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perf unwind: Do not fail due to missing unwind support

PATCH New Jiri Olsa 2 participants 2 messages Jul 4, 2017 – Jul 5, 2017 perf events

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Jiri Olsa

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PATCH 1/1 perf unwind: Do not fail due to missing unwind support

We currently fail the MMAP event processing if we don't have the MMAP event's specific arch unwind support compiled in.

That's wrong and can lead to unresolved mmaps in report output for 32bit binaries on 64bit server, like in this example on x86_64 server:

  $ cat ex.c
  int main(int argc, char **argv)
  {
          while (1) {}
  }
  $ gcc -o ex -m32 ex.c
  $ perf record ./ex
  ^C[ perf record: Woken up 2 times to write data ]
  [ perf record: Captured and wrote 0.371 MB perf.data (9322 samples) ]

Before:

  $ perf report --stdio

SNIP

  # Overhead  Command  Shared Object     Symbol
  # ........  .......  ................  ......................
  #
     100.00%  ex       [unknown]         [.] 0x00000000080483de
       0.00%  ex       [unknown]         [.] 0x00000000f76dba4f
       0.00%  ex       [unknown]         [.] 0x00000000f76e4c11
       0.00%  ex       [unknown]         [.] 0x00000000f76daa30

After:

  $ perf report --stdio

SNIP

  # Overhead  Command  Shared Object  Symbol
  # ........  .......  .............  ...............
  #
     100.00%  ex       ex             [.] main
       0.00%  ex       ld-2.24.so     [.] _dl_start
       0.00%  ex       ld-2.24.so     [.] do_lookup_x
       0.00%  ex       ld-2.24.so     [.] _start

The fix is not to fail, just warn if there's not unwind support compiled in.

Cc Hekuang <[email protected]>
Link http://lkml.kernel.org/n/[email protected] open here
Signed-off-by Jiri Olsa <[email protected]>
---
 tools/perf/util/unwind-libunwind.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
tools/perf/util/unwind-libunwind.c +1 -1
index 6d542a4e0648..8aef572d0889 100644
@@ -50,7 +50,7 @@ int unwind__prepare_access(struct thread *thread, struct map *map,
 
 	if (!ops) {
 		pr_err("unwind: target platform=%s is not supported\n", arch);
-		return -1;
+		return 0;
 	}
 out_register:
 	unwind__register_ops(thread, ops);
Signature · 1 line
2.9.4
merge bot
#1 lore raw
perf unwind: Do not fail due to missing unwind support
Commit-ID:  1934adf78e33fa69570a763c7ac5353212416bb0
Gitweb:     http://git.kernel.org/tip/1934adf78e33fa69570a763c7ac5353212416bb0
Author:     Jiri Olsa <[email protected]>
AuthorDate: Tue, 4 Jul 2017 15:11:31 +0200
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Tue, 4 Jul 2017 11:43:58 -0300

perf unwind: Do not fail due to missing unwind support

We currently fail the MMAP event processing if we don't have the MMAP event's specific arch unwind support compiled in.

That's wrong and can lead to unresolved mmaps in report output for 32bit binaries on 64bit server, like in this example on x86_64 server:

  $ cat ex.c
  int main(int argc, char **argv)
  {
          while (1) {}
  }
  $ gcc -o ex -m32 ex.c
  $ perf record ./ex
  ^C[ perf record: Woken up 2 times to write data ]
  [ perf record: Captured and wrote 0.371 MB perf.data (9322 samples) ]

Before:

  $ perf report --stdio

SNIP

  # Overhead  Command  Shared Object     Symbol
  # ........  .......  ................  ......................
  #
     100.00%  ex       [unknown]         [.] 0x00000000080483de
       0.00%  ex       [unknown]         [.] 0x00000000f76dba4f
       0.00%  ex       [unknown]         [.] 0x00000000f76e4c11
       0.00%  ex       [unknown]         [.] 0x00000000f76daa30

After:

  $ perf report --stdio

SNIP

  # Overhead  Command  Shared Object  Symbol
  # ........  .......  .............  ...............
  #
     100.00%  ex       ex             [.] main
       0.00%  ex       ld-2.24.so     [.] _dl_start
       0.00%  ex       ld-2.24.so     [.] do_lookup_x
       0.00%  ex       ld-2.24.so     [.] _start

The fix is not to fail, just warn if there's not unwind support compiled in.

Reported-by Michael Lyle <[email protected]>
Signed-off-by Jiri Olsa <[email protected]>
Tested-by Arnaldo Carvalho de Melo <[email protected]>
Cc David Ahern <[email protected]>
Cc He Kuang <[email protected]>
Cc Namhyung Kim <[email protected]>
Cc Peter Zijlstra <[email protected]>
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Arnaldo Carvalho de Melo <[email protected]>
---
 tools/perf/util/unwind-libunwind.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
tools/perf/util/unwind-libunwind.c +1 -1
index 6d542a4..8aef572 100644
@@ -50,7 +50,7 @@ int unwind__prepare_access(struct thread *thread, struct map *map,
 
 	if (!ops) {
 		pr_err("unwind: target platform=%s is not supported\n", arch);
-		return -1;
+		return 0;
 	}
 out_register:
 	unwind__register_ops(thread, ops);