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qemu/bsd-user/mmap.c
Stacey Son 4e00b7d85d bsd-user: Implement shmat(2) and shmdt(2) 
Use `WITH_MMAP_LOCK_GUARD` instead of mmap_lock() and mmap_unlock(),
to match linux-user implementation, according to the following commits:

69fa2708a2 linux-user: Use WITH_MMAP_LOCK_GUARD in target_{shmat,shmdt}
ceda5688b6 linux-user: Fix shmdt

Signed-off-by: Stacey Son <sson@FreeBSD.org>
Signed-off-by: Karim Taha <kariem.taha2.7@gmail.com>
Message-Id: <20230925182709.4834-23-kariem.taha2.7@gmail.com>
2023-10-03 17:14:07 -06:00

758 lines
23 KiB
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/*
* mmap support for qemu
*
* Copyright (c) 2003 - 2008 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 "qemu.h"
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);
}
/* 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;
qemu_log_mask(CPU_LOG_PAGE, "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' : '-');
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_untagged(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_untagged(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_untagged(host_start), host_end - host_start, prot);
if (ret != 0)
goto error;
}
page_set_flags(start, start + len - 1, prot | PAGE_VALID);
mmap_unlock();
return 0;
error:
mmap_unlock();
return ret;
}
/*
* map an incomplete host page
*
* mmap_frag can be called with a valid fd, if flags doesn't contain one of
* MAP_ANON, MAP_STACK, MAP_GUARD. If we need to map a page in those cases, we
* pass fd == -1. However, if flags contains MAP_GUARD then MAP_ANON cannot be
* added.
*
* * If fd is valid (not -1) we want to map the pages with MAP_ANON.
* * If flags contains MAP_GUARD we don't want to add MAP_ANON because it
* will be rejected. See kern_mmap's enforcing of constraints for MAP_GUARD
* in sys/vm/vm_mmap.c.
* * If flags contains MAP_ANON it doesn't matter if we add it or not.
* * If flags contains MAP_STACK, mmap adds MAP_ANON when called so doesn't
* matter if we add it or not either. See enforcing of constraints for
* MAP_STACK in kern_mmap.
*
* Don't add MAP_ANON for the flags that use fd == -1 without specifying the
* flags directly, with the assumption that future flags that require fd == -1
* will also not require MAP_ANON.
*/
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_untagged(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. See also above. */
void *p = mmap(host_start, qemu_host_page_size, prot,
flags | ((fd != -1) ? MAP_ANON : 0), -1, 0);
if (p == MAP_FAILED)
return -1;
prot1 = prot;
}
prot1 &= PAGE_BITS;
prot_new = prot | prot1;
if (fd != -1) {
/* msync() won't work here, so we return an error if write is
possible while it is a shared mapping */
if ((flags & TARGET_BSD_MAP_FLAGMASK) == 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_untagged(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 {
if (prot_new != prot1) {
mprotect(host_start, qemu_host_page_size, prot_new);
}
if (prot_new & PROT_WRITE) {
memset(g2h_untagged(start), 0, end - start);
}
}
return 0;
}
#if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64
# define TASK_UNMAPPED_BASE (1ul << 38)
#else
# define TASK_UNMAPPED_BASE 0x40000000
#endif
abi_ulong mmap_next_start = TASK_UNMAPPED_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 alignment)
{
abi_ulong ret;
ret = page_find_range_empty(start, reserved_va, size, alignment);
if (ret == -1 && start > TARGET_PAGE_SIZE) {
/* Restart at the beginning of the address space. */
ret = page_find_range_empty(TARGET_PAGE_SIZE, start - 1,
size, alignment);
}
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.
*/
static abi_ulong mmap_find_vma_aligned(abi_ulong start, abi_ulong size,
abi_ulong alignment)
{
void *ptr, *prev;
abi_ulong addr;
int flags;
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);
if (reserved_va) {
return mmap_find_vma_reserved(start, size,
(alignment != 0 ? 1 << alignment :
MAX(qemu_host_page_size, TARGET_PAGE_SIZE)));
}
addr = start;
wrapped = repeat = 0;
prev = 0;
flags = MAP_ANON | MAP_PRIVATE;
if (alignment != 0) {
flags |= MAP_ALIGNED(alignment);
}
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,
flags, -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 = TARGET_PAGE_SIZE;
