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Re: RFC: enhanced memory protection support

From: Vladimir 'φ-coder/phcoder' Serbinenko
Subject: Re: RFC: enhanced memory protection support
Date: Tue, 01 May 2012 12:29:00 +0200
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On 30.04.2012 19:24, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> On 30.04.2012 17:26, Bean wrote:
>> Hi,
>> While testing network function in efi mode, I've found several memory
>> leak related to fragmentation, but there is still some memory problem
>> that's very tricky to locate. For example, you can run testspeed on a
>> large file several times in a row and it could show the memory error.
>> Since network condition are very difficult to reproduce, I have to
>> look at the source of this issue, memory allocation. Currently it has
>> mm_debug option that could print out file and line number of each
>> memory call, but it's quite useless since we can't find the relevant
>> informaton with full screen of prints.
>> Here are some of my ideas for enhanced memory protection support:
>> 1, when we allocate memory, we append some information at the end of
>> the buffer, which include filename, lineno of caller, and tag to
>> indicate what is used for and some padding to detect memory overwrite
>> problem.
>> 2. add a command to print the current memory list with extended
>> information, this can be used to find memory leaks.
>> 3. it's also a good idea to run the memory check in automated test to
>> locate potential issue.
> This is pretty easy to do leveraging some of the code I did for POSIX
> support. But:
> - Due to additional time and space required it should be done only when
> mm-debug is enabled.
> - The additional data has to be stored before rather than after the
> range since we store all the info before.
> - Integrating with automated tests isn't that easy since some memory is
> intentionally never freed i.a. disk cache or otherwise in use (i.a.
> terminal). We need exceptions for those.
> I have half-working patch, just needs few fixes.
Patch attached. It still has a bug since printing the report to terminal
may change allocations and so iterator may become invalid. That's
another reason why terminal should be excluded altogether from memory

Vladimir 'φ-coder/phcoder' Serbinenko

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