XEmacs / src / unexfreebsd.c

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/* Code to do an unexec for FreeBSD-1.1 for a temacs linked -Bdynamic.
   Derived from unexnetbsd.c, which was derived from unexsunos4.c
   Copyright (C) 1992, 1993 Free Software Foundation, Inc.

This file is part of XEmacs.

XEmacs 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 2, or (at your option) any
later version.

XEmacs 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 XEmacs; see the file COPYING.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

/* Synched up with: Not in FSF? */

/*
Created 29-Oct-92 by Harlan Sexton
Tweaked 06-Aug-93 by Dean Michaels to work with sun3.
Converted 01-Dec-93 by Paul Mackerras to work with NetBSD shared libraries.
Tweaked 26-Feb-94 by Shawn Carey for use with FreeBSD-1.1 shared libraries.
*/

/********************** Included .h Files **************************/

#include <config.h>

#include <stdarg.h>
#include <sys/param.h>
#include <sys/mman.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <a.out.h>
#include <unistd.h>
#include <ctype.h>
#include <stab.h>
#include <sys/dir.h>
#include <link.h>

/********************** Macros *************************************/

#define SYS_ERR		strerror(errno)

#define MASK_UP(x,p_of_two) \
 ((((unsigned long) (x)) + ((p_of_two) - 1)) & (~((p_of_two) - 1)))

#define MASK_DOWN(x,p_of_two) (((unsigned long) (x)) & (~((p_of_two) - 1)))

/********************** Typedefs and Structs ***********************/

struct translation_struct
{
  long txtaddr;
  long txtoff;
  long dataddr;
  long datoff;
  long bssaddr;
  long endaddr;
};

/********************** Function Prototypes/Declarations ***********/

static void unexec_error (CONST char *m, int use_errno, ...);
static int unexec_open (char *filename, int flag, int mode);
static caddr_t unexec_mmap (int fd, size_t len, int prot, int flags);
static long unexec_seek (int fd, long position);
static void unexec_read (int fd, long position, char *buf, int bytes);
static void unexec_write (int fd, long position, char *buf, int bytes);
static void unexec_pad (int fd, int bytes);
static void unexec_fstat (int fd, struct stat *statptr);
static void unexec_fchmod (int fd, int mode);
static long unexec_addr_to_offset (long addr, struct translation_struct *ts);
static void copy_relocation_site (struct relocation_info *ri, 
                                  caddr_t from_base_addr, 
                                  caddr_t to_base_addr, 
                                  struct translation_struct *ts);
static void reset_symtab (struct nlist *start, struct nlist *end, 
                          char *strtab, long edata_value, long end_value,
                          int shlib_image);
static void reset_ldso_symtab (struct nzlist *start, struct nzlist *end, 
                          char *strtab, long edata_value, long end_value,
                          int shlib_image);
int run_time_remap (char *dummy);

/********************** Variables **********************************/

/* for reporting error messages from system calls */
extern int _DYNAMIC;
extern char **environ;             

static unsigned long sbrk_of_0_at_unexec;
             
/*******************************************************************/

static void
unexec_error (CONST char *fmt, int use_errno, ...)
{
  CONST char *err_msg = SYS_ERR;
  va_list args;

  fprintf (stderr, "unexec - ");
  va_start (args, use_errno);
  vfprintf (stderr, fmt, args);
  va_end (args);

  if (use_errno)
    fprintf (stderr, ": %s", err_msg);
  fprintf (stderr, "\n");
  exit (1);
  return;
}

static int
unexec_open (char *filename, int flag, int mode)
{
  int fd;

  errno = 0;

  fd = open (filename, flag, mode);

  if (fd < 0)
    unexec_error ("Failure opening file %s", 1, filename);
  return fd;
}

static caddr_t
unexec_mmap (int fd, size_t len, int prot, int flags)
{
  caddr_t return_val;

  unexec_seek (fd, 0);
  errno = 0;
  return_val = mmap (0, len, prot, flags, fd, 0);

  if (return_val == (caddr_t) -1)
    unexec_error ("Failure mmap'ing file", 1);
  return return_val;
}


static long
unexec_seek (int fd, long position)
{
  long seek_value;

  if (fd <= 0)
    unexec_error ("No file open in which to seek", 0);

  errno = 0;

  if (position < 0)
    seek_value = (long) lseek (fd, 0, L_INCR);
  else
    seek_value = (long) lseek (fd, position, L_SET);

  if (seek_value < 0)
    unexec_error ("Failed to do a seek to 0x%x in %s", 1,
                  position, "unexec() output file");

