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qemu/linux-user/mmap.c
Richard Henderson 78bc8ed9a8 linux-user: Rewrite target_shmat 
Handle combined host and guest alignment requirements.
Handle host and guest page size differences.
Handle SHM_EXEC.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/115
Tested-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2024-03-01 08:09:55 -10:00

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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 "qemu/osdep.h"
#include <sys/shm.h>
#include "trace.h"
#include "exec/log.h"
#include "qemu.h"
#include "user-internals.h"
#include "user-mmap.h"
#include "target_mman.h"
#include "qemu/interval-tree.h"
#ifdef TARGET_ARM
#include "target/arm/cpu-features.h"
#endif
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)
{
assert(mmap_lock_count > 0);
if (--mmap_lock_count == 0) {
pthread_mutex_unlock(&mmap_mutex);
}
}
bool have_mmap_lock(void)
{
return mmap_lock_count > 0 ? true : false;
}
/* 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);
}
}
/* Protected by mmap_lock. */
static IntervalTreeRoot shm_regions;
static void shm_region_add(abi_ptr start, abi_ptr last)
{
IntervalTreeNode *i = g_new0(IntervalTreeNode, 1);
i->start = start;
i->last = last;
interval_tree_insert(i, &shm_regions);
}
static abi_ptr shm_region_find(abi_ptr start)
{
IntervalTreeNode *i;
for (i = interval_tree_iter_first(&shm_regions, start, start); i;
i = interval_tree_iter_next(i, start, start)) {
if (i->start == start) {
return i->last;
}
}
return 0;
}
static void shm_region_rm_complete(abi_ptr start, abi_ptr last)
{
IntervalTreeNode *i, *n;
for (i = interval_tree_iter_first(&shm_regions, start, last); i; i = n) {
n = interval_tree_iter_next(i, start, last);
if (i->start >= start && i->last <= last) {
interval_tree_remove(i, &shm_regions);
g_free(i);
}
}
}
/*
* Validate target prot bitmask.
* Return the prot bitmask for the host in *HOST_PROT.
* Return 0 if the target prot bitmask is invalid, otherwise
* the internal qemu page_flags (which will include PAGE_VALID).
*/
static int validate_prot_to_pageflags(int prot)
{
int valid = PROT_READ | PROT_WRITE | PROT_EXEC | TARGET_PROT_SEM;
int page_flags = (prot & PAGE_BITS) | PAGE_VALID;
#ifdef TARGET_AARCH64
{
ARMCPU *cpu = ARM_CPU(thread_cpu);
/*
* The PROT_BTI bit is only accepted if the cpu supports the feature.
* Since this is the unusual case, don't bother checking unless
* the bit has been requested. If set and valid, record the bit
* within QEMU's page_flags.
*/
if ((prot & TARGET_PROT_BTI) && cpu_isar_feature(aa64_bti, cpu)) {
valid |= TARGET_PROT_BTI;
page_flags |= PAGE_BTI;
}
/* Similarly for the PROT_MTE bit. */
if ((prot & TARGET_PROT_MTE) && cpu_isar_feature(aa64_mte, cpu)) {
valid |= TARGET_PROT_MTE;
page_flags |= PAGE_MTE;
}
}
#elif defined(TARGET_HPPA)
valid |= PROT_GROWSDOWN | PROT_GROWSUP;
#endif
return prot & ~valid ? 0 : page_flags;
}
/*
* For the host, we need not pass anything except read/write/exec.
* While PROT_SEM is allowed by all hosts, it is also ignored, so
* don't bother transforming guest bit to host bit. Any other
* target-specific prot bits will not be understood by the host
* and will need to be encoded into page_flags for qemu emulation.
*
* Pages that are executable by the guest will never be executed
* by the host, but the host will need to be able to read them.
