linux-kernel - [PATCH perf/core 1/2] perf probe: Do not access kallsyms when analyzing user binaries

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Date:	Wed, 17 Sep 2014 08:40:54 +0000
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	linux-perf-user@...r.kernel.org,
	david lerner <dlernerdroid@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	yrl.pp-manager.tt@...achi.com
Subject: [PATCH perf/core 1/2] perf probe: Do not access kallsyms when
 analyzing user binaries

Do not access kallsyms to show available variables and
show source lines in user binaries.
This behavior always requires the root privilege when
sysctl sets kernel.kptr_restrict=1, but we don't need
it just for analyzing user binaries.

Without this patch (by normal user, kptr_restrict=1):
  ----
  $ perf probe -x ./perf -V add_cmdname
  Failed to init vmlinux path.
    Error: Failed to show vars.
  $ perf probe -x ./perf -L add_cmdname
  Failed to init vmlinux path.
    Error: Failed to show lines.
  ----

With this patch:
  ----
  $ perf probe -x ./perf -V add_cmdname
  Available variables at add_cmdname
          @<perf_unknown_cmd_config+144>
                  (No matched variables)
          @<list_commands_in_dir+160>
                  (No matched variables)
          @<add_cmdname+0>
                  char*   name
                  size_t  len
                  struct cmdnames*        cmds
  $ perf probe -x ./perf -L add_cmdname
  <add_cmdname@...me/fedora/ksrc/linux-3/tools/perf/util/help.c:0>
        0  void add_cmdname(struct cmdnames *cmds, const char *name, size_t len)
        1  {
        2         struct cmdname *ent = malloc(sizeof(*ent) + len + 1);

        4         ent->len = len;
        5         memcpy(ent->name, name, len);
        6         ent->name[len] = 0;
  ...
  ----

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
---
 tools/perf/builtin-probe.c    |    3 ++-
 tools/perf/util/probe-event.c |    6 +++---
 tools/perf/util/probe-event.h |    3 ++-
 3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c
index 347729e..a9b82c4b 100644
--- a/tools/perf/builtin-probe.c
+++ b/tools/perf/builtin-probe.c
@@ -470,7 +470,8 @@ __cmd_probe(int argc, const char **argv, const char *prefix __maybe_unused)
 			usage_with_options(probe_usage, options);
 		}
 
-		ret = show_line_range(&params.line_range, params.target);
+		ret = show_line_range(&params.line_range, params.target,
+				      params.uprobes);
 		if (ret < 0)
 			pr_err_with_code("  Error: Failed to show lines.", ret);
 		return ret;
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index f73595f..041e63c 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -697,11 +697,11 @@ end:
 	return ret;
 }
 
-int show_line_range(struct line_range *lr, const char *module)
+int show_line_range(struct line_range *lr, const char *module, bool user)
 {
 	int ret;
 
-	ret = init_symbol_maps(false);
+	ret = init_symbol_maps(user);
 	if (ret < 0)
 		return ret;
 	ret = __show_line_range(lr, module);
@@ -776,7 +776,7 @@ int show_available_vars(struct perf_probe_event *pevs, int npevs,
 	int i, ret = 0;
 	struct debuginfo *dinfo;
 
-	ret = init_symbol_maps(false);
+	ret = init_symbol_maps(pevs->uprobes);
 	if (ret < 0)
 		return ret;
 
diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
index 776c934..e01e994 100644
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -128,7 +128,8 @@ extern int add_perf_probe_events(struct perf_probe_event *pevs, int npevs,
 				 bool force_add);
 extern int del_perf_probe_events(struct strlist *dellist);
 extern int show_perf_probe_events(void);
-extern int show_line_range(struct line_range *lr, const char *module);
+extern int show_line_range(struct line_range *lr, const char *module,
+			   bool user);
 extern int show_available_vars(struct perf_probe_event *pevs, int npevs,
 			       int max_probe_points, const char *module,
 			       struct strfilter *filter, bool externs);


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