BSD 2 development

[unix-history] / .ref-BSD-1 / ex-1.1 / patchd.c

/*
* patchd symbol value [ file ]
*
* Like a db ! but works separate i/d.
*/
long    geto(), getsym(), itol();
char    *file;
struct  header {
       int     magic;
       int     txt_size;
       int     data_size;
       int     bss_size;
       int     sym_size;
       int     entry_loc;
       int     unused;
       int     no_reloc;
} header;

struct  nl {
       char    name[8];
       int     typ;
       int     *val;
} *nlp;

int     *initbrk;

main(argc, argv)
       int argc;
       char *argv[];
{
       long iaddr, addr;
       int value, word;
       int i;

       if (argc != 3 && argc != 4) {
               write(2, "Usage: patchd symbol value [ file ]\n", 36);
               exit(1);
       }
       close(0);
       file = argc == 4 ? argv[3] : "a.out";
       if (open(file, 2) < 0) {
               perror(file);
               exit(1);
       }
       value = geto(argv[2]);
       seek(0, 0, 0);
       if (read(0, &header, sizeof header) != sizeof header)
               goto oops;
       if (header.magic < 0407 || header.magic > 0411) {
               perror(file, "Not object file");
               exit(1);
       }
       addr = iaddr = getsym(argv[1]) + 16;
       switch (header.magic) {

       case 0407:      /* Non-shared */
               /* Just skip past header */
               break;

       case 0410:      /* Shared */
               /* Round to 4kW boundary */
               addr -= ((header.txt_size + 8191) &~ 8191) - header.txt_size;
               break;

       case 0411:      /* Separate i/d */
               addr += header.txt_size;
               break;

       }
       if (lseek(0, addr, 0)) {
seekerr:
               Perror(file, "Seek failed");
               exit(1);
       }
       if (read(0, &word, 2) != 2)
               goto oops;
       if (lseek(0, addr, 0))
               goto seekerr;
       if (write(0, &value, 2) != 2)
               goto oops;
       printf("Was %o now %o\n", word, value);
       exit(1);
oops:
       perror(file);
       exit(1);
}

long
geto(cp)
       char *cp;
{
       long i;

       for (i = 0; *cp >= '0' && *cp <= '7'; i = (i << 3) | *cp++ - '0')
               continue;
       if (*cp) {
               write(2, "Bad number.\n", 12);
               exit(1);
       }
       return (i);
}

Perror(cp, dp)
       char *cp, *dp;
{
       extern int errno;
       extern char *sys_errlist[];

       errno = 0;
       sys_errlist[0] = dp;
       perror(cp);
}

long
getsym(cp)
       char *cp;
{
       static char symbol[8];
       int i, j, n;

       seek(0, sizeof header, 0);
       lseek(0, 0, header.txt_size, 1);
       lseek(0, 0, header.data_size, 1);
       for (i = 0, j = 0; i < 8; i++) {
               symbol[i] = cp[j];
               if (cp[j])
                       j++;
       }
       initbrk = sbrk(0);
       n = ldiv(0, header.sym_size, 12);
       if (n == 0) {
               Perror(file, "No name list");
               exit (1);
       }
       nlp = sbrk(n * 12);
       if (read(0, nlp, n * 12) != n * 12) {
               Perror(file, "Error reading");
               exit (1);
       }
       for (i = 0; i < n; i++) {
               for (j = 0; j < 8; j++)
                       if (nlp->name[j] != symbol[j])
                               break;
               if (j == 8)
                       break;
               nlp++;
       }
       if (i == n) {
               Perror(cp, "Symbol not found");
               exit(1);
       }
       j = nlp->typ & 037;
       if (j > 4)
               j = 1;
       if (j == 0 && nlp->val)
               j = 5;
       if (!(nlp->typ&040) || j != 3) {
               Perror(cp, "Inappropriate symbol");
               exit(1);
       }
       return (itol(0, nlp->val));
}