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Improve partition table code. 

Code to check partition tables used some needless casts
and was broken, using a u8 when a u32 was wanted.

So create structure describing the tables rather than using offset,
and read into those tables instead.

Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
NeilBrown 2010-03-09 10:57:57 +11:00
parent 10adfe9ae7
commit 056b331efe
1 changed files with 49 additions and 21 deletions
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70
util.c
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@ -82,25 +82,55 @@ struct MBR_part_record {
__u32 blocks_num;
};
struct MBR {
__u8 pad[446];
struct MBR_part_record parts[4];
__u16 magic;
} __attribute__((packed));
struct GPT_part_entry {
unsigned char type_guid[16];
unsigned char partition_guid[16];
unsigned char starting_lba[8];
unsigned char ending_lba[8];
__u64 starting_lba;
__u64 ending_lba;
unsigned char attr_bits[8];
unsigned char name[72];
};
} __attribute__((packed));
struct GPT {
__u64 magic;
__u32 revision;
__u32 header_size;
__u32 crc;
__u32 pad1;
__u64 current_lba;
__u64 backup_lba;
__u64 first_lba;
__u64 last_lba;
__u8 guid[16];
__u64 part_start;
__u32 part_cnt;
__u32 part_size;
__u32 part_crc;
__u8 pad2[420];
} __attribute__((packed));
/* Force a compilation error if condition is true */
#define BUILD_BUG_ON(condition) ((void)BUILD_BUG_ON_ZERO(condition))
/* Force a compilation error if condition is true, but also produce a
result (of value 0 and type size_t), so the expression can be used
e.g. in a structure initializer (or where-ever else comma expressions
aren't permitted). */
#define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); }))
/* MBR/GPT magic numbers */
#define MBR_SIGNATURE_MAGIC __cpu_to_le16(0xAA55)
#define GPT_SIGNATURE_MAGIC __cpu_to_le64(0x5452415020494645ULL)
#define MBR_SIGNATURE_OFFSET 510
#define MBR_PARTITION_TABLE_OFFSET 446
#define MBR_PARTITIONS 4
#define MBR_GPT_PARTITION_TYPE 0xEE
#define GPT_ALL_PARTITIONS_OFFSET 80
#define GPT_ENTRY_SIZE_OFFSET 84
/*
* Parse a 128 bit uuid in 4 integers
@ -1141,8 +1171,8 @@ int get_dev_size(int fd, char *dname, unsigned long long *sizep)
*/
static int get_gpt_last_partition_end(int fd, unsigned long long *endofpart)
{
struct GPT gpt;
unsigned char buf[512];
__u64 *buf64;
unsigned char empty_gpt_entry[16]= {0};
struct GPT_part_entry *part;
unsigned long long curr_part_end;
@ -1151,18 +1181,18 @@ static int get_gpt_last_partition_end(int fd, unsigned long long *endofpart)
*endofpart = 0;
BUILD_BUG_ON(sizeof(gpt) != 512);
/* read GPT header */
lseek(fd, 512, SEEK_SET);
if (read(fd, buf, 512) != 512)
if (read(fd, &gpt, 512) != 512)
return 0;
/* get the number of partition entries and the entry size */
all_partitions = __le32_to_cpu(buf[GPT_ALL_PARTITIONS_OFFSET]);
entry_size = __le32_to_cpu(buf[GPT_ENTRY_SIZE_OFFSET]);
all_partitions = __le32_to_cpu(gpt.part_cnt);
entry_size = __le32_to_cpu(gpt.part_size);
/* Check GPT signature*/
buf64 = (__u64*)buf;
if (buf64[0] != GPT_SIGNATURE_MAGIC)
if (gpt.magic != GPT_SIGNATURE_MAGIC)
return -1;
/* sanity checks */
@ -1180,8 +1210,7 @@ static int get_gpt_last_partition_end(int fd, unsigned long long *endofpart)
/* is this valid partition? */
if (memcmp(part->type_guid, empty_gpt_entry, 16) != 0) {
/* check the last lba for the current partition */
buf64 = (__u64*)part->ending_lba;
curr_part_end = __le64_to_cpu(buf64[0]);
curr_part_end = __le64_to_cpu(part->ending_lba);
if (curr_part_end > *endofpart)
*endofpart = curr_part_end;
}
@ -1204,7 +1233,7 @@ static int get_gpt_last_partition_end(int fd, unsigned long long *endofpart)
*/
static int get_last_partition_end(int fd, unsigned long long *endofpart)
{
unsigned char boot_sect[512];
struct MBR boot_sect;
struct MBR_part_record *part;
unsigned long long curr_part_end;
int part_nr;
@ -1212,18 +1241,17 @@ static int get_last_partition_end(int fd, unsigned long long *endofpart)
*endofpart = 0;
BUILD_BUG_ON(sizeof(boot_sect) != 512);
/* read MBR */
lseek(fd, 0, 0);
if (read(fd, boot_sect, 512) != 512)
if (read(fd, &boot_sect, 512) != 512)
goto abort;
/* check MBP signature */
if (*((__u16*)(boot_sect + MBR_SIGNATURE_OFFSET))
== MBR_SIGNATURE_MAGIC) {
if (boot_sect.magic == MBR_SIGNATURE_MAGIC) {
retval = 1;
/* found the correct signature */
part = (struct MBR_part_record*)
(boot_sect + MBR_PARTITION_TABLE_OFFSET);
part = boot_sect.parts;
for (part_nr=0; part_nr < MBR_PARTITIONS; part_nr++) {
/* check for GPT type */