linux-kernel - [PATCH 2/3] powerpc: Fix use of '-mabi=elfv2' with clang

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Message-Id: <20230118-ppc64-elfv2-llvm-v1-2-b9e2ec9da11d@kernel.org>
Date:   Wed, 15 Feb 2023 11:41:16 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     mpe@...erman.id.au
Cc:     npiggin@...il.com, christophe.leroy@...roup.eu,
        erhard_f@...lbox.org, nathan@...nel.org, ndesaulniers@...gle.com,
        trix@...hat.com, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        patches@...ts.linux.dev
Subject: [PATCH 2/3] powerpc: Fix use of '-mabi=elfv2' with clang

'-mabi=elfv2' is not added to clang's invocations when
CONFIG_PPC64_ELF_ABI_V2 is enabled, resulting in the generation of elfv1
code, as evidenced by the orphan section warnings/errors:

  ld.lld: error: vmlinux.a(arch/powerpc/kernel/prom_init.o):(.opd) is being placed in '.opd'
  ld.lld: error: vmlinux.a(init/main.o):(.opd) is being placed in '.opd'
  ld.lld: error: vmlinux.a(init/version.o):(.opd) is being placed in '.opd'

To resolve this, add '-mabi=elfv2' to CFLAGS with clang. This uncovers
an issue in the 32-bit vDSO:

  error: unknown target ABI 'elfv2'

The ELFv2 ABI cannot be used when building code for a 32-bit target. To
resolve this, just remove the '-mabi' flags from the assembler flags, as
it was only needed for preprocessing (the _CALL_ELF macro) but this was
cleaned up in commit 5b89492c03e5 ("powerpc: Finalise cleanup around ABI
use").

Tested-by: "Erhard F." <erhard_f@...lbox.org
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
 arch/powerpc/Makefile | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index dc4cbf0a5ca9..3f2dd930e3cd 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -123,14 +123,12 @@ endif
 endif
 
 CFLAGS-$(CONFIG_PPC64)	:= $(call cc-option,-mtraceback=no)
-ifndef CONFIG_CC_IS_CLANG
 ifdef CONFIG_PPC64_ELF_ABI_V2
 CFLAGS-$(CONFIG_PPC64)	+= $(call cc-option,-mabi=elfv2,$(call cc-option,-mcall-aixdesc))
-AFLAGS-$(CONFIG_PPC64)	+= $(call cc-option,-mabi=elfv2)
 else
+ifndef CONFIG_CC_IS_CLANG
 CFLAGS-$(CONFIG_PPC64)	+= $(call cc-option,-mabi=elfv1)
 CFLAGS-$(CONFIG_PPC64)	+= $(call cc-option,-mcall-aixdesc)
-AFLAGS-$(CONFIG_PPC64)	+= $(call cc-option,-mabi=elfv1)
 endif
 endif
 CFLAGS-$(CONFIG_PPC64)	+= $(call cc-option,-mcmodel=medium,$(call cc-option,-mminimal-toc))

-- 
2.39.2