Miscellaneous constification.

[u/mdw/catacomb] / lmem.c

/* -*-c-*-
 *
 * $Id: lmem.c,v 1.5 2004/04/02 01:03:49 mdw Exp $
 *
 * Locked memory allocation (Unix-specific)
 *
 * (c) 1999 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------* 
 *
 * This file is part of Catacomb.
 *
 * Catacomb is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Library General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 * 
 * Catacomb 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 Library General Public License for more details.
 * 
 * You should have received a copy of the GNU Library General Public
 * License along with Catacomb; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/*----- Revision history --------------------------------------------------* 
 *
 * $Log: lmem.c,v $
 * Revision 1.5  2004/04/02 01:03:49  mdw
 * Miscellaneous constification.
 *
 * Revision 1.4  2002/01/24 22:26:11  mdw
 * Fix build failure when @mlock@ not available.
 *
 * Revision 1.3  2000/07/29 21:58:15  mdw
 * (l_destroy): New function for destroying locked memory blocks.
 *
 * Revision 1.2  2000/06/17 11:29:20  mdw
 * Add arena support.
 *
 * Revision 1.1  1999/12/22 16:02:52  mdw
 * Interface to allocating `locked' memory (which isn't paged out).
 *
 */

/*----- Header files ------------------------------------------------------*/

#include "config.h"

#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <sys/types.h>
#include <unistd.h>

#ifdef HAVE_MLOCK
#  include <sys/mman.h>
#endif

#include <mLib/arena.h>
#include <mLib/dstr.h>
#include <mLib/sub.h>

#include "lmem.h"

/*----- Arena operations --------------------------------------------------*/

static void *aalloc(arena *a, size_t sz) { return l_alloc((lmem *)a, sz); }
static void afree(arena *a, void *p) { l_free((lmem *)a, p); }
static void apurge(arena *a) { l_purge((lmem *)a); }

static const arena_ops l_ops = { aalloc, arena_fakerealloc, afree, apurge };

/*----- Main code ---------------------------------------------------------*/

/* --- @l_init@ --- *
 *
 * Arguments:	@lmem *lm@ = pointer to locked memory descriptor
 *		@size_t sz@ = size of locked memory area requested
 *
 * Returns:	Zero if everything is fine, @+1@ if some insecure memory was
 *		allocated, and @-1@ if everything went horribly wrong.
 *
 * Use:		Initializes the locked memory manager.  This function is safe
 *		to call in a privileged program; privileges should usually be
 *		dropped after allocating the locked memory block.
 *
 *		You must call @sub_init@ before allocating locked memory
 *		buffers.
 */

int l_init(lmem *lm, size_t sz)
{
  char *p;
  int rc = 0;
  l_node *l;

  /* --- Preliminaries --- */

  lm->a.ops = &l_ops;
  lm->err = 0;
  lm->f = 0;

  /* --- Try making a secure locked passphrase buffer --- *
   *
   * Drop privileges before emitting diagnostic messages.
   */

#ifdef HAVE_MLOCK

  /* --- Memory-map a page from somewhere --- */

#  ifdef MAP_ANON
  p = mmap(0, sz, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
#  else
  {
    int fd;
    if ((fd = open("/dev/zero", O_RDWR)) >= 0) {
      p = mmap(0, sz, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
      close(fd);
    }
  }
#  endif

  /* --- Lock the page in memory --- *
   *
   * Why does @mmap@ return such a stupid result if it fails?
   */

  if (p == 0 || p == MAP_FAILED) {
    lm->emsg = "couldn't map locked memory area: %s";
    lm->err = errno;
    p = 0;
  } else if (mlock(p, sz)) {
    lm->emsg = "error locking memory area: %s";
    lm->err = errno;
    munmap(p, sz);
    p = 0;
  } else
    lm->f |= LF_LOCKED;

#endif

  /* --- Make a standard passphrase buffer --- */

#ifdef HAVE_MLOCK
  if (!p)
#else
  lm->err = 0;
  lm->emsg = "locked memory not available on this system";
#endif
  {
    if ((p = malloc(sz)) == 0) {
      lm->emsg = "not enough standard memory!";
      lm->err = ENOMEM;
      return (-1);
    }
    rc = +1;
  }

  /* --- Initialize the buffer --- */

  lm->sz = lm->free = sz;
  lm->p = p;

  /* --- Initialize the free list --- */

  l = CREATE(l_node);
  l->next = 0;
  l->p = p;
  l->sz = sz;
  l->f = 0;
  lm->l = l;

