unexaix.c

/* Dump an executable image.
   Copyright (C) 1985, 1986, 1987, 1988, 1999, 2001, 2002, 2003, 2004,
                 2005, 2006, 2007, 2008, 2009  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 <http://www.gnu.org/licenses/>.  */

/*
In other words, you are welcome to use, share and improve this program.
You are forbidden to forbid anyone else to use, share and improve
what you give them.   Help stamp out software-hoarding!  */


/* Originally based on the COFF unexec.c by Spencer W. Thomas.
 *
 * Subsequently hacked on by
 * Bill Mann <Bill_Man@praxisint.com>
 * Andrew Vignaux <Andrew.Vignaux@comp.vuw.ac.nz>
 * Mike Sperber <sperber@informatik.uni-tuebingen.de>
 *
 * Synopsis:
 *	unexec (new_name, a_name, data_start, bss_start, entry_address)
 *	char *new_name, *a_name;
 *	unsigned data_start, bss_start, entry_address;
 *
 * Takes a snapshot of the program and makes an a.out format file in the
 * file named by the string argument new_name.
 * If a_name is non-NULL, the symbol table will be taken from the given file.
 * On some machines, an existing a_name file is required.
 *
 * data_start and entry_address are ignored.
 *
 * bss_start indicates how much of the data segment is to be saved in the
 * a.out file and restored when the program is executed.  It gives the lowest
 * unsaved address, and is rounded up to a page boundary.  The default when 0
 * is given assumes that the entire data segment is to be stored, including
 * the previous data and bss as well as any additional storage allocated with
 * sbrk(2).
 *
 */

#ifndef emacs
#define PERROR(arg) perror (arg); return -1
#else
#include <config.h>
#define PERROR(file) report_error (file, new)
#endif

#include <a.out.h>
/* Define getpagesize () if the system does not.
   Note that this may depend on symbols defined in a.out.h
 */
#include "getpagesize.h"

#include <sys/types.h>
#include <stdio.h>
#include <sys/stat.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>

extern char *start_of_text (void);		/* Start of text */
extern char *start_of_data (void);		/* Start of initialized data */

extern int _data;
extern int _text;

#include <filehdr.h>
#include <aouthdr.h>
#include <scnhdr.h>
#include <syms.h>

static struct filehdr f_hdr;		/* File header */
static struct aouthdr f_ohdr;		/* Optional file header (a.out) */
static long bias;			/* Bias to add for growth */
static long lnnoptr;			/* Pointer to line-number info within file */

static long text_scnptr;
static long data_scnptr;
#define ALIGN(val, pwr) (((val) + ((1L<<(pwr))-1)) & ~((1L<<(pwr))-1))
static long load_scnptr;
static long orig_load_scnptr;
static long orig_data_scnptr;
static int unrelocate_symbols (int, int, char *, char *);

#ifndef MAX_SECTIONS
#define MAX_SECTIONS	10
#endif

static int adjust_lnnoptrs (int, int, char *);

static int pagemask;

#ifdef emacs
#include "lisp.h"

static void
report_error (char *file, int fd)
{
  if (fd)
    close (fd);
  report_file_error ("Cannot unexec", Fcons (build_string (file), Qnil));
}
#endif /* emacs */

#define ERROR0(msg) report_error_1 (new, msg, 0, 0); return -1
#define ERROR1(msg,x) report_error_1 (new, msg, x, 0); return -1
#define ERROR2(msg,x,y) report_error_1 (new, msg, x, y); return -1

static void
report_error_1 (int fd, char *msg, int a1, int a2)
{
  close (fd);
#ifdef emacs
  error (msg, a1, a2);
#else
  fprintf (stderr, msg, a1, a2);
  fprintf (stderr, "\n");
#endif
}

static int make_hdr (int, int, unsigned, unsigned, unsigned, char *, char *);
static void mark_x (char *);
static int copy_text_and_data (int);
static int copy_sym (int, int, char *, char *);
static void write_segment (int, char *, char *);

/* ****************************************************************
 * unexec
 *
 * driving logic.
 */
int unexec (char *new_name, char *a_name,
	    unsigned data_start,
	    unsigned bss_start,
	    unsigned entry_address)
{
  int new = -1, a_out = -1;

  if (a_name && (a_out = open (a_name, O_RDONLY)) < 0)
    {
      PERROR (a_name);
    }
  if ((new = creat (new_name, 0666)) < 0)
    {
      PERROR (new_name);
    }
  if (make_hdr (new, a_out,
		data_start, bss_start,
		entry_address,
		a_name, new_name) < 0
      || copy_text_and_data (new) < 0
      || copy_sym (new, a_out, a_name, new_name) < 0
      || adjust_lnnoptrs (new, a_out, new_name) < 0
      || unrelocate_symbols (new, a_out, a_name, new_name) < 0)
    {
      close (new);
      return -1;
    }

  close (new);
  if (a_out >= 0)
    close (a_out);
  mark_x (new_name);
  return 0;
}

