blob: 7010b264f192b962de4a62ce04fd6d418bfffa37 [file] [log] [blame]
// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
#include "vm/globals.h"
#if defined(HOST_OS_ANDROID) || defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS)
#include "vm/virtual_memory.h"
#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <unistd.h>
#include "platform/assert.h"
#include "platform/utils.h"
#include "vm/isolate.h"
// #define VIRTUAL_MEMORY_LOGGING 1
#if defined(VIRTUAL_MEMORY_LOGGING)
#define LOG_INFO(msg, ...) OS::PrintErr(msg, ##__VA_ARGS__)
#else
#define LOG_INFO(msg, ...)
#endif // defined(VIRTUAL_MEMORY_LOGGING)
namespace dart {
// standard MAP_FAILED causes "error: use of old-style cast" as it
// defines MAP_FAILED as ((void *) -1)
#undef MAP_FAILED
#define MAP_FAILED reinterpret_cast<void*>(-1)
DECLARE_FLAG(bool, dual_map_code);
DECLARE_FLAG(bool, write_protect_code);
#if defined(TARGET_OS_LINUX)
DECLARE_FLAG(bool, generate_perf_events_symbols);
DECLARE_FLAG(bool, generate_perf_jitdump);
#endif
uword VirtualMemory::page_size_ = 0;
intptr_t VirtualMemory::CalculatePageSize() {
const intptr_t page_size = getpagesize();
ASSERT(page_size != 0);
ASSERT(Utils::IsPowerOfTwo(page_size));
return page_size;
}
void VirtualMemory::Init() {
if (page_size_ != 0) {
// Already initialized.
return;
}
page_size_ = CalculatePageSize();
#if defined(DUAL_MAPPING_SUPPORTED)
// Perf is Linux-specific and the flags aren't defined in Product.
#if defined(TARGET_OS_LINUX) && !defined(PRODUCT)
// Perf interacts strangely with memfds, leading it to sometimes collect
// garbled return addresses.
if (FLAG_generate_perf_events_symbols || FLAG_generate_perf_jitdump) {
LOG_INFO(
"Dual code mapping disabled to generate perf events or jitdump.\n");
FLAG_dual_map_code = false;
return;
}
#endif
// Detect dual mapping exec permission limitation on some platforms,
// such as on docker containers, and disable dual mapping in this case.
// Also detect for missing support of memfd_create syscall.
if (FLAG_dual_map_code) {
intptr_t size = PageSize();
intptr_t alignment = 256 * 1024; // e.g. heap page size.
VirtualMemory* vm = AllocateAligned(size, alignment, true, "memfd-test");
if (vm == NULL) {
LOG_INFO("memfd_create not supported; disabling dual mapping of code.\n");
FLAG_dual_map_code = false;
return;
}
void* region = reinterpret_cast<void*>(vm->region_.start());
void* alias = reinterpret_cast<void*>(vm->alias_.start());
if (region == alias ||
mprotect(region, size, PROT_READ) != 0 || // Remove PROT_WRITE.
mprotect(alias, size, PROT_READ | PROT_EXEC) != 0) { // Add PROT_EXEC.
LOG_INFO("mprotect fails; disabling dual mapping of code.\n");
FLAG_dual_map_code = false;
}
delete vm;
}
#endif // defined(DUAL_MAPPING_SUPPORTED)
}
bool VirtualMemory::DualMappingEnabled() {
return FLAG_dual_map_code;
}
static void unmap(uword start, uword end) {
ASSERT(start <= end);
uword size = end - start;
if (size == 0) {
return;
}
if (munmap(reinterpret_cast<void*>(start), size) != 0) {
int error = errno;
const int kBufferSize = 1024;
char error_buf[kBufferSize];
FATAL2("munmap error: %d (%s)", error,
Utils::StrError(error, error_buf, kBufferSize));
}
}
#if defined(DUAL_MAPPING_SUPPORTED)
// Do not leak file descriptors to child processes.
