KVM: x86: Use macros for x86_emulate_ops to avoid future mistakes

The return values from x86_emulate_ops are defined
in kvm_emulate.h as macros X86EMUL_*.

But in emulate.c, we are comparing the return values
from these ops with 0 to check if they're X86EMUL_CONTINUE
or not: X86EMUL_CONTINUE is defined as 0 now.

To avoid possible mistakes in the future, this patch
substitutes "X86EMUL_CONTINUE" for "0" that are being
compared with the return values from x86_emulate_ops.

  We think that there are more places we should use these
  macros, but the meanings of rc values in x86_emulate_insn()
  were not so clear at a glance. If we use proper macros in
  this function, we would be able to follow the flow of each
  emulation more easily and, maybe, more securely.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 36 insertions, 29 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 0f89e320bc96..48c7f9f8a08f 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1196,7 +1196,7 @@ static int emulate_pop(struct x86_emulate_ctxt *ctxt,
         rc = ops->read_emulated(register_address(c, ss_base(ctxt),
                                                  c->regs[VCPU_REGS_RSP]),
                                 dest, len, ctxt->vcpu);
-        if (rc != 0)
+        if (rc != X86EMUL_CONTINUE)
                 return rc;
 
         register_address_increment(c, &c->regs[VCPU_REGS_RSP], len);
@@ -1370,7 +1370,7 @@ static inline int emulate_grp9(struct x86_emulate_ctxt *ctxt,
         int rc;
 
         rc = ops->read_emulated(memop, &old, 8, ctxt->vcpu);
-        if (rc != 0)
+        if (rc != X86EMUL_CONTINUE)
                 return rc;
 
         if (((u32) (old >> 0) != (u32) c->regs[VCPU_REGS_RAX]) ||
@@ -1385,7 +1385,7 @@ static inline int emulate_grp9(struct x86_emulate_ctxt *ctxt,
                        (u32) c->regs[VCPU_REGS_RBX];
 
                 rc = ops->cmpxchg_emulated(memop, &old, &new, 8, ctxt->vcpu);
-                if (rc != 0)
+                if (rc != X86EMUL_CONTINUE)
                         return rc;
                 ctxt->eflags |= EFLG_ZF;
         }
@@ -1451,7 +1451,7 @@ static inline int writeback(struct x86_emulate_ctxt *ctxt,
                                         &c->dst.val,
                                         c->dst.bytes,
                                         ctxt->vcpu);
-                if (rc != 0)
+                if (rc != X86EMUL_CONTINUE)
                         return rc;
                 break;
         case OP_NONE:
@@ -1749,7 +1749,7 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
                                         &c->src.val,
                                         c->src.bytes,
                                         ctxt->vcpu);
-                if (rc != 0)
+                if (rc != X86EMUL_CONTINUE)
                         goto done;
                 c->src.orig_val = c->src.val;
         }
@@ -1768,12 +1768,15 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
                         c->dst.ptr = (void *)c->dst.ptr +
                                                    (c->src.val & mask) / 8;
                 }
-                if (!(c->d & Mov) &&
-                                   /* optimisation - avoid slow emulated read */
-                    ((rc = ops->read_emulated((unsigned long)c->dst.ptr,
-                                           &c->dst.val,
-                                          c->dst.bytes, ctxt->vcpu)) != 0))
-                        goto done;
+                if (!(c->d & Mov)) {
+                        /* optimisation - avoid slow emulated read */
+                        rc = ops->read_emulated((unsigned long)c->dst.ptr,
+                                                &c->dst.val,
+                                                c->dst.bytes,
+                                                ctxt->vcpu);
+                        if (rc != X86EMUL_CONTINUE)
+                                goto done;
+                }
         }
         c->dst.orig_val = c->dst.val;
 
@@ -2039,11 +2042,12 @@ special_insn:
                 c->dst.ptr = (unsigned long *)register_address(c,
                                                    es_base(ctxt),
                                                    c->regs[VCPU_REGS_RDI]);
-                if ((rc = ops->read_emulated(register_address(c,
-                                           seg_override_base(ctxt, c),
-                                        c->regs[VCPU_REGS_RSI]),
+                rc = ops->read_emulated(register_address(c,
+                                                seg_override_base(ctxt, c),
+                                                c->regs[VCPU_REGS_RSI]),
                                         &c->dst.val,
-                                        c->dst.bytes, ctxt->vcpu)) != 0)
+                                        c->dst.bytes, ctxt->vcpu);
+                if (rc != X86EMUL_CONTINUE)
                         goto done;
                 register_address_increment(c, &c->regs[VCPU_REGS_RSI],
                                        (ctxt->eflags & EFLG_DF) ? -c->dst.bytes
@@ -2058,10 +2062,11 @@ special_insn:
                 c->src.ptr = (unsigned long *)register_address(c,
                                        seg_override_base(ctxt, c),
                                                    c->regs[VCPU_REGS_RSI]);
-                if ((rc = ops->read_emulated((unsigned long)c->src.ptr,
-                                                &c->src.val,
-                                                c->src.bytes,
-                                                ctxt->vcpu)) != 0)
+                rc = ops->read_emulated((unsigned long)c->src.ptr,
+                                        &c->src.val,
+                                        c->src.bytes,
+                                        ctxt->vcpu);
+                if (rc != X86EMUL_CONTINUE)
                         goto done;
 
                 c->dst.type = OP_NONE; /* Disable writeback. */
@@ -2069,10 +2074,11 @@ special_insn:
                 c->dst.ptr = (unsigned long *)register_address(c,
                                                    es_base(ctxt),
                                                    c->regs[VCPU_REGS_RDI]);
-                if ((rc = ops->read_emulated((unsigned long)c->dst.ptr,
-                                                &c->dst.val,
-                                                c->dst.bytes,
-                                                ctxt->vcpu)) != 0)
+                rc = ops->read_emulated((unsigned long)c->dst.ptr,
+                                        &c->dst.val,
+                                        c->dst.bytes,
+                                        ctxt->vcpu);
+                if (rc != X86EMUL_CONTINUE)
                         goto done;
 
                 DPRINTF("cmps: mem1=0x%p mem2=0x%p\n", c->src.ptr, c->dst.ptr);
@@ -2102,12 +2108,13 @@ special_insn:
                 c->dst.type = OP_REG;
                 c->dst.bytes = (c->d & ByteOp) ? 1 : c->op_bytes;
                 c->dst.ptr = (unsigned long *)&c->regs[VCPU_REGS_RAX];
-                if ((rc = ops->read_emulated(register_address(c,
-                                                 seg_override_base(ctxt, c),
-                                                 c->regs[VCPU_REGS_RSI]),
-                                                 &c->dst.val,
-                                                 c->dst.bytes,
-                                                 ctxt->vcpu)) != 0)
+                rc = ops->read_emulated(register_address(c,
+                                                seg_override_base(ctxt, c),
+                                                c->regs[VCPU_REGS_RSI]),
+                                        &c->dst.val,
+                                        c->dst.bytes,
+                                        ctxt->vcpu);
+                if (rc != X86EMUL_CONTINUE)
                         goto done;
                 register_address_increment(c, &c->regs[VCPU_REGS_RSI],
                                        (ctxt->eflags & EFLG_DF) ? -c->dst.bytes