Re: [PATCH 5.4 252/434] perf probe: Fix to probe a function which has no entry pc

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Den 29-12-2019 kl. 19:25, skrev Greg Kroah-Hartman:
From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>

[ 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@xxxxxxxxxx>
Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Link: http://lore.kernel.org/lkml/157199319438.8075.4695576954550638618.stgit@devnote2
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
  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 7857ae7a10b7..4079ed617f53 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",


Still broken...

/usr/bin/ld: perf-in.o: in function `probe_point_search_cb':
/work/rpmbuild/BUILD/kernel-x86_64/linux-5.4/tools/perf/util/probe-finder.c:1012: undefined reference to `die_entrypc'

--
Thomas



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