fs/exec.c

   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  * Demand-loading implemented 01.12.91 - no need to read anything but
  12  * the header into memory. The inode of the executable is put into
  13  * "current->executable", and page faults do the actual loading. Clean.
  14  *
  15  * Once more I can proudly say that linux stood up to being changed: it
  16  * was less than 2 hours work to get demand-loading completely implemented.
  17  *
  18  * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
  19  * current->executable is only used by the procfs.  This allows a dispatch
  20  * table to check for several different types  of binary formats.  We keep
  21  * trying until we recognize the file or we run out of supported binary
  22  * formats.
  23  */
  24
  25 #include <linux/config.h>
  26 #include <linux/slab.h>
  27 #include <linux/file.h>
  28 #include <linux/mman.h>
  29 #include <linux/a.out.h>
  30 #include <linux/stat.h>
  31 #include <linux/fcntl.h>
  32 #include <linux/smp_lock.h>
  33 #include <linux/init.h>
  34
  35 #include <asm/uaccess.h>
  36 #include <asm/pgtable.h>
  37 #include <asm/mmu_context.h>
  38
  39 #ifdef CONFIG_KMOD
  40 #include <linux/kmod.h>
  41 #endif
  42
  43 /*
  44  * Here are the actual binaries that will be accepted:
  45  * add more with "register_binfmt()" if using modules...
  46  *
  47  * These are defined again for the 'real' modules if you are using a
  48  * module definition for these routines.
  49  */
  50
  51 static struct linux_binfmt *formats = (struct linux_binfmt *) NULL;
  52
  53 void __init binfmt_setup(void)
  54 {
  55 #ifdef CONFIG_BINFMT_MISC
  56         init_misc_binfmt();
  57 #endif
  58
  59 #ifdef CONFIG_BINFMT_ELF
  60         init_elf_binfmt();
  61 #endif
  62
  63 #ifdef CONFIG_BINFMT_ELF32
  64         init_elf32_binfmt();
  65 #endif
  66
  67 #ifdef CONFIG_BINFMT_AOUT
  68         init_aout_binfmt();
  69 #endif
  70
  71 #ifdef CONFIG_BINFMT_AOUT32
  72         init_aout32_binfmt();
  73 #endif
  74
  75 #ifdef CONFIG_BINFMT_JAVA
  76         init_java_binfmt();
  77 #endif
  78
  79 #ifdef CONFIG_BINFMT_EM86
  80         init_em86_binfmt();
  81 #endif
  82
  83         /* This cannot be configured out of the kernel */
  84         init_script_binfmt();
  85 }
  86
  87 int register_binfmt(struct linux_binfmt * fmt)
  88 {
  89         struct linux_binfmt ** tmp = &formats;
  90
  91         if (!fmt)
  92                 return -EINVAL;
  93         if (fmt->next)
  94                 return -EBUSY;
  95         while (*tmp) {
  96                 if (fmt == *tmp)
  97                         return -EBUSY;
  98                 tmp = &(*tmp)->next;
  99         }
 100         fmt->next = formats;
 101         formats = fmt;
 102         return 0;
 103 }
 104
 105 #ifdef CONFIG_MODULES
 106 int unregister_binfmt(struct linux_binfmt * fmt)
 107 {
 108         struct linux_binfmt ** tmp = &formats;
 109
 110         while (*tmp) {
 111                 if (fmt == *tmp) {
 112                         *tmp = fmt->next;
 113                         return 0;
 114                 }
 115                 tmp = &(*tmp)->next;
 116         }
 117         return -EINVAL;
 118 }
 119 #endif  /* CONFIG_MODULES */
 120
 121 /* N.B. Error returns must be < 0 */
 122 int open_dentry(struct dentry * dentry, int mode)
 123 {
 124         struct inode * inode = dentry->d_inode;
 125         struct file * f;
 126         int fd, error;
 127
 128         error = -EINVAL;
 129         if (!inode->i_op || !inode->i_op->default_file_ops)
 130                 goto out;
 131         fd = get_unused_fd();
 132         if (fd >= 0) {
 133                 error = -ENFILE;
 134                 f = get_empty_filp();
 135                 if (!f)
 136                         goto out_fd;
 137                 f->f_flags = mode;
 138                 f->f_mode = (mode+1) & O_ACCMODE;
 139                 f->f_dentry = dentry;
 140                 f->f_pos = 0;
 141                 f->f_reada = 0;
 142                 f->f_op = inode->i_op->default_file_ops;
 143                 if (f->f_op->open) {
 144                         error = f->f_op->open(inode,f);
 145                         if (error)
 146                                 goto out_filp;
 147                 }
 148                 fd_install(fd, f);
 149                 dget(dentry);
 150         }
 151         return fd;
 152
 153 out_filp:
 154         if (error > 0)
 155                 error = -EIO;
 156         put_filp(f);
 157 out_fd:
 158         put_unused_fd(fd);
 159 out:
 160         return error;
 161 }
 162
 163 /*
 164  * Note that a shared library must be both readable and executable due to
 165  * security reasons.
