[deliverable/binutils-gdb.git] / mmalloc / mmap-sup.c

/* Support for an sbrk-like function that uses mmap.
   Copyright 1992, 2000 Free Software Foundation, Inc.

   Contributed by Fred Fish at Cygnus Support.   fnf@cygnus.com

This file is part of the GNU C Library.

The GNU C Library 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.

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

#if defined(HAVE_MMAP)

#ifdef HAVE_UNISTD_H
#include <unistd.h>	/* Prototypes for lseek */
#endif
#include <stdio.h>
#include <fcntl.h>
#include <sys/mman.h>

#ifndef SEEK_SET
#define SEEK_SET 0
#endif

#include "mmprivate.h"

/* Cache the pagesize for the current host machine.  Note that if the host
   does not readily provide a getpagesize() function, we need to emulate it
   elsewhere, not clutter up this file with lots of kluges to try to figure
   it out. */

static size_t pagesize;
#if NEED_DECLARATION_GETPAGESIZE
extern int getpagesize PARAMS ((void));
#endif

#define PAGE_ALIGN(addr) (caddr_t) (((long)(addr) + pagesize - 1) & \
				    ~(pagesize - 1))


/* Return MAP_PRIVATE if MDP represents /dev/zero.  Otherwise, return
   MAP_SHARED.  */

#define MAP_PRIVATE_OR_SHARED(MDP) ((MDP -> flags & MMALLOC_DEVZERO) \
                                    ? MAP_PRIVATE \
                                    : MAP_SHARED)


/*  Get core for the memory region specified by MDP, using SIZE as the
    amount to either add to or subtract from the existing region.  Works
    like sbrk(), but using mmap(). */

PTR
__mmalloc_mmap_morecore (mdp, size)
  struct mdesc *mdp;
  int size;
{
  PTR result = NULL;
  off_t foffset;	/* File offset at which new mapping will start */
  size_t mapbytes;	/* Number of bytes to map */
  caddr_t moveto;	/* Address where we wish to move "break value" to */
  caddr_t mapto;	/* Address we actually mapped to */
  char buf = 0;		/* Single byte to write to extend mapped file */

  if (pagesize == 0)
    {
      pagesize = getpagesize ();
    }
  if (size == 0)
    {
      /* Just return the current "break" value. */
      result = mdp -> breakval;
    }
  else if (size < 0)
    {
      /* We are deallocating memory.  If the amount requested would cause
	 us to try to deallocate back past the base of the mmap'd region
	 then do nothing, and return NULL.  Otherwise, deallocate the
	 memory and return the old break value. */
      if (mdp -> breakval + size >= mdp -> base)
	{
	  result = (PTR) mdp -> breakval;
	  mdp -> breakval += size;
	  moveto = PAGE_ALIGN (mdp -> breakval);
	  munmap (moveto, (size_t) (mdp -> top - moveto));
	  mdp -> top = moveto;
	}
    }
  else
    {
      /* We are allocating memory.  Make sure we have an open file
	 descriptor and then go on to get the memory. */
      if (mdp -> fd < 0)
	{
	  result = NULL;
	}
      else if (mdp -> breakval + size > mdp -> top)
	{
	  /* The request would move us past the end of the currently
	     mapped memory, so map in enough more memory to satisfy
	     the request.  This means we also have to grow the mapped-to
	     file by an appropriate amount, since mmap cannot be used
	     to extend a file. */
	  moveto = PAGE_ALIGN (mdp -> breakval + size);
	  mapbytes = moveto - mdp -> top;
	  foffset = mdp -> top - mdp -> base;
	  /* FIXME:  Test results of lseek() and write() */
	  lseek (mdp -> fd, foffset + mapbytes - 1, SEEK_SET);
	  write (mdp -> fd, &buf, 1);
	  if (mdp -> base == 0)
	    {
	      /* Let mmap pick the map start address */
	      mapto = mmap (0, mapbytes, PROT_READ | PROT_WRITE,
			    MAP_PRIVATE_OR_SHARED (mdp), mdp -> fd, foffset);
	      if (mapto != (caddr_t) -1)
		{
		  mdp -> base = mdp -> breakval = mapto;
		  mdp -> top = mdp -> base + mapbytes;
		  result = (PTR) mdp -> breakval;
		  mdp -> breakval += size;
		}
	    }
	  else
	    {
	      mapto = mmap (mdp -> top, mapbytes, PROT_READ | PROT_WRITE,
			    MAP_PRIVATE_OR_SHARED (mdp) | MAP_FIXED, mdp -> fd,
			    foffset);
	      if (mapto == mdp -> top)
		{
		  mdp -> top = moveto;
		  result = (PTR) mdp -> breakval;
		  mdp -> breakval += size;
		}
	    }
	}
      else
	{
	  result = (PTR) mdp -> breakval;
	  mdp -> breakval += size;
	}
    }
  return (result);
}

PTR
__mmalloc_remap_core (mdp)
  struct mdesc *mdp;
{
  caddr_t base;

