linux-kernel - [PATCH v6 05/18] kasan: Fix inline mode for x86 tag-based mode

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Message-ID: <8681ee6683b1c65a1d5d65f21c66e63378806ba0.1761763681.git.m.wieczorretman@pm.me>
Date: Wed, 29 Oct 2025 19:06:49 +0000
From: Maciej Wieczor-Retman <m.wieczorretman@...me>
To: xin@...or.com, peterz@...radead.org, kaleshsingh@...gle.com, kbingham@...nel.org, akpm@...ux-foundation.org, nathan@...nel.org, ryabinin.a.a@...il.com, dave.hansen@...ux.intel.com, bp@...en8.de, morbo@...gle.com, jeremy.linton@....com, smostafa@...gle.com, kees@...nel.org, baohua@...nel.org, vbabka@...e.cz, justinstitt@...gle.com, wangkefeng.wang@...wei.com, leitao@...ian.org, jan.kiszka@...mens.com, fujita.tomonori@...il.com, hpa@...or.com, urezki@...il.com, ubizjak@...il.com, ada.coupriediaz@....com, nick.desaulniers+lkml@...il.com, ojeda@...nel.org, brgerst@...il.com, elver@...gle.com, pankaj.gupta@....com, glider@...gle.com, mark.rutland@....com, trintaeoitogc@...il.com, jpoimboe@...nel.org, thuth@...hat.com, pasha.tatashin@...een.com, dvyukov@...gle.com, jhubbard@...dia.com, catalin.marinas@....com, yeoreum.yun@....com, mhocko@...e.com, lorenzo.stoakes@...cle.com, samuel.holland@...ive.com, vincenzo.frascino@....com, bigeasy@...utronix.de, surenb@...gle.com,
	ardb@...nel.org, Liam.Howlett@...cle.com, nicolas.schier@...ux.dev, ziy@...dia.com, kas@...nel.org, tglx@...utronix.de, mingo@...hat.com, broonie@...nel.org, corbet@....net, andreyknvl@...il.com, maciej.wieczor-retman@...el.com, david@...hat.com, maz@...nel.org, rppt@...nel.org, will@...nel.org, luto@...nel.org
Cc: kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, x86@...nel.org, linux-kbuild@...r.kernel.org, linux-mm@...ck.org, llvm@...ts.linux.dev, linux-doc@...r.kernel.org, m.wieczorretman@...me
Subject: [PATCH v6 05/18] kasan: Fix inline mode for x86 tag-based mode

From: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>

The LLVM compiler uses hwasan-instrument-with-calls parameter to setup
inline or outline mode in tag-based KASAN. If zeroed, it means the
instrumentation implementation will be pasted into each relevant
location along with KASAN related constants during compilation. If set
to one all function instrumentation will be done with function calls
instead.

The default hwasan-instrument-with-calls value for the x86 architecture
in the compiler is "1", which is not true for other architectures.
Because of this, enabling inline mode in software tag-based KASAN
doesn't work on x86 as the kernel script doesn't zero out the parameter
and always sets up the outline mode.

Explicitly zero out hwasan-instrument-with-calls when enabling inline
mode in tag-based KASAN.

Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
Reviewed-by: Andrey Konovalov <andreyknvl@...il.com>
---
Changelog v6:
- Add Andrey's Reviewed-by tag.

Changelog v3:
- Add this patch to the series.

 scripts/Makefile.kasan | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
index 0ba2aac3b8dc..e485814df3e9 100644
--- a/scripts/Makefile.kasan
+++ b/scripts/Makefile.kasan
@@ -76,8 +76,11 @@ CFLAGS_KASAN := -fsanitize=kernel-hwaddress
 RUSTFLAGS_KASAN := -Zsanitizer=kernel-hwaddress \
 		   -Zsanitizer-recover=kernel-hwaddress
 
+# LLVM sets hwasan-instrument-with-calls to 1 on x86 by default. Set it to 0
+# when inline mode is enabled.
 ifdef CONFIG_KASAN_INLINE
 	kasan_params += hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET)
+	kasan_params += hwasan-instrument-with-calls=0
 else
 	kasan_params += hwasan-instrument-with-calls=1
 endif
-- 
2.51.0