[release/8.0] Fix JIT_ByRefWriteBarrier unwinding on macOS x64 #91076
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Local labels in the JIT_ByRefWriteBarrier were not wrapped in the LOCAL_LABEL macro. That causes incorrect unwinding in case an access violation occurs inside of this function. The closest label before the failure point is considered to be the actual function, but it obviously doesn't have the right unwind info. Close #89585
jeffschwMSFT
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Aug 24, 2023
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jkotas
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Backport of #90967 to release/8.0
/cc @janvorli
Customer Impact
On macOS x64, processing null reference can sometimes result in an access violation in the runtime native code. The problem is caused by the libunwind not being able to unwind from the
JIT_ByRefWriteBarrierdue to labels inside of this asm function not being marked as local. On macOS, that means that the libunwind would look up the unwind info for the closest label before the failing instruction and that means there would be none.Testing
Running the coreclr failing test (it was disabled before) and CI testing
Risk
Low, the change just marks labels internal to the
JIT_ByRefWriteBarrier(and other functions in the same file for consistency) as local. That essentially just renames them by adding aLprefix that the compiler / linker understands.