/* ****************************************************************
 * make_hdr
 *
 * Make the header in the new a.out from the header in core.
 * Modify the text and data sizes.
 */
static int
make_hdr (int new, int a_out,
	  unsigned data_start, unsigned bss_start,
	  unsigned entry_address,
	  char *a_name, char *new_name)
{
  int scns;
  unsigned int bss_end;

  struct scnhdr section[MAX_SECTIONS];
  struct scnhdr * f_thdr;		/* Text section header */
  struct scnhdr * f_dhdr;		/* Data section header */
  struct scnhdr * f_bhdr;		/* Bss section header */
  struct scnhdr * f_lhdr;		/* Loader section header */
  struct scnhdr * f_tchdr;		/* Typechk section header */
  struct scnhdr * f_dbhdr;		/* Debug section header */
  struct scnhdr * f_xhdr;		/* Except section header */

  load_scnptr = orig_load_scnptr = lnnoptr = 0;
  pagemask = getpagesize () - 1;

  /* Adjust text/data boundary. */
  data_start = (long) start_of_data ();
  data_start = ADDR_CORRECT (data_start);

  data_start = data_start & ~pagemask; /* (Down) to page boundary. */

  bss_end = ADDR_CORRECT (sbrk (0)) + pagemask;
  bss_end &= ~ pagemask;
  /* Adjust data/bss boundary. */
  if (bss_start != 0)
    {
      bss_start = (ADDR_CORRECT (bss_start) + pagemask);
      /* (Up) to page bdry. */
      bss_start &= ~ pagemask;
      if (bss_start > bss_end)
	{
	  ERROR1 ("unexec: Specified bss_start (%u) is past end of program",
		  bss_start);
	}
    }
  else
    bss_start = bss_end;

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

  /* Salvage as much info from the existing file as possible */
  f_thdr = NULL; f_dhdr = NULL; f_bhdr = NULL;
  f_lhdr = NULL; f_tchdr = NULL; f_dbhdr = NULL; f_xhdr = NULL;
  if (a_out >= 0)
    {
      if (read (a_out, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
	{
	  PERROR (a_name);
	}
      if (f_hdr.f_opthdr > 0)
	{
	  if (read (a_out, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
	    {
	      PERROR (a_name);
	    }
	}
      if (f_hdr.f_nscns > MAX_SECTIONS)
	{
	  ERROR0 ("unexec: too many section headers -- increase MAX_SECTIONS");
	}
      /* Loop through section headers */
      for (scns = 0; scns < f_hdr.f_nscns; scns++) {
	struct scnhdr *s = &section[scns];
	if (read (a_out, s, sizeof (*s)) != sizeof (*s))
	  {
	    PERROR (a_name);
	  }

#define CHECK_SCNHDR(ptr, name, flags) \
  if (strcmp(s->s_name, name) == 0) { \
    if (s->s_flags != flags) { \
      fprintf(stderr, "unexec: %lx flags where %x expected in %s section.\n", \
	      (unsigned long)s->s_flags, flags, name); \
    } \
    if (ptr) { \
      fprintf(stderr, "unexec: duplicate section header for section %s.\n", \
	      name); \
    } \
    ptr = s; \
  }
	CHECK_SCNHDR(f_thdr, _TEXT, STYP_TEXT);
	CHECK_SCNHDR(f_dhdr, _DATA, STYP_DATA);
	CHECK_SCNHDR(f_bhdr, _BSS, STYP_BSS);
	CHECK_SCNHDR(f_lhdr, _LOADER, STYP_LOADER);
	CHECK_SCNHDR(f_dbhdr, _DEBUG,  STYP_DEBUG);
	CHECK_SCNHDR(f_tchdr, _TYPCHK,  STYP_TYPCHK);
	CHECK_SCNHDR(f_xhdr, _EXCEPT,  STYP_EXCEPT);
      }

      if (f_thdr == 0)
	{
	  ERROR1 ("unexec: couldn't find \"%s\" section", (int) _TEXT);
	}
      if (f_dhdr == 0)
	{
	  ERROR1 ("unexec: couldn't find \"%s\" section", (int) _DATA);
	}
      if (f_bhdr == 0)
	{
	  ERROR1 ("unexec: couldn't find \"%s\" section", (int) _BSS);
	}
    }
  else
    {
      ERROR0 ("can't build a COFF file from scratch yet");
    }
  orig_data_scnptr = f_dhdr->s_scnptr;
  orig_load_scnptr = f_lhdr ? f_lhdr->s_scnptr : 0;

