Revert "Make the JIT zygote memory shared."
This reverts commit 05f87217ddc9b4b9186710c0135b918f456c5aef.
Bug: 119800099
Bug: 136110523
Reason for revert: testWebview flaking
Change-Id: I96afa6bc9c56c4aaf5ed72ae370f6f69c096c559
diff --git a/compiler/optimizing/inliner.cc b/compiler/optimizing/inliner.cc
index 1515575..9ef5ec3 100644
--- a/compiler/optimizing/inliner.cc
+++ b/compiler/optimizing/inliner.cc
@@ -1814,8 +1814,7 @@
callee_dead_reference_safe,
graph_->IsDebuggable(),
/* osr= */ false,
- /* is_shared_jit_code= */ graph_->IsCompilingForSharedJitCode(),
- /* start_instruction_id= */ caller_instruction_counter);
+ caller_instruction_counter);
callee_graph->SetArtMethod(resolved_method);
// When they are needed, allocate `inline_stats_` on the Arena instead
diff --git a/compiler/optimizing/instruction_builder.cc b/compiler/optimizing/instruction_builder.cc
index f8f813e..5e7b575 100644
--- a/compiler/optimizing/instruction_builder.cc
+++ b/compiler/optimizing/instruction_builder.cc
@@ -29,7 +29,6 @@
#include "driver/dex_compilation_unit.h"
#include "driver/compiler_options.h"
#include "imtable-inl.h"
-#include "jit/jit.h"
#include "mirror/dex_cache.h"
#include "oat_file.h"
#include "optimizing_compiler_stats.h"
@@ -1291,20 +1290,15 @@
// Check if the class will be initialized at runtime.
if (cls->IsInitialized()) {
Runtime* runtime = Runtime::Current();
- if (runtime->IsAotCompiler()) {
- // Assume loaded only if klass is in the boot image. App classes cannot be assumed
- // loaded because we don't even know what class loader will be used to load them.
- if (IsInBootImage(cls.Get(), code_generator_->GetCompilerOptions())) {
- return true;
- }
- } else {
+ if (!runtime->IsAotCompiler()) {
DCHECK(runtime->UseJitCompilation());
- if (Runtime::Current()->GetJit()->CanAssumeInitialized(
- cls.Get(),
- graph_->IsCompilingForSharedJitCode())) {
- // For JIT, the class cannot revert to an uninitialized state.
- return true;
- }
+ // For JIT, the class cannot revert to an uninitialized state.
+ return true;
+ }
+ // Assume loaded only if klass is in the boot image. App classes cannot be assumed
+ // loaded because we don't even know what class loader will be used to load them.
+ if (IsInBootImage(cls.Get(), code_generator_->GetCompilerOptions())) {
+ return true;
}
}
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index 759a8e6..8ac33a4 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -320,7 +320,6 @@
bool dead_reference_safe = false,
bool debuggable = false,
bool osr = false,
- bool is_shared_jit_code = false,
int start_instruction_id = 0)
: allocator_(allocator),
arena_stack_(arena_stack),
@@ -356,8 +355,7 @@
art_method_(nullptr),
inexact_object_rti_(ReferenceTypeInfo::CreateInvalid()),
osr_(osr),
- cha_single_implementation_list_(allocator->Adapter(kArenaAllocCHA)),
- is_shared_jit_code_(is_shared_jit_code) {
+ cha_single_implementation_list_(allocator->Adapter(kArenaAllocCHA)) {
blocks_.reserve(kDefaultNumberOfBlocks);
}
@@ -587,10 +585,6 @@
bool IsCompilingOsr() const { return osr_; }
- bool IsCompilingForSharedJitCode() const {
- return is_shared_jit_code_;
- }
-
ArenaSet<ArtMethod*>& GetCHASingleImplementationList() {
return cha_single_implementation_list_;
}
@@ -780,10 +774,6 @@
// List of methods that are assumed to have single implementation.
ArenaSet<ArtMethod*> cha_single_implementation_list_;
- // Whether we are JIT compiling in the shared region area, putting
- // restrictions on, for example, how literals are being generated.
