linux-kernel - Re: [PATCH] RISC-V: vdso: Do not add missing symbols to version section in linker script

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Date:   Thu, 10 Nov 2022 15:17:19 -0800 (PST)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     nathan@...nel.org
CC:     Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
        Conor Dooley <conor@...nel.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, patches@...ts.linux.dev, nathan@...nel.org
Subject:     Re: [PATCH] RISC-V: vdso: Do not add missing symbols to version section in linker script

On Tue, 08 Nov 2022 09:13:23 PST (-0800), nathan@...nel.org wrote:
> Recently, ld.lld moved from '--undefined-version' to
> '--no-undefined-version' as the default, which breaks the compat vDSO
> build:
>
>   ld.lld: error: version script assignment of 'LINUX_4.15' to symbol '__vdso_gettimeofday' failed: symbol not defined
>   ld.lld: error: version script assignment of 'LINUX_4.15' to symbol '__vdso_clock_gettime' failed: symbol not defined
>   ld.lld: error: version script assignment of 'LINUX_4.15' to symbol '__vdso_clock_getres' failed: symbol not defined
>
> These symbols are not present in the compat vDSO or the regular vDSO for
> 32-bit but they are unconditionally included in the version section of
> the linker script, which is prohibited with '--no-undefined-version'.
>
> Fix this issue by only including the symbols that are actually exported
> in the version section of the linker script.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1756
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
>  arch/riscv/kernel/vdso/Makefile   | 3 +++
>  arch/riscv/kernel/vdso/vdso.lds.S | 2 ++
>  2 files changed, 5 insertions(+)
>
> diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
> index f2e065671e4d..82416ebf4cca 100644
> --- a/arch/riscv/kernel/vdso/Makefile
> +++ b/arch/riscv/kernel/vdso/Makefile
> @@ -28,6 +28,9 @@ obj-vdso := $(addprefix $(obj)/, $(obj-vdso))
>
>  obj-y += vdso.o
>  CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
> +ifneq ($(filter vgettimeofday, $(vdso-syms)),)
> +CPPFLAGS_vdso.lds += -DHAS_VGETTIMEOFDAY
> +endif
>
>  # Disable -pg to prevent insert call site
>  CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os
> diff --git a/arch/riscv/kernel/vdso/vdso.lds.S b/arch/riscv/kernel/vdso/vdso.lds.S
> index 01d94aae5bf5..150b1a572e61 100644
> --- a/arch/riscv/kernel/vdso/vdso.lds.S
> +++ b/arch/riscv/kernel/vdso/vdso.lds.S
> @@ -68,9 +68,11 @@ VERSION
>  	LINUX_4.15 {
>  	global:
>  		__vdso_rt_sigreturn;
> +#ifdef HAS_VGETTIMEOFDAY
>  		__vdso_gettimeofday;
>  		__vdso_clock_gettime;
>  		__vdso_clock_getres;
> +#endif
>  		__vdso_getcpu;
>  		__vdso_flush_icache;
>  	local: *;
>
> base-commit: f0c4d9fc9cc9462659728d168387191387e903cc

Thanks, this is on fixes.  Something is confusing b4, so I've merged it 
using the old flow -- hopefully that still works ;)