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qemu/bsd-user/mmap.c
Warner Losh be04f210f9 bsd-user: Update mapping to handle reserved and starting conditions 
Update the reserved base based on what platform we're on, as well as the
start of the mmap range. Update routines that find va ranges to interact
with the reserved ranges as well as properly align the mapping (this is
especially important for targets whose page size does not match the
host's). Loop where appropriate when the initial address space offered
by mmap does not meet the contraints.

This has 18e80c55bb from linux-user folded in to the upstream
bsd-user code as well.

Signed-off-by: Mikaël Urankar <mikael.urankar@gmail.com>
Signed-off-by: Stacey Son <sson@FreeBSD.org>
Signed-off-by: Warner Losh <imp@bsdimp.com>
Acked-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Kyle Evans <kevans@FreeBSD.org>
2021-09-10 14:13:06 -06:00

783 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"
#include "qemu-common.h"
//#define DEBUG_MMAP
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);
}
}
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;
#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_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, 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_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 */
void *p = mmap(host_start, qemu_host_page_size, prot,
flags | MAP_ANON, -1, 0);
if (p == MAP_FAILED)
return -1;
prot1 = prot;
}
prot1 &= PAGE_BITS;
prot_new = prot | prot1;
if (!(flags & MAP_ANON)) {
/* 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 */
pread(fd, g2h_untagged(start), end - start, offset);
/* 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)
#else
# define TASK_UNMAPPED_BASE 0x40000000
#endif
abi_ulong mmap_next_start = TASK_UNMAPPED_BASE;
unsigned long last_brk;
/*
* 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 addr;
abi_ulong end_addr;
int prot;
int looped = 0;
if (size > reserved_va) {
return (abi_ulong)-1;
}
size = HOST_PAGE_ALIGN(size) + alignment;
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 (end_addr - addr >= size) {
break;
}
addr -= qemu_host_page_size;
}
if (start == mmap_next_start) {
mmap_next_start = addr;
}
/* addr is sufficiently low to align it up */
if (alignment != 0) {
addr = (addr + alignment) & ~(alignment - 1);
}
return addr;
}
/*
* 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 : 0));
}
addr = start;
wrapped = repeat = 0;
prev = 0;
flags = MAP_ANONYMOUS | MAP_PRIVATE;
#ifdef MAP_ALIGNED
if (alignment != 0) {
flags |= MAP_ALIGNED(alignment);
}
#else
/* XXX TODO */
#endif
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();
#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_ALIGNMENT_MASK) {
printf("MAP_ALIGNED(%u) ", (flags & MAP_ALIGNMENT_MASK)
>> MAP_ALIGNMENT_SHIFT);
}
#if MAP_GUARD
if (flags & MAP_GUARD) {
printf("MAP_GUARD ");
}
#endif
if (flags & MAP_FIXED) {
printf("MAP_FIXED ");
}
if (flags & MAP_ANONYMOUS) {
printf("MAP_ANON ");
}
#ifdef MAP_EXCL
if (flags & MAP_EXCL) {
printf("MAP_EXCL ");
}
#endif
if (flags & MAP_PRIVATE) {
printf("MAP_PRIVATE ");
}
if (flags & MAP_SHARED) {
printf("MAP_SHARED ");
}
if (flags & MAP_NOCORE) {
printf("MAP_NOCORE ");
}
#ifdef MAP_STACK
if (flags & MAP_STACK) {
printf("MAP_STACK ");
}
#endif
printf("fd=%d offset=0x%llx\n", fd, offset);
}
#endif
if ((flags & MAP_ANONYMOUS) && fd != -1) {
errno = EINVAL;
goto fail;
}
#ifdef MAP_STACK
if (flags & MAP_STACK) {
if ((fd != -1) || ((prot & (PROT_READ | PROT_WRITE)) !=
(PROT_READ | PROT_WRITE))) {
errno = EINVAL;
goto fail;
}
}
#endif /* MAP_STACK */
#ifdef MAP_GUARD
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;
}
#endif
if (offset & ~TARGET_PAGE_MASK) {
errno = EINVAL;
goto fail;
}
len = TARGET_PAGE_ALIGN(len);
if (len == 0) {
errno = EINVAL;
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_ANONYMOUS : 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 TARGET_ABI_BITS == 32 && HOST_LONG_BITS == 64
if ((unsigned long)start + len - 1 > (abi_ulong) -1) {
errno = EINVAL;
goto fail;
}
#endif
/*
* worst case: we cannot map the file because the offset is not
* aligned, so we read it
*/
if (!(flags & MAP_ANON) &&
(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;
pread(fd, g2h_untagged(start), len, offset);
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, 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, 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);
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_untagged(real_start), real_end - real_start, PROT_NONE,
MAP_FIXED | MAP_ANONYMOUS | 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, 0);
tb_invalidate_phys_range(start, start + len);
}
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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