src/unexelf.c

   1 /* Copyright (C) 1985, 1986, 1987, 1988, 1990, 1992
   2    Free Software Foundation, Inc.
   3
   4 This file is part of GNU Emacs.
   5
   6 GNU Emacs is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Emacs is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Emacs; see the file COPYING.  If not, write to
  18 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19 Boston, MA 02111-1307, USA.
  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 /*
  27  * unexec.c - Convert a running program into an a.out file.
  28  *
  29  * Author:      Spencer W. Thomas
  30  *              Computer Science Dept.
  31  *              University of Utah
  32  * Date:        Tue Mar  2 1982
  33  * Modified heavily since then.
  34  *
  35  * Synopsis:
  36  *      unexec (new_name, a_name, data_start, bss_start, entry_address)
  37  *      char *new_name, *a_name;
  38  *      unsigned data_start, bss_start, entry_address;
  39  *
  40  * Takes a snapshot of the program and makes an a.out format file in the
  41  * file named by the string argument new_name.
  42  * If a_name is non-NULL, the symbol table will be taken from the given file.
  43  * On some machines, an existing a_name file is required.
  44  *
  45  * The boundaries within the a.out file may be adjusted with the data_start
  46  * and bss_start arguments.  Either or both may be given as 0 for defaults.
  47  *
  48  * Data_start gives the boundary between the text segment and the data
  49  * segment of the program.  The text segment can contain shared, read-only
  50  * program code and literal data, while the data segment is always unshared
  51  * and unprotected.  Data_start gives the lowest unprotected address.
  52  * The value you specify may be rounded down to a suitable boundary
  53  * as required by the machine you are using.
  54  *
  55  * Specifying zero for data_start means the boundary between text and data
  56  * should not be the same as when the program was loaded.
  57  * If NO_REMAP is defined, the argument data_start is ignored and the
  58  * segment boundaries are never changed.
  59  *
  60  * Bss_start indicates how much of the data segment is to be saved in the
  61  * a.out file and restored when the program is executed.  It gives the lowest
  62  * unsaved address, and is rounded up to a page boundary.  The default when 0
  63  * is given assumes that the entire data segment is to be stored, including
  64  * the previous data and bss as well as any additional storage allocated with
  65  * break (2).
  66  *
  67  * The new file is set up to start at entry_address.
  68  *
  69  * If you make improvements I'd like to get them too.
  70  * harpo!utah-cs!thomas, thomas@Utah-20
  71  *
  72  */
  73
  74 /* Even more heavily modified by james@bigtex.cactus.org of Dell Computer Co.
  75  * ELF support added.
  76  *
  77  * Basic theory: the data space of the running process needs to be
  78  * dumped to the output file.  Normally we would just enlarge the size
  79  * of .data, scooting everything down.  But we can't do that in ELF,
  80  * because there is often something between the .data space and the
  81  * .bss space.
  82  *
  83  * In the temacs dump below, notice that the Global Offset Table
  84  * (.got) and the Dynamic link data (.dynamic) come between .data1 and
  85  * .bss.  It does not work to overlap .data with these fields.
  86  *
  87  * The solution is to create a new .data segment.  This segment is
  88  * filled with data from the current process.  Since the contents of
  89  * various sections refer to sections by index, the new .data segment
  90  * is made the last in the table to avoid changing any existing index.
  91
  92  * This is an example of how the section headers are changed.  "Addr"
  93  * is a process virtual address.  "Offset" is a file offset.
