/*
* Copyright (C) 2008 The Android Open Source Project
*
* 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 "mem_map.h"
#include "thread-inl.h"
#include <inttypes.h>
#include <backtrace/BacktraceMap.h>
#include <memory>
// See CreateStartPos below.
#ifdef __BIONIC__
#include <sys/auxv.h>
#endif
#include "base/stringprintf.h"
#include "ScopedFd.h"
#include "utils.h"
#define USE_ASHMEM 1
#ifdef USE_ASHMEM
#include <cutils/ashmem.h>
#ifndef ANDROID_OS
#include <sys/resource.h>
#endif
#endif
#ifndef MAP_ANONYMOUS
#define MAP_ANONYMOUS MAP_ANON
#endif
namespace art {
static std::ostream& operator<<(
std::ostream& os,
std::pair<BacktraceMap::const_iterator, BacktraceMap::const_iterator> iters) {
for (BacktraceMap::const_iterator it = iters.first; it != iters.second; ++it) {
os << StringPrintf("0x%08x-0x%08x %c%c%c %s\n",
static_cast<uint32_t>(it->start),
static_cast<uint32_t>(it->end),
(it->flags & PROT_READ) ? 'r' : '-',
(it->flags & PROT_WRITE) ? 'w' : '-',
(it->flags & PROT_EXEC) ? 'x' : '-', it->name.c_str());
}
return os;
}
std::ostream& operator<<(std::ostream& os, const MemMap::Maps& mem_maps) {
os << "MemMap:" << std::endl;
for (auto it = mem_maps.begin(); it != mem_maps.end(); ++it) {
void* base = it->first;
MemMap* map = it->second;
CHECK_EQ(base, map->BaseBegin());
os << *map << std::endl;
}
return os;
}
MemMap::Maps* MemMap::maps_ = nullptr;
#if USE_ART_LOW_4G_ALLOCATOR
// Handling mem_map in 32b address range for 64b architectures that do not support MAP_32BIT.
// The regular start of memory allocations. The first 64KB is protected by SELinux.
static constexpr uintptr_t LOW_MEM_START = 64 * KB;
// Generate random starting position.
// To not interfere with image position, take the image's address and only place it below. Current
// formula (sketch):
//
// ART_BASE_ADDR = 0001XXXXXXXXXXXXXXX
// ----------------------------------------
// = 0000111111111111111
// & ~(kPageSize - 1) =~0000000000000001111
// ----------------------------------------
// mask = 0000111111111110000
// & random data = YYYYYYYYYYYYYYYYYYY
// -----------------------------------
// tmp = 0000YYYYYYYYYYY0000
// + LOW_MEM_START = 0000000000001000000
// --------------------------------------
// start
//
// getauxval as an entropy source is exposed in Bionic, but not in glibc before 2.16. When we
// do not have Bionic, simply start with LOW_MEM_START.
// Function is standalone so it can be tested somewhat in mem_map_test.cc.
#ifdef __BIONIC__
uintptr_t CreateStartPos(uint64_t input) {
CHECK_NE(0, ART_BASE_ADDRESS);
// Start with all bits below highest bit in ART_BASE_ADDRESS.
constexpr size_t leading_zeros = CLZ(static_cast<uint32_t>(ART_BASE_ADDRESS));
constexpr uintptr_t mask_ones = (1 << (31 - leading_zeros)) - 1;
// Lowest (usually 12) bits are not used, as aligned by page size.
constexpr uintptr_t mask = mask_ones & ~(kPageSize - 1);
// Mask input data.
return (input & mask) + LOW_MEM_START;
}
#endif
static uintptr_t GenerateNextMemPos() {
#ifdef __BIONIC__
uint8_t* random_data = reinterpret_cast<uint8_t*>(getauxval(AT_RANDOM));
// The lower 8B are taken for the stack guard. Use the upper 8B (with mask).
return CreateStartPos(*reinterpret_cast<uintptr_t*>(random_data + 8));
#else
// No auxv on host, see above.
return LOW_MEM_START;
#endif
}
// Initialize linear scan to random position.
uintptr_t MemMap::next_mem_pos_ = GenerateNextMemPos();
#endif
#if !defined(__APPLE__) // TODO: Reanable after b/16861075 BacktraceMap issue is addressed.
