[not solved yet] debugging linux kernel on arm926ejs target

[Madhu]

Hi,

I am not sure how opencd works, but when we do debugging with 
bdi2000/gdb, we do by

a. load kernel using u-boot.

b. from bdi/telnet 'h' to halt, and set the break point (bi <addr>)to 
whatever symbol we have to stop. we use the address listed in the symbol 
table. then say 'go' to resume u-boot.

c. in u-booot, say bootm <addr> to boot.  The kernel has to stop where 
the breakpoint has been put. On bdi/telnet, it will say something like 
"target has entered debug mode"

d. then use gdb and connect the target (target remote bdi-ip:portno) and 
gdb can list the code where the current breakpoint is active.



Regards,
Madhu


On 05/27/2010 08:48 PM, f. achkar wrote:
> anyone successfully debugged linux kernel via openocd + gdb pls read on:
>
> greetings,
>
> I'm newbie and have a s3c2450 based board (arm926ejs), I have a working compressed kernel image
> zImage, this image boots properly via u-boot-1.1.6, however I simply
> failed to debug remotely the vmlinux (root directory of linux source tree) via openocd-0.4.0 with a j-link segger.
> is there a good reference on how to properly debug the linux kernel via openocd/gdb for an arm target on a linux hot machine?
>
> details:
> 1. let u-boot start the board;
> 2. I get the u-boot command prompt:
>
> # bdinfo
>        arch_number = 0x00000648
>        env_t       = 0x00000000
>        boot_params = 0x30000100
>        DRAM bank   = 0x00000000
>        ->  start    = 0x30000000
>        ->  size     = 0x04000000
>        DRAM bank   = 0x00000001
>        ->  start    = 0x38000000
>        ->  size     = 0x04000000
>        ethaddr     = 00:40:5C:26:0A:5B
>        ip_addr     = 192.168.3.5
>        baudrate    = 115200 bps
>
> 3. halt the target via openocd/telnet;
> 4. cd to root directory of linux source code and issue:
> gdb vmlinux
> GNU gdb (GDB) 6.8.50.20090417
> Copyright (C) 2009 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:
> <http://www.gnu.org/software/gdb/bugs/>...
> (gdb)
>
> 5.
> (gdb) target remote localhost:3333
> Remote debugging using localhost:3333
> 0xc3e01874 in ?? ()
> 0xc3e01874:    ldr    r3, [r0, #16]
> (gdb)
>
> 6.
> (gdb) set remote hardware-breakpoint-limit 2
> (gdb) set remote hardware-watchpoint-limit 2
>
> 7.
> (gdb) load
> Loading section .init, size 0x7b000 lma 0xc0008000
> Loading section .text, size 0x2bb618 lma 0xc0083000
> Loading section __ksymtab, size 0x4a58 lma 0xc033f000
> Loading section __ksymtab_gpl, size 0x1360 lma 0xc0343a58
> Loading section __ksymtab_gpl_future, size 0x18 lma 0xc0344db8
> Loading section __ksymtab_strings, size 0xcab7 lma 0xc0344dd0
> Loading section __param, size 0x654 lma 0xc0351888
> Loading section .data, size 0x21538 lma 0xc0352000
> Start address 0xc0008000, load size 3582507
> Transfer rate: 35 KB/sec, 15922 bytes/write.
> (gdb)
>
> 8. if I do continue (gdb) c, then I don't see any output on the serial
> console (as normally do during zImage booting process!)
>
> where I'm messing up? or how should I get on with debugging the linux kernel at jtag level?
>
> thanks,
> ferar
>
>
>
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