  94
  95 raid:/nfs/raid/src/dist-18.56/src> dump -h temacs
  96
  97 temacs:
  98
  99            **** SECTION HEADER TABLE ****
 100 [No]    Type    Flags   Addr         Offset       Size          Name
 101         Link    Info    Adralgn      Entsize
 102
 103 [1]     1       2       0x80480d4    0xd4         0x13          .interp
 104         0       0       0x1          0
 105
 106 [2]     5       2       0x80480e8    0xe8         0x388         .hash
 107         3       0       0x4          0x4
 108
 109 [3]     11      2       0x8048470    0x470        0x7f0         .dynsym
 110         4       1       0x4          0x10
 111
 112 [4]     3       2       0x8048c60    0xc60        0x3ad         .dynstr
 113         0       0       0x1          0
 114
 115 [5]     9       2       0x8049010    0x1010       0x338         .rel.plt
 116         3       7       0x4          0x8
 117
 118 [6]     1       6       0x8049348    0x1348       0x3           .init
 119         0       0       0x4          0
 120
 121 [7]     1       6       0x804934c    0x134c       0x680         .plt
 122         0       0       0x4          0x4
 123
 124 [8]     1       6       0x80499cc    0x19cc       0x3c56f       .text
 125         0       0       0x4          0
 126
 127 [9]     1       6       0x8085f3c    0x3df3c      0x3           .fini
 128         0       0       0x4          0
 129
 130 [10]    1       2       0x8085f40    0x3df40      0x69c         .rodata
 131         0       0       0x4          0
 132
 133 [11]    1       2       0x80865dc    0x3e5dc      0xd51         .rodata1
 134         0       0       0x4          0
 135
 136 [12]    1       3       0x8088330    0x3f330      0x20afc       .data
 137         0       0       0x4          0
 138
 139 [13]    1       3       0x80a8e2c    0x5fe2c      0x89d         .data1
 140         0       0       0x4          0
 141
 142 [14]    1       3       0x80a96cc    0x606cc      0x1a8         .got
 143         0       0       0x4          0x4
 144
 145 [15]    6       3       0x80a9874    0x60874      0x80          .dynamic
 146         4       0       0x4          0x8
 147
 148 [16]    8       3       0x80a98f4    0x608f4      0x449c        .bss
 149         0       0       0x4          0
 150
 151 [17]    2       0       0            0x608f4      0x9b90        .symtab
 152         18      371     0x4          0x10
 153
 154 [18]    3       0       0            0x6a484      0x8526        .strtab
 155         0       0       0x1          0
 156
 157 [19]    3       0       0            0x729aa      0x93          .shstrtab
 158         0       0       0x1          0
 159
 160 [20]    1       0       0            0x72a3d      0x68b7        .comment
 161         0       0       0x1          0
 162
 163 raid:/nfs/raid/src/dist-18.56/src> dump -h xemacs
 164
 165 xemacs:
 166
 167            **** SECTION HEADER TABLE ****
 168 [No]    Type    Flags   Addr         Offset       Size          Name
 169         Link    Info    Adralgn      Entsize
 170
 171 [1]     1       2       0x80480d4    0xd4         0x13          .interp
 172         0       0       0x1          0
 173
 174 [2]     5       2       0x80480e8    0xe8         0x388         .hash
 175         3       0       0x4          0x4
 176
 177 [3]     11      2       0x8048470    0x470        0x7f0         .dynsym
 178         4       1       0x4          0x10
 179
 180 [4]     3       2       0x8048c60    0xc60        0x3ad         .dynstr
 181         0       0       0x1          0
 182
 183 [5]     9       2       0x8049010    0x1010       0x338         .rel.plt
 184         3       7       0x4          0x8
 185
 186 [6]     1       6       0x8049348    0x1348       0x3           .init
 187         0       0       0x4          0
 188
 189 [7]     1       6       0x804934c    0x134c       0x680         .plt
 190         0       0       0x4          0x4
 191
 192 [8]     1       6       0x80499cc    0x19cc       0x3c56f       .text
 193         0       0       0x4          0
 194
 195 [9]     1       6       0x8085f3c    0x3df3c      0x3           .fini
 196         0       0       0x4          0
 197
 198 [10]    1       2       0x8085f40    0x3df40      0x69c         .rodata
 199         0       0       0x4          0
 200
 201 [11]    1       2       0x80865dc    0x3e5dc      0xd51         .rodata1
 202         0       0       0x4          0
 203
 204 [12]    1       3       0x8088330    0x3f330      0x20afc       .data
 205         0       0       0x4          0
 206
 207 [13]    1       3       0x80a8e2c    0x5fe2c      0x89d         .data1
 208         0       0       0x4          0
 209
 210 [14]    1       3       0x80a96cc    0x606cc      0x1a8         .got
 211         0       0       0x4          0x4
 212
 213 [15]    6       3       0x80a9874    0x60874      0x80          .dynamic
 214         4       0       0x4          0x8
 215
 216 [16]    8       3       0x80c6800    0x7d800      0             .bss
 217         0       0       0x4          0
 218
 219 [17]    2       0       0            0x7d800      0x9b90        .symtab
 220         18      371     0x4          0x10
 221
 222 [18]    3       0       0            0x87390      0x8526        .strtab
 223         0       0       0x1          0
 224
 225 [19]    3       0       0            0x8f8b6      0x93          .shstrtab
 226         0       0       0x1          0
 227
 228 [20]    1       0       0            0x8f949      0x68b7        .comment
 229         0       0       0x1          0
 230
 231 [21]    1       3       0x80a98f4    0x608f4      0x1cf0c       .data
 232         0       0       0x4          0
 233
 234  * This is an example of how the file header is changed.  "Shoff" is
 235  * the section header offset within the file.  Since that table is
 236  * after the new .data section, it is moved.  "Shnum" is the number of
 237  * sections, which we increment.
 238  *
 239  * "Phoff" is the file offset to the program header.  "Phentsize" and
 240  * "Shentsz" are the program and section header entries sizes respectively.
