[llvm] r309611 - [sanitizer-coverage] don't instrument available_externally functions

[David Blaikie via llvm-commits]

On Mon, Jul 31, 2017 at 1:50 PM Kostya Serebryany <kcc at google.com> wrote:

> On Mon, Jul 31, 2017 at 1:46 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
>>
>>
>> On Mon, Jul 31, 2017 at 1:01 PM Kostya Serebryany via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>>
>>> Author: kcc
>>> Date: Mon Jul 31 13:00:22 2017
>>> New Revision: 309611
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=309611&view=rev
>>> Log:
>>> [sanitizer-coverage] don't instrument available_externally functions
>>>
>>
>> I take it this happens long after inlining, etc?
>>
>
> Correct. this happens at the later stages of LLVM transformations.
>
>
>> (usually I'd expect various sanitizer instrumentation to happen early
>>
>
> It depends.
> ubsan happens in frontend, because there is where we have all the
> C++-cpecific data.
> asan/msan/tsan happen late in LLVM pipeline, because by that time all
> loads/stores that could have been optimized -- are.
> sanitizer coverage happens right before asan/msan/tsan
>
>
>> - so it could be inlined & still tracked, etc (eg: you'd want to know you
>> had function coverage at one inlined site rather than believing there was
>> no coverage at all)
>>
>
> Sanitizer coverage is *mostly* used for automated tools like fuzzers, and
> so visualization of coverage is of a less concern (still is, but that's a
> trade-off)
>

Ah, makes sense - thanks for the context!


>
>
>> - so it surprises me that you wouldn't want to instrument
>> available_externally functions so that when they were inlined the inlined
>> version would be appropriately instrumented too)
>>
>>
>>>
>>> Modified:
>>>     llvm/trunk/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
>>>     llvm/trunk/test/Instrumentation/SanitizerCoverage/tracing.ll
>>>
>>> Modified: llvm/trunk/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/SanitizerCoverage.cpp?rev=309611&r1=309610&r2=309611&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
>>> (original)
>>> +++ llvm/trunk/lib/Transforms/Instrumentation/SanitizerCoverage.cpp Mon
>>> Jul 31 13:00:22 2017
>>> @@ -418,6 +418,9 @@ bool SanitizerCoverageModule::runOnFunct
>>>      return false; // Should not instrument sanitizer init functions.
>>>    if (F.getName().startswith("__sanitizer_"))
>>>      return false;  // Don't instrument __sanitizer_* callbacks.
>>> +  // Don't touch available_externally functions, their actual body is
>>> elewhere.
>>> +  if (F.getLinkage() == GlobalValue::AvailableExternallyLinkage)
>>> +    return false;
>>>    // Don't instrument MSVC CRT configuration helpers. They may run
>>> before normal
>>>    // initialization.
>>>    if (F.getName() == "__local_stdio_printf_options" ||
>>>
>>> Modified: llvm/trunk/test/Instrumentation/SanitizerCoverage/tracing.ll
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Instrumentation/SanitizerCoverage/tracing.ll?rev=309611&r1=309610&r2=309611&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/test/Instrumentation/SanitizerCoverage/tracing.ll
>>> (original)
>>> +++ llvm/trunk/test/Instrumentation/SanitizerCoverage/tracing.ll Mon Jul
>>> 31 13:00:22 2017
>>> @@ -18,6 +18,12 @@ entry:
>>>    ret void
>>>  }
>>>
>>> +define available_externally void @external_bar(i32* %a)
>>> sanitize_address {
>>> +entry:
>>> +  ret void
>>> +}
>>> +
>>> +
>>>  ; CHECK_PC-LABEL: define void @foo
>>>  ; CHECK_PC: call void @__sanitizer_cov_trace_pc
>>>  ; CHECK_PC: call void @__sanitizer_cov_trace_pc
>>> @@ -33,6 +39,10 @@ entry:
>>>  ; CHECK_PC_GUARD: call void @__sanitizer_cov_trace_pc_guard
>>>  ; CHECK_PC_GUARD-NOT: call void @__sanitizer_cov_trace_pc
>>>  ; CHECK_PC_GUARD: ret void
>>> +; CHECK_PC_GUARD-LABEL: @external_bar
>>> +; CHECK_PC_GUARD-NOT: call void @__sanitizer_cov_trace_pc
>>> +; CHECK_PC_GUARD: ret void
>>> +
>>>  ; CHECK_PC_GUARD: call void @__sanitizer_cov_trace_pc_guard_init(i32*
>>> bitcast (i32** @__start___sancov_guards to i32*), i32* bitcast (i32**
>>> @__stop___sancov_guards to i32*))
>>>
>>>  ; CHECK_PC_GUARD_DARWIN-LABEL: define void @foo
>>>
>>>
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>>>
>>
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