 166  *
 167  * Also note that we take the address to load from from the file itself.
 168  */
 169 asmlinkage int sys_uselib(const char * library)
 170 {
 171         int fd, retval;
 172         struct file * file;
 173         struct linux_binfmt * fmt;
 174
 175         lock_kernel();
 176         fd = sys_open(library, 0, 0);
 177         retval = fd;
 178         if (fd < 0)
 179                 goto out;
 180         file = fget(fd);
 181         retval = -ENOEXEC;
 182         if (file && file->f_dentry && file->f_op && file->f_op->read) {
 183                 for (fmt = formats ; fmt ; fmt = fmt->next) {
 184                         int (*fn)(int) = fmt->load_shlib;
 185                         if (!fn)
 186                                 continue;
 187                         /* N.B. Should use file instead of fd */
 188                         retval = fn(fd);
 189                         if (retval != -ENOEXEC)
 190                                 break;
 191                 }
 192         }
 193         fput(file);
 194         sys_close(fd);
 195 out:
 196         unlock_kernel();
 197         return retval;
 198 }
 199
 200 /*
 201  * count() counts the number of arguments/envelopes
 202  */
 203 static int count(char ** argv)
 204 {
 205         int i = 0;
 206
 207         if (argv != NULL) {
 208                 for (;;) {
 209                         char * p;
 210                         int error;
 211
 212                         error = get_user(p,argv);
 213                         if (error)
 214                                 return error;
 215                         if (!p)
 216                                 break;
 217                         argv++;
 218                         i++;
 219                 }
 220         }
 221         return i;
 222 }
 223
 224 /*
 225  * 'copy_string()' copies argument/envelope strings from user
 226  * memory to free pages in kernel mem. These are in a format ready
 227  * to be put directly into the top of new user memory.
 228  *
 229  * Modified by TYT, 11/24/91 to add the from_kmem argument, which specifies
 230  * whether the string and the string array are from user or kernel segments:
 231  *
 232  * from_kmem     argv *        argv **
 233  *    0          user space    user space
 234  *    1          kernel space  user space
 235  *    2          kernel space  kernel space
 236  *
 237  * We do this by playing games with the fs segment register.  Since it
 238  * is expensive to load a segment register, we try to avoid calling
 239  * set_fs() unless we absolutely have to.