  /* FIXME:  Quick hack, needs error checking and other attention. */

  base = mmap (mdp -> base, mdp -> top - mdp -> base,
	       PROT_READ | PROT_WRITE, MAP_PRIVATE_OR_SHARED (mdp) | MAP_FIXED,
	       mdp -> fd, 0);
  return ((PTR) base);
}

PTR
mmalloc_findbase (size)
  int size;
{
  int fd;
  int flags;
  caddr_t base = NULL;

#ifdef MAP_ANONYMOUS
  flags = MAP_PRIVATE | MAP_ANONYMOUS;
  fd = -1;
#else
#ifdef MAP_FILE
  flags = MAP_PRIVATE | MAP_FILE;
#else
  flags = MAP_PRIVATE;
#endif
  fd = open ("/dev/zero", O_RDWR);
  if (fd != -1)
    {
      return ((PTR) NULL);
    }
#endif
  base = mmap (0, size, PROT_READ | PROT_WRITE, flags, fd, 0);
  if (base != (caddr_t) -1)
    {
      munmap (base, (size_t) size);
    }
  if (fd != -1)
    {
      close (fd);
    }
  if (base == 0)
    {
      /* Don't allow mapping at address zero.  We use that value
	 to signal an error return, and besides, it is useful to
	 catch NULL pointers if it is unmapped.  Instead start
	 at the next page boundary. */
      base = (caddr_t) getpagesize ();
    }
  else if (base == (caddr_t) -1)
    {
      base = NULL;
    }
  return ((PTR) base);
}

