The following commit has been merged into the objtool/core branch of tip:
Commit-ID: fcb268b47a2f4a497fdb40ef24bb9e06488b7213
Gitweb: https://git.kernel.org/tip/fcb268b47a2f4a497fdb40ef24bb9e06488b7213
Author: Alexandre Chartre <alexandre.chartre@oracle.com>
AuthorDate: Fri, 21 Nov 2025 10:53:21 +01:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 21 Nov 2025 15:30:10 +01:00
objtool: Trace instruction state changes during function validation
During function validation, objtool maintains a per-instruction state,
in particular to track call frame information. When tracing validation,
print any instruction state changes.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-12-alexandre.chartre@oracle.com
---
tools/objtool/check.c | 8 +-
tools/objtool/include/objtool/trace.h | 10 ++-
tools/objtool/trace.c | 132 +++++++++++++++++++++++++-
3 files changed, 149 insertions(+), 1 deletion(-)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 409dec9..a02f8db 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -3677,6 +3677,8 @@ static int validate_insn(struct objtool_file *file, struct symbol *func,
struct instruction *prev_insn, struct instruction *next_insn,
bool *dead_end)
{
+ /* prev_state is not used if there is no disassembly support */
+ struct insn_state prev_state __maybe_unused;
struct alternative *alt;
u8 visited;
int ret;
@@ -3785,7 +3787,11 @@ static int validate_insn(struct objtool_file *file, struct symbol *func,
if (skip_alt_group(insn))
return 0;
- if (handle_insn_ops(insn, next_insn, statep))
+ prev_state = *statep;
+ ret = handle_insn_ops(insn, next_insn, statep);
+ TRACE_INSN_STATE(insn, &prev_state, statep);
+
+ if (ret)
return 1;
switch (insn->type) {
diff --git a/tools/objtool/include/objtool/trace.h b/tools/objtool/include/objtool/trace.h
index 3f3c830..33fe9c6 100644
--- a/tools/objtool/include/objtool/trace.h
+++ b/tools/objtool/include/objtool/trace.h
@@ -30,6 +30,12 @@ extern int trace_depth;
} \
})
+#define TRACE_INSN_STATE(insn, sprev, snext) \
+({ \
+ if (trace) \
+ trace_insn_state(insn, sprev, snext); \
+})
+
static inline void trace_enable(void)
{
trace = true;
@@ -53,10 +59,14 @@ static inline void trace_depth_dec(void)
trace_depth--;
}
+void trace_insn_state(struct instruction *insn, struct insn_state *sprev,
+ struct insn_state *snext);
+
#else /* DISAS */
#define TRACE(fmt, ...) ({})
#define TRACE_INSN(insn, fmt, ...) ({})
+#define TRACE_INSN_STATE(insn, sprev, snext) ({})
static inline void trace_enable(void) {}
static inline void trace_disable(void) {}
diff --git a/tools/objtool/trace.c b/tools/objtool/trace.c
index 134cc33..12bbad0 100644
--- a/tools/objtool/trace.c
+++ b/tools/objtool/trace.c
@@ -7,3 +7,135 @@
bool trace;
int trace_depth;
+
+/*
+ * Macros to trace CFI state attributes changes.
+ */
+
+#define TRACE_CFI_ATTR(attr, prev, next, fmt, ...) \
+({ \
+ if ((prev)->attr != (next)->attr) \
+ TRACE("%s=" fmt " ", #attr, __VA_ARGS__); \
+})
+
+#define TRACE_CFI_ATTR_BOOL(attr, prev, next) \
+ TRACE_CFI_ATTR(attr, prev, next, \
+ "%s", (next)->attr ? "true" : "false")
+
+#define TRACE_CFI_ATTR_NUM(attr, prev, next, fmt) \
+ TRACE_CFI_ATTR(attr, prev, next, fmt, (next)->attr)
+
+#define CFI_REG_NAME_MAXLEN 16
+
+/*
+ * Return the name of a register. Note that the same static buffer
+ * is returned if the name is dynamically generated.
