tools: kwboot: Replace fstat()+st_size by lseek()+SEEK_END

fstat()'s st_size works only for regular files. lseek() with SEEK_END works
also for block or MTD devices. This replacement allows kwboot to load
kwbimage from /dev/mtd0 for booting another device over /dev/ttyS0.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Marek Behún <marek.behun@nic.cz>

diff --git a/tools/kwboot.c b/tools/kwboot.c
index 9f2dd2d..b697d3b 100644 (file)
--- a/tools/kwboot.c
+++ b/tools/kwboot.c
@@ -1591,8 +1591,8 @@ static void *
 kwboot_read_image(const char *path, size_t *size, size_t reserve)
 {
        int rc, fd;
-       struct stat st;
        void *img;
+       off_t len;
        off_t tot;
 
        rc = -1;
@@ -1602,31 +1602,34 @@ kwboot_read_image(const char *path, size_t *size, size_t reserve)
        if (fd < 0)
                goto out;
 
-       rc = fstat(fd, &st);
-       if (rc)
+       len = lseek(fd, 0, SEEK_END);
+       if (len == (off_t)-1)
+               goto out;
+
+       if (lseek(fd, 0, SEEK_SET) == (off_t)-1)
                goto out;
 
-       img = malloc(st.st_size + reserve);
+       img = malloc(len + reserve);
        if (!img)
                goto out;
 
        tot = 0;
-       while (tot < st.st_size) {
-               ssize_t rd = read(fd, img + tot, st.st_size - tot);
+       while (tot < len) {
+               ssize_t rd = read(fd, img + tot, len - tot);
 
                if (rd < 0)
                        goto out;
 
                tot += rd;
 
-               if (!rd && tot < st.st_size) {
+               if (!rd && tot < len) {
                        errno = EIO;
                        goto out;
                }
        }
 
        rc = 0;
-       *size = st.st_size;
+       *size = len;
 out:
        if (rc && img) {
                free(img);