unexec.c

早期freebsd实现

  f_thdr.s_scnptr += (f_hdr.f_nscns) * (sizeof (f_thdr));
  lnnoptr = f_thdr.s_lnnoptr;
#ifdef SECTION_ALIGNMENT
  /* Some systems require special alignment
     of the sections in the file itself.  */
  f_thdr.s_scnptr
    = (f_thdr.s_scnptr + SECTION_ALIGNMENT) & ~SECTION_ALIGNMENT;
#endif /* SECTION_ALIGNMENT */
  text_scnptr = f_thdr.s_scnptr;
  f_dhdr.s_paddr = f_ohdr.data_start;
  f_dhdr.s_vaddr = f_ohdr.data_start;
  f_dhdr.s_size = f_ohdr.dsize;
  f_dhdr.s_scnptr = f_thdr.s_scnptr + f_thdr.s_size;
#ifdef SECTION_ALIGNMENT
  /* Some systems require special alignment
     of the sections in the file itself.  */
  f_dhdr.s_scnptr
    = (f_dhdr.s_scnptr + SECTION_ALIGNMENT) & ~SECTION_ALIGNMENT;
#endif /* SECTION_ALIGNMENT */
#ifdef DATA_SECTION_ALIGNMENT
  /* Some systems require special alignment
     of the data section only.  */
  f_dhdr.s_scnptr
    = (f_dhdr.s_scnptr + DATA_SECTION_ALIGNMENT) & ~DATA_SECTION_ALIGNMENT;
#endif /* DATA_SECTION_ALIGNMENT */
  data_scnptr = f_dhdr.s_scnptr;
  f_bhdr.s_paddr = f_ohdr.data_start + f_ohdr.dsize;
  f_bhdr.s_vaddr = f_ohdr.data_start + f_ohdr.dsize;
  f_bhdr.s_size = f_ohdr.bsize;
  f_bhdr.s_scnptr = 0L;
#ifndef USG_SHARED_LIBRARIES
  bias = f_dhdr.s_scnptr + f_dhdr.s_size - block_copy_start;
#endif

  if (f_hdr.f_symptr > 0L)
    {
      f_hdr.f_symptr += bias;
    }

  if (f_thdr.s_lnnoptr > 0L)
    {
      f_thdr.s_lnnoptr += bias;
    }

#ifdef ADJUST_EXEC_HEADER
  ADJUST_EXEC_HEADER
#endif /* ADJUST_EXEC_HEADER */

  if (write (new, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
    {
      PERROR (new_name);
    }

  if (write (new, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
    {
      PERROR (new_name);
    }

#ifndef USG_SHARED_LIBRARIES

  if (write (new, &f_thdr, sizeof (f_thdr)) != sizeof (f_thdr))
    {
      PERROR (new_name);
    }

  if (write (new, &f_dhdr, sizeof (f_dhdr)) != sizeof (f_dhdr))
    {
      PERROR (new_name);
    }

  if (write (new, &f_bhdr, sizeof (f_bhdr)) != sizeof (f_bhdr))
    {
      PERROR (new_name);
    }

#else /* USG_SHARED_LIBRARIES */

  /* The purpose of this code is to write out the new file's section
   * header table.
   *
   * Scan through the original file's sections.  If the encountered
   * section is one we know (.text, .data or .bss), write out the
   * correct header.  If it is a section we do not know (such as
   * .lib), adjust the address of where the section data is in the
   * file, and write out the header.
   *
   * If any section preceeds .text or .data in the file, this code
   * will not adjust the file pointer for that section correctly.
   */

  lseek (a_out, (off_t) sizeof (f_hdr) + sizeof (f_ohdr), 0);

  for (scns = f_hdr.f_nscns; scns > 0; scns--)
    {
      if (read (a_out, &scntemp, sizeof (scntemp)) != sizeof (scntemp))
	PERROR (a_name);

