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/* Dump Emacs in Mach-O format for use on macOS.
Copyright (C) 2001-2024 Free Software Foundation, Inc.
This file is part of GNU Emacs.
GNU Emacs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.
GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>. */
/* Contributed by Andrew Choi (akochoi@mac.com). */
/* Documentation note.
Consult the following documents/files for a description of the
Mach-O format: the file loader.h, man pages for Mach-O and ld, old
NEXTSTEP documents of the Mach-O format. The tool otool dumps the
mach header (-h option) and the load commands (-l option) in a
Mach-O file. The tool nm on macOS displays the symbol table in
a Mach-O file. For examples of unexec for the Mach-O format, see
the file unexnext.c in the GNU Emacs distribution, the file
unexdyld.c in the Darwin port of GNU Emacs 20.7, and unexdyld.c in
the Darwin port of XEmacs 21.1. Also the Darwin Libc source
contains the source code for malloc_freezedry and malloc_jumpstart.
Read that to see what they do. This file was written completely
from scratch, making use of information from the above sources. */
/* The macOS implementation of unexec makes use of Darwin's `zone'
memory allocator. All calls to malloc, realloc, and free in Emacs
are redirected to unexec_malloc, unexec_realloc, and unexec_free in
this file. When temacs is run, all memory requests are handled in
the zone EmacsZone. The Darwin memory allocator library calls
maintain the data structures to manage this zone. Dumping writes
its contents to data segments of the executable file. When emacs
is run, the loader recreates the contents of the zone in memory.
However since the initialization routine of the zone memory
allocator is run again, this `zone' can no longer be used as a
heap. That is why emacs uses the ordinary malloc system call to
allocate memory. Also, when a block of memory needs to be
reallocated and the new size is larger than the old one, a new
block must be obtained by malloc and the old contents copied to
it. */
/* Peculiarity of the Mach-O files generated by ld in macOS
(possible causes of future bugs if changed).
The file offset of the start of the __TEXT segment is zero. Since
the Mach header and load commands are located at the beginning of a
Mach-O file, copying the contents of the __TEXT segment from the
input file overwrites them in the output file. Despite this,
unexec works fine as written below because the segment load command
for __TEXT appears, and is therefore processed, before all other
load commands except the segment load command for __PAGEZERO, which
remains unchanged.
Although the file offset of the start of the __TEXT segment is
zero, none of the sections it contains actually start there. In
fact, the earliest one starts a few hundred bytes beyond the end of
the last load command. The linker option -headerpad controls the
minimum size of this padding. Its setting can be changed in
s/darwin.h. A value of 0x690, e.g., leaves room for 30 additional
load commands for the newly created __DATA segments (at 56 bytes
each). Unexec fails if there is not enough room for these new
segments.
The __TEXT segment contains the sections __text, __cstring,
__picsymbol_stub, and __const and the __DATA segment contains the
sections __data, __la_symbol_ptr, __nl_symbol_ptr, __dyld, __bss,
and __common. The other segments do not contain any sections.
These sections are copied from the input file to the output file,
except for __data, __bss, and __common, which are dumped from
memory. The types of the sections __bss and __common are changed
from S_ZEROFILL to S_REGULAR. Note that the number of sections and
their relative order in the input and output files remain
unchanged. Otherwise all n_sect fields in the nlist records in the
symbol table (specified by the LC_SYMTAB load command) will have to
be changed accordingly.
*/
#include <config.h>
/* Although <config.h> redefines malloc to unexec_malloc, etc., this
file wants stdlib.h to declare the originals. */
#undef malloc
#undef realloc
#undef free
#include <stdlib.h>
#include "unexec.h"
#include "lisp.h"
#include "sysstdio.h"
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdint.h>
#include <sys/types.h>
#include <unistd.h>
#include <mach/mach.h>
#include <mach/vm_map.h>
#include <mach-o/loader.h>
#include <mach-o/reloc.h>
#ifdef HAVE_MALLOC_MALLOC_H
#include <malloc/malloc.h>
#else
#include <objc/malloc.h>
#endif
#include <assert.h>
/* LC_DATA_IN_CODE is not defined in mach-o/loader.h on Mac OS X 10.7.
But it is used if we build with "Command Line Tools for Xcode 4.5
(Mac OS X Lion) - September 2012". */
#ifndef LC_DATA_IN_CODE
#define LC_DATA_IN_CODE 0x29 /* table of non-instructions in __text */
#endif
#ifdef _LP64
#define mach_header mach_header_64
#define segment_command segment_command_64
#undef VM_REGION_BASIC_INFO_COUNT
#define VM_REGION_BASIC_INFO_COUNT VM_REGION_BASIC_INFO_COUNT_64
#undef VM_REGION_BASIC_INFO
#define VM_REGION_BASIC_INFO VM_REGION_BASIC_INFO_64
#undef LC_SEGMENT
#define LC_SEGMENT LC_SEGMENT_64
#define vm_region vm_region_64
#define section section_64
#undef MH_MAGIC
#define MH_MAGIC MH_MAGIC_64
#endif
#define VERBOSE 1
/* Size of buffer used to copy data from the input file to the output
file in function unexec_copy. */
#define UNEXEC_COPY_BUFSZ 1024
/* Regions with memory addresses above this value are assumed to be
mapped to dynamically loaded libraries and will not be dumped. */
#define VM_DATA_TOP (20 * 1024 * 1024)
/* Type of an element on the list of regions to be dumped. */
struct region_t {
vm_address_t address;
vm_size_t size;
vm_prot_t protection;
vm_prot_t max_protection;
struct region_t *next;
};
/* Head and tail of the list of regions to be dumped. */
static struct region_t *region_list_head = 0;
static struct region_t *region_list_tail = 0;
/* Pointer to array of load commands. */
static struct load_command **lca;
/* Number of load commands. */
static int nlc;
/* The highest VM address of segments loaded by the input file.
