The vdso dumped from process memory (in buildid-cache) lacks debugging
info. To annotate vdso symbols with source lines we need specify a
debugging version.

For x86, we can find them from your local build as
arch/x86/entry/vdso/vdso{32,64}.so.dbg. Or they may reside in
/lib/modules/<version>/vdso/vdso{32,64}.so on Ubuntu. But notice that
the buildid has to match.

$ sudo perf record -a
$ sudo perf report --objdump=llvm-objdump \
  --vdso arch/x86/entry/vdso/vdso64.so.dbg,arch/x86/entry/vdso/vdso32.so.dbg

Samples: 17K of event 'cycles:P', 4000 Hz, Event count (approx.): 1760
__vdso_clock_gettime  /work/linux-host/arch/x86/entry/vdso/vdso64.so.d
Percent│       movq    -48(%rbp),%rsi
       │       testq   %rax,%rax
       │     ;               return vread_hvclock();
       │       movq    %rax,%rdx
       │     ;               if (unlikely(!vdso_cycles_ok(cycles)))
       │     ↑ js      eb
       │     ↑ jmp     74
       │     ;               ts->tv_sec = vdso_ts->sec;
  0.02 │147:   leaq    2(%rbx),%rax
       │       shlq    $4, %rax
       │       addq    %r10,%rax
       │     ;               while ((seq = READ_ONCE(vd->seq)) & 1) {
  9.38 │152:   movl    (%r10),%ecx

When doing cross platform analysis, we also need specify the vdso path if
we are interested in its symbols.

v2: update documentation.

Signed-off-by: Changbin Du <changbin.du@huawei.com>
---
 tools/perf/Documentation/perf-annotate.txt |  3 +
 tools/perf/Documentation/perf-c2c.txt      |  3 +
 tools/perf/Documentation/perf-inject.txt   |  3 +
 tools/perf/Documentation/perf-report.txt   |  3 +
 tools/perf/Documentation/perf-script.txt   |  3 +
 tools/perf/Documentation/perf-top.txt      |  3 +
 tools/perf/builtin-annotate.c              |  2 +
 tools/perf/builtin-c2c.c                   |  2 +
 tools/perf/builtin-inject.c                |  2 +
 tools/perf/builtin-report.c                |  2 +
 tools/perf/builtin-script.c                |  2 +
 tools/perf/builtin-top.c                   |  2 +
 tools/perf/util/disasm.c                   |  7 +-
 tools/perf/util/symbol.c                   | 82 +++++++++++++++++++++-
 tools/perf/util/symbol_conf.h              |  5 ++
 15 files changed, 119 insertions(+), 5 deletions(-)

diff --git a/tools/perf/Documentation/perf-annotate.txt b/tools/perf/Documentation/perf-annotate.txt
index b95524bea021..4b6692f9a793 100644
--- a/tools/perf/Documentation/perf-annotate.txt
+++ b/tools/perf/Documentation/perf-annotate.txt
@@ -58,6 +58,9 @@ OPTIONS
 --ignore-vmlinux::
 	Ignore vmlinux files.
 
+--vdso=<vdso1[,vdso2]>::
+	Specify vdso pathnames. You can specify up to two for multiarch-support.
+
 --itrace::
 	Options for decoding instruction tracing data. The options are:
 
diff --git a/tools/perf/Documentation/perf-c2c.txt b/tools/perf/Documentation/perf-c2c.txt
index 856f0dfb8e5a..7c07efca7542 100644
--- a/tools/perf/Documentation/perf-c2c.txt
+++ b/tools/perf/Documentation/perf-c2c.txt
@@ -71,6 +71,9 @@ REPORT OPTIONS
 --vmlinux=<file>::
 	vmlinux pathname
 
