2022-07-10 07:57:33

by Fangrui Song

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

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 <[email protected]>
---
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

2022-07-11 17:55:51

by Nathan Chancellor

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

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 <[email protected]>

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

Tested-by: Nathan Chancellor <[email protected]>

> ---
> 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
>
>

2022-07-11 17:55:51

by Nick Desaulniers

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

On Sun, Jul 10, 2022 at 12:11 AM Fangrui Song <[email protected]> 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 <[email protected]>

Thanks for implementing relaxation in LLD for RISC-V!

Reviewed-by: Nick Desaulniers <[email protected]>
Tested-by: Nick Desaulniers <[email protected]>

> ---
> 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

2022-09-08 17:40:07

by Nathan Chancellor

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

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/[email protected]/

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 <[email protected]>
> ---
> 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
>
>