root/fs/exec.c

/* */

DEFINITIONS

1. core_dump
2. sys_uselib
3. create_tables
4. count
5. copy_strings
6. change_ldt
7. read_omagic
8. do_execve

   1 /*
   2  *  linux/fs/exec.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6 
   7 /*
   8  * #!-checking implemented by tytso.
   9  */
  10 
  11 /*
  12  * Demand-loading implemented 01.12.91 - no need to read anything but
  13  * the header into memory. The inode of the executable is put into
  14  * "current->executable", and page faults do the actual loading. Clean.
  15  *
  16  * Once more I can proudly say that linux stood up to being changed: it
  17  * was less than 2 hours work to get demand-loading completely implemented.
  18  */
  19 
  20 #include <linux/fs.h>
  21 #include <linux/sched.h>
  22 #include <linux/kernel.h>
  23 #include <linux/mm.h>
  24 #include <linux/a.out.h>
  25 #include <linux/errno.h>
  26 #include <linux/signal.h>
  27 #include <linux/string.h>
  28 #include <linux/stat.h>
  29 #include <linux/fcntl.h>
  30 #include <linux/ptrace.h>
  31 #include <linux/user.h>
  32 
  33 #include <asm/segment.h>
  34 
  35 extern int sys_exit(int exit_code);
  36 extern int sys_close(int fd);
  37 
  38 /*
  39  * MAX_ARG_PAGES defines the number of pages allocated for arguments
  40  * and envelope for the new program. 32 should suffice, this gives
  41  * a maximum env+arg of 128kB !
  42  */
  43 #define MAX_ARG_PAGES 32
  44 
  45 /*
  46  * These are the only things you should do on a core-file: use only these
  47  * macros to write out all the necessary info.
  48  */
  49 #define DUMP_WRITE(addr,nr) \
  50 while (file.f_op->write(inode,&file,(char *)(addr),(nr)) != (nr)) goto close_coredump
  51 
  52 #define DUMP_SEEK(offset) \
  53 if (file.f_op->lseek) { \
  54         if (file.f_op->lseek(inode,&file,(offset),0) != (offset)) \
  55                 goto close_coredump; \
  56 } else file.f_pos = (offset)            
  57 
  58 /*
  59  * Routine writes a core dump image in the current directory.
  60  * Currently only a stub-function.
  61  *
  62  * Note that setuid/setgid files won't make a core-dump if the uid/gid
  63  * changed due to the set[u|g]id. It's enforced by the "current->dumpable"
  64  * field, which also makes sure the core-dumps won't be recursive if the
  65  * dumping of the process results in another error..
  66  */
  67 int core_dump(long signr, struct pt_regs * regs)
     /*  */
  68 {
  69         struct inode * inode = NULL;
  70         struct file file;
  71         unsigned short fs;
  72         int has_dumped = 0;
  73         register int dump_start, dump_size;
  74         struct user dump;
  75 
  76         if (!current->dumpable)
  77                 return 0;
  78         current->dumpable = 0;
  79 /* See if we have enough room to write the upage.  */
  80         if (current->rlim[RLIMIT_CORE].rlim_cur < PAGE_SIZE)
  81                 return 0;
  82         __asm__("mov %%fs,%0":"=r" (fs));
  83         __asm__("mov %0,%%fs"::"r" ((unsigned short) 0x10));
  84         if (open_namei("core",O_CREAT | O_WRONLY | O_TRUNC,0600,&inode,NULL)) {
  85                 inode = NULL;
  86                 goto end_coredump;
  87         }
  88         if (!S_ISREG(inode->i_mode))
  89                 goto end_coredump;
  90         if (!inode->i_op || !inode->i_op->default_file_ops)
  91                 goto end_coredump;
  92         file.f_mode = 3;
  93         file.f_flags = 0;
  94         file.f_count = 1;
  95         file.f_inode = inode;
  96         file.f_pos = 0;
  97         file.f_reada = 0;
  98         file.f_op = inode->i_op->default_file_ops;
  99         if (file.f_op->open)