+--vdso=<vdso1[,vdso2]>::
+	Specify vdso pathnames. You can specify up to two for multiarch-support.
+
 -v::
 --verbose::
 	Be more verbose (show counter open errors, etc).
diff --git a/tools/perf/Documentation/perf-inject.txt b/tools/perf/Documentation/perf-inject.txt
index c972032f4ca0..3c88967b4c7f 100644
--- a/tools/perf/Documentation/perf-inject.txt
+++ b/tools/perf/Documentation/perf-inject.txt
@@ -62,6 +62,9 @@ OPTIONS
 --kallsyms=<file>::
 	kallsyms pathname
 
+--vdso=<vdso1[,vdso2]>::
+	Specify vdso pathnames. You can specify up to two for multiarch-support.
+
 --itrace::
 	Decode Instruction Tracing data, replacing it with synthesized events.
 	Options are:
diff --git a/tools/perf/Documentation/perf-report.txt b/tools/perf/Documentation/perf-report.txt
index d2b1593ef700..8a3ba5f74cac 100644
--- a/tools/perf/Documentation/perf-report.txt
+++ b/tools/perf/Documentation/perf-report.txt
@@ -345,6 +345,9 @@ OPTIONS
         Load module symbols. WARNING: This should only be used with -k and
         a LIVE kernel.
 
+--vdso=<vdso1[,vdso2]>::
+	Specify vdso pathnames. You can specify up to two for multiarch-support.
+
 -f::
 --force::
         Don't do ownership validation.
diff --git a/tools/perf/Documentation/perf-script.txt b/tools/perf/Documentation/perf-script.txt
index ff086ef05a0c..48f9974ca4c5 100644
--- a/tools/perf/Documentation/perf-script.txt
+++ b/tools/perf/Documentation/perf-script.txt
@@ -296,6 +296,9 @@ OPTIONS
 --kallsyms=<file>::
         kallsyms pathname
 
+--vdso=<vdso1[,vdso2]>::
+	Specify vdso pathnames. You can specify up to two for multiarch-support.
+
 --symfs=<directory>::
         Look for files with symbols relative to this directory.
 
diff --git a/tools/perf/Documentation/perf-top.txt b/tools/perf/Documentation/perf-top.txt
index 667e5102075e..99f53b5b336b 100644
--- a/tools/perf/Documentation/perf-top.txt
+++ b/tools/perf/Documentation/perf-top.txt
@@ -80,6 +80,9 @@ Default is to monitor all CPUS.
 --kallsyms=<file>::
 	kallsyms pathname
 
