Add an implementation of addr2line that uses libdw. Other addr2line
implementations are slow, particularly in the case of forking
addr2line. Add an implementation that caches the libdw information in
the dso and uses it to find the file and line number
information. Inline information is supported but because
cu_walk_functions_at visits the leaf function last add a
inline_list__append_tail to reverse the lists order.
Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/util/Build | 1 +
tools/perf/util/dso.c | 2 +
tools/perf/util/dso.h | 11 +++
tools/perf/util/libdw.c | 153 ++++++++++++++++++++++++++++++++++++++
tools/perf/util/libdw.h | 60 +++++++++++++++
tools/perf/util/srcline.c | 24 ++++++
tools/perf/util/srcline.h | 1 +
7 files changed, 252 insertions(+)
create mode 100644 tools/perf/util/libdw.c
create mode 100644 tools/perf/util/libdw.h
diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index 1c2a43e1dc68..2bed6274e248 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -224,6 +224,7 @@ perf-util-$(CONFIG_LIBDW) += dwarf-regs-powerpc.o
perf-util-$(CONFIG_LIBDW) += dwarf-regs-x86.o
perf-util-$(CONFIG_LIBDW) += debuginfo.o
perf-util-$(CONFIG_LIBDW) += annotate-data.o
+perf-util-$(CONFIG_LIBDW) += libdw.o
perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
perf-util-$(CONFIG_LOCAL_LIBUNWIND) += unwind-libunwind-local.o
diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 344e689567ee..06980844c014 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -32,6 +32,7 @@
#include "string2.h"
#include "vdso.h"
#include "annotate-data.h"
+#include "libdw.h"
static const char * const debuglink_paths[] = {
"%.0s%s",
@@ -1605,6 +1606,7 @@ void dso__delete(struct dso *dso)
auxtrace_cache__free(RC_CHK_ACCESS(dso)->auxtrace_cache);
dso_cache__free(dso);
dso__free_a2l(dso);
+ dso__free_a2l_libdw(dso);
dso__free_symsrc_filename(dso);
nsinfo__zput(RC_CHK_ACCESS(dso)->nsinfo);
mutex_destroy(dso__lock(dso));
diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index f8ccb9816b89..4aee23775054 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -268,6 +268,7 @@ DECLARE_RC_STRUCT(dso) {
const char *short_name;
const char *long_name;
void *a2l;
+ void *a2l_libdw;
char *symsrc_filename;
#if defined(__powerpc__)
void *dwfl; /* DWARF debug info */
@@ -334,6 +335,16 @@ static inline void dso__set_a2l(struct dso *dso, void *val)
RC_CHK_ACCESS(dso)->a2l = val;
}
+static inline void *dso__a2l_libdw(const struct dso *dso)
+{
+ return RC_CHK_ACCESS(dso)->a2l_libdw;
+}
+
+static inline void dso__set_a2l_libdw(struct dso *dso, void *val)
+{
+ RC_CHK_ACCESS(dso)->a2l_libdw = val;
+}
+
static inline unsigned int dso__a2l_fails(const struct dso *dso)
{
return RC_CHK_ACCESS(dso)->a2l_fails;
diff --git a/tools/perf/util/libdw.c b/tools/perf/util/libdw.c
new file mode 100644
index 000000000000..e4bfd52bd172
--- /dev/null
+++ b/tools/perf/util/libdw.c
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "dso.h"
+#include "libdw.h"
+#include "srcline.h"
+#include "symbol.h"
+#include "dwarf-aux.h"
+#include <fcntl.h>
+#include <unistd.h>
+#include <elfutils/libdwfl.h>
+
+void dso__free_a2l_libdw(struct dso *dso)
+{
+ Dwfl *dwfl = dso__a2l_libdw(dso);
+
+ if (dwfl) {
+ dwfl_end(dwfl);
+ dso__set_a2l_libdw(dso, NULL);
+ }
+}
+
+struct libdw_a2l_cb_args {
+ struct dso *dso;
+ struct symbol *sym;
+ struct inline_node *node;
+ char *leaf_srcline;
+ bool leaf_srcline_used;
+};
+
+static int libdw_a2l_cb(Dwarf_Die *die, void *_args)
+{
+ struct libdw_a2l_cb_args *args = _args;
+ struct symbol *inline_sym = new_inline_sym(args->dso, args->sym, dwarf_diename(die));
+ const char *call_fname = die_get_call_file(die);
+ char *call_srcline = srcline__unknown;
+ struct inline_list *ilist;
+
+ if (!inline_sym)
+ return -ENOMEM;
+
+ /* Assign caller information to the parent. */
+ if (call_fname)
+ call_srcline = srcline_from_fileline(call_fname, die_get_call_lineno(die));
+
+ list_for_each_entry(ilist, &args->node->val, list) {
+ ilist->srcline = call_srcline;
+ call_srcline = NULL;
+ break;
+ }
+ if (call_srcline && call_fname)
+ free(call_srcline);
+
+ /* Add this symbol to the chain as the leaf. */
+ inline_list__append_tail(inline_sym, args->leaf_srcline, args->node);
+ args->leaf_srcline_used = true;
+ return 0;
+}
+
+int libdw__addr2line(const char *dso_name, u64 addr,
+ char **file, unsigned int *line_nr,
+ struct dso *dso, bool unwind_inlines,
+ struct inline_node *node, struct symbol *sym)
+{
+ static const Dwfl_Callbacks offline_callbacks = {
+ .find_debuginfo = dwfl_standard_find_debuginfo,
+ .section_address = dwfl_offline_section_address,
+ .find_elf = dwfl_build_id_find_elf,
+ };
+ Dwfl *dwfl = dso__a2l_libdw(dso);
+ Dwfl_Module *mod;
+ Dwfl_Line *dwline;
+ Dwarf_Addr bias;
+ const char *src;
+ int lineno = 0;
+
+ if (!dwfl) {
+ /*
+ * Initialize Dwfl session.
+ * We need to open the DSO file to report it to libdw.
+ */
+ int fd;
+
+ fd = open(dso_name, O_RDONLY);
+ if (fd < 0)
+ return 0;
+
+ dwfl = dwfl_begin(&offline_callbacks);
+ if (!dwfl) {
+ close(fd);
+ return 0;
+ }
+
+ /*
+ * If the report is successful, the file descriptor fd is consumed
+ * and closed by the Dwfl. If not, it is not closed.
+ */
+ mod = dwfl_report_offline(dwfl, dso_name, dso_name, fd);
+ if (!mod) {
+ dwfl_end(dwfl);
+ close(fd);
+ return 0;
+ }
+
+ dwfl_report_end(dwfl, /*removed=*/NULL, /*arg=*/NULL);
+ dso__set_a2l_libdw(dso, dwfl);
+ } else {
+ /* Dwfl session already initialized, get module for address. */
+ mod = dwfl_addrmodule(dwfl, addr);
+ }
+
+ if (!mod)
+ return 0;
+
+ /*
+ * Get/ignore the dwarf information. Determine the bias, difference
+ * between the regular ELF addr2line addresses and those to use with
+ * libdw.
