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emacs/src/unexcw.c

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/* unexec() support for Cygwin;
complete rewrite of xemacs Cygwin unexec() code
Copyright (C) 2004-2024 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/>. */
#include <config.h>
#include "unexec.h"
#include "lisp.h"
#include <stdio.h>
#include <fcntl.h>
#include <a.out.h>
#include <unistd.h>
#include <assert.h>
#define DOTEXE ".exe"
/*
** header for Windows executable files
*/
typedef struct
{
FILHDR file_header;
PEAOUTHDR file_optional_header;
SCNHDR section_header[32];
} exe_header_t;
int debug_unexcw = 0;
/*
** Read the header from the executable into memory so we can more easily access it.
*/
static exe_header_t *
read_exe_header (int fd, exe_header_t * exe_header_buffer)
{
int i;
MAYBE_UNUSED int ret;
assert (fd >= 0);
assert (exe_header_buffer != 0);
ret = lseek (fd, 0L, SEEK_SET);
assert (ret != -1);
ret =
read (fd, &exe_header_buffer->file_header,
sizeof (exe_header_buffer->file_header));
assert (ret == sizeof (exe_header_buffer->file_header));
assert (exe_header_buffer->file_header.e_magic == 0x5a4d);
assert (exe_header_buffer->file_header.nt_signature == 0x4550);
#ifdef __x86_64__
assert (exe_header_buffer->file_header.f_magic == 0x8664);
#else
assert (exe_header_buffer->file_header.f_magic == 0x014c);
#endif
assert (exe_header_buffer->file_header.f_nscns > 0);
assert (exe_header_buffer->file_header.f_nscns <=
ARRAYELTS (exe_header_buffer->section_header));
assert (exe_header_buffer->file_header.f_opthdr > 0);
ret =
read (fd, &exe_header_buffer->file_optional_header,
sizeof (exe_header_buffer->file_optional_header));
assert (ret == sizeof (exe_header_buffer->file_optional_header));
#ifdef __x86_64__
assert (exe_header_buffer->file_optional_header.magic == 0x020b);
#else
assert (exe_header_buffer->file_optional_header.magic == 0x010b);
#endif
for (i = 0; i < exe_header_buffer->file_header.f_nscns; ++i)
{
ret =
read (fd, &exe_header_buffer->section_header[i],
sizeof (exe_header_buffer->section_header[i]));
assert (ret == sizeof (exe_header_buffer->section_header[i]));
}
return (exe_header_buffer);
}
/*
** Fix the dumped emacs executable:
**
** - copy .data section data of interest from running executable into
** output .exe file
**
** - convert .bss section into an initialized data section (like
** .data) and copy .bss section data of interest from running
** executable into output .exe file
*/
static void
fixup_executable (int fd)
{
exe_header_t exe_header_buffer;
exe_header_t *exe_header;
int i;
MAYBE_UNUSED int ret;
int found_data = 0;
int found_bss = 0;
exe_header = read_exe_header (fd, &exe_header_buffer);
assert (exe_header != 0);
assert (exe_header->file_header.f_nscns > 0);
for (i = 0; i < exe_header->file_header.f_nscns; ++i)
{
unsigned long start_address =
exe_header->section_header[i].s_vaddr +
exe_header->file_optional_header.ImageBase;
unsigned long end_address =
exe_header->section_header[i].s_vaddr +
exe_header->file_optional_header.ImageBase +
exe_header->section_header[i].s_paddr;
if (debug_unexcw)
printf ("%8s start %#lx end %#lx\n",
exe_header->section_header[i].s_name,
start_address, end_address);
if (my_edata >= (char *) start_address
&& my_edata < (char *) end_address)
{
/* data section */
ret =
lseek (fd, (long) (exe_header->section_header[i].s_scnptr),
SEEK_SET);
assert (ret != -1);
ret =
write (fd, (char *) start_address,
my_edata - (char *) start_address);
assert (ret == my_edata - (char *) start_address);
++found_data;
if (debug_unexcw)
printf (" .data, mem start %#lx mem length %td\n",
start_address, my_edata - (char *) start_address);
if (debug_unexcw)
printf (" .data, file start %d file length %d\n",