+--vdso=<vdso1[,vdso2]>::
+	Specify vdso pathnames. You can specify up to two for multiarch-support.
+
 -m <pages>::
 --mmap-pages=<pages>::
 	Number of mmap data pages (must be a power of two) or size
diff --git a/tools/perf/builtin-annotate.c b/tools/perf/builtin-annotate.c
index b10b7f005658..e0aa657e6ca0 100644
--- a/tools/perf/builtin-annotate.c
+++ b/tools/perf/builtin-annotate.c
@@ -742,6 +742,8 @@ int cmd_annotate(int argc, const char **argv)
 		   "file", "vmlinux pathname"),
 	OPT_BOOLEAN('m', "modules", &symbol_conf.use_modules,
 		    "load module symbols - WARNING: use only with -k and LIVE kernel"),
+	OPT_CALLBACK(0, "vdso", NULL, "vdso1[,vdso2]", "vdso pathnames",
+		     parse_vdso_pathnames),
 	OPT_BOOLEAN('l', "print-line", &annotate_opts.print_lines,
 		    "print matching source lines (may be slow)"),
 	OPT_BOOLEAN('P', "full-paths", &annotate_opts.full_path,
diff --git a/tools/perf/builtin-c2c.c b/tools/perf/builtin-c2c.c
index c157bd31f2e5..4764f9139661 100644
--- a/tools/perf/builtin-c2c.c
+++ b/tools/perf/builtin-c2c.c
@@ -3018,6 +3018,8 @@ static int perf_c2c__report(int argc, const char **argv)
 	const struct option options[] = {
 	OPT_STRING('k', "vmlinux", &symbol_conf.vmlinux_name,
 		   "file", "vmlinux pathname"),
+	OPT_CALLBACK(0, "vdso", NULL, "vdso1[,vdso2]", "vdso pathnames",
+		     parse_vdso_pathnames),
 	OPT_STRING('i', "input", &input_name, "file",
 		   "the input file to process"),
 	OPT_INCR('N', "node-info", &c2c.node_info,
diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
index a212678d47be..e774e83d0a0f 100644
--- a/tools/perf/builtin-inject.c
+++ b/tools/perf/builtin-inject.c
@@ -2247,6 +2247,8 @@ int cmd_inject(int argc, const char **argv)
 			    "don't load vmlinux even if found"),
 		OPT_STRING(0, "kallsyms", &symbol_conf.kallsyms_name, "file",
 			   "kallsyms pathname"),
+		OPT_CALLBACK(0, "vdso", NULL, "vdso1[,vdso2]", "vdso pathnames",
+		     parse_vdso_pathnames),
 		OPT_BOOLEAN('f', "force", &data.force, "don't complain, do it"),
 		OPT_CALLBACK_OPTARG(0, "itrace", &inject.itrace_synth_opts,
 				    NULL, "opts", "Instruction Tracing options\n"
diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 6edc0d4ce6fb..00ddf4f06324 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -1321,6 +1321,8 @@ int cmd_report(int argc, const char **argv)
                     "don't load vmlinux even if found"),
 	OPT_STRING(0, "kallsyms", &symbol_conf.kallsyms_name,
 		   "file", "kallsyms pathname"),
+	OPT_CALLBACK(0, "vdso", NULL, "vdso1[,vdso2]", "vdso pathnames",
+		     parse_vdso_pathnames),
 	OPT_BOOLEAN('f', "force", &symbol_conf.force, "don't complain, do it"),
 	OPT_BOOLEAN('m', "modules", &symbol_conf.use_modules,
 		    "load module symbols - WARNING: use only with -k and LIVE kernel"),
diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index c16224b1fef3..2e358922a8d1 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -3965,6 +3965,8 @@ int cmd_script(int argc, const char **argv)
 		   "file", "vmlinux pathname"),
 	OPT_STRING(0, "kallsyms", &symbol_conf.kallsyms_name,
 		   "file", "kallsyms pathname"),
+	OPT_CALLBACK(0, "vdso", NULL, "vdso1[,vdso2]", "vdso pathnames",
+		     parse_vdso_pathnames),
 	OPT_BOOLEAN('G', "hide-call-graph", &no_callchain,
 		    "When printing symbols do not display call chain"),
 	OPT_CALLBACK(0, "symfs", NULL, "directory",
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index e8cbbf10d361..3a4cee6f2d2f 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1488,6 +1488,8 @@ int cmd_top(int argc, const char **argv)
 		   "file", "kallsyms pathname"),
 	OPT_BOOLEAN('K', "hide_kernel_symbols", &top.hide_kernel_symbols,
 		    "hide kernel symbols"),
+	OPT_CALLBACK(0, "vdso", NULL, "vdso1[,vdso2]", "vdso pathnames",
+		     parse_vdso_pathnames),
 	OPT_CALLBACK('m', "mmap-pages", &opts->mmap_pages, "pages",
 		     "number of mmap data pages", evlist__parse_mmap_pages),
 	OPT_INTEGER('r', "realtime", &top.realtime_prio,
diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
index e10558b79504..7e26d5215640 100644
--- a/tools/perf/util/disasm.c
+++ b/tools/perf/util/disasm.c
@@ -16,6 +16,7 @@
 #include "debug.h"
 #include "disasm.h"
 #include "dso.h"
+#include "vdso.h"
 #include "env.h"
 #include "evsel.h"
 #include "map.h"
@@ -1126,7 +1127,7 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
 	if (pos && strlen(pos) < SBUILD_ID_SIZE - 2)
 		dirname(build_id_path);
 
