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

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Date:   Wed, 29 Nov 2017 20:52:13 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
To:     Thomas-Mich Richter <tmricht@...ux.vnet.ibm.com>, acme@...nel.org
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        brueckner@...ux.vnet.ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Subject: Re: [PATCH] perf annotate: Fix objdump comment parsing for Intel mov
 dissassembly



On 11/29/2017 08:33 PM, Thomas-Mich Richter wrote:
> 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);
> }

Looks good.  Ack-by: Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>

Thanks,
Ravi