+ */
+ if (!dwfl_module_getdwarf(mod, &bias))
+ return 0;
+
+ /* Find source line information for the address. */
+ dwline = dwfl_module_getsrc(mod, addr + bias);
+ if (!dwline)
+ return 0;
+
+ /* Get line information. */
+ src = dwfl_lineinfo(dwline, /*addr=*/NULL, &lineno, /*col=*/NULL, /*mtime=*/NULL,
+ /*length=*/NULL);
+
+ if (file)
+ *file = src ? strdup(src) : NULL;
+ if (line_nr)
+ *line_nr = lineno;
+
+ /* Optionally unwind inline function call chain. */
+ if (unwind_inlines && node) {
+ Dwarf_Addr unused_bias;
+ Dwarf_Die *cudie = dwfl_module_addrdie(mod, addr + bias, &unused_bias);
+ struct libdw_a2l_cb_args args = {
+ .dso = dso,
+ .sym = sym,
+ .node = node,
+ .leaf_srcline = srcline_from_fileline(src ?: "<unknown>", lineno),
+ };
+
+ /* Walk from the parent down to the leaf. */
+ cu_walk_functions_at(cudie, addr, libdw_a2l_cb, &args);
+
+ if (!args.leaf_srcline_used)
+ free(args.leaf_srcline);
+ }
+ return 1;
+}
diff --git a/tools/perf/util/libdw.h b/tools/perf/util/libdw.h
new file mode 100644
index 000000000000..0f8d7b4a11a5
--- /dev/null
+++ b/tools/perf/util/libdw.h
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef PERF_LIBDW_H
+#define PERF_LIBDW_H
+
+#include <linux/types.h>
+
+struct dso;
+struct inline_node;
+struct symbol;
+
+#ifdef HAVE_LIBDW_SUPPORT
+/*
+ * libdw__addr2line - Convert address to source location using libdw
+ * @dso_name: Name of the DSO
+ * @addr: Address to resolve
+ * @file: Pointer to return filename (caller must free)
+ * @line_nr: Pointer to return line number
+ * @dso: The dso struct
+ * @unwind_inlines: Whether to unwind inline function calls
+ * @node: Inline node list to append to
+ * @sym: The symbol associated with the address
+ *
+ * This function initializes a Dwfl context for the DSO if not already present,
+ * finds the source line information for the given address, and optionally
+ * resolves inline function call chains.
+ *
+ * Returns 1 on success (found), 0 on failure (not found).
+ */
+int libdw__addr2line(const char *dso_name, u64 addr, char **file,
+ unsigned int *line_nr, struct dso *dso,
+ bool unwind_inlines, struct inline_node *node,
+ struct symbol *sym);
+
+/*
+ * dso__free_a2l_libdw - Free libdw resources associated with the DSO
+ * @dso: The dso to free resources for
+ *
+ * This function cleans up the Dwfl context used for addr2line lookups.
+ */
+void dso__free_a2l_libdw(struct dso *dso);
+
+#else /* HAVE_LIBDW_SUPPORT */
+
+static inline int libdw__addr2line(const char *dso_name __maybe_unused,
+ u64 addr __maybe_unused, char **file __maybe_unused,
+ unsigned int *line_nr __maybe_unused,
+ struct dso *dso __maybe_unused,
+ bool unwind_inlines __maybe_unused,
+ struct inline_node *node __maybe_unused,
+ struct symbol *sym __maybe_unused)
+{
+ return 0;
+}
+
+static inline void dso__free_a2l_libdw(struct dso *dso __maybe_unused)
+{
+}
+#endif /* HAVE_LIBDW_SUPPORT */
+
+#endif /* PERF_LIBDW_H */
diff --git a/tools/perf/util/srcline.c b/tools/perf/util/srcline.c
index 27c0966611ab..e2d280678b02 100644
--- a/tools/perf/util/srcline.c
+++ b/tools/perf/util/srcline.c
@@ -6,6 +6,7 @@
#include "libbfd.h"
#include "llvm.h"
#include "symbol.h"
+#include "libdw.h"
#include <inttypes.h>
#include <string.h>
@@ -51,6 +52,25 @@ int inline_list__append(struct symbol *symbol, char *srcline, struct inline_node
return 0;
}
+int inline_list__append_tail(struct symbol *symbol, char *srcline, struct inline_node *node)
+{
+ struct inline_list *ilist;
+
+ ilist = zalloc(sizeof(*ilist));
+ if (ilist == NULL)
+ return -1;
+
+ ilist->symbol = symbol;
+ ilist->srcline = srcline;
+
+ if (callchain_param.order == ORDER_CALLEE)
+ list_add(&ilist->list, &node->val);
+ else
+ list_add_tail(&ilist->list, &node->val);
+
+ return 0;
+}
+
/* basename version that takes a const input string */
static const char *gnu_basename(const char *path)
{
@@ -120,6 +140,10 @@ static int addr2line(const char *dso_name, u64 addr, char **file, unsigned int *
{
int ret;
+ ret = libdw__addr2line(dso_name, addr, file, line_nr, dso, unwind_inlines, node, sym);
+ if (ret > 0)
+ return ret;
+
ret = llvm__addr2line(dso_name, addr, file, line_nr, dso, unwind_inlines, node, sym);
if (ret > 0)
return ret;
diff --git a/tools/perf/util/srcline.h b/tools/perf/util/srcline.h
index c36f573cd339..be9f002bf234 100644
--- a/tools/perf/util/srcline.h
+++ b/tools/perf/util/srcline.h
@@ -57,6 +57,7 @@ struct inline_node *inlines__tree_find(struct rb_root_cached *tree, u64 addr);
void inlines__tree_delete(struct rb_root_cached *tree);
int inline_list__append(struct symbol *symbol, char *srcline, struct inline_node *node);
+int inline_list__append_tail(struct symbol *symbol, char *srcline, struct inline_node *node);
char *srcline_from_fileline(const char *file, unsigned int line);
struct symbol *new_inline_sym(struct dso *dso,
struct symbol *base_sym,
--
2.52.0.457.g6b5491de43-googOn Sat, Jan 10, 2026 at 08:13:33PM -0800, Ian Rogers wrote:
> Add an implementation of addr2line that uses libdw. Other addr2line
> implementations are slow, particularly in the case of forking
> addr2line. Add an implementation that caches the libdw information in
> the dso and uses it to find the file and line number
> information. Inline information is supported but because
> cu_walk_functions_at visits the leaf function last add a
> inline_list__append_tail to reverse the lists order.
So while testing I moved the inlineloop 'perf test' workload to the
front to test without this new libdw implementation and then with it,
and tested using perf probe on it:
root@number:/home/acme# perf probe -x ~/bin/perf libdw__addr2line%return 'ret=$retval'
Added new event:
probe_perf:libdw_addr2line__return (on libdw__addr2line%return in /home/acme/bin/perf with ret=$retval)
You can now use it in all perf tools, such as:
perf record -e probe_perf:libdw_addr2line__return -aR sleep 1
root@number:/home/acme# perf trace -e probe_perf:libdw_addr2line__return perf report -f --dso perf --stdio -s srcfile,srcline
0.000 :1204769/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
0.007 :1204769/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.680 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.685 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.689 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.692 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.696 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.699 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.702 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.705 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.709 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.712 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.715 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.718 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.721 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.724 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.727 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.729 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.732 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.734 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.737 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.740 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
0.771 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
13.563 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
13.766 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
14.099 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
14.103 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.105 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.134 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.143 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.242 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.244 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.245 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.246 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.248 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.250 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.251 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.252 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.258 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.260 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.265 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.267 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.268 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
14.270 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
# To display the perf.data header info, please use --header/--header-only options.
#
#
# Total Lost Samples: 0
#
# Samples: 4K of event 'cpu/cycles/Pu'
# Event count (approx.): 5535180842
#
# Overhead Source File Source:Line
# ........ ............ ...............
#
99.04% inlineloop.c inlineloop.c:21
0.46% inlineloop.c inlineloop.c:20
#
# (Tip: Save output of perf stat using: perf stat record <target workload>)
#
root@number:/home/acme#
Putting more probes to see the fallbacks...