-	if (dso__is_kcore(dso))
+	if (dso__is_kcore(dso) || dso__is_vdso(dso))
 		goto fallback;
 
 	len = readlink(build_id_path, linkname, sizeof(linkname) - 1);
@@ -1134,7 +1135,7 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
 		goto fallback;
 
 	linkname[len] = '\0';
-	if (strstr(linkname, DSO__NAME_KALLSYMS) ||
+	if (strstr(linkname, DSO__NAME_KALLSYMS) || strstr(linkname, DSO__NAME_VDSO) ||
 		access(filename, R_OK)) {
 fallback:
 		/*
@@ -1142,7 +1143,7 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
 		 * cache, or is just a kallsyms file, well, lets hope that this
 		 * DSO is the same as when 'perf record' ran.
 		 */
-		if (dso__kernel(dso) && dso__long_name(dso)[0] == '/')
+		if ((dso__kernel(dso) || dso__is_vdso(dso)) && dso__long_name(dso)[0] == '/')
 			snprintf(filename, filename_size, "%s", dso__long_name(dso));
 		else
 			__symbol__join_symfs(filename, filename_size, dso__long_name(dso));
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 19eb623e0826..ad3b7b929e94 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -19,6 +19,7 @@
 #include "build-id.h"
 #include "cap.h"
 #include "dso.h"
+#include "vdso.h"
 #include "util.h" // lsdir()
 #include "debug.h"
 #include "event.h"
@@ -44,6 +45,7 @@
 
 static int dso__load_kernel_sym(struct dso *dso, struct map *map);
 static int dso__load_guest_kernel_sym(struct dso *dso, struct map *map);
+static int dso__load_vdso_sym(struct dso *dso, struct map *map);
 static bool symbol__is_idle(const char *name);
 
 int vmlinux_path__nr_entries;
@@ -1832,6 +1834,12 @@ int dso__load(struct dso *dso, struct map *map)
 		goto out;
 	}
 
+	if (dso__is_vdso(dso)) {
+		ret = dso__load_vdso_sym(dso, map);
+		if (ret > 0)
+			goto out;
+	}
+
 	dso__set_adjust_symbols(dso, false);
 
 	if (perfmap) {
@@ -2016,12 +2024,14 @@ int dso__load_vmlinux(struct dso *dso, struct map *map,
 		dso__set_binary_type(dso, DSO_BINARY_TYPE__VMLINUX);
 
 	err = dso__load_sym(dso, map, &ss, &ss, 0);
-	symsrc__destroy(&ss);
-
 	if (err > 0) {
 		dso__set_loaded(dso);
 		pr_debug("Using %s for symbols\n", symfs_vmlinux);
+
+		if (symsrc__has_symtab(&ss) && !dso__symsrc_filename(dso))
+			dso__set_symsrc_filename(dso, strdup(symfs_vmlinux));
 	}
+	symsrc__destroy(&ss);
 
 	return err;
 }
@@ -2348,6 +2358,74 @@ static int vmlinux_path__init(struct perf_env *env)
 	return -1;
 }
 
