src/unexaix.c

   1 /* Dump an executable image.
   2    Copyright (C) 1985, 1986, 1987, 1988, 1999, 2001, 2002, 2003, 2004,
   3                  2005, 2006, 2007  Free Software Foundation, Inc.
   4
   5 This file is part of GNU Emacs.
   6
   7 GNU Emacs is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 2, or (at your option)
  10 any later version.
  11
  12 GNU Emacs is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GNU Emacs; see the file COPYING.  If not, write to
  19 the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  20 Boston, MA 02110-1301, USA.
  21
  22 In other words, you are welcome to use, share and improve this program.
  23 You are forbidden to forbid anyone else to use, share and improve
  24 what you give them.   Help stamp out software-hoarding!  */
  25
  26
  27 /* Originally based on the COFF unexec.c by Spencer W. Thomas.
  28  *
  29  * Subsequently hacked on by
  30  * Bill Mann <Bill_Man@praxisint.com>
  31  * Andrew Vignaux <Andrew.Vignaux@comp.vuw.ac.nz>
  32  * Mike Sperber <sperber@informatik.uni-tuebingen.de>
  33  *
  34  * Synopsis:
  35  *      unexec (new_name, a_name, data_start, bss_start, entry_address)
  36  *      char *new_name, *a_name;
  37  *      unsigned data_start, bss_start, entry_address;
  38  *
  39  * Takes a snapshot of the program and makes an a.out format file in the
  40  * file named by the string argument new_name.
  41  * If a_name is non-NULL, the symbol table will be taken from the given file.
  42  * On some machines, an existing a_name file is required.
  43  *
  44  * data_start and entry_address are ignored.
  45  *
  46  * bss_start indicates how much of the data segment is to be saved in the
  47  * a.out file and restored when the program is executed.  It gives the lowest
  48  * unsaved address, and is rounded up to a page boundary.  The default when 0
  49  * is given assumes that the entire data segment is to be stored, including
  50  * the previous data and bss as well as any additional storage allocated with
  51  * sbrk(2).
  52  *
  53  */
  54
  55 #ifndef emacs
  56 #define PERROR(arg) perror (arg); return -1
  57 #else
  58 #include <config.h>
  59 #define PERROR(file) report_error (file, new)
  60 #endif
  61
  62 #include <a.out.h>
  63 /* Define getpagesize () if the system does not.
  64    Note that this may depend on symbols defined in a.out.h
  65  */
  66 #include "getpagesize.h"
  67
  68 #include <sys/types.h>
  69 #include <stdio.h>
  70 #include <sys/stat.h>
  71 #include <errno.h>
  72 #include <unistd.h>
  73 #include <fcntl.h>
  74
  75 extern char *start_of_text (void);              /* Start of text */
  76 extern char *start_of_data (void);              /* Start of initialized data */
  77
  78 extern int _data;
  79 extern int _text;
  80
  81 #include <filehdr.h>
  82 #include <aouthdr.h>
  83 #include <scnhdr.h>
  84 #include <syms.h>
  85
  86 static struct filehdr f_hdr;            /* File header */
  87 static struct aouthdr f_ohdr;           /* Optional file header (a.out) */
  88 static long bias;                       /* Bias to add for growth */
  89 static long lnnoptr;                    /* Pointer to line-number info within file */
  90
  91 static long text_scnptr;
  92 static long data_scnptr;
  93 #define ALIGN(val, pwr) (((val) + ((1L<<(pwr))-1)) & ~((1L<<(pwr))-1))
  94 static long load_scnptr;
  95 static long orig_load_scnptr;
  96 static long orig_data_scnptr;
  97 static int unrelocate_symbols (int, int, char *, char *);
  98
  99 #ifndef MAX_SECTIONS
 100 #define MAX_SECTIONS    10
 101 #endif
 102
 103 static int adjust_lnnoptrs (int, int, char *);
 104
 105 static int pagemask;
 106
 107 /* Correct an int which is the bit pattern of a pointer to a byte
 108    into an int which is the number of a byte.
 109    This is a no-op on ordinary machines, but not on all.  */
 110
 111 #ifndef ADDR_CORRECT   /* Let m-*.h files override this definition */
 112 #define ADDR_CORRECT(x) ((char *)(x) - (char*)0)
 113 #endif
 114
 115 #ifdef emacs
 116 #include "lisp.h"
 117
 118 static void
 119 report_error (char *file, int fd)
 120 {
 121   if (fd)
 122     close (fd);
 123   report_file_error ("Cannot unexec", Fcons (build_string (file), Qnil));
 124 }
 125 #endif /* emacs */
 126
 127 #define ERROR0(msg) report_error_1 (new, msg, 0, 0); return -1
 128 #define ERROR1(msg,x) report_error_1 (new, msg, x, 0); return -1
 129 #define ERROR2(msg,x,y) report_error_1 (new, msg, x, y); return -1
 130
 131 static void
 132 report_error_1 (int fd, char *msg, int a1, int a2)
 133 {
 134   close (fd);
 135 #ifdef emacs
 136   error (msg, a1, a2);
 137 #else
 138   fprintf (stderr, msg, a1, a2);
 139   fprintf (stderr, "\n");
 140 #endif
 141 }
 142
 143 static int make_hdr (int, int, unsigned, unsigned, unsigned, char *, char *);
 144 static void mark_x (char *);
 145 static int copy_text_and_data (int);
 146 static int copy_sym (int, int, char *, char *);
 147 static void write_segment (int, char *, char *);
 148 \f
 149 /* ****************************************************************
 150  * unexec
 151  *
 152  * driving logic.
 153  */
 154 int unexec (char *new_name, char *a_name,
 155             unsigned data_start,
 156             unsigned bss_start,
 157             unsigned entry_address)
 158 {
 159   int new = -1, a_out = -1;
 160
 161   if (a_name && (a_out = open (a_name, O_RDONLY)) < 0)
 162     {
 163       PERROR (a_name);
 164     }
 165   if ((new = creat (new_name, 0666)) < 0)
 166     {
 167       PERROR (new_name);
 168     }
 169   if (make_hdr (new, a_out,
 170                 data_start, bss_start,
 171                 entry_address,
 172                 a_name, new_name) < 0
 173       || copy_text_and_data (new) < 0
 174       || copy_sym (new, a_out, a_name, new_name) < 0
 175       || adjust_lnnoptrs (new, a_out, new_name) < 0
 176       || unrelocate_symbols (new, a_out, a_name, new_name) < 0)
 177     {
 178       close (new);
 179       return -1;
 180     }
 181
 182   close (new);
 183   if (a_out >= 0)
 184     close (a_out);
 185   mark_x (new_name);
 186   return 0;
 187 }
 188
 189 /* ****************************************************************
 190  * make_hdr
 191  *
 192  * Make the header in the new a.out from the header in core.
 193  * Modify the text and data sizes.
 194  */
 195 static int
 196 make_hdr (int new, int a_out,
 197           unsigned data_start, unsigned bss_start,
 198           unsigned entry_address,
 199           char *a_name, char *new_name)
 200 {
 201   int scns;
 202   unsigned int bss_end;
 203
 204   struct scnhdr section[MAX_SECTIONS];
 205   struct scnhdr * f_thdr;               /* Text section header */
 206   struct scnhdr * f_dhdr;               /* Data section header */
 207   struct scnhdr * f_bhdr;               /* Bss section header */
 208   struct scnhdr * f_lhdr;               /* Loader section header */
 209   struct scnhdr * f_tchdr;              /* Typechk section header */
 210   struct scnhdr * f_dbhdr;              /* Debug section header */
 211   struct scnhdr * f_xhdr;               /* Except section header */
 212
 213   load_scnptr = orig_load_scnptr = lnnoptr = 0;
 214   pagemask = getpagesize () - 1;
 215
 216   /* Adjust text/data boundary. */
 217   data_start = (long) start_of_data ();
 218   data_start = ADDR_CORRECT (data_start);
 219
 220   data_start = data_start & ~pagemask; /* (Down) to page boundary. */
 221
 222   bss_end = ADDR_CORRECT (sbrk (0)) + pagemask;
 223   bss_end &= ~ pagemask;
 224   /* Adjust data/bss boundary. */
 225   if (bss_start != 0)
 226     {
 227       bss_start = (ADDR_CORRECT (bss_start) + pagemask);
 228       /* (Up) to page bdry. */
 229       bss_start &= ~ pagemask;
 230       if (bss_start > bss_end)
 231         {
 232           ERROR1 ("unexec: Specified bss_start (%u) is past end of program",
 233                   bss_start);
 234         }
 235     }
 236   else
 237     bss_start = bss_end;
 238
 239   if (data_start > bss_start)   /* Can't have negative data size. */
 240     {
 241       ERROR2 ("unexec: data_start (%u) can't be greater than bss_start (%u)",
 242               data_start, bss_start);
 243     }
 244
 245   /* Salvage as much info from the existing file as possible */
 246   f_thdr = NULL; f_dhdr = NULL; f_bhdr = NULL;
 247   f_lhdr = NULL; f_tchdr = NULL; f_dbhdr = NULL; f_xhdr = NULL;
 248   if (a_out >= 0)
 249     {
 250       if (read (a_out, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
 251         {
 252           PERROR (a_name);
 253         }
 254       if (f_hdr.f_opthdr > 0)
 255         {
 256           if (read (a_out, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
 257             {
 258               PERROR (a_name);
 259             }
 260         }
 261       if (f_hdr.f_nscns > MAX_SECTIONS)
 262         {
 263           ERROR0 ("unexec: too many section headers -- increase MAX_SECTIONS");
 264         }
 265       /* Loop through section headers */
 266       for (scns = 0; scns < f_hdr.f_nscns; scns++) {
 267         struct scnhdr *s = &section[scns];
 268         if (read (a_out, s, sizeof (*s)) != sizeof (*s))
 269           {
 270             PERROR (a_name);
 271           }
 272
 273 #define CHECK_SCNHDR(ptr, name, flags) \
 274   if (strcmp(s->s_name, name) == 0) { \
 275     if (s->s_flags != flags) { \
 276       fprintf(stderr, "unexec: %lx flags where %x expected in %s section.\n", \
 277               (unsigned long)s->s_flags, flags, name); \
 278     } \
 279     if (ptr) { \
 280       fprintf(stderr, "unexec: duplicate section header for section %s.\n", \
 281               name); \
 282     } \
 283     ptr = s; \
 284   }
 285         CHECK_SCNHDR(f_thdr, _TEXT, STYP_TEXT);
 286         CHECK_SCNHDR(f_dhdr, _DATA, STYP_DATA);
 287         CHECK_SCNHDR(f_bhdr, _BSS, STYP_BSS);
 288         CHECK_SCNHDR(f_lhdr, _LOADER, STYP_LOADER);
 289         CHECK_SCNHDR(f_dbhdr, _DEBUG,  STYP_DEBUG);
 290         CHECK_SCNHDR(f_tchdr, _TYPCHK,  STYP_TYPCHK);
 291         CHECK_SCNHDR(f_xhdr, _EXCEPT,  STYP_EXCEPT);
 292       }
 293
 294       if (f_thdr == 0)
 295         {
 296           ERROR1 ("unexec: couldn't find \"%s\" section", (int) _TEXT);
 297         }
 298       if (f_dhdr == 0)
 299         {
 300           ERROR1 ("unexec: couldn't find \"%s\" section", (int) _DATA);
 301         }
 302       if (f_bhdr == 0)
 303         {
 304           ERROR1 ("unexec: couldn't find \"%s\" section", (int) _BSS);
 305         }
 306     }
 307   else
 308     {
 309       ERROR0 ("can't build a COFF file from scratch yet");
 310     }
 311   orig_data_scnptr = f_dhdr->s_scnptr;
 312   orig_load_scnptr = f_lhdr ? f_lhdr->s_scnptr : 0;
 313
 314   /* Now we alter the contents of all the f_*hdr variables
 315      to correspond to what we want to dump.  */
 316
 317   /* Indicate that the reloc information is no longer valid for ld (bind);
 318      we only update it enough to fake out the exec-time loader.  */
 319   f_hdr.f_flags |= (F_RELFLG | F_EXEC);
 320
 321   f_ohdr.dsize = bss_start - f_ohdr.data_start;
 322   f_ohdr.bsize = bss_end - bss_start;
 323
 324   f_dhdr->s_size = f_ohdr.dsize;
 325   f_bhdr->s_size = f_ohdr.bsize;
 326   f_bhdr->s_paddr = f_ohdr.data_start + f_ohdr.dsize;
 327   f_bhdr->s_vaddr = f_ohdr.data_start + f_ohdr.dsize;
 328
 329   /* fix scnptr's */
 330   {
 331     ulong ptr = section[0].s_scnptr;
 332
 333     bias = -1;
 334     for (scns = 0; scns < f_hdr.f_nscns; scns++)
 335       {
 336         struct scnhdr *s = &section[scns];
 337
 338         if (s->s_flags & STYP_PAD)        /* .pad sections omitted in AIX 4.1 */
 339           {
 340             /*
 341              * the text_start should probably be o_algntext but that doesn't
 342              * seem to change
 343              */
 344             if (f_ohdr.text_start != 0) /* && scns != 0 */
 345               {
 346                 s->s_size = 512 - (ptr % 512);
 347                 if (s->s_size == 512)
 348                   s->s_size = 0;
 349               }
 350             s->s_scnptr = ptr;
 351           }
 352         else if (s->s_flags & STYP_DATA)
 353           s->s_scnptr = ptr;
 354         else if (!(s->s_flags & (STYP_TEXT | STYP_BSS)))
 355           {
 356             if (bias == -1)                /* if first section after bss */
 357               bias = ptr - s->s_scnptr;
 358
 359             s->s_scnptr += bias;
 360             ptr = s->s_scnptr;
 361           }
 362
 363         ptr = ptr + s->s_size;
 364       }
 365   }
 366
 367   /* fix other pointers */
 368   for (scns = 0; scns < f_hdr.f_nscns; scns++)
 369     {
 370       struct scnhdr *s = &section[scns];
 371
 372       if (s->s_relptr != 0)
 373         {
 374           s->s_relptr += bias;
 375         }
 376       if (s->s_lnnoptr != 0)
 377         {
 378           if (lnnoptr == 0) lnnoptr = s->s_lnnoptr;
 379           s->s_lnnoptr += bias;
 380         }
 381     }
 382
 383   if (f_hdr.f_symptr > 0L)
 384     {
 385       f_hdr.f_symptr += bias;
 386     }
 387
 388   text_scnptr = f_thdr->s_scnptr;
 389   data_scnptr = f_dhdr->s_scnptr;
 390   load_scnptr = f_lhdr ? f_lhdr->s_scnptr : 0;
 391
 392   if (write (new, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
 393     {
 394       PERROR (new_name);
 395     }
 396
 397   if (f_hdr.f_opthdr > 0)
 398     {
 399       if (write (new, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
 400         {
 401           PERROR (new_name);
 402         }
 403     }
 404
 405   for (scns = 0; scns < f_hdr.f_nscns; scns++) {
 406     struct scnhdr *s = &section[scns];
 407     if (write (new, s, sizeof (*s)) != sizeof (*s))
 408       {
 409         PERROR (new_name);
 410       }
 411   }
 412
 413   return (0);
 414 }
 415 \f
 416 /* ****************************************************************
 417
 418  *
 419  * Copy the text and data segments from memory to the new a.out
 420  */
 421 static int
 422 copy_text_and_data (int new)
 423 {
 424   char *end;
 425   char *ptr;
 426
 427   lseek (new, (long) text_scnptr, SEEK_SET);
 428   ptr = start_of_text () + text_scnptr;
 429   end = ptr + f_ohdr.tsize;
 430   write_segment (new, ptr, end);
 431
 432   lseek (new, (long) data_scnptr, SEEK_SET);
 433   ptr = (char *) f_ohdr.data_start;
 434   end = ptr + f_ohdr.dsize;
 435   write_segment (new, ptr, end);
 436
 437   return 0;
 438 }
 439
 440 #define UnexBlockSz (1<<12)                     /* read/write block size */
 441 static void
 442 write_segment (int new, char *ptr, char *end)
 443 {
 444   int i, nwrite, ret;
 445   char buf[80];
 446   extern int errno;
 447   char zeros[UnexBlockSz];
 448
 449   for (i = 0; ptr < end;)
 450     {
 451       /* distance to next block.  */
 452       nwrite = (((int) ptr + UnexBlockSz) & -UnexBlockSz) - (int) ptr;
 453       /* But not beyond specified end.  */
 454       if (nwrite > end - ptr) nwrite = end - ptr;
 455       ret = write (new, ptr, nwrite);
 456       /* If write gets a page fault, it means we reached
 457          a gap between the old text segment and the old data segment.
