Messages in this thread Patch in this message | | | Date | Wed, 18 Jul 2018 15:41:59 -0700 | Subject | [PATCH] x86: vdso: Use $LD instead of $CC to link | From | Alistair Strachan <> |
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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.
Cc: Andy Lutomirski <luto@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: x86@kernel.org Cc: kernel-team@android.com Cc: joel@joelfernandes.com Signed-off-by: Alistair Strachan <astrachan@google.com> --- Supersedes "x86: vdso: Fix leaky vdso link with CC=clang" 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 1943aebadede..896a55204386 100644 --- a/arch/x86/entry/vdso/Makefile +++ b/arch/x86/entry/vdso/Makefile @@ -48,10 +48,8 @@ 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) @@ -97,10 +95,8 @@ 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)) @@ -128,7 +124,7 @@ $(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 targets += vdso32/vdso32.lds targets += vdso32/note.o vdso32/system_call.o vdso32/sigreturn.o @@ -162,13 +158,13 @@ $(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 #
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