 241  * These can be larger than the apparent struct sizes.
 242
 243 raid:/nfs/raid/src/dist-18.56/src> dump -f temacs
 244
 245 temacs:
 246
 247                     **** ELF HEADER ****
 248 Class        Data       Type         Machine     Version
 249 Entry        Phoff      Shoff        Flags       Ehsize
 250 Phentsize    Phnum      Shentsz      Shnum       Shstrndx
 251
 252 1            1          2            3           1
 253 0x80499cc    0x34       0x792f4      0           0x34
 254 0x20         5          0x28         21          19
 255
 256 raid:/nfs/raid/src/dist-18.56/src> dump -f xemacs
 257
 258 xemacs:
 259
 260                     **** ELF HEADER ****
 261 Class        Data       Type         Machine     Version
 262 Entry        Phoff      Shoff        Flags       Ehsize
 263 Phentsize    Phnum      Shentsz      Shnum       Shstrndx
 264
 265 1            1          2            3           1
 266 0x80499cc    0x34       0x96200      0           0x34
 267 0x20         5          0x28         22          19
 268
 269  * These are the program headers.  "Offset" is the file offset to the
 270  * segment.  "Vaddr" is the memory load address.  "Filesz" is the
 271  * segment size as it appears in the file, and "Memsz" is the size in
 272  * memory.  Below, the third segment is the code and the fourth is the
 273  * data: the difference between Filesz and Memsz is .bss
 274
 275 raid:/nfs/raid/src/dist-18.56/src> dump -o temacs
 276
 277 temacs:
 278  ***** PROGRAM EXECUTION HEADER *****
 279 Type        Offset      Vaddr       Paddr
 280 Filesz      Memsz       Flags       Align
 281
 282 6           0x34        0x8048034   0
 283 0xa0        0xa0        5           0
 284
 285 3           0xd4        0           0
 286 0x13        0           4           0
 287
 288 1           0x34        0x8048034   0
 289 0x3f2f9     0x3f2f9     5           0x1000
 290
 291 1           0x3f330     0x8088330   0
 292 0x215c4     0x25a60     7           0x1000
 293
 294 2           0x60874     0x80a9874   0
 295 0x80        0           7           0
 296
 297 raid:/nfs/raid/src/dist-18.56/src> dump -o xemacs
 298
 299 xemacs:
 300  ***** PROGRAM EXECUTION HEADER *****
 301 Type        Offset      Vaddr       Paddr
 302 Filesz      Memsz       Flags       Align
 303
 304 6           0x34        0x8048034   0
 305 0xa0        0xa0        5           0
 306
 307 3           0xd4        0           0
 308 0x13        0           4           0
 309
 310 1           0x34        0x8048034   0
 311 0x3f2f9     0x3f2f9     5           0x1000
 312
 313 1           0x3f330     0x8088330   0
 314 0x3e4d0     0x3e4d0     7           0x1000
 315
 316 2           0x60874     0x80a9874   0
 317 0x80        0           7           0
 318
 319
 320  */
 321 \f
 322 /* Modified by wtien@urbana.mcd.mot.com of Motorola Inc.
 323  *
 324  * The above mechanism does not work if the unexeced ELF file is being
 325  * re-layout by other applications (such as `strip'). All the applications
 326  * that re-layout the internal of ELF will layout all sections in ascending
 327  * order of their file offsets. After the re-layout, the data2 section will
 328  * still be the LAST section in the section header vector, but its file offset
 329  * is now being pushed far away down, and causes part of it not to be mapped
 330  * in (ie. not covered by the load segment entry in PHDR vector), therefore
 331  * causes the new binary to fail.
 332  *
 333  * The solution is to modify the unexec algorithm to insert the new data2
 334  * section header right before the new bss section header, so their file
 335  * offsets will be in the ascending order. Since some of the section's (all
 336  * sections AFTER the bss section) indexes are now changed, we also need to
 337  * modify some fields to make them point to the right sections. This is done
 338  * by macro PATCH_INDEX. All the fields that need to be patched are:
 339  *
 340  * 1. ELF header e_shstrndx field.
 341  * 2. section header sh_link and sh_info field.
 342  * 3. symbol table entry st_shndx field.
