255 lines
7.5 KiB
C
Executable File
255 lines
7.5 KiB
C
Executable File
/*
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* lowmem.c - enable access to low memory globals on Darwin
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*
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* Copyright (c) 2003 Michael Z. Sliczniak
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*
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* Basilisk II (C) 1997-2005 Christian Bauer
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <sys/mman.h>
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#include <fcntl.h>
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#include <errno.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <mach/vm_prot.h>
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#include <mach-o/loader.h>
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#include <mach-o/fat.h>
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static const char progname[] = "lowmem";
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static const char *filename;
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static int do_swap = 0;
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static uint32_t target_uint32(uint32_t value)
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{
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if (do_swap)
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value = OSSwapInt32(value);
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return value;
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}
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void pagezero_32(struct mach_header *machhead)
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{
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struct segment_command *sc_cmd;
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if (target_uint32(machhead->filetype) != MH_EXECUTE) {
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(void)fprintf(stderr, "%s: %s does not appear to be an executable file\n",
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progname, filename);
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exit(1);
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}
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if (machhead->ncmds == 0) {
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(void)fprintf(stderr, "%s: %s does not contain any load commands\n",
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progname, filename);
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exit(1);
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}
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sc_cmd = (void *)&machhead[1];
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if (target_uint32(sc_cmd->cmd) != LC_SEGMENT){
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(void)fprintf(stderr, "%s: load segment not first command in %s\n",
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progname, filename);
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exit(1);
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}
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if (strncmp(sc_cmd->segname, "__PAGEZERO", sizeof (*sc_cmd->segname))) {
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(void)fprintf(stderr, "%s: zero page not first segment in %s\n",
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progname, filename);
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exit(1);
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}
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/* change the permissions */
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sc_cmd->maxprot = target_uint32(VM_PROT_ALL);
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sc_cmd->initprot = target_uint32(VM_PROT_ALL);
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#ifdef MH_PIE
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/* disable pie in header */
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machhead->flags = target_uint32(target_uint32(machhead->flags) & ~MH_PIE);
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#endif
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}
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#if defined(MH_MAGIC_64)
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void pagezero_64(struct mach_header_64 *machhead)
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{
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struct segment_command_64 *sc_cmd;
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if (target_uint32(machhead->filetype) != MH_EXECUTE) {
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(void)fprintf(stderr, "%s: %s does not appear to be an executable file\n",
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progname, filename);
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exit(1);
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}
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if (machhead->ncmds == 0) {
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(void)fprintf(stderr, "%s: %s does not contain any load commands\n",
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progname, filename);
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exit(1);
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}
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sc_cmd = (void *)&machhead[1];
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if (target_uint32(sc_cmd->cmd) != LC_SEGMENT_64) {
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(void)fprintf(stderr, "%s: load segment not first command in %s\n",
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progname, filename);
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exit(1);
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}
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if (strncmp(sc_cmd->segname, "__PAGEZERO", sizeof(*sc_cmd->segname))) {
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(void)fprintf(stderr, "%s: zero page not first segment in %s\n",
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progname, filename);
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exit(1);
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}
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/* change the permissions */
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sc_cmd->maxprot = target_uint32(VM_PROT_ALL);
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sc_cmd->initprot = target_uint32(VM_PROT_ALL);
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}
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#endif
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/*
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* Under Mach there is very little assumed about the memory map of object
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* files. It is the job of the loader to create the initial memory map of an
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* executable. In a Mach-O executable there will be numerous loader commands
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* that the loader must process. Some of these will create the initial memory
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* map used by the executable. Under Darwin the static object file linker,
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* ld, automatically adds the __PAGEZERO segment to all executables. The
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* default size of this segment is the page size of the target system and
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* the initial and maximum permissions are set to allow no access. This is so
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* that all programs fault on a NULL pointer dereference. Arguably this is
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* incorrect and the maximum permissions shoould be rwx so that programs can
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* change this default behavior. Then programs could be written that assume
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* a null string at the null address, which was the convention on some
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* systems. In our case we need to have 8K mapped at zero for the low memory
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* globals and this program modifies the segment load command in the
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* basiliskII executable so that it can be used for data.
