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
  46 #define PERROR(file) report_error (file, new)
  47 #include <a.out.h>
  48 /* Define getpagesize () if the system does not.
  49    Note that this may depend on symbols defined in a.out.h
  50  */
  51 #include "getpagesize.h"
  52
  53 #include <sys/types.h>
  54 #include <inttypes.h>
  55 #include <stdarg.h>
  56 #include <stdio.h>
  57 #include <sys/stat.h>
  58 #include <errno.h>
  59 #include <unistd.h>
  60 #include <fcntl.h>
  61
  62 #include "mem-limits.h"
  63
  64 extern char _data[];
  65 extern char _text[];
  66
  67 #include <filehdr.h>
  68 #include <aouthdr.h>
  69 #include <scnhdr.h>
  70 #include <syms.h>
  71
  72 static struct filehdr f_hdr;            /* File header */
  73 static struct aouthdr f_ohdr;           /* Optional file header (a.out) */
  74 static off_t bias;                      /* Bias to add for growth */
  75 static off_t lnnoptr;                   /* Pointer to line-number info within file */
  76
  77 static off_t text_scnptr;
  78 static off_t data_scnptr;
  79 #define ALIGN(val, pwr) (((val) + ((1L<<(pwr))-1)) & ~((1L<<(pwr))-1))
  80 static off_t load_scnptr;
  81 static off_t orig_load_scnptr;
  82 static off_t orig_data_scnptr;
  83 static int unrelocate_symbols (int, int, const char *, const char *);
  84
  85 #ifndef MAX_SECTIONS
  86 #define MAX_SECTIONS    10
  87 #endif
  88
  89 static int adjust_lnnoptrs (int, int, const char *);
  90
  91 static int pagemask;
  92
  93 #include "lisp.h"
  94
  95 static _Noreturn void
  96 report_error (const char *file, int fd)
  97 {
  98   if (fd)
  99     {
 100       int failed_errno = errno;
 101       close (fd);
 102       errno = failed_errno;
 103     }
 104   report_file_error ("Cannot unexec", Fcons (build_string (file), Qnil));
 105 }
 106
 107 #define ERROR0(msg) report_error_1 (new, msg)
 108 #define ERROR1(msg,x) report_error_1 (new, msg, x)
 109 #define ERROR2(msg,x,y) report_error_1 (new, msg, x, y)
 110
 111 static _Noreturn void ATTRIBUTE_FORMAT_PRINTF (2, 3)
 112 report_error_1 (int fd, const char *msg, ...)
 113 {
 114   va_list ap;
 115   close (fd);
 116   va_start (ap, msg);
 117   verror (msg, ap);
 118   va_end (ap);
 119 }
 120
 121 static int make_hdr (int, int, const char *, const char *);
 122 static void mark_x (const char *);
 123 static int copy_text_and_data (int);
 124 static int copy_sym (int, int, const char *, const char *);
 125 static void write_segment (int, char *, char *);
 126 \f
 127 /* ****************************************************************
 128  * unexec
 129  *
 130  * driving logic.
 131  */
 132 void
 133 unexec (const char *new_name, const char *a_name)
 134 {
 135   int new = -1, a_out = -1;
 136
 137   if (a_name && (a_out = open (a_name, O_RDONLY)) < 0)
 138     {
 139       PERROR (a_name);
 140     }
 141   if ((new = creat (new_name, 0666)) < 0)
 142     {
 143       PERROR (new_name);
 144     }
 145   if (make_hdr (new, a_out,
 146                 a_name, new_name) < 0
 147       || copy_text_and_data (new) < 0
 148       || copy_sym (new, a_out, a_name, new_name) < 0
 149       || adjust_lnnoptrs (new, a_out, new_name) < 0
 150       || unrelocate_symbols (new, a_out, a_name, new_name) < 0)
 151     {
 152       close (new);
 153       return;
 154     }
 155
 156   close (new);
 157   if (a_out >= 0)
 158     close (a_out);
 159   mark_x (new_name);
 160 }
 161
 162 /* ****************************************************************
 163  * make_hdr
 164  *
 165  * Make the header in the new a.out from the header in core.
 166  * Modify the text and data sizes.
