perf symbols: Add ability to find kcore in build-id cache

When no vmlinux is found, tools will use kallsyms and, if possible,
kcore.  Add the ability to find kcore in the build-id cache.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1381747424-3557-7-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index b2f60ddc864f408b10c16dd8d681cc62972619c3..76a9e933a7a568435de4b6889221d28f93a0a7a2 100644 (file)
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1401,6 +1401,105 @@ out:
        return err;
 }
 
+static int find_matching_kcore(struct map *map, char *dir, size_t dir_sz)
+{
+       char kallsyms_filename[PATH_MAX];
+       struct dirent *dent;
+       int ret = -1;
+       DIR *d;
+
+       d = opendir(dir);
+       if (!d)
+               return -1;
+
+       while (1) {
+               dent = readdir(d);
+               if (!dent)
+                       break;
+               if (dent->d_type != DT_DIR)
+                       continue;
+               scnprintf(kallsyms_filename, sizeof(kallsyms_filename),
+                         "%s/%s/kallsyms", dir, dent->d_name);
+               if (!validate_kcore_modules(kallsyms_filename, map)) {
+                       strlcpy(dir, kallsyms_filename, dir_sz);
+                       ret = 0;
+                       break;
+               }
+       }
+
+       closedir(d);
+
+       return ret;
+}
+
+static char *dso__find_kallsyms(struct dso *dso, struct map *map)
+{
+       u8 host_build_id[BUILD_ID_SIZE];
+       char sbuild_id[BUILD_ID_SIZE * 2 + 1];
+       bool is_host = false;
+       char path[PATH_MAX];
+
+       if (!dso->has_build_id) {
+               /*
+                * Last resort, if we don't have a build-id and couldn't find
+                * any vmlinux file, try the running kernel kallsyms table.
+                */
+               goto proc_kallsyms;
+       }
+
+       if (sysfs__read_build_id("/sys/kernel/notes", host_build_id,
+                                sizeof(host_build_id)) == 0)
+               is_host = dso__build_id_equal(dso, host_build_id);
+
+       build_id__sprintf(dso->build_id, sizeof(dso->build_id), sbuild_id);
+
+       /* Use /proc/kallsyms if possible */
+       if (is_host) {
+               DIR *d;
+               int fd;
+
+               /* If no cached kcore go with /proc/kallsyms */
+               scnprintf(path, sizeof(path), "%s/[kernel.kcore]/%s",
+                         buildid_dir, sbuild_id);
+               d = opendir(path);
+               if (!d)
+                       goto proc_kallsyms;
+               closedir(d);
+
+               /*
+                * Do not check the build-id cache, until we know we cannot use
+                * /proc/kcore.
+                */
+               fd = open("/proc/kcore", O_RDONLY);
+               if (fd != -1) {
+                       close(fd);
+                       /* If module maps match go with /proc/kallsyms */
+                       if (!validate_kcore_modules("/proc/kallsyms", map))
+                               goto proc_kallsyms;
+               }
+
+               /* Find kallsyms in build-id cache with kcore */
+               if (!find_matching_kcore(map, path, sizeof(path)))
+                       return strdup(path);
+
+               goto proc_kallsyms;
+       }
+
+       scnprintf(path, sizeof(path), "%s/[kernel.kallsyms]/%s",
+                 buildid_dir, sbuild_id);
+
+       if (access(path, F_OK)) {
+               pr_err("No kallsyms or vmlinux with build-id %s was found\n",
+                      sbuild_id);
+               return NULL;
+       }
+
+       return strdup(path);
+
+proc_kallsyms:
+       return strdup("/proc/kallsyms");
+}
+
 static int dso__load_kernel_sym(struct dso *dso, struct map *map,
                                symbol_filter_t filter)
 {
@@ -1449,51 +1548,11 @@ static int dso__load_kernel_sym(struct dso *dso, struct map *map,
        if (symbol_conf.symfs[0] != 0)
                return -1;
 
-       /*
-        * Say the kernel DSO was created when processing the build-id header table,
-        * we have a build-id, so check if it is the same as the running kernel,
-        * using it if it is.
-        */
-       if (dso->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) {
-                       if (dso__build_id_equal(dso, kallsyms_build_id)) {
-                               kallsyms_filename = "/proc/kallsyms";
-                               goto do_kallsyms;
-                       }
-               }
-               /*
-                * Now look if we have it on the build-id cache in
-                * $HOME/.debug/[kernel.kallsyms].
-                */
-               build_id__sprintf(dso->build_id, sizeof(dso->build_id),
-                                 sbuild_id);
-
-               if (asprintf(&kallsyms_allocated_filename,
-                            "%s/.debug/[kernel.kallsyms]/%s",
-                            getenv("HOME"), sbuild_id) == -1) {
-                       pr_err("Not enough memory for kallsyms file lookup\n");
-                       return -1;
-               }
-
-               kallsyms_filename = kallsyms_allocated_filename;
+       kallsyms_allocated_filename = dso__find_kallsyms(dso, map);
+       if (!kallsyms_allocated_filename)
+               return -1;
 
-               if (access(kallsyms_filename, F_OK)) {
-                       pr_err("No kallsyms or vmlinux with build-id %s "
-                              "was found\n", sbuild_id);
-                       free(kallsyms_allocated_filename);
-                       return -1;
-               }
-       } else {
-               /*
-                * Last resort, if we don't have a build-id and couldn't find
-                * any vmlinux file, try the running kernel kallsyms table.
-                */
-               kallsyms_filename = "/proc/kallsyms";
-       }
+       kallsyms_filename = kallsyms_allocated_filename;
 
 do_kallsyms:
        err = dso__load_kallsyms(dso, kallsyms_filename, map, filter);