arch/riscv: fix trap sp restore logic #12717
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This fixes `tp` value of forked child in PROTECTED build to support vfork. Why? the optimized `dispatch_syscall` requires `tp` to hold the task TCB since commit e6973c7. Signed-off-by: Yanfeng Liu <[email protected]>
This fixes stack pointer restore logic to avoid parent stack corruption by forked child in PROTECTED build. Signed-off-by: Yanfeng Liu <[email protected]>
lupyuen
approved these changes
Jul 17, 2024
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Tested OK on Milk-V Duo S SBC and Ox64 BL808 Emulator. Thanks!
jerpelea
approved these changes
Jul 17, 2024
yf13
changed the title
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Summary
This amends pull #12435 and attempts to fix issue #12635 of PROTECTED build vfork failure since commit e6973c7.
Investigation revealed two separate issues:
The optimized
dispatch_syscallnow requires TP to be prepared, which normally isn't a problem. But for the very first run of the forked child, it was zero. So we need prepare it for the forked child specially before its first run.When returning from exception, the SP restored from stack normally works, As forked child stack is copied from parent, thus restored SP from child stack actually points to the parent stack area! So if child executes ealier that parent reaches the waitpid, parent will crash later due to corrupted stack. Unfortunately this is true with PROTECTED build now.
Impacts
riscv devices
Testing