[U-Boot] relocation problem on powerpc

[Chris Packham]

On Mon, Sep 8, 2014 at 9:04 PM, Joakim Tjernlund
<joakim.tjernlund at transmode.se> wrote:
>>
>> There are some disadvantages to living in a weird timezone, mostly
>> that you end up having conversations with yourself.
>>
>> On Mon, Sep 8, 2014 at 4:32 PM, Chris Packham <judge.packham at gmail.com>
> wrote:
>> > Hi All,
>> >
>> > I have come across what I think is a relocation problem for powerpc.
>> >
>> > I've added the following to ArpTimeoutCheck
>> >
>> > +       printf("NetArpWaitTimerStart = %ld\n", NetArpWaitTimerStart);
>> > +       printf("&NetArpWaitTimerStart = %p\n", &NetArpWaitTimerStart);
>> > +       printf("NetArpWaitTry = %d\n", NetArpWaitTry);
>> > +       printf("&NetArpWaitTry = %p\n", &NetArpWaitTry);
>> > +       printf("NetArpWaitTxPacketSize = %d\n",
> NetArpWaitTxPacketSize);
>> > +       printf("&NetArpWaitTxPacketSize = %p\n",
> &NetArpWaitTxPacketSize);
>> >
>> > Which yields the following output
>> >
>> >   NetArpWaitTimerStart = 0
>> >   &NetArpWaitTimerStart = f00000d0
>> >   NetArpWaitTry = 1
>> >   &NetArpWaitTry = 7ffb0058
>> >   NetArpWaitTxPacketSize = 42
>> >   &NetArpWaitTxPacketSize = 7ffb0078
>> >
>> > That looks to me like NetArpWaitTimerStart hasn't been relocated for
>> > some reason. Looking at my u-boot.map NetArpWaitTimerStart is the last
>> > item in the .sbss section
>> >
>> > Here's the relevant snippets for the variables I'm displaying
>> >
>> >  0x00000000f0000058                NetArpWaitTry
>> >  0x00000000f0000078                NetArpWaitTxPacketSize
>> >  0x00000000f00000d0                NetArpWaitTimerStart
>> >
>> > The actual problem for me is that ARPs timeout and various network
>> > things fail. Has anyone got any clues as to why this one particular
>> > variable isn't getting relocated.
>> >
>> > Thanks,
>> > Chris
>> >
>> > More info:
>> >   I'm building P2041RDB_config
>> >
>> >   $ git describe
>> >   v2014.10-rc2-15-g2ec8915
>> >
>> >   => version
>> >   U-Boot 2014.10-rc2-00015-g2ec8915-dirty (Sep 08 2014 - 16:18:42)
>> >   powerpc-e500-linux-gnu-gcc (Gentoo 4.6.3-r1 p1.9, pie-0.5.2) 4.6.3
>> >   GNU ld (GNU Binutils) 2.21
>>
>> I'm not confident enough to say it's a fix but the following seems to
>> solve the relocation problem for NetArpWaitTimerStart.
>>
>> diff --git a/arch/powerpc/cpu/mpc85xx/u-boot.lds
>> b/arch/powerpc/cpu/mpc85xx/u-boot.lds
>> index 2cf0b25..36711b0 100644
>> --- a/arch/powerpc/cpu/mpc85xx/u-boot.lds
>> +++ b/arch/powerpc/cpu/mpc85xx/u-boot.lds
>> @@ -54,7 +54,7 @@ SECTIONS
>>      _FIXUP_TABLE_ = .;
>>      KEEP(*(.fixup))
>>    }
>> -  __got2_entries = ((_GLOBAL_OFFSET_TABLE_ - _GOT2_TABLE_) >> 2) - 1;
>> +  __got2_entries = ((_GLOBAL_OFFSET_TABLE_ - _GOT2_TABLE_) >> 2);
>>    __fixup_entries = (. - _FIXUP_TABLE_) >> 2;
>
> This looks like the correct fix, The relevant code that uses
> __got2_entries is in start.S:

I can turn this into a proper patch. As you say below all powerpc
implementations have this -1. I can test MPC85xx but I don't have
access to any of the others. Also by "test" all I can really do is
printf("%p\n", &NetArpWaitTimerStart); is there something better I
should be doing?

>
> in_ram:
>
>         /*
>          * Relocation Function, r12 point to got2+0x8000
>          *
>          * Adjust got2 pointers, no need to check for 0, this code
>          * already puts a few entries in the table.
>          */
>         li      r0,__got2_entries at sectoff@l
>         la      r3,GOT(_GOT2_TABLE_)
>         lwz     r11,GOT(_GOT2_TABLE_)
>         mtctr   r0
>         sub     r11,r3,r11
>         addi    r3,r3,-4
> 1:      lwzu    r0,4(r3)
>         cmpwi   r0,0
>         beq-    2f
>         add     r0,r0,r11
>         stw     r0,0(r3)
> 2:      bdnz    1b
>
> bdnz does decrement then test for zero so __got2_entries should hold the
> number of entries to relocate.
>
> Seems like most(all?) ppc cpu has this error.
>
>  Jocke

I had actually seen this kind of error before with some usb
routines[1]. Again the symbol happened to be something that was at the
end of .sbss. In this particular case something else changed and the
problem went away so I didn't pursue it but I think this problem may
have been around for a while probably since 337f5f50 (PowerPC: Add
relocation support for -fpic).

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[1] - http://lists.denx.de/pipermail/u-boot/2013-June/156435.html