 100                 if (file.f_op->open(inode,&file))
 101                         goto end_coredump;
 102         if (!file.f_op->write)
 103                 goto close_coredump;
 104         has_dumped = 1;
 105 /* changed the size calculations - should hopefully work better. lbt */
 106         dump.magic = CMAGIC;
 107         dump.start_code = 0;
 108         dump.start_stack = regs->esp & ~(PAGE_SIZE - 1);
 109         dump.u_tsize = ((unsigned long) current->end_code) >> 12;
 110         dump.u_dsize = ((unsigned long) (current->brk + (PAGE_SIZE-1))) >> 12;
 111         dump.u_dsize -= dump.u_tsize;
 112         dump.u_ssize = 0;
 113         if (dump.start_stack < TASK_SIZE)
 114                 dump.u_ssize = ((unsigned long) (TASK_SIZE - dump.start_stack)) >> 12;
 115 /* If the size of the dump file exceeds the rlimit, then see what would happen
 116    if we wrote the stack, but not the data area.  */
 117         if ((dump.u_dsize+dump.u_ssize+1) * PAGE_SIZE >
 118             current->rlim[RLIMIT_CORE].rlim_cur)
 119                 dump.u_dsize = 0;
 120 /* Make sure we have enough room to write the stack and data areas. */
 121         if ((dump.u_ssize+1) * PAGE_SIZE >
 122             current->rlim[RLIMIT_CORE].rlim_cur)
 123                 dump.u_ssize = 0;
 124         dump.u_comm = 0;
 125         dump.u_ar0 = (struct pt_regs *)(((int)(&dump.regs)) -((int)(&dump)));
 126         dump.signal = signr;
 127         dump.regs = *regs;
 128 /* Flag indicating the math stuff is valid. We don't support this for the
 129    soft-float routines yet */
 130         if (hard_math) {
 131                 if ((dump.u_fpvalid = current->used_math) != 0) {
 132                         if (last_task_used_math == current)
 133                                 __asm__("clts ; fnsave %0"::"m" (dump.i387));
 134                         else
 135                                 memcpy(&dump.i387,&current->tss.i387.hard,sizeof(dump.i387));
 136                 }
 137         } else {
 138                 /* we should dump the emulator state here, but we need to
 139                    convert it into standard 387 format first.. */
 140                 dump.u_fpvalid = 0;
 141         }
 142         __asm__("mov %0,%%fs"::"r" ((unsigned short) 0x10));
 143         DUMP_WRITE(&dump,sizeof(dump));
 144         DUMP_SEEK(sizeof(dump));
 145  /* Dump the task struct.  Not be used by gdb, but could be useful */
 146         DUMP_WRITE(current,sizeof(*current));
 147 /* Now dump all of the user data.  Include malloced stuff as well */
 148         DUMP_SEEK(PAGE_SIZE);
 149 /* now we start writing out the user space info */
 150         __asm__("mov %0,%%fs"::"r" ((unsigned short) 0x17));
 151 /* Dump the data area */
 152         if (dump.u_dsize != 0) {
 153                 dump_start = dump.u_tsize << 12;
 154                 dump_size = dump.u_dsize << 12;
 155                 DUMP_WRITE(dump_start,dump_size);
 156         };
 157 /* Now prepare to dump the stack area */
 158         if (dump.u_ssize != 0) {
 159                 dump_start = dump.start_stack;
 160                 dump_size = dump.u_ssize << 12;
 161                 DUMP_WRITE(dump_start,dump_size);
 162         };
 163 close_coredump:
 164         if (file.f_op->release)
 165                 file.f_op->release(inode,&file);
 166 end_coredump:
 167         __asm__("mov %0,%%fs"::"r" (fs));
 168         iput(inode);
 169         return has_dumped;
 170 }
 171 
 172 /*
 173  * Note that a shared library must be both readable and executable due to
 174  * security reasons.
 175  *
 176  * Also note that we take the address to load from from the file itself.
