linux-kernel - Re: [PATCH] riscv: vdso: fix and clean-up Makefile

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Message-ID: <mhng-847a8bb0-7c9a-446a-971c-ede38543cf56@palmerdabbelt-glaptop>
Date:   Thu, 22 Apr 2021 20:00:19 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     jszhang3@...l.ustc.edu.cn
CC:     Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        masahiroy@...nel.org
Subject:     Re: [PATCH] riscv: vdso: fix and clean-up Makefile

On Fri, 02 Apr 2021 06:29:08 PDT (-0700), jszhang3@...l.ustc.edu.cn wrote:
> From: Jisheng Zhang <jszhang@...nel.org>
>
> Running "make" on an already compiled kernel tree will rebuild the
> kernel even without any modifications:
>
>   CALL    linux/scripts/checksyscalls.sh
>   CALL    linux/scripts/atomic/check-atomics.sh
>   CHK     include/generated/compile.h
>   SO2S    arch/riscv/kernel/vdso/vdso-syms.S
>   AS      arch/riscv/kernel/vdso/vdso-syms.o
>   AR      arch/riscv/kernel/vdso/built-in.a
>   AR      arch/riscv/kernel/built-in.a
>   AR      arch/riscv/built-in.a
>   GEN     .version
>   CHK     include/generated/compile.h
>   UPD     include/generated/compile.h
>   CC      init/version.o
>   AR      init/built-in.a
>   LD      vmlinux.o
>
> The reason is "Any target that utilizes if_changed must be listed in
> $(targets), otherwise the command line check will fail, and the target
> will always be built" as explained by Documentation/kbuild/makefiles.rst
>
> Fix this build bug by adding vdso-syms.S to $(targets)
>
> At the same time, there are two trivial clean up modifications:
>
> - the vdso-dummy.o is not needed any more after so remove it.
>
> - vdso.lds is a generated file, so it should be prefixed with
>   $(obj)/ instead of $(src)/
>
> Fixes: c2c81bb2f691 ("RISC-V: Fix the VDSO symbol generaton for binutils-2.35+")
> Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
> ---
>  arch/riscv/kernel/vdso/Makefile | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
> index 71a315e73cbe..7b9f505ba82f 100644
> --- a/arch/riscv/kernel/vdso/Makefile
> +++ b/arch/riscv/kernel/vdso/Makefile
> @@ -23,7 +23,7 @@ ifneq ($(c-gettimeofday-y),)
>  endif
>
>  # Build rules
> -targets := $(obj-vdso) vdso.so vdso.so.dbg vdso.lds vdso-dummy.o
> +targets := $(obj-vdso) vdso.so vdso.so.dbg vdso.lds vdso-syms.S
>  obj-vdso := $(addprefix $(obj)/, $(obj-vdso))
>
>  obj-y += vdso.o vdso-syms.o
> @@ -42,7 +42,7 @@ $(obj)/vdso.o: $(obj)/vdso.so
>
>  # link rule for the .so file, .lds has to be first
>  SYSCFLAGS_vdso.so.dbg = $(c_flags)
> -$(obj)/vdso.so.dbg: $(src)/vdso.lds $(obj-vdso) FORCE
> +$(obj)/vdso.so.dbg: $(obj)/vdso.lds $(obj-vdso) FORCE
>  	$(call if_changed,vdsold)
>  SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \
>  	-Wl,--build-id=sha1 -Wl,--hash-style=both

Thanks, this is on for-next.