KVM: x86 emulator: fix %rip-relative addressing with immediate source operand

%rip-relative addressing is relative to the first byte of the next instruction,
so we need to add %rip only after we've fetched any immediate bytes.

Based on original patch by Li Xin <xin.li@intel.com>.

Signed-off-by: Avi Kivity <avi@redhat.com>
Acked-by: Li Xin <xin.li@intel.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 7 insertions, 5 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 6df88c7885c0..adc98675cda0 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3372,7 +3372,7 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
         int def_op_bytes, def_ad_bytes, goffset, simd_prefix;
         bool op_prefix = false;
         struct opcode opcode;
-        struct operand memop = { .type = OP_NONE };
+        struct operand memop = { .type = OP_NONE }, *memopp = NULL;
 
         c->eip = ctxt->eip;
         c->fetch.start = c->eip;
@@ -3547,9 +3547,6 @@ done_prefixes:
         if (memop.type == OP_MEM && c->ad_bytes != 8)
                 memop.addr.mem.ea = (u32)memop.addr.mem.ea;
 
-        if (memop.type == OP_MEM && c->rip_relative)
-                memop.addr.mem.ea += c->eip;
-
         /*
          * Decode and fetch the source operand: register, memory
          * or immediate.
@@ -3571,6 +3568,7 @@ done_prefixes:
                                                            c->op_bytes;
         srcmem_common:
                 c->src = memop;
+                memopp = &c->src;
                 break;
         case SrcImmU16:
                 rc = decode_imm(ctxt, &c->src, 2, false);
@@ -3667,6 +3665,7 @@ done_prefixes:
         case DstMem:
         case DstMem64:
                 c->dst = memop;
+                memopp = &c->dst;
                 if ((c->d & DstMask) == DstMem64)
                         c->dst.bytes = 8;
                 else
@@ -3700,10 +3699,13 @@ done_prefixes:
                 /* Special instructions do their own operand decoding. */
         default:
                 c->dst.type = OP_NONE; /* Disable writeback. */
-                return 0;
+                break;
         }
 
 done:
+        if (memopp && memopp->type == OP_MEM && c->rip_relative)
+                memopp->addr.mem.ea += c->eip;
+
         return (rc == X86EMUL_UNHANDLEABLE) ? EMULATION_FAILED : EMULATION_OK;
 }