[PATCH] perf: support running perf binaries with a dash in their name

[PATCH] perf: support running perf binaries with a dash in their name

[Milian Wolff]

Previously the part behind "perf-" was interpreted as an internal
perf command. If the suffix could not be handled, the execution
was stopped. This makes it impossible to launch perf binaries that
got renamed to have the `perf-` prefix. This is e.g. the case for
appimages (e.g. "perf-x86_64.AppImage"), but would also apply to
all other scenarios where users symlink or rename perf themselves:

Status quo with the broken behavior:
~~~~~
$ ln -s ./perf ./perf-custom-suffix
$ ./perf-custom-suffix list
cannot handle custom-suffix internally$
~~~~~

Also note the missing newline at the end of the error message.
With this patch applied, the above works properly:

~~~~~
$ ./perf-custom-suffix list

List of pre-defined events (to be used in -e):
...
~~~~~

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Yao Jin <yao.jin@linux.intel.com>
Signed-off-by: Milian Wolff <milian.wolff@kdab.com>
---
 tools/perf/perf.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index e0279babe0c0..7a3a39014446 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -467,15 +467,19 @@ int main(int argc, const char **argv)
 	 *  - cannot execute it externally (since it would just do
 	 *    the same thing over again)
 	 *
-	 * So we just directly call the internal command handler, and
-	 * die if that one cannot handle it.
+	 * So we just directly call the internal command handler. If that one
+	 * fails to handle this, then maybe we just run a renamed perf binary
+	 * that contains a dash in its name. To handle this scenario, we just
+	 * fall through and ignore the "xxxx" part of the command string.
 	 */
 	if (strstarts(cmd, "perf-")) {
 		cmd += 5;
 		argv[0] = cmd;
 		handle_internal_command(argc, argv);
-		fprintf(stderr, "cannot handle %s internally", cmd);
-		goto out;
+		// if the command is handled, the above function does not return
+		// undo changes and fall through in such a case
+		cmd -= 5;
+		argv[0] = cmd;
 	}
 	if (strstarts(cmd, "trace")) {
 #ifdef HAVE_LIBAUDIT_SUPPORT
-- 
2.14.1

Re: [PATCH] perf: support running perf binaries with a dash in their name

[David Ahern]

On 9/11/17 4:14 AM, Milian Wolff wrote:
> Previously the part behind "perf-" was interpreted as an internal
> perf command. If the suffix could not be handled, the execution
> was stopped. This makes it impossible to launch perf binaries that
> got renamed to have the `perf-` prefix. This is e.g. the case for
> appimages (e.g. "perf-x86_64.AppImage"), but would also apply to
> all other scenarios where users symlink or rename perf themselves:
> 
...
> ~~~~~
> $ ./perf-custom-suffix list
> 
> List of pre-defined events (to be used in -e):
> ...
> ~~~~~
> 
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: David Ahern <dsahern@gmail.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: Yao Jin <yao.jin@linux.intel.com>
> Signed-off-by: Milian Wolff <milian.wolff@kdab.com>
> ---
>  tools/perf/perf.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/perf/perf.c b/tools/perf/perf.c
> index e0279babe0c0..7a3a39014446 100644
> --- a/tools/perf/perf.c
> +++ b/tools/perf/perf.c
> @@ -467,15 +467,19 @@ int main(int argc, const char **argv)
>  	 *  - cannot execute it externally (since it would just do
>  	 *    the same thing over again)
>  	 *
> -	 * So we just directly call the internal command handler, and
> -	 * die if that one cannot handle it.
> +	 * So we just directly call the internal command handler. If that one
> +	 * fails to handle this, then maybe we just run a renamed perf binary
> +	 * that contains a dash in its name. To handle this scenario, we just
> +	 * fall through and ignore the "xxxx" part of the command string.
>  	 */
>  	if (strstarts(cmd, "perf-")) {
>  		cmd += 5;
>  		argv[0] = cmd;
>  		handle_internal_command(argc, argv);
> -		fprintf(stderr, "cannot handle %s internally", cmd);
> -		goto out;
> +		// if the command is handled, the above function does not return
> +		// undo changes and fall through in such a case

Those should be /* */ not //

> +		cmd -= 5;
> +		argv[0] = cmd;
>  	}
>  	if (strstarts(cmd, "trace")) {
>  #ifdef HAVE_LIBAUDIT_SUPPORT
> 

other than that LGTM and long over due.

