[U-Boot] [u-boot-mips] gp init and -pie option

[Juhyun (Justin) Oh]

HI Daniel,

I'm using CodeSourcery 4.5.2. I've configured and have built the code for "incaip" board and "dbau1000". The results are the same. (i.e. gp has been set with wrong value)

Could you tell me the CodeSourcery toolchain versions known to be working? I'd like to try out the same version.

Thanks,
Justin

________________________________________
From: Daniel Schwierzeck [daniel.schwierzeck at gmail.com]
Sent: Tuesday, February 26, 2013 1:52 AM
To: Juhyun (Justin) Oh
Cc: u-boot at lists.denx.de
Subject: Re: [U-Boot] [u-boot-mips] gp init and -pie option

2013/2/25 Juhyun (Justin) Oh <Juhyun_Oh at sigmadesigns.com>:
> Hi,
>
> I got a problem while I was trying out v2013.01.01 on the u-boot-mips fork repo. It looks like my u-boot binary built with "-pie" linker option doesn't work due to wrong "gp" initialization.
>
> In the "start.S" file, the gp is supposed to be initialized with "_gp" because ra will hold the address of ".word _gp" line. The below is part of "start.S".
>
> ----------------------------
> ...
>     /* Initialize $gp */
>     bal 1f
>      nop
>     .word   _gp
> 1:
>     lw  gp, 0(ra)
> ...
> ----------------------------
>
> Without the -pie option, linker puts the start address of the .got section. However, with -pie option, the ".word _gp" is translated to "nop". The below is disassembled code.
>
> ----------------------------------------------------------------------------
> 84001490 <reset>:
> ...
> 840014b8:   40804800    mtc0    zero,c0_count
> 840014bc:   40805800    mtc0    zero,c0_compare
> 840014c0:   04110002    bal 840014cc <reset+0x3c>
> 840014c4:   00000000    nop
> 840014c8:   00000000    nop <---------------
> 840014cc:   8ffc0000    lw  gp,0(ra)
> 840014d0:   3c1d8440    lui sp,0x8440
> 840014d4:   8f9982c0    lw  t9,-32064(gp)
> 840014d8:   03200008    jr  t9
> 840014dc:   00000000    nop
> ----------------------------------------------------------------------------
>
> Could anyone tell me what is going on here? Am I missing anything?
>
> Thanks,
> Justin

which board and toolchain do you use?

PIE support has been tested with various toolchains from ELDK,
CodeSourcery and OpenWRT.

--
Best regards,
Daniel