root@number:/home/acme# perf probe -l
probe_perf:cmd_addr2line (on cmd__addr2line@util/addr2line.c in /home/acme/bin/perf)
probe_perf:libbfd_addr2line (on libbfd__addr2line@util/libbfd.h in /home/acme/bin/perf)
probe_perf:libdw_addr2line (on libdw__addr2line@util/libdw.c in /home/acme/bin/perf)
probe_perf:llvm_addr2line (on llvm__addr2line@util/llvm.c in /home/acme/bin/perf)
probe_perf:libdw_addr2line__return (on libdw__addr2line%return@util/libdw.c in /home/acme/bin/perf with ret)
root@number:/home/acme#
As we have:
static int addr2line(const char *dso_name, u64 addr, char **file, unsigned int *line_nr,
struct dso *dso, bool unwind_inlines, struct inline_node *node,
struct symbol *sym)
{
int ret;
ret = libdw__addr2line(dso_name, addr, file, line_nr, dso, unwind_inlines, node, sym);
if (ret > 0)
return ret;
ret = llvm__addr2line(dso_name, addr, file, line_nr, dso, unwind_inlines, node, sym);
if (ret > 0)
return ret;
ret = libbfd__addr2line(dso_name, addr, file, line_nr, dso, unwind_inlines, node, sym);
if (ret > 0)
return ret;
return cmd__addr2line(dso_name, addr, file, line_nr, dso, unwind_inlines, node, sym);
}
root@number:/home/acme# perf stat -e probe_perf:*_addr2line perf report -f --dso perf --stdio -s srcfile,srcline
# To display the perf.data header info, please use --header/--header-only options.
#
#
# Total Lost Samples: 0
#
# Samples: 4K of event 'cpu/cycles/Pu'
# Event count (approx.): 5535180842
#
# Overhead Source File Source:Line
# ........ ............ ...............
#
99.04% inlineloop.c inlineloop.c:21
0.46% inlineloop.c inlineloop.c:20
#
# (Tip: To set sampling period of individual events use perf record -e cpu/cpu-cycles,period=100001/,cpu/branches,period=10001/ ...)
#
Performance counter stats for 'perf report -f --dso perf --stdio -s srcfile,srcline':
44 probe_perf:libdw_addr2line
23 probe_perf:llvm_addr2line
0 probe_perf:libbfd_addr2line
0 probe_perf:cmd_addr2line
0.036554827 seconds time elapsed
0.030570000 seconds user
0.006049000 seconds sys
root@number:/home/acme#
Maybe asking for the dso_name may help understand why it is falling back
23 times to the llvm based one...
root@number:/home/acme# perf probe -x ~/bin/perf llvm__addr2line dso_name:string
Target program is compiled without optimization. Skipping prologue.
Probe on address 0x5f73e4 to force probing at the function entry.
Added new event:
probe_perf:llvm_addr2line (on llvm__addr2line in /home/acme/bin/perf with dso_name:string)
You can now use it in all perf tools, such as:
perf record -e probe_perf:llvm_addr2line -aR sleep 1
root@number:/home/acme# perf trace --libtrace -e probe_perf:llvm_addr2line perf report -f --dso perf --stdio -s srcfile,srcline
0.000 perf/1205478 probe_perf:llvm_addr2line((5f7416) dso_name_string="/root/.debug/.build-id/cc/315df11334de01fb444465f08f6bca45a12bd2/elf")
0.697 perf/1205478 probe_perf:llvm_addr2line((5f7416) dso_name_string="/root/.debug/.build-id/cc/315df11334de01fb444465f08f6bca45a12bd2/elf")
0.704 perf/1205478 probe_perf:llvm_addr2line((5f7416) dso_name_string="/root/.debug/.build-id/cc/315df11334de01fb444465f08f6bca45a12bd2/elf")
0.708 perf/1205478 probe_perf:llvm_addr2line((5f7416) dso_name_string="/root/.debug/.build-id/cc/315df11334de01fb444465f08f6bca45a12bd2/elf")
0.712 perf/1205478 probe_perf:llvm_addr2line((5f7416) dso_name_string="/root/.debug/.build-id/cc/315df11334de01fb444465f08f6bca45a12bd2/elf")
<SNIP>
root@number:/home/acme# readelf -wi /root/.debug/.build-id/cc/315df11334de01fb444465f08f6bca45a12bd2/elf | head -30
Contents of the .debug_info section:
Compilation Unit @ offset 0:
Length: 0x20 (32-bit)
Version: 5
Unit Type: DW_UT_partial (3)
Abbrev Offset: 0xad87
Pointer Size: 8
<0><c>: Abbrev Number: 38 (DW_TAG_partial_unit)
<d> DW_AT_stmt_list : 0
<11> DW_AT_comp_dir : (indirect line string, offset: 0xc9c): /usr/src/debug/glibc-2.42-5.fc43.x86_64/elf
<1><15>: Abbrev Number: 57 (DW_TAG_base_type)
<16> DW_AT_byte_size : 8
<17> DW_AT_encoding : 7 (unsigned)
<18> DW_AT_name : (indirect string, offset: 0x9bf1): long unsigned int
<1><1c>: Abbrev Number: 57 (DW_TAG_base_type)
<1d> DW_AT_byte_size : 1
<1e> DW_AT_encoding : 6 (signed char)
<1f> DW_AT_name : (indirect string, offset: 0x7bab): char
<1><23>: Abbrev Number: 0
Compilation Unit @ offset 0x24:
Length: 0x20 (32-bit)
Version: 5
Unit Type: DW_UT_partial (3)
Abbrev Offset: 0xad87
Pointer Size: 8
<0><30>: Abbrev Number: 38 (DW_TAG_partial_unit)
<31> DW_AT_stmt_list : 0
<35> DW_AT_comp_dir : (indirect line string, offset: 0xc9c): /usr/src/debug/glibc-2.42-5.fc43.x86_64/elf
<1><39>: Abbrev Number: 57 (DW_TAG_base_type)
root@number:/home/acme#
Some partial unit glibc DWARF 5. I think we need some more libdw setup
to handle those?
But then we can merge what James already reviewed and go on from here,
right?
