[U-Boot] relocation problem on powerpc

[Chris Packham]

Hi Jocke

On Wed, Sep 10, 2014 at 1:20 AM, Joakim Tjernlund
<joakim.tjernlund at transmode.se> wrote:
> Joakim Tjernlund/Transmode wrote on 2014/09/09 14:30:13:
>
>> From: Joakim Tjernlund/Transmode
>> To:
>> Cc: Chris Packham <judge.packham at gmail.com>, u-boot
> <u-boot at lists.denx.de>
>> Date: 2014/09/09 14:30
>> Subject: Re: [U-Boot] relocation problem on powerpc
>>
>>
>> > > Here's some more info from a build without any of my modifications.
>> > >
>> > >   $ git describe
>> > >   v2014.10-rc2-12-g0b703db
>> > >
>> > >   $ powerpc-e500-linux-gnu-gcc --version
>> > >   powerpc-e500-linux-gnu-gcc (Gentoo 4.6.3-r1 p1.9, pie-0.5.2) 4.6.3
>> > >
>> > >   $ grep '_GOT2_TABLE_\|_GLOBAL_OFFSET_TABLE_\|__got2_entries'
> u-boot.map
>> > >   0x00000000effb5100                _GOT2_TABLE_ = .
>> > >   0x00000000effb7d38                _GLOBAL_OFFSET_TABLE_
>> > >   0x00000000effb7d48                PROVIDE (_GLOBAL_OFFSET_TABLE_,
> (. + 0x4))
>> > >   0x0000000000000b0d                __got2_entries =
>> > > (((_GLOBAL_OFFSET_TABLE_ - _GOT2_TABLE_) >> 0x2) - 0x1)
>> > >
>> > >   $ gdb-multiarch u-boot
>> > >   (gdb) disassemble /r 0xeffb5100,0xeffb7d48
>> > >   Dump of assembler code from 0xeffb5100 to 0xeffb7d48:
>> > >      0xeffb5100 <_GOT2_TABLE_+0>: ef fb 51 00     .long 0xeffb5100
>> > >      0xeffb5104 <_GOT2_TABLE_+4>: ef fb 7d 44     dtstsf cr7,f27,f15
>> > >      0xeffb5108 <_GOT2_TABLE_+8>: ef f4 00 00     .long 0xeff40000
>> > >      0xeffb510c <_GOT2_TABLE_+12>:        ef f4 01 00     .long
> 0xeff40100
>> > >     <snip>
>> > >      0xeffb7d30 <_GOT2_TABLE_+11312>:     ef f6 6e 74     .long
> 0xeff66e74
>> > >      0xeffb7d34 <_GOT2_TABLE_+11316>:     f0 00 00 d0     psq_st
> f0,208(r0),0,0
>> > >      0xeffb7d38 <_GLOBAL_OFFSET_TABLE_+0>:        00 00 00 00 .long
> 0x0
>> > >      0xeffb7d3c <_GLOBAL_OFFSET_TABLE_+4>:        00 00 00 00 .long
> 0x0
>> > >      0xeffb7d40 <_GLOBAL_OFFSET_TABLE_+8>:        00 00 00 00 .long
> 0x0
>> > >      0xeffb7d44 <_FIXUP_TABLE_+0>:        ef fb 99 d4     .long
> 0xeffb99d4
>> > >
>> > > So no there is no brlr at the end of the table.
>> >
>> > There should be, see
> http://www.freescale.com/files/32bit/doc/ref_manual/E500ABIUG.pdf, chap
> 4.3.2

Yep that's pretty unambiguous "The word at _GLOBAL_OFFSET_TABLE_[-1]
shall contain a blrl instruction". No "should", "may" or "can" in
sight.

>>
>> So I did a quick test too with my copy of u-boot:
>> (gdb) disass /r 0x00000000effa0a48,0x00000000effa0a68
>>    Dump of assembler code from 0xeffa0a48 to 0xeffa0a68:
>>    0xeffa0a48 <_GOT2_TABLE_+9800>: f0 00 00 dc .long 0xf00000dc
>>    0xeffa0a4c <_GOT2_TABLE_+9804>: ef f6 29 48 .long 0xeff62948
>>    0xeffa0a50 <_GOT2_TABLE_+9808>: f0 00 00 e0 .long 0xf00000e0
>>    0xeffa0a54 <_GOT2_TABLE_+9812>: 4e 80 00 21 blrl
>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>    0xeffa0a58 <_GLOBAL_OFFSET_TABLE_+0>: 00 00 00 00 .long 0x0
>>    0xeffa0a5c <_GLOBAL_OFFSET_TABLE_+4>: 00 00 00 00 .long 0x0
>>    0xeffa0a60 <_GLOBAL_OFFSET_TABLE_+8>: 00 00 00 00 .long 0x0
>>    0xeffa0a64 <_FIXUP_TABLE_+0>: ef fa 23 1c .long 0xeffa231c
>
>> $ powerpc-softfloat_4.5.3-linux-gnu-ld --version
>> GNU ld (GNU Binutils) 2.21.1
>>
>> I don't know it this is tool(ld) problem or if something in u-boot's
> build env. Try dropping
>> --gc-sections, see if that changes anything, or add --bss-plt or similar
>
> --bss-plt seems to be the answer:
> http://lists.denx.de/pipermail/u-boot/2014-February/173134.html
>
>   Jocke
>

Same question as that original thread '--bss-plt' or '-mbss-plt'? The
former works (I'll send a patch through) but I can only find
documentation for the latter.