The vdso{32,64}.so can fail to link with CC=clang when clang tries to find a suitable GCC toolchain to link these libraries with.
/usr/bin/ld: arch/x86/entry/vdso/vclock_gettime.o: access beyond end of merged section (782)
This happens because the host environment leaked into the cross compiler environment due to the way clang searches for suitable GCC toolchains.
Clang is a retargetable compiler, and each invocation of it must provide --target=<something> --gcc-toolchain=<something> to allow it to find the correct binutils for cross compilation. These flags had been added to KBUILD_CFLAGS, but the vdso code uses CC and not KBUILD_CFLAGS (for various reasons) which breaks clang's ability to find the correct linker when cross compiling.
Most of the time this goes unnoticed because the host linker is new enough to work anyway, or is incompatible and skipped, but this cannot be reliably assumed.
This change alters the vdso makefile to just use LD directly, which bypasses clang and thus the searching problem. The makefile will just use ${CROSS_COMPILE}ld instead, which is always what we want. This matches the method used to link vmlinux.
This drops references to DISABLE_LTO; this option doesn't seem to be set anywhere, and not knowing what its possible values are, it's not clear how to convert it from CC to LD flag.
Signed-off-by: Alistair Strachan astrachan@google.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Acked-by: Andy Lutomirski luto@kernel.org Cc: "H. Peter Anvin" hpa@zytor.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: kernel-team@android.com Cc: joel@joelfernandes.org Cc: Andi Kleen andi.kleen@intel.com Link: https://lkml.kernel.org/r/20180803173931.117515-1-astrachan@google.com Signed-off-by: Nathan Chancellor natechancellor@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/entry/vdso/Makefile | 22 +++++++++------------- 1 file changed, 9 insertions(+), 13 deletions(-)
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile index d5409660f5de..2ae92c6b1de6 100644 --- a/arch/x86/entry/vdso/Makefile +++ b/arch/x86/entry/vdso/Makefile @@ -47,10 +47,8 @@ targets += $(vdso_img_sodbg)
export CPPFLAGS_vdso.lds += -P -C
-VDSO_LDFLAGS_vdso.lds = -m64 -Wl,-soname=linux-vdso.so.1 \ - -Wl,--no-undefined \ - -Wl,-z,max-page-size=4096 -Wl,-z,common-page-size=4096 \ - $(DISABLE_LTO) +VDSO_LDFLAGS_vdso.lds = -m elf_x86_64 -soname linux-vdso.so.1 --no-undefined \ + -z max-page-size=4096 -z common-page-size=4096
$(obj)/vdso64.so.dbg: $(src)/vdso.lds $(vobjs) FORCE $(call if_changed,vdso) @@ -96,10 +94,8 @@ CFLAGS_REMOVE_vvar.o = -pg #
CPPFLAGS_vdsox32.lds = $(CPPFLAGS_vdso.lds) -VDSO_LDFLAGS_vdsox32.lds = -Wl,-m,elf32_x86_64 \ - -Wl,-soname=linux-vdso.so.1 \ - -Wl,-z,max-page-size=4096 \ - -Wl,-z,common-page-size=4096 +VDSO_LDFLAGS_vdsox32.lds = -m elf32_x86_64 -soname linux-vdso.so.1 \ + -z max-page-size=4096 -z common-page-size=4096
# 64-bit objects to re-brand as x32 vobjs64-for-x32 := $(filter-out $(vobjs-nox32),$(vobjs-y)) @@ -127,7 +123,7 @@ $(obj)/vdsox32.so.dbg: $(src)/vdsox32.lds $(vobjx32s) FORCE $(call if_changed,vdso)
CPPFLAGS_vdso32.lds = $(CPPFLAGS_vdso.lds) -VDSO_LDFLAGS_vdso32.lds = -m32 -Wl,-m,elf_i386 -Wl,-soname=linux-gate.so.1 +VDSO_LDFLAGS_vdso32.lds = -m elf_i386 -soname linux-gate.so.1
# This makes sure the $(obj) subdirectory exists even though vdso32/ # is not a kbuild sub-make subdirectory. @@ -165,13 +161,13 @@ $(obj)/vdso32.so.dbg: FORCE \ # The DSO images are built using a special linker script. # quiet_cmd_vdso = VDSO $@ - cmd_vdso = $(CC) -nostdlib -o $@ \ + cmd_vdso = $(LD) -nostdlib -o $@ \ $(VDSO_LDFLAGS) $(VDSO_LDFLAGS_$(filter %.lds,$(^F))) \ - -Wl,-T,$(filter %.lds,$^) $(filter %.o,$^) && \ + -T $(filter %.lds,$^) $(filter %.o,$^) && \ sh $(srctree)/$(src)/checkundef.sh '$(NM)' '$@'
-VDSO_LDFLAGS = -fPIC -shared $(call cc-ldoption, -Wl$(comma)--hash-style=both) \ - $(call cc-ldoption, -Wl$(comma)--build-id) -Wl,-Bsymbolic $(LTO_CFLAGS) +VDSO_LDFLAGS = -shared $(call ld-option, --hash-style=both) \ + $(call ld-option, --build-id) -Bsymbolic GCOV_PROFILE := n
#