src/unexaix.c

   1 /* Dump an executable image.
   2    Copyright (C) 1985, 1986, 1987, 1988, 1999, 2001, 2002, 2003, 2004,
   3                  2005, 2006, 2007, 2008, 2009, 2010  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 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 (new_name, a_name, data_start, bss_start, entry_address)
  35  *      char *new_name, *a_name;
  36  *      unsigned data_start, bss_start, entry_address;
  37  *
  38  * Takes a snapshot of the program and makes an a.out format file in the
  39  * file named by the string argument new_name.
  40  * If a_name is non-NULL, the symbol table will be taken from the given file.
  41  * On some machines, an existing a_name file is required.
  42  *
  43  * data_start and entry_address are ignored.
  44  *
  45  * bss_start indicates how much of the data segment is to be saved in the
  46  * a.out file and restored when the program is executed.  It gives the lowest
  47  * unsaved address, and is rounded up to a page boundary.  The default when 0
  48  * is given assumes that the entire data segment is to be stored, including
  49  * the previous data and bss as well as any additional storage allocated with
  50  * sbrk(2).
  51  *
  52  */
  53
  54 #ifndef emacs
  55 #define PERROR(arg) perror (arg); return -1
  56 #else
  57 #include <config.h>
  58 #define PERROR(file) report_error (file, new)
  59 #endif
  60
  61 #include <a.out.h>
  62 /* Define getpagesize () if the system does not.
  63    Note that this may depend on symbols defined in a.out.h
  64  */
  65 #include "getpagesize.h"
  66
  67 #include <sys/types.h>
  68 #include <stdio.h>
  69 #include <sys/stat.h>
  70 #include <errno.h>
  71 #include <unistd.h>
  72 #include <fcntl.h>
  73
  74 char *start_of_text (void);                     /* Start of text */
  75 extern char *start_of_data (void);              /* Start of initialized data */
  76
  77 extern int _data;
  78 extern int _text;
  79
  80 #include <filehdr.h>
  81 #include <aouthdr.h>
  82 #include <scnhdr.h>
  83 #include <syms.h>
  84
  85 static struct filehdr f_hdr;            /* File header */
  86 static struct aouthdr f_ohdr;           /* Optional file header (a.out) */
  87 static long bias;                       /* Bias to add for growth */
  88 static long lnnoptr;                    /* Pointer to line-number info within file */
  89
  90 static long text_scnptr;
  91 static long data_scnptr;
  92 #define ALIGN(val, pwr) (((val) + ((1L<<(pwr))-1)) & ~((1L<<(pwr))-1))
  93 static long load_scnptr;
  94 static long orig_load_scnptr;
  95 static long orig_data_scnptr;
  96 static int unrelocate_symbols (int, int, char *, char *);
  97
  98 #ifndef MAX_SECTIONS
  99 #define MAX_SECTIONS    10
 100 #endif
 101
 102 static int adjust_lnnoptrs (int, int, char *);
 103
 104 static int pagemask;
 105
 106 #ifdef emacs
 107 #include <setjmp.h>
 108 #include "lisp.h"
 109
 110 static void
 111 report_error (char *file, int fd)
 112 {
 113   if (fd)
 114     close (fd);
 115   report_file_error ("Cannot unexec", Fcons (build_string (file), Qnil));
 116 }
 117 #endif /* emacs */
 118
 119 #define ERROR0(msg) report_error_1 (new, msg, 0, 0); return -1
 120 #define ERROR1(msg,x) report_error_1 (new, msg, x, 0); return -1
 121 #define ERROR2(msg,x,y) report_error_1 (new, msg, x, y); return -1
 122
 123 static void
 124 report_error_1 (int fd, char *msg, int a1, int a2)
 125 {
 126   close (fd);
 127 #ifdef emacs
 128   error (msg, a1, a2);
 129 #else
 130   fprintf (stderr, msg, a1, a2);
 131   fprintf (stderr, "\n");
 132 #endif
 133 }
 134
 135 static int make_hdr (int, int, unsigned, unsigned, unsigned, char *, char *);
 136 static void mark_x (char *);
 137 static int copy_text_and_data (int);
 138 static int copy_sym (int, int, char *, char *);
 139 static void write_segment (int, char *, char *);
 140 \f
 141 /* ****************************************************************
 142  * unexec
 143  *
 144  * driving logic.
 145  */
 146 int unexec (char *new_name, char *a_name,
 147             unsigned data_start,
 148             unsigned bss_start,
 149             unsigned entry_address)
 150 {
 151   int new = -1, a_out = -1;
 152
 153   if (a_name && (a_out = open (a_name, O_RDONLY)) < 0)
 154     {
 155       PERROR (a_name);
 156     }
 157   if ((new = creat (new_name, 0666)) < 0)
 158     {
 159       PERROR (new_name);
 160     }
 161   if (make_hdr (new, a_out,
 162                 data_start, bss_start,
 163                 entry_address,
 164                 a_name, new_name) < 0
 165       || copy_text_and_data (new) < 0
 166       || copy_sym (new, a_out, a_name, new_name) < 0
 167       || adjust_lnnoptrs (new, a_out, new_name) < 0
 168       || unrelocate_symbols (new, a_out, a_name, new_name) < 0)
 169     {
 170       close (new);
 171       return -1;
 172     }
 173
 174   close (new);
 175   if (a_out >= 0)
 176     close (a_out);
 177   mark_x (new_name);
 178   return 0;
 179 }
 180
 181 /* ****************************************************************
 182  * make_hdr
 183  *
 184  * Make the header in the new a.out from the header in core.
 185  * Modify the text and data sizes.
 186  */
 187 static int
 188 make_hdr (int new, int a_out,
 189           unsigned data_start, unsigned bss_start,
 190           unsigned entry_address,
 191           char *a_name, char *new_name)
 192 {
 193   int scns;
 194   unsigned int bss_end;
 195
 196   struct scnhdr section[MAX_SECTIONS];
 197   struct scnhdr * f_thdr;               /* Text section header */
 198   struct scnhdr * f_dhdr;               /* Data section header */
 199   struct scnhdr * f_bhdr;               /* Bss section header */
 200   struct scnhdr * f_lhdr;               /* Loader section header */
 201   struct scnhdr * f_tchdr;              /* Typechk section header */
 202   struct scnhdr * f_dbhdr;              /* Debug section header */
 203   struct scnhdr * f_xhdr;               /* Except section header */
 204
 205   load_scnptr = orig_load_scnptr = lnnoptr = 0;
 206   pagemask = getpagesize () - 1;
 207
 208   /* Adjust text/data boundary. */
 209   data_start = (long) start_of_data ();
 210   data_start = ADDR_CORRECT (data_start);
 211
 212   data_start = data_start & ~pagemask; /* (Down) to page boundary. */
 213
 214   bss_end = ADDR_CORRECT (sbrk (0)) + pagemask;
 215   bss_end &= ~ pagemask;
 216   /* Adjust data/bss boundary. */
 217   if (bss_start != 0)
 218     {
 219       bss_start = (ADDR_CORRECT (bss_start) + pagemask);
 220       /* (Up) to page bdry. */
 221       bss_start &= ~ pagemask;
 222       if (bss_start > bss_end)
 223         {
 224           ERROR1 ("unexec: Specified bss_start (%u) is past end of program",
 225                   bss_start);
 226         }
 227     }
 228   else
 229     bss_start = bss_end;
 230
 231   if (data_start > bss_start)   /* Can't have negative data size. */
 232     {
 233       ERROR2 ("unexec: data_start (%u) can't be greater than bss_start (%u)",
 234               data_start, bss_start);
 235     }
 236
 237   /* Salvage as much info from the existing file as possible */
 238   f_thdr = NULL; f_dhdr = NULL; f_bhdr = NULL;
 239   f_lhdr = NULL; f_tchdr = NULL; f_dbhdr = NULL; f_xhdr = NULL;
 240   if (a_out >= 0)
 241     {
 242       if (read (a_out, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
 243         {
 244           PERROR (a_name);
 245         }
 246       if (f_hdr.f_opthdr > 0)
 247         {
 248           if (read (a_out, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
 249             {
 250               PERROR (a_name);
 251             }
 252         }
 253       if (f_hdr.f_nscns > MAX_SECTIONS)
 254         {
 255           ERROR0 ("unexec: too many section headers -- increase MAX_SECTIONS");
 256         }
 257       /* Loop through section headers */
 258       for (scns = 0; scns < f_hdr.f_nscns; scns++) {
 259         struct scnhdr *s = &section[scns];
 260         if (read (a_out, s, sizeof (*s)) != sizeof (*s))
 261           {
 262             PERROR (a_name);
 263           }
 264
 265 #define CHECK_SCNHDR(ptr, name, flags) \
 266   if (strcmp(s->s_name, name) == 0) { \
 267     if (s->s_flags != flags) { \
 268       fprintf(stderr, "unexec: %lx flags where %x expected in %s section.\n", \
 269               (unsigned long)s->s_flags, flags, name); \
 270     } \
 271     if (ptr) { \
 272       fprintf(stderr, "unexec: duplicate section header for section %s.\n", \
 273               name); \
 274     } \
 275     ptr = s; \
 276   }
 277         CHECK_SCNHDR(f_thdr, _TEXT, STYP_TEXT);
 278         CHECK_SCNHDR(f_dhdr, _DATA, STYP_DATA);
 279         CHECK_SCNHDR(f_bhdr, _BSS, STYP_BSS);
 280         CHECK_SCNHDR(f_lhdr, _LOADER, STYP_LOADER);
 281         CHECK_SCNHDR(f_dbhdr, _DEBUG,  STYP_DEBUG);
 282         CHECK_SCNHDR(f_tchdr, _TYPCHK,  STYP_TYPCHK);
 283         CHECK_SCNHDR(f_xhdr, _EXCEPT,  STYP_EXCEPT);
 284       }
 285
 286       if (f_thdr == 0)
 287         {
 288           ERROR1 ("unexec: couldn't find \"%s\" section", (int) _TEXT);
 289         }
 290       if (f_dhdr == 0)
 291         {
 292           ERROR1 ("unexec: couldn't find \"%s\" section", (int) _DATA);
 293         }
 294       if (f_bhdr == 0)
 295         {
 296           ERROR1 ("unexec: couldn't find \"%s\" section", (int) _BSS);
 297         }
 298     }
 299   else
 300     {
 301       ERROR0 ("can't build a COFF file from scratch yet");
 302     }
 303   orig_data_scnptr = f_dhdr->s_scnptr;
 304   orig_load_scnptr = f_lhdr ? f_lhdr->s_scnptr : 0;
 305
 306   /* Now we alter the contents of all the f_*hdr variables
 307      to correspond to what we want to dump.  */
 308
 309   /* Indicate that the reloc information is no longer valid for ld (bind);
 310      we only update it enough to fake out the exec-time loader.  */
 311   f_hdr.f_flags |= (F_RELFLG | F_EXEC);
 312
 313   f_ohdr.dsize = bss_start - f_ohdr.data_start;
 314   f_ohdr.bsize = bss_end - bss_start;
 315
 316   f_dhdr->s_size = f_ohdr.dsize;
 317   f_bhdr->s_size = f_ohdr.bsize;
 318   f_bhdr->s_paddr = f_ohdr.data_start + f_ohdr.dsize;
 319   f_bhdr->s_vaddr = f_ohdr.data_start + f_ohdr.dsize;
 320
 321   /* fix scnptr's */
 322   {
 323     ulong ptr = section[0].s_scnptr;
 324
 325     bias = -1;
 326     for (scns = 0; scns < f_hdr.f_nscns; scns++)
 327       {
 328         struct scnhdr *s = &section[scns];
 329
 330         if (s->s_flags & STYP_PAD)        /* .pad sections omitted in AIX 4.1 */
 331           {
 332             /*
 333              * the text_start should probably be o_algntext but that doesn't
 334              * seem to change
 335              */
 336             if (f_ohdr.text_start != 0) /* && scns != 0 */
 337               {
 338                 s->s_size = 512 - (ptr % 512);
 339                 if (s->s_size == 512)
 340                   s->s_size = 0;
 341               }
 342             s->s_scnptr = ptr;
 343           }
 344         else if (s->s_flags & STYP_DATA)
 345           s->s_scnptr = ptr;
 346         else if (!(s->s_flags & (STYP_TEXT | STYP_BSS)))
 347           {
 348             if (bias == -1)                /* if first section after bss */
 349               bias = ptr - s->s_scnptr;
 350
 351             s->s_scnptr += bias;
 352             ptr = s->s_scnptr;
 353           }
 354
 355         ptr = ptr + s->s_size;
 356       }
 357   }
 358
 359   /* fix other pointers */
 360   for (scns = 0; scns < f_hdr.f_nscns; scns++)
 361     {
 362       struct scnhdr *s = &section[scns];
 363
 364       if (s->s_relptr != 0)
 365         {
 366           s->s_relptr += bias;
 367         }
 368       if (s->s_lnnoptr != 0)
 369         {
 370           if (lnnoptr == 0) lnnoptr = s->s_lnnoptr;
 371           s->s_lnnoptr += bias;
 372         }
 373     }
 374
 375   if (f_hdr.f_symptr > 0L)
 376     {
 377       f_hdr.f_symptr += bias;
 378     }
 379
 380   text_scnptr = f_thdr->s_scnptr;
 381   data_scnptr = f_dhdr->s_scnptr;
 382   load_scnptr = f_lhdr ? f_lhdr->s_scnptr : 0;
 383
 384   if (write (new, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
 385     {
 386       PERROR (new_name);
 387     }
 388
 389   if (f_hdr.f_opthdr > 0)
 390     {
 391       if (write (new, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
 392         {
 393           PERROR (new_name);
 394         }
 395     }
 396
 397   for (scns = 0; scns < f_hdr.f_nscns; scns++) {
 398     struct scnhdr *s = &section[scns];
 399     if (write (new, s, sizeof (*s)) != sizeof (*s))
 400       {
 401         PERROR (new_name);
 402       }
 403   }
 404
 405   return (0);
 406 }
 407 \f
 408 /* ****************************************************************
 409
 410  *
 411  * Copy the text and data segments from memory to the new a.out
 412  */
 413 static int
 414 copy_text_and_data (int new)
 415 {
 416   char *end;
 417   char *ptr;
 418
 419   lseek (new, (long) text_scnptr, SEEK_SET);
 420   ptr = start_of_text () + text_scnptr;
 421   end = ptr + f_ohdr.tsize;
 422   write_segment (new, ptr, end);
 423
 424   lseek (new, (long) data_scnptr, SEEK_SET);
 425   ptr = (char *) f_ohdr.data_start;
 426   end = ptr + f_ohdr.dsize;
 427   write_segment (new, ptr, end);
 428
 429   return 0;
 430 }
 431
 432 #define UnexBlockSz (1<<12)                     /* read/write block size */
 433 static void
 434 write_segment (int new, char *ptr, char *end)
 435 {
 436   int i, nwrite, ret;
 437   char buf[80];
 438   char zeros[UnexBlockSz];
 439
 440   for (i = 0; ptr < end;)
 441     {
 442       /* distance to next block.  */
 443       nwrite = (((int) ptr + UnexBlockSz) & -UnexBlockSz) - (int) ptr;
 444       /* But not beyond specified end.  */
 445       if (nwrite > end - ptr) nwrite = end - ptr;
 446       ret = write (new, ptr, nwrite);
 447       /* If write gets a page fault, it means we reached
 448          a gap between the old text segment and the old data segment.
 449          This gap has probably been remapped into part of the text segment.
 450          So write zeros for it.  */
 451       if (ret == -1 && errno == EFAULT)
 452         {
 453           memset (zeros, 0, nwrite);
 454           write (new, zeros, nwrite);
 455         }
 456       else if (nwrite != ret)
 457         {
 458           sprintf (buf,
 459                    "unexec write failure: addr 0x%lx, fileno %d, size 0x%x, wrote 0x%x, errno %d",
 460                    (unsigned long)ptr, new, nwrite, ret, errno);
 461           PERROR (buf);
 462         }
 463       i += nwrite;
 464       ptr += nwrite;
 465     }
 466 }
 467 \f
 468 /* ****************************************************************
 469  * copy_sym
 470  *
 471  * Copy the relocation information and symbol table from the a.out to the new
 472  */
 473 static int
 474 copy_sym (int new, int a_out, char *a_name, char *new_name)
 475 {
 476   char page[UnexBlockSz];
 477   int n;
 478
 479   if (a_out < 0)
 480     return 0;
 481
 482   if (orig_load_scnptr == 0L)
 483     return 0;
 484
 485   if (lnnoptr && lnnoptr < orig_load_scnptr) /* if there is line number info  */
 486     lseek (a_out, lnnoptr, SEEK_SET);  /* start copying from there */
 487   else
 488     lseek (a_out, orig_load_scnptr, SEEK_SET); /* Position a.out to symtab. */
 489
 490   while ((n = read (a_out, page, sizeof page)) > 0)
 491     {
 492       if (write (new, page, n) != n)
 493         {
 494           PERROR (new_name);
 495         }
 496     }
 497   if (n < 0)
 498     {
 499       PERROR (a_name);
 500     }
 501   return 0;
 502 }
 503 \f
 504 /* ****************************************************************
 505  * mark_x
 506  *
 507  * After successfully building the new a.out, mark it executable
 508  */
 509 static void
 510 mark_x (char *name)
 511 {
 512   struct stat sbuf;
 513   int um;
 514   int new = 0;  /* for PERROR */
 515
 516   um = umask (777);
 517   umask (um);
 518   if (stat (name, &sbuf) == -1)
 519     {
 520       PERROR (name);
 521     }
 522   sbuf.st_mode |= 0111 & ~um;
 523   if (chmod (name, sbuf.st_mode) == -1)
 524     PERROR (name);
 525 }
 526 \f
 527 static int
 528 adjust_lnnoptrs (int writedesc, int readdesc, char *new_name)
 529 {
 530   int nsyms;
 531   int naux;
 532   int new;
 533   struct syment symentry;
 534   union auxent auxentry;
 535
 536   if (!lnnoptr || !f_hdr.f_symptr)
 537     return 0;
 538
 539   if ((new = open (new_name, O_RDWR)) < 0)
 540     {
 541       PERROR (new_name);
 542       return -1;
 543     }
 544
 545   lseek (new, f_hdr.f_symptr, SEEK_SET);
 546   for (nsyms = 0; nsyms < f_hdr.f_nsyms; nsyms++)
 547     {
 548       read (new, &symentry, SYMESZ);
 549       if (symentry.n_sclass == C_BINCL || symentry.n_sclass == C_EINCL)
 550         {
 551           symentry.n_value += bias;
 552           lseek (new, -SYMESZ, SEEK_CUR);
 553           write (new, &symentry, SYMESZ);
 554         }
 555
 556       for (naux = symentry.n_numaux; naux-- != 0; )
 557         {
 558           read (new, &auxentry, AUXESZ);
 559           nsyms++;
 560           if (naux != 0              /* skip csect auxentry (last entry) */
 561               && (symentry.n_sclass == C_EXT || symentry.n_sclass == C_HIDEXT))
 562             {
 563               auxentry.x_sym.x_fcnary.x_fcn.x_lnnoptr += bias;
 564               lseek (new, -AUXESZ, SEEK_CUR);
 565               write (new, &auxentry, AUXESZ);
 566             }
 567         }
 568     }
 569   close (new);
 570
 571   return 0;
 572 }
 573
 574 static int
 575 unrelocate_symbols (int new, int a_out, char *a_name, char *new_name)
 576 {
 577   int i;
 578   LDHDR ldhdr;
 579   LDREL ldrel;
 580   ulong t_reloc = (ulong) &_text - f_ohdr.text_start;
 581 #ifndef ALIGN_DATA_RELOC
 582   ulong d_reloc = (ulong) &_data - f_ohdr.data_start;
 583 #else
 584   /* This worked (and was needed) before AIX 4.2.
 585      I have no idea why. -- Mike */
 586   ulong d_reloc = (ulong) &_data - ALIGN(f_ohdr.data_start, 2);
 587 #endif
 588   int * p;
 589
 590   if (load_scnptr == 0)
 591     return 0;
 592
 593   lseek (a_out, orig_load_scnptr, SEEK_SET);
 594   if (read (a_out, &ldhdr, sizeof (ldhdr)) != sizeof (ldhdr))
 595     {
 596       PERROR (new_name);
 597     }
 598
 599 #define SYMNDX_TEXT     0
 600 #define SYMNDX_DATA     1
 601 #define SYMNDX_BSS      2
 602
 603   for (i = 0; i < ldhdr.l_nreloc; i++)
 604     {
 605       lseek (a_out,
 606              orig_load_scnptr + LDHDRSZ + LDSYMSZ*ldhdr.l_nsyms + LDRELSZ*i,
 607              SEEK_SET);
 608
 609       if (read (a_out, &ldrel, LDRELSZ) != LDRELSZ)
 610         {
 611           PERROR (a_name);
 612         }
 613
 614       /* move the BSS loader symbols to the DATA segment */
 615       if (ldrel.l_symndx == SYMNDX_BSS)
 616         {
 617           ldrel.l_symndx = SYMNDX_DATA;
 618
 619           lseek (new,
 620                  load_scnptr + LDHDRSZ + LDSYMSZ*ldhdr.l_nsyms + LDRELSZ*i,
 621                  SEEK_SET);
 622
 623           if (write (new, &ldrel, LDRELSZ) != LDRELSZ)
 624             {
 625               PERROR (new_name);
 626             }
 627         }
 628
 629       if (ldrel.l_rsecnm == f_ohdr.o_sndata)
 630         {
 631           int orig_int;
 632
 633           lseek (a_out,
 634                  orig_data_scnptr + (ldrel.l_vaddr - f_ohdr.data_start),
 635                  SEEK_SET);
 636
 637           if (read (a_out, (void *) &orig_int, sizeof (orig_int))
 638               != sizeof (orig_int))
 639             {
 640               PERROR (a_name);
 641             }
 642
 643           p = (int *) (ldrel.l_vaddr + d_reloc);
 644
 645           switch (ldrel.l_symndx) {
 646           case SYMNDX_TEXT:
 647             orig_int = * p - t_reloc;
 648             break;
 649
 650           case SYMNDX_DATA:
 651           case SYMNDX_BSS:
 652             orig_int = * p - d_reloc;
 653             break;
 654           }
 655
 656           if (orig_int != * p)
 657             {
 658               lseek (new,
 659                      data_scnptr + (ldrel.l_vaddr - f_ohdr.data_start),
 660                      SEEK_SET);
 661               if (write (new, (void *) &orig_int, sizeof (orig_int))
 662                   != sizeof (orig_int))
 663                 {
 664                   PERROR (new_name);
 665                 }
 666             }
 667         }
 668     }
 669   return 0;
 670 }
 671
 672 /*
 673  *      Return the address of the start of the text segment prior to
 674  *      doing an unexec.  After unexec the return value is undefined.
 675  *      See crt0.c for further explanation and _start.
 676  *
 677  */
 678
 679 char *
 680 start_of_text (void)
 681 {
 682   return ((char *) 0x10000000);
 683 }
 684
 685 /* arch-tag: 0783857a-7c2d-456f-a426-58b722d69fd0
 686    (do not change this comment) */