How can I extract the kernel size from uImage?

In case anyone ever needs the same optimization, here is what I added to the file "common/cmd_bootm.c".

This code adds another command to u-boot responsible to update the value of nand_img_siz, the parameter used to copy a determined number of bytes from the NAND to the RAM. Feel free to modify it. Don't forget to call the new commnad (imzise) before calling bootm.

int do_imsize(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
{
   return image_size(0x82000000);
}

static int image_size(ulong addr)
{
   void *hdr=(void*)addr;
   int size;
   char str[29]; /* 29 = strlen("setenv nand_img_siz 0x500000")+'\0' */

   run_command("nand read.i 0x82000000 ${nand_src_addr} 0x10",0);

   size=image_get_data_size(hdr)+0x40; /* 64 bytes to complete uImage's real size */

   if(size>0x500000) {
      size=0x500000;
      printf("ERROR: An error occurred while reading the image's size... Loading default value\n");
   }

   sprintf(str,"setenv nand_img_siz 0x%X",size);
   run_command(str,0);

   return 0;
}

U_BOOT_CMD(
   imsize, CONFIG_SYS_MAXARGS, 1, do_imsize,
   "update the environment variable nand_img_siz with the image's exact size",
   ""
);