Gleb Natapov wrote:
> On Wed, Apr 14, 2010 at 02:11:39PM +0200, Jan Kiszka wrote:
>> static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt,
>> - struct x86_emulate_ops *ops,
>> - u16 tss_selector, int reason)
>> + struct x86_emulate_ops *ops,
>> + u16 tss_selector, int reason,
>> + bool has_error_code, u32 error_code)
>> {
>> struct desc_struct curr_tss_desc, next_tss_desc;
>> int ret;
>> @@ -2416,12 +2417,23 @@ static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt,
>> ops->set_cached_descriptor(&next_tss_desc, VCPU_SREG_TR, ctxt->vcpu);
>> ops->set_segment_selector(tss_selector, VCPU_SREG_TR, ctxt->vcpu);
>>
>> + if (ret == X86EMUL_CONTINUE && has_error_code) {
> It looks like we shouldn't get here if ret != X86EMUL_CONTINUE in the
> first place. This check should be done just after call to
> task_switch_16/32. Not directly related to your patch, but still...
>
>> @@ -2416,12 +2417,23 @@ static int emulator_do_task_switch(struct
>> x86_emulate_ctxt *ctxt,
>> ops->set_cached_descriptor(&next_tss_desc, VCPU_SREG_TR,
>> ctxt->vcpu);
>> ops->set_segment_selector(tss_selector, VCPU_SREG_TR,
>> ctxt->vcpu);
>>
>> + if (ret == X86EMUL_CONTINUE && has_error_code) {
>> + struct decode_cache *c = &ctxt->decode;
>> +
>> + c->op_bytes = c->ad_bytes = (next_tss_desc.type & 8) ? 4
>> : 2;
>> + c->lock_prefix = 0;
>> + c->src.val = (unsigned long) error_code;
>> + emulate_push(ctxt);
>> + ret = writeback(ctxt, ops);
>> + }
> I would move writeback() to emulator_task_switch(). Just make
> c->dst.type = OP_NONE if writeback is not needed.
BTW, how is state rollback realized if one of the steps raises an
exception? Or where are the new state bits saved until the whole
operation has succeeded so that they can be applied?
Jan
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
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