  return seek_value;
}

static void
unexec_read (int fd, long position, char *buf, int bytes)
{
  int n_read;
  int remains = bytes;
  position = unexec_seek (fd, position);

  if (bytes < 0)
    unexec_error ("Attempted read of %d bytes", 0, bytes);

  errno = 0;

  while (remains > 0)
    {
      n_read = read (fd, buf, remains);
      if (n_read <= 0)
        unexec_error ("Read failed for 0x%x bytes at offset 0x%x in %s",
                      1, bytes, position, "unexec() output file");
      buf += n_read;
      remains -= n_read;
    }

  return;
}

static void
unexec_write (int fd, long position, char *buf, int bytes)
{
  int n_written;
  int remains = bytes;
  position = unexec_seek (fd, position);

  if (bytes < 0)
    unexec_error ("Attempted write of %d bytes in %s",
                  0, bytes, "unexec() output file");

  errno = 0;

  while (remains > 0)
    {
      n_written = write (fd, buf, remains);
      if (n_written <= 0)
        unexec_error ("Write failed for 0x%x bytes at offset 0x%x in %s",
                      1, bytes, position, "unexec() output file");
      buf += n_written;
      remains -= n_written;
    }

  return;
}

static void 
unexec_pad (int fd, int bytes)
{
  if (bytes > 0)
    {
      char buf[1024];
      int remaining = bytes;

      memset (buf, 0, sizeof (buf));

      while (remaining > 0)
        {
          int this_write = (remaining > sizeof(buf))?sizeof(buf):remaining;
          unexec_write (fd, -1, buf, this_write);
          remaining -= this_write;
        }
    }
}

static void
unexec_fstat (int fd, struct stat *statptr)
{
  errno = 0;
  if (-1 == fstat (fd, statptr))
    unexec_error ("fstat() failed for descriptor %d", 1, fd);
  return;
}

static void
unexec_fchmod (int fd, int mode)
{
  errno = 0;
  if (-1 == fchmod (fd, mode))
    unexec_error ("fchmod() failed for descriptor %d", 1, fd);
  return;
}

static long
unexec_addr_to_offset (long addr, struct translation_struct *ts)
                             
{
  if ((addr < ts->txtaddr) || (addr >= ts->bssaddr))
    return -1;
  else if (addr >= ts->dataddr)
    return ((long) ((addr - ts->dataddr) + ts->datoff));
  else 
    return ((long) ((addr - ts->txtaddr) + ts->txtoff));
}


/*
 * "LD.SO" DATA AND SYMBOL TABLE OPERATIONS 
 */

static void
copy_relocation_site (struct relocation_info *ri, 
                      caddr_t from_base_addr,
                      caddr_t to_base_addr,
                      struct translation_struct *ts)
{
  long offset;
  caddr_t from, to;

  /* We can get relocation sites in the bss region, for objects whose
     contents are copied from a shared library.  We don't need or want
     to restore these at present. */
#ifndef sparc
  if (ri->r_copy)
    return;
#else
  /* Struct relocation_info_sparc doesn't have member r_copy.
     Instead, we use the address to check if this is run-time-copied. */
  if (ri->r_address >= ts->bssaddr && ri->r_address < ts->endaddr)
    return;
#endif

  offset = unexec_addr_to_offset (ri->r_address, ts);
  if (offset == -1)
    unexec_error ("bad relocation address 0x%x (0x%x)", 0, ri->r_address,
		  ((long *)ri)[1]);

  from = from_base_addr + offset;
  to = to_base_addr + offset;
  /* This stuff should be in a md_ file somewhere... */
#ifndef sparc
  switch (ri->r_length)
    {
    case 0:
      *((char *) to) = *((char *) from);
      break;
    case 1:
      *((short *) to) = *((short *) from);
      break;
    case 2:
      *((long *) to) = *((long *) from);
      break;
    default:
      unexec_error ("unknown reloc length %d seen during unexec()",
		    0, ri->r_length);
      break;
    }
#else /* sparc */
  switch (ri->r_type)
    {
    case RELOC_8:
    case RELOC_DISP8:
      *((char *) to) = *((char *) from);
      break;
    case RELOC_16:
    case RELOC_DISP16:
      *((short *) to) = *((short *) from);
      break;     
    case RELOC_LO10:
    case RELOC_13:     
    case RELOC_22:     
    case RELOC_HI22:
    case RELOC_WDISP22:
    case RELOC_WDISP30:
    case RELOC_32:
    case RELOC_DISP32:
    case RELOC_GLOB_DAT:
      *((long *) to) = *((long *) from);
      break;
    case RELOC_JMP_SLOT:
      {
        long *target = (long *) to;
        long *source = (long *) from;
        *target = *source;
        target++;
        source++;
        *target = *source;
        target++;
        source++;
        *target = *source;
      }
      break;
    default:
      unexec_error ("unknown reloc type %d seen during unexec()",
		    0, ri->r_type);
      break;
    }
#endif /* sparc */
}

