src/Unix/vm_alloc.cpp

/*
 *  vm_alloc.cpp - Wrapper to various virtual memory allocation schemes
 *                 (supports mmap, vm_allocate or fallbacks to malloc)
 *
 *  Basilisk II (C) 1997-2004 Christian Bauer
 *
 *  This program 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 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif

// TODO: Win32 VMs ?
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include "vm_alloc.h"

#ifdef HAVE_MACH_VM
#ifndef HAVE_MACH_TASK_SELF
#ifdef HAVE_TASK_SELF
#define mach_task_self task_self
#else
#error "No task_self(), you lose."
#endif
#endif
#endif

/* We want MAP_32BIT, if available, for SheepShaver and BasiliskII
   because the emulated target is 32-bit and this helps to allocate
   memory so that branches could be resolved more easily (32-bit
   displacement to code in .text), on AMD64 for example.  */
#ifndef MAP_32BIT
#define MAP_32BIT 0
#endif
#ifndef MAP_ANON
#define MAP_ANON 0
#endif
#ifndef MAP_ANONYMOUS
#define MAP_ANONYMOUS 0
#endif

#define MAP_EXTRA_FLAGS (MAP_32BIT)

#ifdef HAVE_MMAP_VM
#if defined(__linux__) && defined(__i386__)
/* Force a reasonnable address below 0x80000000 on x86 so that we
   don't get addresses above when the program is run on AMD64.
   NOTE: this is empirically determined on Linux/x86.  */
#define MAP_BASE        0x10000000
#else
#define MAP_BASE        0x00000000
#endif
static char * next_address = (char *)MAP_BASE;
#ifdef HAVE_MMAP_ANON
#define map_flags       (MAP_ANON | MAP_EXTRA_FLAGS)
#define zero_fd         -1
#else
#ifdef HAVE_MMAP_ANONYMOUS
#define map_flags       (MAP_ANONYMOUS | MAP_EXTRA_FLAGS)
#define zero_fd         -1
#else
#define map_flags       (MAP_EXTRA_FLAGS)
static int zero_fd      = -1;
#endif
#endif
#endif

/* Utility functions for POSIX SHM handling.  */

#ifdef USE_33BIT_ADDRESSING
struct shm_range_t {
        const char *file;
        void *base;
        unsigned int size;
        shm_range_t *next;
};

static shm_range_t *shm_ranges = NULL;

static bool add_shm_range(const char *file, void *base, unsigned int size)
{
        shm_range_t *r = (shm_range_t *)malloc(sizeof(shm_range_t));
        if (r) {
                r->file = file;
                r->base = base;
                r->size = size;
                r->next = shm_ranges ? shm_ranges : NULL;
                shm_ranges = r;
                return true;
        }
        return false;
}

static shm_range_t *find_shm_range(void *base, unsigned int size)
{
        for (shm_range_t *r = shm_ranges; r != NULL; r = r->next)
                if (r->base == base && r->size == size)
                        return r;
        return NULL;
}

static bool remove_shm_range(shm_range_t *r)
{
        if (r) {
                for (shm_range_t *p = shm_ranges; p != NULL; p = p->next) {
                        if (p->next == r) {
                                p->next = r->next;
                                free(r);
                                return true;
                        }
                }
        }
        return false;
}

static bool remove_shm_range(void *base, unsigned int size)
{
        remove_shm_range(find_shm_range(base, size));
}
#endif

/* Build a POSIX SHM memory segment file descriptor name.  */

#ifdef USE_33BIT_ADDRESSING
static const char *build_shm_filename(void)
{
        static int id = 0;
        static char filename[PATH_MAX];
        
        int ret = snprintf(filename, sizeof(filename), "/BasiliskII-%d-shm-%d", getpid(), id);
        if (ret == -1 || ret >= sizeof(filename))
                return NULL;

        id++;
        return filename;
}
#endif

/* Translate generic VM map flags to host values.  */

#ifdef HAVE_MMAP_VM
static int translate_map_flags(int vm_flags)
{
        int flags = 0;
        if (vm_flags & VM_MAP_SHARED)
                flags |= MAP_SHARED;
        if (vm_flags & VM_MAP_PRIVATE)
                flags |= MAP_PRIVATE;
        if (vm_flags & VM_MAP_FIXED)
                flags |= MAP_FIXED;
        if (vm_flags & VM_MAP_32BIT)
                flags |= MAP_32BIT;
        return flags;
}
#endif

