Messages in this thread Patch in this message | | | From | WANG Xuerui <> | Subject | [PATCH v3] LoongArch: Replace -ffreestanding with finer-grained -fno-builtin's | Date | Sun, 6 Aug 2023 18:36:20 +0800 |
| |
From: WANG Xuerui <git@xen0n.name>
As explained by Nick in the original issue: the kernel usually does a good job of providing library helpers that have similar semantics as their ordinary userspace libc equivalents, but -ffreestanding disables such libcall optimization and other related features in the compiler, which can lead to unexpected things such as CONFIG_FORTIFY_SOURCE not working (!).
However, due to the desire for better control over unaligned accesses with respect to CONFIG_ARCH_STRICT_ALIGN, and also for avoiding the GCC bug https://gcc.gnu.org/PR109465, we do want to still disable optimizations for the memory libcalls (memcpy, memmove and memset for now). Use finer-grained -fno-builtin-* toggles to achieve this without losing source fortification and other libcall optimizations.
Closes: https://github.com/ClangBuiltLinux/linux/issues/1897 Reported-by: Nathan Chancellor <nathan@kernel.org> Suggested-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: WANG Xuerui <git@xen0n.name> ---
Changes in v3 (no functional changes):
- Move explanatory words mentioning -ffreestanding from the comments into commit message.
Changes in v2:
- Keep the memory operation builtins disabled, add comments, and tweak the commit message along the way.
arch/loongarch/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile index b1e5db51b61c..3a0a3b209fc1 100644 --- a/arch/loongarch/Makefile +++ b/arch/loongarch/Makefile @@ -83,7 +83,7 @@ KBUILD_CFLAGS_KERNEL += -fPIE LDFLAGS_vmlinux += -static -pie --no-dynamic-linker -z notext endif -cflags-y += -ffreestanding +cflags-y += -fno-builtin-memcpy -fno-builtin-memmove -fno-builtin-memset cflags-y += $(call cc-option, -mno-check-zero-division) load-y = 0x9000000000200000 -- 2.40.0
| |