Re: [MiNT] [PATCH] ethernat.xif hangs the system if card isn't present

[David Gálvez <dgalvez75@gmail.com>]

2013/2/15 Alan Hourihane <alanh@fairlite.co.uk>:
> On 02/15/13 09:34, Vincent Rivičre wrote:
>>
>> On 14/02/2013 21:07, David Gálvez wrote:
>>>
>>> This patch adds code to change the bus error exception handler before
>>> we try to read the register, and to enable the old one when we're
>>> finish.
>>
>>
>> Is this the right way to do with FreeMiNT?
>> I thought there was high level functions like signal catching, etc...
>>
>
> Mmm, yes, I think it should be possible to do....
>
> sigbus()
> {
> /* failed */
> }
>
> SIGACTION(get_curproc(), SIGBUS).sa_handler = (long) sigbus;
>

Before I made the patch I was unsure if it was a correct practice to
replace the bus error exception handler from a driver,
so I did some investigation, this is what I found out. I think
information below is correct but I'm not 100% sure.

Code inside xdd, xfs and xif modules is run like it was kernel code. Then PID=0.

Take a look at the file sys/signal.c, specially the code below:

/*
 * check_sigs: see if we have any signals pending. if so,
 * handle them.
 */
void
check_sigs (void)
{
	struct proc *p = get_curproc();
	ulong sigs, sigm;
	int i;
	short deliversig;

	if (p->pid == 0)
		return;

Returns if PID is 0 without doing anything, before calling
handle_sig() function where signals are handled.
So I think there is no high level way for signal catching for these drivers.