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(Nokia - FI/Espoo)" Cc: "linux-kernel@vger.kernel.org" , "gregkh@linuxfoundation.org" , "sashal@kernel.org" , "tglx@linutronix.de" , "stable@vger.kernel.org" , "hpa@zytor.com" , "andi.kleen@intel.com" , "luto@kernel.org" , "joel@joelfernandes.org" , "astrachan@google.com" , "kernel-team@android.com" Subject: Re: [PATCH 4.14 09/69] x86: vdso: Use $LD instead of $CC to link Message-ID: <20190426124804.GA23970@archlinux-i9> References: <20190415183726.036654568@linuxfoundation.org> <20190415183728.632579553@linuxfoundation.org> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="d6Gm4EdcadzBjdND" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --d6Gm4EdcadzBjdND Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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. 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= --gcc-toolchain= 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 > > Signed-off-by: Thomas Gleixner > > Acked-by: Andy Lutomirski > > Cc: "H. Peter Anvin" > > Cc: Greg Kroah-Hartman > > Cc: kernel-team@android.com > > Cc: joel@joelfernandes.org > > Cc: Andi Kleen > > Link: > > https://lkml.kernel.org/r/20180803173931.117515-1-astrachan@google.com > > Signed-off-by: Nathan Chancellor > > Signed-off-by: Sasha Levin > > --- > > 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 $(filter %.lds,$^) $(filter %.o,$^) && \ > > 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 > > > > # > --d6Gm4EdcadzBjdND Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="0001-kbuild-simplify-ld-option-implementation.patch" From 030323b8729be25808a36281f385c0458d232f39 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Fri, 23 Feb 2018 13:56:53 +0900 Subject: [PATCH] kbuild: simplify ld-option implementation commit 0294e6f4a0006856e1f36b8cd8fa088d9e499e98 upstream. Currently, linker options are tested by the coordination of $(CC) and $(LD) because $(LD) needs some object to link. As commit 86a9df597cdd ("kbuild: fix linker feature test macros when cross compiling with Clang") addressed, we need to make sure $(CC) and $(LD) agree the underlying architecture of the passed object. This could be a bit complex when we combine tools from different groups. For example, we can use clang for $(CC), but we still need to rely on GCC toolchain for $(LD). So, I was searching for a way of standalone testing of linker options. A trick I found is to use '-v'; this not only prints the version string, but also tests if the given option is recognized. If a given option is supported, $ aarch64-linux-gnu-ld -v --fix-cortex-a53-843419 GNU ld (Linaro_Binutils-2017.11) 2.28.2.20170706 $ echo $? 0 If unsupported, $ aarch64-linux-gnu-ld -v --fix-cortex-a53-843419 GNU ld (crosstool-NG linaro-1.13.1-4.7-2013.04-20130415 - Linaro GCC 2013.04) 2.23.1 aarch64-linux-gnu-ld: unrecognized option '--fix-cortex-a53-843419' aarch64-linux-gnu-ld: use the --help option for usage information $ echo $? 1 Gold works likewise. $ aarch64-linux-gnu-ld.gold -v --fix-cortex-a53-843419 GNU gold (Linaro_Binutils-2017.11 2.28.2.20170706) 1.14 masahiro@pug:~/ref/linux$ echo $? 0 $ aarch64-linux-gnu-ld.gold -v --fix-cortex-a53-999999 GNU gold (Linaro_Binutils-2017.11 2.28.2.20170706) 1.14 aarch64-linux-gnu-ld.gold: --fix-cortex-a53-999999: unknown option aarch64-linux-gnu-ld.gold: use the --help option for usage information $ echo $? 1 LLD too. $ ld.lld -v --gc-sections LLD 7.0.0 (http://llvm.org/git/lld.git 4a0e4190e74cea19f8a8dc625ccaebdf8b5d1585) (compatible with GNU linkers) $ echo $? 0 $ ld.lld -v --fix-cortex-a53-843419 LLD 7.0.0 (http://llvm.org/git/lld.git 4a0e4190e74cea19f8a8dc625ccaebdf8b5d1585) (compatible with GNU linkers) $ echo $? 0 $ ld.lld -v --fix-cortex-a53-999999 ld.lld: error: unknown argument: --fix-cortex-a53-999999 LLD 7.0.0 (http://llvm.org/git/lld.git 4a0e4190e74cea19f8a8dc625ccaebdf8b5d1585) (compatible with GNU linkers) $ echo $? 1 Signed-off-by: Masahiro Yamada Tested-by: Nick Desaulniers [nc: try-run-cached was added later, just use try-run, which is the current mainline state] Signed-off-by: Nathan Chancellor --- scripts/Kbuild.include | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include index a0ad87e869f9..a33fa1a91873 100644 --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -165,9 +165,7 @@ cc-ldoption = $(call try-run,\ # ld-option # Usage: LDFLAGS += $(call ld-option, -X) -ld-option = $(call try-run,\ - $(CC) $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) -x c /dev/null -c -o "$$TMPO"; \ - $(LD) $(LDFLAGS) $(1) "$$TMPO" -o "$$TMP",$(1),$(2)) +ld-option = $(call try-run, $(LD) $(LDFLAGS) $(1) -v,$(1),$(2)) # ar-option # Usage: KBUILD_ARFLAGS := $(call ar-option,D) -- 2.21.0 --d6Gm4EdcadzBjdND--