Regions with addresses beyond this are assumed to be allocated
dynamically and thus require dumping. */
static vm_address_t infile_lc_highest_addr = 0;
/* The lowest file offset used by the all sections in the __TEXT
segments. This leaves room at the beginning of the file to store
the Mach-O header. Check this value against header size to ensure
the added load commands for the new __DATA segments did not
overwrite any of the sections in the __TEXT segment. */
static unsigned long text_seg_lowest_offset = 0x10000000;
/* Mach header. */
static struct mach_header mh;
/* Offset at which the next load command should be written. */
static unsigned long curr_header_offset = sizeof (struct mach_header);
/* Offset at which the next segment should be written. */
static unsigned long curr_file_offset = 0;
static unsigned long pagesize;
#define ROUNDUP_TO_PAGE_BOUNDARY(x) (((x) + pagesize - 1) & ~(pagesize - 1))
static int infd, outfd;
static int in_dumped_exec = 0;
static malloc_zone_t *emacs_zone;
/* file offset of input file's data segment */
static off_t data_segment_old_fileoff = 0;
static struct segment_command *data_segment_scp;
/* Read N bytes from infd into memory starting at address DEST.
Return true if successful, false otherwise. */
static int
unexec_read (void *dest, size_t n)
{
return n == read (infd, dest, n);
}
/* Write COUNT bytes from memory starting at address SRC to outfd
starting at offset DEST. Return true if successful, false
otherwise. */
static int
unexec_write (off_t dest, const void *src, size_t count)
{
task_t task = mach_task_self();
if (task == MACH_PORT_NULL || task == MACH_PORT_DEAD)
return false;
if (lseek (outfd, dest, SEEK_SET) != dest)
return 0;
/* We use the Mach virtual memory API to read our process memory
because using src directly would be undefined behavior and fails
under Address Sanitizer. */
bool success = false;
vm_offset_t data;
mach_msg_type_number_t data_count;
if (vm_read (task, (uintptr_t) src, count, &data, &data_count)
== KERN_SUCCESS)
{
success =
write (outfd, (const void *) (uintptr_t) data, data_count) == count;
vm_deallocate (task, data, data_count);
}
return success;
}
/* Write COUNT bytes of zeros to outfd starting at offset DEST.
Return true if successful, false otherwise. */
static int
unexec_write_zero (off_t dest, size_t count)
{
char buf[UNEXEC_COPY_BUFSZ];
ssize_t bytes;
memset (buf, 0, UNEXEC_COPY_BUFSZ);
if (lseek (outfd, dest, SEEK_SET) != dest)
return 0;
while (count > 0)
{
bytes = count > UNEXEC_COPY_BUFSZ ? UNEXEC_COPY_BUFSZ : count;
if (write (outfd, buf, bytes) != bytes)
return 0;
count -= bytes;
}
return 1;
}
/* Copy COUNT bytes from starting offset SRC in infd to starting
offset DEST in outfd. Return true if successful, false
otherwise. */
static int
unexec_copy (off_t dest, off_t src, ssize_t count)
{
ssize_t bytes_read;
ssize_t bytes_to_read;
char buf[UNEXEC_COPY_BUFSZ];
if (lseek (infd, src, SEEK_SET) != src)
return 0;
if (lseek (outfd, dest, SEEK_SET) != dest)
return 0;
while (count > 0)
{
bytes_to_read = count > UNEXEC_COPY_BUFSZ ? UNEXEC_COPY_BUFSZ : count;
bytes_read = read (infd, buf, bytes_to_read);
if (bytes_read <= 0)
return 0;
if (write (outfd, buf, bytes_read) != bytes_read)
return 0;
count -= bytes_read;
}
return 1;
}
/* Debugging and informational messages routines. */
static _Noreturn void
unexec_error (const char *format, ...)