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

  /* Indicate that the reloc information is no longer valid for ld (bind);
     we only update it enough to fake out the exec-time loader.  */
  f_hdr.f_flags |= (F_RELFLG | F_EXEC);

  f_ohdr.dsize = bss_start - f_ohdr.data_start;
  f_ohdr.bsize = bss_end - bss_start;

  f_dhdr->s_size = f_ohdr.dsize;
  f_bhdr->s_size = f_ohdr.bsize;
  f_bhdr->s_paddr = f_ohdr.data_start + f_ohdr.dsize;
  f_bhdr->s_vaddr = f_ohdr.data_start + f_ohdr.dsize;

  /* fix scnptr's */
  {
    ulong ptr = section[0].s_scnptr;

    bias = -1;
    for (scns = 0; scns < f_hdr.f_nscns; scns++)
      {
	struct scnhdr *s = &section[scns];

	if (s->s_flags & STYP_PAD)        /* .pad sections omitted in AIX 4.1 */
	  {
	    /*
	     * the text_start should probably be o_algntext but that doesn't
	     * seem to change
	     */
	    if (f_ohdr.text_start != 0) /* && scns != 0 */
	      {
		s->s_size = 512 - (ptr % 512);
		if (s->s_size == 512)
		  s->s_size = 0;
	      }
	    s->s_scnptr = ptr;
	  }
	else if (s->s_flags & STYP_DATA)
	  s->s_scnptr = ptr;
	else if (!(s->s_flags & (STYP_TEXT | STYP_BSS)))
	  {
	    if (bias == -1)                /* if first section after bss */
	      bias = ptr - s->s_scnptr;

	    s->s_scnptr += bias;
	    ptr = s->s_scnptr;
	  }

	ptr = ptr + s->s_size;
      }
  }

  /* fix other pointers */
  for (scns = 0; scns < f_hdr.f_nscns; scns++)
    {
      struct scnhdr *s = &section[scns];

      if (s->s_relptr != 0)
	{
	  s->s_relptr += bias;
	}
      if (s->s_lnnoptr != 0)
	{
	  if (lnnoptr == 0) lnnoptr = s->s_lnnoptr;
	  s->s_lnnoptr += bias;
	}
    }

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

  text_scnptr = f_thdr->s_scnptr;
  data_scnptr = f_dhdr->s_scnptr;
  load_scnptr = f_lhdr ? f_lhdr->s_scnptr : 0;

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

  if (f_hdr.f_opthdr > 0)
    {
      if (write (new, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
	{
	  PERROR (new_name);
	}
    }

  for (scns = 0; scns < f_hdr.f_nscns; scns++) {
    struct scnhdr *s = &section[scns];
    if (write (new, s, sizeof (*s)) != sizeof (*s))
      {
	PERROR (new_name);
      }
  }

  return (0);
}

/* ****************************************************************

 *
 * Copy the text and data segments from memory to the new a.out
 */
static int
copy_text_and_data (int new)
{
  char *end;
  char *ptr;

  lseek (new, (long) text_scnptr, SEEK_SET);
  ptr = start_of_text () + text_scnptr;
  end = ptr + f_ohdr.tsize;
  write_segment (new, ptr, end);

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

  return 0;
}

#define UnexBlockSz (1<<12)			/* read/write block size */
static void
write_segment (int new, char *ptr, char *end)
{
  int i, nwrite, ret;
  char buf[80];
  extern int errno;
  char zeros[UnexBlockSz];

  for (i = 0; ptr < end;)
    {
      /* distance to next block.  */
      nwrite = (((int) ptr + UnexBlockSz) & -UnexBlockSz) - (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)
	{
	  memset (zeros, 0, nwrite);
	  write (new, zeros, nwrite);
	}
      else if (nwrite != ret)
	{
	  sprintf (buf,
		   "unexec write failure: addr 0x%lx, fileno %d, size 0x%x, wrote 0x%x, errno %d",
		   (unsigned long)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 (int new, int a_out, char *a_name, char *new_name)
{
  char page[UnexBlockSz];
  int n;

  if (a_out < 0)
    return 0;

  if (orig_load_scnptr == 0L)
    return 0;

  if (lnnoptr && lnnoptr < orig_load_scnptr) /* if there is line number info  */
    lseek (a_out, lnnoptr, SEEK_SET);  /* start copying from there */
  else
    lseek (a_out, orig_load_scnptr, SEEK_SET); /* 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 successfully building the new a.out, mark it executable
 */
static void
mark_x (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);
}

static int
adjust_lnnoptrs (int writedesc, int readdesc, char *new_name)
{
  int nsyms;
  int naux;
  int new;
  struct syment symentry;
  union auxent auxentry;

