[PATCH] makedumpfile: change the wrong code to calculate bufsize_cyclic for elf dump

Atsushi Kumagai kumagai-atsushi at mxc.nes.nec.co.jp
Fri May 23 00:18:01 PDT 2014

Hello Bao,

>Hi Astushi,
>> No, 16MB was used for bitmaps also in my case.
>> --cyclic-buffer option means specifying each bitmap size, so allocated bitmap
>> size is the double of --cyclic-buffer.
>> (But now, this behavior is only for ELF case, just the specified size is allocated
>> in kdump case. Yes, it's confusing...)
>>        --cyclic-buffer buffer_size
>>               Specify the buffer size in kilo bytes for analysis in the cyclic
>>               mode.  Actually, the double of buffer_size kilo  bytes  will  be
>>               allocated  in  memory.  In the cyclic mode, the number of cycles
>>               is represented as:
>Yeah, I was wrong about this. If specified --cyclic-buffer doesn't
>exceed the memory limit, it is equal to info->bufsize_cyclic. But for
>elf dump, it need be double. E.g if free memory is 30M, --cyclic-buffer
>is 16M, it will absolutely fail. But the code check here should be done
>separately. Since it's meaningless for elf dump if 2 x --cyclic-buffer
>exceeds the free memory.
>	if (info->bufsize_cyclic > free_memory) {
>	.......
>	{
>I think code here need be changed.

Exactly, this is a bug.
I can fix it simply by modification to the check above, but I think it's
better to change the ELF path to get rid of the 1st bitmap buffer since it's
unused. Then the required buffer size will be just <--cyclic-buffer> in both
cases, so I'll post the patch to do it later.

Atsushi Kumagai

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