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, 35 insertions, 13 deletions

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 71d23e1e30e8..ae61e9f4d6eb 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -383,13 +383,14 @@ size_t dso__fprintf(struct dso *self, enum map_type type, FILE *fp)
         return ret;
 }
 
-int kallsyms__parse(void *arg, int (*process_symbol)(void *arg, const char *name,
+int kallsyms__parse(const char *filename, void *arg,
+                    int (*process_symbol)(void *arg, const char *name,
                                                      char type, u64 start))
 {
         char *line = NULL;
         size_t n;
         int err = 0;
-        FILE *file = fopen("/proc/kallsyms", "r");
+        FILE *file = fopen(filename, "r");
 
         if (file == NULL)
                 goto out_failure;
@@ -466,10 +467,11 @@ static int map__process_kallsym_symbol(void *arg, const char *name,
  * so that we can in the next step set the symbol ->end address and then
  * call kernel_maps__split_kallsyms.
  */
-static int dso__load_all_kallsyms(struct dso *self, struct map *map)
+static int dso__load_all_kallsyms(struct dso *self, const char *filename,
+                                  struct map *map)
 {
         struct process_kallsyms_args args = { .map = map, .dso = self, };
-        return kallsyms__parse(&args, map__process_kallsym_symbol);
+        return kallsyms__parse(filename, &args, map__process_kallsym_symbol);
 }
 
 /*
@@ -556,10 +558,10 @@ discard_symbol:		rb_erase(&pos->rb_node, root);
 }
 
 
-static int dso__load_kallsyms(struct dso *self, struct map *map,
+static int dso__load_kallsyms(struct dso *self, const char *filename, struct map *map,
                               struct perf_session *session, symbol_filter_t filter)
 {
-        if (dso__load_all_kallsyms(self, map) < 0)
+        if (dso__load_all_kallsyms(self, filename, map) < 0)
                 return -1;
 
         symbols__fixup_end(&self->symbols[map->type]);
@@ -1580,7 +1582,8 @@ static int dso__load_kernel_sym(struct dso *self, struct map *map,
                                 struct perf_session *session, symbol_filter_t filter)
 {
         int err;
-        bool is_kallsyms;
+        const char *kallsyms_filename = NULL;
+        char *kallsyms_allocated_filename = NULL;
 
         if (vmlinux_path != NULL) {
                 int i;
@@ -1606,19 +1609,37 @@ static int dso__load_kernel_sym(struct dso *self, struct map *map,
          */
         if (self->has_build_id) {
                 u8 kallsyms_build_id[BUILD_ID_SIZE];
+                char sbuild_id[BUILD_ID_SIZE * 2 + 1];
 
                 if (sysfs__read_build_id("/sys/kernel/notes", kallsyms_build_id,
                                          sizeof(kallsyms_build_id)) == 0) {
-                        is_kallsyms = dso__build_id_equal(self, kallsyms_build_id);
-                        if (is_kallsyms)
+                        if (dso__build_id_equal(self, kallsyms_build_id)) {
+                                kallsyms_filename = "/proc/kallsyms";
                                 goto do_kallsyms;
+                        }
                 }
+
+                build_id__sprintf(self->build_id, sizeof(self->build_id),
+                                  sbuild_id);
+
+                if (asprintf(&kallsyms_allocated_filename,
+                             "%s/.debug/[kernel.kallsyms]/%s",
+                             getenv("HOME"), sbuild_id) != -1) {
+                        if (access(kallsyms_filename, F_OK)) {
+                                kallsyms_filename = kallsyms_allocated_filename;
+                                goto do_kallsyms;
+                        }
+                        free(kallsyms_allocated_filename);
+                        kallsyms_allocated_filename = NULL;
+                }
+
                 goto do_vmlinux;
         }
 
-        is_kallsyms = self->long_name[0] == '[';
-        if (is_kallsyms)
+        if (self->long_name[0] == '[') {
+                kallsyms_filename = "/proc/kallsyms";
                 goto do_kallsyms;
+        }
 
 do_vmlinux:
         err = dso__load_vmlinux(self, map, session, self->long_name, filter);
@@ -1629,9 +1650,10 @@ do_vmlinux:
                 pr_info("The file %s cannot be used, "
                         "trying to use /proc/kallsyms...", self->long_name);
 do_kallsyms:
-                err = dso__load_kallsyms(self, map, session, filter);
-                if (err > 0 && !is_kallsyms)
+                err = dso__load_kallsyms(self, kallsyms_filename, map, session, filter);
+                if (err > 0 && kallsyms_filename == NULL)
                         dso__set_long_name(self, strdup("[kernel.kallsyms]"));
+                free(kallsyms_allocated_filename);
         }
 
         if (err > 0) {