[PATCH AUTOSEL 5.4 227/350] perf probe: Fix to probe a function which has no entry pc

Sasha Levin
2019-12-10T21:11:39Z

From: Masami Hiramatsu <mhiramat@kernel.org>

[ Upstream commit 5d16dbcc311d91267ddb45c6da4f187be320ecee ]

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

After:

[root@quaco ~]# 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@quaco ~]#

Using it with 'perf trace':

[root@quaco ~]# 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@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/157199319438.8075.4695576954550638618.stgit@devnote2
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/perf/util/probe-finder.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 7857ae7a10b73..4079ed617f53c 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -994,7 +994,7 @@ static int probe_point_search_cb(Dwarf_Die *sp_die, void *data)
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",
--
2.20.1