*/
static int target_to_host_prot(int prot)
{
return (prot & (PROT_READ | PROT_WRITE)) |
(prot & PROT_EXEC ? PROT_READ : 0);
}
/* NOTE: all the constants are the HOST ones, but addresses are target. */
int target_mprotect(abi_ulong start, abi_ulong len, int target_prot)
{
int host_page_size = qemu_real_host_page_size();
abi_ulong starts[3];
abi_ulong lens[3];
int prots[3];
abi_ulong host_start, host_last, last;
int prot1, ret, page_flags, nranges;
trace_target_mprotect(start, len, target_prot);
if ((start & ~TARGET_PAGE_MASK) != 0) {
return -TARGET_EINVAL;
}
page_flags = validate_prot_to_pageflags(target_prot);
if (!page_flags) {
return -TARGET_EINVAL;
}
if (len == 0) {
return 0;
}
len = TARGET_PAGE_ALIGN(len);
if (!guest_range_valid_untagged(start, len)) {
return -TARGET_ENOMEM;
}
last = start + len - 1;
host_start = start & -host_page_size;
host_last = ROUND_UP(last, host_page_size) - 1;
nranges = 0;
mmap_lock();
if (host_last - host_start < host_page_size) {
/* Single host page contains all guest pages: sum the prot. */
prot1 = target_prot;
for (abi_ulong a = host_start; a < start; a += TARGET_PAGE_SIZE) {
prot1 |= page_get_flags(a);
}
for (abi_ulong a = last; a < host_last; a += TARGET_PAGE_SIZE) {
prot1 |= page_get_flags(a + 1);
}
starts[nranges] = host_start;
lens[nranges] = host_page_size;
prots[nranges] = prot1;
nranges++;
} else {
if (host_start < start) {
/* Host page contains more than one guest page: sum the prot. */
prot1 = target_prot;
for (abi_ulong a = host_start; a < start; a += TARGET_PAGE_SIZE) {
prot1 |= page_get_flags(a);
}
/* If the resulting sum differs, create a new range. */
if (prot1 != target_prot) {
starts[nranges] = host_start;
lens[nranges] = host_page_size;
prots[nranges] = prot1;
nranges++;
host_start += host_page_size;
}
}
if (last < host_last) {
/* Host page contains more than one guest page: sum the prot. */
prot1 = target_prot;
for (abi_ulong a = last; a < host_last; a += TARGET_PAGE_SIZE) {
prot1 |= page_get_flags(a + 1);
}
/* If the resulting sum differs, create a new range. */
if (prot1 != target_prot) {
host_last -= host_page_size;
starts[nranges] = host_last + 1;
lens[nranges] = host_page_size;
prots[nranges] = prot1;
nranges++;
}
}
/* Create a range for the middle, if any remains. */
if (host_start < host_last) {
starts[nranges] = host_start;
lens[nranges] = host_last - host_start + 1;
prots[nranges] = target_prot;
nranges++;
}
}
for (int i = 0; i < nranges; ++i) {
ret = mprotect(g2h_untagged(starts[i]), lens[i],
target_to_host_prot(prots[i]));
if (ret != 0) {
goto error;
}
}
page_set_flags(start, last, page_flags);
ret = 0;
error:
mmap_unlock();
return ret;
}
/*
* Perform munmap on behalf of the target, with host parameters.
* If reserved_va, we must replace the memory reservation.
*/
static int do_munmap(void *addr, size_t len)
{
if (reserved_va) {
void *ptr = mmap(addr, len, PROT_NONE,
MAP_FIXED | MAP_ANONYMOUS
| MAP_PRIVATE | MAP_NORESERVE, -1, 0);
return ptr == addr ? 0 : -1;
}
return munmap(addr, len);
}
/*
* Map an incomplete host page.
*
* Here be dragons. This case will not work if there is an existing
* overlapping host page, which is file mapped, and for which the mapping
* is beyond the end of the file. In that case, we will see SIGBUS when
* trying to write a portion of this page.
*
* FIXME: Work around this with a temporary signal handler and longjmp.
*/
static bool mmap_frag(abi_ulong real_start, abi_ulong start, abi_ulong last,
int prot, int flags, int fd, off_t offset)
{
int host_page_size = qemu_real_host_page_size();
abi_ulong real_last;
void *host_start;
int prot_old, prot_new;
int host_prot_old, host_prot_new;
if (!(flags & MAP_ANONYMOUS)
&& (flags & MAP_TYPE) == MAP_SHARED
&& (prot & PROT_WRITE)) {
/*
* msync() won't work with the partial page, so we return an
* error if write is possible while it is a shared mapping.
*/
errno = EINVAL;
return false;
}
real_last = real_start + host_page_size - 1;
host_start = g2h_untagged(real_start);
/* Get the protection of the target pages outside the mapping. */
prot_old = 0;
for (abi_ulong a = real_start; a < start; a += TARGET_PAGE_SIZE) {
prot_old |= page_get_flags(a);
}
for (abi_ulong a = real_last; a > last; a -= TARGET_PAGE_SIZE) {
prot_old |= page_get_flags(a);
}
if (prot_old == 0) {
/*
* Since !(prot_old & PAGE_VALID), there were no guest pages
* outside of the fragment we need to map. Allocate a new host
* page to cover, discarding whatever else may have been present.
