[mirror_qemu.git] / linux-user / mmap.c

/*
 *  mmap support for qemu
 * 
 *  Copyright (c) 2003 Fabrice Bellard
 *
 *  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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/mman.h>

#include "qemu.h"

//#define DEBUG_MMAP

/* NOTE: all the constants are the HOST ones */
int target_mprotect(unsigned long start, unsigned long len, int prot)
{
    unsigned long end, host_start, host_end, addr;
    int prot1, ret;

#ifdef DEBUG_MMAP
    printf("mprotect: start=0x%lx len=0x%lx prot=%c%c%c\n", start, len,
           prot & PROT_READ ? 'r' : '-',
           prot & PROT_WRITE ? 'w' : '-',
           prot & PROT_EXEC ? 'x' : '-');
#endif

    if ((start & ~TARGET_PAGE_MASK) != 0)
        return -EINVAL;
    len = TARGET_PAGE_ALIGN(len);
    end = start + len;
    if (end < start)
        return -EINVAL;
    if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC))
        return -EINVAL;
    if (len == 0)
        return 0;
    
    host_start = start & host_page_mask;
    host_end = HOST_PAGE_ALIGN(end);
    if (start > host_start) {
        /* handle host page containing start */
        prot1 = prot;
        for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
            prot1 |= page_get_flags(addr);
        }
        ret = mprotect((void *)host_start, host_page_size, prot1 & PAGE_BITS);
        if (ret != 0)
            return ret;
        host_start += host_page_size;
    }
    if (end < host_end) {
        /* handle host page containing end (can be the same as first page) */
        prot1 = prot;
        for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
            prot1 |= page_get_flags(addr);
        }
        ret = mprotect((void *)(host_end - host_page_size), host_page_size, 
                       prot1 & PAGE_BITS);
        if (ret != 0)
            return ret;
        host_end -= host_page_size;
    }
    
    /* handle the pages in the middle */
    if (host_start < host_end) {
        ret = mprotect((void *)host_start, host_end - host_start, prot);
        if (ret != 0)
            return ret;
    }

    page_set_flags(start, start + len, prot | PAGE_VALID);
    return 0;
}

/* map an incomplete host page */
int mmap_frag(unsigned long host_start, 
               unsigned long start, unsigned long end, 
               int prot, int flags, int fd, unsigned long offset)
{
    unsigned long host_end, ret, addr;
    int prot1, prot_new;

    host_end = host_start + host_page_size;

    /* get the protection of the target pages outside the mapping */
    prot1 = 0;
    for(addr = host_start; addr < host_end; addr++) {
        if (addr < start || addr >= end)
            prot1 |= page_get_flags(addr);
    }
    
    if (prot1 == 0) {
        /* no page was there, so we allocate one */
        ret = (long)mmap((void *)host_start, host_page_size, prot, 
                         flags | MAP_ANONYMOUS, -1, 0);
        if (ret == -1)
            return ret;
    }
    prot1 &= PAGE_BITS;

    prot_new = prot | prot1;
    if (!(flags & MAP_ANONYMOUS)) {
        /* msync() won't work here, so we return an error if write is
           possible while it is a shared mapping */
        if ((flags & MAP_TYPE) == MAP_SHARED &&
            (prot & PROT_WRITE))
            return -EINVAL;

        /* adjust protection to be able to read */
        if (!(prot1 & PROT_WRITE))
            mprotect((void *)host_start, host_page_size, prot1 | PROT_WRITE);
        
        /* read the corresponding file data */
        pread(fd, (void *)start, end - start, offset);
        
        /* put final protection */
        if (prot_new != (prot1 | PROT_WRITE))
            mprotect((void *)host_start, host_page_size, prot_new);
    } else {
        /* just update the protection */
        if (prot_new != prot1) {
            mprotect((void *)host_start, host_page_size, prot_new);
        }
    }
    return 0;
}

/* NOTE: all the constants are the HOST ones */
long target_mmap(unsigned long start, unsigned long len, int prot, 
                 int flags, int fd, unsigned long offset)
{
    unsigned long ret, end, host_start, host_end, retaddr, host_offset, host_len;

