perf symbols: Cache /proc/kallsyms files by build-id

So that when we don't have a vmlinux handy we can store the
kallsyms for later use by 'perf report'.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1263501006-14185-3-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 11 insertions, 4 deletions

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index b31e0ae4b8db..1b65fed0dd2d 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -237,11 +237,13 @@ static int dso__cache_build_id(struct dso *self, const char *debugdir)
         char *filename = malloc(size),
              *linkname = malloc(size), *targetname, *sbuild_id;
         int len, err = -1;
+        bool is_kallsyms = self->kernel && self->long_name[0] != '/';
 
         if (filename == NULL || linkname == NULL)
                 goto out_free;
 
-        len = snprintf(filename, size, "%s%s", debugdir, self->long_name);
+        len = snprintf(filename, size, "%s%s%s",
+                       debugdir, is_kallsyms ? "/" : "", self->long_name);
         if (mkdir_p(filename, 0755))
                 goto out_free;
 
@@ -249,9 +251,14 @@ static int dso__cache_build_id(struct dso *self, const char *debugdir)
         sbuild_id = filename + len;
         build_id__sprintf(self->build_id, sizeof(self->build_id), sbuild_id);
 
-        if (access(filename, F_OK) && link(self->long_name, filename) &&
-            copyfile(self->long_name, filename))
-                goto out_free;
+        if (access(filename, F_OK)) {
+                if (is_kallsyms) {
+                         if (copyfile("/proc/kallsyms", filename))
+                                goto out_free;
+                } else if (link(self->long_name, filename) &&
+                           copyfile(self->long_name, filename))
+                        goto out_free;
+        }
 
         len = snprintf(linkname, size, "%s/.build-id/%.2s",
                        debugdir, sbuild_id);