Re: [RFC, PATCH 5/24] i386 Vmi code patching

[Zachary Amsden <zach@vmware.com>]

Chris Wright wrote:
> * Zachary Amsden (zach@vmware.com) wrote:
>   
>> +static void fixup_translation(struct vmi_annotation *a)
>> +{
>> +	unsigned char *c, *start, *end;
>> +	int left;
>> +
>> +	memcpy(a->nativeEIP, a->translationEIP, a->translation_size);
>> +	start = a->nativeEIP;
>> +	end = a->nativeEIP + a->translation_size;
>> +
>> +	for (c = start; c < end;) {
>> +		switch(*c) {
>> +			case MNEM_CALL_NEAR:
>>
>>     
> Why these restrictions?  How do you do int $0x82, for example?
>   

We don't.  This is the minimal set of instructions that are emitted 
during the annotation.  The instruction sequence is only sufficient to 
call out to the hypervisor ROM.

What we want to do next is to allow the hypervisor itself to do this 
code fixup - in effect, relinking in the local translations, which in 
many cases would then convert to int $0x82 for inline Xen calls.

Zach