Disable ASAN in ffi_call_int functions #858
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The pattern for several of the architectures is for ffi_call_int to stack-allocate some arguments + the registers, and then ffi_call_$ARCH will pop the top of that structure into registers, and then adjust the stack pointer such that the alloca'd buffer _becomes_ the stack-passed arguments for the function being called. If libffi is compiled with ASAN, then there will be a redzone inserted after the alloca'd buffer which is marked as poisoned. This redzone appears beyond the end of $sp upon entry to the called function. If the called function does anything to use this stack memory, ASAN will notice that it's poisoned and report an error. This commit fixes the situation (on the architectures that I have access to) disabling instrumentation for ffi_call_int; that means there will be no alloca redzone left on the shadow-stack.
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The pattern for several of the architectures is for ffi_call_int to stack-allocate some arguments + the registers, and then ffi_call_$ARCH will pop the top of that structure into registers, and then adjust the stack pointer such that the alloca'd buffer becomes the stack-passed arguments for the function being called.
If libffi is compiled with ASAN, then there will be a redzone inserted after the alloca'd buffer which is marked as poisoned. This redzone appears beyond the end of $sp upon entry to the called function.
If the called function does anything to use this stack memory, ASAN will notice that it's poisoned and report an error.
This commit fixes the situation (on the architectures that I have access to) disabling instrumentation for ffi_call_int; that means there will be no alloca redzone left on the shadow-stack.