include/linux/ftrace.h | 11 -- kernel/trace/trace.h | 4 - kernel/trace/trace_entries.h | 6 +- kernel/trace/trace_functions_graph.c | 145 ++++++++++++--------------- 4 files changed, 69 insertions(+), 97 deletions(-)
From: Donglin Peng <pengdonglin@xiaomi.com>
Currently, the funcgraph-args and funcgraph-retaddr features are mutually exclusive.
This patch resolves this limitation by modifying funcgraph-retaddr to adopt the same
implementation approach as funcgraph-args, specifically by storing the return address
in the first entry of the args array.
As a result, both features now coexist seamlessly and function as intended.
To verify the change, use perf to trace vfs_write with both options enabled:
Before:
# perf ftrace -G vfs_write --graph-opts args,retaddr
......
0) | down_read() { /* <-n_tty_write+0xa3/0x540 */
0) 0.075 us | __cond_resched(); /* <-down_read+0x12/0x160 */
0) 0.079 us | preempt_count_add(); /* <-down_read+0x3b/0x160 */
0) 0.077 us | preempt_count_sub(); /* <-down_read+0x8b/0x160 */
0) 0.754 us | }
After:
# perf ftrace -G vfs_write --graph-opts args,retaddr
......
0) | down_read(sem=0xffff8880100bea78) { /* <-n_tty_write+0xa3/0x540 */
0) 0.075 us | __cond_resched(); /* <-down_read+0x12/0x160 */
0) 0.079 us | preempt_count_add(val=1); /* <-down_read+0x3b/0x160 */
0) 0.077 us | preempt_count_sub(val=1); /* <-down_read+0x8b/0x160 */
0) 0.754 us | }
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Donglin Peng <pengdonglin@xiaomi.com>
---
v3:
- Replace min() with min_t() to improve type safety and maintainability
- Keep only one Signed-off-by for cleaner attribution
- Code refactoring for improved readability
v2:
- Preserve retaddr event functionality (suggested by Steven)
- Store the retaddr in args[0] (suggested by Steven)
- Refactor implementation logic and commit message clarity
---
include/linux/ftrace.h | 11 --
kernel/trace/trace.h | 4 -
kernel/trace/trace_entries.h | 6 +-
kernel/trace/trace_functions_graph.c | 145 ++++++++++++---------------
4 files changed, 69 insertions(+), 97 deletions(-)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 7ded7df6e9b5..88cb54d73bdb 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -1129,17 +1129,6 @@ struct ftrace_graph_ent {
int depth;
} __packed;
-/*
- * Structure that defines an entry function trace with retaddr.
- * It's already packed but the attribute "packed" is needed
- * to remove extra padding at the end.
- */
-struct fgraph_retaddr_ent {
- unsigned long func; /* Current function */
- int depth;
- unsigned long retaddr; /* Return address */
-} __packed;
-
/*
* Structure that defines a return function trace.
* It's already packed but the attribute "packed" is needed
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 85eabb454bee..9fac291b913a 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -955,10 +955,6 @@ extern void graph_trace_close(struct trace_iterator *iter);
extern int __trace_graph_entry(struct trace_array *tr,
struct ftrace_graph_ent *trace,
unsigned int trace_ctx);
-extern int __trace_graph_retaddr_entry(struct trace_array *tr,
- struct ftrace_graph_ent *trace,
- unsigned int trace_ctx,
- unsigned long retaddr);
extern void __trace_graph_return(struct trace_array *tr,
struct ftrace_graph_ret *trace,
unsigned int trace_ctx,
diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
index de294ae2c5c5..593a74663c65 100644
--- a/kernel/trace/trace_entries.h
+++ b/kernel/trace/trace_entries.h
@@ -95,14 +95,14 @@ FTRACE_ENTRY_PACKED(fgraph_retaddr_entry, fgraph_retaddr_ent_entry,
TRACE_GRAPH_RETADDR_ENT,
F_STRUCT(
- __field_struct( struct fgraph_retaddr_ent, graph_ent )
+ __field_struct( struct ftrace_graph_ent, graph_ent )
__field_packed( unsigned long, graph_ent, func )
__field_packed( unsigned int, graph_ent, depth )
- __field_packed( unsigned long, graph_ent, retaddr )
+ __dynamic_array(unsigned long, args )
),
F_printk("--> %ps (%u) <- %ps", (void *)__entry->func, __entry->depth,
- (void *)__entry->retaddr)
+ (void *)__entry->args[0])
);
#else
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index a7f4b9a47a71..f31eeeffbb2d 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -16,6 +16,15 @@
#include "trace.h"
#include "trace_output.h"
+#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
+#define HAVE_RETADDR 1
+#define ARGS_OFFS(args_size) \
+ ((args_size) > FTRACE_REGS_MAX_ARGS * sizeof(long) ? 1 : 0)
+#else
+#define HAVE_RETADDR 0
+#define ARGS_OFFS(args_size) 0
+#endif
+
/* When set, irq functions will be ignored */
static int ftrace_graph_skip_irqs;
@@ -27,21 +36,25 @@ struct fgraph_cpu_data {
unsigned long enter_funcs[FTRACE_RETFUNC_DEPTH];
};
+/*
+ * fgraph_retaddr_ent_entry and ftrace_graph_ent_entry share layout, ent
+ * member repurposed for storage
+ */
struct fgraph_ent_args {
struct ftrace_graph_ent_entry ent;
- /* Force the sizeof of args[] to have FTRACE_REGS_MAX_ARGS entries */
- unsigned long args[FTRACE_REGS_MAX_ARGS];
+ /*
+ * Force the sizeof of args[] to have (FTRACE_REGS_MAX_ARGS + HAVE_RETADDR)
+ * entries with the first entry storing the return address for
+ * TRACE_GRAPH_RETADDR_ENT.
+ */
+ unsigned long args[FTRACE_REGS_MAX_ARGS + HAVE_RETADDR];
};
struct fgraph_data {
struct fgraph_cpu_data __percpu *cpu_data;
/* Place to preserve last processed entry. */
- union {
- struct fgraph_ent_args ent;
- /* TODO allow retaddr to have args */
- struct fgraph_retaddr_ent_entry rent;
- };
+ struct fgraph_ent_args ent;
struct ftrace_graph_ret_entry ret;
int failed;
int cpu;
@@ -127,22 +140,43 @@ static int __graph_entry(struct trace_array *tr, struct ftrace_graph_ent *trace,
struct ring_buffer_event *event;
struct trace_buffer *buffer = tr->array_buffer.buffer;
struct ftrace_graph_ent_entry *entry;
- int size;
+ unsigned long retaddr = 0;
+ int size = sizeof(*entry);
+ int type = TRACE_GRAPH_ENT;
+ bool store_args = false;
+ int nr_args = 0, args_offs = 0;
+
+ if (tracer_flags_is_set(TRACE_GRAPH_PRINT_RETADDR)) {
+ retaddr = ftrace_graph_top_ret_addr(current);
+ type = TRACE_GRAPH_RETADDR_ENT;
+ nr_args += 1;
+ }
/* If fregs is defined, add FTRACE_REGS_MAX_ARGS long size words */
- size = sizeof(*entry) + (FTRACE_REGS_MAX_ARGS * !!fregs * sizeof(long));
+ if (tracer_flags_is_set(TRACE_GRAPH_ARGS)) {
+ store_args = !!fregs;
+ if (store_args)
+ nr_args += FTRACE_REGS_MAX_ARGS;
+ }
- event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_ENT, size, trace_ctx);
+ size += nr_args * sizeof(long);
+ event = trace_buffer_lock_reserve(buffer, type, size, trace_ctx);
if (!event)
return 0;
entry = ring_buffer_event_data(event);
entry->graph_ent = *trace;
+ /* Store the retaddr in args[0] */
+ if (type == TRACE_GRAPH_RETADDR_ENT) {
+ entry->args[0] = retaddr;
+ args_offs += 1;
+ }
+
#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
- if (fregs) {
+ if (store_args) {
for (int i = 0; i < FTRACE_REGS_MAX_ARGS; i++)
- entry->args[i] = ftrace_regs_get_argument(fregs, i);
+ entry->args[i + args_offs] = ftrace_regs_get_argument(fregs, i);
}
#endif
@@ -158,38 +192,6 @@ int __trace_graph_entry(struct trace_array *tr,
return __graph_entry(tr, trace, trace_ctx, NULL);
}
-#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
-int __trace_graph_retaddr_entry(struct trace_array *tr,
- struct ftrace_graph_ent *trace,
- unsigned int trace_ctx,
- unsigned long retaddr)
-{
- struct ring_buffer_event *event;
- struct trace_buffer *buffer = tr->array_buffer.buffer;
- struct fgraph_retaddr_ent_entry *entry;
-
- event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_RETADDR_ENT,
- sizeof(*entry), trace_ctx);
- if (!event)
- return 0;
- entry = ring_buffer_event_data(event);
- entry->graph_ent.func = trace->func;
- entry->graph_ent.depth = trace->depth;
- entry->graph_ent.retaddr = retaddr;
- trace_buffer_unlock_commit_nostack(buffer, event);
-
- return 1;
-}
-#else
-int __trace_graph_retaddr_entry(struct trace_array *tr,
- struct ftrace_graph_ent *trace,
- unsigned int trace_ctx,
- unsigned long retaddr)
-{
- return 1;
-}
-#endif
-
static inline int ftrace_graph_ignore_irqs(void)
{
if (!ftrace_graph_skip_irqs || trace_recursion_test(TRACE_IRQ_BIT))
@@ -211,7 +213,6 @@ static int graph_entry(struct ftrace_graph_ent *trace,
struct trace_array *tr = gops->private;
struct fgraph_times *ftimes;
unsigned int trace_ctx;
- int ret = 0;
if (*task_var & TRACE_GRAPH_NOTRACE)
return 0;
@@ -262,15 +263,7 @@ static int graph_entry(struct ftrace_graph_ent *trace,
return 1;
trace_ctx = tracing_gen_ctx();
- if (IS_ENABLED(CONFIG_FUNCTION_GRAPH_RETADDR) &&
- tracer_flags_is_set(TRACE_GRAPH_PRINT_RETADDR)) {
- unsigned long retaddr = ftrace_graph_top_ret_addr(current);
- ret = __trace_graph_retaddr_entry(tr, trace, trace_ctx, retaddr);
- } else {
- ret = __graph_entry(tr, trace, trace_ctx, fregs);
- }
-
- return ret;
+ return __graph_entry(tr, trace, trace_ctx, fregs);
}
int trace_graph_entry(struct ftrace_graph_ent *trace,
@@ -634,13 +627,9 @@ get_return_for_leaf(struct trace_iterator *iter,
* Save current and next entries for later reference
* if the output fails.
*/
- if (unlikely(curr->ent.type == TRACE_GRAPH_RETADDR_ENT)) {
- data->rent = *(struct fgraph_retaddr_ent_entry *)curr;
- } else {
- int size = min((int)sizeof(data->ent), (int)iter->ent_size);
+ int size = min_t(int, sizeof(data->ent), iter->ent_size);
- memcpy(&data->ent, curr, size);
- }
+ memcpy(&data->ent, curr, size);
/*
* If the next event is not a return type, then
* we only care about what type it is. Otherwise we can
@@ -811,21 +800,21 @@ print_graph_duration(struct trace_array *tr, unsigned long long duration,
#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
#define __TRACE_GRAPH_PRINT_RETADDR TRACE_GRAPH_PRINT_RETADDR
-static void print_graph_retaddr(struct trace_seq *s, struct fgraph_retaddr_ent_entry *entry,
- u32 trace_flags, bool comment)
+static void print_graph_retaddr(struct trace_seq *s, unsigned long retaddr, u32 trace_flags,
+ bool comment)
{
if (comment)
trace_seq_puts(s, " /*");
trace_seq_puts(s, " <-");
- seq_print_ip_sym(s, entry->graph_ent.retaddr, trace_flags | TRACE_ITER_SYM_OFFSET);
+ seq_print_ip_sym(s, retaddr, trace_flags | TRACE_ITER_SYM_OFFSET);
if (comment)
trace_seq_puts(s, " */");
}
#else
#define __TRACE_GRAPH_PRINT_RETADDR 0
-#define print_graph_retaddr(_seq, _entry, _tflags, _comment) do { } while (0)
+#define print_graph_retaddr(_seq, _retaddr, _tflags, _comment) do { } while (0)
#endif
#if defined(CONFIG_FUNCTION_GRAPH_RETVAL) || defined(CONFIG_FUNCTION_GRAPH_RETADDR)
@@ -869,10 +858,12 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
trace_seq_printf(s, "%ps", func);
if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
- print_function_args(s, entry->args, (unsigned long)func);
+ print_function_args(s, entry->args + ARGS_OFFS(args_size),
+ (unsigned long)func);
trace_seq_putc(s, ';');
- } else
+ } else {
trace_seq_puts(s, "();");
+ }
if (print_retval || print_retaddr)
trace_seq_puts(s, " /*");
@@ -882,8 +873,7 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
}
if (print_retaddr)
- print_graph_retaddr(s, (struct fgraph_retaddr_ent_entry *)entry,
- trace_flags, false);
+ print_graph_retaddr(s, entry->args[0], trace_flags, false);
if (print_retval) {
if (hex_format || (err_code == 0))
@@ -964,10 +954,12 @@ print_graph_entry_leaf(struct trace_iterator *iter,
trace_seq_printf(s, "%ps", (void *)ret_func);
if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
- print_function_args(s, entry->args, ret_func);
+ print_function_args(s, entry->args + ARGS_OFFS(args_size),
+ ret_func);
trace_seq_putc(s, ';');
- } else
+ } else {
trace_seq_puts(s, "();");
+ }
}
trace_seq_putc(s, '\n');
@@ -1016,7 +1008,7 @@ print_graph_entry_nested(struct trace_iterator *iter,
args_size = iter->ent_size - offsetof(struct ftrace_graph_ent_entry, args);
if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long))
- print_function_args(s, entry->args, func);
+ print_function_args(s, entry->args + ARGS_OFFS(args_size), func);
else
trace_seq_puts(s, "()");
@@ -1024,8 +1016,7 @@ print_graph_entry_nested(struct trace_iterator *iter,
if (flags & __TRACE_GRAPH_PRINT_RETADDR &&
entry->ent.type == TRACE_GRAPH_RETADDR_ENT)
- print_graph_retaddr(s, (struct fgraph_retaddr_ent_entry *)entry,
- tr->trace_flags, true);
+ print_graph_retaddr(s, entry->args[0], tr->trace_flags, true);
trace_seq_putc(s, '\n');
if (trace_seq_has_overflowed(s))
@@ -1202,7 +1193,7 @@ print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s,
* it can be safely saved at the stack.
*/
struct ftrace_graph_ent_entry *entry;
- u8 save_buf[sizeof(*entry) + FTRACE_REGS_MAX_ARGS * sizeof(long)];
+ u8 save_buf[sizeof(*entry) + (FTRACE_REGS_MAX_ARGS + HAVE_RETADDR) * sizeof(long)];
/* The ent_size is expected to be as big as the entry */
if (iter->ent_size > sizeof(save_buf))
@@ -1429,16 +1420,12 @@ print_graph_function_flags(struct trace_iterator *iter, u32 flags)
trace_assign_type(field, entry);
return print_graph_entry(field, s, iter, flags);
}
-#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
case TRACE_GRAPH_RETADDR_ENT: {
- struct fgraph_retaddr_ent_entry saved;
struct fgraph_retaddr_ent_entry *rfield;
trace_assign_type(rfield, entry);
- saved = *rfield;
- return print_graph_entry((struct ftrace_graph_ent_entry *)&saved, s, iter, flags);
+ return print_graph_entry((typeof(field))rfield, s, iter, flags);
}
-#endif
case TRACE_GRAPH_RET: {
struct ftrace_graph_ret_entry *field;
trace_assign_type(field, entry);
--
2.34.1On Wed, Nov 12, 2025 at 11:46 AM Donglin Peng <dolinux.peng@gmail.com> wrote:
>
> From: Donglin Peng <pengdonglin@xiaomi.com>
>
> Currently, the funcgraph-args and funcgraph-retaddr features are mutually exclusive.
> This patch resolves this limitation by modifying funcgraph-retaddr to adopt the same
> implementation approach as funcgraph-args, specifically by storing the return address
> in the first entry of the args array.
>
> As a result, both features now coexist seamlessly and function as intended.
>
> To verify the change, use perf to trace vfs_write with both options enabled:
>
> Before:
> # perf ftrace -G vfs_write --graph-opts args,retaddr
> ......
> 0) | down_read() { /* <-n_tty_write+0xa3/0x540 */
> 0) 0.075 us | __cond_resched(); /* <-down_read+0x12/0x160 */
> 0) 0.079 us | preempt_count_add(); /* <-down_read+0x3b/0x160 */
> 0) 0.077 us | preempt_count_sub(); /* <-down_read+0x8b/0x160 */
> 0) 0.754 us | }
>
> After:
> # perf ftrace -G vfs_write --graph-opts args,retaddr
> ......
