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qemu/linux-user/mmap.c
Helge Deller 4530deb1fe linux-user: Add emulation for MADV_WIPEONFORK and MADV_KEEPONFORK in madvise() 
Both parameters have a different value on the parisc platform, so first
translate the target value into a host value for usage in the native
madvise() syscall.

Those parameters are often used by security sensitive applications (e.g.
tor browser, boringssl, ...) which expect the call to return a proper
return code on failure, so return -EINVAL if qemu fails to forward the
syscall to the host OS.

While touching this code, enhance the comments about MADV_DONTNEED.

Tested with testcase of tor browser when running hppa-linux guest on
x86-64 host.

Signed-off-by: Helge Deller <deller@gmx.de>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <Y5iwTaydU7i66K/i@p100>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
2023-02-03 22:55:12 +01:00

957 lines
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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 "trace.h"
#include "exec/log.h"
#include "qemu.h"
#include "user-internals.h"
#include "user-mmap.h"
#include "target_mman.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)
{
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);
}
/*
* 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 *host_prot, int prot)
{
int valid = PROT_READ | PROT_WRITE | PROT_EXEC | TARGET_PROT_SEM;
int page_flags = (prot & PAGE_BITS) | PAGE_VALID;
/*
* 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.
*/
*host_prot = (prot & (PROT_READ | PROT_WRITE))
| (prot & PROT_EXEC ? PROT_READ : 0);
#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;
}
/* NOTE: all the constants are the HOST ones, but addresses are target. */
int target_mprotect(abi_ulong start, abi_ulong len, int target_prot)
{
abi_ulong end, host_start, host_end, addr;
int prot1, ret, page_flags, host_prot;
trace_target_mprotect(start, len, target_prot);
if ((start & ~TARGET_PAGE_MASK) != 0) {
return -TARGET_EINVAL;
}
page_flags = validate_prot_to_pageflags(&host_prot, target_prot);
if (!page_flags) {
return -TARGET_EINVAL;
}
len = TARGET_PAGE_ALIGN(len);
end = start + len;
if (!guest_range_valid_untagged(start, len)) {
return -TARGET_ENOMEM;
}
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 = host_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 = host_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, host_prot);
if (ret != 0) {
goto error;
}
}
page_set_flags(start, start + len, page_flags);
ret = 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_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_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
#ifdef TARGET_AARCH64
# define TASK_UNMAPPED_BASE 0x5500000000
#else
# define TASK_UNMAPPED_BASE (1ul << 38)
#endif
#else
#ifdef TARGET_HPPA
# define TASK_UNMAPPED_BASE 0xfa000000
#else
# define TASK_UNMAPPED_BASE 0x40000000
#endif
#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 align)
{
abi_ulong addr, end_addr, incr = qemu_host_page_size;
int prot;
bool looped = false;
if (size > reserved_va) {
return (abi_ulong)-1;
}
/* Note that start and size have already been aligned by mmap_find_vma. */
end_addr = start + size;
if (start > reserved_va - size) {
/* Start at the top of the address space. */
end_addr = ((reserved_va - size) & -align) + size;
looped = true;
}
/* Search downward from END_ADDR, checking to see if a page is in use. */
addr = end_addr;
while (1) {
addr -= incr;
if (addr > end_addr) {
if (looped) {
/* Failure. The entire address space has been searched. */
return (abi_ulong)-1;
}
/* Re-start at the top of the address space. */
addr = end_addr = ((reserved_va - size) & -align) + size;
looped = true;
} else {
prot = page_get_flags(addr);
if (prot) {
/* Page in use. Restart below this page. */
addr = end_addr = ((addr - size) & -align) + size;
} else if (addr && addr + size == end_addr) {
/* Success! All pages between ADDR and END_ADDR are free. */
if (start == mmap_next_start) {
mmap_next_start = addr;
}
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.
*/
abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size, abi_ulong align)
{
void *ptr, *prev;
abi_ulong addr;
int wrapped, repeat;
align = MAX(align, qemu_host_page_size);
/* If 'start' == 0, then a default start address is used. */
if (start == 0) {
start = mmap_next_start;
} else {
start &= qemu_host_page_mask;
}
start = ROUND_UP(start, align);
size = HOST_PAGE_ALIGN(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;
}
}
}
/* 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, abi_ulong offset)
{
abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len,
passthrough_start = -1, passthrough_end = -1;
