On Fri, 2019-04-26 at 05:48 -0700, Nathan Chancellor wrote:
On Fri, Apr 26, 2019 at 11:41:30AM +0000, Rantala, Tommi T. (Nokia - FI/Espoo) wrote:
On Mon, 2019-04-15 at 20:58 +0200, Greg Kroah-Hartman wrote:
commit 379d98ddf41344273d9718556f761420f4dc80b3 upstream.
Hi,
With this patch in 4.14.112 build-id is now missing in vdso32.so:
$ file arch/x86/entry/vdso/vdso*so* arch/x86/entry/vdso/vdso32.so: ELF 32-bit LSB pie executable, Intel 80386, version 1 (SYSV), dynamically linked, stripped arch/x86/entry/vdso/vdso32.so.dbg: ELF 32-bit LSB pie executable, Intel 80386, version 1 (SYSV), dynamically linked, with debug_info, not stripped arch/x86/entry/vdso/vdso64.so: ELF 64-bit LSB pie executable, x86- 64, version 1 (SYSV), dynamically linked, BuildID[sha1]=d80730a5b561a3161e488a369d1c76c250b584b4, stripped arch/x86/entry/vdso/vdso64.so.dbg: ELF 64-bit LSB pie executable, x86- 64, version 1 (SYSV), dynamically linked, BuildID[sha1]=d80730a5b561a3161e488a369d1c76c250b584b4, with debug_info, not stripped
Based on quick check, "$(call ld-option, --build-id)" fails due to some 32/64 bit mismatch, so the --build-id linker flag is not used when linking vdso32.so
Perhaps scripts/Kbuild.include is missing some change in 4.14.y to make this work properly.
Hi Tommi,
This appears to be fixed by commit 0294e6f4a000 ("kbuild: simplify ld-option implementation") upstream. Could you test the attached backport and make sure everything works on your end? Assuming that it does, I will test the other stable releases and see if this is needed and send those backports along.
Yes this patch fixes it. Many thanks!
-Tommi
Thanks and sorry for the trouble! Nathan
-Tommi
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 0a550dc5c525..0defcc939ab4 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) @@ -103,10 +101,8 @@ 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)) @@ -134,7 +130,7 @@ $(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. @@ -180,13 +176,13 @@ $(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 $(filter %.lds,$^) $(filter %.o,$^) && \-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 #