[PATCH 1/8] perf symbols: Try the .debug/ DSO cache as a last resort

From: Arnaldo Carvalho de Melo
Date: Tue Oct 13 2015 - 15:44:37 EST


From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

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 <adrian.hunter@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-9y42ikzq3jisiddoi6f07n8z@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/util/symbol.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index bcda43bee4d4..e7bf0c46918d 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -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;
}
--
2.1.0

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