[release/10.0] Fix ARM64 ThreadAbort issue #120579
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There is a problem with RtlRestoreContext not restoring context during ThreadAbort if that abort comes from injected APC callback on ARM64 and the processor supports SVE. In that case, the context provided by the APC callback can contain XSTATE and when we start walking stack from that context, we copy that context into the REGDISPLAY. The problem is that we copy the ContextFlags without changes, so if they contained CONTEXT_XSTATE flag, it is kept set even though the REGDISPLAY has only plain old CONTEXT without any xstate. When we call RtlRestoreContext in the ResumeAfterCatch, it fails because the XSTATE is not valid and so it returns. That's unexpected and we end up crashing with an assert. The fix clears the CONTEXT_XSTATE in ResumableFrame::UpdateRegDisplay so that the REGDISPLAY ContextFlags are validly representing the context. Close #120437
janvorli
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area-ExceptionHandling-coreclr
Servicing-consider
jkotas
approved these changes
Oct 9, 2025
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@tannergooding, @EgorBo, please review this backport PR. |
agocke
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EgorBo
approved these changes
Oct 13, 2025
tannergooding
approved these changes
Oct 13, 2025
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The test failures are known issue #120577 |
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/ba-g failures known |
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Backport of #120552 to release/10.0
/cc @janvorli
Customer Impact
There is a problem with RtlRestoreContext not restoring context during thread abort if that abort comes from injected APC callback on ARM64 and the processor supports SVE. In that case, the context provided by the APC callback can contain XSTATE and when we start walking stack from that context, we copy that context into the REGDISPLAY. The problem is that we copy the ContextFlags without changes, so if they contained CONTEXT_XSTATE flag, it is kept set even though the REGDISPLAY has only plain old CONTEXT without any XSTATE.
When we call RtlRestoreContext in the ResumeAfterCatch, it fails because the XSTATE is not valid and so it returns. That's unexpected and the runtime ends up crashing with an assert in debug/checked build and causing some unexpected behavior and random crashes in release builds.
Regression
Testing
CI tests - libraries tests contain controlled execution tests that started to fail on some CI runs, probably due to added machines with enabled SVE or upgraded Windows with enabled SVE.
Risk
Low, the fix just removes the CONTEXT_XSTATE from the copied context and makes it valid.