[PATCH 15/20] KVM: x86 emulator: Fix popf emulation

Avi Kivity
2010-02-17T13:45:25Z

From: Gleb Natapov <gleb@redhat.com>

POPF behaves differently depending on current CPU mode. Emulate correct
logic to prevent guest from changing flags that it can't change otherwise.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Avi Kivity <avi@redhat.com>
---
arch/x86/kvm/emulate.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 54 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 296e851..1782387 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -343,11 +343,18 @@ static u32 group2_table[] = {
};

/* EFLAGS bit definitions. */
+#define EFLG_ID (1<<21)
+#define EFLG_VIP (1<<20)
+#define EFLG_VIF (1<<19)
+#define EFLG_AC (1<<18)
#define EFLG_VM (1<<17)
#define EFLG_RF (1<<16)
+#define EFLG_IOPL (3<<12)
+#define EFLG_NT (1<<14)
#define EFLG_OF (1<<11)
#define EFLG_DF (1<<10)
#define EFLG_IF (1<<9)
+#define EFLG_TF (1<<8)
#define EFLG_SF (1<<7)
#define EFLG_ZF (1<<6)
#define EFLG_AF (1<<4)
@@ -1214,6 +1221,49 @@ static int emulate_pop(struct x86_emulate_ctxt *ctxt,
return rc;
}

+static int emulate_popf(struct x86_emulate_ctxt *ctxt,
+ struct x86_emulate_ops *ops,
+ void *dest, int len)
+{
+ int rc;
+ unsigned long val, change_mask;
+ int iopl = (ctxt->eflags & X86_EFLAGS_IOPL) >> IOPL_SHIFT;
+ int cpl = kvm_x86_ops->get_cpl(ctxt->vcpu);
+
+ rc = emulate_pop(ctxt, ops, &val, len);
+ if (rc != X86EMUL_CONTINUE)
+ return rc;
+
+ change_mask = EFLG_CF | EFLG_PF | EFLG_AF | EFLG_ZF | EFLG_SF | EFLG_OF
+ | EFLG_TF | EFLG_DF | EFLG_NT | EFLG_RF | EFLG_AC | EFLG_ID;
+
+ switch(ctxt->mode) {
+ case X86EMUL_MODE_PROT64:
+ case X86EMUL_MODE_PROT32:
+ case X86EMUL_MODE_PROT16:
+ if (cpl == 0)
+ change_mask |= EFLG_IOPL;
+ if (cpl <= iopl)
+ change_mask |= EFLG_IF;
+ break;
+ case X86EMUL_MODE_VM86:
+ if (iopl < 3) {
+ kvm_inject_gp(ctxt->vcpu, 0);
+ return X86EMUL_PROPAGATE_FAULT;
+ }
+ change_mask |= EFLG_IF;
+ break;
+ default: /* real mode */
+ change_mask |= (EFLG_IOPL | EFLG_IF);
+ break;
+ }
+
+ *(unsigned long *)dest =
+ (ctxt->eflags & ~change_mask) | (val & change_mask);
+
+ return rc;
+}
+
static void emulate_push_sreg(struct x86_emulate_ctxt *ctxt, int seg)
{
struct decode_cache *c = &ctxt->decode;
@@ -2099,7 +2149,10 @@ special_insn:
c->dst.type = OP_REG;
c->dst.ptr = (unsigned long *) &ctxt->eflags;
c->dst.bytes = c->op_bytes;
- goto pop_instruction;
+ rc = emulate_popf(ctxt, ops, &c->dst.val, c->op_bytes);
+ if (rc != X86EMUL_CONTINUE)
+ goto done;
+ break;
case 0xa0 ... 0xa1: /* mov */
c->dst.ptr = (unsigned long *)&c->regs[VCPU_REGS_RAX];
c->dst.val = c->src.val;
--
1.6.5.3