[PATCH] riscv: Pass -mno-relax only on lld < 15.0.0

[PATCH] riscv: Pass -mno-relax only on lld < 15.0.0

[Fangrui Song]

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@google.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

Re: [PATCH] riscv: Pass -mno-relax only on lld < 15.0.0

[Nathan Chancellor]

On Sun, Jul 10, 2022 at 12:11:17AM -0700, Fangrui Song 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@google.com>

ld.lld 14 and 15 both continue to link kernels and I have no issues
booting them in QEMU.

Tested-by: Nathan Chancellor <nathan@kernel.org>

> ---
>  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
> 
> 

Re: [PATCH] riscv: Pass -mno-relax only on lld < 15.0.0

[Nick Desaulniers]

On Sun, Jul 10, 2022 at 12:11 AM Fangrui Song <maskray@google.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@google.com>

Thanks for implementing relaxation in LLD for RISC-V!

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

Re: [PATCH] riscv: Pass -mno-relax only on lld < 15.0.0

[Nathan Chancellor]

It does not look like this ever got picked up? Would it be possible to
pick it up for 6.1?

The original patch is at:

https://lore.kernel.org/20220710071117.446112-1-maskray@google.com/

Cheers,
Nathan

On Sun, Jul 10, 2022 at 12:11:17AM -0700, Fangrui Song 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@google.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
> 
>