Merge branch 'for-next/fat-detection'

common/filetype.c

@@ -26,6 +26,7 @@
 #include <fcntl.h>
 #include <fs.h>
 #include <malloc.h>
+#include <errno.h>
 
 static const char *filetype_str[] = {
 	[filetype_unknown] = "unknown",
@@ -42,6 +43,7 @@ static const char *filetype_str[] = {
 	[filetype_sh] = "Bourne Shell",
 	[filetype_mips_barebox] = "MIPS barebox image",
 	[filetype_fat] = "FAT filesytem",
+	[filetype_mbr] = "MBR sector",
 };
 
 const char *file_type_to_string(enum filetype f)
@@ -52,26 +54,51 @@ const char *file_type_to_string(enum filetype f)
 	return NULL;
 }
 
-static int is_fat(u8 *buf)
+#define MBR_StartSector		8	/* MBR: Offset of Starting Sector in Partition Table Entry */
+#define BS_55AA			510	/* Boot sector signature (2) */
+#define MBR_Table		446	/* MBR: Partition table offset (2) */
+#define BS_FilSysType32		82	/* File system type (1) */
+#define BS_FilSysType		54	/* File system type (1) */
+
+enum filetype is_fat_or_mbr(const unsigned char *sector, unsigned long *bootsec)
 {
-	if (get_unaligned_le16(&buf[510]) != 0xAA55)
-		return 0;
+	/*
+	 * bootsec can be used to return index of the first sector in the
+	 * first partition
+	 */
+	if (bootsec)
+		*bootsec = 0;
 
-	/* FAT */
-	if ((get_unaligned_le32(&buf[54]) & 0xFFFFFF) == 0x544146)
-		return 1;
+	/*
+	 * Check record signature (always placed at offset 510 even if the
+	 * sector size is > 512)
+	 */
+	if (get_unaligned_le16(&sector[BS_55AA]) != 0xAA55)
+		return filetype_unknown;
 
-	/* FAT32 */
-	if ((get_unaligned_le32(&buf[82]) & 0xFFFFFF) == 0x544146)
-		return 1;
+	/* Check "FAT" string */
+	if ((get_unaligned_le32(&sector[BS_FilSysType]) & 0xFFFFFF) == 0x544146)
+		return filetype_fat;
 
-	return 0;
+	if ((get_unaligned_le32(&sector[BS_FilSysType32]) & 0xFFFFFF) == 0x544146)
+		return filetype_fat;
+
+	if (bootsec)
+		/*
+		 * This must be an MBR, so return the starting sector of the
+		 * first partition so we could check if there is a FAT boot
+		 * sector there
+		 */
+		*bootsec = get_unaligned_le16(&sector[MBR_Table + MBR_StartSector]);
+
+	return filetype_mbr;
 }
 
 enum filetype file_detect_type(void *_buf)
 {
 	u32 *buf = _buf;
 	u8 *buf8 = _buf;
+	enum filetype type;
 
 	if (strncmp(buf8, "#!/bin/sh", 9) == 0)
 		return filetype_sh;
@@ -99,8 +126,9 @@ enum filetype file_detect_type(void *_buf)
 		return filetype_aimage;
 	if (strncmp(buf8 + 0x10, "barebox", 7) == 0)
 		return filetype_mips_barebox;
-	if (is_fat(buf8))
-		return filetype_fat;
+	type = is_fat_or_mbr(buf8, NULL);
+	if (type != filetype_unknown)
+		return type;
 
 	return filetype_unknown;
 }
@@ -110,6 +138,7 @@ enum filetype file_name_detect_type(const char *filename)
 	int fd, ret;
 	void *buf;
 	enum filetype type = filetype_unknown;
+	unsigned long bootsec;
 
 	fd = open(filename, O_RDONLY);
 	if (fd < 0)
@@ -123,6 +152,21 @@ enum filetype file_name_detect_type(const char *filename)
 
 	type = file_detect_type(buf);
 