} else if (wrapped && addr >= start) {
return (abi_ulong)-1;
}
}
}
abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
{
return mmap_find_vma_aligned(start, size, 0);
}
/* NOTE: all the constants are the HOST ones */
abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
int flags, int fd, off_t offset)
{
abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
mmap_lock();
if (qemu_loglevel_mask(CPU_LOG_PAGE)) {
qemu_log("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_ALIGNMENT_MASK) {
qemu_log("MAP_ALIGNED(%u) ",
(flags & MAP_ALIGNMENT_MASK) >> MAP_ALIGNMENT_SHIFT);
}
if (flags & MAP_GUARD) {
qemu_log("MAP_GUARD ");
}
if (flags & MAP_FIXED) {
qemu_log("MAP_FIXED ");
}
if (flags & MAP_ANON) {
qemu_log("MAP_ANON ");
}
if (flags & MAP_EXCL) {
qemu_log("MAP_EXCL ");
}
if (flags & MAP_PRIVATE) {
qemu_log("MAP_PRIVATE ");
}
if (flags & MAP_SHARED) {
qemu_log("MAP_SHARED ");
}
if (flags & MAP_NOCORE) {
qemu_log("MAP_NOCORE ");
}
if (flags & MAP_STACK) {
qemu_log("MAP_STACK ");
}
qemu_log("fd=%d offset=0x%lx\n", fd, offset);
}
if ((flags & MAP_ANON) && fd != -1) {
errno = EINVAL;
goto fail;
}
if (flags & MAP_STACK) {
if ((fd != -1) || ((prot & (PROT_READ | PROT_WRITE)) !=
(PROT_READ | PROT_WRITE))) {
errno = EINVAL;
goto fail;
}
}
if ((flags & MAP_GUARD) && (prot != PROT_NONE || fd != -1 ||
offset != 0 || (flags & (MAP_SHARED | MAP_PRIVATE |
/* MAP_PREFAULT | */ /* MAP_PREFAULT not in mman.h */
MAP_PREFAULT_READ | MAP_ANON | MAP_STACK)) != 0)) {
errno = EINVAL;
goto fail;
}
if (offset & ~TARGET_PAGE_MASK) {
errno = EINVAL;
goto fail;
}
if (len == 0) {
errno = EINVAL;
goto fail;
}
/* Check for overflows */
len = TARGET_PAGE_ALIGN(len);
if (len == 0) {
errno = ENOMEM;
goto fail;
}
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);
if ((flags & MAP_ALIGNMENT_MASK) != 0)
start = mmap_find_vma_aligned(real_start, host_len,
(flags & MAP_ALIGNMENT_MASK) >> MAP_ALIGNMENT_SHIFT);
else
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() < qemu_host_page_size) && fd != -1) {
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 = REAL_HOST_PAGE_ALIGN(sb.st_size - offset);
}
}
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_untagged(start), host_len, prot,
flags | MAP_FIXED | ((fd != -1) ? MAP_ANON : 0), -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 (fd != -1) {
p = mmap(g2h_untagged(start), len, prot,
flags | MAP_FIXED, fd, host_offset);
if (p == MAP_FAILED) {
munmap(g2h_untagged(start), host_len);
goto fail;
}
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 (!guest_range_valid_untagged(start, len)) {
errno = EINVAL;
goto fail;
}
/*
* worst case: we cannot map the file because the offset is not
* aligned, so we read it
*/
if (fd != -1 &&
(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 & TARGET_BSD_MAP_FLAGMASK) == MAP_SHARED &&
(prot & PROT_WRITE)) {
errno = EINVAL;
goto fail;
}
retaddr = target_mmap(start, len, prot | PROT_WRITE,
MAP_FIXED | MAP_PRIVATE | MAP_ANON,
-1, 0);
if (retaddr == -1)
goto fail;
if (pread(fd, g2h_untagged(start), len, offset) == -1) {
goto fail;
}
if (!(prot & PROT_WRITE)) {
ret = target_mprotect(start, len, prot);
assert(ret == 0);
}
goto the_end;
}
/* Reject the mapping if any page within the range is mapped */
if ((flags & MAP_EXCL) && !page_check_range_empty(start, end - 1)) {
errno = EINVAL;
goto fail;
}
/* 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, 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_ANON)
offset1 = 0;
else
offset1 = offset + real_start - start;
p = mmap(g2h_untagged(real_start), real_end - real_start,
prot, flags, fd, offset1);
if (p == MAP_FAILED)
goto fail;
}
}
the_end1:
page_set_flags(start, start + len - 1, 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;
}
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_untagged(real_start), real_end - real_start, PROT_NONE,
MAP_FIXED | MAP_ANON | MAP_PRIVATE, -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_untagged(real_start), real_end - real_start);
}
}
if (ret == 0) {
page_set_flags(start, start + len - 1, 0);
}
mmap_unlock();
return ret;
}
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_untagged(start), end - start, flags);
}
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