- bool is_shared_jit_code_;
-
friend class SsaBuilder; // For caching constants.
friend class SsaLivenessAnalysis; // For the linear order.
friend class HInliner; // For the reverse post order.
diff --git a/compiler/optimizing/optimizing_compiler.cc b/compiler/optimizing/optimizing_compiler.cc
index 6f3b9fe..2153ddd 100644
--- a/compiler/optimizing/optimizing_compiler.cc
+++ b/compiler/optimizing/optimizing_compiler.cc
@@ -384,7 +384,6 @@
ArtMethod* method,
bool baseline,
bool osr,
- bool is_shared_jit_code,
VariableSizedHandleScope* handles) const;
CodeGenerator* TryCompileIntrinsic(ArenaAllocator* allocator,
@@ -784,7 +783,6 @@
ArtMethod* method,
bool baseline,
bool osr,
- bool is_shared_jit_code,
VariableSizedHandleScope* handles) const {
MaybeRecordStat(compilation_stats_.get(), MethodCompilationStat::kAttemptBytecodeCompilation);
const CompilerOptions& compiler_options = GetCompilerOptions();
@@ -852,8 +850,7 @@
kInvalidInvokeType,
dead_reference_safe,
compiler_options.GetDebuggable(),
- /* osr= */ osr,
- /* is_shared_jit_code= */ is_shared_jit_code);
+ /* osr= */ osr);
if (method != nullptr) {
graph->SetArtMethod(method);
@@ -1110,7 +1107,6 @@
method,
compiler_options.IsBaseline(),
/* osr= */ false,
- /* is_shared_jit_code= */ false,
&handles));
}
}
@@ -1372,7 +1368,6 @@
method,
baseline,
osr,
- /* is_shared_jit_code= */ code_cache->IsSharedRegion(*region),
&handles));
if (codegen.get() == nullptr) {
return false;
diff --git a/compiler/optimizing/sharpening.cc b/compiler/optimizing/sharpening.cc
index 3e22edc..8637db1 100644
--- a/compiler/optimizing/sharpening.cc
+++ b/compiler/optimizing/sharpening.cc
@@ -19,7 +19,6 @@
#include "art_method-inl.h"
#include "base/casts.h"
#include "base/enums.h"
-#include "base/logging.h"
#include "class_linker.h"
#include "code_generator.h"
#include "driver/compiler_options.h"
@@ -27,7 +26,6 @@
#include "gc/heap.h"
#include "gc/space/image_space.h"
#include "handle_scope-inl.h"
-#include "jit/jit.h"
#include "mirror/dex_cache.h"
#include "mirror/string.h"
#include "nodes.h"
@@ -100,17 +98,11 @@
}
code_ptr_location = HInvokeStaticOrDirect::CodePtrLocation::kCallArtMethod;
} else if (Runtime::Current()->UseJitCompilation()) {
- if (Runtime::Current()->GetJit()->CanEncodeMethod(
- callee,
- codegen->GetGraph()->IsCompilingForSharedJitCode())) {
- method_load_kind = HInvokeStaticOrDirect::MethodLoadKind::kJitDirectAddress;
- method_load_data = reinterpret_cast<uintptr_t>(callee);
- code_ptr_location = HInvokeStaticOrDirect::CodePtrLocation::kCallArtMethod;
- } else {
- // Do not sharpen.
- method_load_kind = HInvokeStaticOrDirect::MethodLoadKind::kRuntimeCall;
- code_ptr_location = HInvokeStaticOrDirect::CodePtrLocation::kCallArtMethod;
- }
+ // JIT or on-device AOT compilation referencing a boot image method.
+ // Use the method address directly.
+ method_load_kind = HInvokeStaticOrDirect::MethodLoadKind::kJitDirectAddress;
+ method_load_data = reinterpret_cast<uintptr_t>(callee);
+ code_ptr_location = HInvokeStaticOrDirect::CodePtrLocation::kCallArtMethod;
} else if (IsInBootImage(callee)) {
// Use PC-relative access to the .data.bimg.rel.ro methods array.
method_load_kind = HInvokeStaticOrDirect::MethodLoadKind::kBootImageRelRo;
@@ -183,16 +175,7 @@
if (is_in_boot_image) {
desired_load_kind = HLoadClass::LoadKind::kJitBootImageAddress;
} else if (klass != nullptr) {
- if (runtime->GetJit()->CanEncodeClass(
- klass.Get(),
- codegen->GetGraph()->IsCompilingForSharedJitCode())) {
- desired_load_kind = HLoadClass::LoadKind::kJitTableAddress;
- } else {
- // Shared JIT code cannot encode a literal that the GC can move.