/* Initialize the VM system. Returns 0 if successful, -1 for errors.  */

int vm_init(void)
{
#ifdef HAVE_MMAP_VM
#ifndef zero_fd
        zero_fd = open("/dev/zero", O_RDWR);
        if (zero_fd < 0)
                return -1;
#endif
#endif
        return 0;
}

/* Deallocate all internal data used to wrap virtual memory allocators.  */

void vm_exit(void)
{
#ifdef HAVE_MMAP_VM
#ifndef zero_fd
        close(zero_fd);
#endif
#endif
}

/* Allocate zero-filled memory of SIZE bytes. The mapping is private
   and default protection bits are read / write. The return value
   is the actual mapping address chosen or VM_MAP_FAILED for errors.  */

void * vm_acquire(size_t size, int options)
{
        void * addr;

        // VM_MAP_FIXED are to be used with vm_acquire_fixed() only
        if (options & VM_MAP_FIXED)
                return VM_MAP_FAILED;

#ifdef HAVE_MACH_VM
        // vm_allocate() returns a zero-filled memory region
        if (vm_allocate(mach_task_self(), (vm_address_t *)&addr, size, TRUE) != KERN_SUCCESS)
                return VM_MAP_FAILED;
#else
#ifdef HAVE_MMAP_VM
        int fd = zero_fd;
        int the_map_flags = translate_map_flags(options) | map_flags;

#ifdef USE_33BIT_ADDRESSING
        const char *shm_file = NULL;
        if (sizeof(void *) == 8 && (options & VM_MAP_33BIT)) {
                the_map_flags &= ~(MAP_PRIVATE | MAP_ANON | MAP_ANONYMOUS);
                the_map_flags |= MAP_SHARED;

                if ((shm_file = build_shm_filename()) == NULL)
                        return VM_MAP_FAILED;

                if ((fd = shm_open(shm_file, O_RDWR | O_CREAT | O_EXCL, 0644)) < 0)
                        return VM_MAP_FAILED;

                if (ftruncate(fd, size) < 0)
                        return VM_MAP_FAILED;

                the_map_flags |= MAP_SHARED;
        }
#endif

        if ((addr = mmap((caddr_t)next_address, size, VM_PAGE_DEFAULT, the_map_flags, fd, 0)) == (void *)MAP_FAILED)
                return VM_MAP_FAILED;
        
        // Sanity checks for 64-bit platforms
        if (sizeof(void *) == 8 && (options & VM_MAP_32BIT) && !((char *)addr <= (char *)0xffffffff))
                return VM_MAP_FAILED;

        next_address = (char *)addr + size;
        
        // Since I don't know the standard behavior of mmap(), zero-fill here
        if (memset(addr, 0, size) != addr)
                return VM_MAP_FAILED;

        // Remap to 33-bit space
#ifdef USE_33BIT_ADDRESSING
        if (sizeof(void *) == 8 && (options & VM_MAP_33BIT)) {
                if (!add_shm_range(strdup(shm_file), addr, size))
                        return VM_MAP_FAILED;

                if (mmap((char *)addr + (1L << 32), size, VM_PAGE_DEFAULT, the_map_flags | MAP_FIXED, fd, 0) == (void *)MAP_FAILED)
                        return VM_MAP_FAILED;
                close(fd);
        }
#endif
#else
        if ((addr = calloc(size, 1)) == 0)
                return VM_MAP_FAILED;
        
        // Omit changes for protections because they are not supported in this mode
        return addr;
#endif
#endif

        // Explicitely protect the newly mapped region here because on some systems,
        // say MacOS X, mmap() doesn't honour the requested protection flags.
        if (vm_protect(addr, size, VM_PAGE_DEFAULT) != 0)
                return VM_MAP_FAILED;
        
        return addr;
}

/* Allocate zero-filled memory at exactly ADDR (which must be page-aligned).
   Retuns 0 if successful, -1 on errors.  */

int vm_acquire_fixed(void * addr, size_t size, int options)
{
        // Fixed mappings are required to be private
        if (options & VM_MAP_SHARED)
                return -1;

