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qemu/linux-user/mmap.c

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/*
* 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, see <http://www.gnu.org/licenses/>.
*/
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <linux/mman.h>
#include <linux/unistd.h>
#include "qemu.h"
#include "qemu-common.h"
//#define DEBUG_MMAP
#if defined(CONFIG_USE_NPTL)
static pthread_mutex_t mmap_mutex = PTHREAD_MUTEX_INITIALIZER;
static __thread int mmap_lock_count;
void mmap_lock(void)
{
if (mmap_lock_count++ == 0) {
pthread_mutex_lock(&mmap_mutex);
}
}
void mmap_unlock(void)
{
if (--mmap_lock_count == 0) {
pthread_mutex_unlock(&mmap_mutex);
}
}
/* Grab lock to make sure things are in a consistent state after fork(). */
void mmap_fork_start(void)
{
if (mmap_lock_count)
abort();
pthread_mutex_lock(&mmap_mutex);
}
void mmap_fork_end(int child)
{
if (child)
pthread_mutex_init(&mmap_mutex, NULL);
else
pthread_mutex_unlock(&mmap_mutex);
}
#else
/* We aren't threadsafe to start with, so no need to worry about locking. */
void mmap_lock(void)
{
}
void mmap_unlock(void)
{
}
#endif
void *qemu_vmalloc(size_t size)
{
void *p;
unsigned long addr;
mmap_lock();
/* Use map and mark the pages as used. */
p = mmap(NULL, size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
addr = (unsigned long)p;
if (addr == (target_ulong) addr) {
/* Allocated region overlaps guest address space.
This may recurse. */
page_set_flags(addr & TARGET_PAGE_MASK, TARGET_PAGE_ALIGN(addr + size),
PAGE_RESERVED);
}
mmap_unlock();
return p;
}
void *qemu_malloc(size_t size)
{
char * p;
size += 16;
p = qemu_vmalloc(size);
*(size_t *)p = size;
return p + 16;
}
/* We use map, which is always zero initialized. */
void * qemu_mallocz(size_t size)
{
return qemu_malloc(size);
}
void qemu_free(void *ptr)
{
/* FIXME: We should unmark the reserved pages here. However this gets
complicated when one target page spans multiple host pages, so we
don't bother. */
size_t *p;
p = (size_t *)((char *)ptr - 16);
munmap(p, *p);
}
void *qemu_realloc(void *ptr, size_t size)
{
size_t old_size, copy;
void *new_ptr;
if (!ptr)
return qemu_malloc(size);
old_size = *(size_t *)((char *)ptr - 16);
copy = old_size < size ? old_size : size;
new_ptr = qemu_malloc(size);
memcpy(new_ptr, ptr, copy);
qemu_free(ptr);
return new_ptr;
}
/* NOTE: all the constants are the HOST ones, but addresses are target. */
int target_mprotect(abi_ulong start, abi_ulong len, int prot)
{
abi_ulong end, host_start, host_end, addr;
int prot1, ret;
#ifdef DEBUG_MMAP
printf("mprotect: start=0x" TARGET_ABI_FMT_lx
"len=0x" TARGET_ABI_FMT_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;
prot &= PROT_READ | PROT_WRITE | PROT_EXEC;
if (len == 0)
return 0;
mmap_lock();
host_start = start & qemu_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);
}
if (host_end == host_start + qemu_host_page_size) {
for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
prot1 |= page_get_flags(addr);
}
end = host_end;
}
ret = mprotect(g2h(host_start), qemu_host_page_size, prot1 & PAGE_BITS);
if (ret != 0)
goto error;
host_start += qemu_host_page_size;
}
if (end < host_end) {
prot1 = prot;
for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
prot1 |= page_get_flags(addr);
}
ret = mprotect(g2h(host_end - qemu_host_page_size), qemu_host_page_size,
prot1 & PAGE_BITS);
if (ret != 0)
goto error;
host_end -= qemu_host_page_size;
}
/* handle the pages in the middle */
if (host_start < host_end) {
ret = mprotect(g2h(host_start), host_end - host_start, prot);
if (ret != 0)