int page_flags, host_prot;
mmap_lock();
trace_target_mmap(start, len, target_prot, flags, fd, offset);
if (!len) {
errno = EINVAL;
goto fail;
}
page_flags = validate_prot_to_pageflags(&host_prot, target_prot);
if (!page_flags) {
errno = EINVAL;
goto fail;
}
/* Also check for overflows... */
len = TARGET_PAGE_ALIGN(len);
if (!len) {
errno = ENOMEM;
goto fail;
}
if (offset & ~TARGET_PAGE_MASK) {
errno = EINVAL;
goto fail;
}
/*
* 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 (flags & MAP_SHARED) {
CPUState *cpu = thread_cpu;
if (!(cpu->tcg_cflags & CF_PARALLEL)) {
cpu->tcg_cflags |= CF_PARALLEL;
tb_flush(cpu);
}
}
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, TARGET_PAGE_SIZE);
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) &&
!(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 = 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, host_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_untagged(start), len, host_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);
passthrough_start = start;
passthrough_end = start + len;
} 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 (end < start || !guest_range_valid_untagged(start, len)) {
errno = ENOMEM;
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 &&
(host_prot & PROT_WRITE)) {
errno = EINVAL;
goto fail;
}
retaddr = target_mmap(start, len, target_prot | PROT_WRITE,
MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
-1, 0);
if (retaddr == -1)
goto fail;
if (pread(fd, g2h_untagged(start), len, offset) == -1)
goto fail;
if (!(host_prot & PROT_WRITE)) {
ret = target_mprotect(start, len, target_prot);
assert(ret == 0);
}
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,
host_prot, flags, fd, offset);
if (ret == -1)
goto fail;
goto the_end1;
}
ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,
host_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,
host_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_untagged(real_start), real_end - real_start,
host_prot, flags, fd, offset1);
if (p == MAP_FAILED)
goto fail;
passthrough_start = real_start;
passthrough_end = real_end;
}
}
the_end1:
if (flags & MAP_ANONYMOUS) {
page_flags |= PAGE_ANON;
}
page_flags |= PAGE_RESET;
if (passthrough_start == passthrough_end) {
page_set_flags(start, start + len, page_flags);
} else {
if (start < passthrough_start) {
page_set_flags(start, passthrough_start, page_flags);
}
page_set_flags(passthrough_start, passthrough_end,
page_flags | PAGE_PASSTHROUGH);
if (passthrough_end < start + len) {
page_set_flags(passthrough_end, start + len, page_flags);
}
}
the_end:
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);
}
}
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 | MAP_NORESERVE,
-1, 0);
}
}
int target_munmap(abi_ulong start, abi_ulong len)
{
abi_ulong end, real_start, real_end, addr;
int prot, ret;
trace_target_munmap(start, len);
if (start & ~TARGET_PAGE_MASK)
return -TARGET_EINVAL;
len = TARGET_PAGE_ALIGN(len);
if (len == 0 || !guest_range_valid_untagged(start, len)) {
return -TARGET_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);
}
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(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(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_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(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, 0);
page_set_flags(new_addr, new_addr + new_size,
prot | PAGE_VALID | PAGE_RESET);
}
mmap_unlock();
return new_addr;
}
static bool can_passthrough_madvise(abi_ulong start, abi_ulong end)
{
ulong addr;
if ((start | end) & ~qemu_host_page_mask) {
return false;
}
for (addr = start; addr < end; addr += TARGET_PAGE_SIZE) {
if (!(page_get_flags(addr) & PAGE_PASSTHROUGH)) {
return false;
}
}
return true;
}
abi_long target_madvise(abi_ulong start, abi_ulong len_in, int advice)
{
abi_ulong len, end;
int ret = 0;
if (start & ~TARGET_PAGE_MASK) {
return -TARGET_EINVAL;
}
len = TARGET_PAGE_ALIGN(len_in);
if (len_in && !len) {
return -TARGET_EINVAL;
}
end = start + len;
if (end < start) {
return -TARGET_EINVAL;
}
if (end == start) {
return 0;
}
if (!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.
* can_passthrough_madvise() helps to check if a passthrough is possible by
* comparing mappings that are known to have the same semantics in the host
* and the guest. In this case passthrough is safe.
*
* 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 (can_passthrough_madvise(start, end)) {
ret = get_errno(madvise(g2h_untagged(start), len, advice));
if ((advice == MADV_DONTNEED) && (ret == 0)) {
page_reset_target_data(start, start + len);
}
}
}
mmap_unlock();
return ret;
}
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