#ifdef HAVE_MACH_VM
        // vm_allocate() returns a zero-filled memory region
        if (vm_allocate(mach_task_self(), (vm_address_t *)&addr, size, 0) != KERN_SUCCESS)
                return -1;
#else
#ifdef HAVE_MMAP_VM
        const int extra_map_flags = translate_map_flags(options);

        if (mmap((caddr_t)addr, size, VM_PAGE_DEFAULT, extra_map_flags | map_flags | MAP_FIXED, zero_fd, 0) == (void *)MAP_FAILED)
                return -1;
        
        // Since I don't know the standard behavior of mmap(), zero-fill here
        if (memset(addr, 0, size) != addr)
                return -1;
#else
        // Unsupported
        return -1;
#endif
#endif
        
        // Explicitely protect the newly mapped region here because on some systems,
        // say MacOS X, mmap() doesn't honour the requested protection flags.
        if (vm_protect(addr, size, VM_PAGE_DEFAULT) != 0)
                return -1;
        
        return 0;
}

/* Deallocate any mapping for the region starting at ADDR and extending
   LEN bytes. Returns 0 if successful, -1 on errors.  */

int vm_release(void * addr, size_t size)
{
        // Safety check: don't try to release memory that was not allocated
        if (addr == VM_MAP_FAILED)
                return 0;

#ifdef HAVE_MACH_VM
        if (vm_deallocate(mach_task_self(), (vm_address_t)addr, size) != KERN_SUCCESS)
                return -1;
#else
#ifdef HAVE_MMAP_VM
        if (munmap((caddr_t)addr, size) != 0)
                return -1;

#ifdef USE_33BIT_ADDRESSING
        shm_range_t *r = find_shm_range(addr, size);
        if (r) {
                if (munmap((char *)r->base + (1L << 32), size) != 0)
                        return -1;

                if (shm_unlink(r->file) < 0)
                        return -1;
                free((char *)r->file);

                if (!remove_shm_range(r))
                        return -1;
        }
#endif
#else
        free(addr);
#endif
#endif
        
        return 0;
}

/* Change the memory protection of the region starting at ADDR and
   extending LEN bytes to PROT. Returns 0 if successful, -1 for errors.  */

int vm_protect(void * addr, size_t size, int prot)
{
#ifdef HAVE_MACH_VM
        int ret_code = vm_protect(mach_task_self(), (vm_address_t)addr, size, 0, prot);
        return ret_code == KERN_SUCCESS ? 0 : -1;
#else
#ifdef HAVE_MMAP_VM
        int ret_code = mprotect((caddr_t)addr, size, prot);
        return ret_code == 0 ? 0 : -1;
#else
        // Unsupported
        return -1;
#endif
#endif
}

#ifdef CONFIGURE_TEST_VM_MAP
/* Tests covered here:
   - TEST_VM_PROT_* program slices actually succeeds when a crash occurs
   - TEST_VM_MAP_ANON* program slices succeeds when it could be compiled
*/
int main(void)
{
        vm_init();
        
#define page_align(address) ((char *)((unsigned long)(address) & -page_size))
        unsigned long page_size = getpagesize();
        
        const int area_size = 6 * page_size;
        volatile char * area = (volatile char *) vm_acquire(area_size);
        volatile char * fault_address = area + (page_size * 7) / 2;

#if defined(TEST_VM_MMAP_ANON) || defined(TEST_VM_MMAP_ANONYMOUS)
        if (area == VM_MAP_FAILED)
                return 1;

        if (vm_release((char *)area, area_size) < 0)
                return 1;
        
        return 0;
#endif

#if defined(TEST_VM_PROT_NONE_READ) || defined(TEST_VM_PROT_NONE_WRITE)
        if (area == VM_MAP_FAILED)
                return 0;
        
        if (vm_protect(page_align(fault_address), page_size, VM_PAGE_NOACCESS) < 0)
                return 0;
#endif

#if defined(TEST_VM_PROT_RDWR_WRITE)
        if (area == VM_MAP_FAILED)
                return 1;
        
        if (vm_protect(page_align(fault_address), page_size, VM_PAGE_READ) < 0)
                return 1;
        
        if (vm_protect(page_align(fault_address), page_size, VM_PAGE_READ | VM_PAGE_WRITE) < 0)
                return 1;
#endif

#if defined(TEST_VM_PROT_READ_WRITE)
        if (vm_protect(page_align(fault_address), page_size, VM_PAGE_READ) < 0)
                return 0;
#endif

#if defined(TEST_VM_PROT_NONE_READ)
        // this should cause a core dump
        char foo = *fault_address;
        return 0;
#endif

#if defined(TEST_VM_PROT_NONE_WRITE) || defined(TEST_VM_PROT_READ_WRITE)
        // this should cause a core dump
        *fault_address = 'z';
        return 0;
#endif

#if defined(TEST_VM_PROT_RDWR_WRITE)
        // this should not cause a core dump
        *fault_address = 'z';
        return 0;
#endif
}
#endif
Revision:	1.13
Committed:	2004-11-08T21:07:07Z (20 years ago) by gbeauche
Branch:	MAIN
Changes since 1.12:	+132 -5 lines
Log Message:	Enable 33-bit memory addressing on 64-bit JIT capable platforms (e.g. x86-64). This is useful to get rid of address offset sign extensions. It uses POSIX shared memory to create aliased regions, fallback to usual sign-extension way if shm_open et al. don't work (e.g. no /dev/shm mounted)
#	Content
1	/*
2	* vm_alloc.cpp - Wrapper to various virtual memory allocation schemes
3	* (supports mmap, vm_allocate or fallbacks to malloc)
4	*
5	* Basilisk II (C) 1997-2004 Christian Bauer
6	*
7	* This program is free software; you can redistribute it and/or modify
8	* it under the terms of the GNU General Public License as published by
9	* the Free Software Foundation; either version 2 of the License, or
10	* (at your option) any later version.
11	*
12	* This program is distributed in the hope that it will be useful,
13	* but WITHOUT ANY WARRANTY; without even the implied warranty of
14	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15	* GNU General Public License for more details.
16	*
17	* You should have received a copy of the GNU General Public License
18	* along with this program; if not, write to the Free Software
19	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20	*/
21
22	#ifdef HAVE_CONFIG_H
23	#include "config.h"
24	#endif
25
26	#ifdef HAVE_FCNTL_H
27	#include <fcntl.h>
28	#endif
29
30	// TODO: Win32 VMs ?
31	#include <stdio.h>
32	#include <stdlib.h>
33	#include <string.h>
34	#include <limits.h>
35	#include "vm_alloc.h"
36
37	#ifdef HAVE_MACH_VM
38	#ifndef HAVE_MACH_TASK_SELF
39	#ifdef HAVE_TASK_SELF
40	#define mach_task_self task_self
41	#else
42	#error "No task_self(), you lose."
43	#endif
44	#endif
45	#endif
46
47	/* We want MAP_32BIT, if available, for SheepShaver and BasiliskII
48	because the emulated target is 32-bit and this helps to allocate
49	memory so that branches could be resolved more easily (32-bit
50	displacement to code in .text), on AMD64 for example. */
51	#ifndef MAP_32BIT
52	#define MAP_32BIT 0
53	#endif
54	#ifndef MAP_ANON
55	#define MAP_ANON 0
56	#endif
57	#ifndef MAP_ANONYMOUS
58	#define MAP_ANONYMOUS 0
59	#endif
60
61	#define MAP_EXTRA_FLAGS (MAP_32BIT)
62
63	#ifdef HAVE_MMAP_VM
64	#if defined(__linux__) && defined(__i386__)
65	/* Force a reasonnable address below 0x80000000 on x86 so that we
66	don't get addresses above when the program is run on AMD64.
67	NOTE: this is empirically determined on Linux/x86. */
68	#define MAP_BASE 0x10000000
69	#else
70	#define MAP_BASE 0x00000000
71	#endif
72	static char * next_address = (char *)MAP_BASE;
73	#ifdef HAVE_MMAP_ANON
74	#define map_flags (MAP_ANON \| MAP_EXTRA_FLAGS)