 167  */
 168 static int
 169 make_hdr (int new, int a_out,
 170           const char *a_name, const char *new_name)
 171 {
 172   int scns;
 173   uintptr_t bss_start;
 174   uintptr_t data_start;
 175
 176   struct scnhdr section[MAX_SECTIONS];
 177   struct scnhdr * f_thdr;               /* Text section header */
 178   struct scnhdr * f_dhdr;               /* Data section header */
 179   struct scnhdr * f_bhdr;               /* Bss section header */
 180   struct scnhdr * f_lhdr;               /* Loader section header */
 181   struct scnhdr * f_tchdr;              /* Typechk section header */
 182   struct scnhdr * f_dbhdr;              /* Debug section header */
 183   struct scnhdr * f_xhdr;               /* Except section header */
 184
 185   load_scnptr = orig_load_scnptr = lnnoptr = 0;
 186   pagemask = getpagesize () - 1;
 187
 188   /* Adjust text/data boundary. */
 189   data_start = (uintptr_t) _data;
 190
 191   data_start = data_start & ~pagemask; /* (Down) to page boundary. */
 192
 193   bss_start = (uintptr_t) sbrk (0) + pagemask;
 194   bss_start &= ~ pagemask;
 195
 196   if (data_start > bss_start)   /* Can't have negative data size. */
 197     {
 198       ERROR2 (("unexec: data_start (0x%"PRIxPTR
 199                ") can't be greater than bss_start (0x%"PRIxPTR")"),
 200               data_start, bss_start);
 201     }
 202
 203   /* Salvage as much info from the existing file as possible */
 204   f_thdr = NULL; f_dhdr = NULL; f_bhdr = NULL;
 205   f_lhdr = NULL; f_tchdr = NULL; f_dbhdr = NULL; f_xhdr = NULL;
 206   if (a_out >= 0)
 207     {
 208       if (read (a_out, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
 209         {
 210           PERROR (a_name);
 211         }
 212       if (f_hdr.f_opthdr > 0)
 213         {
 214           if (read (a_out, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
 215             {
 216               PERROR (a_name);
 217             }
 218         }
 219       if (f_hdr.f_nscns > MAX_SECTIONS)
 220         {
 221           ERROR0 ("unexec: too many section headers -- increase MAX_SECTIONS");
 222         }
 223       /* Loop through section headers */
 224       for (scns = 0; scns < f_hdr.f_nscns; scns++) {
 225         struct scnhdr *s = &section[scns];
 226         if (read (a_out, s, sizeof (*s)) != sizeof (*s))
 227           {
 228             PERROR (a_name);
 229           }
 230
 231 #define CHECK_SCNHDR(ptr, name, flags) \
 232   if (strcmp (s->s_name, name) == 0) { \
 233     if (s->s_flags != flags) { \
 234       fprintf (stderr, "unexec: %lx flags where %x expected in %s section.\n", \
 235                (unsigned long)s->s_flags, flags, name);                 \
 236     } \
 237     if (ptr) { \
 238       fprintf (stderr, "unexec: duplicate section header for section %s.\n", \
 239                name);                                                   \
 240     } \
 241     ptr = s; \
 242   }
 243         CHECK_SCNHDR (f_thdr, _TEXT, STYP_TEXT);
 244         CHECK_SCNHDR (f_dhdr, _DATA, STYP_DATA);
 245         CHECK_SCNHDR (f_bhdr, _BSS, STYP_BSS);
 246         CHECK_SCNHDR (f_lhdr, _LOADER, STYP_LOADER);
 247         CHECK_SCNHDR (f_dbhdr, _DEBUG,  STYP_DEBUG);
 248         CHECK_SCNHDR (f_tchdr, _TYPCHK,  STYP_TYPCHK);
 249         CHECK_SCNHDR (f_xhdr, _EXCEPT,  STYP_EXCEPT);
 250       }
 251
 252       if (f_thdr == 0)
 253         {
 254           ERROR1 ("unexec: couldn't find \"%s\" section", (int) _TEXT);
 255         }
 256       if (f_dhdr == 0)
 257         {
 258           ERROR1 ("unexec: couldn't find \"%s\" section", (int) _DATA);
 259         }
 260       if (f_bhdr == 0)
 261         {
 262           ERROR1 ("unexec: couldn't find \"%s\" section", (int) _BSS);
 263         }
 264     }
 265   else
 266     {
 267       ERROR0 ("can't build a COFF file from scratch yet");
 268     }
 269   orig_data_scnptr = f_dhdr->s_scnptr;
 270   orig_load_scnptr = f_lhdr ? f_lhdr->s_scnptr : 0;
 271
 272   /* Now we alter the contents of all the f_*hdr variables
 273      to correspond to what we want to dump.  */
 274
 275   /* Indicate that the reloc information is no longer valid for ld (bind);