*/
void *p = mmap(host_start, host_page_size,
target_to_host_prot(prot),
flags | MAP_ANONYMOUS, -1, 0);
if (p != host_start) {
if (p != MAP_FAILED) {
do_munmap(p, host_page_size);
errno = EEXIST;
}
return false;
}
prot_old = prot;
}
prot_new = prot | prot_old;
host_prot_old = target_to_host_prot(prot_old);
host_prot_new = target_to_host_prot(prot_new);
/* Adjust protection to be able to write. */
if (!(host_prot_old & PROT_WRITE)) {
host_prot_old |= PROT_WRITE;
mprotect(host_start, host_page_size, host_prot_old);
}
/* Read or zero the new guest pages. */
if (flags & MAP_ANONYMOUS) {
memset(g2h_untagged(start), 0, last - start + 1);
} else {
if (pread(fd, g2h_untagged(start), last - start + 1, offset) == -1) {
return false;
}
}
/* Put final protection */
if (host_prot_new != host_prot_old) {
mprotect(host_start, host_page_size, host_prot_new);
}
return true;
}
abi_ulong task_unmapped_base;
abi_ulong elf_et_dyn_base;
abi_ulong mmap_next_start;
/*
* 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 align)
{
target_ulong ret;
ret = page_find_range_empty(start, reserved_va, size, align);
if (ret == -1 && start > mmap_min_addr) {
/* Restart at the beginning of the address space. */
ret = page_find_range_empty(mmap_min_addr, start - 1, size, align);
}
return ret;
}
/*
* 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, abi_ulong align)
{
int host_page_size = qemu_real_host_page_size();
void *ptr, *prev;
abi_ulong addr;
int wrapped, repeat;
align = MAX(align, host_page_size);
/* If 'start' == 0, then a default start address is used. */
if (start == 0) {
start = mmap_next_start;
} else {
start &= -host_page_size;
}
start = ROUND_UP(start, align);
size = ROUND_UP(size, host_page_size);
if (reserved_va) {
return mmap_find_vma_reserved(start, size, align);
}
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_untagged(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 & (align - 1)) == 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 = ROUND_UP(addr, align);
break;
case 1:
/*
* Sometimes the kernel decides to perform the allocation
* at the top end of memory instead.
*/
addr &= -align;
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;
}
}
}
/*
* Record a successful mmap within the user-exec interval tree.
*/
static abi_long mmap_end(abi_ulong start, abi_ulong last,
abi_ulong passthrough_start,
abi_ulong passthrough_last,
int flags, int page_flags)
{
if (flags & MAP_ANONYMOUS) {
page_flags |= PAGE_ANON;
}
page_flags |= PAGE_RESET;
if (passthrough_start > passthrough_last) {
page_set_flags(start, last, page_flags);
} else {
if (start < passthrough_start) {
page_set_flags(start, passthrough_start - 1, page_flags);
}
page_set_flags(passthrough_start, passthrough_last,
page_flags | PAGE_PASSTHROUGH);
if (passthrough_last < last) {
page_set_flags(passthrough_last + 1, last, page_flags);
}
}
shm_region_rm_complete(start, last);
trace_target_mmap_complete(start);
if (qemu_loglevel_mask(CPU_LOG_PAGE)) {
FILE *f = qemu_log_trylock();
if (f) {
fprintf(f, "page layout changed following mmap\n");
page_dump(f);
qemu_log_unlock(f);
}
}
return start;
}
/*
* Special case host page size == target page size,
* where there are no edge conditions.
*/
static abi_long mmap_h_eq_g(abi_ulong start, abi_ulong len,
int host_prot, int flags, int page_flags,
int fd, off_t offset)
{
void *p, *want_p = g2h_untagged(start);
abi_ulong last;
p = mmap(want_p, len, host_prot, flags, fd, offset);
if (p == MAP_FAILED) {
return -1;
}
/* If the host kernel does not support MAP_FIXED_NOREPLACE, emulate. */
if ((flags & MAP_FIXED_NOREPLACE) && p != want_p) {
do_munmap(p, len);
errno = EEXIST;
return -1;
}
start = h2g(p);
last = start + len - 1;
return mmap_end(start, last, start, last, flags, page_flags);
}
/*
* Special case host page size < target page size.
*
* The two special cases are increased guest alignment, and mapping
* past the end of a file.
*
* 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.
*
* This workaround only works for files that do not change.
* If the file is later extended (e.g. ftruncate), the SIGBUS
* vanishes and the proper behaviour is that changes within the
* anon page should be reflected in the file.
*
* However, this case is rather common with executable images,
* so the workaround is important for even trivial tests, whereas
* the mmap of of a file being extended is less common.
*/
static abi_long mmap_h_lt_g(abi_ulong start, abi_ulong len, int host_prot,
int mmap_flags, int page_flags, int fd,
off_t offset, int host_page_size)
{
void *p, *want_p = g2h_untagged(start);
off_t fileend_adj = 0;
int flags = mmap_flags;
abi_ulong last, pass_last;
if (!(flags & MAP_ANONYMOUS)) {
struct stat sb;
if (fstat(fd, &sb) == -1) {
return -1;
}
if (offset >= sb.st_size) {
/*
* The entire map is beyond the end of the file.
