linux-kernel - [PATCH] arm64/gcs: Fix outdated ptrace documentation

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Message-Id: <20241031-arm64-gcs-doc-disable-v1-1-d7f6ded62046@kernel.org>
Date: Thu, 31 Oct 2024 19:21:38 +0000
From: Mark Brown <broonie@...nel.org>
To: Catalin Marinas <catalin.marinas@....com>, 
 Will Deacon <will@...nel.org>, Jonathan Corbet <corbet@....net>
Cc: linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>
Subject: [PATCH] arm64/gcs: Fix outdated ptrace documentation

The ptrace documentation for GCS was written prior to the implementation of
clone3() when we still blocked enabling of GCS via ptrace. This restriction
was relaxed as part of implementing clone3() support since we implemented
support for the GCS not being managed by the kernel but the documentation
still mentions the restriction. Update the documentation to reflect what
was merged.

We have not yet merged clone3() itself but all the support other than in
clone() itself is there.

Fixes: 7058bf87cd59 ("arm64/gcs: Document the ABI for Guarded Control Stacks")
Signed-off-by: Mark Brown <broonie@...nel.org>
---
 Documentation/arch/arm64/gcs.rst | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/Documentation/arch/arm64/gcs.rst b/Documentation/arch/arm64/gcs.rst
index af58d9151cb72df9058ddccadb2602127b479c95..1f65a3193e7765dce9bfd6ad88b9fbd6a225ed86 100644
--- a/Documentation/arch/arm64/gcs.rst
+++ b/Documentation/arch/arm64/gcs.rst
@@ -204,11 +204,8 @@ When returning from a signal handler:
 * A new regset NT_ARM_GCS is defined for use with PTRACE_GETREGSET and
   PTRACE_SETREGSET.
 
-* Due to the complexity surrounding allocation and deallocation of stacks and
-  lack of practical application it is not possible to enable GCS via ptrace.
-  GCS may be disabled via the ptrace interface.
-
-* Other GCS modes may be configured via ptrace.
+* The GCS mode, including enable and disable, may be configured via ptrace.
+  If GCS is enabled via ptrace no new GCS will be allocated for the thread.
 
 * Configuration via ptrace ignores locking of GCS mode bits.
 

---
base-commit: 9b9be78258511e67767e4aa51f587cf22feb5065
change-id: 20241031-arm64-gcs-doc-disable-e40c0115570e

Best regards,
-- 
Mark Brown <broonie@...nel.org>