+	if (type == filetype_mbr) {
+		/*
+		 * Get the first partition start sector
+		 * and check for FAT in it
+		 */
+		is_fat_or_mbr(buf, &bootsec);
+		ret = lseek(fd, (bootsec) * 512, SEEK_SET);
+		if (ret < 0)
+			goto err_out;
+		ret = read(fd, buf, 512);
+		if (ret < 0)
+			goto err_out;
+		type = is_fat_or_mbr((u8 *)buf, NULL);
+	}
+
 err_out:
 	close(fd);
 	free(buf);

fs/fat/ff.c

@@ -93,6 +93,7 @@
 #include <errno.h>
 #include <malloc.h>
 #include <linux/ctype.h>
+#include <filetype.h>
 #include "ff.h"			/* FatFs configurations and declarations */
 #include "diskio.h"		/* Declarations of low level disk I/O functions */
 
@@ -1531,29 +1532,20 @@ int follow_path (	/* 0(0): successful, !=0: error code */
 /*
  * Load boot record and check if it is an FAT boot record
  */
-static int check_fs (	/* 0:The FAT BR, 1:Valid BR but not an FAT, 2:Not a BR, 3:Disk error */
+static enum filetype check_fs (	/* 0:The FAT BR, 1:Valid BR but not an FAT, 2:Not a BR, 3:Disk error */
 	FATFS *fs,	/* File system object */
-	DWORD sect	/* Sector# (lba) to check if it is an FAT boot record or not */
+	DWORD sect,	/* Sector# (lba) to check if it is an FAT boot record or not */
+	DWORD *bootsec
 )
 {
-	int ret;
+	enum filetype ret;
 
 	/* Load boot record */
 	ret = disk_read(fs, fs->win, sect, 1);
 	if (ret)
-		return ret;
-	/* Check record signature (always placed at offset 510 even if the sector size is>512) */
-	if (LD_WORD(&fs->win[BS_55AA]) != 0xAA55)
-		return -ENODEV;
+		return filetype_unknown;
 
-	/* Check "FAT" string */
-	if ((LD_DWORD(&fs->win[BS_FilSysType]) & 0xFFFFFF) == 0x544146)
-		return 0;
-
-	if ((LD_DWORD(&fs->win[BS_FilSysType32]) & 0xFFFFFF) == 0x544146)
-		return 0;
-
-	return -ENODEV;
+	return is_fat_or_mbr(fs->win, bootsec);
 }
 
 /*
@@ -1565,8 +1557,10 @@ static int chk_mounted (	/* 0(0): successful, !=0: any error occurred */
 )
 {
 	BYTE fmt, b;
+	DWORD first_boot_sect;
 	DWORD bsect, fasize, tsect, sysect, nclst, szbfat;
 	WORD nrsv;
+	enum filetype type;
 
 	INIT_LIST_HEAD(&fs->dirtylist);
 
@@ -1579,9 +1573,16 @@ static int chk_mounted (	/* 0(0): successful, !=0: any error occurred */
 		return -EIO;
 #endif
 	/* Search FAT partition on the drive. Supports only generic partitionings, FDISK and SFD. */
-	fmt = check_fs(fs, bsect = 0);	/* Check sector 0 if it is a VBR */
-	if (fmt)
-		return fmt; /* No FAT volume is found */
+	type = check_fs(fs, bsect = 0, &first_boot_sect);	/* Check sector 0 if it is a VBR */
+	if (type == filetype_mbr) {
+		/* Sector 0 is an MBR, now check for FAT in the first partition */
+		type = check_fs(fs, bsect = first_boot_sect, NULL);
+		if (type != filetype_fat)
+			return -ENODEV;
+	}
+
+	if (type == filetype_unknown)
+		return -ENODEV;
 
 	/* Following code initializes the file system object */
 

include/filetype.h

@@ -19,10 +19,12 @@ enum filetype {
 	filetype_sh,
 	filetype_mips_barebox,
 	filetype_fat,
+	filetype_mbr,
 };
 
 const char *file_type_to_string(enum filetype f);
 enum filetype file_detect_type(void *_buf);
 enum filetype file_name_detect_type(const char *filename);
+enum filetype is_fat_or_mbr(const unsigned char *sector, unsigned long *bootsec);
 
 #endif /* __FILE_TYPE_H */