- Arnaldo
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
> tools/perf/util/Build | 1 +
> tools/perf/util/dso.c | 2 +
> tools/perf/util/dso.h | 11 +++
> tools/perf/util/libdw.c | 153 ++++++++++++++++++++++++++++++++++++++
> tools/perf/util/libdw.h | 60 +++++++++++++++
> tools/perf/util/srcline.c | 24 ++++++
> tools/perf/util/srcline.h | 1 +
> 7 files changed, 252 insertions(+)
> create mode 100644 tools/perf/util/libdw.c
> create mode 100644 tools/perf/util/libdw.h
>
> diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> index 1c2a43e1dc68..2bed6274e248 100644
> --- a/tools/perf/util/Build
> +++ b/tools/perf/util/Build
> @@ -224,6 +224,7 @@ perf-util-$(CONFIG_LIBDW) += dwarf-regs-powerpc.o
> perf-util-$(CONFIG_LIBDW) += dwarf-regs-x86.o
> perf-util-$(CONFIG_LIBDW) += debuginfo.o
> perf-util-$(CONFIG_LIBDW) += annotate-data.o
> +perf-util-$(CONFIG_LIBDW) += libdw.o
>
> perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
> perf-util-$(CONFIG_LOCAL_LIBUNWIND) += unwind-libunwind-local.o
> diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
> index 344e689567ee..06980844c014 100644
> --- a/tools/perf/util/dso.c
> +++ b/tools/perf/util/dso.c
> @@ -32,6 +32,7 @@
> #include "string2.h"
> #include "vdso.h"
> #include "annotate-data.h"
> +#include "libdw.h"
>
> static const char * const debuglink_paths[] = {
> "%.0s%s",
> @@ -1605,6 +1606,7 @@ void dso__delete(struct dso *dso)
> auxtrace_cache__free(RC_CHK_ACCESS(dso)->auxtrace_cache);
> dso_cache__free(dso);
> dso__free_a2l(dso);
> + dso__free_a2l_libdw(dso);
> dso__free_symsrc_filename(dso);
> nsinfo__zput(RC_CHK_ACCESS(dso)->nsinfo);
> mutex_destroy(dso__lock(dso));
> diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
> index f8ccb9816b89..4aee23775054 100644
> --- a/tools/perf/util/dso.h
> +++ b/tools/perf/util/dso.h
> @@ -268,6 +268,7 @@ DECLARE_RC_STRUCT(dso) {
> const char *short_name;
> const char *long_name;
> void *a2l;
> + void *a2l_libdw;
> char *symsrc_filename;
> #if defined(__powerpc__)
> void *dwfl; /* DWARF debug info */
> @@ -334,6 +335,16 @@ static inline void dso__set_a2l(struct dso *dso, void *val)
> RC_CHK_ACCESS(dso)->a2l = val;
> }
>
> +static inline void *dso__a2l_libdw(const struct dso *dso)
> +{
> + return RC_CHK_ACCESS(dso)->a2l_libdw;
> +}
> +
> +static inline void dso__set_a2l_libdw(struct dso *dso, void *val)
> +{
> + RC_CHK_ACCESS(dso)->a2l_libdw = val;
> +}
> +
> static inline unsigned int dso__a2l_fails(const struct dso *dso)
> {
> return RC_CHK_ACCESS(dso)->a2l_fails;
> diff --git a/tools/perf/util/libdw.c b/tools/perf/util/libdw.c
> new file mode 100644
> index 000000000000..e4bfd52bd172
> --- /dev/null
> +++ b/tools/perf/util/libdw.c
> @@ -0,0 +1,153 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include "dso.h"
> +#include "libdw.h"
> +#include "srcline.h"
> +#include "symbol.h"
> +#include "dwarf-aux.h"
> +#include <fcntl.h>
> +#include <unistd.h>
> +#include <elfutils/libdwfl.h>
> +
> +void dso__free_a2l_libdw(struct dso *dso)
> +{
> + Dwfl *dwfl = dso__a2l_libdw(dso);
> +
> + if (dwfl) {
> + dwfl_end(dwfl);
> + dso__set_a2l_libdw(dso, NULL);
> + }
> +}
> +
> +struct libdw_a2l_cb_args {
> + struct dso *dso;
> + struct symbol *sym;
> + struct inline_node *node;
> + char *leaf_srcline;
> + bool leaf_srcline_used;
> +};
> +
> +static int libdw_a2l_cb(Dwarf_Die *die, void *_args)
> +{
> + struct libdw_a2l_cb_args *args = _args;
> + struct symbol *inline_sym = new_inline_sym(args->dso, args->sym, dwarf_diename(die));
> + const char *call_fname = die_get_call_file(die);
> + char *call_srcline = srcline__unknown;
> + struct inline_list *ilist;
> +
> + if (!inline_sym)
> + return -ENOMEM;
> +
> + /* Assign caller information to the parent. */
> + if (call_fname)
> + call_srcline = srcline_from_fileline(call_fname, die_get_call_lineno(die));
> +
> + list_for_each_entry(ilist, &args->node->val, list) {
> + ilist->srcline = call_srcline;
> + call_srcline = NULL;
> + break;
> + }
> + if (call_srcline && call_fname)
> + free(call_srcline);
> +
> + /* Add this symbol to the chain as the leaf. */
> + inline_list__append_tail(inline_sym, args->leaf_srcline, args->node);
> + args->leaf_srcline_used = true;
> + return 0;
> +}
> +
> +int libdw__addr2line(const char *dso_name, u64 addr,
> + char **file, unsigned int *line_nr,
> + struct dso *dso, bool unwind_inlines,
> + struct inline_node *node, struct symbol *sym)
> +{
> + static const Dwfl_Callbacks offline_callbacks = {
> + .find_debuginfo = dwfl_standard_find_debuginfo,
> + .section_address = dwfl_offline_section_address,
> + .find_elf = dwfl_build_id_find_elf,
> + };
> + Dwfl *dwfl = dso__a2l_libdw(dso);
> + Dwfl_Module *mod;
> + Dwfl_Line *dwline;
> + Dwarf_Addr bias;
> + const char *src;
> + int lineno = 0;
> +
> + if (!dwfl) {
> + /*
> + * Initialize Dwfl session.
> + * We need to open the DSO file to report it to libdw.
> + */
> + int fd;
> +
> + fd = open(dso_name, O_RDONLY);
> + if (fd < 0)
> + return 0;
> +
> + dwfl = dwfl_begin(&offline_callbacks);
> + if (!dwfl) {
> + close(fd);
> + return 0;
> + }
> +
> + /*
> + * If the report is successful, the file descriptor fd is consumed
> + * and closed by the Dwfl. If not, it is not closed.
> + */
> + mod = dwfl_report_offline(dwfl, dso_name, dso_name, fd);
> + if (!mod) {
> + dwfl_end(dwfl);
> + close(fd);
> + return 0;
> + }
> +
> + dwfl_report_end(dwfl, /*removed=*/NULL, /*arg=*/NULL);
> + dso__set_a2l_libdw(dso, dwfl);
> + } else {
> + /* Dwfl session already initialized, get module for address. */
> + mod = dwfl_addrmodule(dwfl, addr);
> + }
> +
> + if (!mod)
> + return 0;
> +
> + /*
> + * Get/ignore the dwarf information. Determine the bias, difference
> + * between the regular ELF addr2line addresses and those to use with
> + * libdw.