 240  */
 241 unsigned long copy_strings(int argc,char ** argv,unsigned long *page,
 242                 unsigned long p, int from_kmem)
 243 {
 244         char *str;
 245         mm_segment_t old_fs;
 246
 247         if (!p)
 248                 return 0;       /* bullet-proofing */
 249         old_fs = get_fs();
 250         if (from_kmem==2)
 251                 set_fs(KERNEL_DS);
 252         while (argc-- > 0) {
 253                 int len;
 254                 unsigned long pos;
 255
 256                 if (from_kmem == 1)
 257                         set_fs(KERNEL_DS);
 258                 get_user(str, argv+argc);
 259                 if (!str)
 260                         panic("VFS: argc is wrong");
 261                 if (from_kmem == 1)
 262                         set_fs(old_fs);
 263                 len = strlen_user(str); /* includes the '\0' */
 264                 if (p < len) {  /* this shouldn't happen - 128kB */
 265                         set_fs(old_fs);
 266                         return 0;
 267                 }
 268                 p -= len;
 269                 pos = p;
 270                 while (len) {
 271                         char *pag;
 272                         int offset, bytes_to_copy;
 273
 274                         offset = pos % PAGE_SIZE;
 275                         if (!(pag = (char *) page[pos/PAGE_SIZE]) &&
 276                             !(pag = (char *) page[pos/PAGE_SIZE] =
 277                               (unsigned long *) get_free_page(GFP_USER))) {
 278                                 if (from_kmem==2)
 279                                         set_fs(old_fs);
 280                                 return 0;
 281                         }
 282                         bytes_to_copy = PAGE_SIZE - offset;
 283                         if (bytes_to_copy > len)
 284                                 bytes_to_copy = len;
 285                         copy_from_user(pag + offset, str, bytes_to_copy);
 286                         pos += bytes_to_copy;
 287                         str += bytes_to_copy;
 288                         len -= bytes_to_copy;
 289                 }
 290         }
 291         if (from_kmem==2)
 292                 set_fs(old_fs);
 293         return p;
 294 }
 295
 296 unsigned long setup_arg_pages(unsigned long p, struct linux_binprm * bprm)
 297 {
 298         unsigned long stack_base;
 299         struct vm_area_struct *mpnt;
 300         int i;
 301
 302         stack_base = STACK_TOP - MAX_ARG_PAGES*PAGE_SIZE;
 303
 304         p += stack_base;
 305         if (bprm->loader)
 306                 bprm->loader += stack_base;
 307         bprm->exec += stack_base;
 308
 309         mpnt = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
 310         if (mpnt) {
 311                 mpnt->vm_mm = current->mm;
 312                 mpnt->vm_start = PAGE_MASK & (unsigned long) p;
 313                 mpnt->vm_end = STACK_TOP;
 314                 mpnt->vm_page_prot = PAGE_COPY;
 315                 mpnt->vm_flags = VM_STACK_FLAGS;
 316                 mpnt->vm_ops = NULL;
 317                 mpnt->vm_offset = 0;
 318                 mpnt->vm_file = NULL;
 319                 mpnt->vm_pte = 0;
 320                 insert_vm_struct(current->mm, mpnt);
 321                 current->mm->total_vm = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 322         }
 323
 324         for (i = 0 ; i < MAX_ARG_PAGES ; i++) {
 325                 if (bprm->page[i]) {
 326                         current->mm->rss++;
 327                         put_dirty_page(current,bprm->page[i],stack_base);
 328                 }
 329                 stack_base += PAGE_SIZE;
 330         }
 331         return p;
 332 }
 333
 334 /*
 335  * Read in the complete executable. This is used for "-N" files
 336  * that aren't on a block boundary, and for files on filesystems
 337  * without bmap support.
 338  */
 339 int read_exec(struct dentry *dentry, unsigned long offset,
 340         char * addr, unsigned long count, int to_kmem)
 341 {
 342         struct file file;
 343         struct inode * inode = dentry->d_inode;
 344         int result = -ENOEXEC;
 345
 346         if (!inode->i_op || !inode->i_op->default_file_ops)
 347                 goto end_readexec;
 348         if (init_private_file(&file, dentry, 1))
 349                 goto end_readexec;
 350         if (!file.f_op->read)
 351                 goto close_readexec;
 352         if (file.f_op->llseek) {
 353                 if (file.f_op->llseek(&file,offset,0) != offset)
 354                         goto close_readexec;
 355         } else
 356                 file.f_pos = offset;
 357         if (to_kmem) {
 358                 mm_segment_t old_fs = get_fs();
 359                 set_fs(get_ds());
 360                 result = file.f_op->read(&file, addr, count, &file.f_pos);
 361                 set_fs(old_fs);
 362         } else {
 363                 result = verify_area(VERIFY_WRITE, addr, count);
 364                 if (result)
 365                         goto close_readexec;
 366                 result = file.f_op->read(&file, addr, count, &file.f_pos);
 367         }
 368 close_readexec:
 369         if (file.f_op->release)
 370                 file.f_op->release(inode,&file);
 371 end_readexec:
 372         return result;
 373 }
 374
 375 static int exec_mmap(void)
 376 {
 377         struct mm_struct * mm, * old_mm;
 378         int retval, nr;
 379
 380         if (atomic_read(&current->mm->count) == 1) {
 381                 flush_cache_mm(current->mm);
 382                 mm_release();
 383                 release_segments(current->mm);
 384                 exit_mmap(current->mm);
 385                 flush_tlb_mm(current->mm);
 386                 return 0;
 387         }
 388
 389         retval = -ENOMEM;
 390         mm = mm_alloc();
 391         if (!mm)
 392                 goto fail_nomem;
 393
 394         mm->cpu_vm_mask = (1UL << smp_processor_id());
 395         mm->total_vm = 0;
 396         mm->rss = 0;
 397         /*
 398          * Make sure we have a private ldt if needed ...