 177  */
 178 int sys_uselib(const char * library)
     /*  */
 179 {
 180 #define libnum  (current->numlibraries)
 181         struct inode * inode;
 182         struct buffer_head * bh;
 183         struct exec ex;
 184         int error;
 185 
 186         if (!library || get_limit(0x17) != TASK_SIZE)
 187                 return -EINVAL;
 188         if ((libnum >= MAX_SHARED_LIBS) || (libnum < 0))
 189                 return -EINVAL;
 190         error = namei(library,&inode);
 191         if (error)
 192                 return error;
 193         if (!inode->i_sb || !S_ISREG(inode->i_mode) || !permission(inode,MAY_READ)) {
 194                 iput(inode);
 195                 return -EACCES;
 196         }
 197         if (!(bh = bread(inode->i_dev,bmap(inode,0),inode->i_sb->s_blocksize))) {
 198                 iput(inode);
 199                 return -EACCES;
 200         }
 201         if (!IS_RDONLY(inode)) {
 202                 inode->i_atime = CURRENT_TIME;
 203                 inode->i_dirt = 1;
 204         }
 205         ex = *(struct exec *) bh->b_data;
 206         brelse(bh);
 207         if (N_MAGIC(ex) != ZMAGIC || ex.a_trsize || ex.a_drsize ||
 208                 ex.a_text+ex.a_data+ex.a_bss>0x3000000 ||
 209                 inode->i_size < ex.a_text+ex.a_data+ex.a_syms+N_TXTOFF(ex)) {
 210                 iput(inode);
 211                 return -ENOEXEC;
 212         }
 213         current->libraries[libnum].library = inode;
 214         current->libraries[libnum].start = ex.a_entry;
 215         current->libraries[libnum].length = (ex.a_data+ex.a_text+0xfff) & 0xfffff000;
 216         current->libraries[libnum].bss = (ex.a_bss+0xfff) & 0xfffff000;
 217 #if 0
 218         printk("Loaded library %d at %08x, length %08x\n",
 219                 libnum,
 220                 current->libraries[libnum].start,
 221                 current->libraries[libnum].length);
 222 #endif
 223         libnum++;
 224         return 0;
 225 #undef libnum
 226 }
 227 
 228 /*
 229  * create_tables() parses the env- and arg-strings in new user
 230  * memory and creates the pointer tables from them, and puts their
 231  * addresses on the "stack", returning the new stack pointer value.
 232  */
 233 static unsigned long * create_tables(char * p,int argc,int envc)
     /*  */
 234 {
 235         unsigned long *argv,*envp;
 236         unsigned long * sp;
 237 
 238         sp = (unsigned long *) (0xfffffffc & (unsigned long) p);
 239         sp -= envc+1;
 240         envp = sp;
 241         sp -= argc+1;
 242         argv = sp;
 243         put_fs_long((unsigned long)envp,--sp);
 244         put_fs_long((unsigned long)argv,--sp);
 245         put_fs_long((unsigned long)argc,--sp);
 246         while (argc-->0) {
 247                 put_fs_long((unsigned long) p,argv++);
 248                 while (get_fs_byte(p++)) /* nothing */ ;
 249         }
 250         put_fs_long(0,argv);
 251         while (envc-->0) {
 252                 put_fs_long((unsigned long) p,envp++);
 253                 while (get_fs_byte(p++)) /* nothing */ ;
 254         }
 255         put_fs_long(0,envp);
 256         return sp;
 257 }
 258 
 259 /*
 260  * count() counts the number of arguments/envelopes
 261  */
 262 static int count(char ** argv)
     /*  */
 263 {
 264         int i=0;
 265         char ** tmp;
 266 
 267         if ((tmp = argv) != 0)
 268                 while (get_fs_long((unsigned long *) (tmp++)))
 269                         i++;
 270 
 271         return i;
 272 }
 273 
 274 /*
 275  * 'copy_string()' copies argument/envelope strings from user
 276  * memory to free pages in kernel mem. These are in a format ready
 277  * to be put directly into the top of new user memory.
 278  *
 279  * Modified by TYT, 11/24/91 to add the from_kmem argument, which specifies
 280  * whether the string and the string array are from user or kernel segments:
 281  * 
 282  * from_kmem     argv *        argv **
 283  *    0          user space    user space
 284  *    1          kernel space  user space
 285  *    2          kernel space  kernel space
 286  * 
 287  * We do this by playing games with the fs segment register.  Since it
 288  * it is expensive to load a segment register, we try to avoid calling
 289  * set_fs() unless we absolutely have to.
 290  */
 291 static unsigned long copy_strings(int argc,char ** argv,unsigned long *page,
     /*  */
 292                 unsigned long p, int from_kmem)
 293 {
 294         char *tmp, *pag = NULL;
 295         int len, offset = 0;
 296         unsigned long old_fs, new_fs;
 297 
 298         if (!p)
 299                 return 0;       /* bullet-proofing */
 300         new_fs = get_ds();
 301         old_fs = get_fs();
 302         if (from_kmem==2)
 303                 set_fs(new_fs);
 304         while (argc-- > 0) {
 305                 if (from_kmem == 1)
 306                         set_fs(new_fs);
 307                 if (!(tmp = (char *)get_fs_long(((unsigned long *)argv)+argc)))
 308                         panic("argc is wrong");
 309                 if (from_kmem == 1)
 310                         set_fs(old_fs);
 311                 len=0;          /* remember zero-padding */
 312                 do {
 313                         len++;
 314                 } while (get_fs_byte(tmp++));
 315                 if (p < len) {  /* this shouldn't happen - 128kB */
 316                         set_fs(old_fs);
 317                         return 0;
 318                 }
 319                 while (len) {
 320                         --p; --tmp; --len;
 321                         if (--offset < 0) {
 322                                 offset = p % PAGE_SIZE;
 323                                 if (from_kmem==2)
 324                                         set_fs(old_fs);
 325                                 if (!(pag = (char *) page[p/PAGE_SIZE]) &&
 326                                     !(pag = (char *) page[p/PAGE_SIZE] =
 327                                       (unsigned long *) get_free_page(GFP_USER))) 
 328                                         return 0;
 329                                 if (from_kmem==2)
 330                                         set_fs(new_fs);
 331 
 332                         }
 333                         *(pag + offset) = get_fs_byte(tmp);
 334                 }
 335         }
 336         if (from_kmem==2)
 337                 set_fs(old_fs);
 338         return p;
 339 }
 340 
 341 static unsigned long change_ldt(unsigned long text_size,unsigned long * page)
     /*  */
 342 {
 343         unsigned long code_limit,data_limit,code_base,data_base;
 344         int i;
 345 
 346         code_limit = TASK_SIZE;
 347         data_limit = TASK_SIZE;
 348         code_base = data_base = 0;
 349         current->start_code = code_base;
 350         set_base(current->ldt[1],code_base);
 351         set_limit(current->ldt[1],code_limit);
 352         set_base(current->ldt[2],data_base);
 353         set_limit(current->ldt[2],data_limit);
 354 /* make sure fs points to the NEW data segment */
 355         __asm__("pushl $0x17\n\tpop %%fs"::);
 356         data_base += data_limit;
 357         for (i=MAX_ARG_PAGES-1 ; i>=0 ; i--) {
 358                 data_base -= PAGE_SIZE;
 359                 if (page[i])
 360                         put_dirty_page(current,page[i],data_base);
 361         }
 362         return data_limit;
 363 }
 364 
 365 static void read_omagic(struct inode *inode, int bytes)
     /*  */
 366 {
 367         struct buffer_head *bh;
 368         int n, blkno, blk = 0;
 369         char *dest = (char *) 0;
 370         unsigned int block_size;
 371 
 372         block_size = 1024;
 373         if (inode->i_sb)
 374                 block_size = inode->i_sb->s_blocksize;
 375         while (bytes > 0) {
 376                 if (!(blkno = bmap(inode, blk)))
 377                         sys_exit(-1);
 378                 if (!(bh = bread(inode->i_dev, blkno, block_size)))
 379                         sys_exit(-1);
 380                 n = (blk ? block_size : block_size - sizeof(struct exec));
 381                 if (bytes < n)
 382                         n = bytes;
 383 
 384                 memcpy_tofs(dest, (blk ? bh->b_data :
 385                                 bh->b_data + sizeof(struct exec)), n);
 386                 brelse(bh);
 387                 ++blk;
 388                 dest += n;
 389                 bytes -= n;
 390         }
 391         iput(inode);
 392         current->executable = NULL;
 393 }
 394 
 395 /*
 396  * 'do_execve()' executes a new program.
 397  *
 398  * NOTE! We leave 4MB free at the top of the data-area for a loadable
 399  * library.