{
va_list ap;
va_start (ap, format);
fputs ("unexec: ", stderr);
vfprintf (stderr, format, ap);
putc ('\n', stderr);
va_end (ap);
exit (1);
}
static void
print_prot (vm_prot_t prot)
{
if (prot == VM_PROT_NONE)
printf ("none");
else
{
putchar (prot & VM_PROT_READ ? 'r' : ' ');
putchar (prot & VM_PROT_WRITE ? 'w' : ' ');
putchar (prot & VM_PROT_EXECUTE ? 'x' : ' ');
putchar (' ');
}
}
static void
print_region (vm_address_t address, vm_size_t size, vm_prot_t prot,
vm_prot_t max_prot)
{
printf ("%#10lx %#8lx ", (long) address, (long) size);
print_prot (prot);
putchar (' ');
print_prot (max_prot);
putchar ('\n');
}
static void
print_region_list (void)
{
struct region_t *r;
printf (" address size prot maxp\n");
for (r = region_list_head; r; r = r->next)
print_region (r->address, r->size, r->protection, r->max_protection);
}
/* Build the list of regions that need to be dumped. Regions with
addresses above VM_DATA_TOP are omitted. Adjacent regions with
identical protection are merged. Note that non-writable regions
cannot be omitted because they some regions created at run time are
read-only. */
static void
build_region_list (void)
{
task_t target_task = mach_task_self ();
vm_address_t address = (vm_address_t) 0;
vm_size_t size;
struct vm_region_basic_info info;
mach_msg_type_number_t info_count = VM_REGION_BASIC_INFO_COUNT;
mach_port_t object_name;
struct region_t *r;
#if VERBOSE
printf ("--- List of All Regions ---\n");
printf (" address size prot maxp\n");
#endif
while (vm_region (target_task, &address, &size, VM_REGION_BASIC_INFO,
(vm_region_info_t) &info, &info_count, &object_name)
== KERN_SUCCESS && info_count == VM_REGION_BASIC_INFO_COUNT)
{
/* Done when we reach addresses of shared libraries, which are
loaded in high memory. */
if (address >= VM_DATA_TOP)
break;
#if VERBOSE
print_region (address, size, info.protection, info.max_protection);
#endif
/* If a region immediately follows the previous one (the one
most recently added to the list) and has identical
protection, merge it with the latter. Otherwise create a
new list element for it. */
if (region_list_tail
&& info.protection == region_list_tail->protection
&& info.max_protection == region_list_tail->max_protection
&& region_list_tail->address + region_list_tail->size == address)
{
region_list_tail->size += size;
}
else
{
r = malloc (sizeof *r);
if (!r)
unexec_error ("cannot allocate region structure");
r->address = address;
r->size = size;
r->protection = info.protection;
r->max_protection = info.max_protection;
r->next = 0;
if (region_list_head == 0)
{
region_list_head = r;
region_list_tail = r;
}
else
{
region_list_tail->next = r;
region_list_tail = r;
}
/* Deallocate (unused) object name returned by
vm_region. */
if (object_name != MACH_PORT_NULL)
mach_port_deallocate (target_task, object_name);
}
address += size;
}
printf ("--- List of Regions to be Dumped ---\n");
print_region_list ();
}
#define MAX_UNEXEC_REGIONS 400
static int num_unexec_regions;
typedef struct {
vm_range_t range;
vm_size_t filesize;
} unexec_region_info;
static unexec_region_info unexec_regions[MAX_UNEXEC_REGIONS];
static void
unexec_regions_recorder (task_t task, void *rr, unsigned type,
vm_range_t *ranges, unsigned num)
{
vm_address_t p;
vm_size_t filesize;
while (num && num_unexec_regions < MAX_UNEXEC_REGIONS)
{
/* Subtract the size of trailing null bytes from filesize. It
can be smaller than vmsize in segment commands. In such a
case, trailing bytes are initialized with zeros. */
for (p = ranges->address + ranges->size; p > ranges->address; p--)
if (*(((char *) p)-1))
break;
filesize = p - ranges->address;
unexec_regions[num_unexec_regions].filesize = filesize;
unexec_regions[num_unexec_regions++].range = *ranges;
printf ("%#10lx (sz: %#8lx/%#8lx)\n", (long) (ranges->address),
(long) filesize, (long) (ranges->size));
ranges++; num--;
}
}
static kern_return_t
unexec_reader (task_t task, vm_address_t address, vm_size_t size, void **ptr)
{
*ptr = (void *) address;
return KERN_SUCCESS;
}
static void
find_emacs_zone_regions (void)
{
num_unexec_regions = 0;
emacs_zone->introspect->enumerator (mach_task_self (), 0,
MALLOC_PTR_REGION_RANGE_TYPE
| MALLOC_ADMIN_REGION_RANGE_TYPE,
(vm_address_t) emacs_zone,
unexec_reader,
unexec_regions_recorder);
if (num_unexec_regions == MAX_UNEXEC_REGIONS)
unexec_error ("find_emacs_zone_regions: too many regions");
}
static int
unexec_regions_sort_compare (const void *a, const void *b)
{
vm_address_t aa = ((unexec_region_info *) a)->range.address;
vm_address_t bb = ((unexec_region_info *) b)->range.address;
if (aa < bb)
return -1;
else if (aa > bb)
return 1;
else
return 0;
}
static void
unexec_regions_merge (void)
{
qsort (unexec_regions, num_unexec_regions, sizeof (unexec_regions[0]),
&unexec_regions_sort_compare);
/* Align each region start address to a page boundary. */
for (unexec_region_info *cur = unexec_regions;
cur < unexec_regions + num_unexec_regions; cur++)
{
vm_size_t padsize = cur->range.address & (pagesize - 1);
if (padsize)
{
cur->range.address -= padsize;
cur->range.size += padsize;
cur->filesize += padsize;
unexec_region_info *prev = cur == unexec_regions ? NULL : cur - 1;
if (prev
&& prev->range.address + prev->range.size > cur->range.address)