> + */
> + if (!dwfl_module_getdwarf(mod, &bias))
> + return 0;
> +
> + /* Find source line information for the address. */
> + dwline = dwfl_module_getsrc(mod, addr + bias);
> + if (!dwline)
> + return 0;
> +
> + /* Get line information. */
> + src = dwfl_lineinfo(dwline, /*addr=*/NULL, &lineno, /*col=*/NULL, /*mtime=*/NULL,
> + /*length=*/NULL);
> +
> + if (file)
> + *file = src ? strdup(src) : NULL;
> + if (line_nr)
> + *line_nr = lineno;
> +
> + /* Optionally unwind inline function call chain. */
> + if (unwind_inlines && node) {
> + Dwarf_Addr unused_bias;
> + Dwarf_Die *cudie = dwfl_module_addrdie(mod, addr + bias, &unused_bias);
> + struct libdw_a2l_cb_args args = {
> + .dso = dso,
> + .sym = sym,
> + .node = node,
> + .leaf_srcline = srcline_from_fileline(src ?: "<unknown>", lineno),
> + };
> +
> + /* Walk from the parent down to the leaf. */
> + cu_walk_functions_at(cudie, addr, libdw_a2l_cb, &args);
> +
> + if (!args.leaf_srcline_used)
> + free(args.leaf_srcline);
> + }
> + return 1;
> +}
> diff --git a/tools/perf/util/libdw.h b/tools/perf/util/libdw.h
> new file mode 100644
> index 000000000000..0f8d7b4a11a5
> --- /dev/null
> +++ b/tools/perf/util/libdw.h
> @@ -0,0 +1,60 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef PERF_LIBDW_H
> +#define PERF_LIBDW_H
> +
> +#include <linux/types.h>
> +
> +struct dso;
> +struct inline_node;
> +struct symbol;
> +
> +#ifdef HAVE_LIBDW_SUPPORT
> +/*
> + * libdw__addr2line - Convert address to source location using libdw
> + * @dso_name: Name of the DSO
> + * @addr: Address to resolve
> + * @file: Pointer to return filename (caller must free)
> + * @line_nr: Pointer to return line number
> + * @dso: The dso struct
> + * @unwind_inlines: Whether to unwind inline function calls
> + * @node: Inline node list to append to
> + * @sym: The symbol associated with the address
> + *
> + * This function initializes a Dwfl context for the DSO if not already present,
> + * finds the source line information for the given address, and optionally
> + * resolves inline function call chains.
> + *
> + * Returns 1 on success (found), 0 on failure (not found).
> + */
> +int libdw__addr2line(const char *dso_name, u64 addr, char **file,
> + unsigned int *line_nr, struct dso *dso,
> + bool unwind_inlines, struct inline_node *node,
> + struct symbol *sym);
> +
> +/*
> + * dso__free_a2l_libdw - Free libdw resources associated with the DSO
> + * @dso: The dso to free resources for
> + *
> + * This function cleans up the Dwfl context used for addr2line lookups.
> + */
> +void dso__free_a2l_libdw(struct dso *dso);
> +
> +#else /* HAVE_LIBDW_SUPPORT */
> +
> +static inline int libdw__addr2line(const char *dso_name __maybe_unused,
> + u64 addr __maybe_unused, char **file __maybe_unused,
> + unsigned int *line_nr __maybe_unused,
> + struct dso *dso __maybe_unused,
> + bool unwind_inlines __maybe_unused,
> + struct inline_node *node __maybe_unused,
> + struct symbol *sym __maybe_unused)
> +{
> + return 0;
> +}
> +
> +static inline void dso__free_a2l_libdw(struct dso *dso __maybe_unused)
> +{
> +}
> +#endif /* HAVE_LIBDW_SUPPORT */
> +
> +#endif /* PERF_LIBDW_H */
> diff --git a/tools/perf/util/srcline.c b/tools/perf/util/srcline.c
> index 27c0966611ab..e2d280678b02 100644
> --- a/tools/perf/util/srcline.c
> +++ b/tools/perf/util/srcline.c
> @@ -6,6 +6,7 @@
> #include "libbfd.h"
> #include "llvm.h"
> #include "symbol.h"
> +#include "libdw.h"
>
> #include <inttypes.h>
> #include <string.h>
> @@ -51,6 +52,25 @@ int inline_list__append(struct symbol *symbol, char *srcline, struct inline_node
> return 0;
> }
>
> +int inline_list__append_tail(struct symbol *symbol, char *srcline, struct inline_node *node)
> +{
> + struct inline_list *ilist;
> +
> + ilist = zalloc(sizeof(*ilist));
> + if (ilist == NULL)
> + return -1;
> +
> + ilist->symbol = symbol;
> + ilist->srcline = srcline;
> +
> + if (callchain_param.order == ORDER_CALLEE)
> + list_add(&ilist->list, &node->val);
> + else
> + list_add_tail(&ilist->list, &node->val);
> +
> + return 0;
> +}
> +
> /* basename version that takes a const input string */
> static const char *gnu_basename(const char *path)
> {
> @@ -120,6 +140,10 @@ static int addr2line(const char *dso_name, u64 addr, char **file, unsigned int *
> {
> int ret;
>
> + ret = libdw__addr2line(dso_name, addr, file, line_nr, dso, unwind_inlines, node, sym);
> + if (ret > 0)
> + return ret;
> +
> ret = llvm__addr2line(dso_name, addr, file, line_nr, dso, unwind_inlines, node, sym);
> if (ret > 0)
> return ret;
> diff --git a/tools/perf/util/srcline.h b/tools/perf/util/srcline.h
> index c36f573cd339..be9f002bf234 100644
> --- a/tools/perf/util/srcline.h
> +++ b/tools/perf/util/srcline.h
> @@ -57,6 +57,7 @@ struct inline_node *inlines__tree_find(struct rb_root_cached *tree, u64 addr);
> void inlines__tree_delete(struct rb_root_cached *tree);
>
> int inline_list__append(struct symbol *symbol, char *srcline, struct inline_node *node);
> +int inline_list__append_tail(struct symbol *symbol, char *srcline, struct inline_node *node);
> char *srcline_from_fileline(const char *file, unsigned int line);
> struct symbol *new_inline_sym(struct dso *dso,
> struct symbol *base_sym,
> --
> 2.52.0.457.g6b5491de43-goog
>
On Mon, Jan 12, 2026 at 11:52 AM Arnaldo Carvalho de Melo
<acme@kernel.org> wrote:
>
> On Sat, Jan 10, 2026 at 08:13:33PM -0800, Ian Rogers wrote:
> > Add an implementation of addr2line that uses libdw. Other addr2line
> > implementations are slow, particularly in the case of forking
> > addr2line. Add an implementation that caches the libdw information in
> > the dso and uses it to find the file and line number
> > information. Inline information is supported but because
> > cu_walk_functions_at visits the leaf function last add a
> > inline_list__append_tail to reverse the lists order.
>
> So while testing I moved the inlineloop 'perf test' workload to the
> front to test without this new libdw implementation and then with it,
> and tested using perf probe on it:
>
> root@number:/home/acme# perf probe -x ~/bin/perf libdw__addr2line%return 'ret=$retval'
> Added new event:
> probe_perf:libdw_addr2line__return (on libdw__addr2line%return in /home/acme/bin/perf with ret=$retval)
>
> You can now use it in all perf tools, such as:
>
> perf record -e probe_perf:libdw_addr2line__return -aR sleep 1
>
> root@number:/home/acme# perf trace -e probe_perf:libdw_addr2line__return perf report -f --dso perf --stdio -s srcfile,srcline
> 0.000 :1204769/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 0.007 :1204769/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.680 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.685 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.689 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.692 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.696 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.699 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.702 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.705 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.709 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.712 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.715 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.718 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.721 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.724 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.727 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.729 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.732 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.734 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.737 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.740 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 0.771 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 13.563 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 13.766 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 14.099 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548)
> 14.103 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.105 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.134 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.143 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.242 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.244 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.245 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.246 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.248 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.250 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.251 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.252 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.258 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.260 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.265 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.267 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.268 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> 14.270 perf/1204769 probe_perf:libdw_addr2line__return(__probe_func: 7698362, __probe_ret_ip: 7030548, ret: 1)
> # To display the perf.data header info, please use --header/--header-only options.
