On Sat, Jul 26, 2025 at 02:29:45PM -0700, Kees Cook wrote: > When building with CONFIG_KSTACK_ERASE=y and CONFIG_ARM_ATAG_DTB_COMPAT=y, > the compressed boot environment encounters an undefined symbol error: > > ld.lld: error: undefined symbol: __sanitizer_cov_stack_depth > >>> referenced by atags_to_fdt.c:135 > > This occurs because the compiler instruments the atags_to_fdt() function > with sanitizer coverage calls, but the minimal compressed boot environment > lacks access to sanitizer runtime support. > > The compressed boot environment already disables stack protector with > -fno-stack-protector. Similarly disable sanitizer coverage by adding > $(DISABLE_KSTACK_ERASE) to the general compiler flags (and remove it > from the one place it was noticed before), which contains the appropriate > flags to prevent sanitizer instrumentation. > > This follows the same pattern used in other early boot contexts where > sanitizer runtime support is unavailable. > > Reported-by: Linux Kernel Functional Testing <l...@linaro.org> > Closes: > https://lore.kernel.org/all/CA+G9fYtBk8qnpWvoaFwymCx5s5i-5KXtPGpmf=_+ukjddco...@mail.gmail.com > Reported-by: Nathan Chancellor <nat...@kernel.org> > Closes: https://lore.kernel.org/all/20250726004313.GA3650901@ax162 > Suggested-by: Nathan Chancellor <nat...@kernel.org> > Signed-off-by: Kees Cook <k...@kernel.org>
Tested-by: Nathan Chancellor <nat...@kernel.org> > --- > arch/arm/boot/compressed/Makefile | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm/boot/compressed/Makefile > b/arch/arm/boot/compressed/Makefile > index f9075edfd773..a159120d1e42 100644 > --- a/arch/arm/boot/compressed/Makefile > +++ b/arch/arm/boot/compressed/Makefile > @@ -9,7 +9,6 @@ OBJS = > > HEAD = head.o > OBJS += misc.o decompress.o > -CFLAGS_decompress.o += $(DISABLE_KSTACK_ERASE) > ifeq ($(CONFIG_DEBUG_UNCOMPRESS),y) > OBJS += debug.o > AFLAGS_head.o += -DDEBUG > @@ -96,6 +95,7 @@ KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING > > ccflags-y := -fpic $(call cc-option,-mno-single-pic-base,) -fno-builtin \ > -I$(srctree)/scripts/dtc/libfdt -fno-stack-protector \ > + $(DISABLE_KSTACK_ERASE) \ > -I$(obj) > ccflags-remove-$(CONFIG_FUNCTION_TRACER) += -pg > asflags-y := -DZIMAGE > -- > 2.34.1 >
