Messages in this thread | | | Date | Mon, 31 Oct 2022 19:21:20 +0000 | From | Conor Dooley <> | Subject | Re: [PATCH] riscv: vdso: fix build with llvm |
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On Tue, Nov 01, 2022 at 02:29:43AM +0800, Jisheng Zhang wrote: > 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 fo > r inline asm constraint 'i' > " .option push \n\t" > ^ > 1 error generated.
Tested-by: Conor Dooley <conor.dooley@microchip.com>
> > I think the problem is when "-Os" is passed as CFLAGS, it's removed by > "CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os" which is > introduced in commit e05d57dcb8c7 ("riscv: Fixup __vdso_gettimeofday > broke dynamic ftrace"), thus no optimization at all for vgettimeofday.c > arm64 does remove "-Os" as well, but it forces "-O2" after removing > "-Os". > > I compared the generated vgettimeofday.o with "-O2" and "-Os", > I think no big performance difference. So let's tell the kbuild not > to remove "-Os" rather than follow arm64 style. > > vdso related performance can be improved a lot when building kernel with > CC_OPTIMIZE_FOR_SIZE after this commit, ("-Os" VS no optimization) > > Fixes: e05d57dcb8c7 ("riscv: Fixup __vdso_gettimeofday broke dynamic ftrace") > Signed-off-by: Jisheng Zhang <jszhang@kernel.org> > --- > arch/riscv/kernel/vdso/Makefile | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile > index f2e065671e4d..84ac0fe612e7 100644 > --- a/arch/riscv/kernel/vdso/Makefile > +++ b/arch/riscv/kernel/vdso/Makefile > @@ -30,7 +30,7 @@ obj-y += vdso.o > CPPFLAGS_vdso.lds += -P -C -U$(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 > -- > 2.37.2 >
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