winch: restore aarch64 frame pointer before advancing SP - #14516
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saulecabrera merged 2 commits intoOct 5, 2026
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Compute the empty tail callee entry SP in a scratch register, then reload the saved FP before releasing the old frame. This prevents a signal handler from overwriting the saved FP before it is read. Add disassembly coverage for both small and large entry-SP offsets. Fixes bytecodealliance#14503.
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saulecabrera
reviewed
Oct 4, 2026
Use a common helper to calculate the callee entry SP, restore frame state, and then update SP for empty and resizing tail calls. This keeps their frame restoration ordering from drifting.
saulecabrera
approved these changes
Oct 5, 2026
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When a function with stack arguments tail-calls a callee with no stack arguments, Winch’s AArch64 backend advances SP past the saved frame pointer before reloading it. A signal handler running between those instructions can overwrite the saved FP.
This PR computes the callee’s entry SP in a scratch register, restores FP while the old frame is still protected, and then updates SP.
Fixes #14503.