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

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

[Juhyun Oh]

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

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

[Daniel Schwierzeck]

2013/2/25 Juhyun (Justin) Oh <Juhyun_Oh@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

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

[Juhyun 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@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

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

[Michael Cashwell]

Not to hijack this thread, but I've had trouble with recent (2013.01 and perhaps the last 2012) mainline u-boots for Pandaboard when built using recent Codesourcery Lite tools. I've found that arm-2009q1 and arm-2010q1 work but arm-2012.03 and arm-2012.09 do not. SPL works but u-boot hangs very early.

It's on my list of things to look into.

-Michael Cashwell

On Feb 26, 2013, at 1:12 PM, "Juhyun (Justin) Oh" <Juhyun_Oh@sigmadesigns.com> wrote:

> 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@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
> _______________________________________________
> U-Boot mailing list
> U-Boot at lists.denx.de
> http://lists.denx.de/mailman/listinfo/u-boot

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

[Juhyun Oh]

Hi Michael,

I'm not working on ARM, but on MIPS. Your problem is certainly different from mine. 


Hi Daniel,

I've tried out "gcc version 4.6.3 (Sourcery CodeBench Lite 2012.03-63)", and this version initialize gp register properly. 

Thanks,
Justin

________________________________________
From: Michael Cashwell [mboards at prograde.net]
Sent: Tuesday, February 26, 2013 11:44 AM
To: Juhyun (Justin) Oh
Cc: Daniel Schwierzeck; u-boot at lists.denx.de
Subject: Re: [U-Boot] [u-boot-mips] gp init and -pie option

Not to hijack this thread, but I've had trouble with recent (2013.01 and perhaps the last 2012) mainline u-boots for Pandaboard when built using recent Codesourcery Lite tools. I've found that arm-2009q1 and arm-2010q1 work but arm-2012.03 and arm-2012.09 do not. SPL works but u-boot hangs very early.

It's on my list of things to look into.

-Michael Cashwell

On Feb 26, 2013, at 1:12 PM, "Juhyun (Justin) Oh" <Juhyun_Oh@sigmadesigns.com> wrote:

> 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@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
> _______________________________________________
> U-Boot mailing list
> U-Boot at lists.denx.de
> http://lists.denx.de/mailman/listinfo/u-boot

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

[Daniel Schwierzeck]

Hi,

2013/2/26 Juhyun (Justin) Oh <Juhyun_Oh@sigmadesigns.com>:
> 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.
>
Which CodeSourcery release do you use?

I have tried following toolchains and all of them have _gp initialized
correctly.

Sourcery CodeBench Lite 2011.09-75
  gcc version 4.5.2 (Sourcery CodeBench Lite 2011.09-75)
  GNU ld (Sourcery CodeBench Lite 2011.09-75) 2.21.53.20110905

Sourcery CodeBench Lite 2012.03-63:
  gcc version 4.6.3 (Sourcery CodeBench Lite 2012.03-63)
  GNU ld (Sourcery CodeBench Lite 2012.03-63) 2.21.53.20110905

ELDK-5.2.1:
  gcc version 4.6.4 20120303 (prerelease) (GCC)
  GNU ld (GNU Binutils) 2.22

ELDK-5.3:
  gcc version 4.7.2 (GCC)
  GNU ld (GNU Binutils) 2.22

-- 
Best regards,
Daniel

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

[Juhyun Oh]

Hi Daniel,

I've verified that the CodeSourcery 4.5.2 and 4.6.3  generate the correct _gp as you mentioned.

Thanks,
Justin

________________________________________
From: Daniel Schwierzeck [daniel.schwierzeck at gmail.com]
Sent: Tuesday, February 26, 2013 12:34 PM
To: Juhyun (Justin) Oh
Cc: u-boot at lists.denx.de
Subject: Re: [U-Boot] [u-boot-mips] gp init and -pie option

Hi,

2013/2/26 Juhyun (Justin) Oh <Juhyun_Oh@sigmadesigns.com>:
> 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.
>
Which CodeSourcery release do you use?

I have tried following toolchains and all of them have _gp initialized
correctly.

Sourcery CodeBench Lite 2011.09-75
  gcc version 4.5.2 (Sourcery CodeBench Lite 2011.09-75)
  GNU ld (Sourcery CodeBench Lite 2011.09-75) 2.21.53.20110905

Sourcery CodeBench Lite 2012.03-63:
  gcc version 4.6.3 (Sourcery CodeBench Lite 2012.03-63)
  GNU ld (Sourcery CodeBench Lite 2012.03-63) 2.21.53.20110905

ELDK-5.2.1:
  gcc version 4.6.4 20120303 (prerelease) (GCC)
  GNU ld (GNU Binutils) 2.22

ELDK-5.3:
  gcc version 4.7.2 (GCC)
  GNU ld (GNU Binutils) 2.22

--
Best regards,
Daniel

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

[Jason Harris]

Daniel Schwierzeck <daniel.schwierzeck <at> gmail.com> writes:

> 
> Hi,
> 
> 2013/2/26 Juhyun (Justin) Oh <Juhyun_Oh <at> sigmadesigns.com>:
> > 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.
> >
> Which CodeSourcery release do you use?
> 
> I have tried following toolchains and all of them have _gp initialized
> correctly.
> 
> Sourcery CodeBench Lite 2011.09-75
>   gcc version 4.5.2 (Sourcery CodeBench Lite 2011.09-75)
>   GNU ld (Sourcery CodeBench Lite 2011.09-75) 2.21.53.20110905
> 
> Sourcery CodeBench Lite 2012.03-63:
>   gcc version 4.6.3 (Sourcery CodeBench Lite 2012.03-63)
>   GNU ld (Sourcery CodeBench Lite 2012.03-63) 2.21.53.20110905
> 
> ELDK-5.2.1:
>   gcc version 4.6.4 20120303 (prerelease) (GCC)
>   GNU ld (GNU Binutils) 2.22
> 
> ELDK-5.3:
>   gcc version 4.7.2 (GCC)
>   GNU ld (GNU Binutils) 2.22
> 


mips-u24kc-linux-gnu-ld --version
GNU ld (GNU Binutils) 2.18

--help ....

  -pie, --pic-executable      Create a position independent executable

I've observed:

with -pie:

800004c0 04110002: bgezal  r0, 0x2L (=2) -> 0x00000000800004cc
800004c4 00000000: nop
800004c8 00000000: nop
800004cc 8ffc0000: lw      r28, 0x0L (=0) (r31)

wrong: _gp = 0

with --pic-executable:

800004c0 04110002: bgezal  r0, 0x2L (=2) -> 0x00000000800004cc
800004c4 00000000: nop
800004c8 800372c0: lb      r3, 0x72c0L (=29376) (r0)
800004cc 8ffc0000: lw      r28, 0x0L (=0) (r31)

correct: _gp = 800372c0

Looks like something is wrong with option processing on ld.

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

[Jason Harris]

Jason Harris <jason.harris <at> motorolasolutions.com> writes:

> 
> Looks like something is wrong with option processing on ld.
> 


I take it back:

The patch from http://sourceware.org/bugzilla/show_bug.cgi?id=10858
fixes it.

Jason H.