 400  */
 401 int do_execve(unsigned long * eip,long tmp,char * filename,
     /*  */
 402         char ** argv, char ** envp)
 403 {
 404         struct inode * inode;
 405         struct buffer_head * bh;
 406         struct exec ex;
 407         unsigned long page[MAX_ARG_PAGES];
 408         int i,argc,envc;
 409         int e_uid, e_gid;
 410         int retval;
 411         int sh_bang = 0;
 412         unsigned long p=PAGE_SIZE*MAX_ARG_PAGES-4;
 413         int ch;
 414 
 415         if ((0xffff & eip[1]) != 0x000f)
 416                 panic("execve called from supervisor mode");
 417         for (i=0 ; i<MAX_ARG_PAGES ; i++)       /* clear page-table */
 418                 page[i]=0;
 419         retval = namei(filename,&inode);        /* get executable inode */
 420         if (retval)
 421                 return retval;
 422         argc = count(argv);
 423         envc = count(envp);
 424         
 425 restart_interp:
 426         if (!S_ISREG(inode->i_mode)) {  /* must be regular file */
 427                 retval = -EACCES;
 428                 goto exec_error2;
 429         }
 430         if (IS_NOEXEC(inode)) {         /* FS mustn't be mounted noexec */
 431                 retval = -EPERM;
 432                 goto exec_error2;
 433         }
 434         if (!inode->i_sb) {
 435                 retval = -EACCES;
 436                 goto exec_error2;
 437         }
 438         i = inode->i_mode;
 439         if (IS_NOSUID(inode) && (((i & S_ISUID) && inode->i_uid != current->
 440             euid) || ((i & S_ISGID) && inode->i_gid != current->egid)) &&
 441             !suser()) {
 442                 retval = -EPERM;
 443                 goto exec_error2;
 444         }
 445         /* make sure we don't let suid, sgid files be ptraced. */
 446         if (current->flags & PF_PTRACED) {
 447                 e_uid = current->euid;
 448                 e_gid = current->egid;
 449         } else {
 450                 e_uid = (i & S_ISUID) ? inode->i_uid : current->euid;
 451                 e_gid = (i & S_ISGID) ? inode->i_gid : current->egid;
 452         }
 453         if (current->euid == inode->i_uid)
 454                 i >>= 6;
 455         else if (in_group_p(inode->i_gid))
 456                 i >>= 3;
 457         if (!(i & 1) &&
 458             !((inode->i_mode & 0111) && suser())) {
 459                 retval = -EACCES;
 460                 goto exec_error2;
 461         }
 462         if (!(bh = bread(inode->i_dev,bmap(inode,0),inode->i_sb->s_blocksize))) {
 463                 retval = -EACCES;
 464                 goto exec_error2;
 465         }
 466         if (!IS_RDONLY(inode)) {
 467                 inode->i_atime = CURRENT_TIME;
 468                 inode->i_dirt = 1;
 469         }
 470         ex = *((struct exec *) bh->b_data);     /* read exec-header */
 471         if ((bh->b_data[0] == '#') && (bh->b_data[1] == '!') && (!sh_bang)) {
 472                 /*
 473                  * This section does the #! interpretation.
 474                  * Sorta complicated, but hopefully it will work.  -TYT
 475                  */
 476 
 477                 char buf[128], *cp, *interp, *i_name, *i_arg;
 478                 unsigned long old_fs;
 479 
 480                 strncpy(buf, bh->b_data+2, 127);
 481                 brelse(bh);
 482                 iput(inode);
 483                 buf[127] = '\0';
 484                 if ((cp = strchr(buf, '\n')) != NULL) {
 485                         *cp = '\0';
 486                         for (cp = buf; (*cp == ' ') || (*cp == '\t'); cp++);
 487                 }
 488                 if (!cp || *cp == '\0') {
 489                         retval = -ENOEXEC; /* No interpreter name found */
 490                         goto exec_error1;
 491                 }
 492                 interp = i_name = cp;
 493                 i_arg = 0;
 494                 for ( ; *cp && (*cp != ' ') && (*cp != '\t'); cp++) {
 495                         if (*cp == '/')
 496                                 i_name = cp+1;
 497                 }
 498                 if (*cp) {
 499                         *cp++ = '\0';
 500                         i_arg = cp;
 501                 }
 502                 /*
 503                  * OK, we've parsed out the interpreter name and
 504                  * (optional) argument.
 505                  */
 506                 if (sh_bang++ == 0) {
 507                         p = copy_strings(envc, envp, page, p, 0);
 508                         p = copy_strings(--argc, argv+1, page, p, 0);
 509                 }
 510                 /*
 511                  * Splice in (1) the interpreter's name for argv[0]
 512                  *           (2) (optional) argument to interpreter
 513                  *           (3) filename of shell script
 514                  *
 515                  * This is done in reverse order, because of how the
 516                  * user environment and arguments are stored.
