linux-kernel - [PATCH] riscv: add correct as-options for assembly in modules

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Date:   Wed,  8 Dec 2021 19:26:07 +0000
From:   Ben Dooks <ben.dooks@...ethink.co.uk>
To:     linux-kernel@...ts.codethink.co.uk, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Bin Meng <bmeng.cn@...il.com>,
        Ben Dooks <ben.dooks@...ethink.co.uk>
Subject: [PATCH] riscv: add correct as-options for assembly in modules

When trying to load modules built for riscv which include assembly
the kernel loader errors with "unexpected relocation type 'R_RISCV_ALIGN'"
due to R_RISCV_ALIGN relocations being generated by the assembler.

In commit 7a8e7da42250138 ("RISC-V: Fixes to module loading") the
CFLAGS have -mno-relax added. This however does not get applied to
KBUILD_AFLAGS_MODULE so when a module builds a .S file, the -mno-relax
is not passed and the above error is seen. Fix it by adding the flags
'-Wa,-mno-relax' to KBUILD_AFLAGS_MODULE.

This may have been fixed in gcc, in:
 https://github.com/gcc-mirror/gcc/commit/3b0a7d624e64eeb81e4d5e8c62c46d86ef521857

Signed-off-by: Ben Dooks <ben.dooks@...ethink.co.uk>
--
Changes since v1:
- added Bin Meng's review of the original patch
---
 arch/riscv/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 0289a97325d1..cf2ea9a1ac20 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -58,6 +58,7 @@ 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
-- 
2.33.0