> #
> #
> # Total Lost Samples: 0
> #
> # Samples: 4K of event 'cpu/cycles/Pu'
> # Event count (approx.): 5535180842
> #
> # Overhead Source File Source:Line
> # ........ ............ ...............
> #
> 99.04% inlineloop.c inlineloop.c:21
> 0.46% inlineloop.c inlineloop.c:20
>
>
> #
> # (Tip: Save output of perf stat using: perf stat record <target workload>)
> #
> root@number:/home/acme#
>
> Putting more probes to see the fallbacks...
>
> root@number:/home/acme# perf probe -l
> probe_perf:cmd_addr2line (on cmd__addr2line@util/addr2line.c in /home/acme/bin/perf)
> probe_perf:libbfd_addr2line (on libbfd__addr2line@util/libbfd.h in /home/acme/bin/perf)
> probe_perf:libdw_addr2line (on libdw__addr2line@util/libdw.c in /home/acme/bin/perf)
> probe_perf:llvm_addr2line (on llvm__addr2line@util/llvm.c in /home/acme/bin/perf)
> probe_perf:libdw_addr2line__return (on libdw__addr2line%return@util/libdw.c in /home/acme/bin/perf with ret)
> root@number:/home/acme#
>
> As we have:
>
> static int addr2line(const char *dso_name, u64 addr, char **file, unsigned int *line_nr,
> struct dso *dso, bool unwind_inlines, struct inline_node *node,
> struct symbol *sym)
> {
> int ret;
>
> ret = libdw__addr2line(dso_name, addr, file, line_nr, dso, unwind_inlines, node, sym);
> if (ret > 0)
> return ret;
>
> ret = llvm__addr2line(dso_name, addr, file, line_nr, dso, unwind_inlines, node, sym);
> if (ret > 0)
> return ret;
>
> ret = libbfd__addr2line(dso_name, addr, file, line_nr, dso, unwind_inlines, node, sym);
> if (ret > 0)
> return ret;
>
> return cmd__addr2line(dso_name, addr, file, line_nr, dso, unwind_inlines, node, sym);
> }
>
> root@number:/home/acme# perf stat -e probe_perf:*_addr2line perf report -f --dso perf --stdio -s srcfile,srcline
> # To display the perf.data header info, please use --header/--header-only options.
> #
> #
> # Total Lost Samples: 0
> #
> # Samples: 4K of event 'cpu/cycles/Pu'
> # Event count (approx.): 5535180842
> #
> # Overhead Source File Source:Line
> # ........ ............ ...............
> #
> 99.04% inlineloop.c inlineloop.c:21
> 0.46% inlineloop.c inlineloop.c:20
>
>
> #
> # (Tip: To set sampling period of individual events use perf record -e cpu/cpu-cycles,period=100001/,cpu/branches,period=10001/ ...)
> #
>
> Performance counter stats for 'perf report -f --dso perf --stdio -s srcfile,srcline':
>
> 44 probe_perf:libdw_addr2line
> 23 probe_perf:llvm_addr2line
> 0 probe_perf:libbfd_addr2line
> 0 probe_perf:cmd_addr2line
>
> 0.036554827 seconds time elapsed
>
> 0.030570000 seconds user
> 0.006049000 seconds sys
>
>
> root@number:/home/acme#
>
> Maybe asking for the dso_name may help understand why it is falling back
> 23 times to the llvm based one...
>
> root@number:/home/acme# perf probe -x ~/bin/perf llvm__addr2line dso_name:string
> Target program is compiled without optimization. Skipping prologue.
> Probe on address 0x5f73e4 to force probing at the function entry.
>
> Added new event:
> probe_perf:llvm_addr2line (on llvm__addr2line in /home/acme/bin/perf with dso_name:string)
>
> You can now use it in all perf tools, such as:
>
> perf record -e probe_perf:llvm_addr2line -aR sleep 1
>
> root@number:/home/acme# perf trace --libtrace -e probe_perf:llvm_addr2line perf report -f --dso perf --stdio -s srcfile,srcline
> 0.000 perf/1205478 probe_perf:llvm_addr2line((5f7416) dso_name_string="/root/.debug/.build-id/cc/315df11334de01fb444465f08f6bca45a12bd2/elf")
> 0.697 perf/1205478 probe_perf:llvm_addr2line((5f7416) dso_name_string="/root/.debug/.build-id/cc/315df11334de01fb444465f08f6bca45a12bd2/elf")
> 0.704 perf/1205478 probe_perf:llvm_addr2line((5f7416) dso_name_string="/root/.debug/.build-id/cc/315df11334de01fb444465f08f6bca45a12bd2/elf")
> 0.708 perf/1205478 probe_perf:llvm_addr2line((5f7416) dso_name_string="/root/.debug/.build-id/cc/315df11334de01fb444465f08f6bca45a12bd2/elf")
> 0.712 perf/1205478 probe_perf:llvm_addr2line((5f7416) dso_name_string="/root/.debug/.build-id/cc/315df11334de01fb444465f08f6bca45a12bd2/elf")
> <SNIP>
>
> root@number:/home/acme# readelf -wi /root/.debug/.build-id/cc/315df11334de01fb444465f08f6bca45a12bd2/elf | head -30
> Contents of the .debug_info section:
>
> Compilation Unit @ offset 0:
> Length: 0x20 (32-bit)
> Version: 5
> Unit Type: DW_UT_partial (3)
> Abbrev Offset: 0xad87
> Pointer Size: 8
> <0><c>: Abbrev Number: 38 (DW_TAG_partial_unit)
> <d> DW_AT_stmt_list : 0
> <11> DW_AT_comp_dir : (indirect line string, offset: 0xc9c): /usr/src/debug/glibc-2.42-5.fc43.x86_64/elf
> <1><15>: Abbrev Number: 57 (DW_TAG_base_type)
> <16> DW_AT_byte_size : 8
> <17> DW_AT_encoding : 7 (unsigned)
> <18> DW_AT_name : (indirect string, offset: 0x9bf1): long unsigned int
> <1><1c>: Abbrev Number: 57 (DW_TAG_base_type)
> <1d> DW_AT_byte_size : 1
> <1e> DW_AT_encoding : 6 (signed char)
> <1f> DW_AT_name : (indirect string, offset: 0x7bab): char
> <1><23>: Abbrev Number: 0
> Compilation Unit @ offset 0x24:
> Length: 0x20 (32-bit)
> Version: 5
> Unit Type: DW_UT_partial (3)
> Abbrev Offset: 0xad87
> Pointer Size: 8
> <0><30>: Abbrev Number: 38 (DW_TAG_partial_unit)
> <31> DW_AT_stmt_list : 0
> <35> DW_AT_comp_dir : (indirect line string, offset: 0xc9c): /usr/src/debug/glibc-2.42-5.fc43.x86_64/elf
> <1><39>: Abbrev Number: 57 (DW_TAG_base_type)
> root@number:/home/acme#
>
> Some partial unit glibc DWARF 5. I think we need some more libdw setup
> to handle those?
Could be. Thanks for the analysis!
> But then we can merge what James already reviewed and go on from here,
> right?
+Masami Hiramatsu
I believe so. I'm not aware of anything outstanding on the patches -
v2 was using the function's declaration file:line rather than its
calling file:line, but that's all resolved in v3 and I'm not aware of
anything else left outstanding. Perhaps James can comment more on the
(non-blocking) issues he faced with LLVM and perhaps Masami can
comment on the libdw usage (I just checked that he did a lot of the
dwarf-aux.c work).
