From b065373b2a48fc6cf9e1c03bb8ee61120ec78aad Mon Sep 17 00:00:00 2001 From: Kuan-Ying Lee Date: Wed, 1 Dec 2021 11:40:10 +0800 Subject: [PATCH] arm64: update PAC description for kernel Remove the paragraph which has nothing to do with the kernel and add PAC description related to kernel. Suggested-by: Mark Rutland Signed-off-by: Kuan-Ying Lee Link: https://lore.kernel.org/r/20211201034014.20048-1-Kuan-Ying.Lee@mediatek.com Signed-off-by: Will Deacon --- Documentation/arm64/pointer-authentication.rst | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/Documentation/arm64/pointer-authentication.rst b/Documentation/arm64/pointer-authentication.rst index f127666ea3a81..e5dad2e40aa89 100644 --- a/Documentation/arm64/pointer-authentication.rst +++ b/Documentation/arm64/pointer-authentication.rst @@ -53,11 +53,10 @@ The number of bits that the PAC occupies in a pointer is 55 minus the virtual address size configured by the kernel. For example, with a virtual address size of 48, the PAC is 7 bits wide. -Recent versions of GCC can compile code with APIAKey-based return -address protection when passed the -msign-return-address option. This -uses instructions in the HINT space (unless -march=armv8.3-a or higher -is also passed), and such code can run on systems without the pointer -authentication extension. +When ARM64_PTR_AUTH_KERNEL is selected, the kernel will be compiled +with HINT space pointer authentication instructions protecting +function returns. Kernels built with this option will work on hardware +with or without pointer authentication support. In addition to exec(), keys can also be reinitialized to random values using the PR_PAC_RESET_KEYS prctl. A bitmask of PR_PAC_APIAKEY, -- 2.39.5