> 0) | down_read(sem=0xffff8880100bea78) { /* <-n_tty_write+0xa3/0x540 */
> 0) 0.075 us | __cond_resched(); /* <-down_read+0x12/0x160 */
> 0) 0.079 us | preempt_count_add(val=1); /* <-down_read+0x3b/0x160 */
> 0) 0.077 us | preempt_count_sub(val=1); /* <-down_read+0x8b/0x160 */
> 0) 0.754 us | }
>
> Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
> Cc: Sven Schnelle <svens@linux.ibm.com>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Signed-off-by: Donglin Peng <pengdonglin@xiaomi.com>
> ---
> v3:
> - Replace min() with min_t() to improve type safety and maintainability
> - Keep only one Signed-off-by for cleaner attribution
> - Code refactoring for improved readability
>
> v2:
> - Preserve retaddr event functionality (suggested by Steven)
> - Store the retaddr in args[0] (suggested by Steven)
> - Refactor implementation logic and commit message clarity
> ---
> include/linux/ftrace.h | 11 --
> kernel/trace/trace.h | 4 -
> kernel/trace/trace_entries.h | 6 +-
> kernel/trace/trace_functions_graph.c | 145 ++++++++++++---------------
> 4 files changed, 69 insertions(+), 97 deletions(-)
>
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index 7ded7df6e9b5..88cb54d73bdb 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -1129,17 +1129,6 @@ struct ftrace_graph_ent {
> int depth;
> } __packed;
>
> -/*
> - * Structure that defines an entry function trace with retaddr.
> - * It's already packed but the attribute "packed" is needed
> - * to remove extra padding at the end.
> - */
> -struct fgraph_retaddr_ent {
> - unsigned long func; /* Current function */
> - int depth;
> - unsigned long retaddr; /* Return address */
> -} __packed;
> -
> /*
> * Structure that defines a return function trace.
> * It's already packed but the attribute "packed" is needed
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 85eabb454bee..9fac291b913a 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -955,10 +955,6 @@ extern void graph_trace_close(struct trace_iterator *iter);
> extern int __trace_graph_entry(struct trace_array *tr,
> struct ftrace_graph_ent *trace,
> unsigned int trace_ctx);
> -extern int __trace_graph_retaddr_entry(struct trace_array *tr,
> - struct ftrace_graph_ent *trace,
> - unsigned int trace_ctx,
> - unsigned long retaddr);
> extern void __trace_graph_return(struct trace_array *tr,
> struct ftrace_graph_ret *trace,
> unsigned int trace_ctx,
> diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
> index de294ae2c5c5..593a74663c65 100644
> --- a/kernel/trace/trace_entries.h
> +++ b/kernel/trace/trace_entries.h
> @@ -95,14 +95,14 @@ FTRACE_ENTRY_PACKED(fgraph_retaddr_entry, fgraph_retaddr_ent_entry,
> TRACE_GRAPH_RETADDR_ENT,
>
> F_STRUCT(
> - __field_struct( struct fgraph_retaddr_ent, graph_ent )
> + __field_struct( struct ftrace_graph_ent, graph_ent )
> __field_packed( unsigned long, graph_ent, func )
> __field_packed( unsigned int, graph_ent, depth )
> - __field_packed( unsigned long, graph_ent, retaddr )
> + __dynamic_array(unsigned long, args )
> ),
>
> F_printk("--> %ps (%u) <- %ps", (void *)__entry->func, __entry->depth,
> - (void *)__entry->retaddr)
> + (void *)__entry->args[0])
> );
>
> #else
> diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> index a7f4b9a47a71..f31eeeffbb2d 100644
> --- a/kernel/trace/trace_functions_graph.c
> +++ b/kernel/trace/trace_functions_graph.c
> @@ -16,6 +16,15 @@
> #include "trace.h"
> #include "trace_output.h"
>
> +#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> +#define HAVE_RETADDR 1
> +#define ARGS_OFFS(args_size) \
> + ((args_size) > FTRACE_REGS_MAX_ARGS * sizeof(long) ? 1 : 0)
> +#else
> +#define HAVE_RETADDR 0
> +#define ARGS_OFFS(args_size) 0
> +#endif
> +
> /* When set, irq functions will be ignored */
> static int ftrace_graph_skip_irqs;
>
> @@ -27,21 +36,25 @@ struct fgraph_cpu_data {
> unsigned long enter_funcs[FTRACE_RETFUNC_DEPTH];
> };
>
> +/*
> + * fgraph_retaddr_ent_entry and ftrace_graph_ent_entry share layout, ent
> + * member repurposed for storage
> + */
> struct fgraph_ent_args {
> struct ftrace_graph_ent_entry ent;
> - /* Force the sizeof of args[] to have FTRACE_REGS_MAX_ARGS entries */
> - unsigned long args[FTRACE_REGS_MAX_ARGS];
> + /*
> + * Force the sizeof of args[] to have (FTRACE_REGS_MAX_ARGS + HAVE_RETADDR)
> + * entries with the first entry storing the return address for
> + * TRACE_GRAPH_RETADDR_ENT.
> + */
> + unsigned long args[FTRACE_REGS_MAX_ARGS + HAVE_RETADDR];
> };
>
> struct fgraph_data {
> struct fgraph_cpu_data __percpu *cpu_data;
>
> /* Place to preserve last processed entry. */
> - union {
> - struct fgraph_ent_args ent;
> - /* TODO allow retaddr to have args */
> - struct fgraph_retaddr_ent_entry rent;
> - };
> + struct fgraph_ent_args ent;
> struct ftrace_graph_ret_entry ret;
> int failed;
> int cpu;
> @@ -127,22 +140,43 @@ static int __graph_entry(struct trace_array *tr, struct ftrace_graph_ent *trace,
> struct ring_buffer_event *event;
> struct trace_buffer *buffer = tr->array_buffer.buffer;
> struct ftrace_graph_ent_entry *entry;
> - int size;
> + unsigned long retaddr = 0;
> + int size = sizeof(*entry);
> + int type = TRACE_GRAPH_ENT;
> + bool store_args = false;
> + int nr_args = 0, args_offs = 0;
> +
> + if (tracer_flags_is_set(TRACE_GRAPH_PRINT_RETADDR)) {
> + retaddr = ftrace_graph_top_ret_addr(current);
> + type = TRACE_GRAPH_RETADDR_ENT;
> + nr_args += 1;
> + }
>
> /* If fregs is defined, add FTRACE_REGS_MAX_ARGS long size words */
> - size = sizeof(*entry) + (FTRACE_REGS_MAX_ARGS * !!fregs * sizeof(long));
> + if (tracer_flags_is_set(TRACE_GRAPH_ARGS)) {
> + store_args = !!fregs;
> + if (store_args)
> + nr_args += FTRACE_REGS_MAX_ARGS;
> + }
>
> - event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_ENT, size, trace_ctx);
> + size += nr_args * sizeof(long);
> + event = trace_buffer_lock_reserve(buffer, type, size, trace_ctx);
> if (!event)
> return 0;
>
> entry = ring_buffer_event_data(event);
> entry->graph_ent = *trace;
>
> + /* Store the retaddr in args[0] */
> + if (type == TRACE_GRAPH_RETADDR_ENT) {
> + entry->args[0] = retaddr;
> + args_offs += 1;
> + }
> +
> #ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
> - if (fregs) {
> + if (store_args) {
> for (int i = 0; i < FTRACE_REGS_MAX_ARGS; i++)
> - entry->args[i] = ftrace_regs_get_argument(fregs, i);
> + entry->args[i + args_offs] = ftrace_regs_get_argument(fregs, i);
> }
> #endif
>
> @@ -158,38 +192,6 @@ int __trace_graph_entry(struct trace_array *tr,
> return __graph_entry(tr, trace, trace_ctx, NULL);
> }
>
> -#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> -int __trace_graph_retaddr_entry(struct trace_array *tr,
> - struct ftrace_graph_ent *trace,
> - unsigned int trace_ctx,
> - unsigned long retaddr)
> -{
> - struct ring_buffer_event *event;
> - struct trace_buffer *buffer = tr->array_buffer.buffer;
> - struct fgraph_retaddr_ent_entry *entry;
> -
> - event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_RETADDR_ENT,
> - sizeof(*entry), trace_ctx);
> - if (!event)
> - return 0;
> - entry = ring_buffer_event_data(event);
> - entry->graph_ent.func = trace->func;
> - entry->graph_ent.depth = trace->depth;
> - entry->graph_ent.retaddr = retaddr;
> - trace_buffer_unlock_commit_nostack(buffer, event);
> -
> - return 1;
> -}
> -#else
> -int __trace_graph_retaddr_entry(struct trace_array *tr,
> - struct ftrace_graph_ent *trace,
> - unsigned int trace_ctx,
> - unsigned long retaddr)
> -{
> - return 1;
> -}
> -#endif
> -
> static inline int ftrace_graph_ignore_irqs(void)
> {
> if (!ftrace_graph_skip_irqs || trace_recursion_test(TRACE_IRQ_BIT))
> @@ -211,7 +213,6 @@ static int graph_entry(struct ftrace_graph_ent *trace,
> struct trace_array *tr = gops->private;
> struct fgraph_times *ftimes;
> unsigned int trace_ctx;
> - int ret = 0;
>
> if (*task_var & TRACE_GRAPH_NOTRACE)
> return 0;
> @@ -262,15 +263,7 @@ static int graph_entry(struct ftrace_graph_ent *trace,
> return 1;
>
> trace_ctx = tracing_gen_ctx();
> - if (IS_ENABLED(CONFIG_FUNCTION_GRAPH_RETADDR) &&
> - tracer_flags_is_set(TRACE_GRAPH_PRINT_RETADDR)) {
> - unsigned long retaddr = ftrace_graph_top_ret_addr(current);
> - ret = __trace_graph_retaddr_entry(tr, trace, trace_ctx, retaddr);
> - } else {
> - ret = __graph_entry(tr, trace, trace_ctx, fregs);
> - }
> -
> - return ret;
> + return __graph_entry(tr, trace, trace_ctx, fregs);
> }
>
> int trace_graph_entry(struct ftrace_graph_ent *trace,
> @@ -634,13 +627,9 @@ get_return_for_leaf(struct trace_iterator *iter,
> * Save current and next entries for later reference
> * if the output fails.
> */
> - if (unlikely(curr->ent.type == TRACE_GRAPH_RETADDR_ENT)) {
> - data->rent = *(struct fgraph_retaddr_ent_entry *)curr;
> - } else {
> - int size = min((int)sizeof(data->ent), (int)iter->ent_size);
> + int size = min_t(int, sizeof(data->ent), iter->ent_size);
>
> - memcpy(&data->ent, curr, size);
> - }
> + memcpy(&data->ent, curr, size);
> /*
> * If the next event is not a return type, then
> * we only care about what type it is. Otherwise we can
> @@ -811,21 +800,21 @@ print_graph_duration(struct trace_array *tr, unsigned long long duration,
>
> #ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> #define __TRACE_GRAPH_PRINT_RETADDR TRACE_GRAPH_PRINT_RETADDR
> -static void print_graph_retaddr(struct trace_seq *s, struct fgraph_retaddr_ent_entry *entry,
> - u32 trace_flags, bool comment)
> +static void print_graph_retaddr(struct trace_seq *s, unsigned long retaddr, u32 trace_flags,
> + bool comment)
> {
> if (comment)
> trace_seq_puts(s, " /*");
>
> trace_seq_puts(s, " <-");
> - seq_print_ip_sym(s, entry->graph_ent.retaddr, trace_flags | TRACE_ITER_SYM_OFFSET);
> + seq_print_ip_sym(s, retaddr, trace_flags | TRACE_ITER_SYM_OFFSET);
>
> if (comment)
> trace_seq_puts(s, " */");
> }
> #else
> #define __TRACE_GRAPH_PRINT_RETADDR 0
> -#define print_graph_retaddr(_seq, _entry, _tflags, _comment) do { } while (0)
> +#define print_graph_retaddr(_seq, _retaddr, _tflags, _comment) do { } while (0)
> #endif
>
> #if defined(CONFIG_FUNCTION_GRAPH_RETVAL) || defined(CONFIG_FUNCTION_GRAPH_RETADDR)
> @@ -869,10 +858,12 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
> trace_seq_printf(s, "%ps", func);
>
> if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
Hi Team,
I have a question regarding the behavior of the funcgraph-args option.
Currently, when the funcgraph-args flag is set, the function arguments
are saved.
However, when the flag is cleared, the trace output still displays the function
arguments unconditionally.
I expected that the flag would control both saving and displaying the arguments.
But it seems that the current design only controls the saving. This
behavior seems
inconsistent.
I think we should add a check for the flag in the display part,
specifically before
calling print_function_args, to ensure that the arguments are only
displayed when
the flag is set.
What are your thoughts?
Thanks,
Donglin
> - print_function_args(s, entry->args, (unsigned long)func);
> + print_function_args(s, entry->args + ARGS_OFFS(args_size),
> + (unsigned long)func);
> trace_seq_putc(s, ';');
> - } else
> + } else {
> trace_seq_puts(s, "();");
> + }
>
> if (print_retval || print_retaddr)
> trace_seq_puts(s, " /*");
> @@ -882,8 +873,7 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
> }
>
> if (print_retaddr)
> - print_graph_retaddr(s, (struct fgraph_retaddr_ent_entry *)entry,
> - trace_flags, false);
> + print_graph_retaddr(s, entry->args[0], trace_flags, false);
>
> if (print_retval) {
> if (hex_format || (err_code == 0))
> @@ -964,10 +954,12 @@ print_graph_entry_leaf(struct trace_iterator *iter,
> trace_seq_printf(s, "%ps", (void *)ret_func);
>
> if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
> - print_function_args(s, entry->args, ret_func);
> + print_function_args(s, entry->args + ARGS_OFFS(args_size),
> + ret_func);
> trace_seq_putc(s, ';');
> - } else
> + } else {
> trace_seq_puts(s, "();");
> + }
> }
> trace_seq_putc(s, '\n');
>
> @@ -1016,7 +1008,7 @@ print_graph_entry_nested(struct trace_iterator *iter,
> args_size = iter->ent_size - offsetof(struct ftrace_graph_ent_entry, args);
>
> if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long))
> - print_function_args(s, entry->args, func);
> + print_function_args(s, entry->args + ARGS_OFFS(args_size), func);
> else
> trace_seq_puts(s, "()");
>
> @@ -1024,8 +1016,7 @@ print_graph_entry_nested(struct trace_iterator *iter,
>
> if (flags & __TRACE_GRAPH_PRINT_RETADDR &&
> entry->ent.type == TRACE_GRAPH_RETADDR_ENT)
> - print_graph_retaddr(s, (struct fgraph_retaddr_ent_entry *)entry,
> - tr->trace_flags, true);
> + print_graph_retaddr(s, entry->args[0], tr->trace_flags, true);
> trace_seq_putc(s, '\n');
>
> if (trace_seq_has_overflowed(s))
> @@ -1202,7 +1193,7 @@ print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s,
> * it can be safely saved at the stack.
