[PATCH] s390: vDSO: Drop '-fPIC' from LDFLAGS

From: Nathan Chancellor <nathan@kernel.org>
To: hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com
Cc: borntraeger@linux.ibm.com, svens@linux.ibm.com,
	ndesaulniers@google.com,  morbo@google.com,
	justinstitt@google.com, linux-s390@vger.kernel.org,
	 llvm@lists.linux.dev, patches@lists.linux.dev,
	 Nathan Chancellor <nathan@kernel.org>
Subject: [PATCH] s390: vDSO: Drop '-fPIC' from LDFLAGS
Date: Tue, 30 Jan 2024 20:14:28 -0700	[thread overview]
Message-ID: <20240130-s390-vdso-drop-fpic-from-ldflags-v1-1-094ad104fc55@kernel.org> (raw)

'-fPIC' as an option to the linker does not do what it seems like it
should. With ld.bfd, it is treated as '-f PIC', which does not make
sense based on the meaning of '-f':

  -f SHLIB, --auxiliary SHLIB Auxiliary filter for shared object symbol table

When building with ld.lld (currently under review in a GitHub pull
request), it just errors out because '-f' means nothing and neither does
'-fPIC':

  ld.lld: error: unknown argument '-fPIC'

'-fPIC' was blindly copied from CFLAGS when the vDSO stopped being
linked with '$(CC)', it should not be needed. Remove it to clear up the
build failure with ld.lld.

Fixes: 2b2a25845d53 ("s390/vdso: Use $(LD) instead of $(CC) to link vDSO")
Link: https://github.com/llvm/llvm-project/pull/75643
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
Hi all,

The LLVM folks are working on SystemZ support in ld.lld and this issue
came up from my initial testing. There are also some other issues that I
have come across in testing that I note in the GitHub pull request
linked above. If they seem like kernel issues, any expertise or help
would be greatly appreciated towards getting this working.

Cheers,
Nathan
---
 arch/s390/kernel/vdso32/Makefile | 2 +-
 arch/s390/kernel/vdso64/Makefile | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/s390/kernel/vdso32/Makefile b/arch/s390/kernel/vdso32/Makefile
index caec7db6f966..b12a274cbb47 100644
--- a/arch/s390/kernel/vdso32/Makefile
+++ b/arch/s390/kernel/vdso32/Makefile
@@ -22,7 +22,7 @@ KBUILD_CFLAGS_32 := $(filter-out -m64,$(KBUILD_CFLAGS))
 KBUILD_CFLAGS_32 := $(filter-out -mno-pic-data-is-text-relative,$(KBUILD_CFLAGS_32))
 KBUILD_CFLAGS_32 += -m31 -fPIC -shared -fno-common -fno-builtin
 
-LDFLAGS_vdso32.so.dbg += -fPIC -shared -soname=linux-vdso32.so.1 \
+LDFLAGS_vdso32.so.dbg += -shared -soname=linux-vdso32.so.1 \
 	--hash-style=both --build-id=sha1 -melf_s390 -T
 
 $(targets:%=$(obj)/%.dbg): KBUILD_CFLAGS = $(KBUILD_CFLAGS_32)
diff --git a/arch/s390/kernel/vdso64/Makefile b/arch/s390/kernel/vdso64/Makefile
index e3c9085f8fa7..caa4ebff8a19 100644
--- a/arch/s390/kernel/vdso64/Makefile
+++ b/arch/s390/kernel/vdso64/Makefile
@@ -26,7 +26,7 @@ KBUILD_AFLAGS_64 += -m64
 KBUILD_CFLAGS_64 := $(filter-out -m64,$(KBUILD_CFLAGS))
 KBUILD_CFLAGS_64 := $(filter-out -mno-pic-data-is-text-relative,$(KBUILD_CFLAGS_64))
 KBUILD_CFLAGS_64 += -m64 -fPIC -fno-common -fno-builtin
-ldflags-y := -fPIC -shared -soname=linux-vdso64.so.1 \
+ldflags-y := -shared -soname=linux-vdso64.so.1 \
 	     --hash-style=both --build-id=sha1 -T
 
 $(targets:%=$(obj)/%.dbg): KBUILD_CFLAGS = $(KBUILD_CFLAGS_64)

---
base-commit: 41bccc98fb7931d63d03f326a746ac4d429c1dd3
change-id: 20240130-s390-vdso-drop-fpic-from-ldflags-0338365b4bc5

Best regards,
-- 
Nathan Chancellor <nathan@kernel.org>