* Transform it to an anonymous mapping.
*/
flags |= MAP_ANONYMOUS;
fd = -1;
offset = 0;
} else if (offset + len > sb.st_size) {
/*
* A portion of the map is beyond the end of the file.
* Truncate the file portion of the allocation.
*/
fileend_adj = offset + len - sb.st_size;
}
}
if (flags & (MAP_FIXED | MAP_FIXED_NOREPLACE)) {
if (fileend_adj) {
p = mmap(want_p, len, host_prot, flags | MAP_ANONYMOUS, -1, 0);
} else {
p = mmap(want_p, len, host_prot, flags, fd, offset);
}
if (p != want_p) {
if (p != MAP_FAILED) {
/* Host does not support MAP_FIXED_NOREPLACE: emulate. */
do_munmap(p, len);
errno = EEXIST;
}
return -1;
}
if (fileend_adj) {
void *t = mmap(p, len - fileend_adj, host_prot,
(flags & ~MAP_FIXED_NOREPLACE) | MAP_FIXED,
fd, offset);
if (t == MAP_FAILED) {
int save_errno = errno;
/*
* We failed a map over the top of the successful anonymous
* mapping above. The only failure mode is running out of VMAs,
* and there's nothing that we can do to detect that earlier.
* If we have replaced an existing mapping with MAP_FIXED,
* then we cannot properly recover. It's a coin toss whether
* it would be better to exit or continue here.
*/
if (!(flags & MAP_FIXED_NOREPLACE) &&
!page_check_range_empty(start, start + len - 1)) {
qemu_log("QEMU target_mmap late failure: %s",
strerror(save_errno));
}
do_munmap(want_p, len);
errno = save_errno;
return -1;
}
}
} else {
size_t host_len, part_len;
/*
* Take care to align the host memory. Perform a larger anonymous
* allocation and extract the aligned portion. Remap the file on
* top of that.
*/
host_len = len + TARGET_PAGE_SIZE - host_page_size;
p = mmap(want_p, host_len, host_prot, flags | MAP_ANONYMOUS, -1, 0);
if (p == MAP_FAILED) {
return -1;
}
part_len = (uintptr_t)p & (TARGET_PAGE_SIZE - 1);
if (part_len) {
part_len = TARGET_PAGE_SIZE - part_len;
do_munmap(p, part_len);
p += part_len;
host_len -= part_len;
}
if (len < host_len) {
do_munmap(p + len, host_len - len);
}
if (!(flags & MAP_ANONYMOUS)) {
void *t = mmap(p, len - fileend_adj, host_prot,
flags | MAP_FIXED, fd, offset);
if (t == MAP_FAILED) {
int save_errno = errno;
do_munmap(p, len);
errno = save_errno;
return -1;
}
}
start = h2g(p);
}
last = start + len - 1;
if (fileend_adj) {
pass_last = ROUND_UP(last - fileend_adj, host_page_size) - 1;
} else {
pass_last = last;
}
return mmap_end(start, last, start, pass_last, mmap_flags, page_flags);
}
/*
* Special case host page size > target page size.
*
* The two special cases are address and file offsets that are valid
* for the guest that cannot be directly represented by the host.
*/
static abi_long mmap_h_gt_g(abi_ulong start, abi_ulong len,
int target_prot, int host_prot,
int flags, int page_flags, int fd,
off_t offset, int host_page_size)
{
void *p, *want_p = g2h_untagged(start);
off_t host_offset = offset & -host_page_size;
abi_ulong last, real_start, real_last;
bool misaligned_offset = false;
size_t host_len;
if (!(flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) {
/*
* Adjust the offset to something representable on the host.
*/
host_len = len + offset - host_offset;
p = mmap(want_p, host_len, host_prot, flags, fd, host_offset);
if (p == MAP_FAILED) {
return -1;
}
/* Update start to the file position at offset. */
p += offset - host_offset;
start = h2g(p);
last = start + len - 1;
return mmap_end(start, last, start, last, flags, page_flags);
}
if (!(flags & MAP_ANONYMOUS)) {
misaligned_offset = (start ^ offset) & (host_page_size - 1);
/*
* The fallback for misalignment is a private mapping + read.
* This carries none of semantics required of MAP_SHARED.
*/
if (misaligned_offset && (flags & MAP_TYPE) != MAP_PRIVATE) {
errno = EINVAL;
return -1;
}
}
last = start + len - 1;
real_start = start & -host_page_size;
real_last = ROUND_UP(last, host_page_size) - 1;
/*
* Handle the start and end of the mapping.