 276      we only update it enough to fake out the exec-time loader.  */
 277   f_hdr.f_flags |= (F_RELFLG | F_EXEC);
 278
 279   f_ohdr.dsize = bss_start - f_ohdr.data_start;
 280   f_ohdr.bsize = 0;
 281
 282   f_dhdr->s_size = f_ohdr.dsize;
 283   f_bhdr->s_size = f_ohdr.bsize;
 284   f_bhdr->s_paddr = f_ohdr.data_start + f_ohdr.dsize;
 285   f_bhdr->s_vaddr = f_ohdr.data_start + f_ohdr.dsize;
 286
 287   /* fix scnptr's */
 288   {
 289     off_t ptr = section[0].s_scnptr;
 290
 291     bias = -1;
 292     for (scns = 0; scns < f_hdr.f_nscns; scns++)
 293       {
 294         struct scnhdr *s = &section[scns];
 295
 296         if (s->s_flags & STYP_PAD)        /* .pad sections omitted in AIX 4.1 */
 297           {
 298             /*
 299              * the text_start should probably be o_algntext but that doesn't
 300              * seem to change
 301              */
 302             if (f_ohdr.text_start != 0) /* && scns != 0 */
 303               {
 304                 s->s_size = 512 - (ptr % 512);
 305                 if (s->s_size == 512)
 306                   s->s_size = 0;
 307               }
 308             s->s_scnptr = ptr;
 309           }
 310         else if (s->s_flags & STYP_DATA)
 311           s->s_scnptr = ptr;
 312         else if (!(s->s_flags & (STYP_TEXT | STYP_BSS)))
 313           {
 314             if (bias == -1)                /* if first section after bss */
 315               bias = ptr - s->s_scnptr;
 316
 317             s->s_scnptr += bias;
 318             ptr = s->s_scnptr;
 319           }
 320
 321         ptr = ptr + s->s_size;
 322       }
 323   }
 324
 325   /* fix other pointers */
 326   for (scns = 0; scns < f_hdr.f_nscns; scns++)
 327     {
 328       struct scnhdr *s = &section[scns];
 329
 330       if (s->s_relptr != 0)
 331         {
 332           s->s_relptr += bias;
 333         }
 334       if (s->s_lnnoptr != 0)
 335         {
 336           if (lnnoptr == 0) lnnoptr = s->s_lnnoptr;
 337           s->s_lnnoptr += bias;
 338         }
 339     }
 340
 341   if (f_hdr.f_symptr > 0L)
 342     {
 343       f_hdr.f_symptr += bias;
 344     }
 345
 346   text_scnptr = f_thdr->s_scnptr;
 347   data_scnptr = f_dhdr->s_scnptr;
 348   load_scnptr = f_lhdr ? f_lhdr->s_scnptr : 0;
 349
 350   if (write (new, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
 351     {
 352       PERROR (new_name);
 353     }
 354
 355   if (f_hdr.f_opthdr > 0)
 356     {
 357       if (write (new, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
 358         {
 359           PERROR (new_name);
 360         }
 361     }
 362
 363   for (scns = 0; scns < f_hdr.f_nscns; scns++) {
 364     struct scnhdr *s = &section[scns];
 365     if (write (new, s, sizeof (*s)) != sizeof (*s))
 366       {
 367         PERROR (new_name);
 368       }
 369   }
 370
 371   return (0);
 372 }
 373 \f
 374 /* ****************************************************************
 375
 376  *
 377  * Copy the text and data segments from memory to the new a.out
 378  */
 379 static int
 380 copy_text_and_data (int new)
 381 {
 382   char *end;
 383   char *ptr;
 384
 385   lseek (new, text_scnptr, SEEK_SET);
 386   ptr = _text + text_scnptr;
 387   end = ptr + f_ohdr.tsize;
 388   write_segment (new, ptr, end);
 389
 390   lseek (new, data_scnptr, SEEK_SET);
 391   ptr = (char *) f_ohdr.data_start;
 392   end = ptr + f_ohdr.dsize;
 393   write_segment (new, ptr, end);
 394
 395   return 0;
 396 }
 397
 398 #define UnexBlockSz (1<<12)                     /* read/write block size */
 399 static void
 400 write_segment (int new, char *ptr, char *end)
 401 {
 402   int i, nwrite, ret;
 403   char zeros[UnexBlockSz];
 404
 405   for (i = 0; ptr < end;)
 406     {
 407       /* distance to next block.  */
 408       nwrite = (((int) ptr + UnexBlockSz) & -UnexBlockSz) - (int) ptr;
 409       /* But not beyond specified end.  */
 410       if (nwrite > end - ptr) nwrite = end - ptr;
 411       ret = write (new, ptr, nwrite);
 412       /* If write gets a page fault, it means we reached
 413          a gap between the old text segment and the old data segment.