> */
> struct ftrace_graph_ent_entry *entry;
> - u8 save_buf[sizeof(*entry) + FTRACE_REGS_MAX_ARGS * sizeof(long)];
> + u8 save_buf[sizeof(*entry) + (FTRACE_REGS_MAX_ARGS + HAVE_RETADDR) * sizeof(long)];
>
> /* The ent_size is expected to be as big as the entry */
> if (iter->ent_size > sizeof(save_buf))
> @@ -1429,16 +1420,12 @@ print_graph_function_flags(struct trace_iterator *iter, u32 flags)
> trace_assign_type(field, entry);
> return print_graph_entry(field, s, iter, flags);
> }
> -#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> case TRACE_GRAPH_RETADDR_ENT: {
> - struct fgraph_retaddr_ent_entry saved;
> struct fgraph_retaddr_ent_entry *rfield;
>
> trace_assign_type(rfield, entry);
> - saved = *rfield;
> - return print_graph_entry((struct ftrace_graph_ent_entry *)&saved, s, iter, flags);
> + return print_graph_entry((typeof(field))rfield, s, iter, flags);
> }
> -#endif
> case TRACE_GRAPH_RET: {
> struct ftrace_graph_ret_entry *field;
> trace_assign_type(field, entry);
> --
> 2.34.1
>
On Wed, 12 Nov 2025 17:00:10 +0800 Donglin Peng <dolinux.peng@gmail.com> wrote: > I have a question regarding the behavior of the funcgraph-args option. > > Currently, when the funcgraph-args flag is set, the function arguments > are saved. > However, when the flag is cleared, the trace output still displays the function > arguments unconditionally. Yes. The flag affects the behavior of the recording and not the displaying of the arguments. There's no reason *not* to show them if they have already been recorded. Recording the arguments causes a noticeable overhead which is why it is optional. > > I expected that the flag would control both saving and displaying the arguments. > But it seems that the current design only controls the saving. This > behavior seems > inconsistent. Not at all. The option is only for the recording. Otherwise, one might expect than they could do the recording and then after the fact enable "func-args" and expect to see them. That would be more inconsistent. > > I think we should add a check for the flag in the display part, > specifically before > calling print_function_args, to ensure that the arguments are only > displayed when > the flag is set. > > What are your thoughts? Big nope! The retaddr is different, as the information is somewhat redundant to the call chain and may cause more noise then needed. -- Steve
On Wed, Nov 12, 2025 at 11:37 PM Steven Rostedt <rostedt@goodmis.org> wrote: > > On Wed, 12 Nov 2025 17:00:10 +0800 > Donglin Peng <dolinux.peng@gmail.com> wrote: > > > I have a question regarding the behavior of the funcgraph-args option. > > > > Currently, when the funcgraph-args flag is set, the function arguments > > are saved. > > However, when the flag is cleared, the trace output still displays the function > > arguments unconditionally. > > Yes. The flag affects the behavior of the recording and not the displaying > of the arguments. There's no reason *not* to show them if they have already > been recorded. Recording the arguments causes a noticeable overhead which > is why it is optional. Thank you for the clarification. I noticed that when funcgraph-args is enabled, it registers trace_graph_entry_args to replace trace_graph_entry. The only difference is whether a valid fregs pointer is passed. To reduce overhead, I propose consolidating the two entry functions. We could maintain only trace_graph_entry and pass the fregs parameter to graph_entry. Within __graph_entry, we can then conditionally record arguments based on 'TRACE_GRAPH_ARGS && !!fregs'. Additionally, I've confirmed that trace_graph_entry is exclusively used by the function_graph tracer. Other tracers like irqsoff and wakeup directly call __trace_graph_entry with a NULL fregs pointer. Therefore, this consolidation would not impact those tracers. What are your thoughts on this approach? Thanks, Donglin > > > > > I expected that the flag would control both saving and displaying the arguments. > > But it seems that the current design only controls the saving. This > > behavior seems > > inconsistent. > > Not at all. The option is only for the recording. Otherwise, one might > expect than they could do the recording and then after the fact enable > "func-args" and expect to see them. That would be more inconsistent. > > > > > I think we should add a check for the flag in the display part, > > specifically before > > calling print_function_args, to ensure that the arguments are only > > displayed when > > the flag is set. > > > > What are your thoughts? > > Big nope! > > The retaddr is different, as the information is somewhat redundant to the > call chain and may cause more noise then needed. > > -- Steve
On Thu, 13 Nov 2025 09:48:52 +0800 Donglin Peng <dolinux.peng@gmail.com> wrote: > I noticed that when funcgraph-args is enabled, it registers > trace_graph_entry_args > to replace trace_graph_entry. The only difference is whether a valid > fregs pointer > is passed. > > To reduce overhead, I propose consolidating the two entry functions. We could > maintain only trace_graph_entry and pass the fregs parameter to graph_entry. > Within __graph_entry, we can then conditionally record arguments based on > 'TRACE_GRAPH_ARGS && !!fregs'. What overhead are you reducing? Why add a branch statement in a critical path? The graph_entry() should not be looking at the flags argument. It's called by *every function*. Also note, I recently fixed the flags to be per instance and not global. Which means testing the flags would require indirection lookups. -- Steve
On Thu, Nov 13, 2025 at 10:02 AM Steven Rostedt <rostedt@goodmis.org> wrote: > > On Thu, 13 Nov 2025 09:48:52 +0800 > Donglin Peng <dolinux.peng@gmail.com> wrote: > > > I noticed that when funcgraph-args is enabled, it registers > > trace_graph_entry_args > > to replace trace_graph_entry. The only difference is whether a valid > > fregs pointer > > is passed. > > > > To reduce overhead, I propose consolidating the two entry functions. We could > > maintain only trace_graph_entry and pass the fregs parameter to graph_entry. > > Within __graph_entry, we can then conditionally record arguments based on > > 'TRACE_GRAPH_ARGS && !!fregs'. > > What overhead are you reducing? Why add a branch statement in a critical path? Thanks. During testing, I found that enabling funcgraph-args incurs significant overhead (344ms) compared to other trace options (near-zero). # time echo 1 > options/funcgraph-retaddr real 0m0.000s user 0m0.000s sys 0m0.000s # time echo 1 > options/funcgraph-args real 0m0.344s user 0m0.000s sys 0m0.344s So I thought it may need to be optimized. > > The graph_entry() should not be looking at the flags argument. It's called > by *every function*. Also note, I recently fixed the flags to be per > instance and not global. Which means testing the flags would require > indirection lookups. Thanks, I agree and it indeed introduces extra branch instruction and may introduce more overhead when using indirection lookups. > > -- Steve
On Thu, Nov 13, 2025 at 10:38 AM Donglin Peng <dolinux.peng@gmail.com> wrote: > > On Thu, Nov 13, 2025 at 10:02 AM Steven Rostedt <rostedt@goodmis.org> wrote: > > > > On Thu, 13 Nov 2025 09:48:52 +0800 > > Donglin Peng <dolinux.peng@gmail.com> wrote: > > > > > I noticed that when funcgraph-args is enabled, it registers > > > trace_graph_entry_args > > > to replace trace_graph_entry. The only difference is whether a valid > > > fregs pointer > > > is passed. > > > > > > To reduce overhead, I propose consolidating the two entry functions. We could > > > maintain only trace_graph_entry and pass the fregs parameter to graph_entry. > > > Within __graph_entry, we can then conditionally record arguments based on > > > 'TRACE_GRAPH_ARGS && !!fregs'. > > > > What overhead are you reducing? Why add a branch statement in a critical path? > > Thanks. During testing, I found that enabling funcgraph-args incurs significant > overhead (344ms) compared to other trace options (near-zero). > > # time echo 1 > options/funcgraph-retaddr > > real 0m0.000s > user 0m0.000s > sys 0m0.000s > > # time echo 1 > options/funcgraph-args > > real 0m0.344s > user 0m0.000s > sys 0m0.344s > > So I thought it may need to be optimized. > > > > > The graph_entry() should not be looking at the flags argument. It's called > > by *every function*. Also note, I recently fixed the flags to be per > > instance and not global. Which means testing the flags would require > > indirection lookups. > > Thanks, I agree and it indeed introduces extra branch instruction and > may introduce more overhead when using indirection lookups. Is it necessary to do the same thing for funcgraph-retaddr considering that it checks the global tracer_flags in the graph_entry? > > > > > -- Steve
On Thu, 13 Nov 2025 11:01:15 +0800 Donglin Peng <dolinux.peng@gmail.com> wrote: > > Thanks, I agree and it indeed introduces extra branch instruction and > > may introduce more overhead when using indirection lookups. > > Is it necessary to do the same thing for funcgraph-retaddr considering > that it checks the global tracer_flags in the graph_entry? Not yet. There's still other flags checked. There's other methods to help with this (at least for some flags). Let's wait on it for now. Thanks, -- Steve
On Wed, Nov 12, 2025 at 11:46 AM Donglin Peng <dolinux.peng@gmail.com> wrote:
>
> From: Donglin Peng <pengdonglin@xiaomi.com>
>
> Currently, the funcgraph-args and funcgraph-retaddr features are mutually exclusive.
> This patch resolves this limitation by modifying funcgraph-retaddr to adopt the same
> implementation approach as funcgraph-args, specifically by storing the return address
> in the first entry of the args array.
>
> As a result, both features now coexist seamlessly and function as intended.
>
> To verify the change, use perf to trace vfs_write with both options enabled:
>
> Before:
> # perf ftrace -G vfs_write --graph-opts args,retaddr
> ......
> 0) | down_read() { /* <-n_tty_write+0xa3/0x540 */
> 0) 0.075 us | __cond_resched(); /* <-down_read+0x12/0x160 */
> 0) 0.079 us | preempt_count_add(); /* <-down_read+0x3b/0x160 */
> 0) 0.077 us | preempt_count_sub(); /* <-down_read+0x8b/0x160 */
> 0) 0.754 us | }
>
> After:
> # perf ftrace -G vfs_write --graph-opts args,retaddr
> ......
> 0) | down_read(sem=0xffff8880100bea78) { /* <-n_tty_write+0xa3/0x540 */
> 0) 0.075 us | __cond_resched(); /* <-down_read+0x12/0x160 */
> 0) 0.079 us | preempt_count_add(val=1); /* <-down_read+0x3b/0x160 */
> 0) 0.077 us | preempt_count_sub(val=1); /* <-down_read+0x8b/0x160 */
> 0) 0.754 us | }
>
> Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
> Cc: Sven Schnelle <svens@linux.ibm.com>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Signed-off-by: Donglin Peng <pengdonglin@xiaomi.com>
> ---
> v3:
> - Replace min() with min_t() to improve type safety and maintainability
> - Keep only one Signed-off-by for cleaner attribution
> - Code refactoring for improved readability
>
> v2:
> - Preserve retaddr event functionality (suggested by Steven)
> - Store the retaddr in args[0] (suggested by Steven)
> - Refactor implementation logic and commit message clarity
> ---
> include/linux/ftrace.h | 11 --
> kernel/trace/trace.h | 4 -
> kernel/trace/trace_entries.h | 6 +-
> kernel/trace/trace_functions_graph.c | 145 ++++++++++++---------------
> 4 files changed, 69 insertions(+), 97 deletions(-)
>
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index 7ded7df6e9b5..88cb54d73bdb 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -1129,17 +1129,6 @@ struct ftrace_graph_ent {
> int depth;
> } __packed;
>
> -/*
> - * Structure that defines an entry function trace with retaddr.
> - * It's already packed but the attribute "packed" is needed
> - * to remove extra padding at the end.
> - */
> -struct fgraph_retaddr_ent {
> - unsigned long func; /* Current function */
> - int depth;
> - unsigned long retaddr; /* Return address */
> -} __packed;
> -
> /*
> * Structure that defines a return function trace.
> * It's already packed but the attribute "packed" is needed
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 85eabb454bee..9fac291b913a 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -955,10 +955,6 @@ extern void graph_trace_close(struct trace_iterator *iter);
> extern int __trace_graph_entry(struct trace_array *tr,
> struct ftrace_graph_ent *trace,
> unsigned int trace_ctx);
> -extern int __trace_graph_retaddr_entry(struct trace_array *tr,
> - struct ftrace_graph_ent *trace,
> - unsigned int trace_ctx,
> - unsigned long retaddr);
> extern void __trace_graph_return(struct trace_array *tr,
> struct ftrace_graph_ret *trace,
> unsigned int trace_ctx,
> diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
> index de294ae2c5c5..593a74663c65 100644
> --- a/kernel/trace/trace_entries.h
> +++ b/kernel/trace/trace_entries.h
> @@ -95,14 +95,14 @@ FTRACE_ENTRY_PACKED(fgraph_retaddr_entry, fgraph_retaddr_ent_entry,
> TRACE_GRAPH_RETADDR_ENT,
>
> F_STRUCT(
> - __field_struct( struct fgraph_retaddr_ent, graph_ent )
> + __field_struct( struct ftrace_graph_ent, graph_ent )
> __field_packed( unsigned long, graph_ent, func )
> __field_packed( unsigned int, graph_ent, depth )
> - __field_packed( unsigned long, graph_ent, retaddr )
> + __dynamic_array(unsigned long, args )
> ),
>
> F_printk("--> %ps (%u) <- %ps", (void *)__entry->func, __entry->depth,
> - (void *)__entry->retaddr)
> + (void *)__entry->args[0])
> );
>
> #else
> diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> index a7f4b9a47a71..f31eeeffbb2d 100644
> --- a/kernel/trace/trace_functions_graph.c
> +++ b/kernel/trace/trace_functions_graph.c
> @@ -16,6 +16,15 @@
> #include "trace.h"
> #include "trace_output.h"
>
> +#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> +#define HAVE_RETADDR 1
> +#define ARGS_OFFS(args_size) \
> + ((args_size) > FTRACE_REGS_MAX_ARGS * sizeof(long) ? 1 : 0)
> +#else
> +#define HAVE_RETADDR 0
> +#define ARGS_OFFS(args_size) 0
> +#endif
> +
> /* When set, irq functions will be ignored */
> static int ftrace_graph_skip_irqs;
>
> @@ -27,21 +36,25 @@ struct fgraph_cpu_data {
> unsigned long enter_funcs[FTRACE_RETFUNC_DEPTH];
> };
>
> +/*
> + * fgraph_retaddr_ent_entry and ftrace_graph_ent_entry share layout, ent
> + * member repurposed for storage
> + */
> struct fgraph_ent_args {
> struct ftrace_graph_ent_entry ent;
> - /* Force the sizeof of args[] to have FTRACE_REGS_MAX_ARGS entries */
> - unsigned long args[FTRACE_REGS_MAX_ARGS];
> + /*
> + * Force the sizeof of args[] to have (FTRACE_REGS_MAX_ARGS + HAVE_RETADDR)
> + * entries with the first entry storing the return address for
> + * TRACE_GRAPH_RETADDR_ENT.
> + */
> + unsigned long args[FTRACE_REGS_MAX_ARGS + HAVE_RETADDR];
> };
>
> struct fgraph_data {
> struct fgraph_cpu_data __percpu *cpu_data;
>
> /* Place to preserve last processed entry. */
> - union {
> - struct fgraph_ent_args ent;
> - /* TODO allow retaddr to have args */
> - struct fgraph_retaddr_ent_entry rent;
> - };
> + struct fgraph_ent_args ent;
> struct ftrace_graph_ret_entry ret;
> int failed;
> int cpu;
> @@ -127,22 +140,43 @@ static int __graph_entry(struct trace_array *tr, struct ftrace_graph_ent *trace,
> struct ring_buffer_event *event;
> struct trace_buffer *buffer = tr->array_buffer.buffer;
> struct ftrace_graph_ent_entry *entry;
> - int size;
> + unsigned long retaddr = 0;
Remove the unnecessary initialization of retaddr. It will be assigned a proper
value before use. Will fix it in the next version.
> + int size = sizeof(*entry);
> + int type = TRACE_GRAPH_ENT;
> + bool store_args = false;
> + int nr_args = 0, args_offs = 0;
> +
> + if (tracer_flags_is_set(TRACE_GRAPH_PRINT_RETADDR)) {
> + retaddr = ftrace_graph_top_ret_addr(current);
> + type = TRACE_GRAPH_RETADDR_ENT;
> + nr_args += 1;
> + }
>
> /* If fregs is defined, add FTRACE_REGS_MAX_ARGS long size words */
> - size = sizeof(*entry) + (FTRACE_REGS_MAX_ARGS * !!fregs * sizeof(long));
> + if (tracer_flags_is_set(TRACE_GRAPH_ARGS)) {
> + store_args = !!fregs;
> + if (store_args)
> + nr_args += FTRACE_REGS_MAX_ARGS;
> + }
>
> - event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_ENT, size, trace_ctx);
> + size += nr_args * sizeof(long);
> + event = trace_buffer_lock_reserve(buffer, type, size, trace_ctx);
> if (!event)
> return 0;
>
> entry = ring_buffer_event_data(event);
> entry->graph_ent = *trace;
>
> + /* Store the retaddr in args[0] */
> + if (type == TRACE_GRAPH_RETADDR_ENT) {
> + entry->args[0] = retaddr;
> + args_offs += 1;
> + }
> +
> #ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
> - if (fregs) {
> + if (store_args) {
> for (int i = 0; i < FTRACE_REGS_MAX_ARGS; i++)
> - entry->args[i] = ftrace_regs_get_argument(fregs, i);
> + entry->args[i + args_offs] = ftrace_regs_get_argument(fregs, i);
> }
> #endif
>
> @@ -158,38 +192,6 @@ int __trace_graph_entry(struct trace_array *tr,
> return __graph_entry(tr, trace, trace_ctx, NULL);
> }
>
> -#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> -int __trace_graph_retaddr_entry(struct trace_array *tr,
> - struct ftrace_graph_ent *trace,
> - unsigned int trace_ctx,
> - unsigned long retaddr)
> -{
> - struct ring_buffer_event *event;
> - struct trace_buffer *buffer = tr->array_buffer.buffer;
> - struct fgraph_retaddr_ent_entry *entry;
> -
> - event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_RETADDR_ENT,
> - sizeof(*entry), trace_ctx);
> - if (!event)
> - return 0;
> - entry = ring_buffer_event_data(event);
> - entry->graph_ent.func = trace->func;
> - entry->graph_ent.depth = trace->depth;
> - entry->graph_ent.retaddr = retaddr;
> - trace_buffer_unlock_commit_nostack(buffer, event);
> -
> - return 1;
> -}
> -#else
> -int __trace_graph_retaddr_entry(struct trace_array *tr,
> - struct ftrace_graph_ent *trace,
> - unsigned int trace_ctx,
> - unsigned long retaddr)
> -{
> - return 1;
> -}
> -#endif
> -
> static inline int ftrace_graph_ignore_irqs(void)
> {
> if (!ftrace_graph_skip_irqs || trace_recursion_test(TRACE_IRQ_BIT))
> @@ -211,7 +213,6 @@ static int graph_entry(struct ftrace_graph_ent *trace,
> struct trace_array *tr = gops->private;
> struct fgraph_times *ftimes;
> unsigned int trace_ctx;
> - int ret = 0;
>
> if (*task_var & TRACE_GRAPH_NOTRACE)
> return 0;
> @@ -262,15 +263,7 @@ static int graph_entry(struct ftrace_graph_ent *trace,
> return 1;
>
> trace_ctx = tracing_gen_ctx();
> - if (IS_ENABLED(CONFIG_FUNCTION_GRAPH_RETADDR) &&
> - tracer_flags_is_set(TRACE_GRAPH_PRINT_RETADDR)) {
> - unsigned long retaddr = ftrace_graph_top_ret_addr(current);
> - ret = __trace_graph_retaddr_entry(tr, trace, trace_ctx, retaddr);
> - } else {
> - ret = __graph_entry(tr, trace, trace_ctx, fregs);
> - }
> -
> - return ret;
> + return __graph_entry(tr, trace, trace_ctx, fregs);
> }
>
> int trace_graph_entry(struct ftrace_graph_ent *trace,
> @@ -634,13 +627,9 @@ get_return_for_leaf(struct trace_iterator *iter,
> * Save current and next entries for later reference
> * if the output fails.
> */
> - if (unlikely(curr->ent.type == TRACE_GRAPH_RETADDR_ENT)) {
> - data->rent = *(struct fgraph_retaddr_ent_entry *)curr;
> - } else {
> - int size = min((int)sizeof(data->ent), (int)iter->ent_size);
> + int size = min_t(int, sizeof(data->ent), iter->ent_size);
>
> - memcpy(&data->ent, curr, size);
> - }
> + memcpy(&data->ent, curr, size);
> /*
> * If the next event is not a return type, then
> * we only care about what type it is. Otherwise we can
> @@ -811,21 +800,21 @@ print_graph_duration(struct trace_array *tr, unsigned long long duration,
>
> #ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> #define __TRACE_GRAPH_PRINT_RETADDR TRACE_GRAPH_PRINT_RETADDR
> -static void print_graph_retaddr(struct trace_seq *s, struct fgraph_retaddr_ent_entry *entry,
> - u32 trace_flags, bool comment)
> +static void print_graph_retaddr(struct trace_seq *s, unsigned long retaddr, u32 trace_flags,
> + bool comment)
> {
> if (comment)
> trace_seq_puts(s, " /*");
>
> trace_seq_puts(s, " <-");
> - seq_print_ip_sym(s, entry->graph_ent.retaddr, trace_flags | TRACE_ITER_SYM_OFFSET);
> + seq_print_ip_sym(s, retaddr, trace_flags | TRACE_ITER_SYM_OFFSET);
>
> if (comment)
> trace_seq_puts(s, " */");
> }
> #else
> #define __TRACE_GRAPH_PRINT_RETADDR 0
> -#define print_graph_retaddr(_seq, _entry, _tflags, _comment) do { } while (0)
> +#define print_graph_retaddr(_seq, _retaddr, _tflags, _comment) do { } while (0)
> #endif
>
> #if defined(CONFIG_FUNCTION_GRAPH_RETVAL) || defined(CONFIG_FUNCTION_GRAPH_RETADDR)
> @@ -869,10 +858,12 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
> trace_seq_printf(s, "%ps", func);
>
> if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
> - print_function_args(s, entry->args, (unsigned long)func);
> + print_function_args(s, entry->args + ARGS_OFFS(args_size),
> + (unsigned long)func);
> trace_seq_putc(s, ';');
> - } else
> + } else {
> trace_seq_puts(s, "();");
> + }
>
> if (print_retval || print_retaddr)
> trace_seq_puts(s, " /*");
> @@ -882,8 +873,7 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
> }
>
> if (print_retaddr)
> - print_graph_retaddr(s, (struct fgraph_retaddr_ent_entry *)entry,
> - trace_flags, false);
> + print_graph_retaddr(s, entry->args[0], trace_flags, false);
>
> if (print_retval) {
> if (hex_format || (err_code == 0))
> @@ -964,10 +954,12 @@ print_graph_entry_leaf(struct trace_iterator *iter,
> trace_seq_printf(s, "%ps", (void *)ret_func);
>
> if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
> - print_function_args(s, entry->args, ret_func);
> + print_function_args(s, entry->args + ARGS_OFFS(args_size),
> + ret_func);
> trace_seq_putc(s, ';');
> - } else
> + } else {
> trace_seq_puts(s, "();");
> + }
> }
> trace_seq_putc(s, '\n');
>
> @@ -1016,7 +1008,7 @@ print_graph_entry_nested(struct trace_iterator *iter,
> args_size = iter->ent_size - offsetof(struct ftrace_graph_ent_entry, args);
>
> if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long))
> - print_function_args(s, entry->args, func);
> + print_function_args(s, entry->args + ARGS_OFFS(args_size), func);
> else
> trace_seq_puts(s, "()");
>
> @@ -1024,8 +1016,7 @@ print_graph_entry_nested(struct trace_iterator *iter,
>
> if (flags & __TRACE_GRAPH_PRINT_RETADDR &&
> entry->ent.type == TRACE_GRAPH_RETADDR_ENT)
> - print_graph_retaddr(s, (struct fgraph_retaddr_ent_entry *)entry,
> - tr->trace_flags, true);
> + print_graph_retaddr(s, entry->args[0], tr->trace_flags, true);
> trace_seq_putc(s, '\n');
>
> if (trace_seq_has_overflowed(s))
> @@ -1202,7 +1193,7 @@ print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s,
> * it can be safely saved at the stack.
> */
> struct ftrace_graph_ent_entry *entry;
> - u8 save_buf[sizeof(*entry) + FTRACE_REGS_MAX_ARGS * sizeof(long)];
> + u8 save_buf[sizeof(*entry) + (FTRACE_REGS_MAX_ARGS + HAVE_RETADDR) * sizeof(long)];
>
> /* The ent_size is expected to be as big as the entry */
> if (iter->ent_size > sizeof(save_buf))
> @@ -1429,16 +1420,12 @@ print_graph_function_flags(struct trace_iterator *iter, u32 flags)
> trace_assign_type(field, entry);
> return print_graph_entry(field, s, iter, flags);
> }
> -#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> case TRACE_GRAPH_RETADDR_ENT: {
> - struct fgraph_retaddr_ent_entry saved;
> struct fgraph_retaddr_ent_entry *rfield;
>
> trace_assign_type(rfield, entry);
> - saved = *rfield;
> - return print_graph_entry((struct ftrace_graph_ent_entry *)&saved, s, iter, flags);
> + return print_graph_entry((typeof(field))rfield, s, iter, flags);
> }
> -#endif
> case TRACE_GRAPH_RET: {
> struct ftrace_graph_ret_entry *field;
> trace_assign_type(field, entry);
> --
> 2.34.1
>
On Wed, 12 Nov 2025 11:43:33 +0800
Donglin Peng <dolinux.peng@gmail.com> wrote:
> From: Donglin Peng <pengdonglin@xiaomi.com>
>
> Currently, the funcgraph-args and funcgraph-retaddr features are mutually exclusive.
> This patch resolves this limitation by modifying funcgraph-retaddr to adopt the same
> implementation approach as funcgraph-args, specifically by storing the return address
> in the first entry of the args array.
>
> As a result, both features now coexist seamlessly and function as intended.
>
> To verify the change, use perf to trace vfs_write with both options enabled:
>
> Before:
> # perf ftrace -G vfs_write --graph-opts args,retaddr
> ......
> 0) | down_read() { /* <-n_tty_write+0xa3/0x540 */
> 0) 0.075 us | __cond_resched(); /* <-down_read+0x12/0x160 */
> 0) 0.079 us | preempt_count_add(); /* <-down_read+0x3b/0x160 */
> 0) 0.077 us | preempt_count_sub(); /* <-down_read+0x8b/0x160 */
> 0) 0.754 us | }
>
> After:
> # perf ftrace -G vfs_write --graph-opts args,retaddr
> ......
> 0) | down_read(sem=0xffff8880100bea78) { /* <-n_tty_write+0xa3/0x540 */
> 0) 0.075 us | __cond_resched(); /* <-down_read+0x12/0x160 */
> 0) 0.079 us | preempt_count_add(val=1); /* <-down_read+0x3b/0x160 */
> 0) 0.077 us | preempt_count_sub(val=1); /* <-down_read+0x8b/0x160 */
> 0) 0.754 us | }
>
> Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
> Cc: Sven Schnelle <svens@linux.ibm.com>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Signed-off-by: Donglin Peng <pengdonglin@xiaomi.com>
Looks good to me except for a few nits, but it's a style issue.
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Thank you,
> ---
> v3:
> - Replace min() with min_t() to improve type safety and maintainability
> - Keep only one Signed-off-by for cleaner attribution
> - Code refactoring for improved readability
>
> v2:
> - Preserve retaddr event functionality (suggested by Steven)
> - Store the retaddr in args[0] (suggested by Steven)
> - Refactor implementation logic and commit message clarity
> ---
> include/linux/ftrace.h | 11 --
> kernel/trace/trace.h | 4 -
> kernel/trace/trace_entries.h | 6 +-
> kernel/trace/trace_functions_graph.c | 145 ++++++++++++---------------
> 4 files changed, 69 insertions(+), 97 deletions(-)
>
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index 7ded7df6e9b5..88cb54d73bdb 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -1129,17 +1129,6 @@ struct ftrace_graph_ent {
> int depth;
> } __packed;
>
> -/*
> - * Structure that defines an entry function trace with retaddr.
> - * It's already packed but the attribute "packed" is needed
> - * to remove extra padding at the end.
> - */
> -struct fgraph_retaddr_ent {
> - unsigned long func; /* Current function */
> - int depth;
> - unsigned long retaddr; /* Return address */
> -} __packed;
> -
> /*
> * Structure that defines a return function trace.
> * It's already packed but the attribute "packed" is needed
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 85eabb454bee..9fac291b913a 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -955,10 +955,6 @@ extern void graph_trace_close(struct trace_iterator *iter);
> extern int __trace_graph_entry(struct trace_array *tr,
> struct ftrace_graph_ent *trace,
> unsigned int trace_ctx);
> -extern int __trace_graph_retaddr_entry(struct trace_array *tr,
> - struct ftrace_graph_ent *trace,
> - unsigned int trace_ctx,
> - unsigned long retaddr);
> extern void __trace_graph_return(struct trace_array *tr,
> struct ftrace_graph_ret *trace,
> unsigned int trace_ctx,
> diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
> index de294ae2c5c5..593a74663c65 100644
> --- a/kernel/trace/trace_entries.h
> +++ b/kernel/trace/trace_entries.h
> @@ -95,14 +95,14 @@ FTRACE_ENTRY_PACKED(fgraph_retaddr_entry, fgraph_retaddr_ent_entry,
> TRACE_GRAPH_RETADDR_ENT,
>
> F_STRUCT(
> - __field_struct( struct fgraph_retaddr_ent, graph_ent )
> + __field_struct( struct ftrace_graph_ent, graph_ent )
> __field_packed( unsigned long, graph_ent, func )
> __field_packed( unsigned int, graph_ent, depth )
> - __field_packed( unsigned long, graph_ent, retaddr )
> + __dynamic_array(unsigned long, args )
> ),
>
> F_printk("--> %ps (%u) <- %ps", (void *)__entry->func, __entry->depth,
> - (void *)__entry->retaddr)
> + (void *)__entry->args[0])
> );
>
> #else
> diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> index a7f4b9a47a71..f31eeeffbb2d 100644
> --- a/kernel/trace/trace_functions_graph.c
> +++ b/kernel/trace/trace_functions_graph.c
> @@ -16,6 +16,15 @@
> #include "trace.h"
> #include "trace_output.h"
>
> +#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> +#define HAVE_RETADDR 1
> +#define ARGS_OFFS(args_size) \
> + ((args_size) > FTRACE_REGS_MAX_ARGS * sizeof(long) ? 1 : 0)
> +#else
> +#define HAVE_RETADDR 0
> +#define ARGS_OFFS(args_size) 0
> +#endif
> +
> /* When set, irq functions will be ignored */
> static int ftrace_graph_skip_irqs;
>
> @@ -27,21 +36,25 @@ struct fgraph_cpu_data {
> unsigned long enter_funcs[FTRACE_RETFUNC_DEPTH];
> };
>
> +/*
> + * fgraph_retaddr_ent_entry and ftrace_graph_ent_entry share layout, ent
> + * member repurposed for storage
> + */
> struct fgraph_ent_args {
> struct ftrace_graph_ent_entry ent;
> - /* Force the sizeof of args[] to have FTRACE_REGS_MAX_ARGS entries */
> - unsigned long args[FTRACE_REGS_MAX_ARGS];
> + /*
> + * Force the sizeof of args[] to have (FTRACE_REGS_MAX_ARGS + HAVE_RETADDR)
> + * entries with the first entry storing the return address for
> + * TRACE_GRAPH_RETADDR_ENT.
> + */
> + unsigned long args[FTRACE_REGS_MAX_ARGS + HAVE_RETADDR];
> };
>
> struct fgraph_data {
> struct fgraph_cpu_data __percpu *cpu_data;
>
> /* Place to preserve last processed entry. */
> - union {
> - struct fgraph_ent_args ent;
> - /* TODO allow retaddr to have args */
> - struct fgraph_retaddr_ent_entry rent;
> - };
> + struct fgraph_ent_args ent;
> struct ftrace_graph_ret_entry ret;
> int failed;
> int cpu;
> @@ -127,22 +140,43 @@ static int __graph_entry(struct trace_array *tr, struct ftrace_graph_ent *trace,
> struct ring_buffer_event *event;
> struct trace_buffer *buffer = tr->array_buffer.buffer;
> struct ftrace_graph_ent_entry *entry;
> - int size;
> + unsigned long retaddr = 0;
> + int size = sizeof(*entry);
> + int type = TRACE_GRAPH_ENT;
> + bool store_args = false;
> + int nr_args = 0, args_offs = 0;
> +
> + if (tracer_flags_is_set(TRACE_GRAPH_PRINT_RETADDR)) {
> + retaddr = ftrace_graph_top_ret_addr(current);
> + type = TRACE_GRAPH_RETADDR_ENT;
> + nr_args += 1;
> + }
>
> /* If fregs is defined, add FTRACE_REGS_MAX_ARGS long size words */
> - size = sizeof(*entry) + (FTRACE_REGS_MAX_ARGS * !!fregs * sizeof(long));
> + if (tracer_flags_is_set(TRACE_GRAPH_ARGS)) {
> + store_args = !!fregs;
> + if (store_args)
> + nr_args += FTRACE_REGS_MAX_ARGS;
> + }
>
> - event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_ENT, size, trace_ctx);
> + size += nr_args * sizeof(long);
> + event = trace_buffer_lock_reserve(buffer, type, size, trace_ctx);
> if (!event)
> return 0;
>
> entry = ring_buffer_event_data(event);
> entry->graph_ent = *trace;
>
> + /* Store the retaddr in args[0] */
> + if (type == TRACE_GRAPH_RETADDR_ENT) {
> + entry->args[0] = retaddr;
> + args_offs += 1;
> + }
> +
> #ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
> - if (fregs) {
> + if (store_args) {
> for (int i = 0; i < FTRACE_REGS_MAX_ARGS; i++)
> - entry->args[i] = ftrace_regs_get_argument(fregs, i);
> + entry->args[i + args_offs] = ftrace_regs_get_argument(fregs, i);
> }
> #endif
>
> @@ -158,38 +192,6 @@ int __trace_graph_entry(struct trace_array *tr,
> return __graph_entry(tr, trace, trace_ctx, NULL);
> }
>
> -#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> -int __trace_graph_retaddr_entry(struct trace_array *tr,
> - struct ftrace_graph_ent *trace,
> - unsigned int trace_ctx,
> - unsigned long retaddr)
> -{
> - struct ring_buffer_event *event;
> - struct trace_buffer *buffer = tr->array_buffer.buffer;
> - struct fgraph_retaddr_ent_entry *entry;
> -
> - event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_RETADDR_ENT,
> - sizeof(*entry), trace_ctx);
> - if (!event)
> - return 0;
> - entry = ring_buffer_event_data(event);
> - entry->graph_ent.func = trace->func;
> - entry->graph_ent.depth = trace->depth;
> - entry->graph_ent.retaddr = retaddr;
> - trace_buffer_unlock_commit_nostack(buffer, event);
> -
> - return 1;
> -}
> -#else
> -int __trace_graph_retaddr_entry(struct trace_array *tr,
> - struct ftrace_graph_ent *trace,
> - unsigned int trace_ctx,
> - unsigned long retaddr)
> -{
> - return 1;
> -}
> -#endif
> -
> static inline int ftrace_graph_ignore_irqs(void)
> {
> if (!ftrace_graph_skip_irqs || trace_recursion_test(TRACE_IRQ_BIT))
> @@ -211,7 +213,6 @@ static int graph_entry(struct ftrace_graph_ent *trace,
> struct trace_array *tr = gops->private;
> struct fgraph_times *ftimes;
> unsigned int trace_ctx;
> - int ret = 0;
>
> if (*task_var & TRACE_GRAPH_NOTRACE)
> return 0;
> @@ -262,15 +263,7 @@ static int graph_entry(struct ftrace_graph_ent *trace,
> return 1;
>
> trace_ctx = tracing_gen_ctx();
> - if (IS_ENABLED(CONFIG_FUNCTION_GRAPH_RETADDR) &&
> - tracer_flags_is_set(TRACE_GRAPH_PRINT_RETADDR)) {
> - unsigned long retaddr = ftrace_graph_top_ret_addr(current);
> - ret = __trace_graph_retaddr_entry(tr, trace, trace_ctx, retaddr);
> - } else {
> - ret = __graph_entry(tr, trace, trace_ctx, fregs);
> - }
> -
> - return ret;
> + return __graph_entry(tr, trace, trace_ctx, fregs);
> }
>
> int trace_graph_entry(struct ftrace_graph_ent *trace,
> @@ -634,13 +627,9 @@ get_return_for_leaf(struct trace_iterator *iter,
> * Save current and next entries for later reference
> * if the output fails.