+int parse_vdso_pathnames(const struct option *opt __maybe_unused,
+			 const char *arg, int unset __maybe_unused)
+{
+	char *tmp, *tok, *str = strdup(arg);
+	unsigned int i = 0;
+
+	for (tok = strtok_r(str, ",", &tmp); tok && i < ARRAY_SIZE(symbol_conf.vdso_name);
+	     tok = strtok_r(NULL, ",", &tmp)) {
+		symbol_conf.vdso_name[i++] = strdup(tok);
+	}
+
+	free(str);
+	return 0;
+}
+
+static int dso__load_vdso(struct dso *dso, struct map *map,
+			  const char *vdso)
+{
+	int err = -1;
+	struct symsrc ss;
+	char symfs_vdso[PATH_MAX];
+
+	if (vdso[0] == '/')
+		snprintf(symfs_vdso, sizeof(symfs_vdso), "%s", vdso);
+	else
+		symbol__join_symfs(symfs_vdso, vdso);
+
+	if (symsrc__init(&ss, dso, symfs_vdso, DSO_BINARY_TYPE__SYSTEM_PATH_DSO))
+		return -1;
+
+	/*
+	 * dso__load_sym() may copy 'dso' which will result in the copies having
+	 * an incorrect long name unless we set it here first.
+	 */
+	dso__set_long_name(dso, vdso, false);
+	dso__set_binary_type(dso, DSO_BINARY_TYPE__SYSTEM_PATH_DSO);
+
+	err = dso__load_sym(dso, map, &ss, &ss, 0);
+	if (err > 0) {
+		dso__set_loaded(dso);
+		pr_debug("Using %s for %s symbols\n", symfs_vdso, dso__short_name(dso));
+
+		if (symsrc__has_symtab(&ss) && !dso__symsrc_filename(dso))
+			dso__set_symsrc_filename(dso, strdup(symfs_vdso));
+	}
+	symsrc__destroy(&ss);
+
+	return err;
+}
+
+static int dso__load_vdso_sym(struct dso *dso, struct map *map)
+{
+	int ret;
+
+	if (!dso__is_vdso(dso))
+		return -1;
+
+	for (unsigned int i = 0; i < ARRAY_SIZE(symbol_conf.vdso_name); i++) {
+		if (symbol_conf.vdso_name[i] != NULL) {
+			ret = dso__load_vdso(dso, map, symbol_conf.vdso_name[i]);
+			if (ret > 0)
+				return ret;
+		}
+	}
+
+	return -1;
+}
+
 int setup_list(struct strlist **list, const char *list_str,
 		      const char *list_name)
 {
diff --git a/tools/perf/util/symbol_conf.h b/tools/perf/util/symbol_conf.h
index 657cfa5af43c..deaec9a60904 100644
--- a/tools/perf/util/symbol_conf.h
+++ b/tools/perf/util/symbol_conf.h
@@ -3,6 +3,7 @@
 #define __PERF_SYMBOL_CONF 1
 
 #include <stdbool.h>
+#include <subcmd/parse-options.h>
 
 struct strlist;
 struct intlist;
@@ -56,6 +57,7 @@ struct symbol_conf {
 	const char	*default_guest_vmlinux_name,
 			*default_guest_kallsyms,
 			*default_guest_modules;
+	const char	*vdso_name[2];
 	const char	*guestmount;
 	const char	*dso_list_str,
 			*comm_list_str,
@@ -86,4 +88,7 @@ struct symbol_conf {
 
 extern struct symbol_conf symbol_conf;
 
+int parse_vdso_pathnames(const struct option *opt __maybe_unused,
+			 const char *arg, int unset __maybe_unused);
+
 #endif // __PERF_SYMBOL_CONF
-- 
2.34.1