      if (!strcmp (scntemp.s_name, f_thdr.s_name))	/* .text */
	{
	  if (write (new, &f_thdr, sizeof (f_thdr)) != sizeof (f_thdr))
	    PERROR (new_name);
	}
      else if (!strcmp (scntemp.s_name, f_dhdr.s_name))	/* .data */
	{
	  if (write (new, &f_dhdr, sizeof (f_dhdr)) != sizeof (f_dhdr))
	    PERROR (new_name);
	}
      else if (!strcmp (scntemp.s_name, f_bhdr.s_name))	/* .bss */
	{
	  if (write (new, &f_bhdr, sizeof (f_bhdr)) != sizeof (f_bhdr))
	    PERROR (new_name);
	}
      else
	{
	  if (scntemp.s_scnptr)
	    scntemp.s_scnptr += bias;
	  if (write (new, &scntemp, sizeof (scntemp)) != sizeof (scntemp))
	    PERROR (new_name);
	}
    }
#endif /* USG_SHARED_LIBRARIES */

  return (0);

#else /* if not COFF */

  /* Get symbol table info from header of a.out file if given one. */
  if (a_out >= 0)
    {
      if (read (a_out, &ohdr, sizeof hdr) != sizeof hdr)
	{
	  PERROR (a_name);
	}

      if (N_BADMAG (ohdr))
	{
	  ERROR1 ("invalid magic number in %s", a_name);
	}
      hdr = ohdr;
    }
  else
    {
      bzero (hdr, sizeof hdr);
    }

  unexec_text_start = (long) start_of_text ();
  unexec_data_start = data_start;

  /* Machine-dependent fixup for header, or maybe for unexec_text_start */
#ifdef ADJUST_EXEC_HEADER
  ADJUST_EXEC_HEADER;
#endif /* ADJUST_EXEC_HEADER */

  hdr.a_trsize = 0;
  hdr.a_drsize = 0;
  if (entry_address != 0)
    hdr.a_entry = entry_address;

  hdr.a_bss = bss_end - bss_start;
  hdr.a_data = bss_start - data_start;
#ifdef NO_REMAP
  hdr.a_text = ohdr.a_text;
#else /* not NO_REMAP */
  hdr.a_text = data_start - unexec_text_start;

#ifdef A_TEXT_OFFSET
  hdr.a_text += A_TEXT_OFFSET (ohdr);
#endif

#endif /* not NO_REMAP */

  if (write (new, &hdr, sizeof hdr) != sizeof hdr)
    {
      PERROR (new_name);
    }

#ifdef A_TEXT_OFFSET
  hdr.a_text -= A_TEXT_OFFSET (ohdr);
#endif

  return 0;

#endif /* not COFF */
}

/* ****************************************************************
 * copy_text_and_data
 *
 * Copy the text and data segments from memory to the new a.out
 */
static int
copy_text_and_data (new, a_out)
     int new, a_out;
{
  register char *end;
  register char *ptr;

#ifdef COFF

#ifdef USG_SHARED_LIBRARIES

  int scns;
  struct scnhdr scntemp;		/* Temporary section header */

  /* The purpose of this code is to write out the new file's section
   * contents.
   *
   * Step through the section table.  If we know the section (.text,
   * .data) do the appropriate thing.  Otherwise, if the section has
   * no allocated space in the file (.bss), do nothing.  Otherwise,
   * the section has space allocated in the file, and is not a section
   * we know.  So just copy it.
   */

  lseek (a_out, (off_t) sizeof (struct filehdr) + sizeof (struct aouthdr), 0);

  for (scns = f_hdr.f_nscns; scns > 0; scns--)
    {
      if (read (a_out, &scntemp, sizeof (scntemp)) != sizeof (scntemp))
	PERROR ("temacs");