*/
if (real_start < start) {
abi_ulong real_page_last = real_start + host_page_size - 1;
if (last <= real_page_last) {
/* Entire allocation a subset of one host page. */
if (!mmap_frag(real_start, start, last, target_prot,
flags, fd, offset)) {
return -1;
}
return mmap_end(start, last, -1, 0, flags, page_flags);
}
if (!mmap_frag(real_start, start, real_page_last, target_prot,
flags, fd, offset)) {
return -1;
}
real_start = real_page_last + 1;
}
if (last < real_last) {
abi_ulong real_page_start = real_last - host_page_size + 1;
if (!mmap_frag(real_page_start, real_page_start, last,
target_prot, flags, fd,
offset + real_page_start - start)) {
return -1;
}
real_last = real_page_start - 1;
}
if (real_start > real_last) {
return mmap_end(start, last, -1, 0, flags, page_flags);
}
/*
* Handle the middle of the mapping.
*/
host_len = real_last - real_start + 1;
want_p += real_start - start;
if (flags & MAP_ANONYMOUS) {
p = mmap(want_p, host_len, host_prot, flags, -1, 0);
} else if (!misaligned_offset) {
p = mmap(want_p, host_len, host_prot, flags, fd,
offset + real_start - start);
} else {
p = mmap(want_p, host_len, host_prot | PROT_WRITE,
flags | MAP_ANONYMOUS, -1, 0);
}
if (p != want_p) {
if (p != MAP_FAILED) {
do_munmap(p, host_len);
errno = EEXIST;
}
return -1;
}
if (misaligned_offset) {
/* TODO: The read could be short. */
if (pread(fd, p, host_len, offset + real_start - start) != host_len) {
do_munmap(p, host_len);
return -1;
}
if (!(host_prot & PROT_WRITE)) {
mprotect(p, host_len, host_prot);
}
}
return mmap_end(start, last, -1, 0, flags, page_flags);
}
static abi_long target_mmap__locked(abi_ulong start, abi_ulong len,
int target_prot, int flags, int page_flags,
int fd, off_t offset)
{
int host_page_size = qemu_real_host_page_size();
int host_prot;
/*
* For reserved_va, we are in full control of the allocation.
* Find a suitable hole and convert to MAP_FIXED.
*/
if (reserved_va) {
if (flags & MAP_FIXED_NOREPLACE) {
/* Validate that the chosen range is empty. */
if (!page_check_range_empty(start, start + len - 1)) {
errno = EEXIST;
return -1;
}
flags = (flags & ~MAP_FIXED_NOREPLACE) | MAP_FIXED;
} else if (!(flags & MAP_FIXED)) {
abi_ulong real_start = start & -host_page_size;
off_t host_offset = offset & -host_page_size;
size_t real_len = len + offset - host_offset;
abi_ulong align = MAX(host_page_size, TARGET_PAGE_SIZE);
start = mmap_find_vma(real_start, real_len, align);
if (start == (abi_ulong)-1) {
errno = ENOMEM;
return -1;
}
start += offset - host_offset;
flags |= MAP_FIXED;
}
}
host_prot = target_to_host_prot(target_prot);
if (host_page_size == TARGET_PAGE_SIZE) {
return mmap_h_eq_g(start, len, host_prot, flags,
page_flags, fd, offset);
} else if (host_page_size < TARGET_PAGE_SIZE) {
return mmap_h_lt_g(start, len, host_prot, flags,
page_flags, fd, offset, host_page_size);
} else {
return mmap_h_gt_g(start, len, target_prot, host_prot, flags,
page_flags, fd, offset, host_page_size);
}
}
/* NOTE: all the constants are the HOST ones */
abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
int flags, int fd, off_t offset)
{
abi_long ret;
int page_flags;
trace_target_mmap(start, len, target_prot, flags, fd, offset);
if (!len) {
errno = EINVAL;
return -1;
}
page_flags = validate_prot_to_pageflags(target_prot);
if (!page_flags) {
errno = EINVAL;
return -1;
}
/* Also check for overflows... */
len = TARGET_PAGE_ALIGN(len);
if (!len || len != (size_t)len) {
errno = ENOMEM;
return -1;
}
if (offset & ~TARGET_PAGE_MASK) {
errno = EINVAL;
return -1;
}
if (flags & (MAP_FIXED | MAP_FIXED_NOREPLACE)) {
if (start & ~TARGET_PAGE_MASK) {
errno = EINVAL;
return -1;
}
if (!guest_range_valid_untagged(start, len)) {
errno = ENOMEM;
return -1;
}
}
mmap_lock();
ret = target_mmap__locked(start, len, target_prot, flags,
page_flags, fd, offset);
mmap_unlock();
/*
* If we're mapping shared memory, ensure we generate code for parallel
* execution and flush old translations. This will work up to the level
* supported by the host -- anything that requires EXCP_ATOMIC will not
* be atomic with respect to an external process.