{
prev->range.size = cur->range.address - prev->range.address;
if (prev->filesize > prev->range.size)
prev->filesize = prev->range.size;
}
}
}
int n = 0;
unexec_region_info r = unexec_regions[0];
for (int i = 1; i < num_unexec_regions; i++)
{
if (r.range.address + r.range.size == unexec_regions[i].range.address
&& r.range.size - r.filesize < 2 * pagesize)
{
r.filesize = r.range.size + unexec_regions[i].filesize;
r.range.size += unexec_regions[i].range.size;
}
else
{
unexec_regions[n++] = r;
r = unexec_regions[i];
}
}
unexec_regions[n++] = r;
num_unexec_regions = n;
}
/* More informational messages routines. */
static void
print_load_command_name (int lc)
{
switch (lc)
{
case LC_SEGMENT:
#ifndef _LP64
printf ("LC_SEGMENT ");
#else
printf ("LC_SEGMENT_64 ");
#endif
break;
case LC_LOAD_DYLINKER:
printf ("LC_LOAD_DYLINKER ");
break;
case LC_LOAD_DYLIB:
printf ("LC_LOAD_DYLIB ");
break;
case LC_SYMTAB:
printf ("LC_SYMTAB ");
break;
case LC_DYSYMTAB:
printf ("LC_DYSYMTAB ");
break;
case LC_UNIXTHREAD:
printf ("LC_UNIXTHREAD ");
break;
case LC_PREBOUND_DYLIB:
printf ("LC_PREBOUND_DYLIB");
break;
case LC_TWOLEVEL_HINTS:
printf ("LC_TWOLEVEL_HINTS");
break;
#ifdef LC_UUID
case LC_UUID:
printf ("LC_UUID ");
break;
#endif
#ifdef LC_DYLD_INFO
case LC_DYLD_INFO:
printf ("LC_DYLD_INFO ");
break;
case LC_DYLD_INFO_ONLY:
printf ("LC_DYLD_INFO_ONLY");
break;
#endif
#ifdef LC_VERSION_MIN_MACOSX
case LC_VERSION_MIN_MACOSX:
printf ("LC_VERSION_MIN_MACOSX");
break;
#endif
#ifdef LC_FUNCTION_STARTS
case LC_FUNCTION_STARTS:
printf ("LC_FUNCTION_STARTS");
break;
#endif
#ifdef LC_MAIN
case LC_MAIN:
printf ("LC_MAIN ");
break;
#endif
#ifdef LC_DATA_IN_CODE
case LC_DATA_IN_CODE:
printf ("LC_DATA_IN_CODE ");
break;
#endif
#ifdef LC_SOURCE_VERSION
case LC_SOURCE_VERSION:
printf ("LC_SOURCE_VERSION");
break;
#endif
#ifdef LC_DYLIB_CODE_SIGN_DRS
case LC_DYLIB_CODE_SIGN_DRS:
printf ("LC_DYLIB_CODE_SIGN_DRS");
break;
#endif
default:
printf ("unknown ");
}
}
static void
print_load_command (struct load_command *lc)
{
print_load_command_name (lc->cmd);
printf ("%8d", lc->cmdsize);
if (lc->cmd == LC_SEGMENT)
{
struct segment_command *scp;
struct section *sectp;
int j;
scp = (struct segment_command *) lc;
printf (" %-16.16s %#10lx %#8lx\n",
scp->segname, (long) (scp->vmaddr), (long) (scp->vmsize));
sectp = (struct section *) (scp + 1);
for (j = 0; j < scp->nsects; j++)
{
printf (" %-16.16s %#10lx %#8lx\n",
sectp->sectname, (long) (sectp->addr), (long) (sectp->size));
sectp++;
}
}
else
printf ("\n");
}
/* Read header and load commands from input file. Store the latter in
the global array lca. Store the total number of load commands in
global variable nlc. */
static void
read_load_commands (void)
{
int i;
if (!unexec_read (&mh, sizeof (struct mach_header)))
unexec_error ("cannot read mach-o header");
if (mh.magic != MH_MAGIC)
unexec_error ("input file not in Mach-O format");
if (mh.filetype != MH_EXECUTE)
unexec_error ("input Mach-O file is not an executable object file");
#if VERBOSE
printf ("--- Header Information ---\n");
printf ("Magic = 0x%08x\n", mh.magic);
printf ("CPUType = %d\n", mh.cputype);
printf ("CPUSubType = %d\n", mh.cpusubtype);
printf ("FileType = 0x%x\n", mh.filetype);
printf ("NCmds = %d\n", mh.ncmds);
printf ("SizeOfCmds = %d\n", mh.sizeofcmds);
printf ("Flags = 0x%08x\n", mh.flags);
#endif
nlc = mh.ncmds;
lca = malloc (nlc * sizeof *lca);
for (i = 0; i < nlc; i++)
{
struct load_command lc;
/* Load commands are variable-size: so read the command type and
size first and then read the rest. */
if (!unexec_read (&lc, sizeof (struct load_command)))
unexec_error ("cannot read load command");
lca[i] = malloc (lc.cmdsize);
memcpy (lca[i], &lc, sizeof (struct load_command));
if (!unexec_read (lca[i] + 1, lc.cmdsize - sizeof (struct load_command)))
unexec_error ("cannot read content of load command");
if (lc.cmd == LC_SEGMENT)
{
struct segment_command *scp = (struct segment_command *) lca[i];
if (scp->vmaddr + scp->vmsize > infile_lc_highest_addr)
infile_lc_highest_addr = scp->vmaddr + scp->vmsize;
if (strncmp (scp->segname, SEG_TEXT, 16) == 0)
{
struct section *sectp = (struct section *) (scp + 1);
int j;
for (j = 0; j < scp->nsects; j++)
if (sectp->offset < text_seg_lowest_offset)
text_seg_lowest_offset = sectp->offset;
}
}
}
printf ("Highest address of load commands in input file: %#8lx\n",
(unsigned long)infile_lc_highest_addr);
printf ("Lowest offset of all sections in __TEXT segment: %#8lx\n",
text_seg_lowest_offset);
printf ("--- List of Load Commands in Input File ---\n");
printf ("# cmd cmdsize name address size\n");
for (i = 0; i < nlc; i++)
{
printf ("%1d ", i);
print_load_command (lca[i]);
}
}
/* Copy a LC_SEGMENT load command other than the __DATA segment from
the input file to the output file, adjusting the file offset of the
segment and the file offsets of sections contained in it. */
static void
copy_segment (struct load_command *lc)
{
struct segment_command *scp = (struct segment_command *) lc;
unsigned long old_fileoff = scp->fileoff;
struct section *sectp;
int j;
scp->fileoff = curr_file_offset;
sectp = (struct section *) (scp + 1);
for (j = 0; j < scp->nsects; j++)
{