 343  *
 344  * The above example now should look like:
 345
 346            **** SECTION HEADER TABLE ****
 347 [No]    Type    Flags   Addr         Offset       Size          Name
 348         Link    Info    Adralgn      Entsize
 349
 350 [1]     1       2       0x80480d4    0xd4         0x13          .interp
 351         0       0       0x1          0
 352
 353 [2]     5       2       0x80480e8    0xe8         0x388         .hash
 354         3       0       0x4          0x4
 355
 356 [3]     11      2       0x8048470    0x470        0x7f0         .dynsym
 357         4       1       0x4          0x10
 358
 359 [4]     3       2       0x8048c60    0xc60        0x3ad         .dynstr
 360         0       0       0x1          0
 361
 362 [5]     9       2       0x8049010    0x1010       0x338         .rel.plt
 363         3       7       0x4          0x8
 364
 365 [6]     1       6       0x8049348    0x1348       0x3           .init
 366         0       0       0x4          0
 367
 368 [7]     1       6       0x804934c    0x134c       0x680         .plt
 369         0       0       0x4          0x4
 370
 371 [8]     1       6       0x80499cc    0x19cc       0x3c56f       .text
 372         0       0       0x4          0
 373
 374 [9]     1       6       0x8085f3c    0x3df3c      0x3           .fini
 375         0       0       0x4          0
 376
 377 [10]    1       2       0x8085f40    0x3df40      0x69c         .rodata
 378         0       0       0x4          0
 379
 380 [11]    1       2       0x80865dc    0x3e5dc      0xd51         .rodata1
 381         0       0       0x4          0
 382
 383 [12]    1       3       0x8088330    0x3f330      0x20afc       .data
 384         0       0       0x4          0
 385
 386 [13]    1       3       0x80a8e2c    0x5fe2c      0x89d         .data1
 387         0       0       0x4          0
 388
 389 [14]    1       3       0x80a96cc    0x606cc      0x1a8         .got
 390         0       0       0x4          0x4
 391
 392 [15]    6       3       0x80a9874    0x60874      0x80          .dynamic
 393         4       0       0x4          0x8
 394
 395 [16]    1       3       0x80a98f4    0x608f4      0x1cf0c       .data
 396         0       0       0x4          0
 397
 398 [17]    8       3       0x80c6800    0x7d800      0             .bss
 399         0       0       0x4          0
 400
 401 [18]    2       0       0            0x7d800      0x9b90        .symtab
 402         19      371     0x4          0x10
 403
 404 [19]    3       0       0            0x87390      0x8526        .strtab
 405         0       0       0x1          0
 406
 407 [20]    3       0       0            0x8f8b6      0x93          .shstrtab
 408         0       0       0x1          0
 409
 410 [21]    1       0       0            0x8f949      0x68b7        .comment
 411         0       0       0x1          0
 412
 413  */
 414 \f
 415 #include <sys/types.h>
 416 #include <stdio.h>
 417 #include <sys/stat.h>
 418 #include <memory.h>
 419 #include <string.h>
 420 #include <errno.h>
 421 #include <unistd.h>
 422 #include <fcntl.h>
 423 #include <elf.h>
 424 #include <sys/mman.h>
 425
 426 #ifndef emacs
 427 #define fatal(a, b, c) fprintf (stderr, a, b, c), exit (1)
 428 #else
 429 #include "config.h"
 430 extern void fatal (char *, ...);
 431 #endif
 432
 433 #ifndef ELF_BSS_SECTION_NAME
 434 #define ELF_BSS_SECTION_NAME ".bss"
 435 #endif
 436
 437 /* Get the address of a particular section or program header entry,
 438  * accounting for the size of the entries.
 439  */
 440
 441 #define OLD_SECTION_H(n) \
 442      (*(Elf32_Shdr *) ((byte *) old_section_h + old_file_h->e_shentsize * (n)))
 443 #define NEW_SECTION_H(n) \
 444      (*(Elf32_Shdr *) ((byte *) new_section_h + new_file_h->e_shentsize * (n)))
 445 #define OLD_PROGRAM_H(n) \
 446      (*(Elf32_Phdr *) ((byte *) old_program_h + old_file_h->e_phentsize * (n)))
 447 #define NEW_PROGRAM_H(n) \
 448      (*(Elf32_Phdr *) ((byte *) new_program_h + new_file_h->e_phentsize * (n)))
 449
 450 #define PATCH_INDEX(n) \
 451   do { \
 452          if ((int) (n) >= old_bss_index) \
 453            (n)++; } while (0)
 454 typedef unsigned char byte;
 455
 456 /* Round X up to a multiple of Y.  */
 457
 458 int
 459 round_up (x, y)
 460      int x, y;
 461 {
 462   int rem = x % y;
 463   if (rem == 0)
 464     return x;
 465   return x - rem + y;
 466 }
 467
 468 /* ****************************************************************
 469  * unexec
 470  *
 471  * driving logic.
 472  *
 473  * In ELF, this works by replacing the old .bss section with a new
 474  * .data section, and inserting an empty .bss immediately afterwards.
 475  *
 476  */
 477 void
 478 unexec (new_name, old_name, data_start, bss_start, entry_address)
 479      char *new_name, *old_name;
 480      unsigned data_start, bss_start, entry_address;
 481 {
 482   int new_file, old_file, new_file_size;
 483
 484   /* Pointers to the base of the image of the two files. */
 485   caddr_t old_base, new_base;
 486
 487   /* Pointers to the file, program and section headers for the old and new
 488    * files.