 414          This gap has probably been remapped into part of the text segment.
 415          So write zeros for it.  */
 416       if (ret == -1 && errno == EFAULT)
 417         {
 418           memset (zeros, 0, nwrite);
 419           write (new, zeros, nwrite);
 420         }
 421       else if (nwrite != ret)
 422         {
 423           int write_errno = errno;
 424           char buf[1000];
 425           void *addr = ptr;
 426           sprintf (buf,
 427                    "unexec write failure: addr %p, fileno %d, size 0x%x, wrote 0x%x, errno %d",
 428                    addr, new, nwrite, ret, errno);
 429           errno = write_errno;
 430           PERROR (buf);
 431         }
 432       i += nwrite;
 433       ptr += nwrite;
 434     }
 435 }
 436 \f
 437 /* ****************************************************************
 438  * copy_sym
 439  *
 440  * Copy the relocation information and symbol table from the a.out to the new
 441  */
 442 static int
 443 copy_sym (int new, int a_out, const char *a_name, const char *new_name)
 444 {
 445   char page[UnexBlockSz];
 446   int n;
 447
 448   if (a_out < 0)
 449     return 0;
 450
 451   if (orig_load_scnptr == 0L)
 452     return 0;
 453
 454   if (lnnoptr && lnnoptr < orig_load_scnptr) /* if there is line number info  */
 455     lseek (a_out, lnnoptr, SEEK_SET);  /* start copying from there */
 456   else
 457     lseek (a_out, orig_load_scnptr, SEEK_SET); /* Position a.out to symtab. */
 458
 459   while ((n = read (a_out, page, sizeof page)) > 0)
 460     {
 461       if (write (new, page, n) != n)
 462         {
 463           PERROR (new_name);
 464         }
 465     }
 466   if (n < 0)
 467     {
 468       PERROR (a_name);
 469     }
 470   return 0;
 471 }
 472 \f
 473 /* ****************************************************************
 474  * mark_x
 475  *
 476  * After successfully building the new a.out, mark it executable
 477  */
 478 static void
 479 mark_x (const char *name)
 480 {
 481   struct stat sbuf;
 482   int um;
 483   int new = 0;  /* for PERROR */
 484
 485   um = umask (777);
 486   umask (um);
 487   if (stat (name, &sbuf) == -1)
 488     {
 489       PERROR (name);
 490     }
 491   sbuf.st_mode |= 0111 & ~um;
 492   if (chmod (name, sbuf.st_mode) == -1)
 493     PERROR (name);
 494 }
 495 \f
 496 static int
 497 adjust_lnnoptrs (int writedesc, int readdesc, const char *new_name)
 498 {
 499   int nsyms;
 500   int naux;
 501   int new;
 502   struct syment symentry;
 503   union auxent auxentry;
 504
 505   if (!lnnoptr || !f_hdr.f_symptr)
 506     return 0;
 507
 508   if ((new = open (new_name, O_RDWR)) < 0)
 509     {
 510       PERROR (new_name);
 511       return -1;
 512     }
 513
 514   lseek (new, f_hdr.f_symptr, SEEK_SET);
 515   for (nsyms = 0; nsyms < f_hdr.f_nsyms; nsyms++)
 516     {
 517       read (new, &symentry, SYMESZ);
 518       if (symentry.n_sclass == C_BINCL || symentry.n_sclass == C_EINCL)
 519         {
 520           symentry.n_value += bias;
 521           lseek (new, -SYMESZ, SEEK_CUR);
 522           write (new, &symentry, SYMESZ);
 523         }
 524
 525       for (naux = symentry.n_numaux; naux-- != 0; )
 526         {
 527           read (new, &auxentry, AUXESZ);
 528           nsyms++;
 529           if (naux != 0              /* skip csect auxentry (last entry) */
