perf symbols: Try the .debug/ DSO cache as a last resort

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2015-10-14 13:13 UTC #0 lore raw

Commit-ID:  dc38218e8b598a0092dae9715e603e9628203bec
Gitweb:     http://git.kernel.org/tip/dc38218e8b598a0092dae9715e603e9628203bec
Author:     Arnaldo Carvalho de Melo <[email protected]>
AuthorDate: Sun, 11 Oct 2015 17:17:24 -0300
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 12 Oct 2015 13:52:27 -0300

perf symbols: Try the .debug/ DSO cache as a last resort

Not as the first attempt at finding a vmlinux for the running kernel, this way we get a more informative filename to present in tools, it will check that the build-id is the same as the one previously loaded in the DSO in dso->build_id, reading from /sys/kernel/notes, for instance.

E.g. in the annotation TUI, going from 'perf top', for the scsi_sg_alloc kernel function, in the first line:

Before:

scsi_sg_alloc /root/.debug/.build-id/28/2777c262e6b3c0451375163c9a81c893218ab1

After:

scsi_sg_alloc /lib/modules/4.3.0-rc1+/build/vmlinux

And:

  # ls -la /root/.debug/.build-id/28/2777c262e6b3c0451375163c9a81c893218ab1
lrwxrwxrwx. 1 root root 81 Sep 22 16:11 /root/.debug/.build-id/28/2777c262e6b3c0451375163c9a81c893218ab1 -> ../../home/git/build/v4.3.0-rc1+/vmlinux/282777c262e6b3c0451375163c9a81c893218ab1
  # file ~/.debug/home/git/build/v4.3.0-rc1+/vmlinux/282777c262e6b3c0451375163c9a81c893218ab1
/root/.debug/home/git/build/v4.3.0-rc1+/vmlinux/282777c262e6b3c0451375163c9a81c893218ab1: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, BuildID[sha1]=282777c262e6b3c0451375163c9a81c893218ab1, not stripped
  #

The same as:

  # file /lib/modules/4.3.0-rc1+/build/vmlinux
/lib/modules/4.3.0-rc1+/build/vmlinux: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, BuildID[sha1]=282777c262e6b3c0451375163c9a81c893218ab1, not stripped

Furthermore:

  # sha256sum /lib/modules/4.3.0-rc1+/build/vmlinux
  e7a789bbdc61029ec09140c228e1dd651271f38ef0b8416c0b7d5ff727b98be2  /lib/modules/4.3.0-rc1+/build/vmlinux
  # sha256sum ~/.debug/home/git/build/v4.3.0-rc1+/vmlinux/282777c262e6b3c0451375163c9a81c893218ab1
  e7a789bbdc61029ec09140c228e1dd651271f38ef0b8416c0b7d5ff727b98be2  /root/.debug/home/git/build/v4.3.0-rc1+/vmlinux/282777c262e6b3c0451375163c9a81c893218ab1
  [root@zoo new]#

Cc Adrian Hunter <[email protected]>

Cc Borislav Petkov <[email protected]>

Cc David Ahern <[email protected]>

Cc Frederic Weisbecker <[email protected]>

Cc Jiri Olsa <[email protected]>

Cc Namhyung Kim <[email protected]>

Cc Stephane Eranian <[email protected]>

Cc Wang Nan <[email protected]>

Link http://lkml.kernel.org/n/[email protected] open here

Signed-off-by Arnaldo Carvalho de Melo <[email protected]>

---
 tools/perf/util/symbol.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

tools/perf/util/symbol.c +9 -9

index bcda43b..e7bf0c4 100644
@@ -1607,6 +1607,15 @@ int dso__load_vmlinux_path(struct dso *dso, struct map *map,
 	int i, err = 0;
 	char *filename = NULL;
 
+	pr_debug("Looking at the vmlinux_path (%d entries long)\n",
+		 vmlinux_path__nr_entries + 1);
+
+	for (i = 0; i < vmlinux_path__nr_entries; ++i) {
+		err = dso__load_vmlinux(dso, map, vmlinux_path[i], false, filter);
+		if (err > 0)
+			goto out;
+	}
+
 	if (!symbol_conf.ignore_vmlinux_buildid)
 		filename = dso__build_id_filename(dso, NULL, 0);
 	if (filename != NULL) {

@@ -1615,15 +1624,6 @@ int dso__load_vmlinux_path(struct dso *dso, struct map *map,
 			goto out;
 		free(filename);
 	}
-
-	pr_debug("Looking at the vmlinux_path (%d entries long)\n",
-		 vmlinux_path__nr_entries + 1);
-
-	for (i = 0; i < vmlinux_path__nr_entries; ++i) {
-		err = dso__load_vmlinux(dso, map, vmlinux_path[i], false, filter);
-		if (err > 0)
-			break;
-	}
 out:
 	return err;
 }