diff --git a/src/fs/iso9660.c b/src/fs/iso9660.c
index 555f8ab5..d8641078 100755
--- a/src/fs/iso9660.c
+++ b/src/fs/iso9660.c
@@ -1,7 +1,6 @@
 // This code is released under the MIT License
 
 #include <fs.h>
-
 #define L9660_SEEK_END -1
 #define L9660_SEEK_SET 0
 #define L9660_SEEK_CUR +1
@@ -438,7 +437,14 @@ int iso9660_readfile(file_t file, void *addr, size_t offset, size_t size) {
   l9660_status st;
   st = l9660_seek(fp, SEEK_SET, offset);
   if (st != L9660_OK) return -1;
-  st = l9660_read(fp, addr, size, null);
+  size_t read = 0;
+  size_t total_read = 0;
+  while (total_read < size) {
+    st = l9660_read(fp, (char *)addr + total_read, size - total_read, &read);
+    if (st != L9660_OK) return -1;
+    total_read += read;
+    if (read == 0) break;
+  }
   if (st != L9660_OK) return -1;
   return 0;
 }
diff --git a/src/kernel/hal/dev.c b/src/kernel/hal/dev.c
index 39792d2a..cf56d2a9 100755
--- a/src/kernel/hal/dev.c
+++ b/src/kernel/hal/dev.c
@@ -17,10 +17,9 @@ static int devfs_mkdir(void *parent, cstr name, vfs_node_t node) {
   node->fsid = 0; // 交给vfs处理
   return 0;
 }
-static void dummy() {
-}
+static void dummy() {}
 // offset 必须能被扇区大小整除
-static int devfs_read(void *file, void *addr, size_t offset, size_t size) {
+static int  devfs_read(void *file, void *addr, size_t offset, size_t size) {
   int dev_id = (int)file;
   int sector_size;
   if (vdisk_ctl[dev_id].flag == 0) return -1;
diff --git a/src/kernel/task/basetask.c b/src/kernel/task/basetask.c
index ffb3cf42..3df138af 100755
--- a/src/kernel/task/basetask.c
+++ b/src/kernel/task/basetask.c
@@ -231,6 +231,26 @@ void shell() {
       buf[size] = '\0';
       printf("%s\n", buf);
       free(buf);
+    } else if (strneq(ch, "readhex ", 8)) {
+      char      *s = ch + 8;
+      vfs_node_t p = vfs_open(s);
+      if (!p) {
+        printf("open %s failed\n", s);
+        continue;
+      }
+      if (p->type == file_dir) {
+        printf("not a file\n");
+        continue;
+      }
+      size_t size = p->size;
+      byte  *buf  = malloc(size);
+      memset(buf, 0, size);
+      vfs_read(p, buf, 0, size);
+      for (size_t i = 0; i < size; i++) {
+        printf("%02x ", buf[i]);
+      }
+      printf("\n");
+      free(buf);
     } else if (strneq(ch, "mkdir ", 6)) {
       vfs_mkdir(ch + 6);
     } else if (strneq(ch, "mount ", 6)) {