 530               && (symentry.n_sclass == C_EXT || symentry.n_sclass == C_HIDEXT))
 531             {
 532               auxentry.x_sym.x_fcnary.x_fcn.x_lnnoptr += bias;
 533               lseek (new, -AUXESZ, SEEK_CUR);
 534               write (new, &auxentry, AUXESZ);
 535             }
 536         }
 537     }
 538   close (new);
 539
 540   return 0;
 541 }
 542
 543 static int
 544 unrelocate_symbols (int new, int a_out,
 545                     const char *a_name, const char *new_name)
 546 {
 547   int i;
 548   LDHDR ldhdr;
 549   LDREL ldrel;
 550   off_t t_reloc = (intptr_t) _text - f_ohdr.text_start;
 551 #ifndef ALIGN_DATA_RELOC
 552   off_t d_reloc = (intptr_t) _data - f_ohdr.data_start;
 553 #else
 554   /* This worked (and was needed) before AIX 4.2.
 555      I have no idea why. -- Mike */
 556   off_t d_reloc = (intptr_t) _data - ALIGN (f_ohdr.data_start, 2);
 557 #endif
 558   int * p;
 559
 560   if (load_scnptr == 0)
 561     return 0;
 562
 563   lseek (a_out, orig_load_scnptr, SEEK_SET);
 564   if (read (a_out, &ldhdr, sizeof (ldhdr)) != sizeof (ldhdr))
 565     {
 566       PERROR (new_name);
 567     }
 568
 569 #define SYMNDX_TEXT     0
 570 #define SYMNDX_DATA     1
 571 #define SYMNDX_BSS      2
 572
 573   for (i = 0; i < ldhdr.l_nreloc; i++)
 574     {
 575       lseek (a_out,
 576              orig_load_scnptr + LDHDRSZ + LDSYMSZ*ldhdr.l_nsyms + LDRELSZ*i,
 577              SEEK_SET);
 578
 579       if (read (a_out, &ldrel, LDRELSZ) != LDRELSZ)
 580         {
 581           PERROR (a_name);
 582         }
 583
 584       /* move the BSS loader symbols to the DATA segment */
 585       if (ldrel.l_symndx == SYMNDX_BSS)
 586         {
 587           ldrel.l_symndx = SYMNDX_DATA;
 588
 589           lseek (new,
 590                  load_scnptr + LDHDRSZ + LDSYMSZ*ldhdr.l_nsyms + LDRELSZ*i,
 591                  SEEK_SET);
 592
 593           if (write (new, &ldrel, LDRELSZ) != LDRELSZ)
 594             {
 595               PERROR (new_name);
 596             }
 597         }
 598
 599       if (ldrel.l_rsecnm == f_ohdr.o_sndata)
 600         {
 601           int orig_int;
 602
 603           lseek (a_out,
 604                  orig_data_scnptr + (ldrel.l_vaddr - f_ohdr.data_start),
 605                  SEEK_SET);
 606
 607           if (read (a_out, (void *) &orig_int, sizeof (orig_int))
 608               != sizeof (orig_int))
 609             {
 610               PERROR (a_name);
 611             }
 612
 613           p = (int *) (ldrel.l_vaddr + d_reloc);
 614
 615           switch (ldrel.l_symndx) {
 616           case SYMNDX_TEXT:
 617             orig_int = * p - t_reloc;
 618             break;
 619
 620           case SYMNDX_DATA:
 621           case SYMNDX_BSS:
 622             orig_int = * p - d_reloc;
 623             break;
 624           }
 625
 626           if (orig_int != * p)
 627             {
 628               lseek (new,
 629                      data_scnptr + (ldrel.l_vaddr - f_ohdr.data_start),
 630                      SEEK_SET);
 631               if (write (new, (void *) &orig_int, sizeof (orig_int))
 632                   != sizeof (orig_int))
 633                 {
 634                   PERROR (new_name);
 635                 }
 636             }
 637         }
 638     }
 639   return 0;
 640 }