kernel debugging (KGDB or JTAG)

[Jan Pohanka]

Hi Marc,

Dne Tue, 02 Aug 2011 11:32:34 +0200 Marc Titinger <mtittinge at hotmail.com>  
napsal(a):

>
>
>
> ----------------------------------------
>> Subject: kernel debugging (KGDB or JTAG)
>> To: linux-arm-kernel at lists.infradead.org
>> From: xhpohanka at gmail.com
>> Date: Tue, 2 Aug 2011 10:13:45 +0200
>>
>> Dear all,
>
> Hi Jan,
>
>>
>> I'd like to ask if anyone has working setup for kernel debugging on arm
>> target. I have tried two boards (one with at91sam9g20, second with
>> freescale i.mx27) with Segger j-link and kgdb with similar and not very
>> useful results. I have Ubuntu 11.04 as development host and latest
>> codesourcery arm-none-(linux-gnu)eabi toolchain.
>>
>> Using 2.6.39 I was able to compile the sources with KGDB enabled. I'm  
>> also
>> able to enter kdb terminal and connect with arm-none-eabi-gdb. Setting  
>> and
>> triggering breakpoints works well, but single stepping (which is  
>> essential
>> to me) does not. Here is the example
>
> did you select "compile with debug info" in the kernel hacking menu ?

Of course :)

>
>>
>> Breakpoint 1, 0xc00e40d4 in sys_sync () at
>> /home/honza/_dev/kernel/linux-2.6.39.y/fs/sync.c:190
>> 190 }
>> (gdb) list
>> 185 ret = err;
>> 186 mutex_unlock(&mapping->host->i_mutex);
>> 187
>> 188 out:
>> 189 return ret;
>> 190 }
>> 191 EXPORT_SYMBOL(vfs_fsync_range);
>> 192
>> 193 /**
>> 194 * vfs_fsync - perform a fsync or fdatasync on a file
>> (gdb) s
>> Sending packet: $Hc148#48...Ack
>> Packet received: OK
>> Sending packet: $s#73...Ack
>> Packet received:
>> warning: Invalid remote reply:
>>
>> ... now gdb hangs forever
>>
>> Using j-ling JTAG probe from segger I can't start debug session at all.
>> When JLinkGDBServer connects it resets the board and I'm not able to
>> resume the execution. I have found e.g. this howto
>
> you must probably pass some option to tell the jtag interface not to  
> issue the TRST signal and any init "pokes" it might do,  if you to  
> attach to a running kernel instead of booting it through jtag.

I started a thread at segger support forum  
http://segger2.com/index.php?page=Thread&threadID=882, it was stated that  
there is no option to attach only, yet. On the other hand I don't  
understand why the board can't rerun from start (through u-boot etc.).  
Maybe openocd could help here, but I have not got a time to try it, yet.

regards
Jan

>
>
> Cheers,
> Marc.
>
>
>> http://www.timesys.com/embedded-linux/docs/Debug_Linux_kernel_with_a_JTAG_from_Segger
>> but as I said it is not working for me.
>>
>> Here is the log from JLinkGDBServer
>>
>> J-Link connected
>> Firmware: J-Link ARM V8 compiled Jul 5 2011 20:48:23
>> Hardware: V8.00
>> S/N: 58004787
>>
>> J-Link found 2 JTAG devices, Total IRLen = 8
>> JTAG ID: 0x07926121 (ARM9)
>>
>> Connected to 127.0.0.1
>> Reading all registers
>> WARNING: Failed to read cacheable memory @ address 0x00000000
>> Read 4 bytes @ address 0x00000000 (Data = 0x00000000)
>> Starting target CPU...
>>
>>
>> Any advice will be greatly appreciated...
>>
>> with best regards
>> Jan
>>
>> --
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>  		 	   		


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