On 25/07/24 05:15, Changbin Du wrote:
> The vdso dumped from process memory (in buildid-cache) lacks debugging
> info. To annotate vdso symbols with source lines we need specify a
> debugging version.
> 
> For x86, we can find them from your local build as
> arch/x86/entry/vdso/vdso{32,64}.so.dbg. Or they may reside in
> /lib/modules/<version>/vdso/vdso{32,64}.so on Ubuntu. But notice that
> the buildid has to match.
> 
> $ sudo perf record -a
> $ sudo perf report --objdump=llvm-objdump \
>   --vdso arch/x86/entry/vdso/vdso64.so.dbg,arch/x86/entry/vdso/vdso32.so.dbg
> 
> Samples: 17K of event 'cycles:P', 4000 Hz, Event count (approx.): 1760
> __vdso_clock_gettime  /work/linux-host/arch/x86/entry/vdso/vdso64.so.d
> Percent│       movq    -48(%rbp),%rsi
>        │       testq   %rax,%rax
>        │     ;               return vread_hvclock();
>        │       movq    %rax,%rdx
>        │     ;               if (unlikely(!vdso_cycles_ok(cycles)))
>        │     ↑ js      eb
>        │     ↑ jmp     74
>        │     ;               ts->tv_sec = vdso_ts->sec;
>   0.02 │147:   leaq    2(%rbx),%rax
>        │       shlq    $4, %rax
>        │       addq    %r10,%rax
>        │     ;               while ((seq = READ_ONCE(vd->seq)) & 1) {
>   9.38 │152:   movl    (%r10),%ecx
> 
> When doing cross platform analysis, we also need specify the vdso path if
> we are interested in its symbols.
> 
> v2: update documentation.
> 
> Signed-off-by: Changbin Du <changbin.du@huawei.com>
> ---
>  tools/perf/Documentation/perf-annotate.txt |  3 +
>  tools/perf/Documentation/perf-c2c.txt      |  3 +
>  tools/perf/Documentation/perf-inject.txt   |  3 +
>  tools/perf/Documentation/perf-report.txt   |  3 +
>  tools/perf/Documentation/perf-script.txt   |  3 +
>  tools/perf/Documentation/perf-top.txt      |  3 +
>  tools/perf/builtin-annotate.c              |  2 +
>  tools/perf/builtin-c2c.c                   |  2 +
>  tools/perf/builtin-inject.c                |  2 +
>  tools/perf/builtin-report.c                |  2 +
>  tools/perf/builtin-script.c                |  2 +
>  tools/perf/builtin-top.c                   |  2 +
>  tools/perf/util/disasm.c                   |  7 +-
>  tools/perf/util/symbol.c                   | 82 +++++++++++++++++++++-
>  tools/perf/util/symbol_conf.h              |  5 ++
>  15 files changed, 119 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/Documentation/perf-annotate.txt b/tools/perf/Documentation/perf-annotate.txt
> index b95524bea021..4b6692f9a793 100644
> --- a/tools/perf/Documentation/perf-annotate.txt
> +++ b/tools/perf/Documentation/perf-annotate.txt
> @@ -58,6 +58,9 @@ OPTIONS
>  --ignore-vmlinux::
>  	Ignore vmlinux files.
>  
> +--vdso=<vdso1[,vdso2]>::
> +	Specify vdso pathnames. You can specify up to two for multiarch-support.
> +
>  --itrace::
>  	Options for decoding instruction tracing data. The options are:
>  

<SNIP>

> diff --git a/tools/perf/builtin-annotate.c b/tools/perf/builtin-annotate.c
> index b10b7f005658..e0aa657e6ca0 100644
> --- a/tools/perf/builtin-annotate.c
> +++ b/tools/perf/builtin-annotate.c
> @@ -742,6 +742,8 @@ int cmd_annotate(int argc, const char **argv)
>  		   "file", "vmlinux pathname"),
>  	OPT_BOOLEAN('m', "modules", &symbol_conf.use_modules,
>  		    "load module symbols - WARNING: use only with -k and LIVE kernel"),
> +	OPT_CALLBACK(0, "vdso", NULL, "vdso1[,vdso2]", "vdso pathnames",
> +		     parse_vdso_pathnames),
>  	OPT_BOOLEAN('l', "print-line", &annotate_opts.print_lines,
>  		    "print matching source lines (may be slow)"),
>  	OPT_BOOLEAN('P', "full-paths", &annotate_opts.full_path,

<SNIP>

> diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
> index e10558b79504..7e26d5215640 100644
> --- a/tools/perf/util/disasm.c
> +++ b/tools/perf/util/disasm.c
> @@ -16,6 +16,7 @@
>  #include "debug.h"
>  #include "disasm.h"
>  #include "dso.h"
> +#include "vdso.h"
>  #include "env.h"
>  #include "evsel.h"
>  #include "map.h"
> @@ -1126,7 +1127,7 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
>  	if (pos && strlen(pos) < SBUILD_ID_SIZE - 2)
>  		dirname(build_id_path);
>  
> -	if (dso__is_kcore(dso))
> +	if (dso__is_kcore(dso) || dso__is_vdso(dso))

Sorry for very long delay.