 399          */
 400         nr = current->tarray_ptr - &task[0];
 401         copy_segments(nr, current, mm);
 402
 403         old_mm = current->mm;
 404         current->mm = mm;
 405         retval = new_page_tables(current);
 406         if (retval)
 407                 goto fail_restore;
 408         activate_context(current);
 409         up(&mm->mmap_sem);
 410         mm_release();
 411         mmput(old_mm);
 412         return 0;
 413
 414         /*
 415          * Failure ... restore the prior mm_struct.
 416          */
 417 fail_restore:
 418         current->mm = old_mm;
 419         /* restore the ldt for this task */
 420         copy_segments(nr, current, NULL);
 421         release_segments(mm);
 422         kmem_cache_free(mm_cachep, mm);
 423
 424 fail_nomem:
 425         return retval;
 426 }
 427
 428 /*
 429  * This function makes sure the current process has its own signal table,
 430  * so that flush_signal_handlers can later reset the handlers without
 431  * disturbing other processes.  (Other processes might share the signal
 432  * table via the CLONE_SIGHAND option to clone().)
 433  */
 434
 435 static inline int make_private_signals(void)
 436 {
 437         struct signal_struct * newsig;
 438
 439         if (atomic_read(&current->sig->count) <= 1)
 440                 return 0;
 441         newsig = kmalloc(sizeof(*newsig), GFP_KERNEL);
 442         if (newsig == NULL)
 443                 return -ENOMEM;
 444         spin_lock_init(&newsig->siglock);
 445         atomic_set(&newsig->count, 1);
 446         memcpy(newsig->action, current->sig->action, sizeof(newsig->action));
 447         current->sig = newsig;
 448         return 0;
 449 }
 450
 451 /*
 452  * If make_private_signals() made a copy of the signal table, decrement the
 453  * refcount of the original table, and free it if necessary.
 454  * We don't do that in make_private_signals() so that we can back off
 455  * in flush_old_exec() if an error occurs after calling make_private_signals().
 456  */
 457
 458 static inline void release_old_signals(struct signal_struct * oldsig)
 459 {
 460         if (current->sig == oldsig)
 461                 return;
 462         if (atomic_dec_and_test(&oldsig->count))
 463                 kfree(oldsig);
 464 }
 465
 466 /*
 467  * These functions flushes out all traces of the currently running executable
 468  * so that a new one can be started
 469  */
 470
 471 static inline void flush_old_files(struct files_struct * files)
 472 {
 473         unsigned long j;
 474
 475         j = 0;
 476         for (;;) {
 477                 unsigned long set, i;
 478
 479                 i = j * __NFDBITS;
 480                 if (i >= files->max_fds)
 481                         break;
 482                 set = files->close_on_exec.fds_bits[j];
 483                 files->close_on_exec.fds_bits[j] = 0;
 484                 j++;
 485                 for ( ; set ; i++,set >>= 1) {
 486                         if (set & 1)
 487                                 sys_close(i);
 488                 }
 489         }
 490 }
 491
 492 int flush_old_exec(struct linux_binprm * bprm)
 493 {
 494         char * name;
 495         int i, ch, retval;
 496         struct signal_struct * oldsig;
 497
 498         /*
 499          * Make sure we have a private signal table
 500          */
 501         oldsig = current->sig;
 502         retval = make_private_signals();
 503         if (retval) goto flush_failed;
 504
 505         /*
 506          * Release all of the old mmap stuff
 507          */
 508         retval = exec_mmap();
 509         if (retval) goto mmap_failed;
 510
 511         /* This is the point of no return */
 512         release_old_signals(oldsig);
 513
 514         if (current->euid == current->uid && current->egid == current->gid)
 515                 current->dumpable = 1;
 516         name = bprm->filename;
 517         for (i=0; (ch = *(name++)) != '\0';) {
 518                 if (ch == '/')
 519                         i = 0;
 520                 else
 521                         if (i < 15)
 522                                 current->comm[i++] = ch;
 523         }
 524         current->comm[i] = '\0';
 525
 526         flush_thread();
 527
 528         if (bprm->e_uid != current->euid || bprm->e_gid != current->egid ||
 529             permission(bprm->dentry->d_inode,MAY_READ))
 530                 current->dumpable = 0;
 531
 532         flush_signal_handlers(current);
 533         flush_old_files(current->files);
 534
 535         return 0;
 536
 537 mmap_failed:
 538         if (current->sig != oldsig)
 539                 kfree(current->sig);
 540 flush_failed:
 541         current->sig = oldsig;
 542         return retval;
 543 }
 544
 545 /*
 546  * We mustn't allow tracing of suid binaries, unless
 547  * the tracer has the capability to trace anything..
