perf tools: Check recorded kernel version when finding vmlinux

Currently vmlinux_path__init() only tries to find vmlinux file from
current directory, /boot and some canonical directories with version
number of the running kernel.  This can be a problem when reporting old
data recorded on a kernel version not running currently.

We can use --symfs option for this but it's annoying for user to do it
always.  As we already have the info in the perf.data file, it can be
changed to use it for the search automatically.

Before:

  $ perf report
  ...
  # Samples: 4K of event 'cpu-clock'
  # Event count (approx.): 1067250000
  #
  # Overhead  Command     Shared Object      Symbol
  # ........  ..........  .................  ..............................
      71.87%     swapper  [kernel.kallsyms]  [k] recover_probed_instruction

After:

  # Overhead  Command     Shared Object      Symbol
  # ........  ..........  .................  ....................
      71.87%     swapper  [kernel.kallsyms]  [k] native_safe_halt

This requires to change signature of symbol__init() to receive struct
perf_session_env *.

Reported-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1407825645-24586-14-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

3 files changed, 20 insertions, 11 deletions

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 443225cb62f7..784ea42ad8cb 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -79,7 +79,7 @@ static int init_symbol_maps(bool user_only)
 	int ret;
 
 	symbol_conf.sort_by_name = true;
-	ret = symbol__init();
+	ret = symbol__init(NULL);
 	if (ret < 0) {
 		pr_debug("Failed to init symbol map.\n");
 		goto out;
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 009a9d064f11..ac098a3c2a31 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -15,6 +15,7 @@
 #include "machine.h"
 #include "symbol.h"
 #include "strlist.h"
+#include "header.h"
 
 #include <elf.h>
 #include <limits.h>
@@ -1749,10 +1750,11 @@ static void vmlinux_path__exit(void)
 	zfree(&vmlinux_path);
 }
 
-static int vmlinux_path__init(void)
+static int vmlinux_path__init(struct perf_session_env *env)
 {
 	struct utsname uts;
 	char bf[PATH_MAX];
+	char *kernel_version;
 
 	vmlinux_path = malloc(sizeof(char *) * 5);
 	if (vmlinux_path == NULL)
@@ -1767,25 +1769,31 @@ static int vmlinux_path__init(void)
 		goto out_fail;
 	++vmlinux_path__nr_entries;
 
-	/* only try running kernel version if no symfs was given */
+	/* only try kernel version if no symfs was given */
 	if (symbol_conf.symfs[0] != 0)
 		return 0;
 
-	if (uname(&uts) < 0)
-		goto out_fail;
+	if (env) {
+		kernel_version = env->os_release;
+	} else {
+		if (uname(&uts) < 0)
+			goto out_fail;
+
+		kernel_version = uts.release;
+	}
 
-	snprintf(bf, sizeof(bf), "/boot/vmlinux-%s", uts.release);
+	snprintf(bf, sizeof(bf), "/boot/vmlinux-%s", kernel_version);
 	vmlinux_path[vmlinux_path__nr_entries] = strdup(bf);
 	if (vmlinux_path[vmlinux_path__nr_entries] == NULL)
 		goto out_fail;
 	++vmlinux_path__nr_entries;
-	snprintf(bf, sizeof(bf), "/lib/modules/%s/build/vmlinux", uts.release);
+	snprintf(bf, sizeof(bf), "/lib/modules/%s/build/vmlinux", kernel_version);
 	vmlinux_path[vmlinux_path__nr_entries] = strdup(bf);
 	if (vmlinux_path[vmlinux_path__nr_entries] == NULL)
 		goto out_fail;
 	++vmlinux_path__nr_entries;
 	snprintf(bf, sizeof(bf), "/usr/lib/debug/lib/modules/%s/vmlinux",
-		 uts.release);
+		 kernel_version);
 	vmlinux_path[vmlinux_path__nr_entries] = strdup(bf);
 	if (vmlinux_path[vmlinux_path__nr_entries] == NULL)
 		goto out_fail;
@@ -1831,7 +1839,7 @@ static bool symbol__read_kptr_restrict(void)
 	return value;
 }
 
-int symbol__init(void)
+int symbol__init(struct perf_session_env *env)
 {
 	const char *symfs;
 
@@ -1846,7 +1854,7 @@ int symbol__init(void)
 		symbol_conf.priv_size += (sizeof(struct symbol_name_rb_node) -
 					  sizeof(struct symbol));
 
-	if (symbol_conf.try_vmlinux_path && vmlinux_path__init() < 0)
+	if (symbol_conf.try_vmlinux_path && vmlinux_path__init(env) < 0)
 		return -1;
 
 	if (symbol_conf.field_sep && *symbol_conf.field_sep == '.') {
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index 196b29104276..b95e3a36d654 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -262,7 +262,8 @@ int modules__parse(const char *filename, void *arg,
 int filename__read_debuglink(const char *filename, char *debuglink,
 			     size_t size);
 
-int symbol__init(void);
+struct perf_session_env;
+int symbol__init(struct perf_session_env *env);
 void symbol__exit(void);
 void symbol__elf_init(void);
 struct symbol *symbol__new(u64 start, u64 len, u8 binding, const char *name);