Acked-by: David Ahern <dsahern@gmail.com>

Re: [PATCH] perf: support running perf binaries with a dash in their name

[Arnaldo Carvalho de Melo]

Em Mon, Sep 11, 2017 at 07:08:18AM -0700, David Ahern escreveu:
> On 9/11/17 4:14 AM, Milian Wolff wrote:
> > Previously the part behind "perf-" was interpreted as an internal
> > perf command. If the suffix could not be handled, the execution
<SNIP>
> > --- a/tools/perf/perf.c
> > -		fprintf(stderr, "cannot handle %s internally", cmd);
> > -		goto out;
> > +		// if the command is handled, the above function does not return
> > +		// undo changes and fall through in such a case
 
> Those should be /* */ not //
> 
> > +		cmd -= 5;
> > +		argv[0] = cmd;
> >  	}
> >  	if (strstarts(cmd, "trace")) {
> >  #ifdef HAVE_LIBAUDIT_SUPPORT
 
> other than that LGTM and long over due.
 
> Acked-by: David Ahern <dsahern@gmail.com>

We got those from git, agreed it should go, thanks for the Acked-by,
always welcome!

- Arnaldo

Re: [PATCH] perf: support running perf binaries with a dash in their name

[Milian Wolff]

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On Monday, September 11, 2017 4:33:12 PM CEST Arnaldo Carvalho de Melo wrote:
> Em Mon, Sep 11, 2017 at 07:08:18AM -0700, David Ahern escreveu:
> > On 9/11/17 4:14 AM, Milian Wolff wrote:
> > > Previously the part behind "perf-" was interpreted as an internal
> > > perf command. If the suffix could not be handled, the execution
> 
> <SNIP>
> 
> > > --- a/tools/perf/perf.c
> > > -		fprintf(stderr, "cannot handle %s internally", cmd);
> > > -		goto out;
> > > +		// if the command is handled, the above function does not return
> > > +		// undo changes and fall through in such a case
> > 
> > Those should be /* */ not //
> > 
> > > +		cmd -= 5;
> > > +		argv[0] = cmd;
> > > 
> > >  	}
> > >  	if (strstarts(cmd, "trace")) {
> > >  
> > >  #ifdef HAVE_LIBAUDIT_SUPPORT
> > 
> > other than that LGTM and long over due.
> > 
> > Acked-by: David Ahern <dsahern@gmail.com>
> 
> We got those from git, agreed it should go, thanks for the Acked-by,
> always welcome!

Arnaldo, do you want me to fixup the commit, or can you handle it?

Thanks for the review guys

-- 
Milian Wolff | milian.wolff@kdab.com | Senior Software Engineer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt Experts

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Re: [PATCH] perf: support running perf binaries with a dash in their name

[Arnaldo Carvalho de Melo]

Em Mon, Sep 11, 2017 at 05:16:11PM +0200, Milian Wolff escreveu:
> On Monday, September 11, 2017 4:33:12 PM CEST Arnaldo Carvalho de Melo wrote:
> > Em Mon, Sep 11, 2017 at 07:08:18AM -0700, David Ahern escreveu:
> > > other than that LGTM and long over due.

> > > Acked-by: David Ahern <dsahern@gmail.com>

> > We got those from git, agreed it should go, thanks for the Acked-by,
> > always welcome!
 
> Arnaldo, do you want me to fixup the commit, or can you handle it?
 
> Thanks for the review guys

I did it already, thanks.

- Arnaldo