perf maps: Lookup maps in both intitial mountns and inner mountns.

If a process is in a mountns and has symbols in /tmp/perf-<pid>.map,
look first in the namespace using the tgid for the pidns that the
process might be in.  If the map isn't found there, try looking in the
mountns where perf is running, and use the tgid that's appropriate for
perf's pid namespace.  If all else fails, use the original pid.

This allows us to locate a symbol map file in the mount namespace, if it
was generated there.  However, we also try the tool's /tmp in case it's
there instead.

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/1499305693-1599-3-git-send-email-kjlx@templeofstupid.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 57 insertions, 13 deletions

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 60a9eaa372ef..21c97cc41cfc 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -19,7 +19,6 @@
 #include "strlist.h"
 #include "intlist.h"
 #include "namespaces.h"
-#include "vdso.h"
 #include "header.h"
 #include "path.h"
 #include "sane_ctype.h"
@@ -1327,14 +1326,15 @@ int dso__load_kallsyms(struct dso *dso, const char *filename,
 	return __dso__load_kallsyms(dso, filename, map, false);
 }
 
-static int dso__load_perf_map(struct dso *dso, struct map *map)
+static int dso__load_perf_map(const char *map_path, struct dso *dso,
+			      struct map *map)
 {
 	char *line = NULL;
 	size_t n;
 	FILE *file;
 	int nr_syms = 0;
 
-	file = fopen(dso->long_name, "r");
+	file = fopen(map_path, "r");
 	if (file == NULL)
 		goto out_failure;
 
@@ -1426,6 +1426,45 @@ static bool dso__is_compatible_symtab_type(struct dso *dso, bool kmod,
 	}
 }
 
+/* Checks for the existence of the perf-<pid>.map file in two different
+ * locations.  First, if the process is a separate mount namespace, check in
+ * that namespace using the pid of the innermost pid namespace.  If's not in a
+ * namespace, or the file can't be found there, try in the mount namespace of
+ * the tracing process using our view of its pid.
+ */
+static int dso__find_perf_map(char *filebuf, size_t bufsz,
+			      struct nsinfo **nsip)
+{
+	struct nscookie nsc;
+	struct nsinfo *nsi;
+	struct nsinfo *nnsi;
+	int rc = -1;
+
+	nsi = *nsip;
+
+	if (nsi->need_setns) {
+		snprintf(filebuf, bufsz, "/tmp/perf-%d.map", nsi->nstgid);
+		nsinfo__mountns_enter(nsi, &nsc);
+		rc = access(filebuf, R_OK);
+		nsinfo__mountns_exit(&nsc);
+		if (rc == 0)
+			return rc;
+	}
+
+	nnsi = nsinfo__copy(nsi);
+	if (nnsi) {
+		nsinfo__put(nsi);
+
+		nnsi->need_setns = false;
+		snprintf(filebuf, bufsz, "/tmp/perf-%d.map", nnsi->tgid);
+		*nsip = nnsi;
+		rc = 0;
+	}
+
+	return rc;
+}
+
+
 int dso__load(struct dso *dso, struct map *map)
 {
 	char *name;
@@ -1437,18 +1476,23 @@ int dso__load(struct dso *dso, struct map *map)
 	struct symsrc ss_[2];
 	struct symsrc *syms_ss = NULL, *runtime_ss = NULL;
 	bool kmod;
+	bool perfmap;
 	unsigned char build_id[BUILD_ID_SIZE];
 	struct nscookie nsc;
+	char newmapname[PATH_MAX];
+	const char *map_path = dso->long_name;
+
+	perfmap = strncmp(dso->name, "/tmp/perf-", 10) == 0;
+	if (perfmap) {
+		if (dso->nsinfo && (dso__find_perf_map(newmapname,
+		    sizeof(newmapname), &dso->nsinfo) == 0)) {
+			map_path = newmapname;
+		}
+	}
 
 	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;
@@ -1471,19 +1515,19 @@ int dso__load(struct dso *dso, struct map *map)
 
 	dso->adjust_symbols = 0;
 
-	if (strncmp(dso->name, "/tmp/perf-", 10) == 0) {
+	if (perfmap) {
 		struct stat st;
 
-		if (lstat(dso->name, &st) < 0)
+		if (lstat(map_path, &st) < 0)
 			goto out;
 
 		if (!symbol_conf.force && st.st_uid && (st.st_uid != geteuid())) {
 			pr_warning("File %s not owned by current user or root, "
-				   "ignoring it (use -f to override).\n", dso->name);
+				   "ignoring it (use -f to override).\n", map_path);
 			goto out;
 		}
 
-		ret = dso__load_perf_map(dso, map);
+		ret = dso__load_perf_map(map_path, dso, map);
 		dso->symtab_type = ret > 0 ? DSO_BINARY_TYPE__JAVA_JIT :
 					     DSO_BINARY_TYPE__NOT_FOUND;
 		goto out;