#else	/* defined(HAVE_MMAP) */
/* Prevent "empty translation unit" warnings from the idiots at X3J11. */
static char ansi_c_idiots = 69;
#endif	/* defined(HAVE_MMAP) */
Commit	Line	Data
c906108c	1	/* Support for an sbrk-like function that uses mmap.
9365c12c	2	Copyright 1992, 2000 Free Software Foundation, Inc.
c906108c SS	3
	4	Contributed by Fred Fish at Cygnus Support. fnf@cygnus.com
	5
	6	This file is part of the GNU C Library.
	7
	8	The GNU C Library is free software; you can redistribute it and/or
	9	modify it under the terms of the GNU Library General Public License as
	10	published by the Free Software Foundation; either version 2 of the
	11	License, or (at your option) any later version.
	12
	13	The GNU C Library is distributed in the hope that it will be useful,
	14	but WITHOUT ANY WARRANTY; without even the implied warranty of
	15	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	16	Library General Public License for more details.
	17
	18	You should have received a copy of the GNU Library General Public
	19	License along with the GNU C Library; see the file COPYING.LIB. If
	20	not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
	21	Boston, MA 02111-1307, USA. */
	22
	23	#if defined(HAVE_MMAP)
	24
9365c12c AC	25	#ifdef HAVE_UNISTD_H
	26	#include <unistd.h> /* Prototypes for lseek */
	27	#endif
c906108c SS	28	#include <stdio.h>
	29	#include <fcntl.h>
	30	#include <sys/mman.h>
	31
	32	#ifndef SEEK_SET
	33	#define SEEK_SET 0
	34	#endif
	35
	36	#include "mmprivate.h"
	37
	38	/* Cache the pagesize for the current host machine. Note that if the host
	39	does not readily provide a getpagesize() function, we need to emulate it
	40	elsewhere, not clutter up this file with lots of kluges to try to figure
	41	it out. */
	42
	43	static size_t pagesize;
ff4e7bb2	44	#if NEED_DECLARATION_GETPAGESIZE
c906108c	45	extern int getpagesize PARAMS ((void));
ff4e7bb2	46	#endif
c906108c SS	47
	48	#define PAGE_ALIGN(addr) (caddr_t) (((long)(addr) + pagesize - 1) & \
	49	~(pagesize - 1))
	50
aeec20ba AC	51
	52	/* Return MAP_PRIVATE if MDP represents /dev/zero. Otherwise, return
	53	MAP_SHARED. */
	54
	55	#define MAP_PRIVATE_OR_SHARED(MDP) ((MDP -> flags & MMALLOC_DEVZERO) \
	56	? MAP_PRIVATE \
	57	: MAP_SHARED)
	58
	59
c906108c SS	60	/* Get core for the memory region specified by MDP, using SIZE as the
	61	amount to either add to or subtract from the existing region. Works
	62	like sbrk(), but using mmap(). */
	63
	64	PTR
	65	__mmalloc_mmap_morecore (mdp, size)
	66	struct mdesc *mdp;
	67	int size;
	68	{
	69	PTR result = NULL;
	70	off_t foffset; /* File offset at which new mapping will start */
	71	size_t mapbytes; /* Number of bytes to map */
	72	caddr_t moveto; /* Address where we wish to move "break value" to */
	73	caddr_t mapto; /* Address we actually mapped to */
	74	char buf = 0; /* Single byte to write to extend mapped file */
	75
	76	if (pagesize == 0)
	77	{
	78	pagesize = getpagesize ();
	79	}
	80	if (size == 0)
	81	{
	82	/* Just return the current "break" value. */
	83	result = mdp -> breakval;
	84	}
	85	else if (size < 0)
	86	{
	87	/* We are deallocating memory. If the amount requested would cause
	88	us to try to deallocate back past the base of the mmap'd region
	89	then do nothing, and return NULL. Otherwise, deallocate the
	90	memory and return the old break value. */
	91	if (mdp -> breakval + size >= mdp -> base)
	92	{
	93	result = (PTR) mdp -> breakval;
	94	mdp -> breakval += size;
	95	moveto = PAGE_ALIGN (mdp -> breakval);
	96	munmap (moveto, (size_t) (mdp -> top - moveto));
	97	mdp -> top = moveto;
	98	}
	99	}
	100	else
	101	{
	102	/* We are allocating memory. Make sure we have an open file
	103	descriptor and then go on to get the memory. */
	104	if (mdp -> fd < 0)
	105	{
	106	result = NULL;
	107	}
	108	else if (mdp -> breakval + size > mdp -> top)
	109	{
	110	/* The request would move us past the end of the currently
	111	mapped memory, so map in enough more memory to satisfy
	112	the request. This means we also have to grow the mapped-to
	113	file by an appropriate amount, since mmap cannot be used
	114	to extend a file. */
	115	moveto = PAGE_ALIGN (mdp -> breakval + size);
	116	mapbytes = moveto - mdp -> top;
	117	foffset = mdp -> top - mdp -> base;
	118	/* FIXME: Test results of lseek() and write() */
	119	lseek (mdp -> fd, foffset + mapbytes - 1, SEEK_SET);
	120	write (mdp -> fd, &buf, 1);
	121	if (mdp -> base == 0)
	122	{
	123	/* Let mmap pick the map start address */
124	mapto = mmap (0, mapbytes, PROT_READ \| PROT_WRITE,
aeec20ba	125	MAP_PRIVATE_OR_SHARED (mdp), mdp -> fd, foffset);
c906108c SS	126	if (mapto != (caddr_t) -1)
	127	{
	128	mdp -> base = mdp -> breakval = mapto;
	129	mdp -> top = mdp -> base + mapbytes;
	130	result = (PTR) mdp -> breakval;
	131	mdp -> breakval += size;
	132	}
	133	}
	134	else
	135	{
	136	mapto = mmap (mdp -> top, mapbytes, PROT_READ \| PROT_WRITE,
aeec20ba AC	137	MAP_PRIVATE_OR_SHARED (mdp) \| MAP_FIXED, mdp -> fd,
aeec20ba AC	138	foffset);
c906108c SS	139	if (mapto == mdp -> top)
	140	{
	141	mdp -> top = moveto;
	142	result = (PTR) mdp -> breakval;
	143	mdp -> breakval += size;
	144	}
	145	}
	146	}
	147	else
	148	{
	149	result = (PTR) mdp -> breakval;
	150	mdp -> breakval += size;
	151	}
	152	}
	153	return (result);
	154	}
	155
	156	PTR
	157	__mmalloc_remap_core (mdp)
	158	struct mdesc *mdp;
	159	{
	160	caddr_t base;
	161
	162	/* FIXME: Quick hack, needs error checking and other attention. */
	163
	164	base = mmap (mdp -> base, mdp -> top - mdp -> base,
aeec20ba	165	PROT_READ \| PROT_WRITE, MAP_PRIVATE_OR_SHARED (mdp) \| MAP_FIXED,
c906108c SS	166	mdp -> fd, 0);
	167	return ((PTR) base);
	168	}
	169
	170	PTR
	171	mmalloc_findbase (size)
	172	int size;
	173	{
	174	int fd;
	175	int flags;
	176	caddr_t base = NULL;
	177
	178	#ifdef MAP_ANONYMOUS
aeec20ba	179	flags = MAP_PRIVATE \| MAP_ANONYMOUS;
c906108c SS	180	fd = -1;
	181	#else
	182	#ifdef MAP_FILE
aeec20ba	183	flags = MAP_PRIVATE \| MAP_FILE;
c906108c	184	#else
aeec20ba	185	flags = MAP_PRIVATE;
c906108c SS	186	#endif
	187	fd = open ("/dev/zero", O_RDWR);
	188	if (fd != -1)
	189	{
	190	return ((PTR) NULL);
	191	}
	192	#endif
	193	base = mmap (0, size, PROT_READ \| PROT_WRITE, flags, fd, 0);
	194	if (base != (caddr_t) -1)
	195	{
	196	munmap (base, (size_t) size);
	197	}
	198	if (fd != -1)
	199	{
	200	close (fd);
	201	}
	202	if (base == 0)
	203	{
	204	/* Don't allow mapping at address zero. We use that value
	205	to signal an error return, and besides, it is useful to
	206	catch NULL pointers if it is unmapped. Instead start
	207	at the next page boundary. */
	208	base = (caddr_t) getpagesize ();
	209	}
	210	else if (base == (caddr_t) -1)
	211	{
	212	base = NULL;
	213	}
	214	return ((PTR) base);
	215	}
	216
	217	#else /* defined(HAVE_MMAP) */
	218	/* Prevent "empty translation unit" warnings from the idiots at X3J11. */
	219	static char ansi_c_idiots = 69;
	220	#endif /* defined(HAVE_MMAP) */