linux-kernel - Re: [PATCH 3/4] perf annotate: add powerpc support

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Message-Id: <57736F01.1010308@linux.vnet.ibm.com>
Date:	Wed, 29 Jun 2016 12:17:29 +0530
From:	Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
To:	David Laight <David.Laight@...LAB.COM>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"acme@...nel.org" <acme@...nel.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Cc:	"ananth@...ibm.com" <ananth@...ibm.com>,
	"naveen.n.rao@...ux.vnet.ibm.com" <naveen.n.rao@...ux.vnet.ibm.com>,
	"dja@...ens.net" <dja@...ens.net>
Subject: Re: [PATCH 3/4] perf annotate: add powerpc support

Thanks David.

On Tuesday 28 June 2016 09:37 PM, David Laight wrote:
> From: Ravi Bangoria
>> Sent: 28 June 2016 12:37
>>
>> Powerpc has long list of branch instructions and hardcoding them in table
>> appears to be error-prone. So, add new function to find instruction
>> instead of creating table.
>>
>> Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
>> Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
>> ---
>>   tools/perf/util/annotate.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 64 insertions(+)
>>
>> diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
>> index 36a5825..96c6610 100644
>> --- a/tools/perf/util/annotate.c
>> +++ b/tools/perf/util/annotate.c
>> @@ -476,6 +476,68 @@ static int ins__cmp(const void *a, const void *b)
>>   	return strcmp(ia->name, ib->name);
>>   }
>>
>> +static struct ins *ins__find_powerpc(const char *name)
> It would be better if the function name include 'branch'.
>
>> +{
>> +	int i;
>> +	struct ins *ins;
>> +
>> +	ins = zalloc(sizeof(struct ins));
>> +	if (!ins)
>> +		return NULL;
>> +
>> +	ins->name = strdup(name);
>> +	if (!ins->name)
>> +		return NULL;
> 	You leak 'ins' here.
>
>> +
>> +	if (name[0] == 'b') {
>> +		/* branch instructions */
>> +		ins->ops = &jump_ops;
>> +
>> +		/*
>> +		 * - Few start with 'b', but aren't branch instructions.
>> +		 * - Let's also ignore instructions involving 'ctr' and
>> +		 *   'tar' since target branch addresses for those can't
>> +		 *   be determined statically.
>> +		 */
>> +		if (!strncmp(name, "bcd", 3)   ||
>> +		    !strncmp(name, "brinc", 5) ||
>> +		    !strncmp(name, "bper", 4)  ||
>> +		    strstr(name, "ctr")        ||
>> +		    strstr(name, "tar"))
>> +			return NULL;
> 	More importantly you leak 'ins' and 'ins->name' here.
> 	And on other paths below.

Yes. Fair points.

I can create linked list that maintain allocated instructions and
lookup it every time before allocating memory. But for this,
I need to free memory at the end and it's becoming complicated.

I can go back to normal approach of creating table for powerpc.
This is simplest. But only problem is powerpc has around 400 branch
instructions(which includes call and ret as well). And list them all is
bit error-prone.

Suggestions?

- Ravi

> ...
>
> 	David
>