/* Unexec for Sunos 4 using shared libraries.
Copyright (C) 1990, 1994 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
. */
/* Contributed by Viktor Dukhovni. */
/*
* Unexec for Berkeley a.out format + SUNOS shared libraries
* The unexeced executable contains the __DYNAMIC area from the
* original text file, and then the rest of data + bss + malloced area of
* the current process. (The __DYNAMIC area is at the top of the process
* data segment, we use "data_start" defined externally to mark the start
* of the "real" data segment.)
*
* For programs that want to remap some of the data segment read only
* a run_time_remap is provided. This attempts to remap largest area starting
* and ending on page boundaries between "data_start" and "bndry"
* For this it to figure out where the text file is located. A path search
* is attempted after trying argv[0] and if all fails we simply do not remap
*
* One feature of run_time_remap () is mandatory: reseting the break.
*
* Note that we can no longer map data into the text segment, as this causes
* the __DYNAMIC struct to become read only, breaking the runtime loader.
* Thus we no longer need to mess with a private crt0.c, the standard one
* will do just fine, since environ can live in the writable area between
* __DYNAMIC and data_start, just make sure that pre-crt0.o (the name
* is somewhat abused here) is loaded first!
*
*/
#include
#include
#include
#include
#include
#include
#include
/* Do this after the above #include's in case a configuration file wants
to define things for this file based on what defines. */
#ifdef emacs
#include
#endif
#if defined (SUNOS4) || defined (__FreeBSD__) || defined (__NetBSD__)
#define UNDO_RELOCATION
#endif
#ifdef UNDO_RELOCATION
#include
#endif
#ifdef HAVE_UNISTD_H
#include
#endif
/* NetBSD needs this bit, but SunOS does not have it. */
#ifndef MAP_FILE
#define MAP_FILE 0
#endif
/*
* for programs other than emacs
* define data_start + initialized here, and make sure
* this object is loaded first!
* emacs will define these elsewhere, and load the object containing
* data_start (pre-crt0.o or firstfile.o?) first!
* The custom crt0.o *must not* be loaded!
*/
#ifndef emacs
static int data_start = 0;
static int initialized = 0;
#else
extern int initialized;
extern unsigned data_start;
extern int pureptr;
#endif
extern char *getenv ();
static unsigned brk_value;
static struct exec nhdr;
static int rd_only_len;
static long cookie;
unexec (new_name, a_name, bndry, bss_start, entry)
char *new_name, *a_name;
unsigned bndry, bss_start, entry;
{
int fd, new;
char *old;
struct exec ohdr; /* Allocate on the stack, not needed in the next life */
struct stat stat;
if ((fd = open (a_name, O_RDONLY)) < 0)
{
fprintf (stderr, "%s: open: ", a_name);
perror (a_name);
exit (1);
}
if ((new = open (new_name, O_WRONLY | O_CREAT, 0666)) == -1)
{
fprintf (stderr, "%s: open: ", a_name);
perror (new_name);
exit (1);
}
if ((fstat (fd, &stat) == -1))
{
fprintf (stderr, "%s: ", a_name);
perror ("fstat");
exit (1);
}
old = (char *)mmap (0, stat.st_size, PROT_READ, MAP_FILE|MAP_SHARED, fd, 0);
if (old == (char *)-1)
{
fprintf (stderr, "%s: ", a_name);
perror ("mmap");
exit (1);
}
close (fd);
nhdr = ohdr = (*(struct exec *)old);
/*
* Remember a magic cookie so we know we've got the right binary
* when remapping.
*/
cookie = time (0);
/* Save the break, it is reset to &_end (by ld.so?). */
brk_value = (unsigned) sbrk (0);
/*
* Round up data start to a page boundary (Lose if not a 2 power!)
*/
data_start = ((((int)&data_start) - 1) & ~(N_PAGSIZ (nhdr) - 1)) + N_PAGSIZ (nhdr);
/*
* Round down read only pages to a multiple of the page size
*/
if (bndry)
rd_only_len = ((int)bndry & ~(N_PAGSIZ (nhdr) - 1)) - data_start;
#ifndef emacs
/* Have to do this some time before dumping the data */
initialized = 1;
#endif
/* Handle new data and bss sizes and optional new entry point.
No one actually uses bss_start and entry, but tradition compels
one to support them.
Could complain if bss_start > brk_value,
but the caller is *supposed* to know what she is doing. */
nhdr.a_data = (bss_start ? bss_start : brk_value) - N_DATADDR (nhdr);
nhdr.a_bss = bss_start ? brk_value - bss_start : 0;
if (entry)
nhdr.a_entry = entry;
/*
* Write out the text segment with new header
* Dynamic executables are ZMAGIC with N_TXTOFF==0 and the header
* part of the text segment, but no need to rely on this.
* So write the TEXT first, then go back replace the header.
* Doing it in the other order is less general!
*/
lseek (new, N_TXTOFF (nhdr), L_SET);
write (new, old + N_TXTOFF (ohdr), N_TXTOFF (ohdr) + ohdr.a_text);
lseek (new, 0L, L_SET);
write (new, &nhdr, sizeof (nhdr));
/*
* Write out the head of the old data segment from the file not
* from core, this has the unresolved __DYNAMIC relocation data
* we need to reload
*/
lseek (new, N_DATOFF (nhdr), L_SET);
write (new, old + N_DATOFF (ohdr), (int)&data_start - N_DATADDR (ohdr));
/*
* Copy the rest of the data from core
*/
write (new, &data_start, N_BSSADDR (nhdr) - (int)&data_start);
/*
* Copy the symbol table and line numbers
*/
lseek (new, N_TRELOFF (nhdr), L_SET);
write (new, old + N_TRELOFF (ohdr), stat.st_size - N_TRELOFF (ohdr));
/* Some other BSD systems use this file.