 517                  */
 518                 p = copy_strings(1, &filename, page, p, 1);
 519                 argc++;
 520                 if (i_arg) {
 521                         p = copy_strings(1, &i_arg, page, p, 2);
 522                         argc++;
 523                 }
 524                 p = copy_strings(1, &i_name, page, p, 2);
 525                 argc++;
 526                 if (!p) {
 527                         retval = -ENOMEM;
 528                         goto exec_error1;
 529                 }
 530                 /*
 531                  * OK, now restart the process with the interpreter's inode.
 532                  */
 533                 old_fs = get_fs();
 534                 set_fs(get_ds());
 535                 retval = namei(interp,&inode);
 536                 set_fs(old_fs);
 537                 if (retval)
 538                         goto exec_error1;
 539                 goto restart_interp;
 540         }
 541         brelse(bh);
 542         if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC) ||
 543                 ex.a_trsize || ex.a_drsize ||
 544                 ex.a_text+ex.a_data+ex.a_bss>0x3000000 ||
 545                 inode->i_size < ex.a_text+ex.a_data+ex.a_syms+N_TXTOFF(ex)) {
 546                 retval = -ENOEXEC;
 547                 goto exec_error2;
 548         }
 549         if (N_TXTOFF(ex) != BLOCK_SIZE && N_MAGIC(ex) != OMAGIC) {
 550                 printk("%s: N_TXTOFF != BLOCK_SIZE. See a.out.h.", filename);
 551                 retval = -ENOEXEC;
 552                 goto exec_error2;
 553         }
 554         if (!sh_bang) {
 555                 p = copy_strings(envc,envp,page,p,0);
 556                 p = copy_strings(argc,argv,page,p,0);
 557                 if (!p) {
 558                         retval = -ENOMEM;
 559                         goto exec_error2;
 560                 }
 561         }
 562 /* OK, This is the point of no return */
 563         current->dumpable = 1;
 564         for (i=0; (ch = get_fs_byte(filename++)) != '\0';)
 565                 if (ch == '/')
 566                         i = 0;
 567                 else
 568                         if (i < 8)
 569                                 current->comm[i++] = ch;
 570         if (i < 8)
 571                 current->comm[i] = '\0';
 572         if (current->executable)
 573                 iput(current->executable);
 574         i = current->numlibraries;
 575         while (i-- > 0) {
 576                 iput(current->libraries[i].library);
 577                 current->libraries[i].library = NULL;
 578         }
 579         if (e_uid != current->euid || e_gid != current->egid ||
 580             !permission(inode,MAY_READ))
 581                 current->dumpable = 0;
 582         current->numlibraries = 0;
 583         current->executable = inode;
 584         current->signal = 0;
 585         for (i=0 ; i<32 ; i++) {
 586                 current->sigaction[i].sa_mask = 0;
 587                 current->sigaction[i].sa_flags = 0;
 588                 if (current->sigaction[i].sa_handler != SIG_IGN)
 589                         current->sigaction[i].sa_handler = NULL;
 590         }
 591         for (i=0 ; i<NR_OPEN ; i++)
 592                 if (FD_ISSET(i,&current->close_on_exec))
 593                         sys_close(i);
 594         FD_ZERO(&current->close_on_exec);
 595         clear_page_tables(current);
 596         if (last_task_used_math == current)
 597                 last_task_used_math = NULL;
 598         current->used_math = 0;
 599         p += change_ldt(ex.a_text,page);
 600         p -= MAX_ARG_PAGES*PAGE_SIZE;
 601         p = (unsigned long) create_tables((char *)p,argc,envc);
 602         current->brk = ex.a_bss +
 603                 (current->end_data = ex.a_data +
 604                 (current->end_code = ex.a_text));
 605         current->start_stack = p;
 606         current->rss = (TASK_SIZE - p + PAGE_SIZE-1) / PAGE_SIZE;
 607         current->suid = current->euid = e_uid;
 608         current->sgid = current->egid = e_gid;
 609         if (N_MAGIC(ex) == OMAGIC)
 610                 read_omagic(inode, ex.a_text+ex.a_data);
 611         eip[0] = ex.a_entry;            /* eip, magic happens :-) */
 612         eip[3] = p;                     /* stack pointer */
 613         if (current->flags & PF_PTRACED)
 614                 send_sig(SIGTRAP, current, 0);
 615         return 0;
 616 exec_error2:
 617         iput(inode);
 618 exec_error1:
 619         for (i=0 ; i<MAX_ARG_PAGES ; i++)
 620                 free_page(page[i]);
 621         return(retval);
 622 }

/* */