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// Copyright (c) 2021, 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 "platform/globals.h"
#if defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_LINUX) || \
defined(DART_HOST_OS_MACOS)
#include "bin/virtual_memory.h"
#include <errno.h>
#include <sys/mman.h>
#include <unistd.h>
#if defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_LINUX)
#include <sys/prctl.h>
#endif
#include "platform/assert.h"
#include "platform/utils.h"
namespace dart {
namespace bin {
// 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)
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;
}
VirtualMemory* VirtualMemory::Allocate(intptr_t size,
bool is_executable,
const char* name) {
ASSERT(Utils::IsAligned(size, PageSize()));
const int prot = PROT_READ | PROT_WRITE | (is_executable ? PROT_EXEC : 0);
int map_flags = MAP_PRIVATE | MAP_ANONYMOUS;
#if (defined(DART_HOST_OS_MACOS) && !defined(DART_HOST_OS_IOS))
if (is_executable && IsAtLeastOS10_14()) {
map_flags |= MAP_JIT;
}
#endif // defined(DART_HOST_OS_MACOS)
// Some 64-bit microarchitectures store only the low 32-bits of targets as
// part of indirect branch prediction, predicting that the target's upper bits
// will be same as the call instruction's address. This leads to misprediction
// for indirect calls crossing a 4GB boundary. We ask mmap to place our
// generated code near the VM binary to avoid this.
void* hint = is_executable ? reinterpret_cast<void*>(&Allocate) : nullptr;
void* address = mmap(hint, size, prot, map_flags, -1, 0);
#if defined(DART_HOST_OS_LINUX)
// On WSL 1 trying to allocate memory close to the binary by supplying a hint
// fails with ENOMEM for unclear reason. Some reports suggest that this might
// be related to the alignment of the hint but aligning it by 64Kb does not
// make the issue go away in our experiments. Instead just retry without any
// hint.
if (address == MAP_FAILED && hint != nullptr &&
Utils::IsWindowsSubsystemForLinux()) {
address = mmap(nullptr, size, prot, map_flags, -1, 0);
}
#endif
if (address == MAP_FAILED) {
return nullptr;
}
#if defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_LINUX)
// PR_SET_VMA was only added to mainline Linux in 5.17, and some versions of
// the Android NDK have incorrect headers, so we manually define it if absent.
#if !defined(PR_SET_VMA)
#define PR_SET_VMA 0x53564d41
#endif
#if !defined(PR_SET_VMA_ANON_NAME)
#define PR_SET_VMA_ANON_NAME 0
#endif
prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, address, size, name);
#endif
return new VirtualMemory(address, size);
}
VirtualMemory::~VirtualMemory() {
if (address_ != nullptr) {
if (munmap(address_, size_) != 0) {
int error = errno;
const int kBufferSize = 1024;
char error_buf[kBufferSize];
FATAL("munmap error: %d (%s)", error,
Utils::StrError(error, error_buf, kBufferSize));
}
}
}
void VirtualMemory::Protect(void* address, intptr_t size, Protection mode) {
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];
FATAL("mprotect error: %d (%s)", error,
Utils::StrError(error, error_buf, kBufferSize));
}
}
} // namespace bin
} // namespace dart
#endif // defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_LINUX) || \
// defined(DART_HOST_OS_MACOS)