*/
if (ret != -1 && (flags & MAP_TYPE) != MAP_PRIVATE) {
CPUState *cpu = thread_cpu;
if (!(cpu->tcg_cflags & CF_PARALLEL)) {
cpu->tcg_cflags |= CF_PARALLEL;
tb_flush(cpu);
}
}
return ret;
}
static int mmap_reserve_or_unmap(abi_ulong start, abi_ulong len)
{
int host_page_size = qemu_real_host_page_size();
abi_ulong real_start;
abi_ulong real_last;
abi_ulong real_len;
abi_ulong last;
abi_ulong a;
void *host_start;
int prot;
last = start + len - 1;
real_start = start & -host_page_size;
real_last = ROUND_UP(last, host_page_size) - 1;
/*
* If guest pages remain on the first or last host pages,
* adjust the deallocation to retain those guest pages.
* The single page special case is required for the last page,
* lest real_start overflow to zero.
*/
if (real_last - real_start < host_page_size) {
prot = 0;
for (a = real_start; a < start; a += TARGET_PAGE_SIZE) {
prot |= page_get_flags(a);
}
for (a = last; a < real_last; a += TARGET_PAGE_SIZE) {
prot |= page_get_flags(a + 1);
}
if (prot != 0) {
return 0;
}
} else {
for (prot = 0, a = real_start; a < start; a += TARGET_PAGE_SIZE) {
prot |= page_get_flags(a);
}
if (prot != 0) {
real_start += host_page_size;
}
for (prot = 0, a = last; a < real_last; a += TARGET_PAGE_SIZE) {
prot |= page_get_flags(a + 1);
}
if (prot != 0) {
real_last -= host_page_size;
}
if (real_last < real_start) {
return 0;
}
}
real_len = real_last - real_start + 1;
host_start = g2h_untagged(real_start);
return do_munmap(host_start, real_len);
}
int target_munmap(abi_ulong start, abi_ulong len)
{
int ret;
trace_target_munmap(start, len);
if (start & ~TARGET_PAGE_MASK) {
errno = EINVAL;
return -1;
}
len = TARGET_PAGE_ALIGN(len);
if (len == 0 || !guest_range_valid_untagged(start, len)) {
errno = EINVAL;
return -1;
}
mmap_lock();
ret = mmap_reserve_or_unmap(start, len);
if (likely(ret == 0)) {
page_set_flags(start, start + len - 1, 0);
shm_region_rm_complete(start, start + len - 1);
}
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;
if (!guest_range_valid_untagged(old_addr, old_size) ||
((flags & MREMAP_FIXED) &&
!guest_range_valid_untagged(new_addr, new_size)) ||
((flags & MREMAP_MAYMOVE) == 0 &&
!guest_range_valid_untagged(old_addr, new_size))) {
errno = ENOMEM;
return -1;
}
mmap_lock();
if (flags & MREMAP_FIXED) {
host_addr = mremap(g2h_untagged(old_addr), old_size, new_size,
flags, g2h_untagged(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_or_unmap(old_addr, old_size);
}
} else if (flags & MREMAP_MAYMOVE) {
abi_ulong mmap_start;
mmap_start = mmap_find_vma(0, new_size, TARGET_PAGE_SIZE);
if (mmap_start == -1) {
errno = ENOMEM;
host_addr = MAP_FAILED;
} else {
host_addr = mremap(g2h_untagged(old_addr), old_size, new_size,
flags | MREMAP_FIXED,
g2h_untagged(mmap_start));
if (reserved_va) {
mmap_reserve_or_unmap(old_addr, old_size);
}
}
} else {
int page_flags = 0;
if (reserved_va && old_size < new_size) {
abi_ulong addr;
for (addr = old_addr + old_size;
addr < old_addr + new_size;
addr++) {
page_flags |= page_get_flags(addr);
}
}
if (page_flags == 0) {
host_addr = mremap(g2h_untagged(old_addr),
old_size, new_size, flags);
if (host_addr != MAP_FAILED) {
/* Check if address fits target address space */
if (!guest_range_valid_untagged(h2g(host_addr), new_size)) {
/* Revert mremap() changes */
host_addr = mremap(g2h_untagged(old_addr),
new_size, old_size, flags);
errno = ENOMEM;
host_addr = MAP_FAILED;
} else if (reserved_va && old_size > new_size) {
mmap_reserve_or_unmap(old_addr + old_size,
old_size - new_size);
}
}
} else {
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 - 1, 0);
shm_region_rm_complete(old_addr, old_addr + old_size - 1);
page_set_flags(new_addr, new_addr + new_size - 1,
prot | PAGE_VALID | PAGE_RESET);
shm_region_rm_complete(new_addr, new_addr + new_size - 1);
}
mmap_unlock();
return new_addr;
}
abi_long target_madvise(abi_ulong start, abi_ulong len_in, int advice)
{
abi_ulong len;
int ret = 0;
if (start & ~TARGET_PAGE_MASK) {
return -TARGET_EINVAL;
}
if (len_in == 0) {
return 0;
}
len = TARGET_PAGE_ALIGN(len_in);
if (len == 0 || !guest_range_valid_untagged(start, len)) {
return -TARGET_EINVAL;
}
/* Translate for some architectures which have different MADV_xxx values */
switch (advice) {
case TARGET_MADV_DONTNEED: /* alpha */
advice = MADV_DONTNEED;
break;
case TARGET_MADV_WIPEONFORK: /* parisc */
advice = MADV_WIPEONFORK;
break;
case TARGET_MADV_KEEPONFORK: /* parisc */
advice = MADV_KEEPONFORK;
break;
/* we do not care about the other MADV_xxx values yet */
}
/*
* Most advice values are hints, so ignoring and returning success is ok.