goto error;
}
page_set_flags(start, start + len, prot | PAGE_VALID);
mmap_unlock();
return 0;
error:
mmap_unlock();
return ret;
}
/* map an incomplete host page */
static int mmap_frag(abi_ulong real_start,
abi_ulong start, abi_ulong end,
int prot, int flags, int fd, abi_ulong offset)
{
abi_ulong real_end, addr;
void *host_start;
int prot1, prot_new;
real_end = real_start + qemu_host_page_size;
host_start = g2h(real_start);
/* get the protection of the target pages outside the mapping */
prot1 = 0;
for(addr = real_start; addr < real_end; addr++) {
if (addr < start || addr >= end)
prot1 |= page_get_flags(addr);
}
if (prot1 == 0) {
/* no page was there, so we allocate one */
void *p = mmap(host_start, qemu_host_page_size, prot,
flags | MAP_ANONYMOUS, -1, 0);
if (p == MAP_FAILED)
return -1;
prot1 = prot;
}
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 -1;
/* adjust protection to be able to read */
if (!(prot1 & PROT_WRITE))
mprotect(host_start, qemu_host_page_size, prot1 | PROT_WRITE);
/* read the corresponding file data */
if (pread(fd, g2h(start), end - start, offset) == -1)
return -1;
/* put final protection */
if (prot_new != (prot1 | PROT_WRITE))
mprotect(host_start, qemu_host_page_size, prot_new);
} else {
/* just update the protection */
if (prot_new != prot1) {
mprotect(host_start, qemu_host_page_size, prot_new);
}
}
return 0;
}
#if defined(__CYGWIN__)
/* Cygwin doesn't have a whole lot of address space. */
static abi_ulong mmap_next_start = 0x18000000;
#else
static abi_ulong mmap_next_start = 0x40000000;
#endif
unsigned long last_brk;
/*
* Find and reserve a free memory area of size 'size'. The search
* starts at 'start'.
* It must be called with mmap_lock() held.
* Return -1 if error.
*/
abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
{
void *ptr;
abi_ulong addr;
size = HOST_PAGE_ALIGN(size);
start &= qemu_host_page_mask;
/* If 'start' == 0, then a default start address is used. */
if (start == 0)
start = mmap_next_start;
addr = start;
for(;;) {
/*
* Reserve needed memory area to avoid a race.
* It should be discarded using:
* - mmap() with MAP_FIXED flag
* - mremap() with MREMAP_FIXED flag
* - shmat() with SHM_REMAP flag
*/
ptr = mmap((void *)(unsigned long)addr, size, PROT_NONE,
MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE, -1, 0);
/* ENOMEM, if host address space has no memory */
if (ptr == MAP_FAILED)
return (abi_ulong)-1;
/* If address fits target address space we've found what we need */
if ((unsigned long)ptr + size - 1 <= (abi_ulong)-1)
break;
/* Unmap and try again with new page */
munmap(ptr, size);
addr += qemu_host_page_size;
/* ENOMEM if we check whole of target address space */
if (addr == start)
return (abi_ulong)-1;
}
/* Update default start address */
if (start == mmap_next_start)
mmap_next_start = (unsigned long)ptr + size;
return h2g(ptr);
}
/* NOTE: all the constants are the HOST ones */
abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
int flags, int fd, abi_ulong offset)
{
abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
unsigned long host_start;
mmap_lock();
#ifdef DEBUG_MMAP
{
printf("mmap: start=0x" TARGET_ABI_FMT_lx
" len=0x" TARGET_ABI_FMT_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=" TARGET_ABI_FMT_lx "\n", fd, offset);
}
#endif
if (offset & ~TARGET_PAGE_MASK) {
errno = EINVAL;
goto fail;
}
len = TARGET_PAGE_ALIGN(len);
if (len == 0)
goto the_end;
real_start = start & qemu_host_page_mask;
/* When mapping files into a memory area larger than the file, accesses
to pages beyond the file size will cause a SIGBUS.
