linux-kernel - Re: [PATCH] riscv: Pass -mno-relax only on lld

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Message-ID: <CAKwvOd=yTio6SDG-dEEB1W3nQdZZNk67x_DsiedmC5t95P8XNg@mail.gmail.com>
Date:   Mon, 11 Jul 2022 10:38:25 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Fangrui Song <maskray@...gle.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv@...ts.infradead.org, Khem Raj <raj.khem@...il.com>,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] riscv: Pass -mno-relax only on lld < 15.0.0

On Sun, Jul 10, 2022 at 12:11 AM Fangrui Song <maskray@...gle.com> wrote:
>
> lld since
> https://github.com/llvm/llvm-project/commit/6611d58f5bbcbec77262d392e2923e1d680f6985
> (milestone: 15.0.0) has implemented some RISC-V linker relaxation.
> -mno-relax is no longer needed in KBUILD_CFLAGS/KBUILD_AFLAGS to
> suppress R_RISCV_ALIGN which older lld can not handle:
>
> ld.lld: error: capability.c:(.fixup+0x0): relocation R_RISCV_ALIGN requires unimplemented linker relaxation; recompile with -mno-relax but the .o is already compiled with -mno-relax
>
> Signed-off-by: Fangrui Song <maskray@...gle.com>

Thanks for implementing relaxation in LLD for RISC-V!

Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
Tested-by: Nick Desaulniers <ndesaulniers@...gle.com>

> ---
>  arch/riscv/Makefile | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> index 34cf8a598617..7e4ceb2a0981 100644
> --- a/arch/riscv/Makefile
> +++ b/arch/riscv/Makefile
> @@ -37,6 +37,7 @@ else
>  endif
>
>  ifeq ($(CONFIG_LD_IS_LLD),y)
> +ifeq ($(shell test $(CONFIG_LLD_VERSION) -lt 150000; echo $$?),0)
>         KBUILD_CFLAGS += -mno-relax
>         KBUILD_AFLAGS += -mno-relax
>  ifndef CONFIG_AS_IS_LLVM
> @@ -44,6 +45,7 @@ ifndef CONFIG_AS_IS_LLVM
>         KBUILD_AFLAGS += -Wa,-mno-relax
>  endif
>  endif
> +endif
>
>  # ISA string setting
>  riscv-march-$(CONFIG_ARCH_RV32I)       := rv32ima
> --
> 2.37.0.144.g8ac04bfd2-goog
>
>


-- 
Thanks,
~Nick Desaulniers