 548  */
 549 static inline int must_not_trace_exec(struct task_struct * p)
 550 {
 551         return (p->flags & PF_PTRACED) && !cap_raised(p->p_pptr->cap_effective, CAP_SYS_PTRACE);
 552 }
 553
 554 /*
 555  * Fill the binprm structure from the inode.
 556  * Check permissions, then read the first 512 bytes
 557  */
 558 int prepare_binprm(struct linux_binprm *bprm)
 559 {
 560         int mode;
 561         int retval,id_change,cap_raised;
 562         struct inode * inode = bprm->dentry->d_inode;
 563
 564         mode = inode->i_mode;
 565         if (!S_ISREG(mode))                     /* must be regular file */
 566                 return -EACCES;
 567         if (!(mode & 0111))                     /* with at least _one_ execute bit set */
 568                 return -EACCES;
 569         if (IS_NOEXEC(inode))                   /* FS mustn't be mounted noexec */
 570                 return -EACCES;
 571         if (!inode->i_sb)
 572                 return -EACCES;
 573         if ((retval = permission(inode, MAY_EXEC)) != 0)
 574                 return retval;
 575         /* better not execute files which are being written to */
 576         if (inode->i_writecount > 0)
 577                 return -ETXTBSY;
 578
 579         bprm->e_uid = current->euid;
 580         bprm->e_gid = current->egid;
 581         id_change = cap_raised = 0;
 582
 583         /* Set-uid? */
 584         if (mode & S_ISUID) {
 585                 bprm->e_uid = inode->i_uid;
 586                 if (bprm->e_uid != current->euid)
 587                         id_change = 1;
 588         }
 589
 590         /* Set-gid? */
 591         /*
 592          * If setgid is set but no group execute bit then this
 593          * is a candidate for mandatory locking, not a setgid
 594          * executable.
 595          */
 596         if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
 597                 bprm->e_gid = inode->i_gid;
 598                 if (!in_group_p(bprm->e_gid))
 599                         id_change = 1;
 600         }
 601
 602         /* We don't have VFS support for capabilities yet */
 603         cap_clear(bprm->cap_inheritable);
 604         cap_clear(bprm->cap_permitted);
 605         cap_clear(bprm->cap_effective);
 606
 607         /*  To support inheritance of root-permissions and suid-root
 608          *  executables under compatibility mode, we raise the
 609          *  effective and inherited bitmasks of the executable file
 610          *  (translation: we set the executable "capability dumb" and
 611          *  set the allowed set to maximum). We don't set any forced
 612          *  bits.
 613          *
 614          *  If only the real uid is 0, we only raise the inheritable
 615          *  bitmask of the executable file (translation: we set the
 616          *  allowed set to maximum and the application to "capability
 617          *  smart").
 618          */
 619
 620         if (!issecure(SECURE_NOROOT)) {
 621                 if (bprm->e_uid == 0 || current->uid == 0)
 622                         cap_set_full(bprm->cap_inheritable);
 623                 if (bprm->e_uid == 0)
 624                         cap_set_full(bprm->cap_effective);
 625         }
 626
 627         /* Only if pP' is _not_ a subset of pP, do we consider there
 628          * has been a capability related "change of capability".  In
 629          * such cases, we need to check that the elevation of
 630          * privilege does not go against other system constraints.
