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| author | Jisheng Zhang <jszhang@kernel.org> | 2022-10-31 19:29:43 +0100 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@rivosinc.com> | 2022-11-10 22:58:36 +0100 |
| commit | 50f4dd657a0fcf90aa8da8dc2794a8100ff4c37c (patch) | |
| tree | 99f4f3209d58c21ae11641528bd86414f4ef0641 /arch/riscv/kernel/vdso | |
| parent | riscv: process: fix kernel info leakage (diff) | |
| download | linux-50f4dd657a0fcf90aa8da8dc2794a8100ff4c37c.tar.xz linux-50f4dd657a0fcf90aa8da8dc2794a8100ff4c37c.zip | |
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 <built-in>: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 = $(CC_FLAGS_FTRACE) -Os" which is
introduced in commit e05d57dcb8c7 ("riscv: Fixup __vdso_gettimeofday
broke dynamic ftrace"), thus no optimization at all for vgettimeofday.c
arm64 does remove "-Os" as well, but it forces "-O2" after removing
"-Os".
I compared the generated vgettimeofday.o with "-O2" and "-Os",
I think no big performance difference. So let's tell the kbuild not
to remove "-Os" rather than follow arm64 style.
vdso related performance can be improved a lot when building kernel with
CC_OPTIMIZE_FOR_SIZE after this commit, ("-Os" VS no optimization)
Fixes: e05d57dcb8c7 ("riscv: Fixup __vdso_gettimeofday broke dynamic ftrace")
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20221031182943.2453-1-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'arch/riscv/kernel/vdso')
| -rw-r--r-- | arch/riscv/kernel/vdso/Makefile | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile index f2e065671e4d..84ac0fe612e7 100644 --- a/arch/riscv/kernel/vdso/Makefile +++ b/arch/riscv/kernel/vdso/Makefile @@ -30,7 +30,7 @@ obj-y += vdso.o CPPFLAGS_vdso.lds += -P -C -U$(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 |