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>

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 6df88c7..adc9867 100644 (file)
--- 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;
 }