When trying to load modules built for RISC-V which include assembly files
the kernel loader errors with "unexpected relocation type 'R_RISCV_ALIGN'"
due to R_RISCV_ALIGN relocations being generated by the assembler.
The R_RISCV_ALIGN relocations can be removed at the expense of code space
by adding -mno-relax to gcc and as. In commit 7a8e7da42250138
("RISC-V: Fixes to module loading") -mno-relax is added to the build
variable KBUILD_CFLAGS_MODULE. See [1] for more info.
The issue is that when kbuild builds a .S file, it invokes gcc with
the -mno-relax flag, but this is not being passed through to the
assembler. Adding -Wa,-mno-relax to KBUILD_AFLAGS_MODULE ensures that
the assembler is invoked correctly. This may have now been fixed in
gcc[2] and this addition should not stop newer gcc and as from working.
[1] https://github.com/riscv/riscv-elf-psabi-doc/issues/183
[2] https://github.com/gcc-mirror/gcc/commit/3b0a7d624e64eeb81e4d5e8c62c46d86ef521857
Notes:
Signed-off-by: Ben Dooks <[email protected]>
Reviewed-by: Bin Meng <[email protected]>
---
arch/riscv/Makefile | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 1f5c03082976..fca40511a8c6 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -60,6 +60,7 @@ ifeq ($(CONFIG_PERF_EVENTS),y)
endif
KBUILD_CFLAGS_MODULE += $(call cc-option,-mno-relax)
+KBUILD_AFLAGS_MODULE += $(call as-option,-Wa$(comma)-mno-relax)
# GCC versions that support the "-mstrict-align" option default to allowing
# unaligned accesses. While unaligned accesses are explicitly allowed in the
--
2.35.1
On Sun, 29 May 2022 08:22:00 PDT (-0700), [email protected] wrote:
> When trying to load modules built for RISC-V which include assembly files
> the kernel loader errors with "unexpected relocation type 'R_RISCV_ALIGN'"
> due to R_RISCV_ALIGN relocations being generated by the assembler.
>
> The R_RISCV_ALIGN relocations can be removed at the expense of code space
> by adding -mno-relax to gcc and as. In commit 7a8e7da42250138
> ("RISC-V: Fixes to module loading") -mno-relax is added to the build
> variable KBUILD_CFLAGS_MODULE. See [1] for more info.
>
> The issue is that when kbuild builds a .S file, it invokes gcc with
> the -mno-relax flag, but this is not being passed through to the
> assembler. Adding -Wa,-mno-relax to KBUILD_AFLAGS_MODULE ensures that
> the assembler is invoked correctly. This may have now been fixed in
> gcc[2] and this addition should not stop newer gcc and as from working.
>
> [1] https://github.com/riscv/riscv-elf-psabi-doc/issues/183
> [2] https://github.com/gcc-mirror/gcc/commit/3b0a7d624e64eeb81e4d5e8c62c46d86ef521857
>
> Notes:
>
> Signed-off-by: Ben Dooks <[email protected]>
> Reviewed-by: Bin Meng <[email protected]>
> ---
> arch/riscv/Makefile | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> index 1f5c03082976..fca40511a8c6 100644
> --- a/arch/riscv/Makefile
> +++ b/arch/riscv/Makefile
> @@ -60,6 +60,7 @@ ifeq ($(CONFIG_PERF_EVENTS),y)
> endif
>
> KBUILD_CFLAGS_MODULE += $(call cc-option,-mno-relax)
> +KBUILD_AFLAGS_MODULE += $(call as-option,-Wa$(comma)-mno-relax)
>
> # GCC versions that support the "-mstrict-align" option default to allowing
> # unaligned accesses. While unaligned accesses are explicitly allowed in the
Sorry for being so slow here, I've gotten pretty buried and it wasn't
clear this was a fix. I put it in fixes with some tags.
Thanks!