Fix read-only image file handling

index 88e70d3..05ff8cb 100644
@@ -422,7 +422,7 @@ int bdrv_open2(BlockDriverState *bs, const char *filename, int flags,
     /* Note: for compatibility, we open disk image files as RDWR, and
        RDONLY as fallback */
     if (!(flags & BDRV_O_FILE))
-        open_flags = BDRV_O_RDWR | (flags & BDRV_O_CACHE_MASK);
+        open_flags = (flags & BDRV_O_ACCESS) | (flags & BDRV_O_CACHE_MASK);
     else
         open_flags = flags & ~(BDRV_O_FILE | BDRV_O_SNAPSHOT);
     ret = drv->bdrv_open(bs, filename, open_flags);

index b38de55..791666b 100644
@@ -2551,6 +2551,15 @@ static void ide_ioport_write(void *opaque, uint32_t addr, uint32_t val)
         case WIN_WRITE_ONCE:
         case CFA_WRITE_SECT_WO_ERASE:
         case WIN_WRITE_VERIFY:
+            if (bdrv_is_read_only(s->bs)) {
+#if defined(DEBUG_IDE)
+                printf("Attempt to write on read-only device %s\n", s->bs->filename);
+#endif
+                s->status = WRERR_STAT;
+                s->error = ABRT_ERR;
+                ide_set_irq(s);
+                break;
+            }
 	    ide_cmd_lba48_transform(s, lba48);
             s->error = 0;
             s->status = SEEK_STAT | READY_STAT;

@@ -2573,6 +2582,15 @@ static void ide_ioport_write(void *opaque, uint32_t addr, uint32_t val)
         case CFA_WRITE_MULTI_WO_ERASE:
             if (!s->mult_sectors)
                 goto abort_cmd;
+	    if (bdrv_is_read_only(s->bs)) {
+#if defined(DEBUG_IDE)
+                printf("Attempt to multiwrite on read-only device %s\n", s->bs->filename);
+#endif
+                s->status = WRERR_STAT;
+                s->error = ABRT_ERR;
+                ide_set_irq(s);
+                break;
+	    }
 	    ide_cmd_lba48_transform(s, lba48);
             s->error = 0;
             s->status = SEEK_STAT | READY_STAT;

@@ -2598,6 +2616,15 @@ static void ide_ioport_write(void *opaque, uint32_t addr, uint32_t val)
         case WIN_WRITEDMA_ONCE:
             if (!s->bs)
                 goto abort_cmd;
+            if (bdrv_is_read_only(s->bs)) {
+#if defined(DEBUG_IDE)
+                printf("Attempt to DMA write to read-only device %s\n", s->bs->filename);
+#endif
+                s->status = WRERR_STAT;
+                s->error = ABRT_ERR;
+                ide_set_irq(s);
+                break;
+            }
 	    ide_cmd_lba48_transform(s, lba48);
             ide_sector_write_dma(s);
             s->media_changed = 1;

index 9745ca3..db808d4 100644
@@ -35,6 +35,7 @@ do { fprintf(stderr, "scsi-disk: " fmt , ##args); } while (0)
 #define SENSE_NOT_READY       2
 #define SENSE_HARDWARE_ERROR  4
 #define SENSE_ILLEGAL_REQUEST 5
+#define SENSE_DATA_PROTECT    7
 
 #define STATUS_GOOD            0
 #define STATUS_CHECK_CONDITION 2

@@ -234,6 +235,9 @@ static int scsi_handle_write_error(SCSIRequest *r, int error)
             || action == BLOCK_ERR_STOP_ANY) {
         r->status |= SCSI_REQ_STATUS_RETRY;
         vm_stop(0);
+    } else if (error == SENSE_DATA_PROTECT) {
+        scsi_command_complete(r, STATUS_CHECK_CONDITION,
+                SENSE_DATA_PROTECT);
     } else {
         scsi_command_complete(r, STATUS_CHECK_CONDITION,
                 SENSE_HARDWARE_ERROR);

@@ -305,6 +309,11 @@ static int scsi_write_data(SCSIDevice *d, uint32_t tag)
         return 1;
     }
 
+    if (bdrv_is_read_only(r->dev->bdrv)) {
+        scsi_write_complete(r, SENSE_DATA_PROTECT);
+        return 1;
+    }
+
     if (r->aiocb)
         BADF("Data transfer already in progress\n");
 

index b6d86ce..94ee0e2 100644
@@ -343,6 +343,11 @@ void xenstore_parse_domain_config(int hvm_domid)
     BlockDriverState *bs;
     BlockDriver *format;
 
+    /* Read-only handling for image files */
+    char *mode = NULL;
+    int flags;
+    int is_readonly;
+
     /* paths controlled by untrustworthy guest, and values read from them */
     char *danger_path;
     char *danger_buf = NULL;

@@ -532,7 +537,24 @@ void xenstore_parse_domain_config(int hvm_domid)
 		}
 	    }
             pstrcpy(bs->filename, sizeof(bs->filename), params);
-            if (bdrv_open2(bs, params, BDRV_O_CACHE_WB /* snapshot and write-back */, format) < 0)
+
+            flags = BDRV_O_CACHE_WB; /* snapshot and write-back */
+            is_readonly = 0;
+            if (pasprintf(&buf, "%s/mode", bpath) == -1)
+                continue;
+            free(mode);
+            mode = xs_read(xsh, XBT_NULL, buf, &len);
+            if (mode == NULL)
+                continue;
+            if (strchr(mode, 'r') && !strchr(mode, 'w'))
+                is_readonly = 1;
+
+            if (!is_readonly)
+                flags |= BDRV_O_ACCESS & O_RDWR;
+
+            fprintf(stderr, "Using file %s in read-%s mode\n", bs->filename, is_readonly ? "only" : "write");
+
+            if (bdrv_open2(bs, params, flags, format) < 0)
                 fprintf(stderr, "qemu: could not open vbd '%s' or hard disk image '%s' (drv '%s' format '%s')\n", buf, params, drv ? drv : "?", format ? format->format_name : "0");
         }
 

@@ -679,6 +701,7 @@ void xenstore_parse_domain_config(int hvm_domid)
 
  out:
     free(danger_type);
+    free(mode);
     free(params);
     free(dev);
     free(bpath);