 489    */
 490   Elf32_Ehdr *old_file_h, *new_file_h;
 491   Elf32_Phdr *old_program_h, *new_program_h;
 492   Elf32_Shdr *old_section_h, *new_section_h;
 493
 494   /* Point to the section name table in the old file */
 495   char *old_section_names;
 496
 497   Elf32_Addr old_bss_addr, new_bss_addr;
 498   Elf32_Word old_bss_size, new_data2_size;
 499   Elf32_Off  new_data2_offset;
 500   Elf32_Addr new_data2_addr;
 501
 502   int n, nn, old_bss_index, old_data_index, new_data2_index;
 503   struct stat stat_buf;
 504
 505   /* Open the old file & map it into the address space. */
 506
 507   old_file = open (old_name, O_RDONLY);
 508
 509   if (old_file < 0)
 510     fatal ("Can't open %s for reading: errno %d\n", old_name, errno);
 511
 512   if (fstat (old_file, &stat_buf) == -1)
 513     fatal ("Can't fstat (%s): errno %d\n", old_name, errno);
 514
 515   old_base = mmap (0, stat_buf.st_size, PROT_READ, MAP_SHARED, old_file, 0);
 516
 517   if (old_base == (caddr_t) -1)
 518     fatal ("Can't mmap (%s): errno %d\n", old_name, errno);
 519
 520 #ifdef DEBUG
 521   fprintf (stderr, "mmap (%s, %x) -> %x\n", old_name, stat_buf.st_size,
 522            old_base);
 523 #endif
 524
 525   /* Get pointers to headers & section names */
 526
 527   old_file_h = (Elf32_Ehdr *) old_base;
 528   old_program_h = (Elf32_Phdr *) ((byte *) old_base + old_file_h->e_phoff);
 529   old_section_h = (Elf32_Shdr *) ((byte *) old_base + old_file_h->e_shoff);
 530   old_section_names = (char *) old_base
 531     + OLD_SECTION_H (old_file_h->e_shstrndx).sh_offset;
 532
 533   /* Find the old .bss section.  Figure out parameters of the new
 534    * data2 and bss sections.
 535    */
 536
 537   for (old_bss_index = 1; old_bss_index < (int) old_file_h->e_shnum;
 538        old_bss_index++)
 539     {
 540 #ifdef DEBUG
 541       fprintf (stderr, "Looking for .bss - found %s\n",
 542                old_section_names + OLD_SECTION_H (old_bss_index).sh_name);
 543 #endif
 544       if (!strcmp (old_section_names + OLD_SECTION_H (old_bss_index).sh_name,
 545                    ELF_BSS_SECTION_NAME))
 546         break;
 547     }
 548   if (old_bss_index == old_file_h->e_shnum)
 549     fatal ("Can't find .bss in %s.\n", old_name, 0);
 550
 551   old_bss_addr = OLD_SECTION_H (old_bss_index).sh_addr;
 552   old_bss_size = OLD_SECTION_H (old_bss_index).sh_size;
 553 #if defined(emacs) || !defined(DEBUG)
 554   new_bss_addr = (Elf32_Addr) sbrk (0);
 555 #else
 556   new_bss_addr = old_bss_addr + old_bss_size + 0x1234;
 557 #endif
 558   new_data2_addr = old_bss_addr;
 559   new_data2_size = new_bss_addr - old_bss_addr;
 560   new_data2_offset = OLD_SECTION_H (old_bss_index).sh_offset;
 561
 562 #ifdef DEBUG
 563   fprintf (stderr, "old_bss_index %d\n", old_bss_index);
 564   fprintf (stderr, "old_bss_addr %x\n", old_bss_addr);
 565   fprintf (stderr, "old_bss_size %x\n", old_bss_size);
 566   fprintf (stderr, "new_bss_addr %x\n", new_bss_addr);
 567   fprintf (stderr, "new_data2_addr %x\n", new_data2_addr);
 568   fprintf (stderr, "new_data2_size %x\n", new_data2_size);
 569   fprintf (stderr, "new_data2_offset %x\n", new_data2_offset);
 570 #endif
 571
 572   if ((unsigned) new_bss_addr < (unsigned) old_bss_addr + old_bss_size)
 573     fatal (".bss shrank when undumping???\n", 0, 0);
 574
 575   /* Set the output file to the right size and mmap it.  Set
 576    * pointers to various interesting objects.  stat_buf still has
 577    * old_file data.
