linux-kernel - Re: [PATCH v2] perf: report/annotate: fix segfault problem.

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Date:	Fri, 3 Apr 2015 12:57:21 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	namhyung@...nel.org, jolsa@...nel.org, acme@...hat.com,
	mingo@...nel.org, linux-kernel@...r.kernel.org, pi3orama@....com
Subject: Re: [PATCH v2] perf: report/annotate: fix segfault problem.

On Fri, Apr 03, 2015 at 05:56:25AM +0000, Wang Nan wrote:
> perf report and perf annotate are easy to trigger segfault if trace data
> contain kernel module information like this:
> 
>  # perf report -D -i ./perf.data
>  ...
>  0 0 0x188 [0x50]: PERF_RECORD_MMAP -1/0: [0xffffffbff1018000(0xf068000) @ 0]: x [test_module]

oops, I was wondering how you'd get such a MMAP record, because we lookup
modules real paths and store it.. I haven't realized that if we dont find
it we keep the '[mod]' name :-\

SNIP

> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> ---
> 
> Patch v1 doesn't consider module named as [aaa.bbb].
> 
> ---
>  tools/perf/util/dso.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
> index fc0ddd5..08d7aaf 100644
> --- a/tools/perf/util/dso.c
> +++ b/tools/perf/util/dso.c
> @@ -214,12 +214,23 @@ int __kmod_path__parse(struct kmod_path *m, const char *path,
>  {
>  	const char *name = strrchr(path, '/');
>  	const char *ext  = strrchr(path, '.');
> +	bool is_simple_name = false;
>  
>  	memset(m, 0x0, sizeof(*m));
>  	name = name ? name + 1 : path;
>  
> +	/*
> +	 * '.' is also a valid character. For example: [aaa.bbb] is a
> +	 * valid module name. '[' should have higher priority than
> +	 * '.ko' suffix.
> +	 */


> +	if ((name[0] == '[') &&	(strncmp(name, "[vdso]", 6) != 0)) {

maybe also check for '[vsyscall]' ?

> +		m->kmod = true;
> +		is_simple_name = true;
> +	}
> +
>  	/* No extension, just return name. */
> -	if (ext == NULL) {
> +	if ((ext == NULL) || is_simple_name) {
>  		if (alloc_name) {
>  			m->name = strdup(name);
>  			return m->name ? 0 : -ENOMEM;

otherwise it looks ok to me.. please update also the tests/kmod-path.c ;-)

thanks,
jirka
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