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.
--
Gleb.
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