  /* --- Done --- */

  return (rc);
}

/* --- @l_alloc@ --- *
 *
 * Arguments:	@lmem *lm@ = pointer to locked memory descriptor
 *		@size_t sz@ = size requested
 *
 * Returns:	Pointer to allocated memory.
 *
 * Use:		Allocates @sz@ bytes of locked memory.
 */

void *l_alloc(lmem *lm, size_t sz)
{
  l_node *l;

  sz = (sz + 3u) & ~3u;
  for (l = lm->l; l; l = l->next) {
    if (l->f & LF_ALLOC)
      continue;
    if (l->sz < sz)
      continue;
    l->f |= LF_ALLOC;
    if (l->sz > sz) {
      l_node *n = CREATE(l_node);
      n->next = l->next;
      n->p = l->p + sz;
      n->sz = l->sz - sz;
      l->sz = sz;
      n->f = 0;
      l->next = n;
    }
    assert(((void)"Locked buffer space has vanished", lm->free >= sz));
    lm->free -= sz;
    return (l->p);
  }
  return (0);
}

/* --- @l_free@ --- *
 *
 * Arguments:	@lmem *lm@ = pointer to locked memory descriptor
 *		@void *p@ = pointer to block
 *
 * Returns:	---
 *
 * Use:		Releases a block of locked memory.
 */

void l_free(lmem *lm, void *p)
{
  l_node *l;
  l_node *ll = 0;

  for (l = lm->l; l; l = l->next) {
    size_t sz;

    /* --- If this isn't the block, skip it --- */

    if (l->p != p) {
      ll = l;
      continue;
    }
    assert(((void)"Block is already free", l->f & LF_ALLOC));

    /* --- Coalesce with adjacent free blocks --- */

    l->f &= ~LF_ALLOC;
    sz = l->sz;
    memset(p, 0, sz);

    if (ll && !(ll->f & LF_ALLOC)) {
      assert(((void)"Previous block doesn't fit", ll->p + ll->sz == p));
      ll->sz += sz;
      ll->next = l->next;
      DESTROY(l);
      l = ll;
    }

    ll = l->next;
    if (ll && !(ll->f & LF_ALLOC)) {
      assert(((void)"Next block doesn't fit", ll->p == l->p + l->sz));
      l->sz += ll->sz;
      l->next = ll->next;
      DESTROY(ll);
    }

    lm->free += sz;
    assert(((void)"Free lunch", lm->free <= lm->sz));
    return;
  }
  assert(((void)"Not a locked block", 0));
}

/* --- @l_purge@ --- *
 *
 * Arguments:	@lmem *lm@ = pointer to locked memory descriptor
 *
 * Returns:	---
 *
 * Use:		Purges all the free blocks in the buffer, and clears all of
 *		the locked memory.  Memory is not freed back to the system.
 */

void l_purge(lmem *lm)
{
  l_node *l;

  l = lm->l;
  while (l) {
    l_node *ll = l->next;
    DESTROY(l);
    l = ll;
  }
  memset(lm->p, 0, lm->sz);
  l = CREATE(l_node);
  l->next = 0;
  l->p = lm->p;
  l->sz = lm->sz;
  l->f = 0;
  lm->l = l;
  lm->free = l->sz;
}

/* --- @l_destroy@ --- *
 *
 * Arguments:	@lmem *lm@ = pointer to locked memory descriptor
 *
 * Returns:	---
 *
 * Use:		Disposes of a locked memory arena permanently.
 */

void l_destroy(lmem *lm)
{
  l_node *l;

  l = lm->l;
  while (l) {
    l_node *ll = l->next;
    DESTROY(l);
    l = ll;
  }
  memset(lm->p, 0, lm->sz);

  if (lm->f & LF_LOCKED)
    munmap(lm->p, lm->sz);
  else
    free(lm->p);
}

/* --- @l_report@ --- *
 *
 * Arguments:	@lmem *lm@ = pointer to locked memory descriptor
 *		@dstr *d@ = string to write the error message on
 *
 * Returns:	Zero if the buffer is fine, @+1@ if there was a problem
 *		getting locked memory but insecure stuff could be allocated,
 *		and @-1@ if not even insecure memory could be found.
 *
 * Use:		Returns a user-digestable explanation for the state of a
 *		locked memory buffer.  If the return code is zero, no message
 *		is emitted to the string @d@.
 */

int l_report(lmem *lm, dstr *d)
{
  int rc;
  if (lm->err)
    dstr_putf(d, lm->emsg, strerror(lm->err));
  if (!lm->p)
    rc = -1;
  else if (lm->err)
    rc = +1;
  else
    rc = 0;
  return (rc);
}

/*----- That's all, folks -------------------------------------------------*/