#ifdef DEBUG_MMAP
    {
        printf("mmap: start=0x%lx len=0x%lx prot=%c%c%c flags=",
               start, len, 
               prot & PROT_READ ? 'r' : '-',
               prot & PROT_WRITE ? 'w' : '-',
               prot & PROT_EXEC ? 'x' : '-');
        if (flags & MAP_FIXED)
            printf("MAP_FIXED ");
        if (flags & MAP_ANONYMOUS)
            printf("MAP_ANON ");
        switch(flags & MAP_TYPE) {
        case MAP_PRIVATE:
            printf("MAP_PRIVATE ");
            break;
        case MAP_SHARED:
            printf("MAP_SHARED ");
            break;
        default:
            printf("[MAP_TYPE=0x%x] ", flags & MAP_TYPE);
            break;
        }
        printf("fd=%d offset=%lx\n", fd, offset);
    }
#endif

    if (offset & ~TARGET_PAGE_MASK)
        return -EINVAL;

    len = TARGET_PAGE_ALIGN(len);
    if (len == 0)
        return start;
    host_start = start & host_page_mask;

    if (!(flags & MAP_FIXED)) {
        if (host_page_size != real_host_page_size) {
            /* NOTE: this code is only for debugging with '-p' option */
            /* reserve a memory area */
            host_len = HOST_PAGE_ALIGN(len) + host_page_size - TARGET_PAGE_SIZE;
            host_start = (long)mmap((void *)host_start, host_len, PROT_NONE, 
                                    MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
            if (host_start == -1)
                return host_start;
            host_end = host_start + host_len;
            start = HOST_PAGE_ALIGN(host_start);
            end = start + HOST_PAGE_ALIGN(len);
            if (start > host_start)
                munmap((void *)host_start, start - host_start);
            if (end < host_end)
                munmap((void *)end, host_end - end);
            /* use it as a fixed mapping */
            flags |= MAP_FIXED;
        } else {
            /* if not fixed, no need to do anything */
            host_offset = offset & host_page_mask;
            host_len = len + offset - host_offset;
            start = (long)mmap((void *)host_start, host_len, 
                               prot, flags, fd, host_offset);
            if (start == -1)
                return start;
            /* update start so that it points to the file position at 'offset' */
            if (!(flags & MAP_ANONYMOUS)) 
                start += offset - host_offset;
            goto the_end1;
        }
    }
    
    if (start & ~TARGET_PAGE_MASK)
        return -EINVAL;
    end = start + len;
    host_end = HOST_PAGE_ALIGN(end);

    /* worst case: we cannot map the file because the offset is not
       aligned, so we read it */
    if (!(flags & MAP_ANONYMOUS) &&
        (offset & ~host_page_mask) != (start & ~host_page_mask)) {
        /* msync() won't work here, so we return an error if write is
           possible while it is a shared mapping */
        if ((flags & MAP_TYPE) == MAP_SHARED &&
            (prot & PROT_WRITE))
            return -EINVAL;
        retaddr = target_mmap(start, len, prot | PROT_WRITE, 
                              MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, 
                              -1, 0);
        if (retaddr == -1)
            return retaddr;
        pread(fd, (void *)start, len, offset);
        if (!(prot & PROT_WRITE)) {
            ret = target_mprotect(start, len, prot);
            if (ret != 0)
                return ret;
        }
        goto the_end;
    }

    /* handle the start of the mapping */
    if (start > host_start) {
        if (host_end == host_start + host_page_size) {
            /* one single host page */
            ret = mmap_frag(host_start, start, end,
                            prot, flags, fd, offset);
            if (ret == -1)
                return ret;
            goto the_end1;
        }
        ret = mmap_frag(host_start, start, host_start + host_page_size,
                        prot, flags, fd, offset);
        if (ret == -1)
            return ret;
        host_start += host_page_size;
    }
    /* handle the end of the mapping */
    if (end < host_end) {
        ret = mmap_frag(host_end - host_page_size, 
                        host_end - host_page_size, host_end,
                        prot, flags, fd, 
                        offset + host_end - host_page_size - start);
        if (ret == -1)
            return ret;
        host_end -= host_page_size;
    }
    
