[release/9.0-rc1] Remove CONTEXT_XSTATE in FaultingExceptionFrame::UpdateRegDisplay #106550
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Fixing the problem introduced by the previous attempt to fix that. The problem was that the CONTEXT_XSTATE contains not only the bit for the xstate, but also the architecture "id" (CONTEXT_AMD64, CONTEXT_ARM64, ...). I've verified this fix using the debugger tests that the previous change was breaking. There is a bug in updating REGDISPLAY from a faulting exception frame. The context stored in the frame can contain extended state, but we only copy the basic CONTEXT part. But we are not removing the CONTEXT_XSTATE flag. There was an issue found on arm64 Windows with SVE enabled. The context from a hardware exception contains the SVE extended state and when we resume after catch for the exception or start propagating it through native frames, the RtlRestoreContext uses some garbage to try to restore the extended state and ends up corrupting memory. The fix is to remove the CONTEXT_XSTATE flag from the context after we copy it to the REGDISPLAY. While we have hit this problem on Windows ARM64 with SVE only, I have made the same change for other targets that can have extended state too. Close #105483
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Backport of #106466 to release/9.0-rc1
/cc @janvorli
Customer Impact
There is a bug in updating
REGDISPLAYfrom a faulting exception frame. The context stored in the frame can contain extended state, but we only copy the basicCONTEXTpart. But we are not removing theCONTEXT_XSTATEflag. There was an issue found on arm64 Windows with SVE enabled by the folks working on enabling SVE on Windows. The context from a hardware exception contains the SVE extended state and when we resume after catch for the exception or start propagating it through native frames, theRtlRestoreContextuses some garbage to try to restore the extended state and ends up corrupting memory.Regression
Testing
The fix was verified on an actual SVE enabled Windows arm64 machine using a test provided by one of the folks working on the SVE enabling that was reliably failing without the fix.
Risk
Low. It just removes incorrect bit from the CONTEXT flags that would otherwise cause Windows to read garbage.