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>

diff --git a/util.c b/util.c
index 66be82ab8082696931ee457003db5dc4d261f0b0..d292a6603a2c2f87791120fae830979d7e2f8ef8 100644 (file)
--- a/util.c
+++ b/util.c
@@ -82,25 +82,55 @@ struct MBR_part_record {
   __u32 blocks_num;
 };
 
   __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];
 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];
   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)
 
 
 /* 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 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
 
 /*
  * 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)
 {
  */
 static int get_gpt_last_partition_end(int fd, unsigned long long *endofpart)
 {

+       struct GPT gpt;

        unsigned char buf[512];
        unsigned char buf[512];

-       __u64 *buf64;

        unsigned char empty_gpt_entry[16]= {0};
        struct GPT_part_entry *part;
        unsigned long long curr_part_end;
        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;
 
 
        *endofpart = 0;
 

+       BUILD_BUG_ON(sizeof(gpt) != 512);

        /* read GPT header */
        lseek(fd, 512, SEEK_SET);
        /* 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 */
                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*/
 
        /* Check GPT signature*/

-       buf64 = (__u64*)buf;
-       if (buf64[0] != GPT_SIGNATURE_MAGIC)
+       if (gpt.magic != GPT_SIGNATURE_MAGIC)

                return -1;
 
        /* sanity checks */
                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 */
                /* 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;
                }
                        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)
 {
  */
 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;
        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;
 
 
        *endofpart = 0;
 

+       BUILD_BUG_ON(sizeof(boot_sect) != 512);

        /* read MBR */
        lseek(fd, 0, 0);
        /* 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 */
                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 */
                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 */
 
                for (part_nr=0; part_nr < MBR_PARTITIONS; part_nr++) {
                        /* check for GPT type */