Re: [Adeos-main] [PATCH 3/3] i386: Cleanup root IRQ trampolines

[Philippe Gerum <rpm@xenomai.org>]

Jan Kiszka wrote:
> Philippe Gerum wrote:
>> Jan Kiszka wrote:
>>> Simplifies xirq trampoline and applies the xirq refactorings to
>>> virq_handler too.
>>>
>> --- linux-2.6.23.12-xeno.orig/include/asm-i386/ipipe.h
>> +++ linux-2.6.23.12-xeno/include/asm-i386/ipipe.h
>> @@ -141,11 +141,7 @@ __ipipe_call_root_xirq_handler(unsigned
>>  		"pushl %%ds\n\t"
>>  		"pushl %%eax\n\t"
>>  		"pushl %%ebp\n\t"
>> -		"pushl %%edi\n\t"
>> -		"pushl %%esi\n\t"
>> -		"pushl %%edx\n\t"
>> -		"pushl %%ecx\n\t"
>> -		"pushl %%ebx\n\t"
>> +		"subl  $5*4,%%esp	# rest can remain unsaved\n\t"
>>
>> This won't work. We actually want to save our regs, so that they are
>> restored when going back to xirq_end through the iret path. If we don't
>> save them, the registers will remain terminally clobbered.
> 
> General purpose registers aren't stable across functions calls. But it
> is a valid question what the compiler assumes due to the function
> inlining here. So declaring those five clobbered should be safe enough -
> but if you prefer to add a few extra cycles for safety, keep it as
> explicit as it was :->.
> 

Declaring clobbers would duplicate what entry.S already does when
restoring args from the interrupt frame.

-- 
Philippe.