sectp->offset += curr_file_offset - old_fileoff;
sectp++;
}
printf ("Writing segment %-16.16s @ %#8lx (%#8lx/%#8lx @ %#10lx)\n",
scp->segname, (long) (scp->fileoff), (long) (scp->filesize),
(long) (scp->vmsize), (long) (scp->vmaddr));
if (!unexec_copy (scp->fileoff, old_fileoff, scp->filesize))
unexec_error ("cannot copy segment from input to output file");
curr_file_offset += ROUNDUP_TO_PAGE_BOUNDARY (scp->filesize);
if (!unexec_write (curr_header_offset, lc, lc->cmdsize))
unexec_error ("cannot write load command to header");
curr_header_offset += lc->cmdsize;
}
/* Copy a LC_SEGMENT load command for the __DATA segment in the input
file to the output file. We assume that only one such segment load
command exists in the input file and it contains the sections
__data, __bss, __common, __la_symbol_ptr, __nl_symbol_ptr, and
__dyld. The first three of these should be dumped from memory and
the rest should be copied from the input file. Note that the
sections __bss and __common contain no data in the input file
because their flag fields have the value S_ZEROFILL. Dumping these
from memory makes it necessary to adjust file offset fields in
subsequently dumped load commands. Then, create new __DATA segment
load commands for regions on the region list other than the one
corresponding to the __DATA segment in the input file. */
static void
copy_data_segment (struct load_command *lc)
{
struct segment_command *scp = (struct segment_command *) lc;
struct section *sectp;
int j;
unsigned long header_offset, old_file_offset;
/* The new filesize of the segment is set to its vmsize because data
blocks for segments must start at region boundaries. Note that
this may leave unused locations at the end of the segment data
block because the total of the sizes of all sections in the
segment is generally smaller than vmsize. */
scp->filesize = scp->vmsize;
printf ("Writing segment %-16.16s @ %#8lx (%#8lx/%#8lx @ %#10lx)\n",
scp->segname, curr_file_offset, (long)(scp->filesize),
(long)(scp->vmsize), (long) (scp->vmaddr));
/* Offsets in the output file for writing the next section structure
and segment data block, respectively. */
header_offset = curr_header_offset + sizeof (struct segment_command);
sectp = (struct section *) (scp + 1);
for (j = 0; j < scp->nsects; j++)
{
old_file_offset = sectp->offset;
sectp->offset = sectp->addr - scp->vmaddr + curr_file_offset;
/* The __data section is dumped from memory. The __bss and
__common sections are also dumped from memory but their flag
fields require changing (from S_ZEROFILL to S_REGULAR). The
other three kinds of sections are just copied from the input
file. */
if (strncmp (sectp->sectname, SECT_DATA, 16) == 0)
{
unsigned long my_size;
/* The __data section is basically dumped from memory. But
initialized data in statically linked libraries are
copied from the input file. In particular,
add_image_hook.names and add_image_hook.pointers stored
by libarclite_macosx.a, are restored so that they will be
reinitialized when the dumped binary is executed. */
my_size = (unsigned long)my_edata - sectp->addr;
if (!(sectp->addr <= (unsigned long)my_edata
&& my_size <= sectp->size))
unexec_error ("my_edata is not in section %s", SECT_DATA);
if (!unexec_write (sectp->offset, (void *) sectp->addr, my_size))
unexec_error ("cannot write section %s", SECT_DATA);
if (!unexec_copy (sectp->offset + my_size, old_file_offset + my_size,
sectp->size - my_size))
unexec_error ("cannot copy section %s", SECT_DATA);
if (!unexec_write (header_offset, sectp, sizeof (struct section)))
unexec_error ("cannot write section %s's header", SECT_DATA);
}
else if (strncmp (sectp->sectname, SECT_COMMON, 16) == 0)
{
sectp->flags = S_REGULAR;
if (!unexec_write (sectp->offset, (void *) sectp->addr, sectp->size))
unexec_error ("cannot write section %.16s", sectp->sectname);
if (!unexec_write (header_offset, sectp, sizeof (struct section)))
unexec_error ("cannot write section %.16s's header", sectp->sectname);
}
else if (strncmp (sectp->sectname, SECT_BSS, 16) == 0)
{
unsigned long my_size;
sectp->flags = S_REGULAR;
/* Clear uninitialized local variables in statically linked
libraries. In particular, function pointers stored by
libSystemStub.a, which is introduced in Mac OS X 10.4 for
binary compatibility with respect to long double, are
cleared so that they will be reinitialized when the
dumped binary is executed on other versions of OS. */
my_size = (unsigned long)my_endbss_static - sectp->addr;
if (!(sectp->addr <= (unsigned long)my_endbss_static
&& my_size <= sectp->size))
unexec_error ("my_endbss_static is not in section %.16s",
sectp->sectname);
if (!unexec_write (sectp->offset, (void *) sectp->addr, my_size))
unexec_error ("cannot write section %.16s", sectp->sectname);
if (!unexec_write_zero (sectp->offset + my_size,
sectp->size - my_size))
unexec_error ("cannot write section %.16s", sectp->sectname);
if (!unexec_write (header_offset, sectp, sizeof (struct section)))
unexec_error ("cannot write section %.16s's header", sectp->sectname);
}
else if (strncmp (sectp->sectname, "__bss", 5) == 0
|| strncmp (sectp->sectname, "__pu_bss", 8) == 0)
{
sectp->flags = S_REGULAR;
/* These sections are produced by GCC 4.6+.
