[compiler-rt] r231413 - [sanitizer] Reconstruct the function that dumps block/edge coverage, hopefully making it more robust. Also increase the allowed coverage size on 32-bit.

[Kostya Serebryany]

Interesting. in r225281 added XFAIL: darwin
Do you actually mean that the test now started passing?
>From your link: "Exit Code: 0"


On Mon, Mar 9, 2015 at 2:25 PM, Kuba Brecka <kuba.brecka at gmail.com> wrote:

> Hi Kostya,
>
> I believe this recent change (r231413) caused a subtle change in behavior
> that is causing a test failure on the Darwin buildbot at
> http://lab.llvm.org:8080/green/job/clang-stage1-cmake-RA_check/2083/console.
> The test is failing for a few days already, but it’s hard to tell which
> exact patch caused the regression, because the bot was offline for a day
> and a half when it occurred.
>
> I think the cause is this:  The old code in CovDump() iterates over the
> process map, but it intentionally skips over segments that are not
> executable.  The new code in DumpOffsets() asks GetModuleNameAndOffsetForPC
> instead, which contains a bug/feature that is triggered for in a 64-bit
> binary when a 4GB __PAGEZERO (with protection=0) segment is present.  In
> that case GetModuleNameAndOffsetForPC will say that the resulting offset is
> larger than 4GB, and the subsequent check in DumpOffsets that asserts
> `offset > 0xffffffffU` will ignore that item and not print it into the
> coverage file.
>
> I also realized that simply ignoring __PAGEZERO in the Darwin
> implementation of process maps is not going to work easily, because there
> seems to be other code that relies on this behavior (I can’t tell if that’s
> a bug or a feature).  What do you think would be way to fix this?
>
> Thanks,
> Kuba
>
> Author: kcc
> Date: Thu Mar  5 16:19:25 2015
> New Revision: 231413
>
> URL: http://llvm.org/viewvc/llvm-project?rev=231413&view=rev
> Log:
> [sanitizer] Reconstruct the function that dumps block/edge coverage, hopefully making it more robust. Also increase the allowed coverage size on 32-bit.
>
> Modified:
>     compiler-rt/trunk/lib/sanitizer_common/sanitizer_coverage_libcdep.cc
>     compiler-rt/trunk/test/asan/TestCases/Linux/coverage-module-unloaded.cc
>     compiler-rt/trunk/test/asan/TestCases/Linux/coverage-sandboxing.cc
>     compiler-rt/trunk/test/asan/TestCases/Linux/coverage.cc
>
> Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_coverage_libcdep.cc
> URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_coverage_libcdep.cc?rev=231413&r1=231412&r2=231413&view=diff
> ==============================================================================
> --- compiler-rt/trunk/lib/sanitizer_common/sanitizer_coverage_libcdep.cc (original)
> +++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_coverage_libcdep.cc Thu Mar  5 16:19:25 2015
> @@ -79,6 +79,8 @@ class CoverageData {
>    void DumpTrace();
>
>
>
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