linux-kernel - Re: [PATCH] perf annotate: Fix objdump comment parsing for Intel mov dissassembly

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Date:   Wed, 29 Nov 2017 16:03:07 +0100
From:   Thomas-Mich Richter <tmricht@...ux.vnet.ibm.com>
To:     Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        acme@...nel.org, brueckner@...ux.vnet.ibm.com,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com
Subject: Re: [PATCH] perf annotate: Fix objdump comment parsing for Intel mov
 dissassembly

On 11/29/2017 02:24 PM, Ravi Bangoria wrote:
> 
> 
> On 11/28/2017 01:26 PM, Thomas Richter wrote:
>> The command 'perf annotate' parses the output of objdump and also
>> investigates the comments produced by objdump. For example the
>> output of objdump produces (on x86):
>>
>> 23eee:  4c 8b 3d 13 01 21 00 mov 0x210113(%rip),%r15
>>                                 # 234008 <stderr@@GLIBC_2.2.5+0x9a8>
>>
>> and the function mov__parse() is called to investigate the complete
>> line. Mov__parse() breaks this line into several parts and finally
>> calls function comment__symbol() to parse the data after the comment
>> character '#'. Comment__symbol() expects a hexadecimal address followed
>> by a symbol in '<' and '>' brackets.
>>
>> However the 2nd parameter given to function comment__symbol()
>> always points to the comment character '#'. The address parsing
>> always returns 0 because the character '#' is not a digit and
>> strtoull() fails without being noticed.
>>
>> Fix this by advancing the second parameter to function comment__symbol()
>> by one byte before invocation and add an error check after strtoull()
>> has been called.
> 
> Yeah, looks like it fails to get correct value in 'addrp'.
> 
> Can you please show the difference in perf annotate output before
> and after patch.
> 
> Thanks,
> Ravi
> 


There is no difference in output of --stdio. The adress value is not
read and remains 0x0 in ops->source.addr or ops->target.addr.
That is not visible because in function mov__scnprintf() that wrong
address is not printed:

static int mov__scnprintf(struct ins *ins, char *bf, size_t size,
                           struct ins_operands *ops)
{
        return scnprintf(bf, size, "%-6.6s %s,%s", ins->name,
                         ops->source.name ?: ops->source.raw,
                         ops->target.name ?: ops->target.raw);
}


-- 
Thomas Richter, Dept 3303, IBM LTC Boeblingen Germany
--
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