mtd: check for Seama magic early when fixing MD5

This avoid long (and unneeded) process of reading all data in case of
running on MTD not containig Seama entity.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>

diff --git a/package/system/mtd/src/seama.c b/package/system/mtd/src/seama.c
index b0c8bf3d0d6f90d88fd76fdbc8477d8022c90a28..8894883c26680d42adb5f67563342e80b6ecdcdb 100644 (file)
--- a/package/system/mtd/src/seama.c
+++ b/package/system/mtd/src/seama.c
@@ -53,7 +53,7 @@ ssize_t pwrite(int fd, const void *buf, size_t count, off_t offset);
 int
 seama_fix_md5(char *buf, size_t len)
 {
-       struct seama_hdr *shdr;
+       struct seama_hdr *shdr = (struct seama_hdr *) buf;
        char *data;
        size_t msize;
        size_t isize;
@@ -64,12 +64,6 @@ seama_fix_md5(char *buf, size_t len)
        if (len < sizeof(struct seama_hdr))
                return -1;
 
-       shdr = (struct seama_hdr *) buf;
-       if (shdr->magic != htonl(SEAMA_MAGIC)) {
-               fprintf(stderr, "no SEAMA header found\n");
-               return -1;
-       }
-
        isize = ntohl(shdr->size);
        msize = ntohs(shdr->metasize);
        if (isize == 0) {
@@ -115,9 +109,11 @@ int
 mtd_fixseama(const char *mtd, size_t offset)
 {
        int fd;
+       char *first_block;
        char *buf;
        ssize_t res;
        size_t block_offset;
+       struct seama_hdr *shdr;
 
        if (quiet < 2)
                fprintf(stderr, "Trying to fix SEAMA header in %s at 0x%x...\n",
@@ -138,6 +134,24 @@ mtd_fixseama(const char *mtd, size_t offset)
                exit(1);
        }
 
+       first_block = malloc(erasesize);
+       if (!first_block) {
+               perror("malloc");
+               exit(1);
+       }
+
+       res = pread(fd, first_block, erasesize, block_offset);
+       if (res != erasesize) {
+               perror("pread");
+               exit(1);
+       }
+
+       shdr = (struct seama_hdr *)first_block;
+       if (shdr->magic != htonl(SEAMA_MAGIC)) {
+               fprintf(stderr, "No SEAMA header found\n");
+               return -1;
+       }
+
        buf = malloc(mtdsize);
        if (!buf) {
                perror("malloc");