Merge tag 'perf-core-for-mingo-20160615' of git://git.kernel.org/pub/scm/linux/kernel...

[deliverable/linux.git] / tools / perf / util / symbol.c

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 20f9cb32b703cd10330fa80ed328a16126a59a04..09c5c34ae38dd08ac21f92572ffd52def4440bd1 100644 (file)
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1641,6 +1641,20 @@ static int find_matching_kcore(struct map *map, char *dir, size_t dir_sz)
        return ret;
 }
 
+/*
+ * Use open(O_RDONLY) to check readability directly instead of access(R_OK)
+ * since access(R_OK) only checks with real UID/GID but open() use effective
+ * UID/GID and actual capabilities (e.g. /proc/kcore requires CAP_SYS_RAWIO).
+ */
+static bool filename__readable(const char *file)
+{
+       int fd = open(file, O_RDONLY);
+       if (fd < 0)
+               return false;
+       close(fd);
+       return true;
+}
+
 static char *dso__find_kallsyms(struct dso *dso, struct map *map)
 {
        u8 host_build_id[BUILD_ID_SIZE];
@@ -1660,58 +1674,43 @@ static char *dso__find_kallsyms(struct dso *dso, struct map *map)
                                 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);
-
-       scnprintf(path, sizeof(path), "%s/%s/%s", buildid_dir,
-                 DSO__NAME_KCORE, sbuild_id);
-
-       /* Use /proc/kallsyms if possible */
+       /* Try a fast path for /proc/kallsyms if possible */
        if (is_host) {
-               DIR *d;
-               int fd;
-
-               /* If no cached kcore go with /proc/kallsyms */
-               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.
+                * Do not check the build-id cache, unless we know we cannot use
+                * /proc/kcore or module maps don't match to /proc/kallsyms.
+                * To check readability of /proc/kcore, do not use access(R_OK)
+                * since /proc/kcore requires CAP_SYS_RAWIO to read and access
+                * can't check it.
                 */
-               fd = open("/proc/kcore", O_RDONLY);
-               if (fd != -1) {
-                       close(fd);
-                       /* If module maps match go with /proc/kallsyms */
-                       if (!validate_kcore_addresses("/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;
+               if (filename__readable("/proc/kcore") &&
+                   !validate_kcore_addresses("/proc/kallsyms", map))
+                       goto proc_kallsyms;
        }
 
+       build_id__sprintf(dso->build_id, sizeof(dso->build_id), sbuild_id);
+
        /* Find kallsyms in build-id cache with kcore */
+       scnprintf(path, sizeof(path), "%s/%s/%s",
+                 buildid_dir, DSO__NAME_KCORE, sbuild_id);
+
        if (!find_matching_kcore(map, path, sizeof(path)))
                return strdup(path);
 
-       scnprintf(path, sizeof(path), "%s/%s/%s",
-                 buildid_dir, DSO__NAME_KALLSYMS, sbuild_id);
+       /* Use current /proc/kallsyms if possible */
+       if (is_host) {
+proc_kallsyms:
+               return strdup("/proc/kallsyms");
+       }
 
-       if (access(path, F_OK)) {
+       /* Finally, find a cache of kallsyms */
+       if (!build_id_cache__kallsyms_path(sbuild_id, path, sizeof(path))) {
                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,
@@ -1933,17 +1932,17 @@ int setup_intlist(struct intlist **list, const char *list_str,
 static bool symbol__read_kptr_restrict(void)
 {
        bool value = false;
+       FILE *fp = fopen("/proc/sys/kernel/kptr_restrict", "r");
 
-       if (geteuid() != 0) {
-               FILE *fp = fopen("/proc/sys/kernel/kptr_restrict", "r");
-               if (fp != NULL) {
-                       char line[8];
+       if (fp != NULL) {
+               char line[8];
 
-                       if (fgets(line, sizeof(line), fp) != NULL)
-                               value = atoi(line) != 0;
+               if (fgets(line, sizeof(line), fp) != NULL)
+                       value = (geteuid() != 0) ?
+                                       (atoi(line) != 0) :
+                                       (atoi(line) == 2);
 
-                       fclose(fp);
-               }
+               fclose(fp);
        }
 
        return value;