Messages in this thread | | | From | Arvind Sankar <> | Date | Sat, 11 Jan 2020 12:20:48 -0500 | Subject | Re: [PATCH] x86/tools/relocs: Add _etext and __end_of_kernel_reserve to S_REL |
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On Sat, Jan 11, 2020 at 02:02:43PM +0100, Borislav Petkov wrote: > On Fri, Jan 10, 2020 at 03:50:29PM -0500, Arvind Sankar wrote: > > On Fri, Jan 10, 2020 at 09:38:28PM +0100, Borislav Petkov wrote: > > > On Fri, Jan 10, 2020 at 03:23:49PM -0500, Arvind Sankar wrote: > > > > Pre-2.23 binutils makes symbols defined outside sections absolute, so > > > > these two symbols break the build on old linkers. > > > > > > -ENOTENOUGHINFO > > > > > > Which old linkers, how exactly do they break the build, etc etc? > > > > > > Please give exact reproduction steps. > > > > > > Thx. > > > > > > > binutils-2.21 and -2.22. An x86-64 defconfig will fail with > > Invalid absolute R_X86_64_32S relocation: _etext > > and after fixing that one, with > > Invalid absolute R_X86_64_32S relocation: __end_of_kernel_reserve > > I'm still not clear as to why this happens. I tried reproducing on > openSUSE 12.1 which has > > Repository: openSUSE-12.1-Oss > Name: binutils > Version: 2.21.1-12.1.4 > > and the build there fails with: > > objdump: arch/x86/lib/clear_page_64.o: File format not recognized > objdump: arch/x86/lib/cmdline.o: File format not recognized > objdump: arch/x86/lib/cmpxchg16b_emu.o: File format not recognized > objdump: arch/x86/lib/copy_page_64.o: File format not recognized > objdump: arch/x86/lib/copy_user_64.o: File format not recognized > objdump: arch/x86/lib/cpu.o: File format not recognized > ... > > and objdump is part of binutils. > > Now, this looks like another symptom of what you're reporting but what > we're missing is the rootcause about *why* this happens. > > Because if the issue is hard to fix or similar, then we probably should > raise the minimum supported binutils version from 2.21 to something > newer and not do this fix. > > But before we do that, we need a proper analysis as to why it happens. > > Also, what distro are you using to reproduce it on? > > Thx. >
I'm not sure if that's the same issue. The root cause for the one I reported is described in more detail in [1], and the change that makes these symbols no longer absolute is commit d2667025dd30 in binutils-gdb (sourceware.org seems to be taking too long to respond from here so I don't have the web link).
I'm running gentoo, but building the kernel using binutils-2.21.1 compiled from the GNU source tarball, and gcc-4.6.4 again compiled from source. (It's not something I normally need but I was investigating something else to see what exactly happens with older toolchains.)
I used the below to compile the kernel (I added in readelf/objdump/objcopy just now, and it does build until the relocs error). The config is x86-64 defconfig with CONFIG_RETPOLINE overridden to n (since gcc 4.6.4 doesn't support retpoline).
make O=~/kernel64 -j LD=~/old/bin/ld AS=~/old/bin/as READELF=~/old/bin/readelf \ OBJDUMP=~/old/bin/objdump OBJCOPY=~/old/bin/objcopy GCC=~/old/bin/gcc
[1] https://lore.kernel.org/lkml/20200110215005.2164353-1-nivedita@alum.mit.edu/
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