This patch (probably this bit here) breaks annotation of vdso.
To allow for bisection, you need to arrange changes so that each
patch leaves things in a working state.

However, I disagree with adding --vdso option since with just
patch 8 alone, it would be possible to do:

  perf buildid-cache --remove /work/linux/arch/x86/entry/vdso/vdso64.so.dbg
  perf buildid-cache --add /work/linux/arch/x86/entry/vdso/vdso64.so.dbg

and same of vdso32.

That would leave the buildid-cache containing only the debug versions,
which would mean you will only get the debug versions, and it would only
need to be done once per kernel instead of having to add --vdso to
every perf command.

Hi, Adrian,

On Wed, Sep 11, 2024 at 11:03:21AM +0300, Adrian Hunter wrote:
> On 25/07/24 05:15, Changbin Du wrote:
> > The vdso dumped from process memory (in buildid-cache) lacks debugging
> > info. To annotate vdso symbols with source lines we need specify a
> > debugging version.
> > 
> > For x86, we can find them from your local build as
> > arch/x86/entry/vdso/vdso{32,64}.so.dbg. Or they may reside in
> > /lib/modules/<version>/vdso/vdso{32,64}.so on Ubuntu. But notice that
> > the buildid has to match.
> > 
> > $ sudo perf record -a
> > $ sudo perf report --objdump=llvm-objdump \
> >   --vdso arch/x86/entry/vdso/vdso64.so.dbg,arch/x86/entry/vdso/vdso32.so.dbg
> > 
> > Samples: 17K of event 'cycles:P', 4000 Hz, Event count (approx.): 1760
> > __vdso_clock_gettime  /work/linux-host/arch/x86/entry/vdso/vdso64.so.d
> > Percent│       movq    -48(%rbp),%rsi
> >        │       testq   %rax,%rax
> >        │     ;               return vread_hvclock();
> >        │       movq    %rax,%rdx
> >        │     ;               if (unlikely(!vdso_cycles_ok(cycles)))
> >        │     ↑ js      eb
> >        │     ↑ jmp     74
> >        │     ;               ts->tv_sec = vdso_ts->sec;
> >   0.02 │147:   leaq    2(%rbx),%rax
> >        │       shlq    $4, %rax
> >        │       addq    %r10,%rax
> >        │     ;               while ((seq = READ_ONCE(vd->seq)) & 1) {
> >   9.38 │152:   movl    (%r10),%ecx
> > 
> > When doing cross platform analysis, we also need specify the vdso path if
> > we are interested in its symbols.
> > 
> > v2: update documentation.
> > 
> > Signed-off-by: Changbin Du <changbin.du@huawei.com>
> > ---
> >  tools/perf/Documentation/perf-annotate.txt |  3 +
> >  tools/perf/Documentation/perf-c2c.txt      |  3 +
> >  tools/perf/Documentation/perf-inject.txt   |  3 +
> >  tools/perf/Documentation/perf-report.txt   |  3 +
> >  tools/perf/Documentation/perf-script.txt   |  3 +
> >  tools/perf/Documentation/perf-top.txt      |  3 +
> >  tools/perf/builtin-annotate.c              |  2 +
> >  tools/perf/builtin-c2c.c                   |  2 +
> >  tools/perf/builtin-inject.c                |  2 +
> >  tools/perf/builtin-report.c                |  2 +
> >  tools/perf/builtin-script.c                |  2 +
> >  tools/perf/builtin-top.c                   |  2 +
> >  tools/perf/util/disasm.c                   |  7 +-