 578    */
 579
 580   new_file = open (new_name, O_RDWR | O_CREAT, 0666);
 581   if (new_file < 0)
 582     fatal ("Can't creat (%s): errno %d\n", new_name, errno);
 583
 584   new_file_size = stat_buf.st_size + old_file_h->e_shentsize + new_data2_size;
 585
 586   if (ftruncate (new_file, new_file_size))
 587     fatal ("Can't ftruncate (%s): errno %d\n", new_name, errno);
 588
 589 #ifdef UNEXEC_USE_MAP_PRIVATE
 590   new_base = mmap (0, new_file_size, PROT_READ | PROT_WRITE, MAP_PRIVATE,
 591                    new_file, 0);
 592 #else
 593   new_base = mmap (0, new_file_size, PROT_READ | PROT_WRITE, MAP_SHARED,
 594                    new_file, 0);
 595 #endif
 596
 597   if (new_base == (caddr_t) -1)
 598     fatal ("Can't mmap (%s): errno %d\n", new_name, errno);
 599
 600   new_file_h = (Elf32_Ehdr *) new_base;
 601   new_program_h = (Elf32_Phdr *) ((byte *) new_base + old_file_h->e_phoff);
 602   new_section_h = (Elf32_Shdr *)
 603     ((byte *) new_base + old_file_h->e_shoff + new_data2_size);
 604
 605   /* Make our new file, program and section headers as copies of the
 606    * originals.
 607    */
 608
 609   memcpy (new_file_h, old_file_h, old_file_h->e_ehsize);
 610   memcpy (new_program_h, old_program_h,
 611           old_file_h->e_phnum * old_file_h->e_phentsize);
 612
 613   /* Modify the e_shstrndx if necessary. */
 614   PATCH_INDEX (new_file_h->e_shstrndx);
 615
 616   /* Fix up file header.  We'll add one section.  Section header is
 617    * further away now.
 618    */
 619
 620   new_file_h->e_shoff += new_data2_size;
 621   new_file_h->e_shnum += 1;
 622
 623 #ifdef DEBUG
 624   fprintf (stderr, "Old section offset %x\n", old_file_h->e_shoff);
 625   fprintf (stderr, "Old section count %d\n", old_file_h->e_shnum);
 626   fprintf (stderr, "New section offset %x\n", new_file_h->e_shoff);
 627   fprintf (stderr, "New section count %d\n", new_file_h->e_shnum);
 628 #endif
 629
 630   /* Fix up a new program header.  Extend the writable data segment so
 631    * that the bss area is covered too. Find that segment by looking
 632    * for a segment that ends just before the .bss area.  Make sure
 633    * that no segments are above the new .data2.  Put a loop at the end
 634    * to adjust the offset and address of any segment that is above
 635    * data2, just in case we decide to allow this later.
 636    */
 637
 638   for (n = new_file_h->e_phnum - 1; n >= 0; n--)
 639     {
 640       /* Compute maximum of all requirements for alignment of section.  */
 641       int alignment = (NEW_PROGRAM_H (n)).p_align;
 642       if ((OLD_SECTION_H (old_bss_index)).sh_addralign > alignment)
 643         alignment = OLD_SECTION_H (old_bss_index).sh_addralign;
 644
 645       if (NEW_PROGRAM_H (n).p_vaddr + NEW_PROGRAM_H (n).p_filesz > old_bss_addr)
 646         fatal ("Program segment above .bss in %s\n", old_name, 0);
 647
 648       if (NEW_PROGRAM_H (n).p_type == PT_LOAD
 649           && (round_up ((NEW_PROGRAM_H (n)).p_vaddr
 650                         + (NEW_PROGRAM_H (n)).p_filesz,
 651                         alignment)
 652               == round_up (old_bss_addr, alignment)))
 653         break;
 654     }
 655   if (n < 0)
 656     fatal ("Couldn't find segment next to .bss in %s\n", old_name, 0);
 657
 658   NEW_PROGRAM_H (n).p_filesz += new_data2_size;
 659   NEW_PROGRAM_H (n).p_memsz = NEW_PROGRAM_H (n).p_filesz;
 660
 661 #if 0 /* Maybe allow section after data2 - does this ever happen? */
 662   for (n = new_file_h->e_phnum - 1; n >= 0; n--)
 663     {
 664       if (NEW_PROGRAM_H (n).p_vaddr
 665           && NEW_PROGRAM_H (n).p_vaddr >= new_data2_addr)
 666         NEW_PROGRAM_H (n).p_vaddr += new_data2_size - old_bss_size;
 667
 668       if (NEW_PROGRAM_H (n).p_offset >= new_data2_offset)
 669         NEW_PROGRAM_H (n).p_offset += new_data2_size;
 670     }
 671 #endif
 672
 673   /* Fix up section headers based on new .data2 section.  Any section
 674    * whose offset or virtual address is after the new .data2 section
 675    * gets its value adjusted.  .bss size becomes zero and new address
 676    * is set.  data2 section header gets added by copying the existing
 677    * .data header and modifying the offset, address and size.