 631          * The new Permitted set is defined below -- see (***). */
 632         {
 633                 kernel_cap_t working =
 634                         cap_combine(bprm->cap_permitted,
 635                                     cap_intersect(bprm->cap_inheritable,
 636                                                   current->cap_inheritable));
 637                 if (!cap_issubset(working, current->cap_permitted)) {
 638                         cap_raised = 1;
 639                 }
 640         }
 641
 642         if (id_change || cap_raised) {
 643                 /* We can't suid-execute if we're sharing parts of the executable */
 644                 /* or if we're being traced (or if suid execs are not allowed)    */
 645                 /* (current->mm->count > 1 is ok, as we'll get a new mm anyway)   */
 646                 if (IS_NOSUID(inode)
 647                     || must_not_trace_exec(current)
 648                     || (atomic_read(&current->fs->count) > 1)
 649                     || (atomic_read(&current->sig->count) > 1)
 650                     || (atomic_read(&current->files->count) > 1)) {
 651                         if (id_change && !capable(CAP_SETUID))
 652                                 return -EPERM;
 653                         if (cap_raised && !capable(CAP_SETPCAP))
 654                                 return -EPERM;
 655                 }
 656         }
 657
 658         memset(bprm->buf,0,sizeof(bprm->buf));
 659         return read_exec(bprm->dentry,0,bprm->buf,128,1);
 660 }
 661
 662 /*
 663  * This function is used to produce the new IDs and capabilities
 664  * from the old ones and the file's capabilities.
 665  *
 666  * The formula used for evolving capabilities is:
 667  *
 668  *       pI' = pI
 669  * (***) pP' = fP | (fI & pI)
 670  *       pE' = pP' & fE          [NB. fE is 0 or ~0]
 671  *
 672  * I=Inheritable, P=Permitted, E=Effective // p=process, f=file
 673  * ' indicates post-exec().
 674  */
 675
 676 void compute_creds(struct linux_binprm *bprm)
 677 {
 678         int new_permitted = cap_t(bprm->cap_permitted) |
 679                 (cap_t(bprm->cap_inheritable) &
 680                  cap_t(current->cap_inheritable));
 681
 682         /* For init, we want to retain the capabilities set
 683          * in the init_task struct. Thus we skip the usual
 684          * capability rules */
 685         if (current->pid != 1) {
 686                 cap_t(current->cap_permitted) = new_permitted;
 687                 cap_t(current->cap_effective) = new_permitted &
 688                                                 cap_t(bprm->cap_effective);
 689         }
 690
 691         /* AUD: Audit candidate if current->cap_effective is set */
 692
 693         current->suid = current->euid = current->fsuid = bprm->e_uid;
 694         current->sgid = current->egid = current->fsgid = bprm->e_gid;
 695         if (current->euid != current->uid || current->egid != current->gid ||
 696             !cap_issubset(new_permitted, current->cap_permitted))
 697                 current->dumpable = 0;
 698 }
 699
 700
 701 void remove_arg_zero(struct linux_binprm *bprm)
 702 {
 703         if (bprm->argc) {
 704                 unsigned long offset;
 705                 char * page;
 706                 offset = bprm->p % PAGE_SIZE;
 707                 page = (char*)bprm->page[bprm->p/PAGE_SIZE];
 708                 while(bprm->p++,*(page+offset++))
 709                         if(offset==PAGE_SIZE){
 710                                 offset=0;
 711                                 page = (char*)bprm->page[bprm->p/PAGE_SIZE];
 712                         }
 713                 bprm->argc--;
 714         }
 715 }
 716
 717 /*
 718  * cycle the list of binary formats handler, until one recognizes the image
 719  */
 720 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
 721 {
 722         int try,retval=0;
 723         struct linux_binfmt *fmt;
 724 #ifdef __alpha__
 725         /* handle /sbin/loader.. */
 726         {
 727             struct exec * eh = (struct exec *) bprm->buf;
 728             struct linux_binprm bprm_loader;
 729
 730             if (!bprm->loader && eh->fh.f_magic == 0x183 &&
 731                 (eh->fh.f_flags & 0x3000) == 0x3000)
 732             {
 733                 int i;
 734                 char * dynloader[] = { "/sbin/loader" };
 735                 struct dentry * dentry;
 736
 737                 dput(bprm->dentry);
 738                 bprm->dentry = NULL;
 739
 740                 bprm_loader.p = PAGE_SIZE*MAX_ARG_PAGES-sizeof(void *);
