[PATCH] perf tools: Restore proper cwd on return from mnt ns

[PATCH] perf tools: Restore proper cwd on return from mnt ns

[Jiri Olsa]

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.

Cc: Krister Johansen <kjlx@templeofstupid.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@kernel.org>
---
 tools/perf/util/namespaces.c | 18 ++++++++++++++++--
 tools/perf/util/namespaces.h |  1 +
 2 files changed, 17 insertions(+), 2 deletions(-)

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
@@ -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)
 {
@@ -186,6 +187,7 @@ void nsinfo__mountns_enter(struct nsinfo *nsi,
 	char curpath[PATH_MAX];
 	int oldns = -1;
 	int newns = -1;
+	char *oldcwd = NULL;
 
 	if (nc == NULL)
 		return;
@@ -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();
+	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 +216,14 @@ 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 +232,16 @@ 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

Re: [PATCH] perf tools: Restore proper cwd on return from mnt ns

[Jiri Olsa]

ping

jirka

On Thu, Nov 01, 2018 at 06:00:01PM +0100, Jiri Olsa wrote:
> 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.
> 
> Cc: Krister Johansen <kjlx@templeofstupid.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@kernel.org>
> ---
>  tools/perf/util/namespaces.c | 18 ++++++++++++++++--
>  tools/perf/util/namespaces.h |  1 +
>  2 files changed, 17 insertions(+), 2 deletions(-)
> 
> 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
> @@ -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)
>  {
> @@ -186,6 +187,7 @@ void nsinfo__mountns_enter(struct nsinfo *nsi,
>  	char curpath[PATH_MAX];
>  	int oldns = -1;
>  	int newns = -1;
> +	char *oldcwd = NULL;
>  
>  	if (nc == NULL)
>  		return;
> @@ -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();
> +	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 +216,14 @@ 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 +232,16 @@ 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
> 

Re: [PATCH] perf tools: Restore proper cwd on return from mnt ns

[Arnaldo Carvalho de Melo]

Em Thu, Nov 01, 2018 at 06:00:01PM +0100, Jiri Olsa escreveu:
> 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.
 
> Cc: Krister Johansen <kjlx@templeofstupid.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@kernel.org>
> ---
>  tools/perf/util/namespaces.c | 18 ++++++++++++++++--
>  tools/perf/util/namespaces.h |  1 +
>  2 files changed, 17 insertions(+), 2 deletions(-)
> 
> 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
> @@ -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)
>  {
> @@ -186,6 +187,7 @@ void nsinfo__mountns_enter(struct nsinfo *nsi,
>  	char curpath[PATH_MAX];
>  	int oldns = -1;
>  	int newns = -1;
> +	char *oldcwd = NULL;
>  
>  	if (nc == NULL)
>  		return;
> @@ -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();
> +	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 +216,14 @@ 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);

Applied, and while at it I removed the needless if in the above two
lines.

>  	if (oldns > -1)
>  		close(oldns);
>  	if (newns > -1)
> @@ -223,11 +232,16 @@ 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

Re: [PATCH] perf tools: Restore proper cwd on return from mnt ns

[Arnaldo Carvalho de Melo]

Em Fri, Nov 16, 2018 at 10:31:43AM -0800, Arnaldo Carvalho de Melo escreveu:
> Em Thu, Nov 01, 2018 at 06:00:01PM +0100, Jiri Olsa escreveu:
> > 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.
>  
> > Cc: Krister Johansen <kjlx@templeofstupid.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@kernel.org>
> > ---
> >  tools/perf/util/namespaces.c | 18 ++++++++++++++++--
> >  tools/perf/util/namespaces.h |  1 +
> >  2 files changed, 17 insertions(+), 2 deletions(-)
> > 
> > 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
> > @@ -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)
> >  {
> > @@ -186,6 +187,7 @@ void nsinfo__mountns_enter(struct nsinfo *nsi,
> >  	char curpath[PATH_MAX];
> >  	int oldns = -1;
> >  	int newns = -1;
> > +	char *oldcwd = NULL;
> >  
> >  	if (nc == NULL)
> >  		return;
> > @@ -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();
> > +	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 +216,14 @@ 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);
> 
> Applied, and while at it I removed the needless if in the above two
> lines.
> 
> >  	if (oldns > -1)
> >  		close(oldns);
> >  	if (newns > -1)
> > @@ -223,11 +232,16 @@ 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);
> > +	}
> > +

Also changed the above to zfree(&nc->oldcwd) as this is in a struct
member, that is not freed by the freeing caller
(nsinfo__mountns_exit()), to avoid later possible use-after-free (I
haven't checked if it _actually_ happens with the current codebase, but
it could) also to match the following block, where the resource is
released and then the handler is invalidated.