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

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

  lseek (new, f_hdr.f_symptr, SEEK_SET);
  for (nsyms = 0; nsyms < f_hdr.f_nsyms; nsyms++)
    {
      read (new, &symentry, SYMESZ);
      if (symentry.n_sclass == C_BINCL || symentry.n_sclass == C_EINCL)
	{
	  symentry.n_value += bias;
	  lseek (new, -SYMESZ, SEEK_CUR);
	  write (new, &symentry, SYMESZ);
	}

      for (naux = symentry.n_numaux; naux-- != 0; )
	{
	  read (new, &auxentry, AUXESZ);
	  nsyms++;
	  if (naux != 0              /* skip csect auxentry (last entry) */
              && (symentry.n_sclass == C_EXT || symentry.n_sclass == C_HIDEXT))
            {
              auxentry.x_sym.x_fcnary.x_fcn.x_lnnoptr += bias;
              lseek (new, -AUXESZ, SEEK_CUR);
              write (new, &auxentry, AUXESZ);
            }
	}
    }
  close (new);

  return 0;
}

static int
unrelocate_symbols (int new, int a_out, char *a_name, char *new_name)
{
  int i;
  LDHDR ldhdr;
  LDREL ldrel;
  ulong t_reloc = (ulong) &_text - f_ohdr.text_start;
#ifndef ALIGN_DATA_RELOC
  ulong d_reloc = (ulong) &_data - f_ohdr.data_start;
#else
  /* This worked (and was needed) before AIX 4.2.
     I have no idea why. -- Mike */
  ulong d_reloc = (ulong) &_data - ALIGN(f_ohdr.data_start, 2);
#endif
  int * p;

  if (load_scnptr == 0)
    return 0;

  lseek (a_out, orig_load_scnptr, SEEK_SET);
  if (read (a_out, &ldhdr, sizeof (ldhdr)) != sizeof (ldhdr))
    {
      PERROR (new_name);
    }

#define SYMNDX_TEXT	0
#define SYMNDX_DATA	1
#define SYMNDX_BSS	2

  for (i = 0; i < ldhdr.l_nreloc; i++)
    {
      lseek (a_out,
	     orig_load_scnptr + LDHDRSZ + LDSYMSZ*ldhdr.l_nsyms + LDRELSZ*i,
	     SEEK_SET);

      if (read (a_out, &ldrel, LDRELSZ) != LDRELSZ)
	{
	  PERROR (a_name);
	}

      /* move the BSS loader symbols to the DATA segment */
      if (ldrel.l_symndx == SYMNDX_BSS)
	{
	  ldrel.l_symndx = SYMNDX_DATA;

	  lseek (new,
		 load_scnptr + LDHDRSZ + LDSYMSZ*ldhdr.l_nsyms + LDRELSZ*i,
		 SEEK_SET);

	  if (write (new, &ldrel, LDRELSZ) != LDRELSZ)
	    {
	      PERROR (new_name);
	    }
	}

      if (ldrel.l_rsecnm == f_ohdr.o_sndata)
	{
	  int orig_int;

	  lseek (a_out,
                 orig_data_scnptr + (ldrel.l_vaddr - f_ohdr.data_start),
		 SEEK_SET);

	  if (read (a_out, (void *) &orig_int, sizeof (orig_int))
	      != sizeof (orig_int))
	    {
	      PERROR (a_name);
	    }

          p = (int *) (ldrel.l_vaddr + d_reloc);

	  switch (ldrel.l_symndx) {
	  case SYMNDX_TEXT:
	    orig_int = * p - t_reloc;
	    break;

	  case SYMNDX_DATA:
	  case SYMNDX_BSS:
	    orig_int = * p - d_reloc;
	    break;
	  }

          if (orig_int != * p)
            {
              lseek (new,
                     data_scnptr + (ldrel.l_vaddr - f_ohdr.data_start),
		     SEEK_SET);
              if (write (new, (void *) &orig_int, sizeof (orig_int))
                  != sizeof (orig_int))
                {
                  PERROR (new_name);
                }
            }
	}
    }
  return 0;
}

/* arch-tag: 0783857a-7c2d-456f-a426-58b722d69fd0
   (do not change this comment) */