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

Thomas Backlund
2019-12-29T18:40:13Z

Den 29-12-2019 kl. 19:25, skrev Greg Kroah-Hartman:
> 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 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