We don't know whether this change is right for them. */
#ifdef UNDO_RELOCATION
/* Undo the relocations done at startup by ld.so.
It will do these relocations again when we start the dumped Emacs.
Doing them twice gives incorrect results. */
{
unsigned long daddr = N_DATADDR (ohdr);
unsigned long rel, erel;
#ifdef SUNOS4
#ifdef SUNOS4_SHARED_LIBRARIES
extern struct link_dynamic _DYNAMIC;
/* SunOS4.x's ld_rel is relative to N_TXTADDR. */
if (!ohdr.a_dynamic)
/* This was statically linked. */
rel = erel = 0;
else if (_DYNAMIC.ld_version < 2)
{
rel = _DYNAMIC.ld_un.ld_1->ld_rel + N_TXTADDR (ohdr);
erel = _DYNAMIC.ld_un.ld_1->ld_hash + N_TXTADDR (ohdr);
}
else
{
rel = _DYNAMIC.ld_un.ld_2->ld_rel + N_TXTADDR (ohdr);
erel = _DYNAMIC.ld_un.ld_2->ld_hash + N_TXTADDR (ohdr);
}
#else /* not SUNOS4_SHARED_LIBRARIES */
rel = erel = 0;
#endif /* not SUNOS4_SHARED_LIBRARIES */
#ifdef sparc
#define REL_INFO_TYPE struct reloc_info_sparc
#else
#define REL_INFO_TYPE struct relocation_info
#endif /* sparc */
#define REL_TARGET_ADDRESS(r) (((REL_INFO_TYPE *)(r))->r_address)
#endif /* SUNOS4 */
#if defined (__FreeBSD__) || defined (__NetBSD__)
extern struct _dynamic _DYNAMIC;
/* FreeBSD's LD_REL is a virtual address itself. */
rel = LD_REL (&_DYNAMIC);
erel = rel + LD_RELSZ (&_DYNAMIC);
#define REL_INFO_TYPE struct relocation_info
#define REL_TARGET_ADDRESS(r) (((REL_INFO_TYPE *)(r))->r_address)
#endif
for (; rel < erel; rel += sizeof (REL_INFO_TYPE))
{
/* This is the virtual address where ld.so will do relocation. */
unsigned long target = REL_TARGET_ADDRESS (rel);
/* This is the offset in the data segment. */
unsigned long segoffset = target - daddr;
/* If it is located below data_start, we have to do nothing here,
because the old data has been already written to the location. */
if (target < (unsigned long)&data_start)
continue;
lseek (new, N_DATOFF (nhdr) + segoffset, L_SET);
write (new, old + N_DATOFF (ohdr) + segoffset, sizeof (unsigned long));
}
}
#endif /* UNDO_RELOCATION */
fchmod (new, 0755);
}
void
run_time_remap (progname)
char *progname;
{
char aout[MAXPATHLEN];
register char *path, *p;
/* Just in case */
if (!initialized)
return;
/* Restore the break */
brk ((char *) brk_value);
/* If nothing to remap: we are done! */
if (rd_only_len == 0)
return;
/*
* Attempt to find the executable
* First try argv[0], will almost always succeed as shells tend to give
* the full path from the hash list rather than using execvp ()
*/
if (is_it (progname))
return;
/*
* If argv[0] is a full path and does not exist, not much sense in
* searching further
*/
if (strchr (progname, '/'))
return;
/*
* Try to search for argv[0] on the PATH
*/
path = getenv ("PATH");
if (path == NULL)
return;
while (*path)
{
/* copy through ':' or end */
for (p = aout; *p = *path; ++p, ++path)
if (*p == ':')
{
++path; /* move past ':' */
break;
}
*p++ = '/';
strcpy (p, progname);
/*
* aout is a candidate full path name
*/
if (is_it (aout))
return;
}
}
is_it (filename)
char *filename;
{
int fd;
long filenames_cookie;
struct exec hdr;
/*
* Open an executable and check for a valid header!
* Can't bcmp the header with what we had, it may have been stripped!
* so we may save looking at non executables with the same name, mostly
* directories.
*/
fd = open (filename, O_RDONLY);
if (fd != -1)
{
if (read (fd, &hdr, sizeof (hdr)) == sizeof (hdr)
&& !N_BADMAG (hdr) && N_DATOFF (hdr) == N_DATOFF (nhdr)
&& N_TRELOFF (hdr) == N_TRELOFF (nhdr))
{
/* compare cookies */
lseek (fd, N_DATOFF (hdr) + (int)&cookie - N_DATADDR (hdr), L_SET);
read (fd, &filenames_cookie, sizeof (filenames_cookie));
if (filenames_cookie == cookie)
{ /* Eureka */
/*
* Do the mapping
* The PROT_EXEC may not be needed, but it is safer this way.
* should the shared library decide to indirect through
* addresses in the data segment not part of __DYNAMIC
*/
mmap ((char *) data_start, rd_only_len, PROT_READ | PROT_EXEC,
MAP_FILE | MAP_SHARED | MAP_FIXED, fd,
N_DATOFF (hdr) + data_start - N_DATADDR (hdr));
close (fd);
return 1;
}
}
close (fd);
}
return 0;
}