FIXME: We possibly ought to clear uninitialized local
variables in statically linked libraries like for
SECT_BSS (__bss) above, but setting up the markers we
need in lastfile.c would be rather messy. See
darwin_output_aligned_bss () in gcc/config/darwin.c for
the root of the problem, keeping in mind that the
sections are numbered by their alignment in GCC 4.6, but
by log2(alignment) in GCC 4.7. */
if (!unexec_write (sectp->offset, (void *) sectp->addr, sectp->size))
unexec_error ("cannot copy section %.16s", sectp->sectname);
if (!unexec_write (header_offset, sectp, sizeof (struct section)))
unexec_error ("cannot write section %.16s's header", sectp->sectname);
}
else if (strncmp (sectp->sectname, "__la_symbol_ptr", 16) == 0
|| strncmp (sectp->sectname, "__nl_symbol_ptr", 16) == 0
|| strncmp (sectp->sectname, "__got", 16) == 0
|| strncmp (sectp->sectname, "__la_sym_ptr2", 16) == 0
|| strncmp (sectp->sectname, "__dyld", 16) == 0
|| strncmp (sectp->sectname, "__const", 16) == 0
|| strncmp (sectp->sectname, "__cfstring", 16) == 0
|| strncmp (sectp->sectname, "__gcc_except_tab", 16) == 0
|| strncmp (sectp->sectname, "__program_vars", 16) == 0
|| strncmp (sectp->sectname, "__mod_init_func", 16) == 0
|| strncmp (sectp->sectname, "__mod_term_func", 16) == 0
|| strncmp (sectp->sectname, "__static_data", 16) == 0
|| strncmp (sectp->sectname, "__objc_", 7) == 0)
{
if (!unexec_copy (sectp->offset, old_file_offset, sectp->size))
unexec_error ("cannot copy section %.16s", sectp->sectname);
if (!unexec_write (header_offset, sectp, sizeof (struct section)))
unexec_error ("cannot write section %.16s's header", sectp->sectname);
}
else
unexec_error ("unrecognized section %.16s in __DATA segment",
sectp->sectname);
printf (" section %-16.16s at %#8lx - %#8lx (sz: %#8lx)\n",
sectp->sectname, (long) (sectp->offset),
(long) (sectp->offset + sectp->size), (long) (sectp->size));
header_offset += sizeof (struct section);
sectp++;
}
curr_file_offset += ROUNDUP_TO_PAGE_BOUNDARY (scp->filesize);
if (!unexec_write (curr_header_offset, scp, sizeof (struct segment_command)))
unexec_error ("cannot write header of __DATA segment");
curr_header_offset += lc->cmdsize;
/* Create new __DATA segment load commands for regions on the region
list that do not corresponding to any segment load commands in
the input file.
*/
for (j = 0; j < num_unexec_regions; j++)
{
struct segment_command sc;
sc.cmd = LC_SEGMENT;
sc.cmdsize = sizeof (struct segment_command);
strncpy (sc.segname, SEG_DATA, 16);
sc.vmaddr = unexec_regions[j].range.address;
sc.vmsize = unexec_regions[j].range.size;
sc.fileoff = curr_file_offset;
sc.filesize = unexec_regions[j].filesize;
sc.maxprot = VM_PROT_READ | VM_PROT_WRITE;
sc.initprot = VM_PROT_READ | VM_PROT_WRITE;
sc.nsects = 0;
sc.flags = 0;
printf ("Writing segment %-16.16s @ %#8lx (%#8lx/%#8lx @ %#10lx)\n",
sc.segname, (long) (sc.fileoff), (long) (sc.filesize),
(long) (sc.vmsize), (long) (sc.vmaddr));
if (!unexec_write (sc.fileoff, (void *) sc.vmaddr, sc.filesize))
unexec_error ("cannot write new __DATA segment");
curr_file_offset += ROUNDUP_TO_PAGE_BOUNDARY (sc.filesize);
if (!unexec_write (curr_header_offset, &sc, sc.cmdsize))
unexec_error ("cannot write new __DATA segment's header");
curr_header_offset += sc.cmdsize;
mh.ncmds++;
}
}
/* Copy a LC_SYMTAB load command from the input file to the output
file, adjusting the file offset fields. */
static void
copy_symtab (struct load_command *lc, long delta)
{
struct symtab_command *stp = (struct symtab_command *) lc;
stp->symoff += delta;
stp->stroff += delta;
printf ("Writing LC_SYMTAB command\n");
if (!unexec_write (curr_header_offset, lc, lc->cmdsize))
unexec_error ("cannot write symtab command to header");
curr_header_offset += lc->cmdsize;
}
/* Fix up relocation entries. */
static void
unrelocate (const char *name, off_t reloff, int nrel, vm_address_t base)
{
int i, unreloc_count;
struct relocation_info reloc_info;
struct scattered_relocation_info *sc_reloc_info
= (struct scattered_relocation_info *) &reloc_info;
vm_address_t location;
for (unreloc_count = 0, i = 0; i < nrel; i++)
{
if (lseek (infd, reloff, L_SET) != reloff)
unexec_error ("unrelocate: %s:%d cannot seek to reloc_info", name, i);
if (!unexec_read (&reloc_info, sizeof (reloc_info)))
unexec_error ("unrelocate: %s:%d cannot read reloc_info", name, i);
reloff += sizeof (reloc_info);
if (sc_reloc_info->r_scattered == 0)
switch (reloc_info.r_type)
{
case GENERIC_RELOC_VANILLA:
