Re: [PATCH 1/4] arm64/sve: Remove bitrotted comment about syscall behaviour
flat view
From: Dave Martin <Dave.Martin@arm.com>
Date: 2024-01-23 15:44:27
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On Mon, Jan 22, 2024 at 08:41:51PM +0000, Mark Brown wrote:
When we documented that we always clear state not shared with FPSIMD we
Where / when?
quoted hunk ↗ jump to hunk
didn't catch all of the places that mentioned that state might not be cleared, remove a lingering reference. Reported-by: Edmund Grimley-Evans <redacted> Signed-off-by: Mark Brown <broonie@kernel.org> --- Documentation/arch/arm64/sve.rst | 5 ----- 1 file changed, 5 deletions(-)diff --git a/Documentation/arch/arm64/sve.rst b/Documentation/arch/arm64/sve.rst index 0d9a426e9f85..b45a2da19bf1 100644 --- a/Documentation/arch/arm64/sve.rst +++ b/Documentation/arch/arm64/sve.rst@@ -117,11 +117,6 @@ the SVE instruction set architecture. * The SVE registers are not used to pass arguments to or receive results from any syscall. -* In practice the affected registers/bits will be preserved or will be replaced - with zeros on return from a syscall, but userspace should not make - assumptions about this. The kernel behaviour may vary on a case-by-case - basis. -
This was originally an intentionally conservative statement, to allow the kernel the flexibility to relax the register zeroing behaviour in the future. It would have permitted not always disabling a task's SVE across a syscall, for example. There were some concerns about security and testability that meant that we didn't use this flexibility to begin with. If we are making an irrevocable commitment not to use this flexibility ever, then this comment can go, but if we're not totally sure then I think it would be harmless to keep it (?) (Feel free to point me to the relevant past discussion that I may have missed.) [...] Cheers ---Dave _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel