src/unexaix.c

   1 /* Dump an executable image.
   2    Copyright (C) 1985-1988, 1999, 2001-2013 Free Software Foundation,
   3    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 3 of the License, or
  10 (at your option) 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.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 /*
  21 In other words, you are welcome to use, share and improve this program.
  22 You are forbidden to forbid anyone else to use, share and improve
  23 what you give them.   Help stamp out software-hoarding!  */
  24
  25
  26 /* Originally based on the COFF unexec.c by Spencer W. Thomas.
  27  *
  28  * Subsequently hacked on by
  29  * Bill Mann <Bill_Man@praxisint.com>
  30  * Andrew Vignaux <Andrew.Vignaux@comp.vuw.ac.nz>
  31  * Mike Sperber <sperber@informatik.uni-tuebingen.de>
  32  *
  33  * Synopsis:
  34  *      unexec (const char *new_name, const *old_name);
  35  *
  36  * Takes a snapshot of the program and makes an a.out format file in the
  37  * file named by the string argument new_name.
  38  * If a_name is non-NULL, the symbol table will be taken from the given file.
  39  * On some machines, an existing a_name file is required.
  40  *
  41  */
  42
  43 #include <config.h>
  44 #include "unexec.h"
  45 #include "lisp.h"
  46
  47 #define PERROR(file) report_error (file, new)
  48 #include <a.out.h>
  49 /* Define getpagesize () if the system does not.
  50    Note that this may depend on symbols defined in a.out.h
  51  */
  52 #include "getpagesize.h"
  53
  54 #include <sys/types.h>
  55 #include <inttypes.h>
  56 #include <stdarg.h>
  57 #include <stdio.h>
  58 #include <sys/stat.h>
  59 #include <errno.h>
  60 #include <unistd.h>
  61 #include <fcntl.h>
  62
  63 extern char _data[];
  64 extern char _text[];
  65
  66 #include <filehdr.h>
  67 #include <aouthdr.h>
  68 #include <scnhdr.h>
  69 #include <syms.h>
  70
  71 static struct filehdr f_hdr;            /* File header */
  72 static struct aouthdr f_ohdr;           /* Optional file header (a.out) */
  73 static off_t bias;                      /* Bias to add for growth */
  74 static off_t lnnoptr;                   /* Pointer to line-number info within file */
  75
  76 static off_t text_scnptr;
  77 static off_t data_scnptr;
  78 #define ALIGN(val, pwr) (((val) + ((1L<<(pwr))-1)) & ~((1L<<(pwr))-1))
  79 static off_t load_scnptr;
  80 static off_t orig_load_scnptr;
  81 static off_t orig_data_scnptr;
  82 static int unrelocate_symbols (int, int, const char *, const char *);
  83
  84 #ifndef MAX_SECTIONS
  85 #define MAX_SECTIONS    10
  86 #endif
  87
  88 static int adjust_lnnoptrs (int, int, const char *);
  89
  90 static int pagemask;
  91
  92 #include "lisp.h"
  93
  94 static _Noreturn void
  95 report_error (const char *file, int fd)
  96 {
  97   if (fd)
  98     {
  99       int failed_errno = errno;
 100       emacs_close (fd);
 101       errno = failed_errno;
 102     }
 103   report_file_error ("Cannot unexec", Fcons (build_string (file), Qnil));
 104 }
 105
 106 #define ERROR0(msg) report_error_1 (new, msg)
 107 #define ERROR1(msg,x) report_error_1 (new, msg, x)
 108 #define ERROR2(msg,x,y) report_error_1 (new, msg, x, y)
 109
 110 static _Noreturn void ATTRIBUTE_FORMAT_PRINTF (2, 3)
 111 report_error_1 (int fd, const char *msg, ...)
 112 {
 113   va_list ap;
 114   emacs_close (fd);
 115   va_start (ap, msg);
 116   verror (msg, ap);
 117   va_end (ap);
 118 }
 119
 120 static int make_hdr (int, int, const char *, const char *);
 121 static void mark_x (const char *);
 122 static int copy_text_and_data (int);
 123 static int copy_sym (int, int, const char *, const char *);
 124 static void write_segment (int, char *, char *);
 125 \f
 126 /* ****************************************************************
 127  * unexec
 128  *
 129  * driving logic.
 130  */
 131 void
 132 unexec (const char *new_name, const char *a_name)
 133 {
 134   int new = -1, a_out = -1;
 135
 136   if (a_name && (a_out = emacs_open (a_name, O_RDONLY, 0)) < 0)
 137     {
 138       PERROR (a_name);
 139     }
 140   if ((new = emacs_open (new_name, O_WRONLY | O_CREAT | O_TRUNC, 0666)) < 0)
 141     {
 142       PERROR (new_name);
 143     }
 144   if (make_hdr (new, a_out,
 145                 a_name, new_name) < 0
 146       || copy_text_and_data (new) < 0
 147       || copy_sym (new, a_out, a_name, new_name) < 0
 148       || adjust_lnnoptrs (new, a_out, new_name) < 0
 149       || unrelocate_symbols (new, a_out, a_name, new_name) < 0)
 150     {
 151       emacs_close (new);
 152       return;
 153     }
 154
 155   emacs_close (new);
 156   if (a_out >= 0)
 157     emacs_close (a_out);
 158   mark_x (new_name);
 159 }
 160
 161 /* ****************************************************************
 162  * make_hdr
 163  *
 164  * Make the header in the new a.out from the header in core.
 165  * Modify the text and data sizes.
 166  */
 167 static int
 168 make_hdr (int new, int a_out,
 169           const char *a_name, const char *new_name)
 170 {
 171   int scns;
 172   uintptr_t bss_start;
 173   uintptr_t data_start;
 174
 175   struct scnhdr section[MAX_SECTIONS];
 176   struct scnhdr * f_thdr;               /* Text section header */
 177   struct scnhdr * f_dhdr;               /* Data section header */
 178   struct scnhdr * f_bhdr;               /* Bss section header */
 179   struct scnhdr * f_lhdr;               /* Loader section header */
 180   struct scnhdr * f_tchdr;              /* Typechk section header */
 181   struct scnhdr * f_dbhdr;              /* Debug section header */
 182   struct scnhdr * f_xhdr;               /* Except section header */
 183
 184   load_scnptr = orig_load_scnptr = lnnoptr = 0;
 185   pagemask = getpagesize () - 1;
 186
 187   /* Adjust text/data boundary. */
 188   data_start = (uintptr_t) _data;
 189
 190   data_start = data_start & ~pagemask; /* (Down) to page boundary. */
 191
 192   bss_start = (uintptr_t) sbrk (0) + pagemask;
 193   bss_start &= ~ pagemask;
 194
 195   if (data_start > bss_start)   /* Can't have negative data size. */
 196     {
 197       ERROR2 (("unexec: data_start (0x%"PRIxPTR
 198                ") can't be greater than bss_start (0x%"PRIxPTR")"),
 199               data_start, bss_start);
 200     }
 201
 202   /* Salvage as much info from the existing file as possible */
 203   f_thdr = NULL; f_dhdr = NULL; f_bhdr = NULL;
 204   f_lhdr = NULL; f_tchdr = NULL; f_dbhdr = NULL; f_xhdr = NULL;
 205   if (a_out >= 0)
 206     {
 207       if (read (a_out, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
 208         {
 209           PERROR (a_name);
 210         }
 211       if (f_hdr.f_opthdr > 0)
 212         {
 213           if (read (a_out, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
 214             {
 215               PERROR (a_name);
 216             }
 217         }
 218       if (f_hdr.f_nscns > MAX_SECTIONS)
 219         {
 220           ERROR0 ("unexec: too many section headers -- increase MAX_SECTIONS");
 221         }
 222       /* Loop through section headers */
 223       for (scns = 0; scns < f_hdr.f_nscns; scns++) {
 224         struct scnhdr *s = &section[scns];
 225         if (read (a_out, s, sizeof (*s)) != sizeof (*s))
 226           {
 227             PERROR (a_name);
 228           }
 229
 230 #define CHECK_SCNHDR(ptr, name, flags) \
 231   if (strcmp (s->s_name, name) == 0) { \
 232     if (s->s_flags != flags) { \
 233       fprintf (stderr, "unexec: %lx flags where %x expected in %s section.\n", \
 234                (unsigned long)s->s_flags, flags, name);                 \
 235     } \
 236     if (ptr) { \
 237       fprintf (stderr, "unexec: duplicate section header for section %s.\n", \
 238                name);                                                   \
 239     } \
 240     ptr = s; \
 241   }
 242         CHECK_SCNHDR (f_thdr, _TEXT, STYP_TEXT);
 243         CHECK_SCNHDR (f_dhdr, _DATA, STYP_DATA);
 244         CHECK_SCNHDR (f_bhdr, _BSS, STYP_BSS);
 245         CHECK_SCNHDR (f_lhdr, _LOADER, STYP_LOADER);
 246         CHECK_SCNHDR (f_dbhdr, _DEBUG,  STYP_DEBUG);
 247         CHECK_SCNHDR (f_tchdr, _TYPCHK,  STYP_TYPCHK);
 248         CHECK_SCNHDR (f_xhdr, _EXCEPT,  STYP_EXCEPT);
 249       }
 250
 251       if (f_thdr == 0)
 252         {
 253           ERROR1 ("unexec: couldn't find \"%s\" section", (int) _TEXT);
 254         }
 255       if (f_dhdr == 0)
 256         {
 257           ERROR1 ("unexec: couldn't find \"%s\" section", (int) _DATA);
 258         }
 259       if (f_bhdr == 0)
 260         {
 261           ERROR1 ("unexec: couldn't find \"%s\" section", (int) _BSS);
 262         }
 263     }
 264   else
 265     {
 266       ERROR0 ("can't build a COFF file from scratch yet");
 267     }
 268   orig_data_scnptr = f_dhdr->s_scnptr;
 269   orig_load_scnptr = f_lhdr ? f_lhdr->s_scnptr : 0;
 270
 271   /* Now we alter the contents of all the f_*hdr variables
 272      to correspond to what we want to dump.  */
 273
 274   /* Indicate that the reloc information is no longer valid for ld (bind);
 275      we only update it enough to fake out the exec-time loader.  */
 276   f_hdr.f_flags |= (F_RELFLG | F_EXEC);
 277
 278   f_ohdr.dsize = bss_start - f_ohdr.data_start;
 279   f_ohdr.bsize = 0;
 280
 281   f_dhdr->s_size = f_ohdr.dsize;
 282   f_bhdr->s_size = f_ohdr.bsize;
 283   f_bhdr->s_paddr = f_ohdr.data_start + f_ohdr.dsize;
 284   f_bhdr->s_vaddr = f_ohdr.data_start + f_ohdr.dsize;
 285
 286   /* fix scnptr's */
 287   {
 288     off_t ptr = section[0].s_scnptr;
 289
 290     bias = -1;
 291     for (scns = 0; scns < f_hdr.f_nscns; scns++)
 292       {
 293         struct scnhdr *s = &section[scns];
 294
 295         if (s->s_flags & STYP_PAD)        /* .pad sections omitted in AIX 4.1 */
 296           {
 297             /*
 298              * the text_start should probably be o_algntext but that doesn't
 299              * seem to change
 300              */
 301             if (f_ohdr.text_start != 0) /* && scns != 0 */
 302               {
 303                 s->s_size = 512 - (ptr % 512);
 304                 if (s->s_size == 512)
 305                   s->s_size = 0;
 306               }
 307             s->s_scnptr = ptr;
 308           }
 309         else if (s->s_flags & STYP_DATA)
 310           s->s_scnptr = ptr;
 311         else if (!(s->s_flags & (STYP_TEXT | STYP_BSS)))
 312           {
 313             if (bias == -1)                /* if first section after bss */
 314               bias = ptr - s->s_scnptr;
 315
 316             s->s_scnptr += bias;
 317             ptr = s->s_scnptr;
 318           }
 319
 320         ptr = ptr + s->s_size;
 321       }
 322   }
 323
 324   /* fix other pointers */
 325   for (scns = 0; scns < f_hdr.f_nscns; scns++)
 326     {
 327       struct scnhdr *s = &section[scns];
 328
 329       if (s->s_relptr != 0)
 330         {
 331           s->s_relptr += bias;
 332         }
 333       if (s->s_lnnoptr != 0)
 334         {
 335           if (lnnoptr == 0) lnnoptr = s->s_lnnoptr;
 336           s->s_lnnoptr += bias;
 337         }
 338     }
 339
 340   if (f_hdr.f_symptr > 0L)
 341     {
 342       f_hdr.f_symptr += bias;
 343     }
 344
 345   text_scnptr = f_thdr->s_scnptr;
 346   data_scnptr = f_dhdr->s_scnptr;
 347   load_scnptr = f_lhdr ? f_lhdr->s_scnptr : 0;
 348
 349   if (write (new, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
 350     {
 351       PERROR (new_name);
 352     }
 353
 354   if (f_hdr.f_opthdr > 0)
 355     {
 356       if (write (new, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
 357         {
 358           PERROR (new_name);
 359         }
 360     }
 361
 362   for (scns = 0; scns < f_hdr.f_nscns; scns++) {
 363     struct scnhdr *s = &section[scns];
 364     if (write (new, s, sizeof (*s)) != sizeof (*s))
 365       {
 366         PERROR (new_name);
 367       }
 368   }
 369
 370   return (0);
 371 }
 372 \f
 373 /* ****************************************************************
 374
 375  *
 376  * Copy the text and data segments from memory to the new a.out
 377  */
 378 static int
 379 copy_text_and_data (int new)
 380 {
 381   char *end;
 382   char *ptr;
 383
 384   lseek (new, text_scnptr, SEEK_SET);
 385   ptr = _text + text_scnptr;
 386   end = ptr + f_ohdr.tsize;
 387   write_segment (new, ptr, end);
 388
 389   lseek (new, data_scnptr, SEEK_SET);
 390   ptr = (char *) f_ohdr.data_start;
 391   end = ptr + f_ohdr.dsize;
 392   write_segment (new, ptr, end);
 393
 394   return 0;
 395 }
 396
 397 #define UnexBlockSz (1<<12)                     /* read/write block size */
 398 static void
 399 write_segment (int new, char *ptr, char *end)
 400 {
 401   int i, nwrite, ret;
 402   char zeros[UnexBlockSz];
 403
 404   for (i = 0; ptr < end;)
 405     {
 406       /* distance to next block.  */
 407       nwrite = (((int) ptr + UnexBlockSz) & -UnexBlockSz) - (int) ptr;
 408       /* But not beyond specified end.  */
 409       if (nwrite > end - ptr) nwrite = end - ptr;
 410       ret = write (new, ptr, nwrite);
 411       /* If write gets a page fault, it means we reached
 412          a gap between the old text segment and the old data segment.
 413          This gap has probably been remapped into part of the text segment.
 414          So write zeros for it.  */
 415       if (ret == -1 && errno == EFAULT)
 416         {
 417           memset (zeros, 0, nwrite);
 418           write (new, zeros, nwrite);
 419         }
 420       else if (nwrite != ret)
 421         {
 422           int write_errno = errno;
 423           char buf[1000];
 424           void *addr = ptr;
 425           sprintf (buf,
 426                    "unexec write failure: addr %p, fileno %d, size 0x%x, wrote 0x%x, errno %d",
 427                    addr, new, nwrite, ret, errno);
 428           errno = write_errno;
 429           PERROR (buf);
 430         }
 431       i += nwrite;
 432       ptr += nwrite;
 433     }
 434 }
 435 \f
 436 /* ****************************************************************
 437  * copy_sym
 438  *
 439  * Copy the relocation information and symbol table from the a.out to the new
 440  */
 441 static int
 442 copy_sym (int new, int a_out, const char *a_name, const char *new_name)
 443 {
 444   char page[UnexBlockSz];
 445   int n;
 446
 447   if (a_out < 0)
 448     return 0;
 449
 450   if (orig_load_scnptr == 0L)
 451     return 0;
 452
 453   if (lnnoptr && lnnoptr < orig_load_scnptr) /* if there is line number info  */
 454     lseek (a_out, lnnoptr, SEEK_SET);  /* start copying from there */
 455   else
 456     lseek (a_out, orig_load_scnptr, SEEK_SET); /* Position a.out to symtab. */
 457
 458   while ((n = read (a_out, page, sizeof page)) > 0)
 459     {
 460       if (write (new, page, n) != n)
 461         {
 462           PERROR (new_name);
 463         }
 464     }
 465   if (n < 0)
 466     {
 467       PERROR (a_name);
 468     }
 469   return 0;
 470 }
 471 \f
 472 /* ****************************************************************
 473  * mark_x
 474  *
 475  * After successfully building the new a.out, mark it executable
 476  */
 477 static void
 478 mark_x (const char *name)
 479 {
 480   struct stat sbuf;
 481   int um;
 482   int new = 0;  /* for PERROR */
 483
 484   um = umask (777);
 485   umask (um);
 486   if (stat (name, &sbuf) == -1)
 487     {
 488       PERROR (name);
 489     }
 490   sbuf.st_mode |= 0111 & ~um;
 491   if (chmod (name, sbuf.st_mode) == -1)
 492     PERROR (name);
 493 }
 494 \f
 495 static int
 496 adjust_lnnoptrs (int writedesc, int readdesc, const char *new_name)
 497 {
 498   int nsyms;
 499   int naux;
 500   int new;
 501   struct syment symentry;
 502   union auxent auxentry;
 503
 504   if (!lnnoptr || !f_hdr.f_symptr)
 505     return 0;
 506
 507   if ((new = emacs_open (new_name, O_RDWR, 0)) < 0)
 508     {
 509       PERROR (new_name);
 510       return -1;
 511     }
 512
 513   lseek (new, f_hdr.f_symptr, SEEK_SET);
 514   for (nsyms = 0; nsyms < f_hdr.f_nsyms; nsyms++)
 515     {
 516       read (new, &symentry, SYMESZ);
 517       if (symentry.n_sclass == C_BINCL || symentry.n_sclass == C_EINCL)
 518         {
 519           symentry.n_value += bias;
 520           lseek (new, -SYMESZ, SEEK_CUR);
 521           write (new, &symentry, SYMESZ);
 522         }
 523
 524       for (naux = symentry.n_numaux; naux-- != 0; )
 525         {
 526           read (new, &auxentry, AUXESZ);
 527           nsyms++;
 528           if (naux != 0              /* skip csect auxentry (last entry) */
 529               && (symentry.n_sclass == C_EXT || symentry.n_sclass == C_HIDEXT))
 530             {
 531               auxentry.x_sym.x_fcnary.x_fcn.x_lnnoptr += bias;
 532               lseek (new, -AUXESZ, SEEK_CUR);
 533               write (new, &auxentry, AUXESZ);
 534             }
 535         }
 536     }
 537   emacs_close (new);
 538
 539   return 0;
 540 }
 541
 542 static int
 543 unrelocate_symbols (int new, int a_out,
 544                     const char *a_name, const char *new_name)
 545 {
 546   int i;
 547   LDHDR ldhdr;
 548   LDREL ldrel;
 549   off_t t_reloc = (intptr_t) _text - f_ohdr.text_start;
 550 #ifndef ALIGN_DATA_RELOC
 551   off_t d_reloc = (intptr_t) _data - f_ohdr.data_start;
 552 #else
 553   /* This worked (and was needed) before AIX 4.2.
 554      I have no idea why. -- Mike */
 555   off_t d_reloc = (intptr_t) _data - ALIGN (f_ohdr.data_start, 2);
 556 #endif
 557   int * p;
 558
 559   if (load_scnptr == 0)
 560     return 0;
 561
 562   lseek (a_out, orig_load_scnptr, SEEK_SET);
 563   if (read (a_out, &ldhdr, sizeof (ldhdr)) != sizeof (ldhdr))
 564     {
 565       PERROR (new_name);
 566     }
 567
 568 #define SYMNDX_TEXT     0
 569 #define SYMNDX_DATA     1
 570 #define SYMNDX_BSS      2
 571
 572   for (i = 0; i < ldhdr.l_nreloc; i++)
 573     {
 574       lseek (a_out,
 575              orig_load_scnptr + LDHDRSZ + LDSYMSZ*ldhdr.l_nsyms + LDRELSZ*i,
 576              SEEK_SET);
 577
 578       if (read (a_out, &ldrel, LDRELSZ) != LDRELSZ)
 579         {
 580           PERROR (a_name);
 581         }
 582
 583       /* move the BSS loader symbols to the DATA segment */
 584       if (ldrel.l_symndx == SYMNDX_BSS)
 585         {
 586           ldrel.l_symndx = SYMNDX_DATA;
 587
 588           lseek (new,
 589                  load_scnptr + LDHDRSZ + LDSYMSZ*ldhdr.l_nsyms + LDRELSZ*i,
 590                  SEEK_SET);
 591
 592           if (write (new, &ldrel, LDRELSZ) != LDRELSZ)
 593             {
 594               PERROR (new_name);
 595             }
 596         }
 597
 598       if (ldrel.l_rsecnm == f_ohdr.o_sndata)
 599         {
 600           int orig_int;
 601
 602           lseek (a_out,
 603                  orig_data_scnptr + (ldrel.l_vaddr - f_ohdr.data_start),
 604                  SEEK_SET);
 605
 606           if (read (a_out, (void *) &orig_int, sizeof (orig_int))
 607               != sizeof (orig_int))
 608             {
 609               PERROR (a_name);
 610             }
 611
 612           p = (int *) (ldrel.l_vaddr + d_reloc);
 613
 614           switch (ldrel.l_symndx) {
 615           case SYMNDX_TEXT:
 616             orig_int = * p - t_reloc;
 617             break;
 618
 619           case SYMNDX_DATA:
 620           case SYMNDX_BSS:
 621             orig_int = * p - d_reloc;
 622             break;
 623           }
 624
 625           if (orig_int != * p)
 626             {
 627               lseek (new,
 628                      data_scnptr + (ldrel.l_vaddr - f_ohdr.data_start),
 629                      SEEK_SET);
 630               if (write (new, (void *) &orig_int, sizeof (orig_int))
 631                   != sizeof (orig_int))
 632                 {
 633                   PERROR (new_name);
 634                 }
 635             }
 636         }
 637     }
 638   return 0;
 639 }