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*/
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int
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main(int argc, const char *argv[])
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{
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int fd;
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char *addr;
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size_t file_size;
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struct mach_header *machhead;
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#if defined(MH_MAGIC_64)
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struct mach_header_64 *machhead64;
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#endif
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struct fat_header *fathead;
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struct stat f;
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if (argc != 2) {
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(void)fprintf(stderr, "Usage: %s executable\n", progname);
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exit(1);
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}
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filename = argv[1];
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if (stat(filename, &f)) {
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(void)fprintf(stderr, "%s: could not stat %s: %s\n",
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progname, filename, strerror(errno));
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exit(1);
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}
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file_size = (size_t) f.st_size;
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fd = open(filename, O_RDWR, 0);
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if (fd == -1) {
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(void)fprintf(stderr, "%s: could not open %s: %s\n",
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progname, filename, strerror(errno));
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exit(1);
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}
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/*
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* Size does not really matter, it will be rounded-up to a multiple
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* of the page size automatically.
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*/
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addr = mmap(NULL, file_size, PROT_READ | PROT_WRITE,
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MAP_FILE | MAP_SHARED, fd, 0);
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if (addr == NULL || addr == MAP_FAILED) {
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(void)fprintf(stderr, "%s: could not mmap %s: %s\n",
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progname, filename, strerror(errno));
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exit(1);
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}
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/*
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* Check to see if the Mach-O magic bytes are in the header.
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*/
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machhead = (void *)addr;
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#if defined(MH_MAGIC_64)
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machhead64 = (void *)addr;
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#endif
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fathead = (void *)addr;
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#if defined(MH_MAGIC_64)
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do_swap = machhead->magic == MH_CIGAM || fathead->magic == FAT_CIGAM || machhead64->magic == MH_CIGAM_64;
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#else
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do_swap = machhead->magic == MH_CIGAM || fathead->magic == FAT_CIGAM;
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#endif
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if (target_uint32(machhead->magic) == MH_MAGIC) {
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pagezero_32(machhead);
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#if defined(MH_MAGIC_64)
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} else if (target_uint32(machhead64->magic) == MH_MAGIC_64) {
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pagezero_64(machhead64);
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#endif
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} else if (target_uint32(fathead->magic) == FAT_MAGIC) {
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struct fat_arch *arch = (void *)&fathead[1];
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int saved_swap = do_swap;
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int i;
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for (i = 0; i < target_uint32(fathead->nfat_arch); ++i, ++arch) {
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machhead = (void *)(addr + target_uint32(arch->offset));
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#if defined(MH_MAGIC_64)
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machhead64 = (void *)(addr + target_uint32(arch->offset));
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#endif
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#if defined(MH_MAGIC_64)
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do_swap = machhead->magic == MH_CIGAM || machhead64->magic == MH_CIGAM_64;
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#else
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do_swap = machhead->magic == MH_CIGAM;
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#endif
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if (target_uint32(machhead->magic) == MH_MAGIC) {
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pagezero_32(machhead);
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#if defined(MH_MAGIC_64)
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} else if (target_uint32(machhead64->magic) == MH_MAGIC_64) {
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pagezero_64(machhead64);
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#endif
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} else {
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(void)fprintf(stderr, "%s: %s does not appear to be a Mach-O object file\n",
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progname, filename);
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exit(1);
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}
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do_swap = saved_swap;
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}
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} else {
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(void)fprintf(stderr, "%s: %s does not appear to be a Mach-O object file\n",
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progname, filename);
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exit(1);
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}
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/*
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* We do not make __PAGEZERO 8K in this program because then
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* all of the offsets would be wrong in the object file after
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* this segment. Instead we use the -pagezero_size option
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* to link the executable.
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*/
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if (msync(addr, file_size, MS_SYNC) == -1) {
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(void)fprintf(stderr, "%s: could not sync %s: %s\n",
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progname, filename, strerror(errno));
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exit(1);
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}
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if (munmap(addr, file_size) == -1) {
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(void)fprintf(stderr, "%s: could not unmap %s: %s\n",
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progname, filename, strerror(errno));
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exit(1);
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}
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(void)close(fd);
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exit(0);
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}
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