      if (!strcmp (scntemp.s_name, ".text"))
	{
	  lseek (new, (off_t) text_scnptr, 0);
	  ptr = (char *) f_ohdr.text_start;
	  end = ptr + f_ohdr.tsize;
	  write_segment (new, ptr, end);
	}
      else if (!strcmp (scntemp.s_name, ".data"))
	{
	  lseek (new, (off_t) data_scnptr, 0);
	  ptr = (char *) f_ohdr.data_start;
	  end = ptr + f_ohdr.dsize;
	  write_segment (new, ptr, end);
	}
      else if (!scntemp.s_scnptr)
	; /* do nothing - no data for this section */
      else
	{
	  char page[BUFSIZ];
	  int size, n;
	  long old_a_out_ptr = lseek (a_out, (off_t) 0, 1);

	  lseek (a_out, (off_t) scntemp.s_scnptr, 0);
	  for (size = scntemp.s_size; size > 0; size -= sizeof (page))
	    {
	      n = size > sizeof (page) ? sizeof (page) : size;
	      if (read (a_out, page, n) != n || write (new, page, n) != n)
		PERROR ("xemacs");
	    }
	  lseek (a_out, (off_t) old_a_out_ptr, 0);
	}
    }

#else /* COFF, but not USG_SHARED_LIBRARIES */

  lseek (new, (off_t) text_scnptr, 0);
  ptr = (char *) f_ohdr.text_start;
  end = ptr + f_ohdr.tsize;
  write_segment (new, ptr, end);

  lseek (new, (off_t) data_scnptr, 0);
  ptr = (char *) f_ohdr.data_start;
  end = ptr + f_ohdr.dsize;
  write_segment (new, ptr, end);

#endif /* USG_SHARED_LIBRARIES */

#else /* if not COFF */

/* Some machines count the header as part of the text segment.
   That is to say, the header appears in core
   just before the address that start_of_text () returns.
   For them, N_TXTOFF is the place where the header goes.
   We must adjust the seek to the place after the header.
   Note that at this point hdr.a_text does *not* count
   the extra A_TEXT_OFFSET bytes, only the actual bytes of code.  */

#ifdef A_TEXT_SEEK
  lseek (new, (off_t) A_TEXT_SEEK (hdr), 0);
#else
#ifdef A_TEXT_OFFSET
  /* Note that on the Sequent machine A_TEXT_OFFSET != sizeof (hdr)
     and sizeof (hdr) is the correct amount to add here.  */
  /* In version 19, eliminate this case and use A_TEXT_SEEK whenever
     N_TXTOFF is not right.  */
  lseek (new, (off_t) N_TXTOFF (hdr) + sizeof (hdr), 0);
#else
  lseek (new, (off_t) N_TXTOFF (hdr), 0);
#endif /* no A_TEXT_OFFSET */
#endif /* no A_TEXT_SEEK */

  ptr = (char *) unexec_text_start;
  end = ptr + hdr.a_text;
  write_segment (new, ptr, end);

  ptr = (char *) unexec_data_start;
  end = ptr + hdr.a_data;
/*  This lseek is certainly incorrect when A_TEXT_OFFSET
    and I believe it is a no-op otherwise.
    Let's see if its absence ever fails.  */
/*  lseek (new, (off_t) N_TXTOFF (hdr) + hdr.a_text, 0); */
  write_segment (new, ptr, end);

#endif /* not COFF */

  return 0;
}

write_segment (new, ptr, end)
     int new;
     register char *ptr, *end;
{
  register int i, nwrite, ret;
  char buf[80];
  extern int errno;
  char zeros[128];

  bzero (zeros, sizeof zeros);

  for (i = 0; ptr < end;)
    {
      /* distance to next multiple of 128.  */
      nwrite = (((int) ptr + 128) & -128) - (int) ptr;
      /* But not beyond specified end.  */
      if (nwrite > end - ptr) nwrite = end - ptr;
      ret = write (new, ptr, nwrite);
      /* If write gets a page fault, it means we reached
	 a gap between the old text segment and the old data segment.
	 This gap has probably been remapped into part of the text segment.
	 So write zeros for it.  */
      if (ret == -1 && errno == EFAULT)
	write (new, zeros, nwrite);
      else if (nwrite != ret)
	{
	  sprintf (buf,
		   "unexec write failure: addr 0x%x, fileno %d, size 0x%x, wrote 0x%x, errno %d",
		   ptr, new, nwrite, ret, errno);
	  PERROR (buf);
	}
      i += nwrite;
      ptr += nwrite;
    }
}