For example, if mmaping a file of 100 bytes on a host with 4K pages
emulating a target with 8K pages, the target expects to be able to
access the first 8K. But the host will trap us on any access beyond
4K.
When emulating a target with a larger page-size than the hosts, we
may need to truncate file maps at EOF and add extra anonymous pages
up to the targets page boundary. */
if ((qemu_real_host_page_size < TARGET_PAGE_SIZE)
&& !(flags & MAP_ANONYMOUS)) {
struct stat sb;
if (fstat (fd, &sb) == -1)
goto fail;
/* Are we trying to create a map beyond EOF?. */
if (offset + len > sb.st_size) {
/* If so, truncate the file map at eof aligned with
the hosts real pagesize. Additional anonymous maps
will be created beyond EOF. */
len = (sb.st_size - offset);
len += qemu_real_host_page_size - 1;
len &= ~(qemu_real_host_page_size - 1);
}
}
if (!(flags & MAP_FIXED)) {
abi_ulong mmap_start;
void *p;
host_offset = offset & qemu_host_page_mask;
host_len = len + offset - host_offset;
host_len = HOST_PAGE_ALIGN(host_len);
mmap_start = mmap_find_vma(real_start, host_len);
if (mmap_start == (abi_ulong)-1) {
errno = ENOMEM;
goto fail;
}
/* Note: we prefer to control the mapping address. It is
especially important if qemu_host_page_size >
qemu_real_host_page_size */
p = mmap(g2h(mmap_start),
host_len, prot, flags | MAP_FIXED | MAP_ANONYMOUS, -1, 0);
if (p == MAP_FAILED)
goto fail;
/* update start so that it points to the file position at 'offset' */
host_start = (unsigned long)p;
if (!(flags & MAP_ANONYMOUS)) {
p = mmap(g2h(mmap_start), len, prot,
flags | MAP_FIXED, fd, host_offset);
host_start += offset - host_offset;
}
start = h2g(host_start);
} else {
int flg;
target_ulong addr;
if (start & ~TARGET_PAGE_MASK) {
errno = EINVAL;
goto fail;
}
end = start + len;
real_end = HOST_PAGE_ALIGN(end);
/*
* Test if requested memory area fits target address space
* It can fail only on 64-bit host with 32-bit target.
* On any other target/host host mmap() handles this error correctly.
*/
if ((unsigned long)start + len - 1 > (abi_ulong) -1) {
errno = EINVAL;
goto fail;
}
for(addr = real_start; addr < real_end; addr += TARGET_PAGE_SIZE) {
flg = page_get_flags(addr);
if (flg & PAGE_RESERVED) {
errno = ENXIO;
goto fail;
}
}
/* worst case: we cannot map the file because the offset is not
aligned, so we read it */
if (!(flags & MAP_ANONYMOUS) &&
(offset & ~qemu_host_page_mask) != (start & ~qemu_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)) {
errno = EINVAL;
goto fail;
}
retaddr = target_mmap(start, len, prot | PROT_WRITE,
MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
-1, 0);
if (retaddr == -1)
goto fail;
if (pread(fd, g2h(start), len, offset) == -1)
goto fail;
if (!(prot & PROT_WRITE)) {
ret = target_mprotect(start, len, prot);
if (ret != 0) {
start = ret;
goto the_end;
}
}
goto the_end;
}
/* handle the start of the mapping */
if (start > real_start) {
if (real_end == real_start + qemu_host_page_size) {
/* one single host page */
ret = mmap_frag(real_start, start, end,
prot, flags, fd, offset);
if (ret == -1)
goto fail;
goto the_end1;
}
ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,
prot, flags, fd, offset);
if (ret == -1)
goto fail;
real_start += qemu_host_page_size;
}
/* handle the end of the mapping */
if (end < real_end) {
ret = mmap_frag(real_end - qemu_host_page_size,