// Return true if the address range is contained in a single /proc/self/map entry.
static bool ContainedWithinExistingMap(uintptr_t begin,
uintptr_t end,
std::string* error_msg) {
std::unique_ptr<BacktraceMap> map(BacktraceMap::Create(getpid(), true));
if (map.get() == nullptr) {
*error_msg = StringPrintf("Failed to build process map");
return false;
}
for (BacktraceMap::const_iterator it = map->begin(); it != map->end(); ++it) {
if ((begin >= it->start && begin < it->end) // start of new within old
&& (end > it->start && end <= it->end)) { // end of new within old
return true;
}
}
std::string maps;
ReadFileToString("/proc/self/maps", &maps);
*error_msg = StringPrintf("Requested region 0x%08" PRIxPTR "-0x%08" PRIxPTR " does not overlap "
"any existing map:\n%s\n",
begin, end, maps.c_str());
return false;
}
#endif
// Return true if the address range does not conflict with any /proc/self/maps entry.
static bool CheckNonOverlapping(uintptr_t begin,
uintptr_t end,
std::string* error_msg) {
std::unique_ptr<BacktraceMap> map(BacktraceMap::Create(getpid(), true));
if (map.get() == nullptr) {
*error_msg = StringPrintf("Failed to build process map");
return false;
}
for (BacktraceMap::const_iterator it = map->begin(); it != map->end(); ++it) {
if ((begin >= it->start && begin < it->end) // start of new within old
|| (end > it->start && end < it->end) // end of new within old
|| (begin <= it->start && end > it->end)) { // start/end of new includes all of old
std::ostringstream map_info;
map_info << std::make_pair(it, map->end());
*error_msg = StringPrintf("Requested region 0x%08" PRIxPTR "-0x%08" PRIxPTR " overlaps with "
"existing map 0x%08" PRIxPTR "-0x%08" PRIxPTR " (%s)\n%s",
begin, end,
static_cast<uintptr_t>(it->start), static_cast<uintptr_t>(it->end),
it->name.c_str(),
map_info.str().c_str());
return false;
}
}
return true;
}
// CheckMapRequest to validate a non-MAP_FAILED mmap result based on
// the expected value, calling munmap if validation fails, giving the
// reason in error_msg.
//
// If the expected_ptr is nullptr, nothing is checked beyond the fact
// that the actual_ptr is not MAP_FAILED. However, if expected_ptr is
// non-null, we check that pointer is the actual_ptr == expected_ptr,
// and if not, report in error_msg what the conflict mapping was if
// found, or a generic error in other cases.
static bool CheckMapRequest(byte* expected_ptr, void* actual_ptr, size_t byte_count,
std::string* error_msg) {
// Handled first by caller for more specific error messages.
CHECK(actual_ptr != MAP_FAILED);
if (expected_ptr == nullptr) {
return true;
}
uintptr_t actual = reinterpret_cast<uintptr_t>(actual_ptr);
uintptr_t expected = reinterpret_cast<uintptr_t>(expected_ptr);
uintptr_t limit = expected + byte_count;
if (expected_ptr == actual_ptr) {
return true;
}
// We asked for an address but didn't get what we wanted, all paths below here should fail.
int result = munmap(actual_ptr, byte_count);
if (result == -1) {
PLOG(WARNING) << StringPrintf("munmap(%p, %zd) failed", actual_ptr, byte_count);
}
// We call this here so that we can try and generate a full error
// message with the overlapping mapping. There's no guarantee that
// that there will be an overlap though, since
// - The kernel is not *required* to honour expected_ptr unless MAP_FIXED is
// true, even if there is no overlap
// - There might have been an overlap at the point of mmap, but the
// overlapping region has since been unmapped.
