From ab708099a0617e2c37b26d9ecbb373456057ba9b Mon Sep 17 00:00:00 2001 From: Nadav Amit Date: Thu, 25 Dec 2014 02:52:21 +0200 Subject: [PATCH] KVM: x86: POP [ESP] is not emulated correctly According to Intel SDM: "If the ESP register is used as a base register for addressing a destination operand in memory, the POP instruction computes the effective address of the operand after it increments the ESP register." The current emulation does not behave so. The fix required to waste another of the precious instruction flags and to check the flag in decode_modrm. Signed-off-by: Nadav Amit Signed-off-by: Paolo Bonzini --- arch/x86/kvm/emulate.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 8f32c03515ad..cc24b74b7454 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -170,6 +170,7 @@ #define PrivUD ((u64)1 << 51) /* #UD instead of #GP on CPL > 0 */ #define NearBranch ((u64)1 << 52) /* Near branches */ #define No16 ((u64)1 << 53) /* No 16 bit operand */ +#define IncSP ((u64)1 << 54) /* SP is incremented before ModRM calc */ #define DstXacc (DstAccLo | SrcAccHi | SrcWrite) @@ -1227,6 +1228,10 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt, else { modrm_ea += reg_read(ctxt, base_reg); adjust_modrm_seg(ctxt, base_reg); + /* Increment ESP on POP [ESP] */ + if ((ctxt->d & IncSP) && + base_reg == VCPU_REGS_RSP) + modrm_ea += ctxt->op_bytes; } if (index_reg != 4) modrm_ea += reg_read(ctxt, index_reg) << scale; @@ -3758,7 +3763,7 @@ static const struct opcode group1[] = { }; static const struct opcode group1A[] = { - I(DstMem | SrcNone | Mov | Stack, em_pop), N, N, N, N, N, N, N, + I(DstMem | SrcNone | Mov | Stack | IncSP, em_pop), N, N, N, N, N, N, N, }; static const struct opcode group2[] = { -- 2.20.1