#if !defined(MFD_CLOEXEC)
#define MFD_CLOEXEC 0x0001U
#endif
// Wrapper to call memfd_create syscall.
static inline int memfd_create(const char* name, unsigned int flags) {
#if !defined(__NR_memfd_create)
errno = ENOSYS;
return -1;
#else
return syscall(__NR_memfd_create, name, flags);
#endif
}
static void* MapAligned(int fd,
int prot,
intptr_t size,
intptr_t alignment,
intptr_t allocated_size) {
void* address =
mmap(NULL, allocated_size, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
LOG_INFO("mmap(NULL, 0x%" Px ", PROT_NONE, ...): %p\n", allocated_size,
address);
if (address == MAP_FAILED) {
return NULL;
}
const uword base = reinterpret_cast<uword>(address);
const uword aligned_base = Utils::RoundUp(base, alignment);
// Guarantee the alignment by mapping at a fixed address inside the above
// mapping. Overlapping region will be automatically discarded in the above
// mapping. Manually discard non-overlapping regions.
address = mmap(reinterpret_cast<void*>(aligned_base), size, prot,
MAP_SHARED | MAP_FIXED, fd, 0);
LOG_INFO("mmap(0x%" Px ", 0x%" Px ", %u, ...): %p\n", aligned_base, size,
prot, address);
if (address == MAP_FAILED) {
unmap(base, base + allocated_size);
return NULL;
}
ASSERT(address == reinterpret_cast<void*>(aligned_base));
unmap(base, aligned_base);
unmap(aligned_base + size, base + allocated_size);
return address;
}
#endif // defined(DUAL_MAPPING_SUPPORTED)
VirtualMemory* VirtualMemory::AllocateAligned(intptr_t size,
intptr_t alignment,
bool is_executable,
const char* name) {
// When FLAG_write_protect_code is active, code memory (indicated by
// is_executable = true) is allocated as non-executable and later
// changed to executable via VirtualMemory::Protect.
//
// If FLAG_dual_map_code is active, the executable mapping will be mapped RX
// immediately and never changes protection until it is eventually unmapped.
ASSERT(Utils::IsAligned(size, PageSize()));
ASSERT(Utils::IsPowerOfTwo(alignment));
ASSERT(Utils::IsAligned(alignment, PageSize()));
ASSERT(name != nullptr);
const intptr_t allocated_size = size + alignment - PageSize();
#if defined(DUAL_MAPPING_SUPPORTED)
const bool dual_mapping =
is_executable && FLAG_write_protect_code && FLAG_dual_map_code;
if (dual_mapping) {
int fd = memfd_create(name, MFD_CLOEXEC);
if (fd == -1) {
return NULL;
}
if (ftruncate(fd, size) == -1) {
close(fd);
return NULL;
}
const int region_prot = PROT_READ | PROT_WRITE;
void* region_ptr =
MapAligned(fd, region_prot, size, alignment, allocated_size);
if (region_ptr == NULL) {
close(fd);
return NULL;
}
// The mapping will be RX and stays that way until it will eventually be
// unmapped.
MemoryRegion region(region_ptr, size);
// DUAL_MAPPING_SUPPORTED is false in TARGET_OS_MACOS and hence support
// for MAP_JIT is not required here.
const int alias_prot = PROT_READ | PROT_EXEC;
void* alias_ptr =
MapAligned(fd, alias_prot, size, alignment, allocated_size);
close(fd);
if (alias_ptr == NULL) {
const uword region_base = reinterpret_cast<uword>(region_ptr);
unmap(region_base, region_base + size);
return NULL;
}
ASSERT(region_ptr != alias_ptr);
MemoryRegion alias(alias_ptr, size);
return new VirtualMemory(region, alias, region);
}
#endif // defined(DUAL_MAPPING_SUPPORTED)
const int prot =
PROT_READ | PROT_WRITE |
((is_executable && !FLAG_write_protect_code) ? PROT_EXEC : 0);
#if defined(DUAL_MAPPING_SUPPORTED)
// Try to use memfd for single-mapped regions too, so they will have an
// associated name for memory attribution. Skip if FLAG_dual_map_code is
// false, which happens if we detected memfd wasn't working in Init above.
