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authorFranck Jullien <franck.jullien@gmail.com>2012-09-19 13:09:01 +0200
committerSascha Hauer <s.hauer@pengutronix.de>2012-09-20 08:57:58 +0200
commit010ee209b75c5732ae4144e3ee9ce14158193c1f (patch)
tree1bff850f196d666b8bdbc98a09b8bd3e37354c95 /common/filetype.c
parentdadcac8b382cd912199530f6e5920c7232f7ae1f (diff)
downloadbarebox-010ee209b75c5732ae4144e3ee9ce14158193c1f.tar.gz
filetype: Improve FAT detection
We may have some disk with MBR as a first sector. In this case, the current FAT check returns an error. However, the FAT sector exist and the MBR can tell us where it is. This patch add to file_name_detect_type function the ability to find the FAT boot sector on the first sector of the first partition in case it is not on sector 0. It also introduce is_fat_or_mbr to check if a buffer is a FAT boot or MBR sector Signed-off-by: Franck Jullien <franck.jullien@gmail.com> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Diffstat (limited to 'common/filetype.c')
-rw-r--r--common/filetype.c68
1 files changed, 56 insertions, 12 deletions
diff --git a/common/filetype.c b/common/filetype.c
index e736d43..6a0dcfb 100644
--- a/common/filetype.c
+++ b/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;
+
+ /*
+ * 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;
+
+ /* Check "FAT" string */
+ if ((get_unaligned_le32(&sector[BS_FilSysType]) & 0xFFFFFF) == 0x544146)
+ return filetype_fat;
- /* FAT */
- if ((get_unaligned_le32(&buf[54]) & 0xFFFFFF) == 0x544146)
- return 1;
+ if ((get_unaligned_le32(&sector[BS_FilSysType32]) & 0xFFFFFF) == 0x544146)
+ return filetype_fat;
- /* FAT32 */
- if ((get_unaligned_le32(&buf[82]) & 0xFFFFFF) == 0x544146)
- return 1;
+ 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 0;
+ 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);