    /* map the middle (easier) */
    if (host_start < host_end) {
        ret = (long)mmap((void *)host_start, host_end - host_start, 
                         prot, flags, fd, offset + host_start - start);
        if (ret == -1)
            return ret;
    }
 the_end1:
    page_set_flags(start, start + len, prot | PAGE_VALID);
 the_end:
#ifdef DEBUG_MMAP
    page_dump(stdout);
    printf("\n");
#endif
    return start;
}

int target_munmap(unsigned long start, unsigned long len)
{
    unsigned long end, host_start, host_end, addr;
    int prot, ret;

#ifdef DEBUG_MMAP
    printf("munmap: start=0x%lx len=0x%lx\n", start, len);
#endif
    if (start & ~TARGET_PAGE_MASK)
        return -EINVAL;
    len = TARGET_PAGE_ALIGN(len);
    if (len == 0)
        return -EINVAL;
    end = start + len;
    host_start = start & host_page_mask;
    host_end = HOST_PAGE_ALIGN(end);

    if (start > host_start) {
        /* handle host page containing start */
        prot = 0;
        for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
            prot |= page_get_flags(addr);
        }
        if (prot != 0)
            host_start += host_page_size;
    }
    if (end < host_end) {
        /* handle host page containing end (can be the same as first page) */
        prot = 0;
        for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
            prot |= page_get_flags(addr);
        }
        if (prot != 0)
            host_end -= host_page_size;
    }
    
    /* unmap what we can */
    if (host_start < host_end) {
        ret = munmap((void *)host_start, host_end - host_start);
        if (ret != 0)
            return ret;
    }

    page_set_flags(start, start + len, 0);
    return 0;
}

/* XXX: currently, we only handle MAP_ANONYMOUS and not MAP_FIXED
   blocks which have been allocated starting on a host page */
long target_mremap(unsigned long old_addr, unsigned long old_size, 
                   unsigned long new_size, unsigned long flags,
                   unsigned long new_addr)
{
    int prot;

    /* XXX: use 5 args syscall */
    new_addr = (long)mremap((void *)old_addr, old_size, new_size, flags);
    if (new_addr == -1)
        return new_addr;
    prot = page_get_flags(old_addr);
    page_set_flags(old_addr, old_addr + old_size, 0);
    page_set_flags(new_addr, new_addr + new_size, prot | PAGE_VALID);
    return new_addr;
}

int target_msync(unsigned long start, unsigned long len, int flags)
{
    unsigned long end;

    if (start & ~TARGET_PAGE_MASK)
        return -EINVAL;
    len = TARGET_PAGE_ALIGN(len);
    if (len == 0)
        return 0;
    end = start + len;
    
