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  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 extern 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 "lisp.h"
 108
 109 static void
 110 report_error (char *file, int fd)
 111 {
 112   if (fd)
 113     close (fd);
 114   report_file_error ("Cannot unexec", Fcons (build_string (file), Qnil));
 115 }
 116 #endif /* emacs */
 117
 118 #define ERROR0(msg) report_error_1 (new, msg, 0, 0); return -1
 119 #define ERROR1(msg,x) report_error_1 (new, msg, x, 0); return -1
 120 #define ERROR2(msg,x,y) report_error_1 (new, msg, x, y); return -1
 121
 122 static void
 123 report_error_1 (int fd, char *msg, int a1, int a2)
 124 {
 125   close (fd);
 126 #ifdef emacs
 127   error (msg, a1, a2);
 128 #else
 129   fprintf (stderr, msg, a1, a2);
 130   fprintf (stderr, "\n");
 131 #endif
 132 }
 133
 134 static int make_hdr (int, int, unsigned, unsigned, unsigned, char *, char *);
 135 static void mark_x (char *);
 136 static int copy_text_and_data (int);
 137 static int copy_sym (int, int, char *, char *);
 138 static void write_segment (int, char *, char *);
 139 \f
 140 /* ****************************************************************
 141  * unexec
 142  *
 143  * driving logic.
 144  */
 145 int unexec (char *new_name, char *a_name,
 146             unsigned data_start,
 147             unsigned bss_start,
 148             unsigned entry_address)
 149 {
 150   int new = -1, a_out = -1;
 151
 152   if (a_name && (a_out = open (a_name, O_RDONLY)) < 0)
 153     {
 154       PERROR (a_name);
 155     }
 156   if ((new = creat (new_name, 0666)) < 0)
 157     {
 158       PERROR (new_name);
 159     }
 160   if (make_hdr (new, a_out,
 161                 data_start, bss_start,
 162                 entry_address,
 163                 a_name, new_name) < 0
 164       || copy_text_and_data (new) < 0
 165       || copy_sym (new, a_out, a_name, new_name) < 0
 166       || adjust_lnnoptrs (new, a_out, new_name) < 0
 167       || unrelocate_symbols (new, a_out, a_name, new_name) < 0)
 168     {
 169       close (new);
 170       return -1;
 171     }
 172
 173   close (new);
 174   if (a_out >= 0)
 175     close (a_out);
 176   mark_x (new_name);
 177   return 0;
 178 }
 179
 180 /* ****************************************************************
 181  * make_hdr
 182  *
 183  * Make the header in the new a.out from the header in core.
 184  * Modify the text and data sizes.
 185  */
 186 static int
 187 make_hdr (int new, int a_out,
 188           unsigned data_start, unsigned bss_start,
 189           unsigned entry_address,
 190           char *a_name, char *new_name)
 191 {
 192   int scns;
 193   unsigned int bss_end;
 194
 195   struct scnhdr section[MAX_SECTIONS];
 196   struct scnhdr * f_thdr;               /* Text section header */
 197   struct scnhdr * f_dhdr;               /* Data section header */
 198   struct scnhdr * f_bhdr;               /* Bss section header */
 199   struct scnhdr * f_lhdr;               /* Loader section header */
 200   struct scnhdr * f_tchdr;              /* Typechk section header */
 201   struct scnhdr * f_dbhdr;              /* Debug section header */
 202   struct scnhdr * f_xhdr;               /* Except section header */
 203
 204   load_scnptr = orig_load_scnptr = lnnoptr = 0;
 205   pagemask = getpagesize () - 1;
 206
 207   /* Adjust text/data boundary. */
 208   data_start = (long) start_of_data ();
 209   data_start = ADDR_CORRECT (data_start);
 210
 211   data_start = data_start & ~pagemask; /* (Down) to page boundary. */
 212
 213   bss_end = ADDR_CORRECT (sbrk (0)) + pagemask;
 214   bss_end &= ~ pagemask;
 215   /* Adjust data/bss boundary. */
 216   if (bss_start != 0)
 217     {
 218       bss_start = (ADDR_CORRECT (bss_start) + pagemask);
 219       /* (Up) to page bdry. */
 220       bss_start &= ~ pagemask;
 221       if (bss_start > bss_end)
 222         {
 223           ERROR1 ("unexec: Specified bss_start (%u) is past end of program",
 224                   bss_start);
 225         }
 226     }
 227   else
 228     bss_start = bss_end;
 229
 230   if (data_start > bss_start)   /* Can't have negative data size. */
 231     {
 232       ERROR2 ("unexec: data_start (%u) can't be greater than bss_start (%u)",
 233               data_start, bss_start);
 234     }
 235
 236   /* Salvage as much info from the existing file as possible */
 237   f_thdr = NULL; f_dhdr = NULL; f_bhdr = NULL;
 238   f_lhdr = NULL; f_tchdr = NULL; f_dbhdr = NULL; f_xhdr = NULL;
 239   if (a_out >= 0)
 240     {
 241       if (read (a_out, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
 242         {
 243           PERROR (a_name);
 244         }
 245       if (f_hdr.f_opthdr > 0)
 246         {
 247           if (read (a_out, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
 248             {
 249               PERROR (a_name);
 250             }
 251         }
 252       if (f_hdr.f_nscns > MAX_SECTIONS)
 253         {
 254           ERROR0 ("unexec: too many section headers -- increase MAX_SECTIONS");
 255         }
 256       /* Loop through section headers */
 257       for (scns = 0; scns < f_hdr.f_nscns; scns++) {
 258         struct scnhdr *s = &section[scns];
 259         if (read (a_out, s, sizeof (*s)) != sizeof (*s))
 260           {
 261             PERROR (a_name);
 262           }
 263
 264 #define CHECK_SCNHDR(ptr, name, flags) \
 265   if (strcmp(s->s_name, name) == 0) { \
 266     if (s->s_flags != flags) { \
 267       fprintf(stderr, "unexec: %lx flags where %x expected in %s section.\n", \
 268               (unsigned long)s->s_flags, flags, name); \
 269     } \
 270     if (ptr) { \
 271       fprintf(stderr, "unexec: duplicate section header for section %s.\n", \
 272               name); \
 273     } \
 274     ptr = s; \
 275   }
 276         CHECK_SCNHDR(f_thdr, _TEXT, STYP_TEXT);
 277         CHECK_SCNHDR(f_dhdr, _DATA, STYP_DATA);
 278         CHECK_SCNHDR(f_bhdr, _BSS, STYP_BSS);
 279         CHECK_SCNHDR(f_lhdr, _LOADER, STYP_LOADER);
 280         CHECK_SCNHDR(f_dbhdr, _DEBUG,  STYP_DEBUG);
 281         CHECK_SCNHDR(f_tchdr, _TYPCHK,  STYP_TYPCHK);
 282         CHECK_SCNHDR(f_xhdr, _EXCEPT,  STYP_EXCEPT);
 283       }
 284
 285       if (f_thdr == 0)
 286         {
 287           ERROR1 ("unexec: couldn't find \"%s\" section", (int) _TEXT);
 288         }
 289       if (f_dhdr == 0)
 290         {
 291           ERROR1 ("unexec: couldn't find \"%s\" section", (int) _DATA);
 292         }
 293       if (f_bhdr == 0)
 294         {
 295           ERROR1 ("unexec: couldn't find \"%s\" section", (int) _BSS);
 296         }
 297     }
 298   else
 299     {
 300       ERROR0 ("can't build a COFF file from scratch yet");
 301     }
 302   orig_data_scnptr = f_dhdr->s_scnptr;
 303   orig_load_scnptr = f_lhdr ? f_lhdr->s_scnptr : 0;
 304
 305   /* Now we alter the contents of all the f_*hdr variables
 306      to correspond to what we want to dump.  */
 307
 308   /* Indicate that the reloc information is no longer valid for ld (bind);
 309      we only update it enough to fake out the exec-time loader.  */
 310   f_hdr.f_flags |= (F_RELFLG | F_EXEC);
 311
 312   f_ohdr.dsize = bss_start - f_ohdr.data_start;
 313   f_ohdr.bsize = bss_end - bss_start;
 314
