[U-Boot] [PATCH] ARM: Add .data/.rodata/.bss section starts to gd_t

[Peter Barada]

On 03/01/2012 09:22 AM, Albert ARIBAUD wrote:
> Hi Peter,
>
> Le 29/02/2012 17:42, Peter Barada a écrit :
>> On 02/28/2012 05:04 PM, Albert ARIBAUD wrote:
>>> Hi Peter,
>>>
>>> Le 27/02/2012 23:00, Peter Barada a écrit :
>>>> When debugging u-boot, after relocation its tedious to calculate positions
>>>> of the various sections (.data, .rodata, .bss).  To make it easier, add
>>>> the structure "sections" to gd_t that contains the relocated start of
>>>> those sections.  Then the gdb command "add-symbol-file" can by used with
>>>> "-s<section>   <address>" that corresponds to the values in gd_t->sections.
>>> NAK until I get an explanation and usage scenario for this, because I've
>>> never had to do calculations on sections so far, so I want to understand
>>> why it would be needed.
>>>
>>> Amicalement,
>> Weird.  Digging further its looking more like a problem with GDB...
>>
>> I'm using the CodeSourcery 2009q1-203 toolchain (for ARM), and
>> "add-symbol-file u-boot 0x...." only relocated symbols in the .text
>> segment, not .data, .rodata, and .bss sections.  Looking at newer
>> toolchains (CodeSourcery 2011.09-70) I see even stranger results:
>>
>> Current directory is /home/peter/work/logic/git/u-boot-branches/
>> GNU gdb (Sourcery CodeBench Lite 2011.09-70) 7.2.50.20100908-cvs
>> Copyright (C) 2010 Free Software Foundation, Inc.
>> License GPLv3+: GNU GPL version 3 or later
>> <http://gnu.org/licenses/gpl.html>
>> This is free software: you are free to change and redistribute it.
>> There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
>> and "show warranty" for details.
>> This GDB was configured as "--host=i686-pc-linux-gnu
>> --target=arm-none-linux-gnueabi".
>> For bug reporting instructions, please see:
>> <https://support.codesourcery.com/GNUToolchain/>...
>> Reading symbols from
>> /home/peter/work/logic/git/u-boot-branches/u-boot...done.
>> (gdb) info file
>> Symbols from "/home/peter/work/logic/git/u-boot-branches/u-boot".
>> Local exec file:
>>      `/home/peter/work/logic/git/u-boot-branches/u-boot', file type
>> elf32-littlearm.
>>      Entry point: 0x80100000
>>      0x80100000 - 0x80124a30 is .text
>>      0x80124a30 - 0x8012d43a is .rodata
>>      0x8012d43c - 0x8012d488 is .hash
>>      0x8012d488 - 0x8012dee0 is .data
>>      0x8012dee0 - 0x8012deec is .got.plt
>>      0x8012deec - 0x8012e544 is .u_boot_cmd
>>      0x8013354c - 0x8013362c is .dynsym
>>      0x8012e544 - 0x8013354c is .rel.dyn
>>      0x8012e544 - 0x80165388 is .bss
>> (gdb)(gdb) symbol-file
>> Discard symbol table from
>> `/home/peter/work/logic/git/u-boot-branches/u-boot'? (y or n) y
>> No symbol file now.
>> (gdb) *add-symbol-file u-boot 0x8ff8a000 -readnow -s .rodata 0x8FFAEA30
>> -s .data 0x8FFB7488 -s .bss 0x8FFB8544*
>> add symbol table from file "u-boot" at
>>      .text_addr = 0x8ff8a000
>>      .rodata_addr = 0x8ffaea30
>>      .data_addr = 0x8ffb7488
>>      .bss_addr = 0x8ffb8544
>> (y or n) y
>> Reading symbols from
>> /home/peter/work/logic/git/u-boot-branches/u-boot...expanding to full
>> symbols...done.
>> (gdb) *p&stdio_devices*
>> $26 = (struct stdio_dev *(*)[3]) *0x80131c0c*
>> (gdb) info sym stdio_devices
>> __rel_dyn_start + 14024 in section .rel.dyn
>> (gdb) info sym boards
>> boards in section .data
>> (gdb) p *&boards*
>> $27 = (struct board_id (*)[2][2]) *0x8ffb7ec0*
>> (gdb) shell nm u-boot | grep stdio_devices
>> *80131c0c* B stdio_devices
>> (gdb) shell nm u-boot | grep boards
>> *8012dec0* d boards
>> (gdb)
>>
>> Note that "boards" gets properly relocated whereas "stdio_devices" does
>> not - apparently a lot (all?) of the .bss symbols are not properly
>> relocated.  Hmm, I wonder if this is caused by .rel.dyn overlaing .bss...
>>
>> Which version of GDB are you using on ARM that properly relocates all
>> the sections after "add-symbol-file u-boot<addr>"?
> I routinely use ELDK42 (4.2.2 toochain) and stcok (linaro) Ubuntu 
> (4.6.1). I don't remember having hit this issue -- although I am hitting 
> another one where breakpoints are set 4 or 8 bytes further than they 
> should, but the symbols themselves are ok; but I rarely use global .data 
> or .bss symbols, so I may have missed the issue.
>
> Anyway, 'help add-symbol-file' says a single address applies to 
> consecutive sections, so until it is sorted out with the GDB people why 
> this does not work, my NAK still holds.
>
> Amicalement,
I agree with the NAK, its an issue in GDB, not u-boot...


-- 
Peter Barada
peter.barada at logicpd.com