linux-kernel - Re: [PATCH] perf: Correctly identify anon

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Message-ID: <20151126171230.GF28162@kernel.org>
Date:	Thu, 26 Nov 2015 14:12:30 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Yannick Brosseau <scientist@...com>
Cc:	linux-kernel@...r.kernel.org, kernel-team@...com,
	zhu.wen-jie@...com, ak@...ux.intel.com
Subject: Re: [PATCH] perf: Correctly identify anon_hugepage when generating
 map (v2)

Em Thu, Nov 26, 2015 at 03:42:32AM -0800, Yannick Brosseau escreveu:
> When parsing /proc/xxx/maps, the sscanf in perf_event__synthesize_mmap_events
> truncate the map name at the space in "/anon_hugepage (deleted)".
> is_anon_memory then only receive the string "/anon_hugepage" and do not detect it.
> We change is_anon_memory to only compare the first part of the string
> effectively ignoring if the (deleted) part is there or not.

Thanks, applied, tested with:

[acme@zoo c]$ cat scanf_proc_smaps.c 
#include <inttypes.h>
#include <limits.h>
#include <stdio.h>

typedef unsigned int u32;
typedef unsigned long long u64;

struct mmap2_event {
	u32 pid, tid;
	u64 start;
	u64 len;
	u64 pgoff;
	u32 maj;
	u32 min;
	u64 ino;
	u64 ino_generation;
	u32 prot;
	u32 flags;
	char filename[PATH_MAX];
};

union perf_event {
	struct mmap2_event mmap2;
};

static inline int is_anon_memory(const char *filename)
{
	return !strcmp(filename, "//anon") ||
	       !strncmp(filename, "/dev/zero", sizeof("/dev/zero") - 1) ||
	       !strncmp(filename, "/anon_hugepage", sizeof("/anon_hugepage") - 1);
}

int main(void)
{
	union perf_event event;
	unsigned int ino;
	char prot[5];
	char bf[] = "7f939395e000-7f939395f000 rw-s 00000000 00:05 98715                      /dev/zero (deleted)";
	int n = sscanf(bf, "%"PRIx64"-%"PRIx64" %s %"PRIx64" %x:%x %u %s\n",
                       &event.mmap2.start, &event.mmap2.len, prot,
                       &event.mmap2.pgoff, &event.mmap2.maj,
                       &event.mmap2.min,
                       &ino, event.mmap2.filename);

	printf("event.filename=\"%s\"\n", event.mmap2.filename);
	if (is_anon_memory(event.mmap2.filename))
		printf("This is anonymous memory\n");
	return 0;
}
[acme@zoo c]$ ./scanf_proc_smaps 
event.filename="/dev/zero"
This is anonymous memory
[acme@zoo c]$
 
> Signed-off-by: Yannick Brosseau <scientist@...com>
> ---
>  tools/perf/util/map.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
> index afc6b56..97e11a7 100644
> --- a/tools/perf/util/map.c
> +++ b/tools/perf/util/map.c
> @@ -26,8 +26,8 @@ const char *map_type__name[MAP__NR_TYPES] = {
>  static inline int is_anon_memory(const char *filename)
>  {
>  	return !strcmp(filename, "//anon") ||
> -	       !strcmp(filename, "/dev/zero (deleted)") ||
> -	       !strcmp(filename, "/anon_hugepage (deleted)");
> +	       !strncmp(filename, "/dev/zero", sizeof("/dev/zero")-1) ||
> +	       !strncmp(filename, "/anon_hugepage", sizeof("/anon_hugepage")-1);
>  }
>  
>  static inline int is_no_dso_memory(const char *filename)
> -- 
> 2.6.2
--
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