> >  tools/perf/util/symbol.c                   | 82 +++++++++++++++++++++-
> >  tools/perf/util/symbol_conf.h              |  5 ++
> >  15 files changed, 119 insertions(+), 5 deletions(-)
> > 
> > diff --git a/tools/perf/Documentation/perf-annotate.txt b/tools/perf/Documentation/perf-annotate.txt
> > index b95524bea021..4b6692f9a793 100644
> > --- a/tools/perf/Documentation/perf-annotate.txt
> > +++ b/tools/perf/Documentation/perf-annotate.txt
> > @@ -58,6 +58,9 @@ OPTIONS
> >  --ignore-vmlinux::
> >  	Ignore vmlinux files.
> >  
> > +--vdso=<vdso1[,vdso2]>::
> > +	Specify vdso pathnames. You can specify up to two for multiarch-support.
> > +
> >  --itrace::
> >  	Options for decoding instruction tracing data. The options are:
> >  
> 
> <SNIP>
> 
> > diff --git a/tools/perf/builtin-annotate.c b/tools/perf/builtin-annotate.c
> > index b10b7f005658..e0aa657e6ca0 100644
> > --- a/tools/perf/builtin-annotate.c
> > +++ b/tools/perf/builtin-annotate.c
> > @@ -742,6 +742,8 @@ int cmd_annotate(int argc, const char **argv)
> >  		   "file", "vmlinux pathname"),
> >  	OPT_BOOLEAN('m', "modules", &symbol_conf.use_modules,
> >  		    "load module symbols - WARNING: use only with -k and LIVE kernel"),
> > +	OPT_CALLBACK(0, "vdso", NULL, "vdso1[,vdso2]", "vdso pathnames",
> > +		     parse_vdso_pathnames),
> >  	OPT_BOOLEAN('l', "print-line", &annotate_opts.print_lines,
> >  		    "print matching source lines (may be slow)"),
> >  	OPT_BOOLEAN('P', "full-paths", &annotate_opts.full_path,
> 
> <SNIP>
> 
> > diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
> > index e10558b79504..7e26d5215640 100644
> > --- a/tools/perf/util/disasm.c
> > +++ b/tools/perf/util/disasm.c
> > @@ -16,6 +16,7 @@
> >  #include "debug.h"
> >  #include "disasm.h"
> >  #include "dso.h"
> > +#include "vdso.h"
> >  #include "env.h"
> >  #include "evsel.h"
> >  #include "map.h"
> > @@ -1126,7 +1127,7 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
> >  	if (pos && strlen(pos) < SBUILD_ID_SIZE - 2)
> >  		dirname(build_id_path);
> >  
> > -	if (dso__is_kcore(dso))
> > +	if (dso__is_kcore(dso) || dso__is_vdso(dso))
> 
> Sorry for very long delay.
> 
> This patch (probably this bit here) breaks annotation of vdso.
> To allow for bisection, you need to arrange changes so that each
> patch leaves things in a working state.
> 
> However, I disagree with adding --vdso option since with just
> patch 8 alone, it would be possible to do:
> 
>   perf buildid-cache --remove /work/linux/arch/x86/entry/vdso/vdso64.so.dbg
>   perf buildid-cache --add /work/linux/arch/x86/entry/vdso/vdso64.so.dbg
> 
> and same of vdso32.
> 
> That would leave the buildid-cache containing only the debug versions,
> which would mean you will only get the debug versions, and it would only
> need to be done once per kernel instead of having to add --vdso to
> every perf command.
>

I may send patch 8 alone first and suspend the rest. I suppose mananging buildid-cache
for vdso mannually is enough for most case. So maybe it's better not get things
more complex.

> 

-- 
Cheers,
Changbin Du