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// Copyright 2022 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_COMMON_CODE_MEMORY_ACCESS_INL_H_
#define V8_COMMON_CODE_MEMORY_ACCESS_INL_H_
#include "src/common/code-memory-access.h"
#include "src/flags/flags.h"
#if V8_HAS_PKU_JIT_WRITE_PROTECT
#include "src/base/platform/memory-protection-key.h"
#endif
#if V8_HAS_PTHREAD_JIT_WRITE_PROTECT
#include "src/base/platform/platform.h"
#endif
namespace v8 {
namespace internal {
RwxMemoryWriteScope::RwxMemoryWriteScope(const char* comment) {
if (!v8_flags.jitless) {
SetWritable();
}
}
RwxMemoryWriteScope::~RwxMemoryWriteScope() {
if (!v8_flags.jitless) {
SetExecutable();
}
}
ThreadIsolation::WritableJitAllocation::WritableJitAllocation(
Address addr, size_t size, JitAllocationType type,
JitAllocationSource source)
: address_(addr),
// The order of these is important. We need to create the write scope
// before we lookup the Jit page, since the latter will take a mutex in
// protected memory.
write_scope_("WritableJitAllocation"),
page_ref_(ThreadIsolation::LookupJitPage(addr, size)),
allocation_(source == JitAllocationSource::kRegister
? page_ref_.RegisterAllocation(addr, size, type)
: page_ref_.LookupAllocation(addr, size, type)) {}
template <typename T, size_t offset>
void ThreadIsolation::WritableJitAllocation::WriteHeaderSlot(T value) {
// These asserts are no strict requirements, they just guard against
// non-implemented functionality.
static_assert(!std::is_convertible_v<T, Object>);
static_assert(offset != HeapObject::kMapOffset);
WriteMaybeUnalignedValue<T>(address_ + offset, value);
}
template <typename T, size_t offset>
void ThreadIsolation::WritableJitAllocation::WriteHeaderSlot(T value,
ReleaseStoreTag) {
// These asserts are no strict requirements, they just guard against
// non-implemented functionality.
static_assert(std::is_convertible_v<T, Object>);
static_assert(offset != HeapObject::kMapOffset);
TaggedField<T, offset>::Release_Store(HeapObject::FromAddress(address_),
value);
}
template <typename T, size_t offset>
void ThreadIsolation::WritableJitAllocation::WriteHeaderSlot(T value,
RelaxedStoreTag) {
// These asserts are no strict requirements, they just guard against
// non-implemented functionality.
static_assert(std::is_convertible_v<T, Object>);
if constexpr (offset == HeapObject::kMapOffset) {
TaggedField<T, offset>::Relaxed_Store_Map_Word(
HeapObject::FromAddress(address_), value);
} else {
TaggedField<T, offset>::Relaxed_Store(HeapObject::FromAddress(address_),
value);
}
}
void ThreadIsolation::WritableJitAllocation::CopyCode(size_t dst_offset,
const uint8_t* src,
size_t num_bytes) {
CopyBytes(reinterpret_cast<uint8_t*>(address_ + dst_offset), src, num_bytes);
}
void ThreadIsolation::WritableJitAllocation::CopyData(size_t dst_offset,
const uint8_t* src,
size_t num_bytes) {
CopyBytes(reinterpret_cast<uint8_t*>(address_ + dst_offset), src, num_bytes);
}
void ThreadIsolation::WritableJitAllocation::ClearBytes(size_t offset,
size_t len) {
memset(reinterpret_cast<void*>(address_ + offset), 0, len);
}
#if V8_HAS_PTHREAD_JIT_WRITE_PROTECT
// static
bool RwxMemoryWriteScope::IsSupported() { return true; }
// static
bool RwxMemoryWriteScope::IsSupportedUntrusted() { return true; }
// static
void RwxMemoryWriteScope::SetWritable() {
if (code_space_write_nesting_level_ == 0) {
base::SetJitWriteProtected(0);
}
code_space_write_nesting_level_++;
}
// static
void RwxMemoryWriteScope::SetExecutable() {
code_space_write_nesting_level_--;
if (code_space_write_nesting_level_ == 0) {
base::SetJitWriteProtected(1);
}
}
#elif V8_HAS_PKU_JIT_WRITE_PROTECT
// static
bool RwxMemoryWriteScope::IsSupported() {
static_assert(base::MemoryProtectionKey::kNoMemoryProtectionKey == -1);
DCHECK(ThreadIsolation::initialized());
// TODO(sroettger): can we check this at initialization time instead? The
// tests won't be able to run with/without pkey support anymore in the same
// process.
return v8_flags.memory_protection_keys && ThreadIsolation::pkey() >= 0;
}
// static
bool RwxMemoryWriteScope::IsSupportedUntrusted() {
DCHECK(ThreadIsolation::initialized());
return v8_flags.memory_protection_keys &&
ThreadIsolation::untrusted_pkey() >= 0;
}
// static
void RwxMemoryWriteScope::SetWritable() {
DCHECK(ThreadIsolation::initialized());
if (!IsSupported()) return;
if (code_space_write_nesting_level_ == 0) {
DCHECK_NE(
base::MemoryProtectionKey::GetKeyPermission(ThreadIsolation::pkey()),
base::MemoryProtectionKey::kNoRestrictions);
base::MemoryProtectionKey::SetPermissionsForKey(
ThreadIsolation::pkey(), base::MemoryProtectionKey::kNoRestrictions);
}
code_space_write_nesting_level_++;
}
// static
void RwxMemoryWriteScope::SetExecutable() {
DCHECK(ThreadIsolation::initialized());
if (!IsSupported()) return;
code_space_write_nesting_level_--;
if (code_space_write_nesting_level_ == 0) {
DCHECK_EQ(
base::MemoryProtectionKey::GetKeyPermission(ThreadIsolation::pkey()),
base::MemoryProtectionKey::kNoRestrictions);
base::MemoryProtectionKey::SetPermissionsForKey(
ThreadIsolation::pkey(), base::MemoryProtectionKey::kDisableWrite);
}
}
#else // !V8_HAS_PTHREAD_JIT_WRITE_PROTECT && !V8_TRY_USE_PKU_JIT_WRITE_PROTECT
// static
bool RwxMemoryWriteScope::IsSupported() { return false; }
// static
bool RwxMemoryWriteScope::IsSupportedUntrusted() { return false; }
// static
void RwxMemoryWriteScope::SetWritable() {}
// static
void RwxMemoryWriteScope::SetExecutable() {}
#endif // V8_HAS_PTHREAD_JIT_WRITE_PROTECT
} // namespace internal
} // namespace v8
#endif // V8_COMMON_CODE_MEMORY_ACCESS_INL_H_
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