    start &= host_page_mask;
    return msync((void *)start, len, flags);
}
Commit	Line	Data
54936004 FB	1	/*
	2	* mmap support for qemu
	3	*
	4	* Copyright (c) 2003 Fabrice Bellard
	5	*
	6	* This program is free software; you can redistribute it and/or modify
	7	* it under the terms of the GNU General Public License as published by
	8	* the Free Software Foundation; either version 2 of the License, or
	9	* (at your option) any later version.
	10	*
	11	* This program is distributed in the hope that it will be useful,
	12	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	14	* GNU General Public License for more details.
	15	*
	16	* You should have received a copy of the GNU General Public License
	17	* along with this program; if not, write to the Free Software
	18	* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
	19	*/
	20	#include <stdlib.h>
	21	#include <stdio.h>
	22	#include <stdarg.h>
	23	#include <string.h>
	24	#include <unistd.h>
	25	#include <errno.h>
	26	#include <sys/mman.h>
	27
	28	#include "qemu.h"
	29
	30	//#define DEBUG_MMAP
	31
	32	/* NOTE: all the constants are the HOST ones */
	33	int target_mprotect(unsigned long start, unsigned long len, int prot)
	34	{
	35	unsigned long end, host_start, host_end, addr;
	36	int prot1, ret;
	37
	38	#ifdef DEBUG_MMAP
	39	printf("mprotect: start=0x%lx len=0x%lx prot=%c%c%c\n", start, len,
	40	prot & PROT_READ ? 'r' : '-',
	41	prot & PROT_WRITE ? 'w' : '-',
	42	prot & PROT_EXEC ? 'x' : '-');
	43	#endif
	44
	45	if ((start & ~TARGET_PAGE_MASK) != 0)
	46	return -EINVAL;
	47	len = TARGET_PAGE_ALIGN(len);
	48	end = start + len;
	49	if (end < start)
	50	return -EINVAL;
	51	if (prot & ~(PROT_READ \| PROT_WRITE \| PROT_EXEC))
	52	return -EINVAL;
	53	if (len == 0)
	54	return 0;
	55
	56	host_start = start & host_page_mask;
	57	host_end = HOST_PAGE_ALIGN(end);
	58	if (start > host_start) {
	59	/* handle host page containing start */
	60	prot1 = prot;
	61	for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
	62	prot1 \|= page_get_flags(addr);
	63	}
	64	ret = mprotect((void *)host_start, host_page_size, prot1 & PAGE_BITS);
65	if (ret != 0)
66	return ret;
67	host_start += host_page_size;
68	}
69	if (end < host_end) {
70	/* handle host page containing end (can be the same as first page) */
71	prot1 = prot;
72	for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
73	prot1 \|= page_get_flags(addr);
74	}
75	ret = mprotect((void *)(host_end - host_page_size), host_page_size,
76	prot1 & PAGE_BITS);
77	if (ret != 0)
78	return ret;
79	host_end -= host_page_size;
80	}
81
82	/* handle the pages in the middle */
83	if (host_start < host_end) {
84	ret = mprotect((void *)host_start, host_end - host_start, prot);
85	if (ret != 0)
86	return ret;
87	}
88
89	page_set_flags(start, start + len, prot \| PAGE_VALID);
90	return 0;
91	}
92
93	/* map an incomplete host page */
94	int mmap_frag(unsigned long host_start,
95	unsigned long start, unsigned long end,
96	int prot, int flags, int fd, unsigned long offset)
97	{
98	unsigned long host_end, ret, addr;
99	int prot1, prot_new;
100
101	host_end = host_start + host_page_size;
102
103	/* get the protection of the target pages outside the mapping */
104	prot1 = 0;
105	for(addr = host_start; addr < host_end; addr++) {
106	if (addr < start \|\| addr >= end)
107	prot1 \|= page_get_flags(addr);
108	}
109
110	if (prot1 == 0) {
111	/* no page was there, so we allocate one */
112	ret = (long)mmap((void *)host_start, host_page_size, prot,
113	flags \| MAP_ANONYMOUS, -1, 0);
114	if (ret == -1)
115	return ret;
116	}
117	prot1 &= PAGE_BITS;
118
119	prot_new = prot \| prot1;
120	if (!(flags & MAP_ANONYMOUS)) {