> */
> - if (unlikely(curr->ent.type == TRACE_GRAPH_RETADDR_ENT)) {
> - data->rent = *(struct fgraph_retaddr_ent_entry *)curr;
> - } else {
> - int size = min((int)sizeof(data->ent), (int)iter->ent_size);
> + int size = min_t(int, sizeof(data->ent), iter->ent_size);
>
> - memcpy(&data->ent, curr, size);
> - }
> + memcpy(&data->ent, curr, size);
> /*
> * If the next event is not a return type, then
> * we only care about what type it is. Otherwise we can
> @@ -811,21 +800,21 @@ print_graph_duration(struct trace_array *tr, unsigned long long duration,
>
> #ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> #define __TRACE_GRAPH_PRINT_RETADDR TRACE_GRAPH_PRINT_RETADDR
> -static void print_graph_retaddr(struct trace_seq *s, struct fgraph_retaddr_ent_entry *entry,
> - u32 trace_flags, bool comment)
> +static void print_graph_retaddr(struct trace_seq *s, unsigned long retaddr, u32 trace_flags,
> + bool comment)
> {
> if (comment)
> trace_seq_puts(s, " /*");
>
> trace_seq_puts(s, " <-");
> - seq_print_ip_sym(s, entry->graph_ent.retaddr, trace_flags | TRACE_ITER_SYM_OFFSET);
> + seq_print_ip_sym(s, retaddr, trace_flags | TRACE_ITER_SYM_OFFSET);
>
> if (comment)
> trace_seq_puts(s, " */");
> }
> #else
> #define __TRACE_GRAPH_PRINT_RETADDR 0
> -#define print_graph_retaddr(_seq, _entry, _tflags, _comment) do { } while (0)
> +#define print_graph_retaddr(_seq, _retaddr, _tflags, _comment) do { } while (0)
> #endif
>
> #if defined(CONFIG_FUNCTION_GRAPH_RETVAL) || defined(CONFIG_FUNCTION_GRAPH_RETADDR)
> @@ -869,10 +858,12 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
> trace_seq_printf(s, "%ps", func);
>
> if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
> - print_function_args(s, entry->args, (unsigned long)func);
> + print_function_args(s, entry->args + ARGS_OFFS(args_size),
> + (unsigned long)func);
> trace_seq_putc(s, ';');
> - } else
> + } else {
nit: you don't need to add braces for a single line block.
> trace_seq_puts(s, "();");
> + }
>
> if (print_retval || print_retaddr)
> trace_seq_puts(s, " /*");
> @@ -882,8 +873,7 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
> }
>
> if (print_retaddr)
> - print_graph_retaddr(s, (struct fgraph_retaddr_ent_entry *)entry,
> - trace_flags, false);
> + print_graph_retaddr(s, entry->args[0], trace_flags, false);
>
> if (print_retval) {
> if (hex_format || (err_code == 0))
> @@ -964,10 +954,12 @@ print_graph_entry_leaf(struct trace_iterator *iter,
> trace_seq_printf(s, "%ps", (void *)ret_func);
>
> if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
> - print_function_args(s, entry->args, ret_func);
> + print_function_args(s, entry->args + ARGS_OFFS(args_size),
> + ret_func);
> trace_seq_putc(s, ';');
> - } else
> + } else {
Ditto.
> trace_seq_puts(s, "();");
> + }
> }
> trace_seq_putc(s, '\n');
>
> @@ -1016,7 +1008,7 @@ print_graph_entry_nested(struct trace_iterator *iter,
> args_size = iter->ent_size - offsetof(struct ftrace_graph_ent_entry, args);
>
> if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long))
> - print_function_args(s, entry->args, func);
> + print_function_args(s, entry->args + ARGS_OFFS(args_size), func);
> else
> trace_seq_puts(s, "()");
>
> @@ -1024,8 +1016,7 @@ print_graph_entry_nested(struct trace_iterator *iter,
>
> if (flags & __TRACE_GRAPH_PRINT_RETADDR &&
> entry->ent.type == TRACE_GRAPH_RETADDR_ENT)
> - print_graph_retaddr(s, (struct fgraph_retaddr_ent_entry *)entry,
> - tr->trace_flags, true);
> + print_graph_retaddr(s, entry->args[0], tr->trace_flags, true);
> trace_seq_putc(s, '\n');
>
> if (trace_seq_has_overflowed(s))
> @@ -1202,7 +1193,7 @@ print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s,
> * it can be safely saved at the stack.
> */
> struct ftrace_graph_ent_entry *entry;
> - u8 save_buf[sizeof(*entry) + FTRACE_REGS_MAX_ARGS * sizeof(long)];
> + u8 save_buf[sizeof(*entry) + (FTRACE_REGS_MAX_ARGS + HAVE_RETADDR) * sizeof(long)];
>
> /* The ent_size is expected to be as big as the entry */
> if (iter->ent_size > sizeof(save_buf))
> @@ -1429,16 +1420,12 @@ print_graph_function_flags(struct trace_iterator *iter, u32 flags)
> trace_assign_type(field, entry);
> return print_graph_entry(field, s, iter, flags);
> }
> -#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> case TRACE_GRAPH_RETADDR_ENT: {
> - struct fgraph_retaddr_ent_entry saved;
> struct fgraph_retaddr_ent_entry *rfield;
>
> trace_assign_type(rfield, entry);
> - saved = *rfield;
> - return print_graph_entry((struct ftrace_graph_ent_entry *)&saved, s, iter, flags);
> + return print_graph_entry((typeof(field))rfield, s, iter, flags);
> }
> -#endif
> case TRACE_GRAPH_RET: {
> struct ftrace_graph_ret_entry *field;
> trace_assign_type(field, entry);
> --
> 2.34.1
>
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
On Wed, 12 Nov 2025 14:17:05 +0900
Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:
> > #if defined(CONFIG_FUNCTION_GRAPH_RETVAL) || defined(CONFIG_FUNCTION_GRAPH_RETADDR)
> > @@ -869,10 +858,12 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
> > trace_seq_printf(s, "%ps", func);
> >
> > if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
> > - print_function_args(s, entry->args, (unsigned long)func);
> > + print_function_args(s, entry->args + ARGS_OFFS(args_size),
> > + (unsigned long)func);
> > trace_seq_putc(s, ';');
> > - } else
> > + } else {
>
> nit: you don't need to add braces for a single line block.
>
> > trace_seq_puts(s, "();");
> > + }
> >
Actually you do.
The rule for if/else is if one side requires { }, then both do.
https://docs.kernel.org/process/coding-style.html#placing-braces-and-spaces
Yes, this has been inconsistent and my older code breaks this rule, but I
try to follow it in newer code.
-- Steve
On Wed, Nov 12, 2025 at 1:17 PM Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> On Wed, 12 Nov 2025 11:43:33 +0800
> Donglin Peng <dolinux.peng@gmail.com> wrote:
>
> > From: Donglin Peng <pengdonglin@xiaomi.com>
> >
> > Currently, the funcgraph-args and funcgraph-retaddr features are mutually exclusive.
> > This patch resolves this limitation by modifying funcgraph-retaddr to adopt the same
> > implementation approach as funcgraph-args, specifically by storing the return address
> > in the first entry of the args array.
> >
> > As a result, both features now coexist seamlessly and function as intended.
> >
> > To verify the change, use perf to trace vfs_write with both options enabled:
> >
> > Before:
> > # perf ftrace -G vfs_write --graph-opts args,retaddr
> > ......
> > 0) | down_read() { /* <-n_tty_write+0xa3/0x540 */
> > 0) 0.075 us | __cond_resched(); /* <-down_read+0x12/0x160 */
> > 0) 0.079 us | preempt_count_add(); /* <-down_read+0x3b/0x160 */
> > 0) 0.077 us | preempt_count_sub(); /* <-down_read+0x8b/0x160 */
> > 0) 0.754 us | }
> >
> > After:
> > # perf ftrace -G vfs_write --graph-opts args,retaddr
> > ......
> > 0) | down_read(sem=0xffff8880100bea78) { /* <-n_tty_write+0xa3/0x540 */
> > 0) 0.075 us | __cond_resched(); /* <-down_read+0x12/0x160 */
> > 0) 0.079 us | preempt_count_add(val=1); /* <-down_read+0x3b/0x160 */
> > 0) 0.077 us | preempt_count_sub(val=1); /* <-down_read+0x8b/0x160 */
> > 0) 0.754 us | }
> >
> > Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
> > Cc: Sven Schnelle <svens@linux.ibm.com>
> > Cc: Masami Hiramatsu <mhiramat@kernel.org>
> > Signed-off-by: Donglin Peng <pengdonglin@xiaomi.com>
>
> Looks good to me except for a few nits, but it's a style issue.
>
> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Thank you for ack.
>
> Thank you,
>
> > ---
> > v3:
> > - Replace min() with min_t() to improve type safety and maintainability
> > - Keep only one Signed-off-by for cleaner attribution
> > - Code refactoring for improved readability
> >
> > v2:
> > - Preserve retaddr event functionality (suggested by Steven)
> > - Store the retaddr in args[0] (suggested by Steven)
> > - Refactor implementation logic and commit message clarity
> > ---
> > include/linux/ftrace.h | 11 --
> > kernel/trace/trace.h | 4 -
> > kernel/trace/trace_entries.h | 6 +-
> > kernel/trace/trace_functions_graph.c | 145 ++++++++++++---------------
> > 4 files changed, 69 insertions(+), 97 deletions(-)
> >
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > index 7ded7df6e9b5..88cb54d73bdb 100644
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -1129,17 +1129,6 @@ struct ftrace_graph_ent {
> > int depth;
> > } __packed;
> >
> > -/*
> > - * Structure that defines an entry function trace with retaddr.
> > - * It's already packed but the attribute "packed" is needed
> > - * to remove extra padding at the end.
> > - */
> > -struct fgraph_retaddr_ent {
> > - unsigned long func; /* Current function */
> > - int depth;
> > - unsigned long retaddr; /* Return address */
> > -} __packed;
> > -
> > /*
> > * Structure that defines a return function trace.
> > * It's already packed but the attribute "packed" is needed
> > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> > index 85eabb454bee..9fac291b913a 100644
> > --- a/kernel/trace/trace.h
> > +++ b/kernel/trace/trace.h
> > @@ -955,10 +955,6 @@ extern void graph_trace_close(struct trace_iterator *iter);
> > extern int __trace_graph_entry(struct trace_array *tr,
> > struct ftrace_graph_ent *trace,
> > unsigned int trace_ctx);
> > -extern int __trace_graph_retaddr_entry(struct trace_array *tr,
> > - struct ftrace_graph_ent *trace,
> > - unsigned int trace_ctx,
> > - unsigned long retaddr);
> > extern void __trace_graph_return(struct trace_array *tr,
> > struct ftrace_graph_ret *trace,
> > unsigned int trace_ctx,
> > diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
> > index de294ae2c5c5..593a74663c65 100644
> > --- a/kernel/trace/trace_entries.h
> > +++ b/kernel/trace/trace_entries.h
> > @@ -95,14 +95,14 @@ FTRACE_ENTRY_PACKED(fgraph_retaddr_entry, fgraph_retaddr_ent_entry,
> > TRACE_GRAPH_RETADDR_ENT,
> >
> > F_STRUCT(
> > - __field_struct( struct fgraph_retaddr_ent, graph_ent )
> > + __field_struct( struct ftrace_graph_ent, graph_ent )
> > __field_packed( unsigned long, graph_ent, func )
> > __field_packed( unsigned int, graph_ent, depth )
> > - __field_packed( unsigned long, graph_ent, retaddr )
> > + __dynamic_array(unsigned long, args )
> > ),
> >
> > F_printk("--> %ps (%u) <- %ps", (void *)__entry->func, __entry->depth,
> > - (void *)__entry->retaddr)
> > + (void *)__entry->args[0])
> > );
> >
> > #else
> > diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> > index a7f4b9a47a71..f31eeeffbb2d 100644
> > --- a/kernel/trace/trace_functions_graph.c
> > +++ b/kernel/trace/trace_functions_graph.c
> > @@ -16,6 +16,15 @@
> > #include "trace.h"
> > #include "trace_output.h"
> >
> > +#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> > +#define HAVE_RETADDR 1
> > +#define ARGS_OFFS(args_size) \
> > + ((args_size) > FTRACE_REGS_MAX_ARGS * sizeof(long) ? 1 : 0)
> > +#else
> > +#define HAVE_RETADDR 0
> > +#define ARGS_OFFS(args_size) 0
> > +#endif
> > +
> > /* When set, irq functions will be ignored */
> > static int ftrace_graph_skip_irqs;
> >
> > @@ -27,21 +36,25 @@ struct fgraph_cpu_data {
> > unsigned long enter_funcs[FTRACE_RETFUNC_DEPTH];
> > };
> >
> > +/*
> > + * fgraph_retaddr_ent_entry and ftrace_graph_ent_entry share layout, ent
> > + * member repurposed for storage
> > + */
> > struct fgraph_ent_args {
> > struct ftrace_graph_ent_entry ent;
> > - /* Force the sizeof of args[] to have FTRACE_REGS_MAX_ARGS entries */
> > - unsigned long args[FTRACE_REGS_MAX_ARGS];
> > + /*
> > + * Force the sizeof of args[] to have (FTRACE_REGS_MAX_ARGS + HAVE_RETADDR)
> > + * entries with the first entry storing the return address for
> > + * TRACE_GRAPH_RETADDR_ENT.
> > + */
> > + unsigned long args[FTRACE_REGS_MAX_ARGS + HAVE_RETADDR];
> > };
> >
> > struct fgraph_data {
> > struct fgraph_cpu_data __percpu *cpu_data;
> >
> > /* Place to preserve last processed entry. */
> > - union {
> > - struct fgraph_ent_args ent;
> > - /* TODO allow retaddr to have args */
> > - struct fgraph_retaddr_ent_entry rent;
> > - };
> > + struct fgraph_ent_args ent;
> > struct ftrace_graph_ret_entry ret;
> > int failed;
> > int cpu;
> > @@ -127,22 +140,43 @@ static int __graph_entry(struct trace_array *tr, struct ftrace_graph_ent *trace,
> > struct ring_buffer_event *event;
> > struct trace_buffer *buffer = tr->array_buffer.buffer;
> > struct ftrace_graph_ent_entry *entry;
> > - int size;
> > + unsigned long retaddr = 0;
> > + int size = sizeof(*entry);
> > + int type = TRACE_GRAPH_ENT;
> > + bool store_args = false;
> > + int nr_args = 0, args_offs = 0;
> > +
> > + if (tracer_flags_is_set(TRACE_GRAPH_PRINT_RETADDR)) {
> > + retaddr = ftrace_graph_top_ret_addr(current);
> > + type = TRACE_GRAPH_RETADDR_ENT;
> > + nr_args += 1;
> > + }
> >
> > /* If fregs is defined, add FTRACE_REGS_MAX_ARGS long size words */
> > - size = sizeof(*entry) + (FTRACE_REGS_MAX_ARGS * !!fregs * sizeof(long));
> > + if (tracer_flags_is_set(TRACE_GRAPH_ARGS)) {
> > + store_args = !!fregs;
> > + if (store_args)
> > + nr_args += FTRACE_REGS_MAX_ARGS;
> > + }
> >
> > - event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_ENT, size, trace_ctx);
> > + size += nr_args * sizeof(long);
> > + event = trace_buffer_lock_reserve(buffer, type, size, trace_ctx);
> > if (!event)
> > return 0;
> >
> > entry = ring_buffer_event_data(event);
> > entry->graph_ent = *trace;
> >
> > + /* Store the retaddr in args[0] */
> > + if (type == TRACE_GRAPH_RETADDR_ENT) {
> > + entry->args[0] = retaddr;
> > + args_offs += 1;
> > + }
> > +
> > #ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
> > - if (fregs) {
> > + if (store_args) {
> > for (int i = 0; i < FTRACE_REGS_MAX_ARGS; i++)
> > - entry->args[i] = ftrace_regs_get_argument(fregs, i);
> > + entry->args[i + args_offs] = ftrace_regs_get_argument(fregs, i);
> > }
> > #endif
> >
> > @@ -158,38 +192,6 @@ int __trace_graph_entry(struct trace_array *tr,
> > return __graph_entry(tr, trace, trace_ctx, NULL);
> > }
> >
> > -#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> > -int __trace_graph_retaddr_entry(struct trace_array *tr,
> > - struct ftrace_graph_ent *trace,
> > - unsigned int trace_ctx,
> > - unsigned long retaddr)
> > -{
> > - struct ring_buffer_event *event;
> > - struct trace_buffer *buffer = tr->array_buffer.buffer;
> > - struct fgraph_retaddr_ent_entry *entry;
> > -
> > - event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_RETADDR_ENT,
> > - sizeof(*entry), trace_ctx);
> > - if (!event)
> > - return 0;
> > - entry = ring_buffer_event_data(event);
> > - entry->graph_ent.func = trace->func;
> > - entry->graph_ent.depth = trace->depth;
> > - entry->graph_ent.retaddr = retaddr;
> > - trace_buffer_unlock_commit_nostack(buffer, event);
> > -
> > - return 1;
> > -}
> > -#else
> > -int __trace_graph_retaddr_entry(struct trace_array *tr,
> > - struct ftrace_graph_ent *trace,
> > - unsigned int trace_ctx,
> > - unsigned long retaddr)
> > -{
> > - return 1;
> > -}
> > -#endif
> > -
> > static inline int ftrace_graph_ignore_irqs(void)
> > {
> > if (!ftrace_graph_skip_irqs || trace_recursion_test(TRACE_IRQ_BIT))
> > @@ -211,7 +213,6 @@ static int graph_entry(struct ftrace_graph_ent *trace,
> > struct trace_array *tr = gops->private;
> > struct fgraph_times *ftimes;
> > unsigned int trace_ctx;
> > - int ret = 0;
> >
> > if (*task_var & TRACE_GRAPH_NOTRACE)
> > return 0;
> > @@ -262,15 +263,7 @@ static int graph_entry(struct ftrace_graph_ent *trace,
> > return 1;
> >
> > trace_ctx = tracing_gen_ctx();
> > - if (IS_ENABLED(CONFIG_FUNCTION_GRAPH_RETADDR) &&
> > - tracer_flags_is_set(TRACE_GRAPH_PRINT_RETADDR)) {
> > - unsigned long retaddr = ftrace_graph_top_ret_addr(current);
> > - ret = __trace_graph_retaddr_entry(tr, trace, trace_ctx, retaddr);
> > - } else {
> > - ret = __graph_entry(tr, trace, trace_ctx, fregs);
> > - }
> > -
> > - return ret;
> > + return __graph_entry(tr, trace, trace_ctx, fregs);
> > }
> >
> > int trace_graph_entry(struct ftrace_graph_ent *trace,
> > @@ -634,13 +627,9 @@ get_return_for_leaf(struct trace_iterator *iter,
> > * Save current and next entries for later reference
> > * if the output fails.
