Messages in this thread | | | From | Andy Lutomirski <> | Date | Sat, 21 Jul 2018 16:28:55 -0700 | Subject | Re: [PATCH] x86: vdso: Use $LD instead of $CC to link |
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On Wed, Jul 18, 2018 at 3:41 PM, Alistair Strachan <astrachan@google.com> wrote: > 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.
Acked-by: Andy Lutomirski <luto@kernel.org>
> > 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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