 678    */
 679   for (old_data_index = 1; old_data_index < (int) old_file_h->e_shnum;
 680        old_data_index++)
 681     if (!strcmp (old_section_names + OLD_SECTION_H (old_data_index).sh_name,
 682                  ".data"))
 683       break;
 684   if (old_data_index == old_file_h->e_shnum)
 685     fatal ("Can't find .data in %s.\n", old_name, 0);
 686
 687   /* Walk through all section headers, insert the new data2 section right
 688      before the new bss section. */
 689   for (n = 1, nn = 1; n < (int) old_file_h->e_shnum; n++, nn++)
 690     {
 691       caddr_t src;
 692       /* If it is bss section, insert the new data2 section before it. */
 693       if (n == old_bss_index)
 694         {
 695           /* Steal the data section header for this data2 section. */
 696           memcpy (&NEW_SECTION_H (nn), &OLD_SECTION_H (old_data_index),
 697                   new_file_h->e_shentsize);
 698
 699           NEW_SECTION_H (nn).sh_addr = new_data2_addr;
 700           NEW_SECTION_H (nn).sh_offset = new_data2_offset;
 701           NEW_SECTION_H (nn).sh_size = new_data2_size;
 702           /* Use the bss section's alignment. This will assure that the
 703              new data2 section always be placed in the same spot as the old
 704              bss section by any other application. */
 705           NEW_SECTION_H (nn).sh_addralign = OLD_SECTION_H (n).sh_addralign;
 706
 707           /* Now copy over what we have in the memory now. */
 708           memcpy (NEW_SECTION_H (nn).sh_offset + new_base,
 709                   (caddr_t) OLD_SECTION_H (n).sh_addr,
 710                   new_data2_size);
 711           nn++;
 712         }
 713
 714       memcpy (&NEW_SECTION_H (nn), &OLD_SECTION_H (n),
 715               old_file_h->e_shentsize);
 716
 717       /* The new bss section's size is zero, and its file offset and virtual
 718          address should be off by NEW_DATA2_SIZE. */
 719       if (n == old_bss_index)
 720         {
 721           /* NN should be `old_bss_index + 1' at this point. */
 722           NEW_SECTION_H (nn).sh_offset += new_data2_size;
 723           NEW_SECTION_H (nn).sh_addr += new_data2_size;
 724           /* Let the new bss section address alignment be the same as the
 725              section address alignment followed the old bss section, so
 726              this section will be placed in exactly the same place. */
 727           NEW_SECTION_H (nn).sh_addralign = OLD_SECTION_H (nn).sh_addralign;
 728           NEW_SECTION_H (nn).sh_size = 0;
 729         }
 730       else
 731         {
 732           /* Any section that was original placed AFTER the bss
 733              section should now be off by NEW_DATA2_SIZE. */
 734           if (NEW_SECTION_H (nn).sh_offset >= new_data2_offset)
 735             NEW_SECTION_H (nn).sh_offset += new_data2_size;
 736           /* Any section that was originally placed after the section
 737              header table should now be off by the size of one section
 738              header table entry.  */
 739           if (NEW_SECTION_H (nn).sh_offset > new_file_h->e_shoff)
 740             NEW_SECTION_H (nn).sh_offset += new_file_h->e_shentsize;
 741         }
 742
 743       /* If any section hdr refers to the section after the new .data
 744          section, make it refer to next one because we have inserted
 745          a new section in between.  */
 746
 747       PATCH_INDEX (NEW_SECTION_H (nn).sh_link);
 748       /* For symbol tables, info is a symbol table index,
 749          so don't change it.  */
 750       if (NEW_SECTION_H (nn).sh_type != SHT_SYMTAB
 751           && NEW_SECTION_H (nn).sh_type != SHT_DYNSYM)
 752         PATCH_INDEX (NEW_SECTION_H (nn).sh_info);
 753
 754       /* Now, start to copy the content of sections.  */
 755       if (NEW_SECTION_H (nn).sh_type == SHT_NULL
 756           || NEW_SECTION_H (nn).sh_type == SHT_NOBITS)
 757         continue;
 758
 759       /* Write out the sections. .data and .data1 (and data2, called
 760          ".data" in the strings table) get copied from the current process
 761          instead of the old file.  */
 762       if (!strcmp (old_section_names + NEW_SECTION_H (n).sh_name, ".data")
 763           || !strcmp ((old_section_names + NEW_SECTION_H (n).sh_name),