(int) exe_header->section_header[i].s_scnptr,
(int) exe_header->section_header[i].s_paddr);
}
else if (my_endbss >= (char *) start_address
&& my_endbss < (char *) end_address)
{
/* bss section */
++found_bss;
if (exe_header->section_header[i].s_flags & 0x00000080)
{
/* convert uninitialized data section to initialized data section */
struct stat statbuf;
ret = fstat (fd, &statbuf);
assert (ret != -1);
exe_header->section_header[i].s_flags &= ~0x00000080;
exe_header->section_header[i].s_flags |= 0x00000040;
exe_header->section_header[i].s_scnptr =
(statbuf.st_size +
exe_header->file_optional_header.FileAlignment) /
exe_header->file_optional_header.FileAlignment *
exe_header->file_optional_header.FileAlignment;
exe_header->section_header[i].s_size =
(exe_header->section_header[i].s_paddr +
exe_header->file_optional_header.FileAlignment) /
exe_header->file_optional_header.FileAlignment *
exe_header->file_optional_header.FileAlignment;
/* Make sure the generated bootstrap binary isn't
* sparse. NT doesn't use a file cache for sparse
* executables, so if we bootstrap Emacs using a sparse
* bootstrap-emacs.exe, bootstrap takes about twenty
* times longer than it would otherwise. */
ret = posix_fallocate (fd,
( exe_header->section_header[i].s_scnptr +
exe_header->section_header[i].s_size ),
1);
assert (ret != -1);
ret =
lseek (fd,
(long) (exe_header->section_header[i].s_scnptr +
exe_header->section_header[i].s_size - 1),
SEEK_SET);
assert (ret != -1);
ret = write (fd, "", 1);
assert (ret == 1);
ret =
lseek (fd,
(long) ((char *) &exe_header->section_header[i] -
(char *) exe_header), SEEK_SET);
assert (ret != -1);
ret =
write (fd, &exe_header->section_header[i],
sizeof (exe_header->section_header[i]));
assert (ret == sizeof (exe_header->section_header[i]));
if (debug_unexcw)
printf (" seek to %ld, write %zu\n",
(long) ((char *) &exe_header->section_header[i] -
(char *) exe_header),
sizeof (exe_header->section_header[i]));
}
/* write initialized data section */
ret =
lseek (fd, (long) (exe_header->section_header[i].s_scnptr),
SEEK_SET);
assert (ret != -1);
ret =
write (fd, (char *) start_address,
my_endbss - (char *) start_address);
assert (ret == (my_endbss - (char *) start_address));
if (debug_unexcw)
printf (" .bss, mem start %#lx mem length %td\n",
start_address, my_endbss - (char *) start_address);
if (debug_unexcw)
printf (" .bss, file start %d file length %d\n",
(int) exe_header->section_header[i].s_scnptr,
(int) exe_header->section_header[i].s_paddr);
}
}
assert (found_bss == 1);
assert (found_data == 1);
}
/*
** Windows likes .exe suffixes on executables.
*/
static char *
add_exe_suffix_if_necessary (const char *name, char *modified)
{
int i = strlen (name);
if (i <= (sizeof (DOTEXE) - 1))
{
sprintf (modified, "%s%s", name, DOTEXE);
}
else if (!strcasecmp (name + i - (sizeof (DOTEXE) - 1), DOTEXE))
{
strcpy (modified, name);
}
else
{
sprintf (modified, "%s%s", name, DOTEXE);
}
return (modified);
}
void
unexec (const char *outfile, const char *infile)
{
char infile_buffer[FILENAME_MAX];
char outfile_buffer[FILENAME_MAX];
int fd_in;
int fd_out;
int ret;
MAYBE_UNUSED int ret2;
infile = add_exe_suffix_if_necessary (infile, infile_buffer);
outfile = add_exe_suffix_if_necessary (outfile, outfile_buffer);
fd_in = emacs_open (infile, O_RDONLY, 0);
assert (fd_in >= 0);
fd_out = emacs_open (outfile, O_RDWR | O_TRUNC | O_CREAT, 0755);
assert (fd_out >= 0);
for (;;)
{
char buffer[4096];
ret = read (fd_in, buffer, sizeof (buffer));
if (ret == 0)
{
/* eof */
break;
}
assert (ret > 0);
/* data */
ret2 = write (fd_out, buffer, ret);
assert (ret2 == ret);
}
ret = emacs_close (fd_in);
assert (ret == 0);
fixup_executable (fd_out);
ret = emacs_close (fd_out);
assert (ret == 0);
}
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