static void
reset_symtab (struct nlist *start, struct nlist *end, char *strtab,
              long edata_value, long end_value, int shlib_image)
{
  struct nlist *tmp = start;
  int found_edata = 0;
  int found_end = 0;
     
  while (tmp < end)
    {
      int type = tmp->n_type;

      if ((type == (N_UNDF | N_EXT)) &&
          (tmp->n_value != 0))
        unexec_error ("unexec'ing image has COMMON symbols in it -- we quit!",
		      0);
     
      if (!(type & N_STAB))
        {
          if (!found_edata &&
              (type == (N_EXT | N_DATA)) &&
              tmp->n_un.n_strx &&
              !strcmp ("_edata", strtab + tmp->n_un.n_strx))
            {
              tmp->n_value = edata_value;
              found_edata = 1;
            }


          if ((type & N_TYPE) == N_BSS)
            {
              if (!found_end &&
                  (type == (N_EXT | N_BSS)) &&
                  tmp->n_un.n_strx &&
                  !strcmp ("_end", strtab + tmp->n_un.n_strx))
                {
                  tmp->n_value = end_value;
                  found_end = 1;
                }
              else if (type & N_EXT)
                tmp->n_type = N_DATA | N_EXT;
              else
                tmp->n_type = N_DATA;
            }

          /* the way things are being handled here, having sbrk() in the
             image is fatal for an image linked with shared lib's (although 
             the code could be modified to support it), but this should 
             never happen anyway */
          if (shlib_image &&
              (type == (N_EXT | N_TEXT)) &&
              tmp->n_un.n_strx &&
              !strcmp ("_sbrk", strtab + tmp->n_un.n_strx))
            unexec_error ("unexec'd shlib image has sbrk() in it -- we quit!",
                          0);
        }

      tmp++;
    }
} 
     
static void
reset_ldso_symtab (struct nzlist *start, struct nzlist *end, char *strtab,
              long edata_value, long end_value, int shlib_image)
{
  struct nzlist *tmp = start;
  int found_edata = 0;
  int found_end = 0;
     
  while (tmp < end) {
    int type = tmp->nz_type;
/*
 * the following code breaks under FreeBSD-1.1-BETA, but everything
 * seems to work perfectly if it's commented out.  This did not break
 * anything until the changes to ld.so were made.
 */
/*
    if ((type == (N_UNDF | N_EXT)) && (tmp->nz_value != 0))
      unexec_error("unexec'ing image has COMMON symbols in rel -- we quit!",0);
*/
    if (!(type & N_STAB)) {
      if (!found_edata &&
	  (type == (N_EXT | N_DATA)) &&
	  !strcmp ("_edata", strtab + tmp->nz_strx)) {
	tmp->nz_value = edata_value;
	found_edata = 1;
      }

      if ((type & N_TYPE) == N_BSS) {
	if (!found_end &&
	    (type == (N_EXT | N_BSS)) &&
	    !strcmp ("_end", strtab + tmp->nz_strx)) {
	  tmp->nz_value = end_value;
	  found_end = 1;
	} else if (type & N_EXT)
	  tmp->nz_type = N_DATA | N_EXT;
	else
	  tmp->nz_type = N_DATA;
      }

      /* the way things are being handled here, having sbrk() in the
	 image is fatal for an image linked with shared lib's (although 
	 the code could be modified to support it), but this should 
	 never happen anyway */
      if (shlib_image &&
	  (type == (N_EXT | N_TEXT)) &&
	  !strcmp ("_sbrk", strtab + tmp->nz_strx))
	unexec_error("unexec'd shlib image has sbrk() ref -- we quit!", 0);
    }
    tmp++;
  }
} 
     
extern int getpagesize (void);