std::string error_detail;
CheckNonOverlapping(expected, limit, &error_detail);
std::ostringstream os;
os << StringPrintf("Failed to mmap at expected address, mapped at "
"0x%08" PRIxPTR " instead of 0x%08" PRIxPTR,
actual, expected);
if (!error_detail.empty()) {
os << " : " << error_detail;
}
*error_msg = os.str();
return false;
}
MemMap* MemMap::MapAnonymous(const char* name, byte* expected_ptr, size_t byte_count, int prot,
bool low_4gb, std::string* error_msg) {
if (byte_count == 0) {
return new MemMap(name, nullptr, 0, nullptr, 0, prot, false);
}
size_t page_aligned_byte_count = RoundUp(byte_count, kPageSize);
int flags = MAP_PRIVATE | MAP_ANONYMOUS;
ScopedFd fd(-1);
#ifdef USE_ASHMEM
#ifdef HAVE_ANDROID_OS
const bool use_ashmem = true;
#else
// When not on Android ashmem is faked using files in /tmp. Ensure that such files won't
// fail due to ulimit restrictions. If they will then use a regular mmap.
struct rlimit rlimit_fsize;
CHECK_EQ(getrlimit(RLIMIT_FSIZE, &rlimit_fsize), 0);
const bool use_ashmem = (rlimit_fsize.rlim_cur == RLIM_INFINITY) ||
(page_aligned_byte_count < rlimit_fsize.rlim_cur);
#endif
if (use_ashmem) {
// android_os_Debug.cpp read_mapinfo assumes all ashmem regions associated with the VM are
// prefixed "dalvik-".
std::string debug_friendly_name("dalvik-");
debug_friendly_name += name;
fd.reset(ashmem_create_region(debug_friendly_name.c_str(), page_aligned_byte_count));
if (fd.get() == -1) {
*error_msg = StringPrintf("ashmem_create_region failed for '%s': %s", name, strerror(errno));
return nullptr;
}
flags = MAP_PRIVATE;
}
#endif
// We need to store and potentially set an error number for pretty printing of errors
int saved_errno = 0;
#ifdef __LP64__
// When requesting low_4g memory and having an expectation, the requested range should fit into
// 4GB.
if (low_4gb && (
// Start out of bounds.
(reinterpret_cast<uintptr_t>(expected_ptr) >> 32) != 0 ||
// End out of bounds. For simplicity, this will fail for the last page of memory.
(reinterpret_cast<uintptr_t>(expected_ptr + page_aligned_byte_count) >> 32) != 0)) {
*error_msg = StringPrintf("The requested address space (%p, %p) cannot fit in low_4gb",
expected_ptr, expected_ptr + page_aligned_byte_count);
return nullptr;
}
#endif
// TODO:
// A page allocator would be a useful abstraction here, as
// 1) It is doubtful that MAP_32BIT on x86_64 is doing the right job for us
// 2) The linear scheme, even with simple saving of the last known position, is very crude
#if USE_ART_LOW_4G_ALLOCATOR
// MAP_32BIT only available on x86_64.
void* actual = MAP_FAILED;
if (low_4gb && expected_ptr == nullptr) {
bool first_run = true;
for (uintptr_t ptr = next_mem_pos_; ptr < 4 * GB; ptr += kPageSize) {
if (4U * GB - ptr < page_aligned_byte_count) {
// Not enough memory until 4GB.
if (first_run) {
// Try another time from the bottom;
ptr = LOW_MEM_START - kPageSize;
first_run = false;
continue;
} else {
// Second try failed.
break;
}
}
uintptr_t tail_ptr;
// Check pages are free.
bool safe = true;
for (tail_ptr = ptr; tail_ptr < ptr + page_aligned_byte_count; tail_ptr += kPageSize) {
if (msync(reinterpret_cast<void*>(tail_ptr), kPageSize, 0) == 0) {
safe = false;
break;
} else {
DCHECK_EQ(errno, ENOMEM);
}
}
next_mem_pos_ = tail_ptr; // update early, as we break out when we found and mapped a region
if (safe == true) {
actual = mmap(reinterpret_cast<void*>(ptr), page_aligned_byte_count, prot, flags, fd.get(),
0);
if (actual != MAP_FAILED) {
// Since we didn't use MAP_FIXED the kernel may have mapped it somewhere not in the low
// 4GB. If this is the case, unmap and retry.
if (reinterpret_cast<uintptr_t>(actual) + page_aligned_byte_count < 4 * GB) {
break;
} else {
munmap(actual, page_aligned_byte_count);
actual = MAP_FAILED;
}
}
} else {
// Skip over last page.
