Subject: Re: Trace

From: Sébastien CHRETIEN<[email-masked]>
Date: Tue, 02 Sep 2008 07:13:17 +0200

My board has only a uart device on a FPGA. I don't use the serial layer 
because it isn't documented in Linux Device Driver 3rd. Only the tty 
layer is documented

Benjamin Herrenschmidt a écrit :
> On Mon, 2008-09-01 at 18:33 +0200, Sébastien Chrétien wrote:
>   
>> Thanks for your answer.
>> Your analyse of ttys is very well. It was not my answer. All adresses in 
>> system.map begin with 0xc... So I think it is the case for ttys too.
>>
>> I found the mistake. It came from my board_device function in struct 
>> console(console ->device). It didn't change the value of the parameter 
>> int* index.
>> So Linux loaded a tty_structure which was in tiny_ttys[-1]
>>
>> console.h is not very well documented about this.
>>     
>
> You have a custom serial port ? Why not use the framework in
> drivers/serial ? Or are you using it ?
>
> Cheers,
> Ben.
>
>   
>> Thanks
>> Sébastien Chrétien
>>
>> Jenkins, Clive a écrit :
>>     
>>>>  Why can't tty have value 0x57555541 ?
>>>>     
>>>>         
>>> To answer my own question, because it ends in 1 and is not word-aligned!
>>>
>>> -----Original Message-----
>>> From: linuxppc-dev-bounces+clive.jenkins=[email-masked] [mailto:linuxppc-dev-bounces+clive.jenkins=[email-masked]] On Behalf Of Jenkins, Clive
>>> Sent: 01 September 2008 14:54
>>> To: Sébastien Chrétien
>>> Cc: [email-masked]
>>> Subject: RE: Trace
>>>
>>> I'm not sure that is a failure. Why can't tty have value 0x57555541 ?
>>>
>>> I think the code in tty_io.c initialises driver->ttys and you shouldn't need to do anything in your driver.
>>>  
>>> If you are not already aware, a useful way to explore kernel code is to use LXR:
>>> http://lxr.linux.no/linux+v2.6.26/include/linux/tty_driver.h#L212
>>> This may help you understand the tty code.
>>>  
>>> Good luck!
>>>  
>>> ________________________________
>>>
>>> From: Sébastien Chrétien [mailto:[email-masked]] 
>>> Sent: 01 September 2008 13:25
>>> To: Jenkins, Clive
>>> Cc: [email-masked]
>>> Subject: Re: Trace
>>>
>>>
>>> I found where is the failure with your advices 
>>> In init_dev (tty_io.c), init_dev calls "tty = driver->ttys[idx]"
>>> after this call, tty value is : tty = 0x57555541
>>>
>>> Have I to initialize driver->ttys in my driver. If yes, how have I to Initialize this ?
>>>
>>> The driver tty is used in order to have a console on my serial port.
>>> Thanks for your help
>>>
>>>
>>>
>>> 2008/9/1, Jenkins, Clive <[email-masked]>: 
>>>
>>> 	The instruction that caused the fault is at this address:
>>> 	
>>> 	> NIP [c0110ddc] init_dev+0x2bc/0x584
>>> 	
>>> 	
>>> 	The hex value of the instruction is also highlighted between <> here:
>>> 	
>>> 	> Instruction dump:
>>> 	> 7d808120 4e800020 7c832378 4bfa9ea9 7c7f1b79 418201f0 a81e0062 2f800001
>>> 	> 409efd98 83ff00d0 2c1f0000 4182fd90 <801f00b8> 70090080 408201b0 801e0060
>>> 	
>>> 	
>>> 	Disassemble your kernel and look at offset 0x2BC relative to the label init_dev
>>> 	
>>> 	________________________________
>>> 	
>>> 	From: linuxppc-dev-bounces+clive.jenkins=[email-masked] [mailto:linuxppc-dev-bounces+clive.jenkins <mailto:linuxppc-dev-bounces%2Bclive.jenkins> =[email-masked]] On Behalf Of Sébastien Chrétien
>>> 	Sent: 01 September 2008 10:16
>>> 	To: [email-masked]
>>> 	Subject: Trace
>>> 	
>>> 	
>>> 	
>>> 	Hello,
>>> 	
>>> 	I am triying to write a tty_driver under ppc. And I get a kernel panic.
>>> 	Can somebody explain me how finding the source of the error with a kernel panic trace :
>>> 	thanks
>>> 	
>>> 	Unable to handle kernel paging request for data at address 0x575555f9
>>> 	Faulting instruction address: 0xc0110ddc
>>> 	Oops: Kernel access of bad area, sig: 11 [#1]
>>> 	Modules linked in:
>>> 	NIP: c0110ddc LR: c011118c CTR: 00000000
>>> 	REGS: cf01bcb0 TRAP: 0300   Not tainted  (2.6.26)
>>> 	MSR: 00009032 <EE,ME,IR,DR>  CR: 44002022  XER: 20000000
>>> 	DAR: 575555f9, DSISR: 40000000
>>> 	TASK = cf01c000[1] 'swapper' THREAD: cf01a000
>>> 	GPR00: 0000000c cf01bd60 cf01c000 cf04c300 ffffffff cf01bdbc 00000000 c01d0000
>>> 	GPR08: 00001249 fffffffc 00000000 cf000420 84002022 00000000 10000b00 007fff00
>>> 	GPR16: 0fffa1d0 00000000 00000004 cf01bdbc 007ffec0 00000000 00000000 00800000
>>> 	GPR24: 00000000 c01b7650 00000002 c01d0000 ffffffff ce4a6700 cf04c300 57555541
>>> 	NIP [c0110ddc] init_dev+0x2bc/0x584
>>> 	LR [c011118c] tty_open+0xe8/0x3e0
>>> 	Call Trace:
>>> 	[cf01bd60] [cf01bd78] 0xcf01bd78 (unreliable)
>>> 	[cf01bdb0] [c011118c] tty_open+0xe8/0x3e0
>>> 	[cf01bde0] [c00742c8] chrdev_open+0x114/0x1b0
>>> 	[cf01be10] [c006fb5c] __dentry_open+0x190/0x2e8
>>> 	[cf01be40] [c006fdac] nameidata_to_filp+0x38/0x70
>>> 	[cf01be60] [c007bc60] do_filp_open+0x200/0x7d0
>>> 	[cf01bf10] [c00700b4] do_sys_open+0x74/0x114
>>> 	[cf01bf40] [c0003c94] init_post+0x34/0x258
>>> 	[cf01bf60] [c019ca64] kernel_init+0x258/0x270
>>> 	[cf01bff0] [c0011b3c] kernel_thread+0x44/0x60
>>> 	Instruction dump:
>>> 	7d808120 4e800020 7c832378 4bfa9ea9 7c7f1b79 418201f0 a81e0062 2f800001
>>> 	409efd98 83ff00d0 2c1f0000 4182fd90 <801f00b8> 70090080 408201b0 801e0060
>>> 	---[ end trace b7795a387aeb7786 ]---
>>> 	Kernel panic - not syncing: Attempted to kill init!
>>> 	allocation failed: out of vmalloc space - use vmalloc=<size> to increase size.
>>> 	
>>> 	
>>>
>>>
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>>>
>>>   
>>>       
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