/*
 * EXPORTED FUNCTIONS 
 */

/* this has to be a global variable to prevent the optimizers from
 * assuming that it can not be 0.  
*/
static void *dynamic_addr = (void *) &_DYNAMIC;

int
unexec (char *new_name, char *old_name,
        unsigned int emacs_edata, unsigned int dummy1, unsigned int dummy2)
{
  /* ld.so data */
  struct _dynamic *ld = 0;
  struct section_dispatch_table *ld2 = 0;
  /* old and new state */
  int old_fd;
  int new_fd;
  caddr_t old_base_addr;
  caddr_t new_base_addr;
  struct exec old_hdr;
  struct exec new_hdr;
  struct stat old_buf;
  struct stat new_buf;
  /* some process specific "constants" */
  unsigned long n_pagsiz, new_edata;
  long page_size = getpagesize ();
  caddr_t plt_end;
  caddr_t current_break = (caddr_t) sbrk (0);

  if (!page_size)
    unexec_error ("unexec() failed because we can't get the size of a page!",
                  0);

  /* see if this is a -Bdynamic image -- if so, find ld.so structures */
  if (dynamic_addr)
    {
      ld = (struct _dynamic *) dynamic_addr;
      ld2 = ld->d_un.d_sdt;
      if (ld->d_version < LD_VERSION_BSD)
        unexec_error ("%s linked with obsolete version of ld -- we quit!",
                      0, old_name);
    }

  /* open the old and new files, figuring out how big the old one is
     so that we can map it in */
  old_fd = unexec_open (old_name, O_RDONLY, 0);
  new_fd = unexec_open (new_name, O_RDWR | O_CREAT | O_TRUNC, 0666);

  /* setup the header and the statbuf for old_fd */
  unexec_read (old_fd, 0, (char *) &old_hdr, sizeof (old_hdr));
  unexec_fstat (old_fd, &old_buf);


  /* set up some important constants */
  n_pagsiz = __LDPGSZ;
  if (dynamic_addr)
    plt_end = (caddr_t) MASK_UP (ld2->sdt_plt + ld2->sdt_plt_sz, sizeof (double));
  else
    plt_end = (caddr_t) N_DATADDR (old_hdr);

#if 0
  /* never write protect the variable "environ", defined in /lib/crt0.o, and
     set in process.c and callproc.c */
  mprotect_bottom_addr = ((unsigned long) &environ) + sizeof (char **);
  /* never protect ABOVE the end of data emacs_edata specified */
  mprotect_top_addr = MIN (emacs_edata, N_DATADDR (old_hdr) + old_hdr.a_data);
#endif

  /* Set up the image of the old file */
  old_base_addr = unexec_mmap (old_fd, old_buf.st_size, PROT_READ,
			       MAP_FILE | MAP_PRIVATE);
  close (old_fd);

  /* set up the new exec */
  new_hdr = old_hdr;
  new_edata = (unsigned long) MASK_UP (current_break, n_pagsiz);
  new_hdr.a_data = new_edata - ((unsigned long) N_DATADDR (old_hdr));
  new_hdr.a_bss  = 0;

  /* set up this variable, in case we want to reset "the break" 
     when restarting */
  sbrk_of_0_at_unexec = ((unsigned long) MASK_UP (current_break, n_pagsiz));
     
  /* Write out the first approximation to the new file. The sizes of
     each section will be correct, but there will be a number of 
     corrections that will need to be made. */
  {
    long old_datoff = N_DATOFF (old_hdr);
    long old_dataddr = N_DATADDR (old_hdr);
    long new_treloff = N_RELOFF (new_hdr);
    long old_treloff = N_RELOFF (old_hdr);
    long ld_so_size = ((unsigned long) plt_end) - old_dataddr;
    long real_data_size = current_break - plt_end;
    long pad_size = 
      MASK_UP (current_break, n_pagsiz) - ((unsigned long) current_break);


    /* First, write the text segment with new header -- copy everything until
       the start of the data segment from the old file, and then go back and 
       write the new header. */
    unexec_write (new_fd, 0, old_base_addr, old_datoff + ld_so_size);
    unexec_write (new_fd, 0, (char *) &new_hdr, sizeof (new_hdr));

    /* Copy the rest of the data segment from the running image. */
    unexec_write (new_fd, old_datoff + ld_so_size, 
                  plt_end, real_data_size);

    /* pad out the data segment */
    unexec_pad (new_fd, pad_size);
    
    /* Finally, copy the symbol table information from the old file. */
    unexec_write (new_fd, new_treloff,
                  old_base_addr + old_treloff,
                  old_buf.st_size - old_treloff);
  }
     
