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// Copyright 2017 The Crashpad Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <sys/mman.h>
#include <dlfcn.h>
#include <errno.h>
#include <stdint.h>
#include <unistd.h>
#include "dlfcn_internal.h"
#if defined(__USE_FILE_OFFSET64) && __ANDROID_API__ < 21
// Bionic has provided a wrapper for __mmap2() since the beginning of time. See
// bionic/libc/SYSCALLS.TXT in any Android version.
extern "C" void* __mmap2(void* addr,
size_t size,
int prot,
int flags,
int fd,
size_t pgoff);
namespace {
template <typename T>
T Align(T value, size_t alignment) {
return (value + alignment - 1) & ~(alignment - 1);
}
// Adapted from Android 8.0.0 bionic/libc/bionic/mmap.cpp.
void* LocalMmap64(void* addr,
size_t size,
int prot,
int flags,
int fd,
off64_t offset) {
constexpr int kMmap2Shift = 12;
if (offset < 0 || (offset & ((1UL << kMmap2Shift) - 1)) != 0) {
errno = EINVAL;
return MAP_FAILED;
}
const size_t rounded = Align(size, getpagesize());
if (rounded < size || rounded > PTRDIFF_MAX) {
errno = ENOMEM;
return MAP_FAILED;
}
const bool is_private_anonymous =
(flags & (MAP_PRIVATE | MAP_ANONYMOUS)) == (MAP_PRIVATE | MAP_ANONYMOUS);
const bool is_stack_or_grows_down =
(flags & (MAP_STACK | MAP_GROWSDOWN)) != 0;
void* const result =
__mmap2(addr, size, prot, flags, fd, offset >> kMmap2Shift);
static bool kernel_has_MADV_MERGEABLE = true;
if (result != MAP_FAILED && kernel_has_MADV_MERGEABLE &&
is_private_anonymous && !is_stack_or_grows_down) {
const int saved_errno = errno;
const int rc = madvise(result, size, MADV_MERGEABLE);
if (rc == -1 && errno == EINVAL) {
kernel_has_MADV_MERGEABLE = false;
}
errno = saved_errno;
}
return result;
}
} // namespace
extern "C" {
void* mmap(void* addr, size_t size, int prot, int flags, int fd, off_t offset) {
// Use the system’s mmap64() wrapper if available. It will be available on
// Android 5.0 (“Lollipop”) and later.
using Mmap64Type = void* (*)(void*, size_t, int, int, int, off64_t);
static const Mmap64Type mmap64 = reinterpret_cast<Mmap64Type>(
crashpad::internal::Dlsym(RTLD_DEFAULT, "mmap64"));
if (mmap64) {
return mmap64(addr, size, prot, flags, fd, offset);
}
// Otherwise, use the local implementation, which should amount to exactly the
// same thing.
return LocalMmap64(addr, size, prot, flags, fd, offset);
}
} // extern "C"
#endif // defined(__USE_FILE_OFFSET64) && __ANDROID_API__ < 21