linux-kernel - [PATCH 0/2] Noinstr fixes for K[CA]SAN with GCOV

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Message-ID: <20251208-gcov-inline-noinstr-v1-0-623c48ca5714@google.com>
Date: Mon, 08 Dec 2025 01:34:57 +0000
From: Brendan Jackman <jackmanb@...gle.com>
To: Andrey Ryabinin <ryabinin.a.a@...il.com>, Alexander Potapenko <glider@...gle.com>, 
	Andrey Konovalov <andreyknvl@...il.com>, Dmitry Vyukov <dvyukov@...gle.com>, 
	Vincenzo Frascino <vincenzo.frascino@....com>, Marco Elver <elver@...gle.com>, 
	Ard Biesheuvel <ardb@...nel.org>
Cc: kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org, 
	Brendan Jackman <jackmanb@...gle.com>
Subject: [PATCH 0/2] Noinstr fixes for K[CA]SAN with GCOV

Details:

 - ❯❯  clang --version
   Debian clang version 19.1.7 (3+build5)
   Target: x86_64-pc-linux-gnu
   Thread model: posix
   InstalledDir: /usr/lib/llvm-19/bin

 - Kernel config:

   https://gist.githubusercontent.com/bjackman/bbfdf4ec2e1dfd0e18657174f0537e2c/raw/a88dcc6567d14c69445e7928a7d5dfc23ca9f619/gistfile0.txt

Note I also get this error:

vmlinux.o: warning: objtool: set_ftrace_ops_ro+0x3b: relocation to !ENDBR: machine_kexec_prepare+0x810

That one's a total mystery to me. I guess it's better to "fix" the SEV
one independently rather than waiting until I know how to fix them both.

Note I also mentioned other similar errors in [0]. Those errors don't
exist in Linus' master and I didn't note down where I saw them. Either
they have since been fixed, or I observed them in Google's internal
codebase where they were instroduced downstream.

This is a successor to [1] but I haven't called it a v2 because it's a
totally different solution. Thanks to Ard for the guidance and
corrections.

[0] https://lore.kernel.org/all/DERNCQGNRITE.139O331ACPKZ9@google.com/

[1] https://lore.kernel.org/all/20251117-b4-sev-gcov-objtool-v1-1-54f7790d54df@google.com/

Signed-off-by: Brendan Jackman <jackmanb@...gle.com>
---
Brendan Jackman (2):
      kasan: mark !__SANITIZE_ADDRESS__ stubs __always_inline
      kcsan: mark !__SANITIZE_THREAD__ stub __always_inline

 include/linux/kasan-checks.h | 4 ++--
 include/linux/kcsan-checks.h | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)
---
base-commit: 67a454e6b1c604555c04501c77b7fedc5d98a779
change-id: 20251208-gcov-inline-noinstr-1550cfee445c

Best regards,
-- 
Brendan Jackman <jackmanb@...gle.com>