RE: [ECOS] Multi thread Debugging

[Fabrice Gautier <Fabrice_Gautier@sdesigns.com>]

> -----Original Message-----
> From: Jonathan Larmour [ mailto:jlarmour@redhat.co.uk ]
> Subject: Re: [ECOS] Multi thread Debugging
> 
> 
> 
> The stack_ptr member is there for a different purpose than 
> saved_context.
> saved_context is for GDB debugging purposes only and provides the full
> context. AFAIK interrupt_end is the only place that stores 
> the context in
> saved_context.

In fact I've seen that when saved_context member is NULL, the stack_ptr is
used instead.
 

> This is interesting - it's not clear to me either how 
> saved_context is set
> if threads get rescheduled for any reason other than an interrupt.

It is not set at all. But get_saved_context get the registers from
stack_ptr.
 
> Is this a bug?

It doesn't seem 
 
> I wouldn't have thought this would have caused a problem on the scale
> Fabrice is seeing at any rate.

The problem may be elsewhere.

May be here: (Warning, this is i386 PC specific stuff now)

void hal_get_gdb_registers(target_register_t * d, HAL_SavedRegisters * s)
{
	int i ;

	for (i = 0; i < NUMREGS; i++)
		d[i] = hal_pc_trap_registers[i] ;
} 

This is seen in hal/i386/pc/current/src/plf_stub.c. Note how this function
does not use the 's' parameter while all we need is in there. This is called
in dbg_getthreadreg and 's' would be either saved_context or stack_ptr.

I found another version of this function in
hal/i386/arch/current/src/i386_stub.c

#if 0
void hal_get_gdb_registers(target_register_t * d, HAL_SavedRegisters * s)
{
	d[ESP] = s->esp ;
	d[ESP] = s->esp ;
	d[EBP] = s->ebp ;
	d[EBX] = s->ebx ;
	d[ESI] = s->esi ;
	d[EDI] = s->edi ;
	d[PC] = s->eip ;
}
#endif

This one looks better, but unfortunately there is no s->eip. The
HAL_SavedRegister doesn't have one. Unfortunate.

If someone know why this version has been discarded and what the other is
intented to do it sould be fun.

Thanks

A+

-- 
Fabrice Gautier
fabrice_gautier@sdesigns.com