unexconvex.c

早期freebsd实现

	}
    } else
	bss_start = bss_end;

    if (data_start > bss_start)	{ /* Can't have negative data size. */
	ERROR2 ("unexec: data_start (%x) can't be greater than bss_start (%x)",
		data_start, bss_start);
    }

    /* Salvage as much info from the existing file as possible */
    if (a_out < 0) {
	ERROR0 ("can't build a COFF file from scratch yet");
	/*NOTREACHED*/
    }

    if (read (a_out, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr)) {
	PERROR (a_name);
    }
    block_copy_start += sizeof (f_hdr);
    if (f_hdr.h_opthdr > 0) {
	if (read (a_out, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr)) {
	    PERROR (a_name);
	}
	block_copy_start += sizeof (f_ohdr);
    }

    /* Allocate room for scn headers */
    stbl = (struct scnhdr *)malloc( sizeof(struct scnhdr) * f_hdr.h_nscns );
    if( stbl == NULL ) {
	ERROR0( "unexec: malloc of stbl failed" );
    }

    f_tdhdr = f_tbhdr = NULL;

    /* Loop through section headers, copying them in */
    for (scns = 0; scns < f_hdr.h_nscns; scns++) {

	if( read( a_out, &stbl[scns], sizeof(*stbl)) != sizeof(*stbl)) {
	    PERROR (a_name);
	}

	scntype = stbl[scns].s_flags & S_TYPMASK; /* What type of section */

	if( stbl[scns].s_scnptr > 0L) {
	    if( block_copy_start < stbl[scns].s_scnptr + stbl[scns].s_size )
		block_copy_start = stbl[scns].s_scnptr + stbl[scns].s_size;
	}

	if( scntype == S_TEXT) {
	    f_thdr = &stbl[scns];
	} else if( scntype == S_DATA) {
	    f_dhdr = &stbl[scns];
#ifdef S_TDATA
	} else if( scntype == S_TDATA ) {
	    f_tdhdr = &stbl[scns];
	} else if( scntype == S_TBSS ) {
	    f_tbhdr = &stbl[scns];
#endif /* S_TDATA (thread stuff) */

	} else if( scntype == S_BSS) {
	    f_bhdr = &stbl[scns];
	}

    }

    /* We will now convert TEXT and DATA into TEXT, BSS into DATA, and leave
     * all thread stuff alone.
     */

    /* Now we alter the contents of all the f_*hdr variables
       to correspond to what we want to dump.  */

    f_thdr->s_vaddr = (long) start_of_text ();
    f_thdr->s_size = data_start - f_thdr->s_vaddr;
    f_thdr->s_scnptr = pagesz;
    f_thdr->s_relptr = 0;
    f_thdr->s_nrel = 0;

    eo_data = f_thdr->s_scnptr + f_thdr->s_size;

    if( f_tdhdr ) {		/* Process thread data */

	f_tdhdr->s_vaddr = data_start;
	f_tdhdr->s_size += f_dhdr->s_size - (data_start - f_dhdr->s_vaddr);
	f_tdhdr->s_scnptr = eo_data;
	f_tdhdr->s_relptr = 0;
	f_tdhdr->s_nrel = 0;

	eo_data += f_tdhdr->s_size;

	/* And now for DATA */

	f_dhdr->s_vaddr = f_bhdr->s_vaddr; /* Take BSS start address */
	f_dhdr->s_size = bss_end - f_bhdr->s_vaddr;
	f_dhdr->s_scnptr = eo_data;
	f_dhdr->s_relptr = 0;
	f_dhdr->s_nrel = 0;

	eo_data += f_dhdr->s_size;

    } else {

	f_dhdr->s_vaddr = data_start;
	f_dhdr->s_size = bss_start - data_start;
	f_dhdr->s_scnptr = eo_data;
	f_dhdr->s_relptr = 0;
	f_dhdr->s_nrel = 0;

	eo_data += f_dhdr->s_size;

    }

    f_bhdr->s_vaddr = bss_start;
    f_bhdr->s_size = bss_end - bss_start + pagesz /* fudge */;
    f_bhdr->s_scnptr = 0;
    f_bhdr->s_relptr = 0;
    f_bhdr->s_nrel = 0;

    text_scnptr = f_thdr->s_scnptr;
    data_scnptr = f_dhdr->s_scnptr;
    bias = eo_data - block_copy_start;

    if (f_ohdr.o_symptr > 0L) {
	f_ohdr.o_symptr += bias;
    }

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

    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);
    }

    for( scns = 0; scns < f_hdr.h_nscns; scns++ ) {

	/* This is a cheesey little loop to write out the section headers
	 * in order of increasing virtual address. Dull but effective.
	 */

	for( i = scns+1; i < f_hdr.h_nscns; i++ ) {
	    if( stbl[i].s_vaddr < stbl[scns].s_vaddr ) { /* Swap */
		scntemp = stbl[i];
		stbl[i] = stbl[scns];
		stbl[scns] = scntemp;
	    }
	}

    }

    for( scns = 0; scns < f_hdr.h_nscns; scns++ ) {

	if( write( new, &stbl[scns], sizeof(*stbl)) != sizeof(*stbl)) {
	    PERROR (new_name);
	}

    }

    return (0);

}

/* ****************************************************************
 * copy_text_and_data
 *
 * Copy the text and data segments from memory to the new a.out
 */
static int
copy_text_and_data (new)
int new;
{
    register int scns;

    for( scns = 0; scns < f_hdr.h_nscns; scns++ )
	write_segment( new, &stbl[scns] );

    return 0;
}

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

    if( sptr->s_scnptr == 0 )
	return;			/* Nothing to do */

    if( lseek( new, (long) sptr->s_scnptr, 0 ) == -1 )
	PERROR( "unexecing" );

    bzero (zeros, sizeof zeros);

    ptr = (char *) sptr->s_vaddr;
    end = ptr + sptr->s_size;

    while( 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);
	}
	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;

    if (SYMS_START == 0L)
	return 0;

    lseek (a_out, SYMS_START, 0);	/* Position a.out to symtab. */
    lseek( new, (long)f_ohdr.o_symptr, 0 );

    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);
}

/* Find the first pty letter.  This is usually 'p', as in ptyp0, but
   is sometimes configured down to 'm', 'n', or 'o' for some reason. */

first_pty_letter ()
{
  struct stat buf;
  char pty_name[16];
  char c;

  for (c = 'o'; c >= 'a'; c--)
    {
      sprintf (pty_name, "/dev/pty%c0", c);
      if (stat (pty_name, &buf) < 0)
	return c + 1;
    }
  return 'a';
}