75	#define zero_fd -1
76	#else
77	#ifdef HAVE_MMAP_ANONYMOUS
78	#define map_flags (MAP_ANONYMOUS \| MAP_EXTRA_FLAGS)
79	#define zero_fd -1
80	#else
81	#define map_flags (MAP_EXTRA_FLAGS)
82	static int zero_fd = -1;
83	#endif
84	#endif
85	#endif
86
87	/* Utility functions for POSIX SHM handling. */
88
89	#ifdef USE_33BIT_ADDRESSING
90	struct shm_range_t {
91	const char *file;
92	void *base;
93	unsigned int size;
94	shm_range_t *next;
95	};
96
97	static shm_range_t *shm_ranges = NULL;
98
99	static bool add_shm_range(const char file, void base, unsigned int size)
100	{
101	shm_range_t r = (shm_range_t )malloc(sizeof(shm_range_t));
102	if (r) {
103	r->file = file;
104	r->base = base;
105	r->size = size;
106	r->next = shm_ranges ? shm_ranges : NULL;
107	shm_ranges = r;
108	return true;
109	}
110	return false;
111	}
112
113	static shm_range_t find_shm_range(void base, unsigned int size)
114	{
115	for (shm_range_t *r = shm_ranges; r != NULL; r = r->next)
116	if (r->base == base && r->size == size)
117	return r;
118	return NULL;
119	}
120
121	static bool remove_shm_range(shm_range_t *r)
122	{
123	if (r) {
124	for (shm_range_t *p = shm_ranges; p != NULL; p = p->next) {
125	if (p->next == r) {
126	p->next = r->next;
127	free(r);
128	return true;
129	}
130	}
131	}
132	return false;
133	}
134
135	static bool remove_shm_range(void *base, unsigned int size)
136	{
137	remove_shm_range(find_shm_range(base, size));
138	}
139	#endif
140
141	/* Build a POSIX SHM memory segment file descriptor name. */
142
143	#ifdef USE_33BIT_ADDRESSING
144	static const char *build_shm_filename(void)
145	{
146	static int id = 0;
147	static char filename[PATH_MAX];
148
149	int ret = snprintf(filename, sizeof(filename), "/BasiliskII-%d-shm-%d", getpid(), id);
150	if (ret == -1 \|\| ret >= sizeof(filename))
151	return NULL;
152
153	id++;
154	return filename;
155	}
156	#endif
157
158	/* Translate generic VM map flags to host values. */
159
160	#ifdef HAVE_MMAP_VM
161	static int translate_map_flags(int vm_flags)
162	{
163	int flags = 0;
164	if (vm_flags & VM_MAP_SHARED)
165	flags \|= MAP_SHARED;
166	if (vm_flags & VM_MAP_PRIVATE)
167	flags \|= MAP_PRIVATE;
168	if (vm_flags & VM_MAP_FIXED)
169	flags \|= MAP_FIXED;
170	if (vm_flags & VM_MAP_32BIT)
171	flags \|= MAP_32BIT;
172	return flags;
173	}
174	#endif
175
176	/* Initialize the VM system. Returns 0 if successful, -1 for errors. */
177
178	int vm_init(void)
179	{
180	#ifdef HAVE_MMAP_VM
181	#ifndef zero_fd
182	zero_fd = open("/dev/zero", O_RDWR);
183	if (zero_fd < 0)
184	return -1;
185	#endif
186	#endif
187	return 0;
188	}
189
190	/* Deallocate all internal data used to wrap virtual memory allocators. */
191
192	void vm_exit(void)
193	{
194	#ifdef HAVE_MMAP_VM
195	#ifndef zero_fd
196	close(zero_fd);
197	#endif
198	#endif
199	}
200
201	/* Allocate zero-filled memory of SIZE bytes. The mapping is private
202	and default protection bits are read / write. The return value
203	is the actual mapping address chosen or VM_MAP_FAILED for errors. */
204
205	void * vm_acquire(size_t size, int options)
206	{
207	void * addr;
208
209	// VM_MAP_FIXED are to be used with vm_acquire_fixed() only
210	if (options & VM_MAP_FIXED)
211	return VM_MAP_FAILED;
212
213	#ifdef HAVE_MACH_VM
214	// vm_allocate() returns a zero-filled memory region
