From a6e3407bb1570ac5d8d7fc471bca07d531d1dde7 Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Sun, 10 Jun 2012 17:15:39 +0300 Subject: [PATCH] KVM: Fix SS default ESP/EBP based addressing We correctly default to SS when BP is used as a base in 16-bit address mode, but we don't do that for 32-bit mode. Fix by adjusting the default to SS when either ESP or EBP is used as the base register. Signed-off-by: Avi Kivity --- arch/x86/kvm/emulate.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 33ccd757cb11..7552c0ac6e76 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -974,6 +974,12 @@ static void decode_register_operand(struct x86_emulate_ctxt *ctxt, op->orig_val = op->val; } +static void adjust_modrm_seg(struct x86_emulate_ctxt *ctxt, int base_reg) +{ + if (base_reg == VCPU_REGS_RSP || base_reg == VCPU_REGS_RBP) + ctxt->modrm_seg = VCPU_SREG_SS; +} + static int decode_modrm(struct x86_emulate_ctxt *ctxt, struct operand *op) { @@ -1077,15 +1083,20 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt, if ((base_reg & 7) == 5 && ctxt->modrm_mod == 0) modrm_ea += insn_fetch(s32, ctxt); - else + else { modrm_ea += ctxt->regs[base_reg]; + adjust_modrm_seg(ctxt, base_reg); + } if (index_reg != 4) modrm_ea += ctxt->regs[index_reg] << scale; } else if ((ctxt->modrm_rm & 7) == 5 && ctxt->modrm_mod == 0) { if (ctxt->mode == X86EMUL_MODE_PROT64) ctxt->rip_relative = 1; - } else - modrm_ea += ctxt->regs[ctxt->modrm_rm]; + } else { + base_reg = ctxt->modrm_rm; + modrm_ea += ctxt->regs[base_reg]; + adjust_modrm_seg(ctxt, base_reg); + } switch (ctxt->modrm_mod) { case 0: if (ctxt->modrm_rm == 5) -- 2.39.5