linux-kernel - [PATCH 3.16 066/148] perf probe: Fix to probe a function which has no entry pc

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Message-ID: <lsq.1581185940.974232671@decadent.org.uk>
Date:   Sat, 08 Feb 2020 18:20:05 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Jiri Olsa" <jolsa@...hat.com>,
        "Masami Hiramatsu" <mhiramat@...nel.org>,
        "Arnaldo Carvalho de Melo" <acme@...hat.com>,
        "Namhyung Kim" <namhyung@...nel.org>,
        "Arnaldo Carvalho de Melo" <acme@...nel.org>
Subject: [PATCH 3.16 066/148] perf probe: Fix to probe a function which
 has no entry pc

3.16.82-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Masami Hiramatsu <mhiramat@...nel.org>

commit 5d16dbcc311d91267ddb45c6da4f187be320ecee upstream.

Fix 'perf probe' to probe a function which has no entry pc or low pc but
only has ranges attribute.

probe_point_search_cb() uses dwarf_entrypc() to get the probe address,
but that doesn't work for the function DIE which has only ranges
attribute. Use die_entrypc() instead.

Without this fix:

  # perf probe -k ../build-x86_64/vmlinux -D clear_tasks_mm_cpumask:0
  Probe point 'clear_tasks_mm_cpumask' not found.
    Error: Failed to add events.

With this:

  # perf probe -k ../build-x86_64/vmlinux -D clear_tasks_mm_cpumask:0
  p:probe/clear_tasks_mm_cpumask clear_tasks_mm_cpumask+0

Committer testing:

Before:

  [root@...co ~]# perf probe clear_tasks_mm_cpumask:0
  Probe point 'clear_tasks_mm_cpumask' not found.
    Error: Failed to add events.
  [root@...co ~]#

After:

  [root@...co ~]# perf probe clear_tasks_mm_cpumask:0
  Added new event:
    probe:clear_tasks_mm_cpumask (on clear_tasks_mm_cpumask)

  You can now use it in all perf tools, such as:

  	perf record -e probe:clear_tasks_mm_cpumask -aR sleep 1

  [root@...co ~]#

Using it with 'perf trace':

  [root@...co ~]# perf trace -e probe:clear_tasks_mm_cpumask

Doesn't seem to be used in x86_64:

  $ find . -name "*.c" | xargs grep clear_tasks_mm_cpumask
  ./kernel/cpu.c: * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
  ./kernel/cpu.c:void clear_tasks_mm_cpumask(int cpu)
  ./arch/xtensa/kernel/smp.c:	clear_tasks_mm_cpumask(cpu);
  ./arch/csky/kernel/smp.c:	clear_tasks_mm_cpumask(cpu);
  ./arch/sh/kernel/smp.c:	clear_tasks_mm_cpumask(cpu);
  ./arch/arm/kernel/smp.c:	clear_tasks_mm_cpumask(cpu);
  ./arch/powerpc/mm/nohash/mmu_context.c:	clear_tasks_mm_cpumask(cpu);
  $ find . -name "*.h" | xargs grep clear_tasks_mm_cpumask
  ./include/linux/cpu.h:void clear_tasks_mm_cpumask(int cpu);
  $ find . -name "*.S" | xargs grep clear_tasks_mm_cpumask
  $

Fixes: e1ecbbc3fa83 ("perf probe: Fix to handle optimized not-inlined functions")
Reported-by: Arnaldo Carvalho de Melo <acme@...nel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Link: http://lore.kernel.org/lkml/157199319438.8075.4695576954550638618.stgit@devnote2
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 tools/perf/util/probe-finder.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -908,7 +908,7 @@ static int probe_point_search_cb(Dwarf_D
 		param->retval = find_probe_point_by_line(pf);
 	} else if (die_is_func_instance(sp_die)) {
 		/* Instances always have the entry address */
-		dwarf_entrypc(sp_die, &pf->addr);
+		die_entrypc(sp_die, &pf->addr);
 		/* But in some case the entry address is 0 */
 		if (pf->addr == 0) {
 			pr_debug("%s has no entry PC. Skipped\n",