> > */
> > - if (unlikely(curr->ent.type == TRACE_GRAPH_RETADDR_ENT)) {
> > - data->rent = *(struct fgraph_retaddr_ent_entry *)curr;
> > - } else {
> > - int size = min((int)sizeof(data->ent), (int)iter->ent_size);
> > + int size = min_t(int, sizeof(data->ent), iter->ent_size);
> >
> > - memcpy(&data->ent, curr, size);
> > - }
> > + memcpy(&data->ent, curr, size);
> > /*
> > * If the next event is not a return type, then
> > * we only care about what type it is. Otherwise we can
> > @@ -811,21 +800,21 @@ print_graph_duration(struct trace_array *tr, unsigned long long duration,
> >
> > #ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> > #define __TRACE_GRAPH_PRINT_RETADDR TRACE_GRAPH_PRINT_RETADDR
> > -static void print_graph_retaddr(struct trace_seq *s, struct fgraph_retaddr_ent_entry *entry,
> > - u32 trace_flags, bool comment)
> > +static void print_graph_retaddr(struct trace_seq *s, unsigned long retaddr, u32 trace_flags,
> > + bool comment)
> > {
> > if (comment)
> > trace_seq_puts(s, " /*");
> >
> > trace_seq_puts(s, " <-");
> > - seq_print_ip_sym(s, entry->graph_ent.retaddr, trace_flags | TRACE_ITER_SYM_OFFSET);
> > + seq_print_ip_sym(s, retaddr, trace_flags | TRACE_ITER_SYM_OFFSET);
> >
> > if (comment)
> > trace_seq_puts(s, " */");
> > }
> > #else
> > #define __TRACE_GRAPH_PRINT_RETADDR 0
> > -#define print_graph_retaddr(_seq, _entry, _tflags, _comment) do { } while (0)
> > +#define print_graph_retaddr(_seq, _retaddr, _tflags, _comment) do { } while (0)
> > #endif
> >
> > #if defined(CONFIG_FUNCTION_GRAPH_RETVAL) || defined(CONFIG_FUNCTION_GRAPH_RETADDR)
> > @@ -869,10 +858,12 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
> > trace_seq_printf(s, "%ps", func);
> >
> > if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
> > - print_function_args(s, entry->args, (unsigned long)func);
> > + print_function_args(s, entry->args + ARGS_OFFS(args_size),
> > + (unsigned long)func);
> > trace_seq_putc(s, ';');
> > - } else
> > + } else {
>
> nit: you don't need to add braces for a single line block.
Thanks. I added the else braces for consistency with the
multi-statement if branch,
per coding-style.rst. Happy to remove if you prefer the
single-statement exception.
https://elixir.bootlin.com/linux/v6.18-rc5/source/Documentation/process/coding-style.rst#L213
Do not unnecessarily use braces where a single statement will do.
.. code-block:: c
if (condition)
action();
and
.. code-block:: c
if (condition)
do_this();
else
do_that();
This does not apply if only one branch of a conditional statement is a single
statement; in the latter case use braces in both branches:
.. code-block:: c
if (condition) {
do_this();
do_that();
} else {
otherwise();
}
>
> > trace_seq_puts(s, "();");
> > + }
> >
> > if (print_retval || print_retaddr)
> > trace_seq_puts(s, " /*");
> > @@ -882,8 +873,7 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
> > }
> >
> > if (print_retaddr)
> > - print_graph_retaddr(s, (struct fgraph_retaddr_ent_entry *)entry,
> > - trace_flags, false);
> > + print_graph_retaddr(s, entry->args[0], trace_flags, false);
> >
> > if (print_retval) {
> > if (hex_format || (err_code == 0))
> > @@ -964,10 +954,12 @@ print_graph_entry_leaf(struct trace_iterator *iter,
> > trace_seq_printf(s, "%ps", (void *)ret_func);
> >
> > if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
> > - print_function_args(s, entry->args, ret_func);
> > + print_function_args(s, entry->args + ARGS_OFFS(args_size),
> > + ret_func);
> > trace_seq_putc(s, ';');
> > - } else
> > + } else {
>
> Ditto.
>
> > trace_seq_puts(s, "();");
> > + }
> > }
> > trace_seq_putc(s, '\n');
> >
> > @@ -1016,7 +1008,7 @@ print_graph_entry_nested(struct trace_iterator *iter,
> > args_size = iter->ent_size - offsetof(struct ftrace_graph_ent_entry, args);
> >
> > if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long))
> > - print_function_args(s, entry->args, func);
> > + print_function_args(s, entry->args + ARGS_OFFS(args_size), func);
> > else
> > trace_seq_puts(s, "()");
> >
> > @@ -1024,8 +1016,7 @@ print_graph_entry_nested(struct trace_iterator *iter,
> >
> > if (flags & __TRACE_GRAPH_PRINT_RETADDR &&
> > entry->ent.type == TRACE_GRAPH_RETADDR_ENT)
> > - print_graph_retaddr(s, (struct fgraph_retaddr_ent_entry *)entry,
> > - tr->trace_flags, true);
> > + print_graph_retaddr(s, entry->args[0], tr->trace_flags, true);
> > trace_seq_putc(s, '\n');
> >
> > if (trace_seq_has_overflowed(s))
> > @@ -1202,7 +1193,7 @@ print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s,
> > * it can be safely saved at the stack.
> > */
> > struct ftrace_graph_ent_entry *entry;
> > - u8 save_buf[sizeof(*entry) + FTRACE_REGS_MAX_ARGS * sizeof(long)];
> > + u8 save_buf[sizeof(*entry) + (FTRACE_REGS_MAX_ARGS + HAVE_RETADDR) * sizeof(long)];
> >
> > /* The ent_size is expected to be as big as the entry */
> > if (iter->ent_size > sizeof(save_buf))
> > @@ -1429,16 +1420,12 @@ print_graph_function_flags(struct trace_iterator *iter, u32 flags)
> > trace_assign_type(field, entry);
> > return print_graph_entry(field, s, iter, flags);
> > }
> > -#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> > case TRACE_GRAPH_RETADDR_ENT: {
> > - struct fgraph_retaddr_ent_entry saved;
> > struct fgraph_retaddr_ent_entry *rfield;
> >
> > trace_assign_type(rfield, entry);
> > - saved = *rfield;
> > - return print_graph_entry((struct ftrace_graph_ent_entry *)&saved, s, iter, flags);
> > + return print_graph_entry((typeof(field))rfield, s, iter, flags);
> > }
> > -#endif
> > case TRACE_GRAPH_RET: {
> > struct ftrace_graph_ret_entry *field;
> > trace_assign_type(field, entry);
> > --
> > 2.34.1
> >
>
>
> --
> Masami Hiramatsu (Google) <mhiramat@kernel.org>
On Wed, 12 Nov 2025 14:03:30 +0800
Donglin Peng <dolinux.peng@gmail.com> wrote:
> On Wed, Nov 12, 2025 at 1:17 PM Masami Hiramatsu <mhiramat@kernel.org> wrote:
> >
> > On Wed, 12 Nov 2025 11:43:33 +0800
> > Donglin Peng <dolinux.peng@gmail.com> wrote:
> >
> > > From: Donglin Peng <pengdonglin@xiaomi.com>
> > >
> > > Currently, the funcgraph-args and funcgraph-retaddr features are mutually exclusive.
> > > This patch resolves this limitation by modifying funcgraph-retaddr to adopt the same
> > > implementation approach as funcgraph-args, specifically by storing the return address
> > > in the first entry of the args array.
Ah, if you can update the patch, please keep each line shorter than
70-75 characters.
> > >
> > > As a result, both features now coexist seamlessly and function as intended.
> > >
> > > To verify the change, use perf to trace vfs_write with both options enabled:
> > >
> > > Before:
> > > # perf ftrace -G vfs_write --graph-opts args,retaddr
> > > ......
> > > 0) | down_read() { /* <-n_tty_write+0xa3/0x540 */
> > > 0) 0.075 us | __cond_resched(); /* <-down_read+0x12/0x160 */
> > > 0) 0.079 us | preempt_count_add(); /* <-down_read+0x3b/0x160 */
> > > 0) 0.077 us | preempt_count_sub(); /* <-down_read+0x8b/0x160 */
> > > 0) 0.754 us | }
> > >
> > > After:
> > > # perf ftrace -G vfs_write --graph-opts args,retaddr
> > > ......
> > > 0) | down_read(sem=0xffff8880100bea78) { /* <-n_tty_write+0xa3/0x540 */
> > > 0) 0.075 us | __cond_resched(); /* <-down_read+0x12/0x160 */
> > > 0) 0.079 us | preempt_count_add(val=1); /* <-down_read+0x3b/0x160 */
> > > 0) 0.077 us | preempt_count_sub(val=1); /* <-down_read+0x8b/0x160 */
> > > 0) 0.754 us | }
> > >
> > > Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
> > > Cc: Sven Schnelle <svens@linux.ibm.com>
> > > Cc: Masami Hiramatsu <mhiramat@kernel.org>
> > > Signed-off-by: Donglin Peng <pengdonglin@xiaomi.com>
> >
> > Looks good to me except for a few nits, but it's a style issue.
> >
> > Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>
> Thank you for ack.
>
> >
> > Thank you,
> >
> > > ---
> > > v3:
> > > - Replace min() with min_t() to improve type safety and maintainability
> > > - Keep only one Signed-off-by for cleaner attribution
> > > - Code refactoring for improved readability
> > >
> > > v2:
> > > - Preserve retaddr event functionality (suggested by Steven)
> > > - Store the retaddr in args[0] (suggested by Steven)
> > > - Refactor implementation logic and commit message clarity
> > > ---
> > > include/linux/ftrace.h | 11 --
> > > kernel/trace/trace.h | 4 -
> > > kernel/trace/trace_entries.h | 6 +-
> > > kernel/trace/trace_functions_graph.c | 145 ++++++++++++---------------
> > > 4 files changed, 69 insertions(+), 97 deletions(-)
> > >
> > > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > > index 7ded7df6e9b5..88cb54d73bdb 100644
> > > --- a/include/linux/ftrace.h
> > > +++ b/include/linux/ftrace.h
> > > @@ -1129,17 +1129,6 @@ struct ftrace_graph_ent {
> > > int depth;
> > > } __packed;
> > >
> > > -/*
> > > - * Structure that defines an entry function trace with retaddr.
> > > - * It's already packed but the attribute "packed" is needed
> > > - * to remove extra padding at the end.
> > > - */
> > > -struct fgraph_retaddr_ent {
> > > - unsigned long func; /* Current function */
> > > - int depth;
> > > - unsigned long retaddr; /* Return address */
> > > -} __packed;
> > > -
> > > /*
> > > * Structure that defines a return function trace.
> > > * It's already packed but the attribute "packed" is needed
> > > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> > > index 85eabb454bee..9fac291b913a 100644
> > > --- a/kernel/trace/trace.h
> > > +++ b/kernel/trace/trace.h
> > > @@ -955,10 +955,6 @@ extern void graph_trace_close(struct trace_iterator *iter);
> > > extern int __trace_graph_entry(struct trace_array *tr,
> > > struct ftrace_graph_ent *trace,
> > > unsigned int trace_ctx);
> > > -extern int __trace_graph_retaddr_entry(struct trace_array *tr,
> > > - struct ftrace_graph_ent *trace,
> > > - unsigned int trace_ctx,
> > > - unsigned long retaddr);
> > > extern void __trace_graph_return(struct trace_array *tr,
> > > struct ftrace_graph_ret *trace,
> > > unsigned int trace_ctx,
> > > diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
> > > index de294ae2c5c5..593a74663c65 100644
> > > --- a/kernel/trace/trace_entries.h
> > > +++ b/kernel/trace/trace_entries.h
> > > @@ -95,14 +95,14 @@ FTRACE_ENTRY_PACKED(fgraph_retaddr_entry, fgraph_retaddr_ent_entry,
> > > TRACE_GRAPH_RETADDR_ENT,
> > >
> > > F_STRUCT(
> > > - __field_struct( struct fgraph_retaddr_ent, graph_ent )
> > > + __field_struct( struct ftrace_graph_ent, graph_ent )
> > > __field_packed( unsigned long, graph_ent, func )
> > > __field_packed( unsigned int, graph_ent, depth )
> > > - __field_packed( unsigned long, graph_ent, retaddr )
> > > + __dynamic_array(unsigned long, args )
> > > ),
> > >
> > > F_printk("--> %ps (%u) <- %ps", (void *)__entry->func, __entry->depth,
> > > - (void *)__entry->retaddr)
> > > + (void *)__entry->args[0])
> > > );
> > >
> > > #else
> > > diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> > > index a7f4b9a47a71..f31eeeffbb2d 100644
> > > --- a/kernel/trace/trace_functions_graph.c
> > > +++ b/kernel/trace/trace_functions_graph.c
> > > @@ -16,6 +16,15 @@
> > > #include "trace.h"
> > > #include "trace_output.h"
> > >
> > > +#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> > > +#define HAVE_RETADDR 1
> > > +#define ARGS_OFFS(args_size) \
> > > + ((args_size) > FTRACE_REGS_MAX_ARGS * sizeof(long) ? 1 : 0)
> > > +#else
> > > +#define HAVE_RETADDR 0
> > > +#define ARGS_OFFS(args_size) 0
> > > +#endif
> > > +
> > > /* When set, irq functions will be ignored */
> > > static int ftrace_graph_skip_irqs;
> > >
> > > @@ -27,21 +36,25 @@ struct fgraph_cpu_data {
> > > unsigned long enter_funcs[FTRACE_RETFUNC_DEPTH];
> > > };
> > >
> > > +/*
> > > + * fgraph_retaddr_ent_entry and ftrace_graph_ent_entry share layout, ent
> > > + * member repurposed for storage
> > > + */
> > > struct fgraph_ent_args {
> > > struct ftrace_graph_ent_entry ent;
> > > - /* Force the sizeof of args[] to have FTRACE_REGS_MAX_ARGS entries */
> > > - unsigned long args[FTRACE_REGS_MAX_ARGS];
> > > + /*
> > > + * Force the sizeof of args[] to have (FTRACE_REGS_MAX_ARGS + HAVE_RETADDR)
> > > + * entries with the first entry storing the return address for
> > > + * TRACE_GRAPH_RETADDR_ENT.
