root/fs/exec.c

/* */

DEFINITIONS

1. core_dump
2. sys_uselib
3. create_tables
4. count
5. copy_strings
6. change_ldt
7. read_exec
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 /* struct user */
 144         DUMP_WRITE(&dump,sizeof(dump));
 145 /* name of the executable */
 146         DUMP_WRITE(current->comm,16);
 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 /* Finally dump the task struct.  Not be used by gdb, but could be useful */
 164         __asm__("mov %0,%%fs"::"r" ((unsigned short) 0x10));
 165         DUMP_WRITE(current,sizeof(*current));
 166 close_coredump:
 167         if (file.f_op->release)
 168                 file.f_op->release(inode,&file);
 169 end_coredump:
 170         __asm__("mov %0,%%fs"::"r" (fs));
 171         iput(inode);
 172         return has_dumped;
 173 }
 174 
 175 /*
 176  * Note that a shared library must be both readable and executable due to
 177  * security reasons.
 178  *
 179  * Also note that we take the address to load from from the file itself.
 180  */
 181 int sys_uselib(const char * library)
     /*  */
 182 {
 183 #define libnum  (current->numlibraries)
 184         struct inode * inode;
 185         struct buffer_head * bh;
 186         struct exec ex;
 187         unsigned long offset;
 188         int error;
 189 
 190         if (!library || get_limit(0x17) != TASK_SIZE)
 191                 return -EINVAL;
 192         if ((libnum >= MAX_SHARED_LIBS) || (libnum < 0))
 193                 return -EINVAL;
 194         error = namei(library,&inode);
 195         if (error)
 196                 return error;
 197         if (!inode->i_sb || !S_ISREG(inode->i_mode) || !permission(inode,MAY_READ)) {
 198                 iput(inode);
 199                 return -EACCES;
 200         }
 201         if (!inode->i_op || !inode->i_op->bmap) {
 202                 iput(inode);
 203                 return -ENOEXEC;
 204         }
 205         if (!(bh = bread(inode->i_dev,bmap(inode,0),inode->i_sb->s_blocksize))) {
 206                 iput(inode);
 207                 return -EACCES;
 208         }
 209         if (!IS_RDONLY(inode)) {
 210                 inode->i_atime = CURRENT_TIME;
 211                 inode->i_dirt = 1;
 212         }
 213         ex = *(struct exec *) bh->b_data;
 214         brelse(bh);
 215         if (N_MAGIC(ex) != ZMAGIC || ex.a_trsize ||
 216                 ex.a_drsize || ex.a_entry & 0xfff ||
 217                 inode->i_size < ex.a_text+ex.a_data+ex.a_syms+N_TXTOFF(ex)) {
 218                 iput(inode);
 219                 return -ENOEXEC;
 220         }
 221         current->libraries[libnum].library = inode;
 222         current->libraries[libnum].start = ex.a_entry;
 223         offset = (ex.a_data + ex.a_text + 0xfff) & 0xfffff000;
 224         current->libraries[libnum].length = offset;
 225         current->libraries[libnum].bss = ex.a_bss;
 226         offset += ex.a_entry;
 227         zeromap_page_range(offset, ex.a_bss, PAGE_COPY);
 228 #if 0
 229         printk("VFS: Loaded library %d at %08x, length %08x\n",
 230                 libnum,
 231                 current->libraries[libnum].start,
 232                 current->libraries[libnum].length);
 233 #endif
 234         libnum++;
 235         return 0;
 236 #undef libnum
 237 }
 238 
 239 /*
 240  * create_tables() parses the env- and arg-strings in new user
 241  * memory and creates the pointer tables from them, and puts their
 242  * addresses on the "stack", returning the new stack pointer value.
 243  */
 244 static unsigned long * create_tables(char * p,int argc,int envc)
     /*  */
 245 {
 246         unsigned long *argv,*envp;
 247         unsigned long * sp;
 248 
 249         sp = (unsigned long *) (0xfffffffc & (unsigned long) p);
 250         sp -= envc+1;
 251         envp = sp;
 252         sp -= argc+1;
 253         argv = sp;
 254         put_fs_long((unsigned long)envp,--sp);
 255         put_fs_long((unsigned long)argv,--sp);
 256         put_fs_long((unsigned long)argc,--sp);
 257         current->arg_start = (unsigned long) p;
 258         while (argc-->0) {
 259                 put_fs_long((unsigned long) p,argv++);
 260                 while (get_fs_byte(p++)) /* nothing */ ;
 261         }
 262         put_fs_long(0,argv);
 263         current->arg_end = current->env_start = (unsigned long) p;
 264         while (envc-->0) {
 265                 put_fs_long((unsigned long) p,envp++);
 266                 while (get_fs_byte(p++)) /* nothing */ ;
 267         }
 268         put_fs_long(0,envp);
 269         current->env_end = (unsigned long) p;
 270         return sp;
 271 }
 272 
 273 /*
 274  * count() counts the number of arguments/envelopes
 275  */
 276 static int count(char ** argv)
     /*  */
 277 {
 278         int i=0;
 279         char ** tmp;
 280 
 281         if ((tmp = argv) != 0)
 282                 while (get_fs_long((unsigned long *) (tmp++)))
 283                         i++;
 284 
 285         return i;
 286 }
 287 
 288 /*
 289  * 'copy_string()' copies argument/envelope strings from user
 290  * memory to free pages in kernel mem. These are in a format ready
 291  * to be put directly into the top of new user memory.
 292  *
 293  * Modified by TYT, 11/24/91 to add the from_kmem argument, which specifies
 294  * whether the string and the string array are from user or kernel segments:
 295  * 
 296  * from_kmem     argv *        argv **
 297  *    0          user space    user space
 298  *    1          kernel space  user space
 299  *    2          kernel space  kernel space
 300  * 
 301  * We do this by playing games with the fs segment register.  Since it
 302  * it is expensive to load a segment register, we try to avoid calling
 303  * set_fs() unless we absolutely have to.
 304  */
 305 static unsigned long copy_strings(int argc,char ** argv,unsigned long *page,
     /*  */
 306                 unsigned long p, int from_kmem)
 307 {
 308         char *tmp, *pag = NULL;
 309         int len, offset = 0;
 310         unsigned long old_fs, new_fs;
 311 
 312         if (!p)
 313                 return 0;       /* bullet-proofing */
 314         new_fs = get_ds();
 315         old_fs = get_fs();
 316         if (from_kmem==2)
 317                 set_fs(new_fs);
 318         while (argc-- > 0) {
 319                 if (from_kmem == 1)
 320                         set_fs(new_fs);
 321                 if (!(tmp = (char *)get_fs_long(((unsigned long *)argv)+argc)))
 322                         panic("VFS: argc is wrong");
 323                 if (from_kmem == 1)
 324                         set_fs(old_fs);
 325                 len=0;          /* remember zero-padding */
 326                 do {
 327                         len++;
 328                 } while (get_fs_byte(tmp++));
 329                 if (p < len) {  /* this shouldn't happen - 128kB */
 330                         set_fs(old_fs);
 331                         return 0;
 332                 }
 333                 while (len) {
 334                         --p; --tmp; --len;
 335                         if (--offset < 0) {
 336                                 offset = p % PAGE_SIZE;
 337                                 if (from_kmem==2)
 338                                         set_fs(old_fs);
 339                                 if (!(pag = (char *) page[p/PAGE_SIZE]) &&
 340                                     !(pag = (char *) page[p/PAGE_SIZE] =
 341                                       (unsigned long *) get_free_page(GFP_USER))) 
 342                                         return 0;
 343                                 if (from_kmem==2)
 344                                         set_fs(new_fs);
 345 
 346                         }
 347                         *(pag + offset) = get_fs_byte(tmp);
 348                 }
 349         }
 350         if (from_kmem==2)
 351                 set_fs(old_fs);
 352         return p;
 353 }
 354 
 355 static unsigned long change_ldt(unsigned long text_size,unsigned long * page)
     /*  */
 356 {
 357         unsigned long code_limit,data_limit,code_base,data_base;
 358         int i;
 359 
 360         code_limit = TASK_SIZE;
 361         data_limit = TASK_SIZE;
 362         code_base = data_base = 0;
 363         current->start_code = code_base;
 364         set_base(current->ldt[1],code_base);
 365         set_limit(current->ldt[1],code_limit);
 366         set_base(current->ldt[2],data_base);
 367         set_limit(current->ldt[2],data_limit);
 368 /* make sure fs points to the NEW data segment */
 369         __asm__("pushl $0x17\n\tpop %%fs"::);
 370         data_base += data_limit;
 371         for (i=MAX_ARG_PAGES-1 ; i>=0 ; i--) {
 372                 data_base -= PAGE_SIZE;
 373                 if (page[i])
 374                         put_dirty_page(current,page[i],data_base);
 375         }
 376         return data_limit;
 377 }
 378 
 379 /*
 380  * Read in the complete executable. This is used for "-N" files
 381  * that aren't on a block boundary, and for files on filesystems
 382  * without bmap support.
 383  */
 384 static int read_exec(struct inode *inode, unsigned long offset,
     /*  */
 385         char * addr, unsigned long count)
 386 {
 387         struct file file;
 388         int result = -ENOEXEC;
 389 
 390         if (!inode->i_op || !inode->i_op->default_file_ops)
 391                 goto end_readexec;
 392         file.f_mode = 1;
 393         file.f_flags = 0;
 394         file.f_count = 1;
 395         file.f_inode = inode;
 396         file.f_pos = 0;
 397         file.f_reada = 0;
 398         file.f_op = inode->i_op->default_file_ops;
 399         if (file.f_op->open)
 400                 if (file.f_op->open(inode,&file))
 401                         goto end_readexec;
 402         if (!file.f_op || !file.f_op->read)
 403                 goto close_readexec;
 404         if (file.f_op->lseek) {
 405                 if (file.f_op->lseek(inode,&file,offset,0) != offset)
 406                         goto close_readexec;
 407         } else
 408                 file.f_pos = offset;
 409         result = file.f_op->read(inode, &file, addr, count);
 410 close_readexec:
 411         if (file.f_op->release)
 412                 file.f_op->release(inode,&file);
 413 end_readexec:
 414         return result;
 415 }
 416 
 417 /*
 418  * 'do_execve()' executes a new program.
 419  *
 420  * NOTE! We leave 4MB free at the top of the data-area for a loadable
 421  * library.
 422  */
 423 int do_execve(unsigned long * eip,long tmp,char * filename,
     /*  */
 424         char ** argv, char ** envp)
 425 {
 426         struct inode * inode;
 427         char buf[128];
 428         unsigned long old_fs;
 429         struct exec ex;
 430         unsigned long page[MAX_ARG_PAGES];
 431         int i,argc,envc;
 432         int e_uid, e_gid;
 433         int retval;
 434         int sh_bang = 0;
 435         unsigned long p=PAGE_SIZE*MAX_ARG_PAGES-4;
 436         int ch;
 437 
 438         if ((0xffff & eip[1]) != 0x000f)
 439                 panic("VFS: execve called from supervisor mode");
 440         for (i=0 ; i<MAX_ARG_PAGES ; i++)       /* clear page-table */
 441                 page[i]=0;
 442         retval = namei(filename,&inode);        /* get executable inode */
 443         if (retval)
 444                 return retval;
 445         argc = count(argv);
 446         envc = count(envp);
 447         
 448 restart_interp:
 449         if (!S_ISREG(inode->i_mode)) {  /* must be regular file */
 450                 retval = -EACCES;
 451                 goto exec_error2;
 452         }
 453         if (IS_NOEXEC(inode)) {         /* FS mustn't be mounted noexec */
 454                 retval = -EPERM;
 455                 goto exec_error2;
 456         }
 457         if (!inode->i_sb) {
 458                 retval = -EACCES;
 459                 goto exec_error2;
 460         }
 461         i = inode->i_mode;
 462         if (IS_NOSUID(inode) && (((i & S_ISUID) && inode->i_uid != current->
 463             euid) || ((i & S_ISGID) && !in_group_p(inode->i_gid))) &&
 464             !suser()) {
 465                 retval = -EPERM;
 466                 goto exec_error2;
 467         }
 468         /* make sure we don't let suid, sgid files be ptraced. */
 469         if (current->flags & PF_PTRACED) {
 470                 e_uid = current->euid;
 471                 e_gid = current->egid;
 472         } else {
 473                 e_uid = (i & S_ISUID) ? inode->i_uid : current->euid;
 474                 e_gid = (i & S_ISGID) ? inode->i_gid : current->egid;
 475         }
 476         if (current->euid == inode->i_uid)
 477                 i >>= 6;
 478         else if (in_group_p(inode->i_gid))
 479                 i >>= 3;
 480         if (!(i & 1) &&
 481             !((inode->i_mode & 0111) && suser())) {
 482                 retval = -EACCES;
 483                 goto exec_error2;
 484         }
 485         memset(buf,0,sizeof(buf));
 486         old_fs = get_fs();
 487         set_fs(get_ds());
 488         retval = read_exec(inode,0,buf,128);
 489         set_fs(old_fs);
 490         if (retval < 0)
 491                 goto exec_error2;
 492         ex = *((struct exec *) buf);            /* exec-header */
 493         if ((buf[0] == '#') && (buf[1] == '!') && (!sh_bang)) {
 494                 /*
 495                  * This section does the #! interpretation.
 496                  * Sorta complicated, but hopefully it will work.  -TYT
 497                  */
 498 
 499                 char *cp, *interp, *i_name, *i_arg;
 500 
 501                 iput(inode);
 502                 buf[127] = '\0';
 503                 if ((cp = strchr(buf, '\n')) == NULL)
 504                         cp = buf+127;
 505                 *cp = '\0';
 506                 while (cp > buf) {
 507                         cp--;
 508                         if ((*cp == ' ') || (*cp == '\t'))
 509                                 *cp = '\0';
 510                         else
 511                                 break;
 512                 }
 513                 for (cp = buf+2; (*cp == ' ') || (*cp == '\t'); cp++);
 514                 if (!cp || *cp == '\0') {
 515                         retval = -ENOEXEC; /* No interpreter name found */
 516                         goto exec_error1;
 517                 }
 518                 interp = i_name = cp;
 519                 i_arg = 0;
 520                 for ( ; *cp && (*cp != ' ') && (*cp != '\t'); cp++) {
 521                         if (*cp == '/')
 522                                 i_name = cp+1;
 523                 }
 524                 while ((*cp == ' ') || (*cp == '\t'))
 525                         *cp++ = '\0';
 526                 if (*cp)
 527                         i_arg = cp;
 528                 /*
 529                  * OK, we've parsed out the interpreter name and
 530                  * (optional) argument.
 531                  */
 532                 if (sh_bang++ == 0) {
 533                         p = copy_strings(envc, envp, page, p, 0);
 534                         p = copy_strings(--argc, argv+1, page, p, 0);
 535                 }
 536                 /*
 537                  * Splice in (1) the interpreter's name for argv[0]
 538                  *           (2) (optional) argument to interpreter
 539                  *           (3) filename of shell script
 540                  *
 541                  * This is done in reverse order, because of how the
 542                  * user environment and arguments are stored.
 543                  */
 544                 p = copy_strings(1, &filename, page, p, 1);
 545                 argc++;
 546                 if (i_arg) {
 547                         p = copy_strings(1, &i_arg, page, p, 2);
 548                         argc++;
 549                 }
 550                 p = copy_strings(1, &i_name, page, p, 2);
 551                 argc++;
 552                 if (!p) {
 553                         retval = -E2BIG;
 554                         goto exec_error1;
 555                 }
 556                 /*
 557                  * OK, now restart the process with the interpreter's inode.
 558                  * Note that we use open_namei() as the name is now in kernel
 559                  * space, and we don't need to copy it.
 560                  */
 561                 retval = open_namei(interp,0,0,&inode,NULL);
 562                 if (retval)
 563                         goto exec_error1;
 564                 goto restart_interp;
 565         }
 566         if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC) ||
 567                 ex.a_trsize || ex.a_drsize ||
 568                 inode->i_size < ex.a_text+ex.a_data+ex.a_syms+N_TXTOFF(ex)) {
 569                 retval = -ENOEXEC;
 570                 goto exec_error2;
 571         }
 572         if (N_TXTOFF(ex) != BLOCK_SIZE && N_MAGIC(ex) != OMAGIC) {
 573                 printk("VFS: N_TXTOFF != BLOCK_SIZE. See a.out.h.");
 574                 retval = -ENOEXEC;
 575                 goto exec_error2;
 576         }
 577         if (!sh_bang) {
 578                 p = copy_strings(envc,envp,page,p,0);
 579                 p = copy_strings(argc,argv,page,p,0);
 580                 if (!p) {
 581                         retval = -E2BIG;
 582                         goto exec_error2;
 583                 }
 584         }
 585 /* OK, This is the point of no return */
 586         current->dumpable = 1;
 587         for (i=0; (ch = get_fs_byte(filename++)) != '\0';)
 588                 if (ch == '/')
 589                         i = 0;
 590                 else
 591                         if (i < 15)
 592                                 current->comm[i++] = ch;
 593         current->comm[i] = '\0';
 594         if (current->executable) {
 595                 iput(current->executable);
 596                 current->executable = NULL;
 597         }
 598         i = current->numlibraries;
 599         while (i-- > 0) {
 600                 iput(current->libraries[i].library);
 601                 current->libraries[i].library = NULL;
 602         }
 603         if (e_uid != current->euid || e_gid != current->egid ||
 604             !permission(inode,MAY_READ))
 605                 current->dumpable = 0;
 606         current->numlibraries = 0;
 607         current->signal = 0;
 608         for (i=0 ; i<32 ; i++) {
 609                 current->sigaction[i].sa_mask = 0;
 610                 current->sigaction[i].sa_flags = 0;
 611                 if (current->sigaction[i].sa_handler != SIG_IGN)
 612                         current->sigaction[i].sa_handler = NULL;
 613         }
 614         for (i=0 ; i<NR_OPEN ; i++)
 615                 if (FD_ISSET(i,&current->close_on_exec))
 616                         sys_close(i);
 617         FD_ZERO(&current->close_on_exec);
 618         clear_page_tables(current);
 619         if (last_task_used_math == current)
 620                 last_task_used_math = NULL;
 621         current->used_math = 0;
 622         p += change_ldt(ex.a_text,page);
 623         p -= MAX_ARG_PAGES*PAGE_SIZE;
 624         p = (unsigned long) create_tables((char *)p,argc,envc);
 625         current->brk = ex.a_bss +
 626                 (current->end_data = ex.a_data +
 627                 (current->end_code = ex.a_text));
 628         current->start_stack = p;
 629         current->rss = (TASK_SIZE - p + PAGE_SIZE-1) / PAGE_SIZE;
 630         current->suid = current->euid = e_uid;
 631         current->sgid = current->egid = e_gid;
 632         if (N_MAGIC(ex) == OMAGIC) {
 633                 read_exec(inode, 32, (char *) 0, ex.a_text+ex.a_data);
 634                 iput(inode);
 635         } else if (!inode->i_op || !inode->i_op->bmap) {
 636                 read_exec(inode, 1024, (char *) 0, ex.a_text+ex.a_data);
 637                 iput(inode);
 638         } else
 639                 current->executable = inode;
 640         zeromap_page_range((ex.a_text + ex.a_data + 0xfff) & 0xfffff000,ex.a_bss, PAGE_COPY);
 641         eip[0] = ex.a_entry;            /* eip, magic happens :-) */
 642         eip[3] = p;                     /* stack pointer */
 643         if (current->flags & PF_PTRACED)
 644                 send_sig(SIGTRAP, current, 0);
 645         return 0;
 646 exec_error2:
 647         iput(inode);
 648 exec_error1:
 649         for (i=0 ; i<MAX_ARG_PAGES ; i++)
 650                 free_page(page[i]);
 651         return(retval);
 652 }

/* */