if (FLAG_dual_map_code) {
int fd = memfd_create(name, MFD_CLOEXEC);
if (fd == -1) {
return NULL;
}
if (ftruncate(fd, size) == -1) {
close(fd);
return NULL;
}
void* region_ptr = MapAligned(fd, prot, size, alignment, allocated_size);
close(fd);
if (region_ptr == NULL) {
return NULL;
}
MemoryRegion region(region_ptr, size);
return new VirtualMemory(region, region);
}
#endif
int map_flags = MAP_PRIVATE | MAP_ANONYMOUS;
#if (defined(HOST_OS_MACOS) && !defined(HOST_OS_IOS))
if (is_executable && IsAtLeastOS10_14()) {
map_flags |= MAP_JIT;
}
#endif // defined(HOST_OS_MACOS)
void* address = mmap(NULL, allocated_size, prot, map_flags, -1, 0);
LOG_INFO("mmap(NULL, 0x%" Px ", %u, ...): %p\n", allocated_size, prot,
address);
if (address == MAP_FAILED) {
return NULL;
}
const uword base = reinterpret_cast<uword>(address);
const uword aligned_base = Utils::RoundUp(base, alignment);
unmap(base, aligned_base);
unmap(aligned_base + size, base + allocated_size);
MemoryRegion region(reinterpret_cast<void*>(aligned_base), size);
return new VirtualMemory(region, region);
}
VirtualMemory::~VirtualMemory() {
if (vm_owns_region()) {
unmap(reserved_.start(), reserved_.end());
const intptr_t alias_offset = AliasOffset();
if (alias_offset != 0) {
unmap(reserved_.start() + alias_offset, reserved_.end() + alias_offset);
}
}
}
void VirtualMemory::FreeSubSegment(void* address,
intptr_t size) {
const uword start = reinterpret_cast<uword>(address);
unmap(start, start + size);
}
void VirtualMemory::Protect(void* address, intptr_t size, Protection mode) {
#if defined(DEBUG)
Thread* thread = Thread::Current();
ASSERT(thread == nullptr || thread->IsMutatorThread() ||
thread->isolate() == nullptr ||
thread->isolate()->mutator_thread()->IsAtSafepoint());
#endif
uword start_address = reinterpret_cast<uword>(address);
uword end_address = start_address + size;
uword page_address = Utils::RoundDown(start_address, PageSize());
int prot = 0;
switch (mode) {
case kNoAccess:
prot = PROT_NONE;
break;
case kReadOnly:
prot = PROT_READ;
break;
case kReadWrite:
prot = PROT_READ | PROT_WRITE;
break;
case kReadExecute:
prot = PROT_READ | PROT_EXEC;
break;
case kReadWriteExecute:
prot = PROT_READ | PROT_WRITE | PROT_EXEC;
break;
}
if (mprotect(reinterpret_cast<void*>(page_address),
end_address - page_address, prot) != 0) {
int error = errno;
const int kBufferSize = 1024;
char error_buf[kBufferSize];
LOG_INFO("mprotect(0x%" Px ", 0x%" Px ", %u) failed\n", page_address,
end_address - page_address, prot);
FATAL2("mprotect error: %d (%s)", error,
Utils::StrError(error, error_buf, kBufferSize));
}
LOG_INFO("mprotect(0x%" Px ", 0x%" Px ", %u) ok\n", page_address,
end_address - page_address, prot);
}
} // namespace dart
#endif // defined(HOST_OS_ANDROID ... HOST_OS_LINUX ... HOST_OS_MACOS)