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Message-ID: <20181120112352.GE8967@krava>
Date: Tue, 20 Nov 2018 12:23:52 +0100
From: Jiri Olsa <jolsa@...hat.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Jiri Olsa <jolsa@...nel.org>,
Krister Johansen <kjlx@...pleofstupid.com>,
lkml <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: [PATCHv2] perf tools: Restore proper cwd on return from mnt ns
On Tue, Nov 20, 2018 at 11:56:18AM +0100, Jiri Olsa wrote:
> On Mon, Nov 19, 2018 at 08:10:06AM -0800, Arnaldo Carvalho de Melo wrote:
> > Em Thu, Nov 01, 2018 at 06:00:01PM +0100, Jiri Olsa escreveu:
> > > Adding the current working directory to be part of the cookie
> > > and restoring it in the nsinfo__mountns_exit call.
> >
> > > diff --git a/tools/perf/util/namespaces.c b/tools/perf/util/namespaces.c
> > > index cf8bd123cf73..fb0458b7e6aa 100644
> > > --- a/tools/perf/util/namespaces.c
> > > +++ b/tools/perf/util/namespaces.c
> >
> > > @@ -199,9 +201,13 @@ void nsinfo__mountns_enter(struct nsinfo *nsi,
> > > if (snprintf(curpath, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX)
> > > return;
> >
> > > + oldcwd = get_current_dir_name();
> >
> > Breaks the build with bionic (Android), where get_current_dir_name() is
> > not available:
> >
> > /tmp/build/perf/libperf.a(libperf-in.o):hist.c:function nsinfo__mountns_enter: error: undefined reference to 'get_current_dir_name'
> > collect2: error: ld returned 1 exit status
> > Makefile.perf:534: recipe for target '/tmp/build/perf/perf' failed
> > make[2]: *** [/tmp/build/perf/perf] Error 1
> > Makefile.perf:206: recipe for target 'sub-make' failed
> > make[1]: *** [sub-make] Error 2
> > Makefile:69: recipe for target 'all' failed
> > make: *** [all] Error 2
> > make: Leaving directory '/git/linux/tools/perf'
> > [root@...enth ~]#
> >
> > The container builds are ongoing, its possoble that this becomes an
> > issue in uCLibc, wasn't on musl libc (Alpine Linux).
>
> will check, thanks
how about this one?
thanks,
jirka
---
When reporting on 'record' server we try to retrieve/use
the mnt namespace of the profiled tasks. We use following
API with cookie to hold the return namespace, roughly:
nsinfo__mountns_enter(struct nsinfo *nsi, struct nscookie *nc)
setns(newns, 0);
...
new ns related open..
...
nsinfo__mountns_exit(struct nscookie *nc)
setns(nc->oldns)
Once finished we setns to old namespace, which also sets the
current working directory (cwd) to "/", trashing the cwd we had.
This is mostly fine, because we use absolute paths almost everywhere,
but it screws up perf diff:
# perf diff
failed to open perf.data: No such file or directory (try 'perf record' first)
...
Adding the current working directory to be part of the cookie
and restoring it in the nsinfo__mountns_exit call.
v2: get rid of _GNU_SOURCE get_current_dir_name call [acme]
Cc: Krister Johansen <kjlx@...pleofstupid.com>
Fixes: 843ff37bb59e ("perf symbols: Find symbols in different mount namespace")
Link: http://lkml.kernel.org/n/tip-zg3vz7kjr86cco7lo91v8yhj@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
tools/perf/util/namespaces.c | 25 +++++++++++++++++++++++--
tools/perf/util/namespaces.h | 1 +
2 files changed, 24 insertions(+), 2 deletions(-)
diff --git a/tools/perf/util/namespaces.c b/tools/perf/util/namespaces.c
index cf8bd123cf73..b759a7ad87e7 100644
--- a/tools/perf/util/namespaces.c
+++ b/tools/perf/util/namespaces.c
@@ -18,6 +18,7 @@
#include <stdio.h>
#include <string.h>
#include <unistd.h>
+#include <asm/bug.h>
struct namespaces *namespaces__new(struct namespaces_event *event)
{
@@ -180,12 +181,20 @@ void nsinfo__put(struct nsinfo *nsi)
nsinfo__delete(nsi);
}
+static char *get_current_dir(void)
+{
+ char path[PATH_MAX];
+
+ return getcwd(path, PATH_MAX) ? strdup(path) : NULL;
+}
+
void nsinfo__mountns_enter(struct nsinfo *nsi,
struct nscookie *nc)
{
char curpath[PATH_MAX];
int oldns = -1;
int newns = -1;
+ char *oldcwd = NULL;
if (nc == NULL)
return;
@@ -199,9 +208,13 @@ void nsinfo__mountns_enter(struct nsinfo *nsi,
if (snprintf(curpath, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX)
return;
+ oldcwd = get_current_dir();
+ if (!oldcwd)
+ return;
+
oldns = open(curpath, O_RDONLY);
if (oldns < 0)
- return;
+ goto errout;
newns = open(nsi->mntns_path, O_RDONLY);
if (newns < 0)
@@ -210,11 +223,14 @@ void nsinfo__mountns_enter(struct nsinfo *nsi,
if (setns(newns, CLONE_NEWNS) < 0)
goto errout;
+ nc->oldcwd = oldcwd;
nc->oldns = oldns;
nc->newns = newns;
return;
errout:
+ if (oldcwd)
+ free(oldcwd);
if (oldns > -1)
close(oldns);
if (newns > -1)
@@ -223,11 +239,16 @@ void nsinfo__mountns_enter(struct nsinfo *nsi,
void nsinfo__mountns_exit(struct nscookie *nc)
{
- if (nc == NULL || nc->oldns == -1 || nc->newns == -1)
+ if (nc == NULL || nc->oldns == -1 || nc->newns == -1 || !nc->oldcwd)
return;
setns(nc->oldns, CLONE_NEWNS);
+ if (nc->oldcwd) {
+ WARN_ON_ONCE(chdir(nc->oldcwd));
+ free(nc->oldcwd);
+ }
+
if (nc->oldns > -1) {
close(nc->oldns);
nc->oldns = -1;
diff --git a/tools/perf/util/namespaces.h b/tools/perf/util/namespaces.h
index cae1a9a39722..d5f46c09ea31 100644
--- a/tools/perf/util/namespaces.h
+++ b/tools/perf/util/namespaces.h
@@ -38,6 +38,7 @@ struct nsinfo {
struct nscookie {
int oldns;
int newns;
+ char *oldcwd;
};
int nsinfo__init(struct nsinfo *nsi);
--
2.17.2
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