*
* However, some advice values such as MADV_DONTNEED, MADV_WIPEONFORK and
* MADV_KEEPONFORK are not hints and need to be emulated.
*
* A straight passthrough for those may not be safe because qemu sometimes
* turns private file-backed mappings into anonymous mappings.
* If all guest pages have PAGE_PASSTHROUGH set, mappings have the
* same semantics for the host as for the guest.
*
* We pass through MADV_WIPEONFORK and MADV_KEEPONFORK if possible and
* return failure if not.
*
* MADV_DONTNEED is passed through as well, if possible.
* If passthrough isn't possible, we nevertheless (wrongly!) return
* success, which is broken but some userspace programs fail to work
* otherwise. Completely implementing such emulation is quite complicated
* though.
*/
mmap_lock();
switch (advice) {
case MADV_WIPEONFORK:
case MADV_KEEPONFORK:
ret = -EINVAL;
/* fall through */
case MADV_DONTNEED:
if (page_check_range(start, len, PAGE_PASSTHROUGH)) {
ret = get_errno(madvise(g2h_untagged(start), len, advice));
if ((advice == MADV_DONTNEED) && (ret == 0)) {
page_reset_target_data(start, start + len - 1);
}
}
}
mmap_unlock();
return ret;
}
#ifndef TARGET_FORCE_SHMLBA
/*
* For most architectures, SHMLBA is the same as the page size;
* some architectures have larger values, in which case they should
* define TARGET_FORCE_SHMLBA and provide a target_shmlba() function.
* This corresponds to the kernel arch code defining __ARCH_FORCE_SHMLBA
* and defining its own value for SHMLBA.
*
* The kernel also permits SHMLBA to be set by the architecture to a
* value larger than the page size without setting __ARCH_FORCE_SHMLBA;
* this means that addresses are rounded to the large size if
* SHM_RND is set but addresses not aligned to that size are not rejected
* as long as they are at least page-aligned. Since the only architecture
* which uses this is ia64 this code doesn't provide for that oddity.
*/
static inline abi_ulong target_shmlba(CPUArchState *cpu_env)
{
return TARGET_PAGE_SIZE;
}
#endif
#if defined(__arm__) || defined(__mips__) || defined(__sparc__)
#define HOST_FORCE_SHMLBA 1
#else
#define HOST_FORCE_SHMLBA 0
#endif
abi_ulong target_shmat(CPUArchState *cpu_env, int shmid,
abi_ulong shmaddr, int shmflg)
{
CPUState *cpu = env_cpu(cpu_env);
struct shmid_ds shm_info;
int ret;
int h_pagesize;
int t_shmlba, h_shmlba, m_shmlba;
size_t t_len, h_len, m_len;
/* shmat pointers are always untagged */
/*
* Because we can't use host shmat() unless the address is sufficiently
* aligned for the host, we'll need to check both.
* TODO: Could be fixed with softmmu.
*/
t_shmlba = target_shmlba(cpu_env);
h_pagesize = qemu_real_host_page_size();
h_shmlba = (HOST_FORCE_SHMLBA ? SHMLBA : h_pagesize);
m_shmlba = MAX(t_shmlba, h_shmlba);
if (shmaddr) {
if (shmaddr & (m_shmlba - 1)) {
if (shmflg & SHM_RND) {
/*
* The guest is allowing the kernel to round the address.
* Assume that the guest is ok with us rounding to the
* host required alignment too. Anyway if we don't, we'll
* get an error from the kernel.
*/
shmaddr &= ~(m_shmlba - 1);
if (shmaddr == 0 && (shmflg & SHM_REMAP)) {
return -TARGET_EINVAL;
}
} else {
int require = TARGET_PAGE_SIZE;
#ifdef TARGET_FORCE_SHMLBA
require = t_shmlba;
#endif
/*
* Include host required alignment, as otherwise we cannot
* use host shmat at all.