215	if (vm_allocate(mach_task_self(), (vm_address_t *)&addr, size, TRUE) != KERN_SUCCESS)
216	return VM_MAP_FAILED;
217	#else
218	#ifdef HAVE_MMAP_VM
219	int fd = zero_fd;
220	int the_map_flags = translate_map_flags(options) \| map_flags;
221
222	#ifdef USE_33BIT_ADDRESSING
223	const char *shm_file = NULL;
224	if (sizeof(void *) == 8 && (options & VM_MAP_33BIT)) {
225	the_map_flags &= ~(MAP_PRIVATE \| MAP_ANON \| MAP_ANONYMOUS);
226	the_map_flags \|= MAP_SHARED;
227
228	if ((shm_file = build_shm_filename()) == NULL)
229	return VM_MAP_FAILED;
230
231	if ((fd = shm_open(shm_file, O_RDWR \| O_CREAT \| O_EXCL, 0644)) < 0)
232	return VM_MAP_FAILED;
233
234	if (ftruncate(fd, size) < 0)
235	return VM_MAP_FAILED;
236
237	the_map_flags \|= MAP_SHARED;
238	}
239	#endif
240
241	if ((addr = mmap((caddr_t)next_address, size, VM_PAGE_DEFAULT, the_map_flags, fd, 0)) == (void *)MAP_FAILED)
242	return VM_MAP_FAILED;
243
244	// Sanity checks for 64-bit platforms
245	if (sizeof(void ) == 8 && (options & VM_MAP_32BIT) && !((char )addr <= (char *)0xffffffff))
246	return VM_MAP_FAILED;
247
248	next_address = (char *)addr + size;
249
250	// Since I don't know the standard behavior of mmap(), zero-fill here
251	if (memset(addr, 0, size) != addr)
252	return VM_MAP_FAILED;
253
254	// Remap to 33-bit space
255	#ifdef USE_33BIT_ADDRESSING
256	if (sizeof(void *) == 8 && (options & VM_MAP_33BIT)) {
257	if (!add_shm_range(strdup(shm_file), addr, size))
258	return VM_MAP_FAILED;
259
260	if (mmap((char )addr + (1L << 32), size, VM_PAGE_DEFAULT, the_map_flags \| MAP_FIXED, fd, 0) == (void )MAP_FAILED)
261	return VM_MAP_FAILED;
262	close(fd);
263	}
264	#endif
265	#else
266	if ((addr = calloc(size, 1)) == 0)
267	return VM_MAP_FAILED;
268
269	// Omit changes for protections because they are not supported in this mode
270	return addr;
271	#endif
272	#endif
273
274	// Explicitely protect the newly mapped region here because on some systems,
275	// say MacOS X, mmap() doesn't honour the requested protection flags.
276	if (vm_protect(addr, size, VM_PAGE_DEFAULT) != 0)
277	return VM_MAP_FAILED;
278
279	return addr;
280	}
281
282	/* Allocate zero-filled memory at exactly ADDR (which must be page-aligned).
283	Retuns 0 if successful, -1 on errors. */
284
285	int vm_acquire_fixed(void * addr, size_t size, int options)
286	{
287	// Fixed mappings are required to be private
288	if (options & VM_MAP_SHARED)
289	return -1;
290
291	#ifdef HAVE_MACH_VM
292	// vm_allocate() returns a zero-filled memory region
293	if (vm_allocate(mach_task_self(), (vm_address_t *)&addr, size, 0) != KERN_SUCCESS)
294	return -1;
295	#else
296	#ifdef HAVE_MMAP_VM
297	const int extra_map_flags = translate_map_flags(options);
298
299	if (mmap((caddr_t)addr, size, VM_PAGE_DEFAULT, extra_map_flags \| map_flags \| MAP_FIXED, zero_fd, 0) == (void *)MAP_FAILED)
300	return -1;
301
302	// Since I don't know the standard behavior of mmap(), zero-fill here
303	if (memset(addr, 0, size) != addr)
304	return -1;
305	#else
306	// Unsupported
307	return -1;
308	#endif
309	#endif
310
311	// Explicitely protect the newly mapped region here because on some systems,
312	// say MacOS X, mmap() doesn't honour the requested protection flags.
313	if (vm_protect(addr, size, VM_PAGE_DEFAULT) != 0)
314	return -1;
315
316	return 0;
317	}
318
319	/* Deallocate any mapping for the region starting at ADDR and extending
