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xemu/linux-user/mmap.c
Richard Henderson a5e7ee467c linux-user: Allocate the right amount of space for non-fixed file maps 
If we let the kernel handle the implementation of mmap_find_vma,
via an anon mmap, we must use the size as indicated by the user
and not the size truncated to the filesize.

This happens often in ld.so, where we initially mmap the file to
the size of the text+data+bss to reserve an area, then mmap+fixed
over the top to properly handle data and bss.

Signed-off-by: Richard Henderson <rth@twiddle.net>
2012-08-04 09:37:49 -07:00

789 lines
24 KiB
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
/* 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 HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64
# define TASK_UNMAPPED_BASE (1ul << 38)
#elif defined(__CYGWIN__)
/* Cygwin doesn't have a whole lot of address space. */
# define TASK_UNMAPPED_BASE 0x18000000
#else
# define TASK_UNMAPPED_BASE 0x40000000
#endif
abi_ulong mmap_next_start = TASK_UNMAPPED_BASE;
unsigned long last_brk;
#ifdef CONFIG_USE_GUEST_BASE
/* Subroutine of mmap_find_vma, used when we have pre-allocated a chunk
of guest address space. */
static abi_ulong mmap_find_vma_reserved(abi_ulong start, abi_ulong size)
{
abi_ulong addr;
abi_ulong end_addr;
int prot;
int looped = 0;
if (size > RESERVED_VA) {
return (abi_ulong)-1;
}
size = HOST_PAGE_ALIGN(size);
end_addr = start + size;
if (end_addr > RESERVED_VA) {
end_addr = RESERVED_VA;
}
addr = end_addr - qemu_host_page_size;
while (1) {
if (addr > end_addr) {
if (looped) {
return (abi_ulong)-1;
}
end_addr = RESERVED_VA;
addr = end_addr - qemu_host_page_size;
looped = 1;
continue;
}
prot = page_get_flags(addr);
if (prot) {
end_addr = addr;
}
if (addr + size == end_addr) {
break;
}
addr -= qemu_host_page_size;
}
if (start == mmap_next_start) {
mmap_next_start = addr;
}
return addr;
}
#endif
/*
* 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, *prev;
abi_ulong addr;
int wrapped, repeat;
/* If 'start' == 0, then a default start address is used. */
if (start == 0) {
start = mmap_next_start;
} else {
start &= qemu_host_page_mask;
}
size = HOST_PAGE_ALIGN(size);
#ifdef CONFIG_USE_GUEST_BASE
if (RESERVED_VA) {
return mmap_find_vma_reserved(start, size);
}
#endif
addr = start;
wrapped = repeat = 0;
prev = 0;
for (;; prev = ptr) {
/*
* 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(g2h(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;
}
/* Count the number of sequential returns of the same address.
This is used to modify the search algorithm below. */
repeat = (ptr == prev ? repeat + 1 : 0);
if (h2g_valid(ptr + size - 1)) {
addr = h2g(ptr);
if ((addr & ~TARGET_PAGE_MASK) == 0) {
/* Success. */
if (start == mmap_next_start && addr >= TASK_UNMAPPED_BASE) {
mmap_next_start = addr + size;
}
return addr;
}
/* The address is not properly aligned for the target. */
switch (repeat) {
case 0:
/* Assume the result that the kernel gave us is the
first with enough free space, so start again at the
next higher target page. */
addr = TARGET_PAGE_ALIGN(addr);
break;
case 1:
/* Sometimes the kernel decides to perform the allocation
at the top end of memory instead. */
addr &= TARGET_PAGE_MASK;
break;
case 2:
/* Start over at low memory. */
addr = 0;
break;
default:
/* Fail. This unaligned block must the last. */
addr = -1;
break;
}
} else {
/* Since the result the kernel gave didn't fit, start
again at low memory. If any repetition, fail. */
addr = (repeat ? -1 : 0);
}
/* Unmap and try again. */
munmap(ptr, size);
/* ENOMEM if we checked the whole of the target address space. */
if (addr == (abi_ulong)-1) {
return (abi_ulong)-1;
} else if (addr == 0) {
if (wrapped) {
return (abi_ulong)-1;
}
wrapped = 1;
/* Don't actually use 0 when wrapping, instead indicate
that we'd truly like an allocation in low memory. */
addr = (mmap_min_addr > TARGET_PAGE_SIZE
? TARGET_PAGE_ALIGN(mmap_min_addr)
: TARGET_PAGE_SIZE);
} else if (wrapped && addr >= start) {
return (abi_ulong)-1;
}
}
}
/* 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;
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;
host_offset = offset & qemu_host_page_mask;
/* If the user is asking for the kernel to find a location, do that
before we truncate the length for mapping files below. */
if (!(flags & MAP_FIXED)) {
host_len = len + offset - host_offset;
host_len = HOST_PAGE_ALIGN(host_len);
start = mmap_find_vma(real_start, host_len);
if (start == (abi_ulong)-1) {
errno = ENOMEM;
goto fail;
}
}
/* 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)) {
unsigned long host_start;
void *p;
host_len = len + offset - host_offset;
host_len = HOST_PAGE_ALIGN(host_len);
/* 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(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(start), len, prot,
flags | MAP_FIXED, fd, host_offset);
host_start += offset - host_offset;
}
start = h2g(host_start);
} else {
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;
}
/* 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
tb_invalidate_phys_range(start, start + len, 0);
mmap_unlock();
return start;
fail:
mmap_unlock();
return -1;
}
static void mmap_reserve(abi_ulong start, abi_ulong size)
{
abi_ulong real_start;
abi_ulong real_end;
abi_ulong addr;
abi_ulong end;
int prot;
real_start = start & qemu_host_page_mask;
real_end = HOST_PAGE_ALIGN(start + size);
end = start + size;
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;
}
if (real_start != real_end) {
mmap(g2h(real_start), real_end - real_start, PROT_NONE,
MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE,
-1, 0);
}
}
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) {
if (RESERVED_VA) {
mmap_reserve(real_start, real_end - real_start);
} else {
ret = munmap(g2h(real_start), real_end - real_start);
}
}
if (ret == 0) {
page_set_flags(start, start + len, 0);
tb_invalidate_phys_range(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,
g2h(new_addr));
if (RESERVED_VA && host_addr != MAP_FAILED) {
/* If new and old addresses overlap then the above mremap will
already have failed with EINVAL. */
mmap_reserve(old_addr, old_size);
}
} 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));
if ( RESERVED_VA ) {
mmap_reserve(old_addr, old_size);
}
}
} else {
int prot = 0;
if (RESERVED_VA && old_size < new_size) {
abi_ulong addr;
for (addr = old_addr + old_size;
addr < old_addr + new_size;
addr++) {
prot |= page_get_flags(addr);
}
}
if (prot == 0) {
host_addr = mremap(g2h(old_addr), old_size, new_size, flags);
if (host_addr != MAP_FAILED && RESERVED_VA && old_size > new_size) {
mmap_reserve(old_addr + old_size, new_size - old_size);
}
} else {
errno = ENOMEM;
host_addr = MAP_FAILED;
}
/* 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);
}
tb_invalidate_phys_range(new_addr, new_addr + new_size, 0);
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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