linux-kernel - Re: [PATCH v2 4/5] kasan: support LLVM-style asan parameters

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Date:   Thu, 30 Nov 2017 19:36:54 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Paul Lawrence <paullawrence@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <mmarek@...e.com>
Cc:     linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, linux-kbuild@...r.kernel.org,
        Matthias Kaehlcke <mka@...omium.org>,
        Michael Davidson <md@...gle.com>,
        Greg Hackmann <ghackmann@...gle.com>
Subject: Re: [PATCH v2 4/5] kasan: support LLVM-style asan parameters

On 11/30/2017 12:50 AM, Paul Lawrence wrote:
> Use cc-option to figure out whether the compiler's sanitizer uses
> LLVM-style parameters ("-mllvm -asan-foo=bar") or GCC-style parameters
> ("--param asan-foo=bar").
> 
> Signed-off-by: Greg Hackmann <ghackmann@...gle.com>
> Signed-off-by: Paul Lawrence <paullawrence@...gle.com>
> 
> ---
>  scripts/Makefile.kasan | 39 +++++++++++++++++++++++++++------------
>  1 file changed, 27 insertions(+), 12 deletions(-)
> 

It looks rather messy. Try the following patch.
Note, that I didn't add asan-instrument-allocas=1 because it has nothing to do
with LLVM-style params support.
asan-instrument-allocas should probably be in the patch that adds alloca() support.


From: Andrey Ryabinin <aryabinin@...tuozzo.com>
Subject: [PATCH] kasan/Makefile: Support LLVM style asan parameters.

LLVM doesn't understand GCC-style paramters ("--param asan-foo=bar"),
thus we currently we don't use inline/globals/stack instrumentation
when building the kernel with clang.

Add support for LLVM-style parameters ("-mllvm -asan-foo=bar") to
enable all KASAN features.

Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
---
 scripts/Makefile.kasan | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
index 1ce7115aa499..2af5977c394d 100644
--- a/scripts/Makefile.kasan
+++ b/scripts/Makefile.kasan
@@ -10,10 +10,7 @@ KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)
 
 CFLAGS_KASAN_MINIMAL := -fsanitize=kernel-address
 
-CFLAGS_KASAN := $(call cc-option, -fsanitize=kernel-address \
-		-fasan-shadow-offset=$(KASAN_SHADOW_OFFSET) \
-		--param asan-stack=1 --param asan-globals=1 \
-		--param asan-instrumentation-with-call-threshold=$(call_threshold))
+cc-param = $(call cc-option, --param $(1)) $(call cc-option, -mllvm -$(1))
 
 ifeq ($(call cc-option, $(CFLAGS_KASAN_MINIMAL) -Werror),)
    ifneq ($(CONFIG_COMPILE_TEST),y)
@@ -21,13 +18,23 @@ ifeq ($(call cc-option, $(CFLAGS_KASAN_MINIMAL) -Werror),)
             -fsanitize=kernel-address is not supported by compiler)
    endif
 else
-    ifeq ($(CFLAGS_KASAN),)
-        ifneq ($(CONFIG_COMPILE_TEST),y)
-            $(warning CONFIG_KASAN: compiler does not support all options.\
-                Trying minimal configuration)
-        endif
-        CFLAGS_KASAN := $(CFLAGS_KASAN_MINIMAL)
-    endif
+   # -fasan-shadow-offset fails without -fsanitize
+   CFLAGS_KASAN_SHADOW := $(call cc-option, -fsanitize=kernel-address \
+			-fasan-shadow-offset=$(KASAN_SHADOW_OFFSET), \
+			$(call cc-option, -fsanitize=kernel-address \
+			-mllvm -asan-mapping-offset=$(KASAN_SHADOW_OFFSET)))
+
+   ifeq ($(CFLAGS_KASAN_SHADOW),)
+      CFLAGS_KASAN := $(CFLAGS_KASAN_MINIMAL)
+   else
+      # Now add all the compiler specific options that are valid standalone
+      CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
+	$(call cc-param,asan-globals=1) \
+	$(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
+	$(call cc-param,asan-stack=1) \
+	$(call cc-param,asan-use-after-scope=1)
+   endif
+
 endif
 
 CFLAGS_KASAN += $(call cc-option, -fsanitize-address-use-after-scope)
-- 
2.13.6