> > > + */
> > > + unsigned long args[FTRACE_REGS_MAX_ARGS + HAVE_RETADDR];
> > > };
> > >
> > > struct fgraph_data {
> > > struct fgraph_cpu_data __percpu *cpu_data;
> > >
> > > /* Place to preserve last processed entry. */
> > > - union {
> > > - struct fgraph_ent_args ent;
> > > - /* TODO allow retaddr to have args */
> > > - struct fgraph_retaddr_ent_entry rent;
> > > - };
> > > + struct fgraph_ent_args ent;
> > > struct ftrace_graph_ret_entry ret;
> > > int failed;
> > > int cpu;
> > > @@ -127,22 +140,43 @@ static int __graph_entry(struct trace_array *tr, struct ftrace_graph_ent *trace,
> > > struct ring_buffer_event *event;
> > > struct trace_buffer *buffer = tr->array_buffer.buffer;
> > > struct ftrace_graph_ent_entry *entry;
> > > - int size;
> > > + unsigned long retaddr = 0;
> > > + int size = sizeof(*entry);
> > > + int type = TRACE_GRAPH_ENT;
> > > + bool store_args = false;
> > > + int nr_args = 0, args_offs = 0;
> > > +
> > > + if (tracer_flags_is_set(TRACE_GRAPH_PRINT_RETADDR)) {
> > > + retaddr = ftrace_graph_top_ret_addr(current);
> > > + type = TRACE_GRAPH_RETADDR_ENT;
> > > + nr_args += 1;
> > > + }
> > >
> > > /* If fregs is defined, add FTRACE_REGS_MAX_ARGS long size words */
> > > - size = sizeof(*entry) + (FTRACE_REGS_MAX_ARGS * !!fregs * sizeof(long));
> > > + if (tracer_flags_is_set(TRACE_GRAPH_ARGS)) {
> > > + store_args = !!fregs;
> > > + if (store_args)
> > > + nr_args += FTRACE_REGS_MAX_ARGS;
> > > + }
> > >
> > > - event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_ENT, size, trace_ctx);
> > > + size += nr_args * sizeof(long);
> > > + event = trace_buffer_lock_reserve(buffer, type, size, trace_ctx);
> > > if (!event)
> > > return 0;
> > >
> > > entry = ring_buffer_event_data(event);
> > > entry->graph_ent = *trace;
> > >
> > > + /* Store the retaddr in args[0] */
> > > + if (type == TRACE_GRAPH_RETADDR_ENT) {
> > > + entry->args[0] = retaddr;
> > > + args_offs += 1;
> > > + }
> > > +
> > > #ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
> > > - if (fregs) {
> > > + if (store_args) {
> > > for (int i = 0; i < FTRACE_REGS_MAX_ARGS; i++)
> > > - entry->args[i] = ftrace_regs_get_argument(fregs, i);
> > > + entry->args[i + args_offs] = ftrace_regs_get_argument(fregs, i);
> > > }
> > > #endif
> > >
> > > @@ -158,38 +192,6 @@ int __trace_graph_entry(struct trace_array *tr,
> > > return __graph_entry(tr, trace, trace_ctx, NULL);
> > > }
> > >
> > > -#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> > > -int __trace_graph_retaddr_entry(struct trace_array *tr,
> > > - struct ftrace_graph_ent *trace,
> > > - unsigned int trace_ctx,
> > > - unsigned long retaddr)
> > > -{
> > > - struct ring_buffer_event *event;
> > > - struct trace_buffer *buffer = tr->array_buffer.buffer;
> > > - struct fgraph_retaddr_ent_entry *entry;
> > > -
> > > - event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_RETADDR_ENT,
> > > - sizeof(*entry), trace_ctx);
> > > - if (!event)
> > > - return 0;
> > > - entry = ring_buffer_event_data(event);
> > > - entry->graph_ent.func = trace->func;
> > > - entry->graph_ent.depth = trace->depth;
> > > - entry->graph_ent.retaddr = retaddr;
> > > - trace_buffer_unlock_commit_nostack(buffer, event);
> > > -
> > > - return 1;
> > > -}
> > > -#else
> > > -int __trace_graph_retaddr_entry(struct trace_array *tr,
> > > - struct ftrace_graph_ent *trace,
> > > - unsigned int trace_ctx,
> > > - unsigned long retaddr)
> > > -{
> > > - return 1;
> > > -}
> > > -#endif
> > > -
> > > static inline int ftrace_graph_ignore_irqs(void)
> > > {
> > > if (!ftrace_graph_skip_irqs || trace_recursion_test(TRACE_IRQ_BIT))
> > > @@ -211,7 +213,6 @@ static int graph_entry(struct ftrace_graph_ent *trace,
> > > struct trace_array *tr = gops->private;
> > > struct fgraph_times *ftimes;
> > > unsigned int trace_ctx;
> > > - int ret = 0;
> > >
> > > if (*task_var & TRACE_GRAPH_NOTRACE)
> > > return 0;
> > > @@ -262,15 +263,7 @@ static int graph_entry(struct ftrace_graph_ent *trace,
> > > return 1;
> > >
> > > trace_ctx = tracing_gen_ctx();
> > > - if (IS_ENABLED(CONFIG_FUNCTION_GRAPH_RETADDR) &&
> > > - tracer_flags_is_set(TRACE_GRAPH_PRINT_RETADDR)) {
> > > - unsigned long retaddr = ftrace_graph_top_ret_addr(current);
> > > - ret = __trace_graph_retaddr_entry(tr, trace, trace_ctx, retaddr);
> > > - } else {
> > > - ret = __graph_entry(tr, trace, trace_ctx, fregs);
> > > - }
> > > -
> > > - return ret;
> > > + return __graph_entry(tr, trace, trace_ctx, fregs);
> > > }
> > >
> > > int trace_graph_entry(struct ftrace_graph_ent *trace,
> > > @@ -634,13 +627,9 @@ get_return_for_leaf(struct trace_iterator *iter,
> > > * Save current and next entries for later reference
> > > * if the output fails.
> > > */
> > > - if (unlikely(curr->ent.type == TRACE_GRAPH_RETADDR_ENT)) {
> > > - data->rent = *(struct fgraph_retaddr_ent_entry *)curr;
> > > - } else {
> > > - int size = min((int)sizeof(data->ent), (int)iter->ent_size);
> > > + int size = min_t(int, sizeof(data->ent), iter->ent_size);
> > >
> > > - memcpy(&data->ent, curr, size);
> > > - }
> > > + memcpy(&data->ent, curr, size);
> > > /*
> > > * If the next event is not a return type, then
> > > * we only care about what type it is. Otherwise we can
> > > @@ -811,21 +800,21 @@ print_graph_duration(struct trace_array *tr, unsigned long long duration,
> > >
> > > #ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> > > #define __TRACE_GRAPH_PRINT_RETADDR TRACE_GRAPH_PRINT_RETADDR
> > > -static void print_graph_retaddr(struct trace_seq *s, struct fgraph_retaddr_ent_entry *entry,
> > > - u32 trace_flags, bool comment)
> > > +static void print_graph_retaddr(struct trace_seq *s, unsigned long retaddr, u32 trace_flags,
> > > + bool comment)
> > > {
> > > if (comment)
> > > trace_seq_puts(s, " /*");
> > >
> > > trace_seq_puts(s, " <-");
> > > - seq_print_ip_sym(s, entry->graph_ent.retaddr, trace_flags | TRACE_ITER_SYM_OFFSET);
> > > + seq_print_ip_sym(s, retaddr, trace_flags | TRACE_ITER_SYM_OFFSET);
> > >
> > > if (comment)
> > > trace_seq_puts(s, " */");
> > > }
> > > #else
> > > #define __TRACE_GRAPH_PRINT_RETADDR 0
> > > -#define print_graph_retaddr(_seq, _entry, _tflags, _comment) do { } while (0)
> > > +#define print_graph_retaddr(_seq, _retaddr, _tflags, _comment) do { } while (0)
> > > #endif
> > >
> > > #if defined(CONFIG_FUNCTION_GRAPH_RETVAL) || defined(CONFIG_FUNCTION_GRAPH_RETADDR)
> > > @@ -869,10 +858,12 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
> > > trace_seq_printf(s, "%ps", func);
> > >
> > > if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
> > > - print_function_args(s, entry->args, (unsigned long)func);
> > > + print_function_args(s, entry->args + ARGS_OFFS(args_size),
> > > + (unsigned long)func);
> > > trace_seq_putc(s, ';');
> > > - } else
> > > + } else {
> >
> > nit: you don't need to add braces for a single line block.
>
> Thanks. I added the else braces for consistency with the
> multi-statement if branch,
> per coding-style.rst. Happy to remove if you prefer the
> single-statement exception.
Ah, OK. I also checked this passed checkpatch.pl. (some other
macros are warned but those are false positive.)
Thanks,
>
> https://elixir.bootlin.com/linux/v6.18-rc5/source/Documentation/process/coding-style.rst#L213
>
> Do not unnecessarily use braces where a single statement will do.
>
> .. code-block:: c
>
> if (condition)
> action();
>
> and
>
> .. code-block:: c
>
> if (condition)
> do_this();
> else
> do_that();
>
> This does not apply if only one branch of a conditional statement is a single
> statement; in the latter case use braces in both branches:
>
> .. code-block:: c
>
> if (condition) {
> do_this();
> do_that();
> } else {
> otherwise();
> }
>
> >
> > > trace_seq_puts(s, "();");
> > > + }
> > >
> > > if (print_retval || print_retaddr)
> > > trace_seq_puts(s, " /*");
> > > @@ -882,8 +873,7 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
> > > }
> > >
> > > if (print_retaddr)
> > > - print_graph_retaddr(s, (struct fgraph_retaddr_ent_entry *)entry,
> > > - trace_flags, false);
> > > + print_graph_retaddr(s, entry->args[0], trace_flags, false);
> > >
> > > if (print_retval) {
> > > if (hex_format || (err_code == 0))
> > > @@ -964,10 +954,12 @@ print_graph_entry_leaf(struct trace_iterator *iter,
> > > trace_seq_printf(s, "%ps", (void *)ret_func);
> > >
> > > if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
> > > - print_function_args(s, entry->args, ret_func);
> > > + print_function_args(s, entry->args + ARGS_OFFS(args_size),
> > > + ret_func);
> > > trace_seq_putc(s, ';');
> > > - } else
> > > + } else {
> >
> > Ditto.
> >
> > > trace_seq_puts(s, "();");
> > > + }
> > > }
> > > trace_seq_putc(s, '\n');
> > >
> > > @@ -1016,7 +1008,7 @@ print_graph_entry_nested(struct trace_iterator *iter,
> > > args_size = iter->ent_size - offsetof(struct ftrace_graph_ent_entry, args);
> > >
> > > if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long))
> > > - print_function_args(s, entry->args, func);
> > > + print_function_args(s, entry->args + ARGS_OFFS(args_size), func);
> > > else
> > > trace_seq_puts(s, "()");
> > >
> > > @@ -1024,8 +1016,7 @@ print_graph_entry_nested(struct trace_iterator *iter,
> > >
> > > if (flags & __TRACE_GRAPH_PRINT_RETADDR &&
> > > entry->ent.type == TRACE_GRAPH_RETADDR_ENT)
> > > - print_graph_retaddr(s, (struct fgraph_retaddr_ent_entry *)entry,
> > > - tr->trace_flags, true);
> > > + print_graph_retaddr(s, entry->args[0], tr->trace_flags, true);
> > > trace_seq_putc(s, '\n');
> > >
> > > if (trace_seq_has_overflowed(s))
> > > @@ -1202,7 +1193,7 @@ print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s,
> > > * it can be safely saved at the stack.
> > > */
> > > struct ftrace_graph_ent_entry *entry;
> > > - u8 save_buf[sizeof(*entry) + FTRACE_REGS_MAX_ARGS * sizeof(long)];
> > > + u8 save_buf[sizeof(*entry) + (FTRACE_REGS_MAX_ARGS + HAVE_RETADDR) * sizeof(long)];
> > >
> > > /* The ent_size is expected to be as big as the entry */
> > > if (iter->ent_size > sizeof(save_buf))
> > > @@ -1429,16 +1420,12 @@ print_graph_function_flags(struct trace_iterator *iter, u32 flags)
> > > trace_assign_type(field, entry);
> > > return print_graph_entry(field, s, iter, flags);
> > > }
> > > -#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> > > case TRACE_GRAPH_RETADDR_ENT: {
> > > - struct fgraph_retaddr_ent_entry saved;
> > > struct fgraph_retaddr_ent_entry *rfield;
> > >
> > > trace_assign_type(rfield, entry);
> > > - saved = *rfield;
> > > - return print_graph_entry((struct ftrace_graph_ent_entry *)&saved, s, iter, flags);
> > > + return print_graph_entry((typeof(field))rfield, s, iter, flags);
> > > }
> > > -#endif
> > > case TRACE_GRAPH_RET: {
> > > struct ftrace_graph_ret_entry *field;
> > > trace_assign_type(field, entry);
> > > --
> > > 2.34.1
> > >
> >
> >
> > --
> > Masami Hiramatsu (Google) <mhiramat@kernel.org>
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
On Wed, Nov 12, 2025 at 3:10 PM Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> On Wed, 12 Nov 2025 14:03:30 +0800
> Donglin Peng <dolinux.peng@gmail.com> wrote:
>
> > On Wed, Nov 12, 2025 at 1:17 PM Masami Hiramatsu <mhiramat@kernel.org> wrote:
> > >
> > > On Wed, 12 Nov 2025 11:43:33 +0800
> > > Donglin Peng <dolinux.peng@gmail.com> wrote:
> > >
> > > > From: Donglin Peng <pengdonglin@xiaomi.com>
> > > >
> > > > Currently, the funcgraph-args and funcgraph-retaddr features are mutually exclusive.
> > > > This patch resolves this limitation by modifying funcgraph-retaddr to adopt the same
> > > > implementation approach as funcgraph-args, specifically by storing the return address
> > > > in the first entry of the args array.
>
> Ah, if you can update the patch, please keep each line shorter than
> 70-75 characters.
Thanks, I will fix it in the next version.
>
> > > >
> > > > As a result, both features now coexist seamlessly and function as intended.
> > > >
> > > > To verify the change, use perf to trace vfs_write with both options enabled:
> > > >
> > > > Before:
> > > > # perf ftrace -G vfs_write --graph-opts args,retaddr
> > > > ......
> > > > 0) | down_read() { /* <-n_tty_write+0xa3/0x540 */
> > > > 0) 0.075 us | __cond_resched(); /* <-down_read+0x12/0x160 */
> > > > 0) 0.079 us | preempt_count_add(); /* <-down_read+0x3b/0x160 */
> > > > 0) 0.077 us | preempt_count_sub(); /* <-down_read+0x8b/0x160 */
> > > > 0) 0.754 us | }
> > > >
> > > > After:
> > > > # perf ftrace -G vfs_write --graph-opts args,retaddr
> > > > ......
> > > > 0) | down_read(sem=0xffff8880100bea78) { /* <-n_tty_write+0xa3/0x540 */
> > > > 0) 0.075 us | __cond_resched(); /* <-down_read+0x12/0x160 */
> > > > 0) 0.079 us | preempt_count_add(val=1); /* <-down_read+0x3b/0x160 */
> > > > 0) 0.077 us | preempt_count_sub(val=1); /* <-down_read+0x8b/0x160 */
> > > > 0) 0.754 us | }
> > > >
> > > > Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
> > > > Cc: Sven Schnelle <svens@linux.ibm.com>
> > > > Cc: Masami Hiramatsu <mhiramat@kernel.org>
> > > > Signed-off-by: Donglin Peng <pengdonglin@xiaomi.com>
> > >
> > > Looks good to me except for a few nits, but it's a style issue.
> > >
> > > Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> >
> > Thank you for ack.
> >
> > >
> > > Thank you,
> > >
> > > > ---
> > > > v3:
> > > > - Replace min() with min_t() to improve type safety and maintainability
> > > > - Keep only one Signed-off-by for cleaner attribution
> > > > - Code refactoring for improved readability
> > > >
> > > > v2:
> > > > - Preserve retaddr event functionality (suggested by Steven)
> > > > - Store the retaddr in args[0] (suggested by Steven)
> > > > - Refactor implementation logic and commit message clarity
> > > > ---
> > > > include/linux/ftrace.h | 11 --
> > > > kernel/trace/trace.h | 4 -
> > > > kernel/trace/trace_entries.h | 6 +-
> > > > kernel/trace/trace_functions_graph.c | 145 ++++++++++++---------------
> > > > 4 files changed, 69 insertions(+), 97 deletions(-)
> > > >
> > > > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > > > index 7ded7df6e9b5..88cb54d73bdb 100644
> > > > --- a/include/linux/ftrace.h
> > > > +++ b/include/linux/ftrace.h
> > > > @@ -1129,17 +1129,6 @@ struct ftrace_graph_ent {
> > > > int depth;
> > > > } __packed;
> > > >
> > > > -/*
> > > > - * Structure that defines an entry function trace with retaddr.
> > > > - * It's already packed but the attribute "packed" is needed
> > > > - * to remove extra padding at the end.
> > > > - */
> > > > -struct fgraph_retaddr_ent {
> > > > - unsigned long func; /* Current function */
> > > > - int depth;
> > > > - unsigned long retaddr; /* Return address */
> > > > -} __packed;
> > > > -
> > > > /*
> > > > * Structure that defines a return function trace.
