linux-kernel - [PATCH early RFC 1/4] kbuild: kasan,kcsan: refactor out enablement check

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Message-Id: <20250804-kasan-via-kcsan-v1-1-823a6d5b5f84@google.com>
Date: Mon, 04 Aug 2025 21:17:05 +0200
From: Jann Horn <jannh@...gle.com>
To: Masahiro Yamada <masahiroy@...nel.org>, 
 Nathan Chancellor <nathan@...nel.org>, 
 Nicolas Schier <nicolas.schier@...ux.dev>, 
 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>, 
 Andrew Morton <akpm@...ux-foundation.org>, Marco Elver <elver@...gle.com>, 
 Christoph Lameter <cl@...two.org>, David Rientjes <rientjes@...gle.com>, 
 Vlastimil Babka <vbabka@...e.cz>, Roman Gushchin <roman.gushchin@...ux.dev>, 
 Harry Yoo <harry.yoo@...cle.com>
Cc: linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, 
 kasan-dev@...glegroups.com, linux-mm@...ck.org, 
 Jann Horn <jannh@...gle.com>
Subject: [PATCH early RFC 1/4] kbuild: kasan,kcsan: refactor out enablement
 check

In preparation for making the logic for enabling KASAN/KCSAN compiler
instrumentation more complicated, refactor the existing logic to be more
readable and (for KASAN) less repetitive.

Signed-off-by: Jann Horn <jannh@...gle.com>
---
 scripts/Makefile.lib | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 1d581ba5df66..017c9801b6bb 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -52,14 +52,12 @@ endif
 # Enable address sanitizer flags for kernel except some files or directories
 # we don't want to check (depends on variables KASAN_SANITIZE_obj.o, KASAN_SANITIZE)
 #
+is-kasan-compatible = $(patsubst n%,, \
+	$(KASAN_SANITIZE_$(target-stem).o)$(KASAN_SANITIZE)$(is-kernel-object))
 ifeq ($(CONFIG_KASAN),y)
 ifneq ($(CONFIG_KASAN_HW_TAGS),y)
-_c_flags += $(if $(patsubst n%,, \
-		$(KASAN_SANITIZE_$(target-stem).o)$(KASAN_SANITIZE)$(is-kernel-object)), \
-		$(CFLAGS_KASAN), $(CFLAGS_KASAN_NOSANITIZE))
-_rust_flags += $(if $(patsubst n%,, \
-		$(KASAN_SANITIZE_$(target-stem).o)$(KASAN_SANITIZE)$(is-kernel-object)), \
-		$(RUSTFLAGS_KASAN))
+_c_flags += $(if $(is-kasan-compatible), $(CFLAGS_KASAN), $(CFLAGS_KASAN_NOSANITIZE))
+_rust_flags += $(if $(is-kasan-compatible), $(RUSTFLAGS_KASAN))
 endif
 endif
 
@@ -94,10 +92,10 @@ endif
 # Enable KCSAN flags except some files or directories we don't want to check
 # (depends on variables KCSAN_SANITIZE_obj.o, KCSAN_SANITIZE)
 #
+is-kcsan-compatible = $(patsubst n%,, \
+	$(KCSAN_SANITIZE_$(target-stem).o)$(KCSAN_SANITIZE)$(is-kernel-object))
 ifeq ($(CONFIG_KCSAN),y)
-_c_flags += $(if $(patsubst n%,, \
-	$(KCSAN_SANITIZE_$(target-stem).o)$(KCSAN_SANITIZE)$(is-kernel-object)), \
-	$(CFLAGS_KCSAN))
+_c_flags += $(if $(is-kcsan-compatible), $(CFLAGS_KCSAN))
 # Some uninstrumented files provide implied barriers required to avoid false
 # positives: set KCSAN_INSTRUMENT_BARRIERS for barrier instrumentation only.
 _c_flags += $(if $(patsubst n%,, \

-- 
2.50.1.565.gc32cd1483b-goog