ptr = tail_ptr;
}
}
if (actual == MAP_FAILED) {
LOG(ERROR) << "Could not find contiguous low-memory space.";
saved_errno = ENOMEM;
}
} else {
actual = mmap(expected_ptr, page_aligned_byte_count, prot, flags, fd.get(), 0);
saved_errno = errno;
}
#else
#if defined(__LP64__)
if (low_4gb && expected_ptr == nullptr) {
flags |= MAP_32BIT;
}
#endif
void* actual = mmap(expected_ptr, page_aligned_byte_count, prot, flags, fd.get(), 0);
saved_errno = errno;
#endif
if (actual == MAP_FAILED) {
std::string maps;
ReadFileToString("/proc/self/maps", &maps);
*error_msg = StringPrintf("Failed anonymous mmap(%p, %zd, 0x%x, 0x%x, %d, 0): %s\n%s",
expected_ptr, page_aligned_byte_count, prot, flags, fd.get(),
strerror(saved_errno), maps.c_str());
return nullptr;
}
std::ostringstream check_map_request_error_msg;
if (!CheckMapRequest(expected_ptr, actual, page_aligned_byte_count, error_msg)) {
return nullptr;
}
return new MemMap(name, reinterpret_cast<byte*>(actual), byte_count, actual,
page_aligned_byte_count, prot, false);
}
MemMap* MemMap::MapFileAtAddress(byte* expected_ptr, size_t byte_count, int prot, int flags, int fd,
off_t start, bool reuse, const char* filename,
std::string* error_msg) {
CHECK_NE(0, prot);
CHECK_NE(0, flags & (MAP_SHARED | MAP_PRIVATE));
// Note that we do not allow MAP_FIXED unless reuse == true, i.e we
// expect his mapping to be contained within an existing map.
if (reuse) {
// reuse means it is okay that it overlaps an existing page mapping.
// Only use this if you actually made the page reservation yourself.
CHECK(expected_ptr != nullptr);
#if !defined(__APPLE__) // TODO: Reanable after b/16861075 BacktraceMap issue is addressed.
uintptr_t expected = reinterpret_cast<uintptr_t>(expected_ptr);
uintptr_t limit = expected + byte_count;
DCHECK(ContainedWithinExistingMap(expected, limit, error_msg));
#endif
flags |= MAP_FIXED;
} else {
CHECK_EQ(0, flags & MAP_FIXED);
// Don't bother checking for an overlapping region here. We'll
// check this if required after the fact inside CheckMapRequest.
}
if (byte_count == 0) {
return new MemMap(filename, nullptr, 0, nullptr, 0, prot, false);
}
// Adjust 'offset' to be page-aligned as required by mmap.
int page_offset = start % kPageSize;
off_t page_aligned_offset = start - page_offset;
// Adjust 'byte_count' to be page-aligned as we will map this anyway.
size_t page_aligned_byte_count = RoundUp(byte_count + page_offset, kPageSize);
// The 'expected_ptr' is modified (if specified, ie non-null) to be page aligned to the file but
// not necessarily to virtual memory. mmap will page align 'expected' for us.
byte* page_aligned_expected = (expected_ptr == nullptr) ? nullptr : (expected_ptr - page_offset);
byte* actual = reinterpret_cast<byte*>(mmap(page_aligned_expected,
page_aligned_byte_count,
prot,
flags,
fd,
page_aligned_offset));
if (actual == MAP_FAILED) {
auto saved_errno = errno;
std::string maps;
ReadFileToString("/proc/self/maps", &maps);
*error_msg = StringPrintf("mmap(%p, %zd, 0x%x, 0x%x, %d, %" PRId64
") of file '%s' failed: %s\n%s",
page_aligned_expected, page_aligned_byte_count, prot, flags, fd,
static_cast<int64_t>(page_aligned_offset), filename,
strerror(saved_errno), maps.c_str());
return nullptr;
}
std::ostringstream check_map_request_error_msg;
if (!CheckMapRequest(expected_ptr, actual, page_aligned_byte_count, error_msg)) {
return nullptr;
}
return new MemMap(filename, actual + page_offset, byte_count, actual, page_aligned_byte_count,
prot, reuse);
}
MemMap::~MemMap() {
if (base_begin_ == nullptr && base_size_ == 0) {
return;
}
if (!reuse_) {
int result = munmap(base_begin_, base_size_);
if (result == -1) {
PLOG(FATAL) << "munmap failed";
}
}
// Remove it from maps_.
