Messages in this thread | | | Date | Wed, 13 Oct 2021 14:43:25 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] tools/nolibc: x86: Remove `r8`, `r9` and `r10` from the clobber list |
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On Wed, Oct 13, 2021 at 05:23:11AM +0700, Ammar Faizi wrote: > "Figure 3.4: Register Usage" is not the answer, if it were, nolibc.h > would be broken as it is missing "rdi", "rsi", "rdx" in the clobber list.
It is not about what happens in practice but what the contract is: syscall argument registers can potentially get clobbered and userspace should treat them as such. Because if the kernel decides to actually clobber them for whatever reason and some userspace thing thinks otherwise, then it is the userspace thing's problem as it doesn't adhere to the well known ABI.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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