 764                       ".data1"))
 765         src = (caddr_t) OLD_SECTION_H (n).sh_addr;
 766       else
 767         src = old_base + OLD_SECTION_H (n).sh_offset;
 768
 769       memcpy (NEW_SECTION_H (nn).sh_offset + new_base, src,
 770               NEW_SECTION_H (nn).sh_size);
 771
 772       /* If it is the symbol table, its st_shndx field needs to be patched.  */
 773       if (NEW_SECTION_H (nn).sh_type == SHT_SYMTAB
 774           || NEW_SECTION_H (nn).sh_type == SHT_DYNSYM)
 775         {
 776           Elf32_Shdr *spt = &NEW_SECTION_H (nn);
 777           unsigned int num = spt->sh_size / spt->sh_entsize;
 778           Elf32_Sym * sym = (Elf32_Sym *) (NEW_SECTION_H (nn).sh_offset +
 779                                            new_base);
 780           for (; num--; sym++)
 781             {
 782               if ((sym->st_shndx == SHN_UNDEF)
 783                   || (sym->st_shndx == SHN_ABS)
 784                   || (sym->st_shndx == SHN_COMMON))
 785                 continue;
 786
 787               PATCH_INDEX (sym->st_shndx);
 788             }
 789         }
 790     }
 791
 792   /* Update the symbol values of _edata and _end.  */
 793   for (n = new_file_h->e_shnum - 1; n; n--)
 794     {
 795       byte *symnames;
 796       Elf32_Sym *symp, *symendp;
 797
 798       if (NEW_SECTION_H (n).sh_type != SHT_DYNSYM
 799           && NEW_SECTION_H (n).sh_type != SHT_SYMTAB)
 800         continue;
 801
 802       symnames = ((byte *) new_base
 803                   + NEW_SECTION_H (NEW_SECTION_H (n).sh_link).sh_offset);
 804       symp = (Elf32_Sym *) (NEW_SECTION_H (n).sh_offset + new_base);
 805       symendp = (Elf32_Sym *) ((byte *)symp + NEW_SECTION_H (n).sh_size);
 806
 807       for (; symp < symendp; symp ++)
 808         if (strcmp ((char *) (symnames + symp->st_name), "_end") == 0
 809             || strcmp ((char *) (symnames + symp->st_name), "_edata") == 0)
 810           memcpy (&symp->st_value, &new_bss_addr, sizeof (new_bss_addr));
 811     }
 812
 813   /* This loop seeks out relocation sections for the data section, so
 814      that it can undo relocations performed by the runtime linker.  */
 815   for (n = new_file_h->e_shnum - 1; n; n--)
 816     {
 817       Elf32_Shdr section = NEW_SECTION_H (n);
 818       switch (section.sh_type) {
 819       default:
 820         break;
 821       case SHT_REL:
 822       case SHT_RELA:
 823         /* This code handles two different size structs, but there should
 824            be no harm in that provided that r_offset is always the first
 825            member.  */
 826         nn = section.sh_info;
 827         if (!strcmp (old_section_names + NEW_SECTION_H (nn).sh_name, ".data")
 828             || !strcmp ((old_section_names + NEW_SECTION_H (nn).sh_name),
 829                         ".data1"))
 830           {
 831             Elf32_Addr offset = NEW_SECTION_H (nn).sh_addr -
 832               NEW_SECTION_H (nn).sh_offset;
 833             caddr_t reloc = old_base + section.sh_offset, end;
 834             for (end = reloc + section.sh_size; reloc < end;
 835                  reloc += section.sh_entsize)
 836               {
 837                 Elf32_Addr addr = ((Elf32_Rel *) reloc)->r_offset - offset;
 838                 memcpy (new_base + addr, old_base + addr, 4);
 839               }
 840           }
 841         break;
 842       }
 843     }
 844
 845 #ifdef UNEXEC_USE_MAP_PRIVATE
 846   if (lseek (new_file, 0, SEEK_SET) == -1)
 847     fatal ("Can't rewind (%s): errno %d\n", new_name, errno);
 848
 849   if (write (new_file, new_base, new_file_size) != new_file_size)
 850     fatal ("Can't write (%s): errno %d\n", new_name, errno);
 851 #endif
 852
 853   /* Close the files and make the new file executable.  */
 854
 855   if (close (old_file))
 856     fatal ("Can't close (%s): errno %d\n", old_name, errno);
 857
 858   if (close (new_file))
 859     fatal ("Can't close (%s): errno %d\n", new_name, errno);
 860
 861   if (stat (new_name, &stat_buf) == -1)
 862     fatal ("Can't stat (%s): errno %d\n", new_name, errno);
 863
 864   n = umask (777);
 865   umask (n);
 866   stat_buf.st_mode |= 0111 & ~n;
 867   if (chmod (new_name, stat_buf.st_mode) == -1)
 868     fatal ("Can't chmod (%s): errno %d\n", new_name, errno);
 869 }