MutexLock mu(Thread::Current(), *Locks::mem_maps_lock_);
bool found = false;
DCHECK(maps_ != nullptr);
for (auto it = maps_->lower_bound(base_begin_), end = maps_->end();
it != end && it->first == base_begin_; ++it) {
if (it->second == this) {
found = true;
maps_->erase(it);
break;
}
}
CHECK(found) << "MemMap not found";
}
MemMap::MemMap(const std::string& name, byte* begin, size_t size, void* base_begin,
size_t base_size, int prot, bool reuse)
: name_(name), begin_(begin), size_(size), base_begin_(base_begin), base_size_(base_size),
prot_(prot), reuse_(reuse) {
if (size_ == 0) {
CHECK(begin_ == nullptr);
CHECK(base_begin_ == nullptr);
CHECK_EQ(base_size_, 0U);
} else {
CHECK(begin_ != nullptr);
CHECK(base_begin_ != nullptr);
CHECK_NE(base_size_, 0U);
// Add it to maps_.
MutexLock mu(Thread::Current(), *Locks::mem_maps_lock_);
DCHECK(maps_ != nullptr);
maps_->insert(std::make_pair(base_begin_, this));
}
};
MemMap* MemMap::RemapAtEnd(byte* new_end, const char* tail_name, int tail_prot,
std::string* error_msg) {
DCHECK_GE(new_end, Begin());
DCHECK_LE(new_end, End());
DCHECK_LE(begin_ + size_, reinterpret_cast<byte*>(base_begin_) + base_size_);
DCHECK(IsAligned<kPageSize>(begin_));
DCHECK(IsAligned<kPageSize>(base_begin_));
DCHECK(IsAligned<kPageSize>(reinterpret_cast<byte*>(base_begin_) + base_size_));
DCHECK(IsAligned<kPageSize>(new_end));
byte* old_end = begin_ + size_;
byte* old_base_end = reinterpret_cast<byte*>(base_begin_) + base_size_;
byte* new_base_end = new_end;
DCHECK_LE(new_base_end, old_base_end);
if (new_base_end == old_base_end) {
return new MemMap(tail_name, nullptr, 0, nullptr, 0, tail_prot, false);
}
size_ = new_end - reinterpret_cast<byte*>(begin_);
base_size_ = new_base_end - reinterpret_cast<byte*>(base_begin_);
DCHECK_LE(begin_ + size_, reinterpret_cast<byte*>(base_begin_) + base_size_);
size_t tail_size = old_end - new_end;
byte* tail_base_begin = new_base_end;
size_t tail_base_size = old_base_end - new_base_end;
DCHECK_EQ(tail_base_begin + tail_base_size, old_base_end);
DCHECK(IsAligned<kPageSize>(tail_base_size));
#ifdef USE_ASHMEM
// android_os_Debug.cpp read_mapinfo assumes all ashmem regions associated with the VM are
// prefixed "dalvik-".
std::string debug_friendly_name("dalvik-");
debug_friendly_name += tail_name;
ScopedFd fd(ashmem_create_region(debug_friendly_name.c_str(), tail_base_size));
int flags = MAP_PRIVATE | MAP_FIXED;
if (fd.get() == -1) {
*error_msg = StringPrintf("ashmem_create_region failed for '%s': %s",
tail_name, strerror(errno));
return nullptr;
}
#else
ScopedFd fd(-1);
int flags = MAP_PRIVATE | MAP_ANONYMOUS;
#endif
// Unmap/map the tail region.
int result = munmap(tail_base_begin, tail_base_size);
if (result == -1) {
std::string maps;
ReadFileToString("/proc/self/maps", &maps);
*error_msg = StringPrintf("munmap(%p, %zd) failed for '%s'\n%s",
tail_base_begin, tail_base_size, name_.c_str(),
maps.c_str());
return nullptr;
}
// Don't cause memory allocation between the munmap and the mmap
// calls. Otherwise, libc (or something else) might take this memory
// region. Note this isn't perfect as there's no way to prevent
// other threads to try to take this memory region here.