- VLOG(jit) << "Unable to encode in shared region class literal: "
- << klass->PrettyClass();
- desired_load_kind = HLoadClass::LoadKind::kRuntimeCall;
- }
+ desired_load_kind = HLoadClass::LoadKind::kJitTableAddress;
} else {
// Class not loaded yet. This happens when the dex code requesting
// this `HLoadClass` hasn't been executed in the interpreter.
@@ -348,18 +331,10 @@
DCHECK(!codegen->GetCompilerOptions().GetCompilePic());
string = class_linker->LookupString(string_index, dex_cache.Get());
if (string != nullptr) {
- gc::Heap* heap = runtime->GetHeap();
- if (heap->ObjectIsInBootImageSpace(string)) {
+ if (runtime->GetHeap()->ObjectIsInBootImageSpace(string)) {
desired_load_kind = HLoadString::LoadKind::kJitBootImageAddress;
- } else if (runtime->GetJit()->CanEncodeString(
- string,
- codegen->GetGraph()->IsCompilingForSharedJitCode())) {
- desired_load_kind = HLoadString::LoadKind::kJitTableAddress;
} else {
- // Shared JIT code cannot encode a literal that the GC can move.
- VLOG(jit) << "Unable to encode in shared region string literal: "
- << string->ToModifiedUtf8();
- desired_load_kind = HLoadString::LoadKind::kRuntimeCall;
+ desired_load_kind = HLoadString::LoadKind::kJitTableAddress;
}
} else {
desired_load_kind = HLoadString::LoadKind::kRuntimeCall;
diff --git a/runtime/jit/jit.cc b/runtime/jit/jit.cc
index c5133b9..1f734fe 100644
--- a/runtime/jit/jit.cc
+++ b/runtime/jit/jit.cc
@@ -267,15 +267,15 @@
return false;
}
- JitMemoryRegion* region = GetCodeCache()->GetCurrentRegion();
-
// If we get a request to compile a proxy method, we pass the actual Java method
// of that proxy method, as the compiler does not expect a proxy method.
ArtMethod* method_to_compile = method->GetInterfaceMethodIfProxy(kRuntimePointerSize);
- if (!code_cache_->NotifyCompilationOf(method_to_compile, self, osr, prejit, region)) {
+ if (!code_cache_->NotifyCompilationOf(method_to_compile, self, osr, prejit)) {
return false;
}
+ JitMemoryRegion* region = GetCodeCache()->GetPrivateRegion();
+
VLOG(jit) << "Compiling method "
<< ArtMethod::PrettyMethod(method_to_compile)
<< " osr=" << std::boolalpha << osr;
@@ -838,7 +838,7 @@
klass == GetClassRoot<mirror::VarHandle>()) {
// MethodHandle and VarHandle invocation methods are required to throw an
// UnsupportedOperationException if invoked reflectively. We achieve this by having native
- // implementations that raise the exception. We need to disable JIT compilation of these JNI
+ // implementations that arise the exception. We need to disable JIT compilation of these JNI
// methods as it can lead to transitioning between JIT compiled JNI stubs and generic JNI
// stubs. Since these stubs have different stack representations we can then crash in stack
// walking (b/78151261).
@@ -1074,35 +1074,5 @@
thread_pool_->CreateThreads();
}
-bool Jit::CanEncodeMethod(ArtMethod* method ATTRIBUTE_UNUSED,
- bool is_for_shared_region ATTRIBUTE_UNUSED) const {
- // TODO: For shared region, we should only encode a method of a class
- // allocated before any fork.
- return true;
-}
-
-bool Jit::CanEncodeClass(ObjPtr<mirror::Class> cls, bool is_for_shared_region) const {
- // TODO: For shared region, we should only encode a non-moving class allocated
- // before any fork.
- return !is_for_shared_region || !Runtime::Current()->GetHeap()->IsMovableObject(cls);
-}
-
-bool Jit::CanEncodeString(ObjPtr<mirror::String> string, bool is_for_shared_region) const {
- // TODO: For shared region, we should only encode a non-moving string allocated
- // before any fork.
