perf symbols: Fix ELF header errors during "perf kmem record"

The write_event() function in builtin-record.c writes out all
mmap()'d DSOs including non-ELF files like GNOME resource files
and such.

Therefore, check for ELF_K_ELF in filename__read_build_id()
before attempting to read the ELF header with gelf_getehdr().

Fixes the following error messages when running "perf kmem
record":

  penberg@penberg-laptop:~/src/linux/tools/perf$ perf kmem record
  ^C[ perf record: Woken up 2 times to write data ]
  [ perf record: Captured and wrote 0.753 MB perf.data (~32885 samples) ]
  filename__read_build_id: cannot get elf header.
  filename__read_build_id: cannot get elf header.
  filename__read_build_id: cannot get elf header.
  filename__read_build_id: cannot get elf header.
  filename__read_build_id: cannot get elf header.
  filename__read_build_id: cannot get elf header.
  filename__read_build_id: cannot get elf header.
  filename__read_build_id: cannot get elf header.
  filename__read_build_id: cannot get elf header.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1258885784-11709-1-git-send-email-penberg@cs.helsinki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 5 insertions, 0 deletions

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 86ec6c720f0f..f56158fb4dc9 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -921,6 +921,7 @@ int filename__read_build_id(const char *filename, void *bf, size_t size)
         GElf_Shdr shdr;
         Elf_Data *data;
         Elf_Scn *sec;
+        Elf_Kind ek;
         void *ptr;
         Elf *elf;
 
@@ -937,6 +938,10 @@ int filename__read_build_id(const char *filename, void *bf, size_t size)
                 goto out_close;
         }
 
+        ek = elf_kind(elf);
+        if (ek != ELF_K_ELF)
+                goto out_elf_end;
+
         if (gelf_getehdr(elf, &ehdr) == NULL) {
                 pr_err("%s: cannot get elf header.\n", __func__);
                 goto out_elf_end;