byte* actual = reinterpret_cast<byte*>(mmap(tail_base_begin, tail_base_size, tail_prot,
flags, fd.get(), 0));
if (actual == MAP_FAILED) {
std::string maps;
ReadFileToString("/proc/self/maps", &maps);
*error_msg = StringPrintf("anonymous mmap(%p, %zd, 0x%x, 0x%x, %d, 0) failed\n%s",
tail_base_begin, tail_base_size, tail_prot, flags, fd.get(),
maps.c_str());
return nullptr;
}
return new MemMap(tail_name, actual, tail_size, actual, tail_base_size, tail_prot, false);
}
void MemMap::MadviseDontNeedAndZero() {
if (base_begin_ != nullptr || base_size_ != 0) {
if (!kMadviseZeroes) {
memset(base_begin_, 0, base_size_);
}
int result = madvise(base_begin_, base_size_, MADV_DONTNEED);
if (result == -1) {
PLOG(WARNING) << "madvise failed";
}
}
}
bool MemMap::Protect(int prot) {
if (base_begin_ == nullptr && base_size_ == 0) {
prot_ = prot;
return true;
}
if (mprotect(base_begin_, base_size_, prot) == 0) {
prot_ = prot;
return true;
}
PLOG(ERROR) << "mprotect(" << reinterpret_cast<void*>(base_begin_) << ", " << base_size_ << ", "
<< prot << ") failed";
return false;
}
bool MemMap::CheckNoGaps(MemMap* begin_map, MemMap* end_map) {
MutexLock mu(Thread::Current(), *Locks::mem_maps_lock_);
CHECK(begin_map != nullptr);
CHECK(end_map != nullptr);
CHECK(HasMemMap(begin_map));
CHECK(HasMemMap(end_map));
CHECK_LE(begin_map->BaseBegin(), end_map->BaseBegin());
MemMap* map = begin_map;
while (map->BaseBegin() != end_map->BaseBegin()) {
MemMap* next_map = GetLargestMemMapAt(map->BaseEnd());
if (next_map == nullptr) {
// Found a gap.
return false;
}
map = next_map;
}
return true;
}
void MemMap::DumpMaps(std::ostream& os) {
MutexLock mu(Thread::Current(), *Locks::mem_maps_lock_);
DumpMapsLocked(os);
}
void MemMap::DumpMapsLocked(std::ostream& os) {
os << maps_;
}
bool MemMap::HasMemMap(MemMap* map) {
void* base_begin = map->BaseBegin();
for (auto it = maps_->lower_bound(base_begin), end = maps_->end();
it != end && it->first == base_begin; ++it) {
if (it->second == map) {
return true;
}
}
return false;
}
MemMap* MemMap::GetLargestMemMapAt(void* address) {
size_t largest_size = 0;
MemMap* largest_map = nullptr;
DCHECK(maps_ != nullptr);
for (auto it = maps_->lower_bound(address), end = maps_->end();
it != end && it->first == address; ++it) {
MemMap* map = it->second;
CHECK(map != nullptr);
if (largest_size < map->BaseSize()) {
largest_size = map->BaseSize();
largest_map = map;
}
}
return largest_map;
}
void MemMap::Init() {
MutexLock mu(Thread::Current(), *Locks::mem_maps_lock_);
if (maps_ == nullptr) {
// dex2oat calls MemMap::Init twice since its needed before the runtime is created.
maps_ = new Maps;
}
}
void MemMap::Shutdown() {
MutexLock mu(Thread::Current(), *Locks::mem_maps_lock_);
delete maps_;
maps_ = nullptr;
}
std::ostream& operator<<(std::ostream& os, const MemMap& mem_map) {
os << StringPrintf("[MemMap: %p-%p prot=0x%x %s]",
mem_map.BaseBegin(), mem_map.BaseEnd(), mem_map.GetProtect(),
mem_map.GetName().c_str());
return os;
}
} // namespace art