- Arnaldo

> >  	if (nc->oldns > -1) {
> >  		close(nc->oldns);
> >  		nc->oldns = -1;

Re: [PATCH] perf tools: Restore proper cwd on return from mnt ns

[Jiri Olsa]

On Fri, Nov 16, 2018 at 10:42:45AM -0800, Arnaldo Carvalho de Melo wrote:
> Em Fri, Nov 16, 2018 at 10:31:43AM -0800, Arnaldo Carvalho de Melo escreveu:
> > Em Thu, Nov 01, 2018 at 06:00:01PM +0100, Jiri Olsa escreveu:
> > > 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.
> >  
> > > Cc: Krister Johansen <kjlx@templeofstupid.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@kernel.org>
> > > ---
> > >  tools/perf/util/namespaces.c | 18 ++++++++++++++++--
> > >  tools/perf/util/namespaces.h |  1 +
> > >  2 files changed, 17 insertions(+), 2 deletions(-)
> > > 
> > > 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
> > > @@ -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)
> > >  {
> > > @@ -186,6 +187,7 @@ void nsinfo__mountns_enter(struct nsinfo *nsi,
> > >  	char curpath[PATH_MAX];
> > >  	int oldns = -1;
> > >  	int newns = -1;
> > > +	char *oldcwd = NULL;
> > >  
> > >  	if (nc == NULL)
> > >  		return;
> > > @@ -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();
> > > +	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 +216,14 @@ 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);

right, ok

> > 
> > Applied, and while at it I removed the needless if in the above two
> > lines.
> > 
> > >  	if (oldns > -1)
> > >  		close(oldns);
> > >  	if (newns > -1)
> > > @@ -223,11 +232,16 @@ 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);
> > > +	}
> > > +
> 
> Also changed the above to zfree(&nc->oldcwd) as this is in a struct
> member, that is not freed by the freeing caller
> (nsinfo__mountns_exit()), to avoid later possible use-after-free (I
> haven't checked if it _actually_ happens with the current codebase, but
> it could) also to match the following block, where the resource is
> released and then the handler is invalidated.

great, thanks

jirka

Re: [PATCH] perf tools: Restore proper cwd on return from mnt ns

[Arnaldo Carvalho de Melo]

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@seventh ~]# 

The container builds are ongoing, its possoble that this becomes an
issue in uCLibc, wasn't on musl libc (Alpine Linux).

- Arnaldo

Re: [PATCH] perf tools: Restore proper cwd on return from mnt ns

[Jiri Olsa]

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@seventh ~]# 
> 
> The container builds are ongoing, its possoble that this becomes an
> issue in uCLibc, wasn't on musl libc (Alpine Linux).

will check, thanks

jirka

[PATCHv2] perf tools: Restore proper cwd on return from mnt ns

[Jiri Olsa]

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@seventh ~]# 
> > 
> > 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@templeofstupid.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@kernel.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

Re: [PATCH] perf tools: Restore proper cwd on return from mnt ns

[Arnaldo Carvalho de Melo]

Em Tue, Nov 20, 2018 at 11:56:18AM +0100, Jiri Olsa escreveu:
> 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@seventh ~]# 
> > 
> > The container builds are ongoing, its possoble that this becomes an
> > issue in uCLibc, wasn't on musl libc (Alpine Linux).
> 
> will check, thanks

I fixed this already, by adding a test for that get_current_dir_name()
function and a simple implementation based on strdup(getcwd(bf)), take a
look at my perf/urgent branch 

- Arnaldo

Re: [PATCH] perf tools: Restore proper cwd on return from mnt ns

[Jiri Olsa]

On Tue, Nov 20, 2018 at 12:56:04PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Tue, Nov 20, 2018 at 11:56:18AM +0100, Jiri Olsa escreveu:
> > 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@seventh ~]# 
> > > 
> > > The container builds are ongoing, its possoble that this becomes an
> > > issue in uCLibc, wasn't on musl libc (Alpine Linux).
> > 
> > will check, thanks
> 
> I fixed this already, by adding a test for that get_current_dir_name()
> function and a simple implementation based on strdup(getcwd(bf)), take a
> look at my perf/urgent branch 

ok, I saw it.. but it seems little too much for a single function to me

jirka

[tip:perf/urgent] perf tools: Restore proper cwd on return from mnt namespace

[tip-bot for Jiri Olsa]

Commit-ID:  b01c1f69c8660eaeab7d365cd570103c5c073a02
Gitweb:     https://git.kernel.org/tip/b01c1f69c8660eaeab7d365cd570103c5c073a02
Author:     Jiri Olsa <jolsa@kernel.org>
AuthorDate: Thu, 1 Nov 2018 18:00:01 +0100
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 19 Nov 2018 12:12:26 -0800

perf tools: Restore proper cwd on return from mnt namespace

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.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Krister Johansen <kjlx@templeofstupid.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: 843ff37bb59e ("perf symbols: Find symbols in different mount namespace")
Link: http://lkml.kernel.org/r/20181101170001.30019-1-jolsa@kernel.org
[ No need to check for NULL args for free(), use zfree() for struct members ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/namespaces.c | 17 +++++++++++++++--
 tools/perf/util/namespaces.h |  1 +
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/namespaces.c b/tools/perf/util/namespaces.c
index cf8bd123cf73..aed170bd4384 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)
 {
@@ -186,6 +187,7 @@ void nsinfo__mountns_enter(struct nsinfo *nsi,
 	char curpath[PATH_MAX];
 	int oldns = -1;
 	int newns = -1;
+	char *oldcwd = NULL;
 
 	if (nc == NULL)
 		return;
@@ -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();
+	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 +216,13 @@ 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:
+	free(oldcwd);
 	if (oldns > -1)
 		close(oldns);
 	if (newns > -1)
@@ -223,11 +231,16 @@ errout:
 
 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));
+		zfree(&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);