to get offset of structure for assembly code

offset.c

#include <sys/types.h>
#include <sys/stat.h>
#include <stddef.h>
#include <time.h>

// the following are reported by :  man 2 stat
struct the_stat {
    dev_t     st_dev;         /* ID of device containing file */
    ino_t     st_ino;         /* inode number */
    mode_t    st_mode;        /* protection */
    nlink_t   st_nlink;       /* number of hard links */
    uid_t     st_uid;         /* user ID of owner */
    gid_t     st_gid;         /* group ID of owner */
    dev_t     st_rdev;        /* device ID (if special file) */
    off_t     st_size;        /* total size, in bytes */
    blksize_t st_blksize;     /* blocksize for filesystem I/O */
    blkcnt_t  st_blocks;      /* number of 512B blocks allocated */

    /* Since Linux 2.6, the kernel supports nanosecond
       precision for the following timestamp fields.
       For the details before Linux 2.6, see NOTES. */

    struct timespec st_atim;  /* time of last access */
    struct timespec st_mtim;  /* time of last modification */
    struct timespec st_ctim;  /* time of last status change */

#define st_atime st_atim.tv_sec      /* Backward compatibility */
#define st_mtime st_mtim.tv_sec
#define st_ctime st_ctim.tv_sec
};



int
main(int argc, char *argv[])
{
  printf("\n");
  printf("\n(%d) (%u)     dev_t     st_dev;             ", sizeof(dev_t), offsetof(struct stat, st_dev));
  printf("\n(%d) (%u)     ino_t     st_ino;             ", sizeof(ino_t), offsetof(struct stat, st_ino));
  printf("\n(%d) (%u)     mode_t    st_mode;            ", sizeof(mode_t), offsetof(struct stat, st_mode));
  printf("\n(%d) (%u)     nlink_t   st_nlink;           ", sizeof(nlink_t), offsetof(struct stat, st_nlink));
  printf("\n(%d) (%u)     uid_t     st_uid;             ", sizeof(uid_t), offsetof(struct stat, st_uid));
  printf("\n(%d) (%u)     gid_t     st_gid;             ", sizeof(gid_t), offsetof(struct stat, st_gid));
  printf("\n(%d) (%u)     dev_t     st_rdev;            ", sizeof(dev_t), offsetof(struct stat, st_rdev));
  printf("\n(%d) (%u)     off_t     st_size;            ", sizeof(off_t), offsetof(struct stat, st_size));
  printf("\n(%d) (%u)     blksize_t st_blksize;         ", sizeof(blksize_t), offsetof(struct stat, st_blksize));
  printf("\n(%d) (%u)     blkcnt_t  st_blocks;          ", sizeof(blkcnt_t), offsetof(struct stat, st_blocks));
  printf("\n");                                       
  printf("\n(%d) (%u)     __time_t tv_sec;              ", sizeof(__time_t), offsetof(struct timespec, tv_sec));
  printf("\n(%d) (%u)     __syscall_slong_t tv_nsec;    ", sizeof(__syscall_slong_t), offsetof(struct timespec, tv_nsec));
  printf("\n");
}

// the following is example result :

/*
(8) (0)     dev_t     st_dev;             
(8) (8)     ino_t     st_ino;             
(4) (24)     mode_t    st_mode;            
(8) (16)     nlink_t   st_nlink;           
(4) (28)     uid_t     st_uid;             
(4) (32)     gid_t     st_gid;             
(8) (40)     dev_t     st_rdev;            
(8) (48)     off_t     st_size;            
(8) (56)     blksize_t st_blksize;         
(8) (64)     blkcnt_t  st_blocks;          

(8) (0)     __time_t tv_sec;              
(8) (8)     __syscall_slong_t tv_nsec;
*/

another useful comment from #forth

proteusguy:
one comment though - you need to make sure that you build
the code with the same parameters as your kernel was built with
regarding alignment and padding or else this perfectly good result
could be perfectly incompatible with your kernel. So best to check
what options the kernel is using. However I would anticipate that
kernel devs would (hopefully) ensure their structure aligned on
natural boundaries already. But if you find these offsets don't work
then that's the next thing to check.

@xieyuheng maybe you need __attribute__ ((packed)) for you structure fields for avoiding padding.
https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-g_t_0040code_007bpacked_007d-variable-attribute-3331