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    SubjectRe: [PATCH] x86/tools/relocs: Add _etext and __end_of_kernel_reserve to S_REL
    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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