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Date:   Fri, 29 May 2020 21:12:25 +0200
Message-Id: <c2f0c8e4048852ae014f4a391d96ca42d27e3255.1590779332.git.andreyknvl@google.com>
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Subject: [PATCH v2] kasan: fix clang compilation warning due to stack protector
From:   Andrey Konovalov <andreyknvl@google.com>
To:     Andrew Morton <akpm@linux-foundation.org>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc:     Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Marco Elver <elver@google.com>, kasan-dev@googlegroups.com,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Qian Cai <cai@lca.pw>, Andrey Konovalov <andreyknvl@google.com>
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Sender: linux-kernel-owner@vger.kernel.org
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KASAN uses a single cc-option invocation to disable both conserve-stack
and stack-protector flags. The former flag is not present in Clang, which
causes cc-option to fail, and results in stack-protector being enabled.

Fix by using separate cc-option calls for each flag. Also collect all
flags in a variable to avoid calling cc-option multiple times for
different files.

Reported-by: Qian Cai <cai@lca.pw>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---

Changes v1 -> v2:
- Renamed CC_FLAGS_KASAN_CONFLICT to CC_FLAGS_KASAN_RUNTIME.

---
 mm/kasan/Makefile | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
index de3121848ddf..d532c2587731 100644
--- a/mm/kasan/Makefile
+++ b/mm/kasan/Makefile
@@ -15,14 +15,19 @@ CFLAGS_REMOVE_tags_report.o = $(CC_FLAGS_FTRACE)
 
 # Function splitter causes unnecessary splits in __asan_load1/__asan_store1
 # see: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63533
-CFLAGS_common.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
-CFLAGS_generic.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
-CFLAGS_generic_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
-CFLAGS_init.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
-CFLAGS_quarantine.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
-CFLAGS_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
-CFLAGS_tags.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
-CFLAGS_tags_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
+CC_FLAGS_KASAN_RUNTIME := $(call cc-option, -fno-conserve-stack)
+CC_FLAGS_KASAN_RUNTIME += $(call cc-option, -fno-stack-protector)
+# Disable branch tracing to avoid recursion.
+CC_FLAGS_KASAN_RUNTIME += -DDISABLE_BRANCH_PROFILING
+
+CFLAGS_common.o := $(CC_FLAGS_KASAN_RUNTIME)
+CFLAGS_generic.o := $(CC_FLAGS_KASAN_RUNTIME)
+CFLAGS_generic_report.o := $(CC_FLAGS_KASAN_RUNTIME)
+CFLAGS_init.o := $(CC_FLAGS_KASAN_RUNTIME)
+CFLAGS_quarantine.o := $(CC_FLAGS_KASAN_RUNTIME)
+CFLAGS_report.o := $(CC_FLAGS_KASAN_RUNTIME)
+CFLAGS_tags.o := $(CC_FLAGS_KASAN_RUNTIME)
+CFLAGS_tags_report.o := $(CC_FLAGS_KASAN_RUNTIME)
 
 obj-$(CONFIG_KASAN) := common.o init.o report.o
 obj-$(CONFIG_KASAN_GENERIC) += generic.o generic_report.o quarantine.o
-- 
2.27.0.rc0.183.gde8f92d652-goog