Wasmtime GitHub notifications bot (Apr 18 2024 at 17:35): Wasmtime GitHub notifications bot (Apr 18 2024 at 17:35):elliottt opened PR #8401 from elliottt:trevor/riscv64-prologue-sp to bytecodealliance:main:
Instead of generating negative offsets to SP for clobbers and updating SP after clobbers have been spilled, eagerly bump SP and write the clobbers to positive offsets instead. This change should preserve the locations on the stack where the clobbers are written, so no changes were necessary for the epilogue.
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Wasmtime GitHub notifications bot (Apr 18 2024 at 17:37):elliottt updated PR #8401.
Wasmtime GitHub notifications bot (Apr 18 2024 at 17:38):elliottt updated PR #8401.
Wasmtime GitHub notifications bot (Apr 18 2024 at 17:39):elliottt updated PR #8401.
Wasmtime GitHub notifications bot (Apr 18 2024 at 17:41):elliottt has marked PR #8401 as ready for review.
Wasmtime GitHub notifications bot (Apr 18 2024 at 17:41):elliottt requested cfallin for a review on PR #8401.
Wasmtime GitHub notifications bot (Apr 18 2024 at 17:41):elliottt requested wasmtime-compiler-reviewers for a review on PR #8401.
Wasmtime GitHub notifications bot (Apr 18 2024 at 17:41):elliottt requested alexcrichton for a review on PR #8401.
Wasmtime GitHub notifications bot (Apr 18 2024 at 17:41):elliottt requested jameysharp for a review on PR #8401.
Wasmtime GitHub notifications bot (Apr 18 2024 at 19:01):jameysharp submitted PR review:
I believe this change is correct and also fixes a bug: We're generally not supposed to write important information, like clobber saves, beyond wherever the stack pointer points. A signal handler could run on our stack at any time and is allowed to overwrite anything outside our reserved portion of the stack. Some architectures provide a small "red zone" where we could get away with this, but we shouldn't rely on that.
For the same reason, the epilogue should also be updated to not adjust the stack pointer until it has already restored all the clobbers.
Would you update the commit message and PR description to mention this bug fix?
Wasmtime GitHub notifications bot (Apr 18 2024 at 19:52):elliottt updated PR #8401.
Last updated: Dec 23 2024 at 12:05 UTC