Thanks,
Ian
> - Arnaldo
>
> > Signed-off-by: Ian Rogers <irogers@google.com>
> > ---
> > tools/perf/util/Build | 1 +
> > tools/perf/util/dso.c | 2 +
> > tools/perf/util/dso.h | 11 +++
> > tools/perf/util/libdw.c | 153 ++++++++++++++++++++++++++++++++++++++
> > tools/perf/util/libdw.h | 60 +++++++++++++++
> > tools/perf/util/srcline.c | 24 ++++++
> > tools/perf/util/srcline.h | 1 +
> > 7 files changed, 252 insertions(+)
> > create mode 100644 tools/perf/util/libdw.c
> > create mode 100644 tools/perf/util/libdw.h
> >
> > diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> > index 1c2a43e1dc68..2bed6274e248 100644
> > --- a/tools/perf/util/Build
> > +++ b/tools/perf/util/Build
> > @@ -224,6 +224,7 @@ perf-util-$(CONFIG_LIBDW) += dwarf-regs-powerpc.o
> > perf-util-$(CONFIG_LIBDW) += dwarf-regs-x86.o
> > perf-util-$(CONFIG_LIBDW) += debuginfo.o
> > perf-util-$(CONFIG_LIBDW) += annotate-data.o
> > +perf-util-$(CONFIG_LIBDW) += libdw.o
> >
> > perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
> > perf-util-$(CONFIG_LOCAL_LIBUNWIND) += unwind-libunwind-local.o
> > diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
> > index 344e689567ee..06980844c014 100644
> > --- a/tools/perf/util/dso.c
> > +++ b/tools/perf/util/dso.c
> > @@ -32,6 +32,7 @@
> > #include "string2.h"
> > #include "vdso.h"
> > #include "annotate-data.h"
> > +#include "libdw.h"
> >
> > static const char * const debuglink_paths[] = {
> > "%.0s%s",
> > @@ -1605,6 +1606,7 @@ void dso__delete(struct dso *dso)
> > auxtrace_cache__free(RC_CHK_ACCESS(dso)->auxtrace_cache);
> > dso_cache__free(dso);
> > dso__free_a2l(dso);
> > + dso__free_a2l_libdw(dso);
> > dso__free_symsrc_filename(dso);
> > nsinfo__zput(RC_CHK_ACCESS(dso)->nsinfo);
> > mutex_destroy(dso__lock(dso));
> > diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
> > index f8ccb9816b89..4aee23775054 100644
> > --- a/tools/perf/util/dso.h
> > +++ b/tools/perf/util/dso.h
> > @@ -268,6 +268,7 @@ DECLARE_RC_STRUCT(dso) {
> > const char *short_name;
> > const char *long_name;
> > void *a2l;
> > + void *a2l_libdw;
> > char *symsrc_filename;
> > #if defined(__powerpc__)
> > void *dwfl; /* DWARF debug info */
> > @@ -334,6 +335,16 @@ static inline void dso__set_a2l(struct dso *dso, void *val)
> > RC_CHK_ACCESS(dso)->a2l = val;
> > }
> >
> > +static inline void *dso__a2l_libdw(const struct dso *dso)
> > +{
> > + return RC_CHK_ACCESS(dso)->a2l_libdw;
> > +}
> > +
> > +static inline void dso__set_a2l_libdw(struct dso *dso, void *val)
> > +{
> > + RC_CHK_ACCESS(dso)->a2l_libdw = val;
> > +}
> > +
> > static inline unsigned int dso__a2l_fails(const struct dso *dso)
> > {
> > return RC_CHK_ACCESS(dso)->a2l_fails;
> > diff --git a/tools/perf/util/libdw.c b/tools/perf/util/libdw.c
> > new file mode 100644
> > index 000000000000..e4bfd52bd172
> > --- /dev/null
> > +++ b/tools/perf/util/libdw.c
> > @@ -0,0 +1,153 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#include "dso.h"
> > +#include "libdw.h"
> > +#include "srcline.h"
> > +#include "symbol.h"
> > +#include "dwarf-aux.h"
> > +#include <fcntl.h>
> > +#include <unistd.h>
> > +#include <elfutils/libdwfl.h>
> > +
> > +void dso__free_a2l_libdw(struct dso *dso)
> > +{
> > + Dwfl *dwfl = dso__a2l_libdw(dso);
> > +
> > + if (dwfl) {
> > + dwfl_end(dwfl);
> > + dso__set_a2l_libdw(dso, NULL);
> > + }
> > +}
> > +
> > +struct libdw_a2l_cb_args {
> > + struct dso *dso;
> > + struct symbol *sym;
> > + struct inline_node *node;
> > + char *leaf_srcline;
> > + bool leaf_srcline_used;
> > +};
> > +
> > +static int libdw_a2l_cb(Dwarf_Die *die, void *_args)
> > +{
> > + struct libdw_a2l_cb_args *args = _args;
> > + struct symbol *inline_sym = new_inline_sym(args->dso, args->sym, dwarf_diename(die));
> > + const char *call_fname = die_get_call_file(die);
> > + char *call_srcline = srcline__unknown;
> > + struct inline_list *ilist;
> > +
> > + if (!inline_sym)
> > + return -ENOMEM;
> > +
> > + /* Assign caller information to the parent. */
> > + if (call_fname)
> > + call_srcline = srcline_from_fileline(call_fname, die_get_call_lineno(die));
> > +
> > + list_for_each_entry(ilist, &args->node->val, list) {
> > + ilist->srcline = call_srcline;
> > + call_srcline = NULL;
> > + break;
> > + }
> > + if (call_srcline && call_fname)
> > + free(call_srcline);
> > +
> > + /* Add this symbol to the chain as the leaf. */
> > + inline_list__append_tail(inline_sym, args->leaf_srcline, args->node);
> > + args->leaf_srcline_used = true;
> > + return 0;
> > +}
> > +
> > +int libdw__addr2line(const char *dso_name, u64 addr,
> > + char **file, unsigned int *line_nr,
> > + struct dso *dso, bool unwind_inlines,
> > + struct inline_node *node, struct symbol *sym)
> > +{
> > + static const Dwfl_Callbacks offline_callbacks = {
> > + .find_debuginfo = dwfl_standard_find_debuginfo,
> > + .section_address = dwfl_offline_section_address,
> > + .find_elf = dwfl_build_id_find_elf,
> > + };
> > + Dwfl *dwfl = dso__a2l_libdw(dso);
> > + Dwfl_Module *mod;
> > + Dwfl_Line *dwline;
> > + Dwarf_Addr bias;
> > + const char *src;
> > + int lineno = 0;
> > +
> > + if (!dwfl) {
> > + /*
> > + * Initialize Dwfl session.
> > + * We need to open the DSO file to report it to libdw.
> > + */
> > + int fd;
> > +
> > + fd = open(dso_name, O_RDONLY);
> > + if (fd < 0)
> > + return 0;
> > +
> > + dwfl = dwfl_begin(&offline_callbacks);
> > + if (!dwfl) {
> > + close(fd);
> > + return 0;
> > + }
> > +
> > + /*
> > + * If the report is successful, the file descriptor fd is consumed
> > + * and closed by the Dwfl. If not, it is not closed.
