perf symbols: Find symbols in different mount namespace
Teach perf how to resolve symbols from binaries that are in a different
mount namespace from the tool. This allows perf to generate meaningful
stack traces even if the binary resides in a different mount namespace
from the tool.
Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
Tested-by: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas-Mich Richter <tmricht@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1499305693-1599-2-git-send-email-kjlx@templeofstupid.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/namespaces.c b/tools/perf/util/namespaces.c
index 67dcbcc..bcc6bb1 100644
--- a/tools/perf/util/namespaces.c
+++ b/tools/perf/util/namespaces.c
@@ -9,9 +9,13 @@
#include "namespaces.h"
#include "util.h"
#include "event.h"
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sched.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
+#include <unistd.h>
struct namespaces *namespaces__new(struct namespaces_event *event)
{
@@ -35,3 +39,126 @@ void namespaces__free(struct namespaces *namespaces)
{
free(namespaces);
}
+
+void nsinfo__init(struct nsinfo *nsi)
+{
+ char oldns[PATH_MAX];
+ char *newns = NULL;
+ struct stat old_stat;
+ struct stat new_stat;
+
+ if (snprintf(oldns, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX)
+ return;
+
+ if (asprintf(&newns, "/proc/%d/ns/mnt", nsi->pid) == -1)
+ return;
+
+ if (stat(oldns, &old_stat) < 0)
+ goto out;
+
+ if (stat(newns, &new_stat) < 0)
+ goto out;
+
+ /* Check if the mount namespaces differ, if so then indicate that we
+ * want to switch as part of looking up dso/map data.
+ */
+ if (old_stat.st_ino != new_stat.st_ino) {
+ nsi->need_setns = true;
+ nsi->mntns_path = newns;
+ newns = NULL;
+ }
+
+out:
+ free(newns);
+}
+
+struct nsinfo *nsinfo__new(pid_t pid)
+{
+ struct nsinfo *nsi = calloc(1, sizeof(*nsi));
+
+ if (nsi != NULL) {
+ nsi->pid = pid;
+ nsi->need_setns = false;
+ nsinfo__init(nsi);
+ refcount_set(&nsi->refcnt, 1);
+ }
+
+ return nsi;
+}
+
+void nsinfo__delete(struct nsinfo *nsi)
+{
+ zfree(&nsi->mntns_path);
+ free(nsi);
+}
+
+struct nsinfo *nsinfo__get(struct nsinfo *nsi)
+{
+ if (nsi)
+ refcount_inc(&nsi->refcnt);
+ return nsi;
+}
+
+void nsinfo__put(struct nsinfo *nsi)
+{
+ if (nsi && refcount_dec_and_test(&nsi->refcnt))
+ nsinfo__delete(nsi);
+}
+
+void nsinfo__mountns_enter(struct nsinfo *nsi, struct nscookie *nc)
+{
+ char curpath[PATH_MAX];
+ int oldns = -1;
+ int newns = -1;
+
+ if (nc == NULL)
+ return;
+
+ nc->oldns = -1;
+ nc->newns = -1;
+
+ if (!nsi || !nsi->need_setns)
+ return;
+
+ if (snprintf(curpath, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX)
+ return;
+
+ oldns = open(curpath, O_RDONLY);
+ if (oldns < 0)
+ return;
+
+ newns = open(nsi->mntns_path, O_RDONLY);
+ if (newns < 0)
+ goto errout;
+
+ if (setns(newns, CLONE_NEWNS) < 0)
+ goto errout;
+
+ nc->oldns = oldns;
+ nc->newns = newns;
+ return;
+
+errout:
+ if (oldns > -1)
+ close(oldns);
+ if (newns > -1)
+ close(newns);
+}
+
+void nsinfo__mountns_exit(struct nscookie *nc)
+{
+ if (nc == NULL || nc->oldns == -1 || nc->newns == -1)
+ return;
+
+ setns(nc->oldns, CLONE_NEWNS);
+
+ if (nc->oldns > -1) {
+ close(nc->oldns);
+ nc->oldns = -1;
+ }
+
+ if (nc->newns > -1) {
+ close(nc->newns);
+ nc->newns = -1;
+ }
+}