 315   f_dhdr->s_size = f_ohdr.dsize;
 316   f_bhdr->s_size = f_ohdr.bsize;
 317   f_bhdr->s_paddr = f_ohdr.data_start + f_ohdr.dsize;
 318   f_bhdr->s_vaddr = f_ohdr.data_start + f_ohdr.dsize;
 319
 320   /* fix scnptr's */
 321   {
 322     ulong ptr = section[0].s_scnptr;
 323
 324     bias = -1;
 325     for (scns = 0; scns < f_hdr.f_nscns; scns++)
 326       {
 327         struct scnhdr *s = &section[scns];
 328
 329         if (s->s_flags & STYP_PAD)        /* .pad sections omitted in AIX 4.1 */
 330           {
 331             /*
 332              * the text_start should probably be o_algntext but that doesn't
 333              * seem to change
 334              */
 335             if (f_ohdr.text_start != 0) /* && scns != 0 */
 336               {
 337                 s->s_size = 512 - (ptr % 512);
 338                 if (s->s_size == 512)
 339                   s->s_size = 0;
 340               }
 341             s->s_scnptr = ptr;
 342           }
 343         else if (s->s_flags & STYP_DATA)
 344           s->s_scnptr = ptr;
 345         else if (!(s->s_flags & (STYP_TEXT | STYP_BSS)))
 346           {
 347             if (bias == -1)                /* if first section after bss */
 348               bias = ptr - s->s_scnptr;
 349
 350             s->s_scnptr += bias;
 351             ptr = s->s_scnptr;
 352           }
 353
 354         ptr = ptr + s->s_size;
 355       }
 356   }
 357
 358   /* fix other pointers */
 359   for (scns = 0; scns < f_hdr.f_nscns; scns++)
 360     {
 361       struct scnhdr *s = &section[scns];
 362
 363       if (s->s_relptr != 0)
 364         {
 365           s->s_relptr += bias;
 366         }
 367       if (s->s_lnnoptr != 0)
 368         {
 369           if (lnnoptr == 0) lnnoptr = s->s_lnnoptr;
 370           s->s_lnnoptr += bias;
 371         }
 372     }
 373
 374   if (f_hdr.f_symptr > 0L)
 375     {
 376       f_hdr.f_symptr += bias;
 377     }
 378
 379   text_scnptr = f_thdr->s_scnptr;
 380   data_scnptr = f_dhdr->s_scnptr;
 381   load_scnptr = f_lhdr ? f_lhdr->s_scnptr : 0;
 382
 383   if (write (new, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
 384     {
 385       PERROR (new_name);
 386     }
 387
 388   if (f_hdr.f_opthdr > 0)
 389     {
 390       if (write (new, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
 391         {
 392           PERROR (new_name);
 393         }
 394     }
 395
 396   for (scns = 0; scns < f_hdr.f_nscns; scns++) {
 397     struct scnhdr *s = &section[scns];
 398     if (write (new, s, sizeof (*s)) != sizeof (*s))
 399       {
 400         PERROR (new_name);
 401       }
 402   }
 403
 404   return (0);
 405 }
 406 \f
 407 /* ****************************************************************
 408
 409  *
 410  * Copy the text and data segments from memory to the new a.out
 411  */
 412 static int
 413 copy_text_and_data (int new)
 414 {
 415   char *end;
 416   char *ptr;
 417
 418   lseek (new, (long) text_scnptr, SEEK_SET);
 419   ptr = start_of_text () + text_scnptr;
 420   end = ptr + f_ohdr.tsize;
 421   write_segment (new, ptr, end);
 422
 423   lseek (new, (long) data_scnptr, SEEK_SET);
 424   ptr = (char *) f_ohdr.data_start;
 425   end = ptr + f_ohdr.dsize;
 426   write_segment (new, ptr, end);
 427
 428   return 0;
 429 }
 430
 431 #define UnexBlockSz (1<<12)                     /* read/write block size */
 432 static void
 433 write_segment (int new, char *ptr, char *end)
 434 {
 435   int i, nwrite, ret;
 436   char buf[80];
 437   extern int errno;
 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 /* arch-tag: 0783857a-7c2d-456f-a426-58b722d69fd0
 673    (do not change this comment) */