location = base + reloc_info.r_address;
if (location >= data_segment_scp->vmaddr
&& location < (data_segment_scp->vmaddr
+ data_segment_scp->vmsize))
{
off_t src_off = data_segment_old_fileoff
+ (location - data_segment_scp->vmaddr);
off_t dst_off = data_segment_scp->fileoff
+ (location - data_segment_scp->vmaddr);
if (!unexec_copy (dst_off, src_off, 1 << reloc_info.r_length))
unexec_error ("unrelocate: %s:%d cannot copy original value",
name, i);
unreloc_count++;
}
break;
default:
unexec_error ("unrelocate: %s:%d cannot handle type = %d",
name, i, reloc_info.r_type);
}
else
unexec_error ("unrelocate: %s:%d cannot handle scattered type = %d",
name, i, sc_reloc_info->r_type);
}
if (nrel > 0)
printf ("Fixed up %d/%d %s relocation entries in data segment.\n",
unreloc_count, nrel, name);
}
/* Copy a LC_DYSYMTAB load command from the input file to the output
file, adjusting the file offset fields. */
static void
copy_dysymtab (struct load_command *lc, long delta)
{
struct dysymtab_command *dstp = (struct dysymtab_command *) lc;
vm_address_t base;
#ifdef _LP64
/* First writable segment address. */
base = data_segment_scp->vmaddr;
#else
/* First segment address in the file (unless MH_SPLIT_SEGS set). */
base = 0;
#endif
unrelocate ("local", dstp->locreloff, dstp->nlocrel, base);
unrelocate ("external", dstp->extreloff, dstp->nextrel, base);
if (dstp->nextrel > 0) {
dstp->extreloff += delta;
}
if (dstp->nlocrel > 0) {
dstp->locreloff += delta;
}
if (dstp->nindirectsyms > 0)
dstp->indirectsymoff += delta;
printf ("Writing LC_DYSYMTAB command\n");
if (!unexec_write (curr_header_offset, lc, lc->cmdsize))
unexec_error ("cannot write symtab command to header");
curr_header_offset += lc->cmdsize;
}
/* Copy a LC_TWOLEVEL_HINTS load command from the input file to the output
file, adjusting the file offset fields. */
static void
copy_twolevelhints (struct load_command *lc, long delta)
{
struct twolevel_hints_command *tlhp = (struct twolevel_hints_command *) lc;
if (tlhp->nhints > 0) {
tlhp->offset += delta;
}
printf ("Writing LC_TWOLEVEL_HINTS command\n");
if (!unexec_write (curr_header_offset, lc, lc->cmdsize))
unexec_error ("cannot write two level hint command to header");
curr_header_offset += lc->cmdsize;
}
#ifdef LC_DYLD_INFO
/* Copy a LC_DYLD_INFO(_ONLY) load command from the input file to the output
file, adjusting the file offset fields. */
static void
copy_dyld_info (struct load_command *lc, long delta)
{
struct dyld_info_command *dip = (struct dyld_info_command *) lc;
if (dip->rebase_off > 0)
dip->rebase_off += delta;
if (dip->bind_off > 0)
dip->bind_off += delta;
if (dip->weak_bind_off > 0)
dip->weak_bind_off += delta;
if (dip->lazy_bind_off > 0)
dip->lazy_bind_off += delta;
if (dip->export_off > 0)
dip->export_off += delta;
printf ("Writing ");
print_load_command_name (lc->cmd);
printf (" command\n");
if (!unexec_write (curr_header_offset, lc, lc->cmdsize))
unexec_error ("cannot write dyld info command to header");
curr_header_offset += lc->cmdsize;
}
#endif
#ifdef LC_FUNCTION_STARTS
/* Copy a LC_FUNCTION_STARTS/LC_DATA_IN_CODE/LC_DYLIB_CODE_SIGN_DRS
load command from the input file to the output file, adjusting the
data offset field. */
static void
copy_linkedit_data (struct load_command *lc, long delta)
{
struct linkedit_data_command *ldp = (struct linkedit_data_command *) lc;
if (ldp->dataoff > 0)
ldp->dataoff += delta;
printf ("Writing ");
print_load_command_name (lc->cmd);
printf (" command\n");
if (!unexec_write (curr_header_offset, lc, lc->cmdsize))
unexec_error ("cannot write linkedit data command to header");
curr_header_offset += lc->cmdsize;
}
#endif
/* Copy other kinds of load commands from the input file to the output
file, ones that do not require adjustments of file offsets. */
static void
copy_other (struct load_command *lc)
{
printf ("Writing ");
print_load_command_name (lc->cmd);
printf (" command\n");
if (!unexec_write (curr_header_offset, lc, lc->cmdsize))
unexec_error ("cannot write symtab command to header");
curr_header_offset += lc->cmdsize;
}
/* Loop through all load commands and dump them. Then write the Mach
header. */
static void
dump_it (void)
{
int i;
long linkedit_delta = 0;
printf ("--- Load Commands written to Output File ---\n");
for (i = 0; i < nlc; i++)
switch (lca[i]->cmd)
{
case LC_SEGMENT:
{
struct segment_command *scp = (struct segment_command *) lca[i];
if (strncmp (scp->segname, SEG_DATA, 16) == 0)
{
