The problem is easy:
ks0108_init() prints the error message and exit with -EINVAL, so the
module isn't loaded properly.
However, cfag12864b_init() is called, although ks0108 failed. It
returns 0 and after a while cfag12864b calls ks0108_writecontrol()
which dereferences the uninitialized pointer ks0108_parport:
parport_write_control(ks0108_parport, byte ^ (bit(0) | bit(1) | bit(3)));
Why is cfag12864b_init() called if ks0108 module didn't load properly?
Is that normal? If so, how a module should alarm other modules about
it failed loading?
An easy solution woule be to export a function at ks0108.c like
ks0108_inited() that would return if the module was properly inited or
not. Is there any better solution?
Regards,
Miguel
On 2/1/07, Miguel Ojeda <[email protected]> wrote:
On 1/7/07, Daniel Walker <[email protected]> wrote:
> (forgot to CC LKML)
>
> The options,
>
> CONFIG_CFAG12864B=y
> CONFIG_CFAG12864B_RATE=20
>
> causes a crash at boot in 2.6.20-rc3-mm1. I don't have the hardware
> associated with the options. It looks like it just doesn't have guards
> to detect if the hardware doesn't exists.
>
> Here is the crash,
>
> ks0108: ERROR: parport didn't find 888 port
> BUG: unable to handle kernel NULL pointer dereference at virtual address
> 0000004 printing eip:
> c02dbff9
> *pde = 00000000
> Oops: 0000 [#1]
> PREEMPT SMP
> last sysfs file:
> Modules linked in:
> CPU: 3
> EIP: 0060:[<c02dbff9>] Not tainted VLI
> EFLAGS: 00010246 (2.6.20-rc3-mm1 #11)
> EIP is at ks0108_writecontrol+0x79/0xc0
> eax: 00001008 ebx: 0000000a ecx: 673e2eb8 edx: 00000001
> esi: 0000000a edi: 00000000 ebp: f7c3ff6c esp: f7c3ff50
> ds: 007b es: 007b fs: 00d8 gs: 0000 ss: 0068
> Process swapper (pid: 1, ti=f7c3e000 task=f7c26a90 task.ti=f7c3e000)
> Stack: 00000001 f7552c40 f7c3ff60 c0120e3f 00000000 c049f450 00000000
> f7c3ff74
> c02dc159 f7c3ff80 c02dc177 00000000 f7c3ff98 c048feda 00000378
> c02d74db
> 00000000 00000000 f7c3ffe0 c0478610 c03d9d35 00000004 f7c26a90
> c0473fc4
> Call Trace:
> [<c01053da>] show_trace_log_lvl+0x1a/0x30
> [<c0105499>] show_stack_log_lvl+0xa9/0xd0
> [<c01056c7>] show_registers+0x207/0x370
> [<c0105949>] die+0x119/0x250
> [<c011d267>] do_page_fault+0x277/0x610
> [<c038e9d4>] error_code+0x7c/0x84
> [<c02dc159>] cfag12864b_e+0x19/0x20
> [<c02dc177>] cfag12864b_page+0x17/0x30
> [<c048feda>] cfag12864b_init+0x8a/0x130
> [<c0478610>] init+0x110/0x250
> [<c0104fd3>] kernel_thread_helper+0x7/0x14
> =======================
> Code: 8b 98 ec 00 00 00 0f b6 03 24 df 88 45 f3 80 75 f3 20 0f b6 43 01 20
> 45 f
> EIP: [<c02dbff9>] ks0108_writecontrol+0x79/0xc0 SS:ESP 0068:f7c3ff50
> <0>Kernel panic - not syncing: Attempted to kill init!
>
>
>
>
As Daniel Walker pointed out, the driver doesn't probe for the
hardware because it just uses the parallel port for output (there
isn't any kind of input).
The driver shouldn't continue execution and using
ks0108_writecontrol() (which writes to the parallel port) after the
"ks0108: ERROR: parport didn't find 888 port" message.
Will check.
Thanks for the warning,
Miguel
(forgot to reply to all).
--
Miguel Ojeda
http://maxextreme.googlepages.com/index.htm
--
Miguel Ojeda
http://maxextreme.googlepages.com/index.htm
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