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Re: [PATCH, RFC] Enable libsanitizer on powerpc{,64}


On Tue, Nov 20, 2012 at 6:21 PM, Konstantin Serebryany
<konstantin.s.serebryany@gmail.com> wrote:
> On Tue, Nov 20, 2012 at 6:18 PM, Evgeniy Stepanov
> <eugeni.stepanov@gmail.com> wrote:
>> On Tue, Nov 20, 2012 at 5:52 PM, Konstantin Serebryany
>> <konstantin.s.serebryany@gmail.com> wrote:
>>>
>>> On Tue, Nov 20, 2012 at 5:41 PM, Peter Bergner <bergner@vnet.ibm.com>
>>> wrote:
>>> > On Tue, 2012-11-20 at 11:07 +0400, Konstantin Serebryany wrote:
>>> >> I've applied your patch (with minor style and comment changes)
>>> >> upstream:
>>> >> http://llvm.org/viewvc/llvm-project?view=rev&revision=168356
>>> >> I did not have any way to test it though. Also, gmail does something
>>> >> horrible with patches inlined in a message, so I might have missed
>>> >> something.
>>> >
>>> > Doing a quick peruse through your LLVM commit, I see you grabbed the
>>> > PopStackFrames() addition, but the asan_linux.cc changes do not include
>>> > the call to PopStackFrames() after the _Unwind_Backtrace() call.
>>> > Specifically, the following patch hunk:
>>> >
>>> >>      _Unwind_Backtrace(Unwind_Trace, stack);
>>> >> > +    // Pop off the two ASAN functions from the backtrace.
>>> >> > +    stack->PopStackFrames(2);
>>
>>
>> I wonder if under some conditions we may get a different number of extra
>> frames (inlining comes to mind). What do you think of removing any number of
>> frames that belong to the runtime library - we have memory layout info for
>> that?
>
> Bad idea, imho.
> Hard to implement, slower to run (remember, this *is* a hotspot).
> The frames in question are in our run-time and we can fully control inlining.
> What is the current number of redundant frames on ARM?


And we can have output tests that verify that we remove the right
number of frames.


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