real_end - qemu_host_page_size, real_end,
prot, flags, fd,
offset + real_end - qemu_host_page_size - start);
if (ret == -1)
goto fail;
real_end -= qemu_host_page_size;
}
/* map the middle (easier) */
if (real_start < real_end) {
void *p;
unsigned long offset1;
if (flags & MAP_ANONYMOUS)
offset1 = 0;
else
offset1 = offset + real_start - start;
p = mmap(g2h(real_start), real_end - real_start,
prot, flags, fd, offset1);
if (p == MAP_FAILED)
goto fail;
}
}
the_end1:
page_set_flags(start, start + len, prot | PAGE_VALID);
the_end:
#ifdef DEBUG_MMAP
printf("ret=0x" TARGET_ABI_FMT_lx "\n", start);
page_dump(stdout);
printf("\n");
#endif
mmap_unlock();
return start;
fail:
mmap_unlock();
return -1;
}
int target_munmap(abi_ulong start, abi_ulong len)
{
abi_ulong end, real_start, real_end, addr;
int prot, ret;
#ifdef DEBUG_MMAP
printf("munmap: start=0x" TARGET_ABI_FMT_lx " len=0x"
TARGET_ABI_FMT_lx "\n",
start, len);
#endif
if (start & ~TARGET_PAGE_MASK)
return -EINVAL;
len = TARGET_PAGE_ALIGN(len);
if (len == 0)
return -EINVAL;
mmap_lock();
end = start + len;
real_start = start & qemu_host_page_mask;
real_end = HOST_PAGE_ALIGN(end);
if (start > real_start) {
/* handle host page containing start */
prot = 0;
for(addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
prot |= page_get_flags(addr);
}
if (real_end == real_start + qemu_host_page_size) {
for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
prot |= page_get_flags(addr);
}
end = real_end;
}
if (prot != 0)
real_start += qemu_host_page_size;
}
if (end < real_end) {
prot = 0;
for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
prot |= page_get_flags(addr);
}
if (prot != 0)
real_end -= qemu_host_page_size;
}
ret = 0;
/* unmap what we can */
if (real_start < real_end) {
ret = munmap(g2h(real_start), real_end - real_start);
}
if (ret == 0)
page_set_flags(start, start + len, 0);
mmap_unlock();
return ret;
}
abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
abi_ulong new_size, unsigned long flags,
abi_ulong new_addr)
{
int prot;
void *host_addr;
mmap_lock();
if (flags & MREMAP_FIXED)
host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
old_size, new_size,
flags,
new_addr);
else if (flags & MREMAP_MAYMOVE) {
abi_ulong mmap_start;
mmap_start = mmap_find_vma(0, new_size);
if (mmap_start == -1) {
errno = ENOMEM;
host_addr = MAP_FAILED;
} else
host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
old_size, new_size,
flags | MREMAP_FIXED,
g2h(mmap_start));
} else {
host_addr = mremap(g2h(old_addr), old_size, new_size, flags);
/* Check if address fits target address space */
if ((unsigned long)host_addr + new_size > (abi_ulong)-1) {
/* Revert mremap() changes */
host_addr = mremap(g2h(old_addr), new_size, old_size, flags);
errno = ENOMEM;
host_addr = MAP_FAILED;
}
}
if (host_addr == MAP_FAILED) {
new_addr = -1;
} else {
new_addr = h2g(host_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);
}
mmap_unlock();
return new_addr;
}
int target_msync(abi_ulong start, abi_ulong len, int flags)
{
abi_ulong end;
if (start & ~TARGET_PAGE_MASK)
return -EINVAL;
len = TARGET_PAGE_ALIGN(len);
end = start + len;
if (end < start)
return -EINVAL;
if (end == start)
return 0;
start &= qemu_host_page_mask;
return msync(g2h(start), end - start, flags);
}
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