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Mon, 22 Jun 2020 15:52:40 -0700 (PDT) Date: Mon, 22 Jun 2020 15:52:37 -0700 From: Fangrui Song To: Kees Cook Cc: Borislav Petkov , Thomas Gleixner , Ingo Molnar , x86@kernel.org, Arnd Bergmann , Nick Desaulniers , Nathan Chancellor , clang-built-linux@googlegroups.com, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/3] vmlinux.lds.h: Add .gnu.version* to DISCARDS Message-ID: <20200622225237.ybol4qmz4mhkmlqc@google.com> References: <20200622205341.2987797-1-keescook@chromium.org> <20200622205341.2987797-2-keescook@chromium.org> <20200622220043.6j3vl6v7udmk2ppp@google.com> <202006221524.CEB86E036B@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <202006221524.CEB86E036B@keescook> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-06-22, Kees Cook wrote: >On Mon, Jun 22, 2020 at 03:00:43PM -0700, Fangrui Song wrote: >> On 2020-06-22, Kees Cook wrote: >> > For vmlinux linking, no architecture uses the .gnu.version* section, >> > so remove it via the common DISCARDS macro in preparation for adding >> > --orphan-handling=warn more widely. >> > >> > Signed-off-by: Kees Cook >> > --- >> > include/asm-generic/vmlinux.lds.h | 1 + >> > 1 file changed, 1 insertion(+) >> > >> > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h >> > index db600ef218d7..6fbe9ed10cdb 100644 >> > --- a/include/asm-generic/vmlinux.lds.h >> > +++ b/include/asm-generic/vmlinux.lds.h >> > @@ -934,6 +934,7 @@ >> > *(.discard) \ >> > *(.discard.*) \ >> > *(.modinfo) \ >> > + *(.gnu.version*) \ >> > } >> > >> > /** >> > -- >> > 2.25.1 >> >> I wonder what lead to .gnu.version{,_d,_r} sections in the kernel. > >This looks like a bug in bfd.ld? There are no versioned symbols in any >of the input files (and no output section either!) > >The link command is: >$ ld -m elf_x86_64 --no-ld-generated-unwind-info -z noreloc-overflow -pie \ >--no-dynamic-linker --orphan-handling=warn -T \ >arch/x86/boot/compressed/vmlinux.lds \ >arch/x86/boot/compressed/kernel_info.o \ >arch/x86/boot/compressed/head_64.o arch/x86/boot/compressed/misc.o \ >arch/x86/boot/compressed/string.o arch/x86/boot/compressed/cmdline.o \ >arch/x86/boot/compressed/error.o arch/x86/boot/compressed/piggy.o \ >arch/x86/boot/compressed/cpuflags.o \ >arch/x86/boot/compressed/early_serial_console.o \ >arch/x86/boot/compressed/kaslr.o arch/x86/boot/compressed/kaslr_64.o \ >arch/x86/boot/compressed/mem_encrypt.o \ >arch/x86/boot/compressed/pgtable_64.o arch/x86/boot/compressed/acpi.o \ >-o arch/x86/boot/compressed/vmlinux > >None of the inputs have the section: > >$ for i in arch/x86/boot/compressed/kernel_info.o \ >arch/x86/boot/compressed/head_64.o arch/x86/boot/compressed/misc.o \ >arch/x86/boot/compressed/string.o arch/x86/boot/compressed/cmdline.o \ >arch/x86/boot/compressed/error.o arch/x86/boot/compressed/piggy.o \ >arch/x86/boot/compressed/cpuflags.o \ >arch/x86/boot/compressed/early_serial_console.o \ >arch/x86/boot/compressed/kaslr.o arch/x86/boot/compressed/kaslr_64.o \ >arch/x86/boot/compressed/mem_encrypt.o \ >arch/x86/boot/compressed/pgtable_64.o arch/x86/boot/compressed/acpi.o \ >; do echo -n $i": "; readelf -Vs $i | grep 'version'; done >arch/x86/boot/compressed/kernel_info.o: No version information found in this file. >arch/x86/boot/compressed/head_64.o: No version information found in this file. >arch/x86/boot/compressed/misc.o: No version information found in this file. >arch/x86/boot/compressed/string.o: No version information found in this file. >arch/x86/boot/compressed/cmdline.o: No version information found in this file. >arch/x86/boot/compressed/error.o: No version information found in this file. >arch/x86/boot/compressed/piggy.o: No version information found in this file. >arch/x86/boot/compressed/cpuflags.o: No version information found in this file. >arch/x86/boot/compressed/early_serial_console.o: No version information found in this file. >arch/x86/boot/compressed/kaslr.o: No version information found in this file. >arch/x86/boot/compressed/kaslr_64.o: No version information found in this file. >arch/x86/boot/compressed/mem_encrypt.o: No version information found in this file. >arch/x86/boot/compressed/pgtable_64.o: No version information found in this file. >arch/x86/boot/compressed/acpi.o: No version information found in this file. > >And it's not in the output: > >$ readelf -Vs arch/x86/boot/compressed/vmlinux | grep version >No version information found in this file. > >So... for the kernel we need to silence it right now. Re-link with -M (or -Map file) to check where .gnu.version{,_d,_r} input sections come from? If it is a bug, we should probably figure out which version of binutils has fixed the bug.