[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
> 
> 

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

[kernel test robot]

BCC: lkp@intel.com
In-Reply-To: <20220710071117.446112-1-maskray@google.com>
References: <20220710071117.446112-1-maskray@google.com>
TO: Fangrui Song <maskray@google.com>
TO: Paul Walmsley <paul.walmsley@sifive.com>
TO: Palmer Dabbelt <palmer@dabbelt.com>
TO: Albert Ou <aou@eecs.berkeley.edu>
TO: linux-riscv@lists.infradead.org
CC: Khem Raj <raj.khem@gmail.com>
CC: linux-kernel@vger.kernel.org
CC: llvm@lists.linux.dev
CC: Fangrui Song <maskray@google.com>

Hi Fangrui,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v5.19-rc6 next-20220712]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Fangrui-Song/riscv-Pass-mno-relax-only-on-lld-15-0-0/20220710-151301
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git b1c428b6c3684ee8ddf4137d68b3e8d51d2a700f
config: riscv-rv32_defconfig (https://download.01.org/0day-ci/archive/20220713/202207131251.9wFgtqfN-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project e60b4fb2b777118c0ff664a6347851df14fcf75b)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install riscv cross compiling tool for clang build
        # apt-get install binutils-riscv-linux-gnu
        # https://github.com/intel-lab-lkp/linux/commit/9abe0b92e612c5b6c53d4658b46c60b75bbd39d3
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Fangrui-Song/riscv-Pass-mno-relax-only-on-lld-15-0-0/20220710-151301
        git checkout 9abe0b92e612c5b6c53d4658b46c60b75bbd39d3
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> ld.lld: error: fs/built-in.a(nfs/nfs3xdr.o):(function decode_wcc_data: .text+0x2ec4): relocation R_RISCV_RVC_JUMP out of range: -1079 is not in [-1024, 1023]; references decode_fattr3
   >>> referenced by nfs3xdr.c
   >>> defined in fs/built-in.a(nfs/nfs3xdr.o)

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp

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

[Fangrui Song]

On Tue, Jul 12, 2022 at 9:16 PM kernel test robot <lkp@intel.com> wrote:
>
> BCC: lkp@intel.com
> In-Reply-To: <20220710071117.446112-1-maskray@google.com>
> References: <20220710071117.446112-1-maskray@google.com>
> TO: Fangrui Song <maskray@google.com>
> TO: Paul Walmsley <paul.walmsley@sifive.com>
> TO: Palmer Dabbelt <palmer@dabbelt.com>
> TO: Albert Ou <aou@eecs.berkeley.edu>
> TO: linux-riscv@lists.infradead.org
> CC: Khem Raj <raj.khem@gmail.com>
> CC: linux-kernel@vger.kernel.org
> CC: llvm@lists.linux.dev
> CC: Fangrui Song <maskray@google.com>
>
> Hi Fangrui,
>
> Thank you for the patch! Yet something to improve:
>
> [auto build test ERROR on linus/master]
> [also build test ERROR on v5.19-rc6 next-20220712]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Fangrui-Song/riscv-Pass-mno-relax-only-on-lld-15-0-0/20220710-151301
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git b1c428b6c3684ee8ddf4137d68b3e8d51d2a700f
> config: riscv-rv32_defconfig (https://download.01.org/0day-ci/archive/20220713/202207131251.9wFgtqfN-lkp@intel.com/config)
> compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project e60b4fb2b777118c0ff664a6347851df14fcf75b)
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # install riscv cross compiling tool for clang build
>         # apt-get install binutils-riscv-linux-gnu
>         # https://github.com/intel-lab-lkp/linux/commit/9abe0b92e612c5b6c53d4658b46c60b75bbd39d3
>         git remote add linux-review https://github.com/intel-lab-lkp/linux
>         git fetch --no-tags linux-review Fangrui-Song/riscv-Pass-mno-relax-only-on-lld-15-0-0/20220710-151301
>         git checkout 9abe0b92e612c5b6c53d4658b46c60b75bbd39d3
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash
>
> If you fix the issue, kindly add following tag where applicable
> Reported-by: kernel test robot <lkp@intel.com>
>
> All errors (new ones prefixed by >>):
>
> >> ld.lld: error: fs/built-in.a(nfs/nfs3xdr.o):(function decode_wcc_data: .text+0x2ec4): relocation R_RISCV_RVC_JUMP out of range: -1079 is not in [-1024, 1023]; references decode_fattr3
>    >>> referenced by nfs3xdr.c
>    >>> defined in fs/built-in.a(nfs/nfs3xdr.o)
>
> --
> 0-DAY CI Kernel Test Service
> https://01.org/lkp
>

This exposed an issue about imprecise branch distance computation when
checking a call instruction referencing the same input section.
I'll fix lld.