     
  /* Next, map in the output file so that we can jump around fixing it
     up. We retain the old file so that we can refer to it. */
  unexec_fstat (new_fd, &new_buf);
  new_base_addr = unexec_mmap (new_fd, 
                               MASK_UP (new_buf.st_size, page_size),
                               PROT_READ | PROT_WRITE,
			       MAP_FILE | MAP_SHARED);



  /* We need to do 2 things. First, make sure that _edata and _end (and
     hence, curbrk) are set to the correct values. At the same time, for
     neatness and to help with debugging, mark all the types of all ld.so
     and nm BSS symbols in the new file to be DATA, and make sure that
     there are no COMMON symbols in the output file, as any references to
     these can lose really big. Second, reset all of the ld.so "relocation
     sites" in the new file to have the values that appear in the old file
     -- the failure to do this was the biggest loser in the old version of
     this code. */

  /* STEP 1 */
  /* Reset the regular symbol table first. */
  reset_symtab ((struct nlist *) (new_base_addr + N_SYMOFF(new_hdr)),
		(struct nlist *) (new_base_addr + N_SYMOFF(new_hdr) +
				  new_hdr.a_syms),
		(char *) (new_base_addr + N_STROFF(new_hdr)),
		new_edata, new_edata,
		!!dynamic_addr);

  /* Now reset the ld.so symbol table. */
  if (dynamic_addr)
    {
      struct translation_struct ts;
      struct relocation_info *tmp, *end;
      caddr_t syms, strings;

      /* set up the structure that we use to translate addresses in the
	 old file into file offsets */
      ts.txtaddr = N_TXTADDR (old_hdr);
      ts.txtoff = N_TXTOFF (old_hdr);
      ts.dataddr = N_DATADDR (old_hdr);
      ts.datoff = N_DATOFF (old_hdr);
      ts.bssaddr = N_DATADDR (old_hdr) + old_hdr.a_data;
      ts.endaddr = ts.bssaddr + old_hdr.a_bss;

      syms = new_base_addr + unexec_addr_to_offset(ld2->sdt_nzlist, &ts);
      strings = new_base_addr + unexec_addr_to_offset(ld2->sdt_strings, &ts);
      reset_ldso_symtab ((struct nzlist *) syms, (struct nzlist *) strings,
			 (char *) strings,
			 new_edata, new_edata,
			 !!dynamic_addr);

      /* STEP 2 */
      tmp = (struct relocation_info *)
	(old_base_addr + unexec_addr_to_offset(ld2->sdt_rel, &ts));
      end = (struct relocation_info *)
	(old_base_addr + unexec_addr_to_offset(ld2->sdt_hash, &ts));
      while (tmp < end)
	{
	  copy_relocation_site (tmp, old_base_addr, new_base_addr, &ts);
	  tmp++;
	}
    }
     
  /* get rid of the mmap-ed file space and make the output file 
     executable -- then quit */
  munmap (new_base_addr, MASK_UP (new_buf.st_size, page_size));
  munmap (old_base_addr, MASK_UP (old_buf.st_size, page_size));
  unexec_fchmod (new_fd, 0755);
  close (new_fd);
  return 0;
}


int
run_time_remap (char *dummy)
{
      unsigned long current_sbrk = (unsigned long) sbrk (0);

#if __FreeBSD_version < 300000 /* 2.x can work with this code */
      if (sbrk_of_0_at_unexec < current_sbrk)
	{
	  if (sbrk_of_0_at_unexec != 0)
	    fprintf (stderr, "Absurd new brk addr = %lx (current = %lx)\n", 
		     sbrk_of_0_at_unexec, current_sbrk);
	}
      else
#endif
	if (sbrk_of_0_at_unexec > current_sbrk)
        {
          errno = 0;
          if (brk ((caddr_t) sbrk_of_0_at_unexec))
            fprintf (stderr, "failed to change brk addr to %lx: %s\n", 
                     sbrk_of_0_at_unexec, SYS_ERR);
        }

#if 0
/* with proper COW, i don't think we really need to do this... */
  {
    long page_size = getpagesize();
    unsigned long base_addr = MASK_UP (mprotect_bottom_addr, page_size);
    unsigned long top_addr = MASK_DOWN (mprotect_top_addr, page_size);
    long len = top_addr - base_addr;

    if (len > 0)
      {
        errno = 0;
        if (mprotect ((caddr_t) base_addr, len, PROT_READ | PROT_EXEC))
          fprintf (stderr, "failed to change protection on data pages: %s\n",
                   SYS_ERR);
      }
  }
#endif
             
  return 0;
}
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