320	LEN bytes. Returns 0 if successful, -1 on errors. */
321
322	int vm_release(void * addr, size_t size)
323	{
324	// Safety check: don't try to release memory that was not allocated
325	if (addr == VM_MAP_FAILED)
326	return 0;
327
328	#ifdef HAVE_MACH_VM
329	if (vm_deallocate(mach_task_self(), (vm_address_t)addr, size) != KERN_SUCCESS)
330	return -1;
331	#else
332	#ifdef HAVE_MMAP_VM
333	if (munmap((caddr_t)addr, size) != 0)
334	return -1;
335
336	#ifdef USE_33BIT_ADDRESSING
337	shm_range_t *r = find_shm_range(addr, size);
338	if (r) {
339	if (munmap((char *)r->base + (1L << 32), size) != 0)
340	return -1;
341
342	if (shm_unlink(r->file) < 0)
343	return -1;
344	free((char *)r->file);
345
346	if (!remove_shm_range(r))
347	return -1;
348	}
349	#endif
350	#else
351	free(addr);
352	#endif
353	#endif
354
355	return 0;
356	}
357
358	/* Change the memory protection of the region starting at ADDR and
359	extending LEN bytes to PROT. Returns 0 if successful, -1 for errors. */
360
361	int vm_protect(void * addr, size_t size, int prot)
362	{
363	#ifdef HAVE_MACH_VM
364	int ret_code = vm_protect(mach_task_self(), (vm_address_t)addr, size, 0, prot);
365	return ret_code == KERN_SUCCESS ? 0 : -1;
366	#else
367	#ifdef HAVE_MMAP_VM
368	int ret_code = mprotect((caddr_t)addr, size, prot);
369	return ret_code == 0 ? 0 : -1;
370	#else
371	// Unsupported
372	return -1;
373	#endif
374	#endif
375	}
376
377	#ifdef CONFIGURE_TEST_VM_MAP
378	/* Tests covered here:
379	- TEST_VM_PROT_* program slices actually succeeds when a crash occurs
380	- TEST_VM_MAP_ANON* program slices succeeds when it could be compiled
381	*/
382	int main(void)
383	{
384	vm_init();
385
386	#define page_align(address) ((char *)((unsigned long)(address) & -page_size))
387	unsigned long page_size = getpagesize();
388
389	const int area_size = 6 * page_size;
390	volatile char * area = (volatile char *) vm_acquire(area_size);
391	volatile char * fault_address = area + (page_size * 7) / 2;
392
393	#if defined(TEST_VM_MMAP_ANON) \|\| defined(TEST_VM_MMAP_ANONYMOUS)
394	if (area == VM_MAP_FAILED)
395	return 1;
396
397	if (vm_release((char *)area, area_size) < 0)
398	return 1;
399
400	return 0;
401	#endif
402
403	#if defined(TEST_VM_PROT_NONE_READ) \|\| defined(TEST_VM_PROT_NONE_WRITE)
404	if (area == VM_MAP_FAILED)
405	return 0;
406
407	if (vm_protect(page_align(fault_address), page_size, VM_PAGE_NOACCESS) < 0)
408	return 0;
409	#endif
410
411	#if defined(TEST_VM_PROT_RDWR_WRITE)
412	if (area == VM_MAP_FAILED)
413	return 1;
414
415	if (vm_protect(page_align(fault_address), page_size, VM_PAGE_READ) < 0)
416	return 1;
417
418	if (vm_protect(page_align(fault_address), page_size, VM_PAGE_READ \| VM_PAGE_WRITE) < 0)
419	return 1;
420	#endif
421
422	#if defined(TEST_VM_PROT_READ_WRITE)
423	if (vm_protect(page_align(fault_address), page_size, VM_PAGE_READ) < 0)
424	return 0;
425	#endif
426
427	#if defined(TEST_VM_PROT_NONE_READ)
428	// this should cause a core dump
429	char foo = *fault_address;
430	return 0;
431	#endif
432
433	#if defined(TEST_VM_PROT_NONE_WRITE) \|\| defined(TEST_VM_PROT_READ_WRITE)
434	// this should cause a core dump
435	*fault_address = 'z';
436	return 0;
437	#endif
438
439	#if defined(TEST_VM_PROT_RDWR_WRITE)
440	// this should not cause a core dump
441	*fault_address = 'z';
442	return 0;
443	#endif
444	}
445	#endif