 458          This gap has probably been remapped into part of the text segment.
 459          So write zeros for it.  */
 460       if (ret == -1 && errno == EFAULT)
 461         {
 462           memset (zeros, 0, nwrite);
 463           write (new, zeros, nwrite);
 464         }
 465       else if (nwrite != ret)
 466         {
 467           sprintf (buf,
 468                    "unexec write failure: addr 0x%lx, fileno %d, size 0x%x, wrote 0x%x, errno %d",
 469                    (unsigned long)ptr, new, nwrite, ret, errno);
 470           PERROR (buf);
 471         }
 472       i += nwrite;
 473       ptr += nwrite;
 474     }
 475 }
 476 \f
 477 /* ****************************************************************
 478  * copy_sym
 479  *
 480  * Copy the relocation information and symbol table from the a.out to the new
 481  */
 482 static int
 483 copy_sym (int new, int a_out, char *a_name, char *new_name)
 484 {
 485   char page[UnexBlockSz];
 486   int n;
 487
 488   if (a_out < 0)
 489     return 0;
 490
 491   if (orig_load_scnptr == 0L)
 492     return 0;
 493
 494   if (lnnoptr && lnnoptr < orig_load_scnptr) /* if there is line number info  */
 495     lseek (a_out, lnnoptr, SEEK_SET);  /* start copying from there */
 496   else
 497     lseek (a_out, orig_load_scnptr, SEEK_SET); /* Position a.out to symtab. */
 498
 499   while ((n = read (a_out, page, sizeof page)) > 0)
 500     {
 501       if (write (new, page, n) != n)
 502         {
 503           PERROR (new_name);
 504         }
 505     }
 506   if (n < 0)
 507     {
 508       PERROR (a_name);
 509     }
 510   return 0;
 511 }
 512 \f
 513 /* ****************************************************************
 514  * mark_x
 515  *
 516  * After successfully building the new a.out, mark it executable
 517  */
 518 static void
 519 mark_x (char *name)
 520 {
 521   struct stat sbuf;
 522   int um;
 523   int new = 0;  /* for PERROR */
 524
 525   um = umask (777);
 526   umask (um);
 527   if (stat (name, &sbuf) == -1)
 528     {
 529       PERROR (name);
 530     }
 531   sbuf.st_mode |= 0111 & ~um;
 532   if (chmod (name, sbuf.st_mode) == -1)
 533     PERROR (name);
 534 }
 535 \f
 536 static int
 537 adjust_lnnoptrs (int writedesc, int readdesc, char *new_name)
 538 {
 539   int nsyms;
 540   int naux;
 541   int new;
 542   struct syment symentry;
 543   union auxent auxentry;
 544
 545   if (!lnnoptr || !f_hdr.f_symptr)
 546     return 0;
 547
 548   if ((new = open (new_name, O_RDWR)) < 0)
 549     {
 550       PERROR (new_name);
 551       return -1;
 552     }
 553
 554   lseek (new, f_hdr.f_symptr, SEEK_SET);
 555   for (nsyms = 0; nsyms < f_hdr.f_nsyms; nsyms++)
 556     {
 557       read (new, &symentry, SYMESZ);
 558       if (symentry.n_sclass == C_BINCL || symentry.n_sclass == C_EINCL)
 559         {
 560           symentry.n_value += bias;
 561           lseek (new, -SYMESZ, SEEK_CUR);
 562           write (new, &symentry, SYMESZ);
 563         }
 564
 565       for (naux = symentry.n_numaux; naux-- != 0; )
 566         {
 567           read (new, &auxentry, AUXESZ);
 568           nsyms++;
 569           if (naux != 0              /* skip csect auxentry (last entry) */
 570               && (symentry.n_sclass == C_EXT || symentry.n_sclass == C_HIDEXT))
 571             {
 572               auxentry.x_sym.x_fcnary.x_fcn.x_lnnoptr += bias;
 573               lseek (new, -AUXESZ, SEEK_CUR);
 574               write (new, &auxentry, AUXESZ);
 575             }
 576         }
 577     }
 578   close (new);
 579
 580   return 0;
 581 }
 582
 583 static int
 584 unrelocate_symbols (int new, int a_out, char *a_name, char *new_name)
 585 {
 586   int i;
 587   LDHDR ldhdr;
 588   LDREL ldrel;
 589   ulong t_reloc = (ulong) &_text - f_ohdr.text_start;
 590 #ifndef ALIGN_DATA_RELOC
 591   ulong d_reloc = (ulong) &_data - f_ohdr.data_start;
 592 #else
 593   /* This worked (and was needed) before AIX 4.2.