+ */
+static const char *cfi_reg_name(unsigned int reg)
+{
+ static char rname_buffer[CFI_REG_NAME_MAXLEN];
+
+ switch (reg) {
+ case CFI_UNDEFINED:
+ return "<undefined>";
+ case CFI_CFA:
+ return "cfa";
+ case CFI_SP_INDIRECT:
+ return "(sp)";
+ case CFI_BP_INDIRECT:
+ return "(bp)";
+ }
+
+ if (snprintf(rname_buffer, CFI_REG_NAME_MAXLEN, "r%d", reg) == -1)
+ return "<error>";
+
+ return (const char *)rname_buffer;
+}
+
+/*
+ * Functions and macros to trace CFI registers changes.
+ */
+
+static void trace_cfi_reg(const char *prefix, int reg, const char *fmt,
+ int base_prev, int offset_prev,
+ int base_next, int offset_next)
+{
+ char *rname;
+
+ if (base_prev == base_next && offset_prev == offset_next)
+ return;
+
+ if (prefix)
+ TRACE("%s:", prefix);
+
+ if (base_next == CFI_UNDEFINED) {
+ TRACE("%1$s=<undef> ", cfi_reg_name(reg));
+ } else {
+ rname = strdup(cfi_reg_name(reg));
+ TRACE(fmt, rname, cfi_reg_name(base_next), offset_next);
+ free(rname);
+ }
+}
+
+static void trace_cfi_reg_val(const char *prefix, int reg,
+ int base_prev, int offset_prev,
+ int base_next, int offset_next)
+{
+ trace_cfi_reg(prefix, reg, "%1$s=%2$s%3$+d ",
+ base_prev, offset_prev, base_next, offset_next);
+}
+
+static void trace_cfi_reg_ref(const char *prefix, int reg,
+ int base_prev, int offset_prev,
+ int base_next, int offset_next)
+{
+ trace_cfi_reg(prefix, reg, "%1$s=(%2$s%3$+d) ",
+ base_prev, offset_prev, base_next, offset_next);
+}
+
+#define TRACE_CFI_REG_VAL(reg, prev, next) \
+ trace_cfi_reg_val(NULL, reg, prev.base, prev.offset, \
+ next.base, next.offset)
+
+#define TRACE_CFI_REG_REF(reg, prev, next) \
+ trace_cfi_reg_ref(NULL, reg, prev.base, prev.offset, \
+ next.base, next.offset)
+
+void trace_insn_state(struct instruction *insn, struct insn_state *sprev,
+ struct insn_state *snext)
+{
+ struct cfi_state *cprev, *cnext;
+ int i;
+
+ if (!memcmp(sprev, snext, sizeof(struct insn_state)))
+ return;
+
+ cprev = &sprev->cfi;
+ cnext = &snext->cfi;
+
+ disas_print_insn(stderr, objtool_disas_ctx, insn,
+ trace_depth - 1, "state: ");
+
+ /* print registers changes */
+ TRACE_CFI_REG_VAL(CFI_CFA, cprev->cfa, cnext->cfa);
+ for (i = 0; i < CFI_NUM_REGS; i++) {
+ TRACE_CFI_REG_VAL(i, cprev->vals[i], cnext->vals[i]);
+ TRACE_CFI_REG_REF(i, cprev->regs[i], cnext->regs[i]);
+ }
+
+ /* print attributes changes */
+ TRACE_CFI_ATTR_NUM(stack_size, cprev, cnext, "%d");
+ TRACE_CFI_ATTR_BOOL(drap, cprev, cnext);
+ if (cnext->drap) {
+ trace_cfi_reg_val("drap", cnext->drap_reg,
+ cprev->drap_reg, cprev->drap_offset,
+ cnext->drap_reg, cnext->drap_offset);
+ }
+ TRACE_CFI_ATTR_BOOL(bp_scratch, cprev, cnext);
+ TRACE_CFI_ATTR_NUM(instr, sprev, snext, "%d");
+ TRACE_CFI_ATTR_NUM(uaccess_stack, sprev, snext, "%u");
+
+ TRACE("\n");
+
+ insn->trace = 1;
+}