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Commit 03ebebeb authored by Avi Kivity's avatar Avi Kivity Committed by Marcelo Tosatti
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KVM: x86 emulator: Leave segment limit and attributs alone in real mode 



When loading a segment in real mode, only the base and selector must
be modified.  The limit needs to be left alone, otherwise big real mode
users will hit a #GP due to limit checking (currently this is suppressed
because we don't check limits in real mode).

Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent e2a610d7

arch/x86/kvm/emulate.c

+2 −6
Original line number Original line Diff line number Diff line
@@ -1388,19 +1388,15 @@ static int load_segment_descriptor(struct x86_emulate_ctxt *ctxt, 
	bool null_selector = !(selector & ~0x3); /* 0000-0003 are null */

	bool null_selector = !(selector & ~0x3); /* 0000-0003 are null */

	ulong desc_addr;

	ulong desc_addr;

	int ret;

	int ret;

	u16 dummy;





	memset(&seg_desc, 0, sizeof seg_desc);

	memset(&seg_desc, 0, sizeof seg_desc);





	if ((seg <= VCPU_SREG_GS && ctxt->mode == X86EMUL_MODE_VM86)

	if ((seg <= VCPU_SREG_GS && ctxt->mode == X86EMUL_MODE_VM86)

	    || ctxt->mode == X86EMUL_MODE_REAL) {

	    || ctxt->mode == X86EMUL_MODE_REAL) {

		/* set real mode segment descriptor */

		/* set real mode segment descriptor */

		ctxt->ops->get_segment(ctxt, &dummy, &seg_desc, NULL, seg);

		set_desc_base(&seg_desc, selector << 4);

		set_desc_base(&seg_desc, selector << 4);

		set_desc_limit(&seg_desc, 0xffff);

		seg_desc.type = 3;

		seg_desc.p = 1;

		seg_desc.s = 1;

		if (ctxt->mode == X86EMUL_MODE_VM86)

			seg_desc.dpl = 3;

		goto load;

		goto load;

	}

	}