With KASAN enabled the kernel has two different memset() functions, one with KASAN checks (memset) and one without (__memset). KASAN uses some macro tricks to use the proper version where required. For example memset() calls in mm/slub.c are without KASAN checks, since they operate on poisoned slab object metadata. The issue is that clang emits memset() calls even when there is no memset() in the source code. They get linked with improper memset() implementation and the kernel fails to boot due to a huge amount of KASAN reports during early boot stages. The solution is to add -fno-builtin flag for files with KASAN_SANITIZE := n marker. Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> --- This patch should be applied on top of the v4 "kasan: support alloca, LLVM" patchset from Paul Lawrence. Makefile | 3 ++- scripts/Makefile.kasan | 3 +++ scripts/Makefile.lib | 2 +- 3 files changed, 6 insertions(+), 2 deletions(-) diff --git a/Makefile b/Makefile index bf5b8cbb9469..d45e31b293d0 100644 --- a/Makefile +++ b/Makefile @@ -432,7 +432,8 @@ export MAKE AWK GENKSYMS INSTALLKERNEL PERL PYTHON UTS_MACHINE export HOSTCXX HOSTCXXFLAGS LDFLAGS_MODULE CHECK CHECKFLAGS export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS LDFLAGS -export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE CFLAGS_KASAN CFLAGS_UBSAN +export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE +export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE CFLAGS_UBSAN export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan index dbbd4382f15a..db473309f136 100644 --- a/scripts/Makefile.kasan +++ b/scripts/Makefile.kasan @@ -39,4 +39,7 @@ else endif CFLAGS_KASAN += $(call cc-option, -fsanitize-address-use-after-scope) + +CFLAGS_KASAN_NOSANITIZE := $(call cc-option, -fno-builtin) + endif diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 1ca4dcd2d500..015aa9dbad86 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -121,7 +121,7 @@ endif ifeq ($(CONFIG_KASAN),y) _c_flags += $(if $(patsubst n%,, \ $(KASAN_SANITIZE_$(basetarget).o)$(KASAN_SANITIZE)y), \ - $(CFLAGS_KASAN)) + $(CFLAGS_KASAN), $(CFLAGS_KASAN_NOSANITIZE)) endif ifeq ($(CONFIG_UBSAN),y) -- 2.16.0.rc1.238.g530d649a79-goog -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