- return !is_for_shared_region || !Runtime::Current()->GetHeap()->IsMovableObject(string);
-}
-
-bool Jit::CanAssumeInitialized(ObjPtr<mirror::Class> cls,
- bool is_for_shared_region ATTRIBUTE_UNUSED) const {
- // TODO: For shared region, we should assume initialized if the class is initialized
- // before any fork.
- return cls->IsInitialized();
-}
-
-bool Jit::UseJitCompilation() {
- return options_->UseJitCompilation() && GetCodeCache()->GetCurrentRegion()->IsValid();
-}
-
} // namespace jit
} // namespace art
diff --git a/runtime/jit/jit.h b/runtime/jit/jit.h
index 1474a30..5643277 100644
--- a/runtime/jit/jit.h
+++ b/runtime/jit/jit.h
@@ -39,7 +39,6 @@
class Object;
class Class;
class ClassLoader;
-class String;
} // namespace mirror
namespace jit {
@@ -213,9 +212,10 @@
return options_->GetPriorityThreadWeight();
}
- // Return whether we should do JIT compilation. Note this will returns false
- // if we only need to save profile information and not compile methods.
- bool UseJitCompilation();
+ // Returns false if we only need to save profile information and not compile methods.
+ bool UseJitCompilation() const {
+ return options_->UseJitCompilation();
+ }
bool GetSaveProfilingInfo() const {
return options_->GetSaveProfilingInfo();
@@ -322,16 +322,6 @@
void RegisterDexFiles(const std::vector<std::unique_ptr<const DexFile>>& dex_files,
jobject class_loader);
- // Called by the compiler to know whether it can directly encode the
- // method/class/string.
- bool CanEncodeMethod(ArtMethod* method, bool is_for_shared_region) const;
- bool CanEncodeClass(ObjPtr<mirror::Class> cls, bool is_for_shared_region) const
- REQUIRES_SHARED(Locks::mutator_lock_);
- bool CanEncodeString(ObjPtr<mirror::String> string, bool is_for_shared_region) const
- REQUIRES_SHARED(Locks::mutator_lock_);
- bool CanAssumeInitialized(ObjPtr<mirror::Class> cls, bool is_for_shared_region) const
- REQUIRES_SHARED(Locks::mutator_lock_);
-
private:
Jit(JitCodeCache* code_cache, JitOptions* options);
diff --git a/runtime/jit/jit_code_cache.cc b/runtime/jit/jit_code_cache.cc
index d227cec..dd1dbea 100644
--- a/runtime/jit/jit_code_cache.cc
+++ b/runtime/jit/jit_code_cache.cc
@@ -206,10 +206,8 @@
if (is_zygote) {
// Zygote should never collect code to share the memory with the children.
jit_code_cache->garbage_collect_code_ = false;
- jit_code_cache->shared_region_ = std::move(region);
- } else {
- jit_code_cache->private_region_ = std::move(region);
}
+ jit_code_cache->private_region_ = std::move(region);
VLOG(jit) << "Created jit code cache: initial capacity="
<< PrettySize(initial_capacity)
@@ -385,8 +383,7 @@
return reinterpret_cast<const uint32_t*>(stack_map)[-1];
}
-static void DCheckRootsAreValid(const std::vector<Handle<mirror::Object>>& roots,
- bool is_shared_region)
+static void DCheckRootsAreValid(const std::vector<Handle<mirror::Object>>& roots)
REQUIRES(!Locks::intern_table_lock_) REQUIRES_SHARED(Locks::mutator_lock_) {
if (!kIsDebugBuild) {
return;
@@ -399,10 +396,6 @@
ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
CHECK(class_linker->GetInternTable()->LookupStrong(Thread::Current(), str) != nullptr);
}
- // Ensure that we don't put movable objects in the shared region.
- if (is_shared_region) {
- CHECK(!Runtime::Current()->GetHeap()->IsMovableObject(object.Get()));
- }
}
}
@@ -671,7 +664,7 @@
if (!method->IsNative()) {
// We need to do this before grabbing the lock_ because it needs to be able to see the string
// InternTable. Native methods do not have roots.