> > > > * It's already packed but the attribute "packed" is needed
> > > > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> > > > index 85eabb454bee..9fac291b913a 100644
> > > > --- a/kernel/trace/trace.h
> > > > +++ b/kernel/trace/trace.h
> > > > @@ -955,10 +955,6 @@ extern void graph_trace_close(struct trace_iterator *iter);
> > > > extern int __trace_graph_entry(struct trace_array *tr,
> > > > struct ftrace_graph_ent *trace,
> > > > unsigned int trace_ctx);
> > > > -extern int __trace_graph_retaddr_entry(struct trace_array *tr,
> > > > - struct ftrace_graph_ent *trace,
> > > > - unsigned int trace_ctx,
> > > > - unsigned long retaddr);
> > > > extern void __trace_graph_return(struct trace_array *tr,
> > > > struct ftrace_graph_ret *trace,
> > > > unsigned int trace_ctx,
> > > > diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
> > > > index de294ae2c5c5..593a74663c65 100644
> > > > --- a/kernel/trace/trace_entries.h
> > > > +++ b/kernel/trace/trace_entries.h
> > > > @@ -95,14 +95,14 @@ FTRACE_ENTRY_PACKED(fgraph_retaddr_entry, fgraph_retaddr_ent_entry,
> > > > TRACE_GRAPH_RETADDR_ENT,
> > > >
> > > > F_STRUCT(
> > > > - __field_struct( struct fgraph_retaddr_ent, graph_ent )
> > > > + __field_struct( struct ftrace_graph_ent, graph_ent )
> > > > __field_packed( unsigned long, graph_ent, func )
> > > > __field_packed( unsigned int, graph_ent, depth )
> > > > - __field_packed( unsigned long, graph_ent, retaddr )
> > > > + __dynamic_array(unsigned long, args )
> > > > ),
> > > >
> > > > F_printk("--> %ps (%u) <- %ps", (void *)__entry->func, __entry->depth,
> > > > - (void *)__entry->retaddr)
> > > > + (void *)__entry->args[0])
> > > > );
> > > >
> > > > #else
> > > > diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> > > > index a7f4b9a47a71..f31eeeffbb2d 100644
> > > > --- a/kernel/trace/trace_functions_graph.c
> > > > +++ b/kernel/trace/trace_functions_graph.c
> > > > @@ -16,6 +16,15 @@
> > > > #include "trace.h"
> > > > #include "trace_output.h"
> > > >
> > > > +#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> > > > +#define HAVE_RETADDR 1
> > > > +#define ARGS_OFFS(args_size) \
> > > > + ((args_size) > FTRACE_REGS_MAX_ARGS * sizeof(long) ? 1 : 0)
> > > > +#else
> > > > +#define HAVE_RETADDR 0
> > > > +#define ARGS_OFFS(args_size) 0
> > > > +#endif
> > > > +
> > > > /* When set, irq functions will be ignored */
> > > > static int ftrace_graph_skip_irqs;
> > > >
> > > > @@ -27,21 +36,25 @@ struct fgraph_cpu_data {
> > > > unsigned long enter_funcs[FTRACE_RETFUNC_DEPTH];
> > > > };
> > > >
> > > > +/*
> > > > + * fgraph_retaddr_ent_entry and ftrace_graph_ent_entry share layout, ent
> > > > + * member repurposed for storage
> > > > + */
> > > > struct fgraph_ent_args {
> > > > struct ftrace_graph_ent_entry ent;
> > > > - /* Force the sizeof of args[] to have FTRACE_REGS_MAX_ARGS entries */
> > > > - unsigned long args[FTRACE_REGS_MAX_ARGS];
> > > > + /*
> > > > + * Force the sizeof of args[] to have (FTRACE_REGS_MAX_ARGS + HAVE_RETADDR)
> > > > + * entries with the first entry storing the return address for
> > > > + * TRACE_GRAPH_RETADDR_ENT.
> > > > + */
> > > > + unsigned long args[FTRACE_REGS_MAX_ARGS + HAVE_RETADDR];
> > > > };
> > > >
> > > > struct fgraph_data {
> > > > struct fgraph_cpu_data __percpu *cpu_data;
> > > >
> > > > /* Place to preserve last processed entry. */
> > > > - union {
> > > > - struct fgraph_ent_args ent;
> > > > - /* TODO allow retaddr to have args */
> > > > - struct fgraph_retaddr_ent_entry rent;
> > > > - };
> > > > + struct fgraph_ent_args ent;
> > > > struct ftrace_graph_ret_entry ret;
> > > > int failed;
> > > > int cpu;
> > > > @@ -127,22 +140,43 @@ static int __graph_entry(struct trace_array *tr, struct ftrace_graph_ent *trace,
> > > > struct ring_buffer_event *event;
> > > > struct trace_buffer *buffer = tr->array_buffer.buffer;
> > > > struct ftrace_graph_ent_entry *entry;
> > > > - int size;
> > > > + unsigned long retaddr = 0;
> > > > + int size = sizeof(*entry);
> > > > + int type = TRACE_GRAPH_ENT;
> > > > + bool store_args = false;
> > > > + int nr_args = 0, args_offs = 0;
> > > > +
> > > > + if (tracer_flags_is_set(TRACE_GRAPH_PRINT_RETADDR)) {
> > > > + retaddr = ftrace_graph_top_ret_addr(current);
> > > > + type = TRACE_GRAPH_RETADDR_ENT;
> > > > + nr_args += 1;
> > > > + }
> > > >
> > > > /* If fregs is defined, add FTRACE_REGS_MAX_ARGS long size words */
> > > > - size = sizeof(*entry) + (FTRACE_REGS_MAX_ARGS * !!fregs * sizeof(long));
> > > > + if (tracer_flags_is_set(TRACE_GRAPH_ARGS)) {
> > > > + store_args = !!fregs;
> > > > + if (store_args)
> > > > + nr_args += FTRACE_REGS_MAX_ARGS;
> > > > + }
> > > >
> > > > - event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_ENT, size, trace_ctx);
> > > > + size += nr_args * sizeof(long);
> > > > + event = trace_buffer_lock_reserve(buffer, type, size, trace_ctx);
> > > > if (!event)
> > > > return 0;
> > > >
> > > > entry = ring_buffer_event_data(event);
> > > > entry->graph_ent = *trace;
> > > >
> > > > + /* Store the retaddr in args[0] */
> > > > + if (type == TRACE_GRAPH_RETADDR_ENT) {
> > > > + entry->args[0] = retaddr;
> > > > + args_offs += 1;
> > > > + }
> > > > +
> > > > #ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
> > > > - if (fregs) {
> > > > + if (store_args) {
> > > > for (int i = 0; i < FTRACE_REGS_MAX_ARGS; i++)
> > > > - entry->args[i] = ftrace_regs_get_argument(fregs, i);
> > > > + entry->args[i + args_offs] = ftrace_regs_get_argument(fregs, i);
> > > > }
> > > > #endif
> > > >
> > > > @@ -158,38 +192,6 @@ int __trace_graph_entry(struct trace_array *tr,
> > > > return __graph_entry(tr, trace, trace_ctx, NULL);
> > > > }
> > > >
> > > > -#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> > > > -int __trace_graph_retaddr_entry(struct trace_array *tr,
> > > > - struct ftrace_graph_ent *trace,
> > > > - unsigned int trace_ctx,
> > > > - unsigned long retaddr)
> > > > -{
> > > > - struct ring_buffer_event *event;
> > > > - struct trace_buffer *buffer = tr->array_buffer.buffer;
> > > > - struct fgraph_retaddr_ent_entry *entry;
> > > > -
> > > > - event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_RETADDR_ENT,
> > > > - sizeof(*entry), trace_ctx);
> > > > - if (!event)
> > > > - return 0;
> > > > - entry = ring_buffer_event_data(event);
> > > > - entry->graph_ent.func = trace->func;
> > > > - entry->graph_ent.depth = trace->depth;
> > > > - entry->graph_ent.retaddr = retaddr;
> > > > - trace_buffer_unlock_commit_nostack(buffer, event);
> > > > -
> > > > - return 1;
> > > > -}
> > > > -#else
> > > > -int __trace_graph_retaddr_entry(struct trace_array *tr,
> > > > - struct ftrace_graph_ent *trace,
> > > > - unsigned int trace_ctx,
> > > > - unsigned long retaddr)
> > > > -{
> > > > - return 1;
> > > > -}
> > > > -#endif
> > > > -
> > > > static inline int ftrace_graph_ignore_irqs(void)
> > > > {
> > > > if (!ftrace_graph_skip_irqs || trace_recursion_test(TRACE_IRQ_BIT))
> > > > @@ -211,7 +213,6 @@ static int graph_entry(struct ftrace_graph_ent *trace,
> > > > struct trace_array *tr = gops->private;
> > > > struct fgraph_times *ftimes;
> > > > unsigned int trace_ctx;
> > > > - int ret = 0;
> > > >
> > > > if (*task_var & TRACE_GRAPH_NOTRACE)
> > > > return 0;
> > > > @@ -262,15 +263,7 @@ static int graph_entry(struct ftrace_graph_ent *trace,
> > > > return 1;
> > > >
> > > > trace_ctx = tracing_gen_ctx();
> > > > - if (IS_ENABLED(CONFIG_FUNCTION_GRAPH_RETADDR) &&
> > > > - tracer_flags_is_set(TRACE_GRAPH_PRINT_RETADDR)) {
> > > > - unsigned long retaddr = ftrace_graph_top_ret_addr(current);
> > > > - ret = __trace_graph_retaddr_entry(tr, trace, trace_ctx, retaddr);
> > > > - } else {
> > > > - ret = __graph_entry(tr, trace, trace_ctx, fregs);
> > > > - }
> > > > -
> > > > - return ret;
> > > > + return __graph_entry(tr, trace, trace_ctx, fregs);
> > > > }
> > > >
> > > > int trace_graph_entry(struct ftrace_graph_ent *trace,
> > > > @@ -634,13 +627,9 @@ get_return_for_leaf(struct trace_iterator *iter,
> > > > * Save current and next entries for later reference
> > > > * if the output fails.
> > > > */
> > > > - if (unlikely(curr->ent.type == TRACE_GRAPH_RETADDR_ENT)) {
> > > > - data->rent = *(struct fgraph_retaddr_ent_entry *)curr;
> > > > - } else {
> > > > - int size = min((int)sizeof(data->ent), (int)iter->ent_size);
> > > > + int size = min_t(int, sizeof(data->ent), iter->ent_size);
> > > >
> > > > - memcpy(&data->ent, curr, size);
> > > > - }
> > > > + memcpy(&data->ent, curr, size);
> > > > /*
> > > > * If the next event is not a return type, then
> > > > * we only care about what type it is. Otherwise we can
> > > > @@ -811,21 +800,21 @@ print_graph_duration(struct trace_array *tr, unsigned long long duration,
> > > >
> > > > #ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> > > > #define __TRACE_GRAPH_PRINT_RETADDR TRACE_GRAPH_PRINT_RETADDR
> > > > -static void print_graph_retaddr(struct trace_seq *s, struct fgraph_retaddr_ent_entry *entry,
> > > > - u32 trace_flags, bool comment)
> > > > +static void print_graph_retaddr(struct trace_seq *s, unsigned long retaddr, u32 trace_flags,
> > > > + bool comment)
> > > > {
> > > > if (comment)
> > > > trace_seq_puts(s, " /*");
> > > >
> > > > trace_seq_puts(s, " <-");
> > > > - seq_print_ip_sym(s, entry->graph_ent.retaddr, trace_flags | TRACE_ITER_SYM_OFFSET);
> > > > + seq_print_ip_sym(s, retaddr, trace_flags | TRACE_ITER_SYM_OFFSET);
> > > >
> > > > if (comment)
> > > > trace_seq_puts(s, " */");
> > > > }
> > > > #else
> > > > #define __TRACE_GRAPH_PRINT_RETADDR 0
> > > > -#define print_graph_retaddr(_seq, _entry, _tflags, _comment) do { } while (0)
> > > > +#define print_graph_retaddr(_seq, _retaddr, _tflags, _comment) do { } while (0)
> > > > #endif
> > > >
> > > > #if defined(CONFIG_FUNCTION_GRAPH_RETVAL) || defined(CONFIG_FUNCTION_GRAPH_RETADDR)
> > > > @@ -869,10 +858,12 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
> > > > trace_seq_printf(s, "%ps", func);
> > > >
> > > > if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
> > > > - print_function_args(s, entry->args, (unsigned long)func);
> > > > + print_function_args(s, entry->args + ARGS_OFFS(args_size),
> > > > + (unsigned long)func);
> > > > trace_seq_putc(s, ';');
> > > > - } else
> > > > + } else {
> > >
> > > nit: you don't need to add braces for a single line block.
> >
> > Thanks. I added the else braces for consistency with the
> > multi-statement if branch,
> > per coding-style.rst. Happy to remove if you prefer the
> > single-statement exception.
>
> Ah, OK. I also checked this passed checkpatch.pl. (some other
> macros are warned but those are false positive.)
Thanks.
>
> Thanks,
>
> >
> > https://elixir.bootlin.com/linux/v6.18-rc5/source/Documentation/process/coding-style.rst#L213
> >
> > Do not unnecessarily use braces where a single statement will do.
> >
> > .. code-block:: c
> >
> > if (condition)
> > action();
> >
> > and
> >
> > .. code-block:: c
> >
> > if (condition)
> > do_this();
> > else
> > do_that();
> >
> > This does not apply if only one branch of a conditional statement is a single
> > statement; in the latter case use braces in both branches:
> >
> > .. code-block:: c
> >
> > if (condition) {
> > do_this();
> > do_that();
> > } else {
> > otherwise();
> > }
> >
> > >
> > > > trace_seq_puts(s, "();");
> > > > + }
> > > >
> > > > if (print_retval || print_retaddr)
> > > > trace_seq_puts(s, " /*");
> > > > @@ -882,8 +873,7 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
> > > > }
> > > >
> > > > if (print_retaddr)
> > > > - print_graph_retaddr(s, (struct fgraph_retaddr_ent_entry *)entry,
> > > > - trace_flags, false);
> > > > + print_graph_retaddr(s, entry->args[0], trace_flags, false);
> > > >
> > > > if (print_retval) {
> > > > if (hex_format || (err_code == 0))
> > > > @@ -964,10 +954,12 @@ print_graph_entry_leaf(struct trace_iterator *iter,
> > > > trace_seq_printf(s, "%ps", (void *)ret_func);
> > > >
> > > > if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
> > > > - print_function_args(s, entry->args, ret_func);
> > > > + print_function_args(s, entry->args + ARGS_OFFS(args_size),
> > > > + ret_func);
> > > > trace_seq_putc(s, ';');
> > > > - } else
> > > > + } else {
> > >
> > > Ditto.
> > >
> > > > trace_seq_puts(s, "();");
> > > > + }
> > > > }
> > > > trace_seq_putc(s, '\n');
> > > >
> > > > @@ -1016,7 +1008,7 @@ print_graph_entry_nested(struct trace_iterator *iter,
> > > > args_size = iter->ent_size - offsetof(struct ftrace_graph_ent_entry, args);
> > > >
> > > > if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long))
> > > > - print_function_args(s, entry->args, func);
> > > > + print_function_args(s, entry->args + ARGS_OFFS(args_size), func);
> > > > else
> > > > trace_seq_puts(s, "()");
> > > >
> > > > @@ -1024,8 +1016,7 @@ print_graph_entry_nested(struct trace_iterator *iter,
> > > >
> > > > if (flags & __TRACE_GRAPH_PRINT_RETADDR &&
> > > > entry->ent.type == TRACE_GRAPH_RETADDR_ENT)
> > > > - print_graph_retaddr(s, (struct fgraph_retaddr_ent_entry *)entry,
> > > > - tr->trace_flags, true);
> > > > + print_graph_retaddr(s, entry->args[0], tr->trace_flags, true);
> > > > trace_seq_putc(s, '\n');
> > > >
> > > > if (trace_seq_has_overflowed(s))
> > > > @@ -1202,7 +1193,7 @@ print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s,
> > > > * it can be safely saved at the stack.
> > > > */
> > > > struct ftrace_graph_ent_entry *entry;
> > > > - u8 save_buf[sizeof(*entry) + FTRACE_REGS_MAX_ARGS * sizeof(long)];
> > > > + u8 save_buf[sizeof(*entry) + (FTRACE_REGS_MAX_ARGS + HAVE_RETADDR) * sizeof(long)];
> > > >
> > > > /* The ent_size is expected to be as big as the entry */
> > > > if (iter->ent_size > sizeof(save_buf))
> > > > @@ -1429,16 +1420,12 @@ print_graph_function_flags(struct trace_iterator *iter, u32 flags)
> > > > trace_assign_type(field, entry);
> > > > return print_graph_entry(field, s, iter, flags);
> > > > }
> > > > -#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
> > > > case TRACE_GRAPH_RETADDR_ENT: {
> > > > - struct fgraph_retaddr_ent_entry saved;
> > > > struct fgraph_retaddr_ent_entry *rfield;
> > > >
> > > > trace_assign_type(rfield, entry);
> > > > - saved = *rfield;
> > > > - return print_graph_entry((struct ftrace_graph_ent_entry *)&saved, s, iter, flags);
> > > > + return print_graph_entry((typeof(field))rfield, s, iter, flags);
> > > > }
> > > > -#endif
> > > > case TRACE_GRAPH_RET: {
> > > > struct ftrace_graph_ret_entry *field;
> > > > trace_assign_type(field, entry);
> > > > --
> > > > 2.34.1
> > > >
> > >
> > >
> > > --
> > > Masami Hiramatsu (Google) <mhiramat@kernel.org>
>
>
> --
> Masami Hiramatsu (Google) <mhiramat@kernel.org>
© 2016 - 2026 Red Hat, Inc.