 594      I have no idea why. -- Mike */
 595   ulong d_reloc = (ulong) &_data - ALIGN(f_ohdr.data_start, 2);
 596 #endif
 597   int * p;
 598
 599   if (load_scnptr == 0)
 600     return 0;
 601
 602   lseek (a_out, orig_load_scnptr, SEEK_SET);
 603   if (read (a_out, &ldhdr, sizeof (ldhdr)) != sizeof (ldhdr))
 604     {
 605       PERROR (new_name);
 606     }
 607
 608 #define SYMNDX_TEXT     0
 609 #define SYMNDX_DATA     1
 610 #define SYMNDX_BSS      2
 611
 612   for (i = 0; i < ldhdr.l_nreloc; i++)
 613     {
 614       lseek (a_out,
 615              orig_load_scnptr + LDHDRSZ + LDSYMSZ*ldhdr.l_nsyms + LDRELSZ*i,
 616              SEEK_SET);
 617
 618       if (read (a_out, &ldrel, LDRELSZ) != LDRELSZ)
 619         {
 620           PERROR (a_name);
 621         }
 622
 623       /* move the BSS loader symbols to the DATA segment */
 624       if (ldrel.l_symndx == SYMNDX_BSS)
 625         {
 626           ldrel.l_symndx = SYMNDX_DATA;
 627
 628           lseek (new,
 629                  load_scnptr + LDHDRSZ + LDSYMSZ*ldhdr.l_nsyms + LDRELSZ*i,
 630                  SEEK_SET);
 631
 632           if (write (new, &ldrel, LDRELSZ) != LDRELSZ)
 633             {
 634               PERROR (new_name);
 635             }
 636         }
 637
 638       if (ldrel.l_rsecnm == f_ohdr.o_sndata)
 639         {
 640           int orig_int;
 641
 642           lseek (a_out,
 643                  orig_data_scnptr + (ldrel.l_vaddr - f_ohdr.data_start),
 644                  SEEK_SET);
 645
 646           if (read (a_out, (void *) &orig_int, sizeof (orig_int))
 647               != sizeof (orig_int))
 648             {
 649               PERROR (a_name);
 650             }
 651
 652           p = (int *) (ldrel.l_vaddr + d_reloc);
 653
 654           switch (ldrel.l_symndx) {
 655           case SYMNDX_TEXT:
 656             orig_int = * p - t_reloc;
 657             break;
 658
 659           case SYMNDX_DATA:
 660           case SYMNDX_BSS:
 661             orig_int = * p - d_reloc;
 662             break;
 663           }
 664
 665           if (orig_int != * p)
 666             {
 667               lseek (new,
 668                      data_scnptr + (ldrel.l_vaddr - f_ohdr.data_start),
 669                      SEEK_SET);
 670               if (write (new, (void *) &orig_int, sizeof (orig_int))
 671                   != sizeof (orig_int))
 672                 {
 673                   PERROR (new_name);
 674                 }
 675             }
 676         }
 677     }
 678   return 0;
 679 }
 680
 681 /* arch-tag: 0783857a-7c2d-456f-a426-58b722d69fd0
 682    (do not change this comment) */