Fix edit and continue in VS with hardware exceptions #76401
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There is a subtle bug in hardware exception handling in the runtime that causes the debugged process to crash when a user tries to use the "unwind to this frame" on the frame where the exception happened. This issue was introduced by the recent changes that modified hardware exception handling. The problem turned out to be in how we update the exception and context records in the HandleManagedFaultFilter when we re-raise the exception using RaiseException from the VEH. Updating the context is both not necessary and wrong. All we need to update is the `ExceptionAddress` in the `EXCEPTION_RECORD`, since the RaiseException puts the address of itself there and we need the address of the original access violation to be there. The context should stay untouched as we are unwinding from the RaiseException. The context copying was originally made to mimick the code in the `NakedThrowHelper` used before the exception handling change. That one needed the context update, as it was used to fix unwinding over the NakedThrowHelper that was a hijack helper. In the current state, nothing like that is needed. With this fix, the VS debugger works as expected.
jkotas
approved these changes
Sep 29, 2022
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/backport to release/7.0 |
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Started backporting to release/7.0: https://github.com/dotnet/runtime/actions/runs/3157197640 |
ghost
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There is a subtle bug in hardware exception handling in the runtime that causes the debugged process to crash when a user tries to use the "unwind to this frame" on the frame where the exception happened. This issue was introduced by the recent changes that modified hardware exception handling.
The problem turned out to be in how we update the exception and context records in the HandleManagedFaultFilter when we re-raise the exception using RaiseException from the VEH. Updating the context is both not necessary and wrong. All we need to update is the
ExceptionAddressin theEXCEPTION_RECORD, since the RaiseException puts the address of itself there and we need the address of the original access violation to be there.The context should stay untouched as we are unwinding from the RaiseException.
The context copying was originally made to mimick the code in the
NakedThrowHelperused before the exception handling change. That one needed the context update, as it was used to fix unwinding over the NakedThrowHelper that was a hijack helper. In the current state, nothing like that is needed.With this fix, the VS debugger works as expected.
Close #75762