 741                 for (i=0 ; i<MAX_ARG_PAGES ; i++)       /* clear page-table */
 742                     bprm_loader.page[i] = 0;
 743
 744                 dentry = open_namei(dynloader[0], 0, 0);
 745                 retval = PTR_ERR(dentry);
 746                 if (IS_ERR(dentry))
 747                         return retval;
 748                 bprm->dentry = dentry;
 749                 bprm->loader = bprm_loader.p;
 750                 retval = prepare_binprm(bprm);
 751                 if (retval<0)
 752                         return retval;
 753                 /* should call search_binary_handler recursively here,
 754                    but it does not matter */
 755             }
 756         }
 757 #endif
 758         for (try=0; try<2; try++) {
 759                 for (fmt = formats ; fmt ; fmt = fmt->next) {
 760                         int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
 761                         if (!fn)
 762                                 continue;
 763                         retval = fn(bprm, regs);
 764                         if (retval >= 0) {
 765                                 if (bprm->dentry)
 766                                         dput(bprm->dentry);
 767                                 bprm->dentry = NULL;
 768                                 current->did_exec = 1;
 769                                 return retval;
 770                         }
 771                         if (retval != -ENOEXEC)
 772                                 break;
 773                         if (!bprm->dentry) /* We don't have the dentry anymore */
 774                                 return retval;
 775                 }
 776                 if (retval != -ENOEXEC) {
 777                         break;
 778 #ifdef CONFIG_KMOD
 779                 }else{
 780 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
 781                         char modname[20];
 782                         if (printable(bprm->buf[0]) &&
 783                             printable(bprm->buf[1]) &&
 784                             printable(bprm->buf[2]) &&
 785                             printable(bprm->buf[3]))
 786                                 break; /* -ENOEXEC */
 787                         sprintf(modname, "binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
 788                         request_module(modname);
 789 #endif
 790                 }
 791         }
 792         return retval;
 793 }
 794
 795
 796 /*
 797  * sys_execve() executes a new program.
 798  */
 799 int do_execve(char * filename, char ** argv, char ** envp, struct pt_regs * regs)
 800 {
 801         struct linux_binprm bprm;
 802         struct dentry * dentry;
 803         int retval;
 804         int i;
 805
 806         bprm.p = PAGE_SIZE*MAX_ARG_PAGES-sizeof(void *);
 807         for (i=0 ; i<MAX_ARG_PAGES ; i++)       /* clear page-table */
 808                 bprm.page[i] = 0;
 809
 810         dentry = open_namei(filename, 0, 0);
 811         retval = PTR_ERR(dentry);
 812         if (IS_ERR(dentry))
 813                 return retval;
 814
 815         bprm.dentry = dentry;
 816         bprm.filename = filename;
 817         bprm.sh_bang = 0;
 818         bprm.java = 0;
 819         bprm.loader = 0;
 820         bprm.exec = 0;
 821         if ((bprm.argc = count(argv)) < 0) {
 822                 dput(dentry);
 823                 return bprm.argc;
 824         }
 825
 826         if ((bprm.envc = count(envp)) < 0) {
 827                 dput(dentry);
 828                 return bprm.envc;
 829         }
 830
 831         retval = prepare_binprm(&bprm);
 832
 833         if (retval >= 0) {
 834                 bprm.p = copy_strings(1, &bprm.filename, bprm.page, bprm.p, 2);
 835                 bprm.exec = bprm.p;
 836                 bprm.p = copy_strings(bprm.envc,envp,bprm.page,bprm.p,0);
 837                 bprm.p = copy_strings(bprm.argc,argv,bprm.page,bprm.p,0);
 838                 if (!bprm.p)
 839                         retval = -E2BIG;
 840         }
 841
 842         if (retval >= 0)
 843                 retval = search_binary_handler(&bprm,regs);
 844         if (retval >= 0)
 845                 /* execve success */
 846                 return retval;
 847
 848         /* Something went wrong, return the inode and free the argument pages*/
 849         if (bprm.dentry)
 850                 dput(bprm.dentry);
 851
 852         for (i=0 ; i<MAX_ARG_PAGES ; i++)
 853                 free_page(bprm.page[i]);
 854
 855         return retval;
 856 }