121	/* msync() won't work here, so we return an error if write is
122	possible while it is a shared mapping */
123	if ((flags & MAP_TYPE) == MAP_SHARED &&
124	(prot & PROT_WRITE))
125	return -EINVAL;
126
127	/* adjust protection to be able to read */
128	if (!(prot1 & PROT_WRITE))
129	mprotect((void *)host_start, host_page_size, prot1 \| PROT_WRITE);
130
131	/* read the corresponding file data */
132	pread(fd, (void *)start, end - start, offset);
133
134	/* put final protection */
135	if (prot_new != (prot1 \| PROT_WRITE))
136	mprotect((void *)host_start, host_page_size, prot_new);
137	} else {
138	/* just update the protection */
139	if (prot_new != prot1) {
140	mprotect((void *)host_start, host_page_size, prot_new);
141	}
142	}
143	return 0;
144	}
145
146	/* NOTE: all the constants are the HOST ones */
147	long target_mmap(unsigned long start, unsigned long len, int prot,
148	int flags, int fd, unsigned long offset)
149	{
150	unsigned long ret, end, host_start, host_end, retaddr, host_offset, host_len;
151
152	#ifdef DEBUG_MMAP
153	{
154	printf("mmap: start=0x%lx len=0x%lx prot=%c%c%c flags=",
155	start, len,
156	prot & PROT_READ ? 'r' : '-',
157	prot & PROT_WRITE ? 'w' : '-',
158	prot & PROT_EXEC ? 'x' : '-');
159	if (flags & MAP_FIXED)
160	printf("MAP_FIXED ");
161	if (flags & MAP_ANONYMOUS)
162	printf("MAP_ANON ");
163	switch(flags & MAP_TYPE) {
164	case MAP_PRIVATE:
165	printf("MAP_PRIVATE ");
166	break;
167	case MAP_SHARED:
168	printf("MAP_SHARED ");
169	break;
170	default:
171	printf("[MAP_TYPE=0x%x] ", flags & MAP_TYPE);
172	break;
173	}
174	printf("fd=%d offset=%lx\n", fd, offset);
175	}
176	#endif
177
178	if (offset & ~TARGET_PAGE_MASK)
179	return -EINVAL;
180
181	len = TARGET_PAGE_ALIGN(len);
182	if (len == 0)
183	return start;
184	host_start = start & host_page_mask;
185
186	if (!(flags & MAP_FIXED)) {
187	if (host_page_size != real_host_page_size) {
188	/* NOTE: this code is only for debugging with '-p' option */
189	/* reserve a memory area */
190	host_len = HOST_PAGE_ALIGN(len) + host_page_size - TARGET_PAGE_SIZE;
191	host_start = (long)mmap((void *)host_start, host_len, PROT_NONE,
192	MAP_PRIVATE \| MAP_ANONYMOUS, -1, 0);
193	if (host_start == -1)
194	return host_start;
195	host_end = host_start + host_len;
196	start = HOST_PAGE_ALIGN(host_start);
197	end = start + HOST_PAGE_ALIGN(len);
198	if (start > host_start)
199	munmap((void *)host_start, start - host_start);
200	if (end < host_end)
201	munmap((void *)end, host_end - end);
202	/* use it as a fixed mapping */
203	flags \|= MAP_FIXED;
204	} else {
205	/* if not fixed, no need to do anything */
206	host_offset = offset & host_page_mask;
207	host_len = len + offset - host_offset;
208	start = (long)mmap((void *)host_start, host_len,
209	prot, flags, fd, host_offset);
210	if (start == -1)
211	return start;
212	/* update start so that it points to the file position at 'offset' */
213	if (!(flags & MAP_ANONYMOUS))
214	start += offset - host_offset;
215	goto the_end1;
216	}
217	}
218
219	if (start & ~TARGET_PAGE_MASK)
220	return -EINVAL;
221	end = start + len;
222	host_end = HOST_PAGE_ALIGN(end);
223
224	/* worst case: we cannot map the file because the offset is not
225	aligned, so we read it */
226	if (!(flags & MAP_ANONYMOUS) &&
227	(offset & ~host_page_mask) != (start & ~host_page_mask)) {
228	/* msync() won't work here, so we return an error if write is
229	possible while it is a shared mapping */
230	if ((flags & MAP_TYPE) == MAP_SHARED &&
231	(prot & PROT_WRITE))
232	return -EINVAL;
233	retaddr = target_mmap(start, len, prot \| PROT_WRITE,
234	MAP_FIXED \| MAP_PRIVATE \| MAP_ANONYMOUS,
