linux-kernel - [PATCH v2] arm64: update PAC description for kernel

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Message-ID: <20211201034014.20048-1-Kuan-Ying.Lee@mediatek.com>
Date:   Wed, 1 Dec 2021 11:40:10 +0800
From:   Kuan-Ying Lee <Kuan-Ying.Lee@...iatek.com>
To:     Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Matthias Brugger <matthias.bgg@...il.com>
CC:     <chinwen.chang@...iatek.com>, <nicholas.tang@...iatek.com>,
        <james.hsu@...iatek.com>,
        Kuan-Ying Lee <Kuan-Ying.Lee@...iatek.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>
Subject: [PATCH v2] 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 <mark.rutland@....com>
Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@...iatek.com>
---
v1 -> v2:
  - Remove compiler option description
  - Add PAC description for kernel

 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 f127666ea3a8..e5dad2e40aa8 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,
-- 
2.18.0