[PATCH 34/86] perf symbols: Find symbols in different mount namespace

Arnaldo Carvalho de Melo
2017-07-19T14:33:34Z

From: Krister Johansen <kjlx@templeofstupid.com>

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>
---
tools/perf/util/dso.c | 1 +
tools/perf/util/dso.h | 2 +
tools/perf/util/map.c | 2 +
tools/perf/util/namespaces.c | 127 +++++++++++++++++++++++++++++++++++++++++++
tools/perf/util/namespaces.h | 33 +++++++++++
tools/perf/util/symbol.c | 11 ++++
tools/perf/util/thread.c | 3 +
tools/perf/util/thread.h | 1 +
8 files changed, 180 insertions(+)

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 4e7ab611377a..beda40ed63b0 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -1236,6 +1236,7 @@ void dso__delete(struct dso *dso)
dso_cache__free(dso);
dso__free_a2l(dso);
zfree(&dso->symsrc_filename);
+ nsinfo__zput(dso->nsinfo);
pthread_mutex_destroy(&dso->lock);
free(dso);
}
diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index bd061ba7b47c..78ec637fc68b 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -10,6 +10,7 @@
#include <linux/types.h>
#include <linux/bitops.h>
#include "map.h"
+#include "namespaces.h"
#include "build-id.h"

enum dso_binary_type {
@@ -187,6 +188,7 @@ struct dso {
void *priv;
u64 db_id;
};
+ struct nsinfo *nsinfo;
refcount_t refcnt;
char name[0];
};
diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index 2179b2deb730..5dc60ca5a294 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -16,6 +16,7 @@
#include "machine.h"
#include <linux/string.h>
#include "srcline.h"
+#include "namespaces.h"
#include "unwind.h"

static void __maps__insert(struct maps *maps, struct map *map);
@@ -200,6 +201,7 @@ struct map *map__new(struct machine *machine, u64 start, u64 len,
if (type != MAP__FUNCTION)
dso__set_loaded(dso, map->type);
}
+ dso->nsinfo = nsinfo__get(thread->nsinfo);
dso__put(dso);
}
return map;
diff --git a/tools/perf/util/namespaces.c b/tools/perf/util/namespaces.c
index 67dcbcc73c7d..bcc6bb19cf10 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;
+ }
+}
diff --git a/tools/perf/util/namespaces.h b/tools/perf/util/namespaces.h
index 468f1e9a1484..b20f6ead7b2d 100644
--- a/tools/perf/util/namespaces.h
+++ b/tools/perf/util/namespaces.h
@@ -11,6 +11,7 @@

#include "../perf.h"
#include <linux/list.h>
+#include <linux/refcount.h>

struct namespaces_event;

@@ -23,4 +24,36 @@ struct namespaces {
struct namespaces *namespaces__new(struct namespaces_event *event);
void namespaces__free(struct namespaces *namespaces);

+struct nsinfo {
+ pid_t pid;
+ bool need_setns;
+ char *mntns_path;
+ refcount_t refcnt;
+};
+
+struct nscookie {
+ int oldns;
+ int newns;
+};
+
+void nsinfo__init(struct nsinfo *nsi);
+struct nsinfo *nsinfo__new(pid_t pid);
+void nsinfo__delete(struct nsinfo *nsi);
+
+struct nsinfo *nsinfo__get(struct nsinfo *nsi);
+void nsinfo__put(struct nsinfo *nsi);
+
+void nsinfo__mountns_enter(struct nsinfo *nsi, struct nscookie *nc);
+void nsinfo__mountns_exit(struct nscookie *nc);
+
+static inline void __nsinfo__zput(struct nsinfo **nsip)
+{
+ if (nsip) {
+ nsinfo__put(*nsip);
+ *nsip = NULL;
+ }
+}
+
+#define nsinfo__zput(nsi) __nsinfo__zput(&nsi)
+
#endif /* __PERF_NAMESPACES_H */
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index e7a98dbd2aed..60a9eaa372ef 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -18,6 +18,8 @@
#include "symbol.h"
#include "strlist.h"
#include "intlist.h"
+#include "namespaces.h"
+#include "vdso.h"
#include "header.h"
#include "path.h"
#include "sane_ctype.h"
@@ -1436,9 +1438,17 @@ int dso__load(struct dso *dso, struct map *map)
struct symsrc *syms_ss = NULL, *runtime_ss = NULL;
bool kmod;
unsigned char build_id[BUILD_ID_SIZE];
+ struct nscookie nsc;

+ nsinfo__mountns_enter(dso->nsinfo, &nsc);
pthread_mutex_lock(&dso->lock);

+ /* The vdso files always live in the host container, so don't go looking
+ * for them in the container's mount namespace.
+ */
+ if (dso__is_vdso(dso))
+ nsinfo__mountns_exit(&nsc);
+
/* check again under the dso->lock */
if (dso__loaded(dso, map->type)) {
ret = 1;
@@ -1584,6 +1594,7 @@ int dso__load(struct dso *dso, struct map *map)
out:
dso__set_loaded(dso, map->type);
pthread_mutex_unlock(&dso->lock);
+ nsinfo__mountns_exit(&nsc);

return ret;
}
diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index 378c418ca0c1..aee9a42102ba 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -59,6 +59,8 @@ struct thread *thread__new(pid_t pid, pid_t tid)
list_add(&comm->list, &thread->comm_list);
refcount_set(&thread->refcnt, 1);
RB_CLEAR_NODE(&thread->rb_node);
+ /* Thread holds first ref to nsdata. */
+ thread->nsinfo = nsinfo__new(pid);
}

return thread;
@@ -91,6 +93,7 @@ void thread__delete(struct thread *thread)
comm__free(comm);
}
unwind__finish_access(thread);
+ nsinfo__zput(thread->nsinfo);

free(thread);
}
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index 4eb849e9098f..cb1a5dd5c2b9 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -34,6 +34,7 @@ struct thread {

void *priv;
struct thread_stack *ts;
+ struct nsinfo *nsinfo;
#ifdef HAVE_LIBUNWIND_SUPPORT
void *addr_space;
struct unwind_libunwind_ops *unwind_libunwind_ops;
--
2.9.4