From 50f4dd657a0fcf90aa8da8dc2794a8100ff4c37c Mon Sep 17 00:00:00 2001 From: Jisheng Zhang Date: Tue, 1 Nov 2022 02:29:43 +0800 Subject: [PATCH] riscv: vdso: fix build with llvm Even after commit 89fd4a1df829 ("riscv: jump_label: mark arguments as const to satisfy asm constraints"), building with CC_OPTIMIZE_FOR_SIZE + LLVM=1 can reproduce below build error: CC arch/riscv/kernel/vdso/vgettimeofday.o In file included from :4: In file included from lib/vdso/gettimeofday.c:5: In file included from include/vdso/datapage.h:17: In file included from include/vdso/processor.h:10: In file included from arch/riscv/include/asm/vdso/processor.h:7: In file included from include/linux/jump_label.h:112: arch/riscv/include/asm/jump_label.h:42:3: error: invalid operand for inline asm constraint 'i' " .option push \n\t" ^ 1 error generated. I think the problem is when "-Os" is passed as CFLAGS, it's removed by "CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os" which is introduced in commit e05d57dcb8c7 ("riscv: Fixup __vdso_gettimeofday broke dynamic ftrace"), thus no optimization at all for vgettimeofday.c arm64 does remove "-Os" as well, but it forces "-O2" after removing "-Os". I compared the generated vgettimeofday.o with "-O2" and "-Os", I think no big performance difference. So let's tell the kbuild not to remove "-Os" rather than follow arm64 style. vdso related performance can be improved a lot when building kernel with CC_OPTIMIZE_FOR_SIZE after this commit, ("-Os" VS no optimization) Fixes: e05d57dcb8c7 ("riscv: Fixup __vdso_gettimeofday broke dynamic ftrace") Signed-off-by: Jisheng Zhang Tested-by: Conor Dooley Link: https://lore.kernel.org/r/20221031182943.2453-1-jszhang@kernel.org Signed-off-by: Palmer Dabbelt --- arch/riscv/kernel/vdso/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile index f2e065671e4d..84ac0fe612e7 100644 --- a/arch/riscv/kernel/vdso/Makefile +++ b/arch/riscv/kernel/vdso/Makefile @@ -30,7 +30,7 @@ obj-y += vdso.o CPPFLAGS_vdso.lds += -P -C -U$(ARCH) # Disable -pg to prevent insert call site -CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os +CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) # Disable profiling and instrumentation for VDSO code GCOV_PROFILE := n