ftrace/MIPS related x86_64 build failure on in Linus' tree

[Stephen Rothwell <sfr@canb.auug.org.au>]

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Hi all,

Since October 31 our x86_64 allmodconfig builds have been failing like this:

/opt/crosstool/gcc-4.4.3-nolibc/x86_64-linux/bin/x86_64-linux-ld: arch/x86/ia32/sys_ia32.o: bad reloc symbol index (0x1000000 >= 0x6b) for offset 0x808080 in section `__mcount_loc'
arch/x86/ia32/sys_ia32.o: could not read symbols: Bad value

and many similar
(http://fandango2.ozlabs.ibm.com/kisskb/buildresult/3423985/).  I finally
got around to bisecting it and it comes down to this commit:

a2d49358ba9bc93204dc001d5568c5bdb299b77d is the first bad commit
commit a2d49358ba9bc93204dc001d5568c5bdb299b77d
Author: John Reiser <jreiser@BitWagon.com>
Date:   Wed Oct 27 18:59:07 2010 +0800

    ftrace/MIPS: Add MIPS64 support for C version of recordmcount
    
    MIPS64 has 'weird' Elf64_Rel.r_info[1,2], which must be used instead of
    the generic Elf64_Rel.r_info, otherwise, the C version of recordmcount
    will not work for "segmentation fault".
    
    Usage of "union mips_r_info" and the functions MIPS64_r_sym() and
    MIPS64_r_info() written by Maciej W. Rozycki <macro@linux-mips.org>
    
    ----
    [1] http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
    [2] arch/mips/include/asm/module.h
    
    Tested-by: Wu Zhangjin <wuzhangjin@gmail.com>
    Signed-off-by: John Reiser <jreiser@BitWagon.com>
    Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
    LKML-Reference: <AANLkTinwXjLAYACUfhLYaocHD_vBbiErLN3NjwN8JqSy@mail.gmail.com>
    LKML-Reference: <910dc2d5ae1ed042df4f96815fe4a433078d1c2a.1288176026.git.wuzhangjin@gmail.com>
    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
    Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

:040000 040000 c208c976b8bd3eb28791d0e96dcb24967586fbb0 28da1214674ed267e0c4aa249379504bc8b20216 M	scripts

This seems to be tool chain specific.  We are using a PowerPC hosted
x86_64 cross compiler:

x86_64-linux-gcc (GCC) 4.4.3
GNU ld (GNU Binutils) 2.20

[It does *not* fail for our x86_64 hosted x86_64 compiler:

x86_64-linux-gcc (GCC) 4.4.4
GNU ld (GNU Binutils) 2.20
]

I tried reverting that commit (and the next commit
412910cd046c1f14f0fba9c0aec401d47e57dcd1 "ftrace/MIPS: Add module support
for C version of recordmcount" because of conflicts) and the build of
Linus' current tree now succeeds with the above toolchain,

-- 
Cheers,
Stephen Rothwell                    sfr@canb.auug.org.au
http://www.canb.auug.org.au/~sfr/

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