linux-kernel - Re: [PATCH v2 1/2] perf tools: Make find_vdso

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Date:   Mon, 10 Dec 2018 12:16:39 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Kim Phillips <kim.phillips@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        rmk+kernel@...linux.org.uk, l.stach@...gutronix.de
Subject: Re: [PATCH v2 1/2] perf tools: Make find_vdso_map() more modular

On 11/27/18 1:31 AM, Jiri Olsa wrote:
> On Thu, Oct 25, 2018 at 10:55:07AM -0700, Florian Fainelli wrote:
>> In preparation for checking that the vectors page on the ARM
>> architecture, refactor the find_vdso_map() function to accept finding an
>> arbitrary string and create a dedicated helper function for that under
>> util/find-map.c and update find_vdso_map() to use it.
>>
>> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
>> ---
>>  tools/perf/util/find-map.c      | 31 +++++++++++++++++++++++++++++++
>>  tools/perf/util/find-vdso-map.c | 30 +++---------------------------
>>  2 files changed, 34 insertions(+), 27 deletions(-)
>>  create mode 100644 tools/perf/util/find-map.c
>>
>> diff --git a/tools/perf/util/find-map.c b/tools/perf/util/find-map.c
>> new file mode 100644
>> index 000000000000..19a3431a7b2a
>> --- /dev/null
>> +++ b/tools/perf/util/find-map.c
>> @@ -0,0 +1,31 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +static int find_map(void **start, void **end, const char *name)
>> +{
>> +	FILE *maps;
>> +	char line[128];
>> +	int found = 0;
>> +
>> +	maps = fopen("/proc/self/maps", "r");
>> +	if (!maps) {
>> +		fprintf(stderr, "vdso: cannot open maps\n");
>> +		return -1;
>> +	}
>> +
>> +	while (!found && fgets(line, sizeof(line), maps)) {
>> +		int m = -1;
>> +
>> +		/* We care only about private r-x mappings. */
>> +		if (2 != sscanf(line, "%p-%p r-xp %*x %*x:%*x %*u %n",
>> +				start, end, &m))
>> +			continue;
>> +		if (m < 0)
>> +			continue;
>> +
>> +		if (!strncmp(&line[m], name, strlen(name)))
>> +			found = 1;
>> +	}
>> +
>> +	fclose(maps);
>> +	return !found;
>> +}
> 
> please keep just one object for both.. looks to me like
> it coud go to util.c.. or just find-map.c if there's
> a reason to have this separated

The reason for keeping both implementations separate is because
VDSO__MAP_NAME may not be defined/applicable for all architectures, so
instead of having them have to define VDSO__MAP_NAME just to get that
file to build, they would only include find-map.c to get access to
find_map() and then search for specific tokens.

Would you prefer if find_map() was moved to tools/perf/util/util.c?
-- 
Florian