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riscv: add as-options for modules with assembly compontents

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commit c1f6eff304e4dfa4558b6a8c6b2d26a91db6c998 upstream.

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 7a8e7da422
("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] 3b0a7d624e

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Link: https://lore.kernel.org/r/20220529152200.609809-1-ben.dooks@codethink.co.uk
Fixes: ab1ef68e54 ("RISC-V: Add sections of PLT and GOT for kernel module")
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ben Dooks 2022-05-29 16:22:00 +01:00 committed by Greg Kroah-Hartman
parent 31f3bb363a
commit 15155fa898
1 changed files with 1 additions and 0 deletions
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arch/riscv/Makefile
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@ -73,6 +73,7 @@ ifeq ($(CONFIG_PERF_EVENTS),y)
endif endif
KBUILD_CFLAGS_MODULE += $(call cc-option,-mno-relax) 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 # GCC versions that support the "-mstrict-align" option default to allowing
# unaligned accesses. While unaligned accesses are explicitly allowed in the # unaligned accesses. While unaligned accesses are explicitly allowed in the