235	-1, 0);
236	if (retaddr == -1)
237	return retaddr;
238	pread(fd, (void *)start, len, offset);
239	if (!(prot & PROT_WRITE)) {
240	ret = target_mprotect(start, len, prot);
241	if (ret != 0)
242	return ret;
243	}
244	goto the_end;
245	}
246
247	/* handle the start of the mapping */
248	if (start > host_start) {
249	if (host_end == host_start + host_page_size) {
250	/* one single host page */
251	ret = mmap_frag(host_start, start, end,
252	prot, flags, fd, offset);
253	if (ret == -1)
254	return ret;
255	goto the_end1;
256	}
257	ret = mmap_frag(host_start, start, host_start + host_page_size,
258	prot, flags, fd, offset);
259	if (ret == -1)
260	return ret;
261	host_start += host_page_size;
262	}
263	/* handle the end of the mapping */
264	if (end < host_end) {
265	ret = mmap_frag(host_end - host_page_size,
266	host_end - host_page_size, host_end,
267	prot, flags, fd,
268	offset + host_end - host_page_size - start);
269	if (ret == -1)
270	return ret;
271	host_end -= host_page_size;
272	}
273
274	/* map the middle (easier) */
275	if (host_start < host_end) {
276	ret = (long)mmap((void *)host_start, host_end - host_start,
277	prot, flags, fd, offset + host_start - start);
278	if (ret == -1)
279	return ret;
280	}
281	the_end1:
282	page_set_flags(start, start + len, prot \| PAGE_VALID);
283	the_end:
284	#ifdef DEBUG_MMAP
285	page_dump(stdout);
286	printf("\n");
287	#endif
288	return start;
289	}
290
291	int target_munmap(unsigned long start, unsigned long len)
292	{
293	unsigned long end, host_start, host_end, addr;
294	int prot, ret;
295
296	#ifdef DEBUG_MMAP
297	printf("munmap: start=0x%lx len=0x%lx\n", start, len);
298	#endif
299	if (start & ~TARGET_PAGE_MASK)
300	return -EINVAL;
301	len = TARGET_PAGE_ALIGN(len);
302	if (len == 0)
303	return -EINVAL;
304	end = start + len;
305	host_start = start & host_page_mask;
306	host_end = HOST_PAGE_ALIGN(end);
307
308	if (start > host_start) {
309	/* handle host page containing start */
310	prot = 0;
311	for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
312	prot \|= page_get_flags(addr);
313	}
314	if (prot != 0)
315	host_start += host_page_size;
316	}
317	if (end < host_end) {
318	/* handle host page containing end (can be the same as first page) */
319	prot = 0;
320	for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
321	prot \|= page_get_flags(addr);
322	}
323	if (prot != 0)
324	host_end -= host_page_size;
325	}
326
327	/* unmap what we can */
328	if (host_start < host_end) {
329	ret = munmap((void *)host_start, host_end - host_start);
330	if (ret != 0)
331	return ret;
332	}
333
334	page_set_flags(start, start + len, 0);
335	return 0;
336	}
337
338	/* XXX: currently, we only handle MAP_ANONYMOUS and not MAP_FIXED
339	blocks which have been allocated starting on a host page */
340	long target_mremap(unsigned long old_addr, unsigned long old_size,
341	unsigned long new_size, unsigned long flags,
342	unsigned long new_addr)
343	{
344	int prot;
345
346	/* XXX: use 5 args syscall */
347	new_addr = (long)mremap((void *)old_addr, old_size, new_size, flags);
348	if (new_addr == -1)
349	return new_addr;
350	prot = page_get_flags(old_addr);
351	page_set_flags(old_addr, old_addr + old_size, 0);
352	page_set_flags(new_addr, new_addr + new_size, prot \| PAGE_VALID);
353	return new_addr;
354	}
355
356	int target_msync(unsigned long start, unsigned long len, int flags)
357	{
358	unsigned long end;
359
360	if (start & ~TARGET_PAGE_MASK)
361	return -EINVAL;
362	len = TARGET_PAGE_ALIGN(len);
363	if (len == 0)
364	return 0;
365	end = start + len;
366
367	start &= host_page_mask;
368	return msync((void *)start, len, flags);
369	}
370