*/
require = MAX(require, h_shmlba);
if (shmaddr & (require - 1)) {
return -TARGET_EINVAL;
}
}
}
} else {
if (shmflg & SHM_REMAP) {
return -TARGET_EINVAL;
}
}
/* All rounding now manually concluded. */
shmflg &= ~SHM_RND;
/* Find out the length of the shared memory segment. */
ret = get_errno(shmctl(shmid, IPC_STAT, &shm_info));
if (is_error(ret)) {
/* can't get length, bail out */
return ret;
}
t_len = TARGET_PAGE_ALIGN(shm_info.shm_segsz);
h_len = ROUND_UP(shm_info.shm_segsz, h_pagesize);
m_len = MAX(t_len, h_len);
if (!guest_range_valid_untagged(shmaddr, m_len)) {
return -TARGET_EINVAL;
}
WITH_MMAP_LOCK_GUARD() {
bool mapped = false;
void *want, *test;
abi_ulong last;
if (!shmaddr) {
shmaddr = mmap_find_vma(0, m_len, m_shmlba);
if (shmaddr == -1) {
return -TARGET_ENOMEM;
}
mapped = !reserved_va;
} else if (shmflg & SHM_REMAP) {
/*
* If host page size > target page size, the host shmat may map
* more memory than the guest expects. Reject a mapping that
* would replace memory in the unexpected gap.
* TODO: Could be fixed with softmmu.
*/
if (t_len < h_len &&
!page_check_range_empty(shmaddr + t_len,
shmaddr + h_len - 1)) {
return -TARGET_EINVAL;
}
} else {
if (!page_check_range_empty(shmaddr, shmaddr + m_len - 1)) {
return -TARGET_EINVAL;
}
}
/* All placement is now complete. */
want = (void *)g2h_untagged(shmaddr);
/*
* Map anonymous pages across the entire range, then remap with
* the shared memory. This is required for a number of corner
* cases for which host and guest page sizes differ.
*/
if (h_len != t_len) {
int mmap_p = PROT_READ | (shmflg & SHM_RDONLY ? 0 : PROT_WRITE);
int mmap_f = MAP_PRIVATE | MAP_ANONYMOUS
| (reserved_va || (shmflg & SHM_REMAP)
? MAP_FIXED : MAP_FIXED_NOREPLACE);
test = mmap(want, m_len, mmap_p, mmap_f, -1, 0);
if (unlikely(test != want)) {
/* shmat returns EINVAL not EEXIST like mmap. */
ret = (test == MAP_FAILED && errno != EEXIST
? get_errno(-1) : -TARGET_EINVAL);
if (mapped) {
do_munmap(want, m_len);
}
return ret;
}
mapped = true;
}
if (reserved_va || mapped) {
shmflg |= SHM_REMAP;
}
test = shmat(shmid, want, shmflg);
if (test == MAP_FAILED) {
ret = get_errno(-1);
if (mapped) {
do_munmap(want, m_len);
}
return ret;
}
assert(test == want);
last = shmaddr + m_len - 1;
page_set_flags(shmaddr, last,
PAGE_VALID | PAGE_RESET | PAGE_READ |
(shmflg & SHM_RDONLY ? 0 : PAGE_WRITE) |
(shmflg & SHM_EXEC ? PAGE_EXEC : 0));
shm_region_rm_complete(shmaddr, last);
shm_region_add(shmaddr, last);
}
/*
* We're mapping shared memory, so ensure we generate code for parallel
* execution and flush old translations. This will work up to the level
* supported by the host -- anything that requires EXCP_ATOMIC will not
* be atomic with respect to an external process.
*/
if (!(cpu->tcg_cflags & CF_PARALLEL)) {
cpu->tcg_cflags |= CF_PARALLEL;
tb_flush(cpu);
}
if (qemu_loglevel_mask(CPU_LOG_PAGE)) {
FILE *f = qemu_log_trylock();
if (f) {
fprintf(f, "page layout changed following shmat\n");
page_dump(f);
qemu_log_unlock(f);
}
}
return shmaddr;
}
abi_long target_shmdt(abi_ulong shmaddr)
{
abi_long rv;
/* shmdt pointers are always untagged */
WITH_MMAP_LOCK_GUARD() {
abi_ulong last = shm_region_find(shmaddr);
if (last == 0) {
return -TARGET_EINVAL;
}
rv = get_errno(shmdt(g2h_untagged(shmaddr)));
if (rv == 0) {
abi_ulong size = last - shmaddr + 1;
page_set_flags(shmaddr, last, 0);
shm_region_rm_complete(shmaddr, last);
mmap_reserve_or_unmap(shmaddr, size);
}
}
return rv;
}
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