/* ****************************************************************
 * copy_sym
 *
 * Copy the relocation information and symbol table from the a.out to the new
 */
static int
copy_sym (new, a_out, a_name, new_name)
     int new, a_out;
     char *a_name, *new_name;
{
  char page[1024];
  int n;

  if (a_out < 0)
    return 0;

#ifdef COFF
  if (SYMS_START == 0L)
    return 0;
#endif  /* COFF */

#ifdef COFF
  if (lnnoptr)			/* if there is line number info */
    lseek (a_out, (off_t) lnnoptr, 0);	/* start copying from there */
  else
#endif /* COFF */
    lseek (a_out, (off_t) SYMS_START, 0);	/* Position a.out to symtab. */

  while ((n = read (a_out, page, sizeof page)) > 0)
    {
      if (write (new, page, n) != n)
	{
	  PERROR (new_name);
	}
    }
  if (n < 0)
    {
      PERROR (a_name);
    }
  return 0;
}

/* ****************************************************************
 * mark_x
 *
 * After succesfully building the new a.out, mark it executable
 */
static
mark_x (name)
     char *name;
{
  struct stat sbuf;
  int um;
  int new = 0;  /* for PERROR */

  um = umask (777);
  umask (um);
  if (stat (name, &sbuf) == -1)
    {
      PERROR (name);
    }
  sbuf.st_mode |= 0111 & ~um;
  if (chmod (name, sbuf.st_mode) == -1)
    PERROR (name);
}

/*
 *	If the COFF file contains a symbol table and a line number section,
 *	then any auxiliary entries that have values for x_lnnoptr must
 *	be adjusted by the amount that the line number section has moved
 *	in the file (bias computed in make_hdr).  The #@$%&* designers of
 *	the auxiliary entry structures used the absolute file offsets for
 *	the line number entry rather than an offset from the start of the
 *	line number section!
 *
 *	When I figure out how to scan through the symbol table and pick out
 *	the auxiliary entries that need adjustment, this routine will
 *	be fixed.  As it is now, all such entries are wrong and sdb
 *	will complain.   Fred Fish, UniSoft Systems Inc.
 */

#ifdef COFF

/* This function is probably very slow.  Instead of reopening the new
   file for input and output it should copy from the old to the new
   using the two descriptors already open (WRITEDESC and READDESC).
   Instead of reading one small structure at a time it should use
   a reasonable size buffer.  But I don't have time to work on such
   things, so I am installing it as submitted to me.  -- RMS.  */

adjust_lnnoptrs (writedesc, readdesc, new_name)
     int writedesc;
     int readdesc;
     char *new_name;
{
  register int nsyms;
  register int new;
#ifdef amdahl_uts
  SYMENT symentry;
  AUXENT auxentry;
#else
  struct syment symentry;
  union auxent auxentry;
#endif

  if (!lnnoptr || !f_hdr.f_symptr)
    return 0;

  if ((new = open (new_name, 2)) < 0)
    {
      PERROR (new_name);
      return -1;
    }

  lseek (new, (off_t) f_hdr.f_symptr, 0);
  for (nsyms = 0; nsyms < f_hdr.f_nsyms; nsyms++)
    {
      read (new, &symentry, SYMESZ);
      if (symentry.n_numaux)
	{
	  read (new, &auxentry, AUXESZ);
	  nsyms++;
	  if (ISFCN (symentry.n_type)) {
	    auxentry.x_sym.x_fcnary.x_fcn.x_lnnoptr += bias;
	    lseek (new, (off_t) -AUXESZ, 1);
	    write (new, &auxentry, AUXESZ);
	  }
	}
    }
  close (new);
}

#endif /* COFF */

#endif /* not CANNOT_UNEXEC */

#endif /* not CANNOT_DUMP */