Add extra check.

Still, Ventoy is used in some non standard way. (e.g. WuYouBBS)
I have explained in
https://github.com/ventoy/Ventoy/commit/8bbd5a14a3ca4820266bed6afc1314c3f41e76c3

So I add an extra check.
This is also a prepare for the future Ventoy secure boot policy.

GRUB2/MOD_SRC/grub-2.04/grub-core/ventoy/ventoy_cmd.c

@@ -51,6 +51,37 @@
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
+static grub_uint8_t g_check_mbr_data[440] = {
+    0xEB, 0x63, 0x90, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x01, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0xFF, 0xFA, 0x90, 0x90, 0xF6, 0xC2, 0x80, 0x74, 0x05, 0xF6, 0xC2, 0x70,
+    0x74, 0x02, 0xB2, 0x80, 0xEA, 0x79, 0x7C, 0x00, 0x00, 0x31, 0xC0, 0x8E, 0xD8, 0x8E, 0xD0, 0xBC,
+    0x00, 0x20, 0xFB, 0xA0, 0x64, 0x7C, 0x3C, 0xFF, 0x74, 0x02, 0x88, 0xC2, 0x52, 0xBE, 0x90, 0x7D,
+    0xE8, 0x16, 0x01, 0xBE, 0x05, 0x7C, 0xB4, 0x41, 0xBB, 0xAA, 0x55, 0xCD, 0x13, 0x5A, 0x52, 0x72,
+    0x3D, 0x81, 0xFB, 0x55, 0xAA, 0x75, 0x37, 0x83, 0xE1, 0x01, 0x74, 0x32, 0x31, 0xC0, 0x89, 0x44,
+    0x04, 0x40, 0x88, 0x44, 0xFF, 0x89, 0x44, 0x02, 0xC7, 0x04, 0x10, 0x00, 0x66, 0x8B, 0x1E, 0x5C,
+    0x7C, 0x66, 0x89, 0x5C, 0x08, 0x66, 0x8B, 0x1E, 0x60, 0x7C, 0x66, 0x89, 0x5C, 0x0C, 0xC7, 0x44,
+    0x06, 0x00, 0x70, 0xB4, 0x42, 0xCD, 0x13, 0x72, 0x05, 0xBB, 0x00, 0x70, 0xEB, 0x76, 0xB4, 0x08,
+    0xCD, 0x13, 0x73, 0x0D, 0x5A, 0x84, 0xD2, 0x0F, 0x83, 0xD8, 0x00, 0xBE, 0x96, 0x7D, 0xE9, 0x82,
+    0x00, 0x66, 0x0F, 0xB6, 0xC6, 0x88, 0x64, 0xFF, 0x40, 0x66, 0x89, 0x44, 0x04, 0x0F, 0xB6, 0xD1,
+    0xC1, 0xE2, 0x02, 0x88, 0xE8, 0x88, 0xF4, 0x40, 0x89, 0x44, 0x08, 0x0F, 0xB6, 0xC2, 0xC0, 0xE8,
+    0x02, 0x66, 0x89, 0x04, 0x66, 0xA1, 0x60, 0x7C, 0x66, 0x09, 0xC0, 0x75, 0x4E, 0x66, 0xA1, 0x5C,
+    0x7C, 0x66, 0x31, 0xD2, 0x66, 0xF7, 0x34, 0x88, 0xD1, 0x31, 0xD2, 0x66, 0xF7, 0x74, 0x04, 0x3B,
+    0x44, 0x08, 0x7D, 0x37, 0xFE, 0xC1, 0x88, 0xC5, 0x30, 0xC0, 0xC1, 0xE8, 0x02, 0x08, 0xC1, 0x88,
+    0xD0, 0x5A, 0x88, 0xC6, 0xBB, 0x00, 0x70, 0x8E, 0xC3, 0x31, 0xDB, 0xB8, 0x01, 0x02, 0xCD, 0x13,
+    0x72, 0x1E, 0x8C, 0xC3, 0x60, 0x1E, 0xB9, 0x00, 0x01, 0x8E, 0xDB, 0x31, 0xF6, 0xBF, 0x00, 0x80,
+    0x8E, 0xC6, 0xFC, 0xF3, 0xA5, 0x1F, 0x61, 0xFF, 0x26, 0x5A, 0x7C, 0xBE, 0x93, 0x7D, 0xEB, 0x03,
+    0xBE, 0x99, 0x7D, 0xE8, 0x33, 0x00, 0xBE, 0x9C, 0x7D, 0xE8, 0x2D, 0x00, 0xCD, 0x18, 0xEB, 0xFE,
+    0x58, 0x58, 0x58, 0x58, 0x58, 0x58, 0x58, 0x58, 0x58, 0x58, 0x58, 0x58, 0x58, 0x58, 0x58, 0x58,
+    0x56, 0x54, 0x00, 0x47, 0x65, 0x00, 0x48, 0x44, 0x00, 0x52, 0x64, 0x00, 0x20, 0x45, 0x72, 0x0D,
+    0x0A, 0x00, 0xBB, 0x01, 0x00, 0xB4, 0x0E, 0xCD, 0x10, 0xAC, 0x3C, 0x00, 0x75, 0xF4, 0xC3, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 
+};
+
 initrd_info *g_initrd_img_list = NULL;
 initrd_info *g_initrd_img_tail = NULL;
 int g_initrd_img_count = 0;
@@ -479,7 +510,7 @@ static int ventoy_set_check_result(int ret)
         grub_printf(VTOY_WARNING"\n");
         grub_printf(VTOY_WARNING"\n\n\n");
         
-        grub_printf("This is NOT a standard Ventoy device and is NOT supported (0x%x).\n\n", ret);
+        grub_printf("This is NOT a standard Ventoy device and is NOT supported (%d).\n\n", ret);
         grub_printf("You should follow the instructions in https://www.ventoy.net to use Ventoy.\n");
         
         grub_printf("\n\nWill exit after 10 seconds ...... ");
@@ -497,6 +528,8 @@ static int ventoy_check_official_device(grub_device_t dev)
     grub_uint64_t offset;
     char devname[64];
     grub_fs_t fs;
+    grub_uint8_t mbr[512];
+    grub_disk_t disk;
     grub_device_t dev2;
     char *label = NULL;
     struct grub_partition *partition;
@@ -611,7 +644,27 @@ static int ventoy_check_official_device(grub_device_t dev)
 
         grub_device_close(dev2);    
     }
-    
+
+    /* MBR check */
+    disk = grub_disk_open(dev->disk->name);
+    if (!disk)
+    {
+        return ventoy_set_check_result(11);
+    }
+
+    grub_memset(mbr, 0, 512);
+    grub_disk_read(disk, 0, 0, 512, mbr);
+    grub_disk_close(disk);
+
+    g_check_mbr_data[92] = mbr[92];
+    g_check_mbr_data[102] = mbr[102];
+    g_check_mbr_data[103] = mbr[103];
+    grub_memcpy(g_check_mbr_data + 0x180, mbr + 0x180, 16);
+    if (grub_memcmp(g_check_mbr_data, mbr, 440))
+    {
+        return ventoy_set_check_result(12);
+    }
+
     return ventoy_set_check_result(0);
 }