/* save data segment file offset and segment_command for
unrelocate */
if (data_segment_old_fileoff)
unexec_error ("cannot handle multiple DATA segments"
" in input file");
data_segment_old_fileoff = scp->fileoff;
data_segment_scp = scp;
copy_data_segment (lca[i]);
}
else
{
if (strncmp (scp->segname, SEG_LINKEDIT, 16) == 0)
{
if (linkedit_delta)
unexec_error ("cannot handle multiple LINKEDIT segments"
" in input file");
linkedit_delta = curr_file_offset - scp->fileoff;
}
copy_segment (lca[i]);
}
}
break;
case LC_SYMTAB:
copy_symtab (lca[i], linkedit_delta);
break;
case LC_DYSYMTAB:
copy_dysymtab (lca[i], linkedit_delta);
break;
case LC_TWOLEVEL_HINTS:
copy_twolevelhints (lca[i], linkedit_delta);
break;
#ifdef LC_DYLD_INFO
case LC_DYLD_INFO:
case LC_DYLD_INFO_ONLY:
copy_dyld_info (lca[i], linkedit_delta);
break;
#endif
#ifdef LC_FUNCTION_STARTS
case LC_FUNCTION_STARTS:
#ifdef LC_DATA_IN_CODE
case LC_DATA_IN_CODE:
#endif
#ifdef LC_DYLIB_CODE_SIGN_DRS
case LC_DYLIB_CODE_SIGN_DRS:
#endif
copy_linkedit_data (lca[i], linkedit_delta);
break;
#endif
default:
copy_other (lca[i]);
break;
}
if (curr_header_offset > text_seg_lowest_offset)
unexec_error ("not enough room for load commands for new __DATA segments"
" (increase headerpad_extra in configure.in to at least %lX)",
num_unexec_regions * sizeof (struct segment_command));
printf ("%ld unused bytes follow Mach-O header\n",
text_seg_lowest_offset - curr_header_offset);
mh.sizeofcmds = curr_header_offset - sizeof (struct mach_header);
if (!unexec_write (0, &mh, sizeof (struct mach_header)))
unexec_error ("cannot write final header contents");
}
/* Take a snapshot of Emacs and make a Mach-O format executable file
from it. The file names of the output and input files are outfile
and infile, respectively. The three other parameters are
ignored. */
void
unexec (const char *outfile, const char *infile)
{
if (in_dumped_exec)
unexec_error ("Unexec from a dumped executable is not supported.");
pagesize = getpagesize ();
infd = emacs_open (infile, O_RDONLY, 0);
if (infd < 0)
{
unexec_error ("%s: %s", infile, strerror (errno));
}
outfd = emacs_open (outfile, O_WRONLY | O_TRUNC | O_CREAT, 0777);
if (outfd < 0)
{
emacs_close (infd);
unexec_error ("%s: %s", outfile, strerror (errno));
}
build_region_list ();
read_load_commands ();
find_emacs_zone_regions ();
unexec_regions_merge ();
in_dumped_exec = 1;
dump_it ();
emacs_close (outfd);
}
void
unexec_init_emacs_zone (void)
{
emacs_zone = malloc_create_zone (0, 0);
malloc_set_zone_name (emacs_zone, "EmacsZone");
}
#ifndef MACOSX_MALLOC_MULT16
#define MACOSX_MALLOC_MULT16 1
#endif
typedef struct unexec_malloc_header {
union {
char c[8];
size_t size;
} u;
} unexec_malloc_header_t;
#if MACOSX_MALLOC_MULT16
#define ptr_in_unexec_regions(p) ((((vm_address_t) (p)) & 8) != 0)
#else
int
ptr_in_unexec_regions (void *ptr)
{
int i;
for (i = 0; i < num_unexec_regions; i++)
if ((vm_address_t) ptr - unexec_regions[i].range.address
< unexec_regions[i].range.size)
return 1;
return 0;
}
#endif
void *
unexec_malloc (size_t size)
{
if (in_dumped_exec)
{
void *p;
p = malloc (size);
#if MACOSX_MALLOC_MULT16
assert (((vm_address_t) p % 16) == 0);
#endif
return p;
}
else
{
unexec_malloc_header_t *ptr;
ptr = (unexec_malloc_header_t *)
malloc_zone_malloc (emacs_zone, size + sizeof (unexec_malloc_header_t));
ptr->u.size = size;
ptr++;
#if MACOSX_MALLOC_MULT16
assert (((vm_address_t) ptr % 16) == 8);
#endif
return (void *) ptr;
}
}
void *
unexec_realloc (void *old_ptr, size_t new_size)
{
if (in_dumped_exec)
{
void *p;
if (ptr_in_unexec_regions (old_ptr))
{
size_t old_size = ((unexec_malloc_header_t *) old_ptr)[-1].u.size;
size_t size = new_size > old_size ? old_size : new_size;
p = malloc (new_size);
if (size)
memcpy (p, old_ptr, size);
}
else
{
p = realloc (old_ptr, new_size);
}
#if MACOSX_MALLOC_MULT16
assert (((vm_address_t) p % 16) == 0);
#endif
return p;
}
else
{
unexec_malloc_header_t *ptr;
ptr = (unexec_malloc_header_t *)
malloc_zone_realloc (emacs_zone, (unexec_malloc_header_t *) old_ptr - 1,
new_size + sizeof (unexec_malloc_header_t));
ptr->u.size = new_size;
ptr++;
#if MACOSX_MALLOC_MULT16
assert (((vm_address_t) ptr % 16) == 8);
#endif
return (void *) ptr;
}
}
void
unexec_free (void *ptr)
{
if (ptr == NULL)
return;
if (in_dumped_exec)
{
if (!ptr_in_unexec_regions (ptr))
free (ptr);
}
else
malloc_zone_free (emacs_zone, (unexec_malloc_header_t *) ptr - 1);
}
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