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

[Fangrui Song]

On Tue, Jul 12, 2022 at 10:48 PM Fangrui Song <maskray@google.com> wrote:
>
> On Tue, Jul 12, 2022 at 9:16 PM kernel test robot <lkp@intel.com> wrote:
> >
> > BCC: lkp@intel.com
> > In-Reply-To: <20220710071117.446112-1-maskray@google.com>
> > References: <20220710071117.446112-1-maskray@google.com>
> > TO: Fangrui Song <maskray@google.com>
> > TO: Paul Walmsley <paul.walmsley@sifive.com>
> > TO: Palmer Dabbelt <palmer@dabbelt.com>
> > TO: Albert Ou <aou@eecs.berkeley.edu>
> > TO: linux-riscv@lists.infradead.org
> > CC: Khem Raj <raj.khem@gmail.com>
> > CC: linux-kernel@vger.kernel.org
> > CC: llvm@lists.linux.dev
> > CC: Fangrui Song <maskray@google.com>
> >
> > Hi Fangrui,
> >
> > Thank you for the patch! Yet something to improve:
> >
> > [auto build test ERROR on linus/master]
> > [also build test ERROR on v5.19-rc6 next-20220712]
> > [If your patch is applied to the wrong git tree, kindly drop us a note.
> > And when submitting patch, we suggest to use '--base' as documented in
> > https://git-scm.com/docs/git-format-patch#_base_tree_information]
> >
> > url:    https://github.com/intel-lab-lkp/linux/commits/Fangrui-Song/riscv-Pass-mno-relax-only-on-lld-15-0-0/20220710-151301
> > base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git b1c428b6c3684ee8ddf4137d68b3e8d51d2a700f
> > config: riscv-rv32_defconfig (https://download.01.org/0day-ci/archive/20220713/202207131251.9wFgtqfN-lkp@intel.com/config)
> > compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project e60b4fb2b777118c0ff664a6347851df14fcf75b)
> > reproduce (this is a W=1 build):
> >         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> >         chmod +x ~/bin/make.cross
> >         # install riscv cross compiling tool for clang build
> >         # apt-get install binutils-riscv-linux-gnu
> >         # https://github.com/intel-lab-lkp/linux/commit/9abe0b92e612c5b6c53d4658b46c60b75bbd39d3
> >         git remote add linux-review https://github.com/intel-lab-lkp/linux
> >         git fetch --no-tags linux-review Fangrui-Song/riscv-Pass-mno-relax-only-on-lld-15-0-0/20220710-151301
> >         git checkout 9abe0b92e612c5b6c53d4658b46c60b75bbd39d3
> >         # save the config file
> >         mkdir build_dir && cp config build_dir/.config
> >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash
> >
> > If you fix the issue, kindly add following tag where applicable
> > Reported-by: kernel test robot <lkp@intel.com>
> >
> > All errors (new ones prefixed by >>):
> >
> > >> ld.lld: error: fs/built-in.a(nfs/nfs3xdr.o):(function decode_wcc_data: .text+0x2ec4): relocation R_RISCV_RVC_JUMP out of range: -1079 is not in [-1024, 1023]; references decode_fattr3
> >    >>> referenced by nfs3xdr.c
> >    >>> defined in fs/built-in.a(nfs/nfs3xdr.o)
> >
> > --
> > 0-DAY CI Kernel Test Service
> > https://01.org/lkp
> >
>
> This exposed an issue about imprecise branch distance computation when
> checking a call instruction referencing the same input section.
> I'll fix lld.

This was an issue in the R_RISCV_CALL lld patch. I just fixed it in
https://github.com/llvm/llvm-project/commit/6b1d151fe3dc530195d8802f1ecc247c8235dd3a
.

It's unnecessary to adjust the commit message since riscv32/riscv64
kernels should work with the very first R_RISCV_ALIGN lld patch.