- DCheckRootsAreValid(roots, IsSharedRegion(*region));
+ DCheckRootsAreValid(roots);
}
size_t root_table_size = ComputeRootTableSize(roots.size());
@@ -1408,13 +1401,6 @@
bool retry_allocation)
// No thread safety analysis as we are using TryLock/Unlock explicitly.
NO_THREAD_SAFETY_ANALYSIS {
- // If we don't have a private region, we cannot allocate a profiling info.
- // A shared region doesn't support in general GC objects, which a profiling info
- // can reference.
- if (!private_region_.IsValid()) {
- return nullptr;
- }
-
ProfilingInfo* info = nullptr;
if (!retry_allocation) {
// If we are allocating for the interpreter, just try to lock, to avoid
@@ -1468,9 +1454,7 @@
}
void* JitCodeCache::MoreCore(const void* mspace, intptr_t increment) {
- return shared_region_.OwnsSpace(mspace)
- ? shared_region_.MoreCore(mspace, increment)
- : private_region_.MoreCore(mspace, increment);
+ return private_region_.MoreCore(mspace, increment);
}
void JitCodeCache::GetProfiledMethods(const std::set<std::string>& dex_base_locations,
@@ -1562,11 +1546,7 @@
return osr_code_map_.find(method) != osr_code_map_.end();
}
-bool JitCodeCache::NotifyCompilationOf(ArtMethod* method,
- Thread* self,
- bool osr,
- bool prejit,
- JitMemoryRegion* region) {
+bool JitCodeCache::NotifyCompilationOf(ArtMethod* method, Thread* self, bool osr, bool prejit) {
if (!osr && ContainsPc(method->GetEntryPointFromQuickCompiledCode())) {
return false;
}
@@ -1628,7 +1608,7 @@
ProfilingInfo* info = method->GetProfilingInfo(kRuntimePointerSize);
if (info == nullptr) {
// When prejitting, we don't allocate a profiling info.
- if (!prejit && !IsSharedRegion(*region)) {
+ if (!prejit) {
VLOG(jit) << method->PrettyMethod() << " needs a ProfilingInfo to be compiled";
// Because the counter is not atomic, there are some rare cases where we may not hit the
// threshold for creating the ProfilingInfo. Reset the counter now to "correct" this.
@@ -1737,19 +1717,13 @@
void JitCodeCache::PostForkChildAction(bool is_system_server, bool is_zygote) {
if (is_zygote) {
- // Don't create a private region for a child zygote. Regions are usually map shared
- // (to satisfy dual-view), and we don't want children of a child zygote to inherit it.
+ // Don't transition if this is for a child zygote.
return;
}
-
- if (private_region_.IsValid()) {
- // In case the zygote was running with its own private region (happens for
- // unit tests), move the region to the shared one.
- CHECK(!shared_region_.IsValid());
- std::swap(shared_region_, private_region_);
- }
MutexLock mu(Thread::Current(), *Locks::jit_lock_);
+ shared_region_ = std::move(private_region_);
+
// Reset all statistics to be specific to this process.
number_of_compilations_ = 0;
number_of_osr_compilations_ = 0;
@@ -1767,9 +1741,5 @@
}
}
-JitMemoryRegion* JitCodeCache::GetCurrentRegion() {
- return Runtime::Current()->IsZygote() ? &shared_region_ : &private_region_;
-}
-
} // namespace jit
} // namespace art
diff --git a/runtime/jit/jit_code_cache.h b/runtime/jit/jit_code_cache.h
index a777ab7..a4e2964 100644
--- a/runtime/jit/jit_code_cache.h
+++ b/runtime/jit/jit_code_cache.h
@@ -96,11 +96,7 @@
std::string* error_msg);
~JitCodeCache();
- bool NotifyCompilationOf(ArtMethod* method,
- Thread* self,
- bool osr,
- bool prejit,
- JitMemoryRegion* region)
+ bool NotifyCompilationOf(ArtMethod* method, Thread* self, bool osr, bool prejit)
REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(!Locks::jit_lock_);
@@ -217,7 +213,7 @@
REQUIRES_SHARED(Locks::mutator_lock_);
bool OwnsSpace(const void* mspace) const NO_THREAD_SAFETY_ANALYSIS {
- return private_region_.OwnsSpace(mspace) || shared_region_.OwnsSpace(mspace);
+ return private_region_.OwnsSpace(mspace);
}
void* MoreCore(const void* mspace, intptr_t increment);
@@ -280,8 +276,7 @@
// is debuggable.