> > + */
> > + mod = dwfl_report_offline(dwfl, dso_name, dso_name, fd);
> > + if (!mod) {
> > + dwfl_end(dwfl);
> > + close(fd);
> > + return 0;
> > + }
> > +
> > + dwfl_report_end(dwfl, /*removed=*/NULL, /*arg=*/NULL);
> > + dso__set_a2l_libdw(dso, dwfl);
> > + } else {
> > + /* Dwfl session already initialized, get module for address. */
> > + mod = dwfl_addrmodule(dwfl, addr);
> > + }
> > +
> > + if (!mod)
> > + return 0;
> > +
> > + /*
> > + * Get/ignore the dwarf information. Determine the bias, difference
> > + * between the regular ELF addr2line addresses and those to use with
> > + * libdw.
> > + */
> > + if (!dwfl_module_getdwarf(mod, &bias))
> > + return 0;
> > +
> > + /* Find source line information for the address. */
> > + dwline = dwfl_module_getsrc(mod, addr + bias);
> > + if (!dwline)
> > + return 0;
> > +
> > + /* Get line information. */
> > + src = dwfl_lineinfo(dwline, /*addr=*/NULL, &lineno, /*col=*/NULL, /*mtime=*/NULL,
> > + /*length=*/NULL);
> > +
> > + if (file)
> > + *file = src ? strdup(src) : NULL;
> > + if (line_nr)
> > + *line_nr = lineno;
> > +
> > + /* Optionally unwind inline function call chain. */
> > + if (unwind_inlines && node) {
> > + Dwarf_Addr unused_bias;
> > + Dwarf_Die *cudie = dwfl_module_addrdie(mod, addr + bias, &unused_bias);
> > + struct libdw_a2l_cb_args args = {
> > + .dso = dso,
> > + .sym = sym,
> > + .node = node,
> > + .leaf_srcline = srcline_from_fileline(src ?: "<unknown>", lineno),
> > + };
> > +
> > + /* Walk from the parent down to the leaf. */
> > + cu_walk_functions_at(cudie, addr, libdw_a2l_cb, &args);
> > +
> > + if (!args.leaf_srcline_used)
> > + free(args.leaf_srcline);
> > + }
> > + return 1;
> > +}
> > diff --git a/tools/perf/util/libdw.h b/tools/perf/util/libdw.h
> > new file mode 100644
> > index 000000000000..0f8d7b4a11a5
> > --- /dev/null
> > +++ b/tools/perf/util/libdw.h
> > @@ -0,0 +1,60 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef PERF_LIBDW_H
> > +#define PERF_LIBDW_H
> > +
> > +#include <linux/types.h>
> > +
> > +struct dso;
> > +struct inline_node;
> > +struct symbol;
> > +
> > +#ifdef HAVE_LIBDW_SUPPORT
> > +/*
> > + * libdw__addr2line - Convert address to source location using libdw
> > + * @dso_name: Name of the DSO
> > + * @addr: Address to resolve
> > + * @file: Pointer to return filename (caller must free)
> > + * @line_nr: Pointer to return line number
> > + * @dso: The dso struct
> > + * @unwind_inlines: Whether to unwind inline function calls
> > + * @node: Inline node list to append to
> > + * @sym: The symbol associated with the address
> > + *
> > + * This function initializes a Dwfl context for the DSO if not already present,
> > + * finds the source line information for the given address, and optionally
> > + * resolves inline function call chains.
> > + *
> > + * Returns 1 on success (found), 0 on failure (not found).
> > + */
> > +int libdw__addr2line(const char *dso_name, u64 addr, char **file,
> > + unsigned int *line_nr, struct dso *dso,
> > + bool unwind_inlines, struct inline_node *node,
> > + struct symbol *sym);
> > +
> > +/*
> > + * dso__free_a2l_libdw - Free libdw resources associated with the DSO
> > + * @dso: The dso to free resources for
> > + *
> > + * This function cleans up the Dwfl context used for addr2line lookups.
> > + */
> > +void dso__free_a2l_libdw(struct dso *dso);
> > +
> > +#else /* HAVE_LIBDW_SUPPORT */
> > +
> > +static inline int libdw__addr2line(const char *dso_name __maybe_unused,
> > + u64 addr __maybe_unused, char **file __maybe_unused,
> > + unsigned int *line_nr __maybe_unused,
> > + struct dso *dso __maybe_unused,
> > + bool unwind_inlines __maybe_unused,
> > + struct inline_node *node __maybe_unused,
> > + struct symbol *sym __maybe_unused)
> > +{
> > + return 0;
> > +}
> > +
> > +static inline void dso__free_a2l_libdw(struct dso *dso __maybe_unused)
> > +{
> > +}
> > +#endif /* HAVE_LIBDW_SUPPORT */
> > +
> > +#endif /* PERF_LIBDW_H */
> > diff --git a/tools/perf/util/srcline.c b/tools/perf/util/srcline.c
> > index 27c0966611ab..e2d280678b02 100644
> > --- a/tools/perf/util/srcline.c
> > +++ b/tools/perf/util/srcline.c
> > @@ -6,6 +6,7 @@
> > #include "libbfd.h"
> > #include "llvm.h"
> > #include "symbol.h"
> > +#include "libdw.h"
> >
> > #include <inttypes.h>
> > #include <string.h>
> > @@ -51,6 +52,25 @@ int inline_list__append(struct symbol *symbol, char *srcline, struct inline_node
> > return 0;
> > }
> >
> > +int inline_list__append_tail(struct symbol *symbol, char *srcline, struct inline_node *node)
> > +{
> > + struct inline_list *ilist;
> > +
> > + ilist = zalloc(sizeof(*ilist));
> > + if (ilist == NULL)
> > + return -1;
> > +
> > + ilist->symbol = symbol;
> > + ilist->srcline = srcline;
> > +
> > + if (callchain_param.order == ORDER_CALLEE)
> > + list_add(&ilist->list, &node->val);
> > + else
> > + list_add_tail(&ilist->list, &node->val);
> > +
> > + return 0;
> > +}
> > +
> > /* basename version that takes a const input string */
> > static const char *gnu_basename(const char *path)
> > {
> > @@ -120,6 +140,10 @@ static int addr2line(const char *dso_name, u64 addr, char **file, unsigned int *
> > {
> > int ret;
> >
> > + ret = libdw__addr2line(dso_name, addr, file, line_nr, dso, unwind_inlines, node, sym);
> > + if (ret > 0)
> > + return ret;
> > +
> > ret = llvm__addr2line(dso_name, addr, file, line_nr, dso, unwind_inlines, node, sym);
> > if (ret > 0)
> > return ret;
> > diff --git a/tools/perf/util/srcline.h b/tools/perf/util/srcline.h
> > index c36f573cd339..be9f002bf234 100644
> > --- a/tools/perf/util/srcline.h
> > +++ b/tools/perf/util/srcline.h
> > @@ -57,6 +57,7 @@ struct inline_node *inlines__tree_find(struct rb_root_cached *tree, u64 addr);
> > void inlines__tree_delete(struct rb_root_cached *tree);
> >
> > int inline_list__append(struct symbol *symbol, char *srcline, struct inline_node *node);
> > +int inline_list__append_tail(struct symbol *symbol, char *srcline, struct inline_node *node);
> > char *srcline_from_fileline(const char *file, unsigned int line);
> > struct symbol *new_inline_sym(struct dso *dso,
> > struct symbol *base_sym,
> > --
> > 2.52.0.457.g6b5491de43-goog
> >
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