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

Palmer Dabbelt
2022-11-10T23:17:27Z

On Tue, 08 Nov 2022 09:13:23 PST (-0800), nathan@kernel.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@kernel.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 ;)