void ClearEntryPointsInZygoteExecSpace() REQUIRES(!Locks::jit_lock_) REQUIRES(Locks::mutator_lock_);
- JitMemoryRegion* GetCurrentRegion();
- bool IsSharedRegion(const JitMemoryRegion& region) const { return ®ion == &shared_region_; }
+ JitMemoryRegion* GetPrivateRegion() { return &private_region_; }
private:
JitCodeCache();
diff --git a/runtime/jit/jit_memory_region.cc b/runtime/jit/jit_memory_region.cc
index 3438c37..2db5245 100644
--- a/runtime/jit/jit_memory_region.cc
+++ b/runtime/jit/jit_memory_region.cc
@@ -64,14 +64,9 @@
// File descriptor enabling dual-view mapping of code section.
unique_fd mem_fd;
- if (is_zygote) {
- // Because we are not going to GC code generated by the zygote, just use all available.
- current_capacity_ = max_capacity;
- mem_fd = unique_fd(CreateZygoteMemory(capacity, error_msg));
- if (mem_fd.get() < 0) {
- return false;
- }
- } else {
+ // Zygote shouldn't create a shared mapping for JIT, so we cannot use dual view
+ // for it.
+ if (!is_zygote) {
// Bionic supports memfd_create, but the call may fail on older kernels.
mem_fd = unique_fd(art::memfd_create("/jit-cache", /* flags= */ 0));
if (mem_fd.get() < 0) {
@@ -84,14 +79,16 @@
return false;
}
VLOG(jit) << oss.str();
- } else if (ftruncate(mem_fd, capacity) != 0) {
- std::ostringstream oss;
- oss << "Failed to initialize memory file: " << strerror(errno);
- *error_msg = oss.str();
- return false;
}
}
+ if (mem_fd.get() >= 0 && ftruncate(mem_fd, capacity) != 0) {
+ std::ostringstream oss;
+ oss << "Failed to initialize memory file: " << strerror(errno);
+ *error_msg = oss.str();
+ return false;
+ }
+
std::string data_cache_name = is_zygote ? "zygote-data-code-cache" : "data-code-cache";
std::string exec_cache_name = is_zygote ? "zygote-jit-code-cache" : "jit-code-cache";
@@ -210,13 +207,6 @@
}
}
}
- if (is_zygote) {
- // Now that we have created the writable and executable mappings, prevent creating any new
- // ones.
- if (!ProtectZygoteMemory(mem_fd.get(), error_msg)) {
- return false;
- }
- }
} else {
// Profiling only. No memory for code required.
}
@@ -244,14 +234,15 @@
CheckedCall(mprotect, "create code heap", code_heap->Begin(), code_heap->Size(), kProtRW);
exec_mspace_ = create_mspace_with_base(code_heap->Begin(), exec_end_, false /*locked*/);
CHECK(exec_mspace_ != nullptr) << "create_mspace_with_base (exec) failed";
- SetFootprintLimit(current_capacity_);
+ SetFootprintLimit(initial_capacity_);
// Protect pages containing heap metadata. Updates to the code heap toggle write permission to
// perform the update and there are no other times write access is required.
CheckedCall(mprotect, "protect code heap", code_heap->Begin(), code_heap->Size(), kProtR);
} else {
exec_mspace_ = nullptr;
- SetFootprintLimit(current_capacity_);
+ SetFootprintLimit(initial_capacity_);
}
+
return true;
}
diff --git a/runtime/jit/jit_memory_region.h b/runtime/jit/jit_memory_region.h
index 2cf01bd..b5f808d 100644
--- a/runtime/jit/jit_memory_region.h
+++ b/runtime/jit/jit_memory_region.h
@@ -107,10 +107,6 @@
REQUIRES(Locks::jit_lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
- bool IsValid() const NO_THREAD_SAFETY_ANALYSIS {
- return exec_mspace_ != nullptr || data_mspace_ != nullptr;
- }
-
bool HasDualCodeMapping() const {
return non_exec_pages_.IsValid();
}