Re: [PATCH] perf tool: Round mmap pages to power 2

[David Ahern]

On 11/8/13, 2:11 AM, Adrian Hunter wrote:
> This prevents:
>
>      --out-pages=0
>
> from working e.g.
>
>      tools/perf/perf record -vv --out-pages=0 uname
>      rounding mmap pages size to 4096 (1 pages)
>
> Although without this patch:
>
>      tools/perf/perf record -vv --out-pages=0 uname
>      --mmap_pages/-m value must be a power of two.
>       usage: perf record [<options>] [<command>]
>          or: perf record [<options>] -- <command> [<options>]
>
>              --out-pages <pages>
>                            Number of pages or size with units to use for
> output (default 64M)
>
> Also there is:
>
>      tools/perf/perf record -vv --no-out-pages uname
>      Segmentation fault (core dumped)

This is problem with perf_evlist__parse_mmap_pages(); same thing happens 
with --no-map-pages.

With the attached both round a 0 up to 1 page:

[daahern@nxos-vdc-dev3 perf]$ perf record --out-pages 0 uname
rounding mmap pages size to 4096 (1 pages)
Linux
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.008 MB perf.data (~339 samples) ]

[daahern@nxos-vdc-dev3 perf]$ perf record --mmap-pages 0 uname
rounding mmap pages size to 4096 (1 pages)
Linux
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.008 MB perf.data (~339 samples) ]

[daahern@nxos-vdc-dev3 perf]$ perf record --no-mmap-pages uname

 usage: perf record [<options>] [<command>]
    or: perf record [<options>] -- <command> [<options>]

    -m, --mmap-pages <pages>
                          number of mmap data pages
David

>From fc7c5a6b2b47a2e7a04613b4e82e478a0dcabf42 Mon Sep 17 00:00:00 2001
From: David Ahern <dsahern@xxxxxxxxx>
Date: Fri, 8 Nov 2013 07:37:43 -0700
Subject: [PATCH] perf record: Fix segfault with --no-mmap-pages

Adrian reported a segfault when using --no-out-pages
$ tools/perf/perf record -vv --no-out-pages uname
Segmentation fault (core dumped)

The same occurs with --no-mmap-pages. Fix by checking that str is non-NULL
before parsing it.

Reported-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Signed-off-by: David Ahern <dsahern@xxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
---
 tools/perf/util/evlist.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 9ec3a5a45f22..1f103616d906 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -718,6 +718,9 @@ int perf_evlist__parse_mmap_pages(const struct option *opt, const char *str,
 		{ .tag  = 0 },
 	};
 
+	if (str == NULL)
+		return -1;
+
 	val = parse_tag_value(str, tags);
 	if (val != (unsigned long) -1) {
 		/* we got file size value */
-- 
1.8.3.4 (Apple Git-47)