Support inline self modifying code #4165
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For reference, this is referring to #4161. |
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Needs a rebase. |
alyssarosenzweig
approved these changes
Dec 12, 2024
Frontends need to detect this in order to handle SMC within the current block (inline SMC) differently to regular SMC which can just reprotect and continue.
guest instruction Single instruction blocks need to be treated specially when inline SMC is detected, the frontend only needs to reprotect RWX and invalidate caches then continue execution as side effects from the SMC shouldn't be seen until the instruction executes.
When an SMC trap happens: reconstruct the context before the SMC write then compile the write as a single instruction block to reduce it to regular SMC. SMC where the writing instruction is the instruction being patched will hit the signal handler at most twice: the 1st will trigger the write to be compiled as a single instuction block, the 2nd will detect inline SMC of a single instruction block and then just take the usual invalidate+reprotect+continue step, avoiding a potential infinite loop of recompilation.
This is used to notify the JIT of e.g. memory writes by a debugger.
Sonicadvance1
approved these changes
Dec 12, 2024
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When an SMC trap happens: reconstruct the context before the SMC write then compile the write as a single instruction block to reduce it to regular SMC. SMC where the writing instruction is the instruction being patched will hit the signal handler at most twice: the 1st will trigger the write to be compiled as a single instuction block, the 2nd will detect inline SMC of a single instruction block and then just take the usual invalidate+reprotect+continue step, avoiding a potential infinite loop of recompilation.
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