decoder fix for cut/paste bug in rm decoding

diff --git a/palacios/include/palacios/vmm_instr_decoder.h b/palacios/include/palacios/vmm_instr_decoder.h
index 53831c4..ce494e7 100644 (file)
--- a/palacios/include/palacios/vmm_instr_decoder.h
+++ b/palacios/include/palacios/vmm_instr_decoder.h
@@ -681,7 +681,6 @@ static int decode_rm_operand32(struct guest_info * core,
        }
 
        if (has_sib_byte) {
-           instr_cursor += 1;
            struct sib_byte * sib = (struct sib_byte *)(instr_cursor);
            int scale = 0x1 << sib->scale;
 
@@ -736,6 +735,9 @@ static int decode_rm_operand32(struct guest_info * core,
                case 5:
                    if (modrm->mod != 0) {
                        base_addr += ADDR_MASK(gprs->rbp, 4);
+                   } else {
+                       mod_mode = DISP32;
+                       base_addr = 0;
                    }
                    break;
                case 6:
@@ -888,7 +890,6 @@ int decode_rm_operand64(struct guest_info * core, uint8_t * modrm_instr,
        }
 
        if (has_sib_byte) {
-           instr_cursor += 1;
            struct sib_byte * sib = (struct sib_byte *)(instr_cursor);
            int scale = 0x1 << sib->scale;
            uint8_t index_val = sib->index;
@@ -972,6 +973,9 @@ int decode_rm_operand64(struct guest_info * core, uint8_t * modrm_instr,
                case 5:
                    if (modrm->mod != 0) {
                        base_addr += gprs->rbp;
+                   } else {
+                       mod_mode = DISP32;
+                       base_addr = 0;
                    }
                    break;
                case 6: