linux-kernel - Re: [PATCH v5 2/7] perf annotate: Add cross arch annotate support

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Message-Id: <57B6EE92.6050200@linux.vnet.ibm.com>
Date:   Fri, 19 Aug 2016 17:03:38 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        acme@...nel.org, peterz@...radead.org, mingo@...hat.com,
        alexander.shishkin@...ux.intel.com, treeze.taeung@...il.com,
        naveen.n.rao@...ux.vnet.ibm.com, markus@...ppelsdorf.de,
        chris.ryder@....com, pawel.moll@....com, mhiramat@...nel.org,
        jolsa@...nel.org, mpe@...erman.id.au, hemant@...ux.vnet.ibm.com,
        namhyung@...nel.org,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Subject: Re: [PATCH v5 2/7] perf annotate: Add cross arch annotate support



On Friday 19 August 2016 04:18 PM, Russell King - ARM Linux wrote:
> On Fri, Aug 19, 2016 at 04:09:51PM +0530, Ravi Bangoria wrote:
>> Thanks Russell for reviewing.
>>
>> On Friday 19 August 2016 01:20 PM, Russell King - ARM Linux wrote:
>>> On Fri, Aug 19, 2016 at 10:59:01AM +0530, Ravi Bangoria wrote:
>>>> -static struct ins instructions[] = {
>>>> +static struct ins instructions_x86[] = {
>>>>  	{ .name = "add",   .ops  = &mov_ops, },
>>>>  	{ .name = "addl",  .ops  = &mov_ops, },
>>>>  	{ .name = "addq",  .ops  = &mov_ops, },
>>>>  	{ .name = "addw",  .ops  = &mov_ops, },
>>>>  	{ .name = "and",   .ops  = &mov_ops, },
>>>> -#ifdef __arm__
>>>> -	{ .name = "b",     .ops  = &jump_ops, }, // might also be a call
>>>> -	{ .name = "bcc",   .ops  = &jump_ops, },
>>>> -	{ .name = "bcs",   .ops  = &jump_ops, },
>>>> -	{ .name = "beq",   .ops  = &jump_ops, },
>>>> -	{ .name = "bge",   .ops  = &jump_ops, },
>>>> -	{ .name = "bgt",   .ops  = &jump_ops, },
>>>> -	{ .name = "bhi",   .ops  = &jump_ops, },
>>>> -	{ .name = "bl",    .ops  = &call_ops, },
>>>> -	{ .name = "bls",   .ops  = &jump_ops, },
>>>> -	{ .name = "blt",   .ops  = &jump_ops, },
>>>> -	{ .name = "blx",   .ops  = &call_ops, },
>>>> -	{ .name = "bne",   .ops  = &jump_ops, },
>>>> -#endif
>>> Notice that ARM includes a lot of other instructions from this table,
>>> not just those above.
>>>
>>>>  	{ .name = "bts",   .ops  = &mov_ops, },
>>>>  	{ .name = "call",  .ops  = &call_ops, },
>>>>  	{ .name = "callq", .ops  = &call_ops, },
>>>> @@ -456,6 +444,21 @@ static struct ins instructions[] = {
>>>>  	{ .name = "retq",  .ops  = &ret_ops, },
>>>>  };
>>>>  
>>>> +static struct ins instructions_arm[] = {
>>>> +	{ .name = "b",     .ops  = &jump_ops, }, /* might also be a call */
>>>> +	{ .name = "bcc",   .ops  = &jump_ops, },
>>>> +	{ .name = "bcs",   .ops  = &jump_ops, },
>>>> +	{ .name = "beq",   .ops  = &jump_ops, },
>>>> +	{ .name = "bge",   .ops  = &jump_ops, },
>>>> +	{ .name = "bgt",   .ops  = &jump_ops, },
>>>> +	{ .name = "bhi",   .ops  = &jump_ops, },
>>>> +	{ .name = "bl",    .ops  = &call_ops, },
>>>> +	{ .name = "bls",   .ops  = &jump_ops, },
>>>> +	{ .name = "blt",   .ops  = &jump_ops, },
>>>> +	{ .name = "blx",   .ops  = &call_ops, },
>>>> +	{ .name = "bne",   .ops  = &jump_ops, },
>>>> +};
>>>> +
>>> ...
>>>> +	if (!strcmp(norm_arch, NORM_X86)) {
>>>> +		instructions = instructions_x86;
>>>> +		nmemb = ARRAY_SIZE(instructions_x86);
>>>> +	} else if (!strcmp(norm_arch, NORM_ARM)) {
>>>> +		instructions = instructions_arm;
>>>> +		nmemb = ARRAY_SIZE(instructions_arm);
>>> But these changes result in _only_ the ones that were in the #if __arm__
>>> being matched.  This is wrong.
>>>
>>> If we want to go that way, we need to add _all_ arm instructions to
>>> instructions_arm, not just those within the #if.
>> Yes, I've mentioned same in cover letter as well.
>>
>> Can I add all x86 instructions for arm as well? If not, can you please
>> provide a list of arm instructions that needs to be added here.
> If it were me doing a change like this, I'd be trying to preserve the
> current behaviour to avoid causing regressions, which would mean
> ensuring that all the instructions that were visible before the change
> remain visible after the change, even those which are obviously x86
> specific but were still in the table anyway.  It then becomes a cleanup
> matter later to remove those which aren't relevent, rather than having
> to chase around wondering why the tool broke.
>
> I'm afraid I don't have time to look at this (I'm chasing regressions
> and bugs in the kernel) so I'd suggest you try to avoid causing
> regressions in this tool...
>

Yes Russell, Fair point. Will send a next series.

-Ravi