Revision: 17473
Author: [email protected]
Date: Tue Nov 5 10:14:48 2013 UTC
Log: Make snapshots reproducible.
To keep the structure of the serializer more or less untouched, we use
some ingenious Corry-approved(TM) 3-step technology (a.k.a. "hack"):
* Create copies of code objects.
* Wipe out all absolute addresses in these copies.
* Write out the cleaned copies instead of the originals.
In conjunction with --random-seed, our snapshots are reproducible now.
BUG=v8:2885
[email protected], [email protected]
Review URL: https://codereview.chromium.org/54823002
http://code.google.com/p/v8/source/detail?r=17473
Modified:
/branches/bleeding_edge/src/arm/assembler-arm-inl.h
/branches/bleeding_edge/src/assembler.h
/branches/bleeding_edge/src/ia32/assembler-ia32-inl.h
/branches/bleeding_edge/src/mips/assembler-mips-inl.h
/branches/bleeding_edge/src/objects-inl.h
/branches/bleeding_edge/src/objects.h
/branches/bleeding_edge/src/serialize.cc
/branches/bleeding_edge/src/x64/assembler-x64-inl.h
=======================================
--- /branches/bleeding_edge/src/arm/assembler-arm-inl.h Tue Nov 5 09:40:36
2013 UTC
+++ /branches/bleeding_edge/src/arm/assembler-arm-inl.h Tue Nov 5 10:14:48
2013 UTC
@@ -256,6 +256,15 @@
(IsDebugBreakSlot(rmode()) && IsPatchedDebugBreakSlotSequence()));
return reinterpret_cast<Object**>(pc_ + 2 * Assembler::kInstrSize);
}
+
+
+void RelocInfo::WipeOut() {
+ ASSERT(IsEmbeddedObject(rmode_) ||
+ IsCodeTarget(rmode_) ||
+ IsRuntimeEntry(rmode_) ||
+ IsExternalReference(rmode_));
+ Assembler::set_target_pointer_at(pc_, NULL);
+}
bool RelocInfo::IsPatchedReturnSequence() {
=======================================
--- /branches/bleeding_edge/src/assembler.h Tue Nov 5 09:40:36 2013 UTC
+++ /branches/bleeding_edge/src/assembler.h Tue Nov 5 10:14:48 2013 UTC
@@ -435,6 +435,10 @@
INLINE(void set_call_object(Object* target));
INLINE(Object** call_object_address());
+ // Wipe out a relocation to a fixed value, used for making snapshots
+ // reproducible.
+ INLINE(void WipeOut());
+
template<typename StaticVisitor> inline void Visit(Heap* heap);
inline void Visit(Isolate* isolate, ObjectVisitor* v);
=======================================
--- /branches/bleeding_edge/src/ia32/assembler-ia32-inl.h Tue Nov 5
09:40:36 2013 UTC
+++ /branches/bleeding_edge/src/ia32/assembler-ia32-inl.h Tue Nov 5
10:14:48 2013 UTC
@@ -241,6 +241,18 @@
(IsDebugBreakSlot(rmode()) && IsPatchedDebugBreakSlotSequence()));
return reinterpret_cast<Object**>(pc_ + 1);
}
+
+
+void RelocInfo::WipeOut() {
+ if (IsEmbeddedObject(rmode_) || IsExternalReference(rmode_)) {
+ Memory::Address_at(pc_) = NULL;
+ } else if (IsCodeTarget(rmode_) || IsRuntimeEntry(rmode_)) {
+ // Effectively write zero into the relocation.
+ Assembler::set_target_address_at(pc_, pc_ + sizeof(int32_t));
+ } else {
+ UNREACHABLE();
+ }
+}
bool RelocInfo::IsPatchedReturnSequence() {
=======================================
--- /branches/bleeding_edge/src/mips/assembler-mips-inl.h Tue Nov 5
09:40:36 2013 UTC
+++ /branches/bleeding_edge/src/mips/assembler-mips-inl.h Tue Nov 5
10:14:48 2013 UTC
@@ -313,6 +313,15 @@
void RelocInfo::set_call_object(Object* target) {
*call_object_address() = target;
}
+
+
+void RelocInfo::WipeOut() {
+ ASSERT(IsEmbeddedObject(rmode_) ||
+ IsCodeTarget(rmode_) ||
+ IsRuntimeEntry(rmode_) ||
+ IsExternalReference(rmode_));
+ Assembler::set_target_address_at(pc_, NULL);
+}
bool RelocInfo::IsPatchedReturnSequence() {
=======================================
--- /branches/bleeding_edge/src/objects-inl.h Tue Nov 5 10:05:03 2013 UTC
+++ /branches/bleeding_edge/src/objects-inl.h Tue Nov 5 10:14:48 2013 UTC
@@ -5323,6 +5323,17 @@
ACCESSORS(Code, raw_type_feedback_info, Object, kTypeFeedbackInfoOffset)
+void Code::WipeOutHeader() {
+ WRITE_FIELD(this, kRelocationInfoOffset, NULL);
+ WRITE_FIELD(this, kHandlerTableOffset, NULL);
+ WRITE_FIELD(this, kDeoptimizationDataOffset, NULL);
+ // Do not wipe out e.g. a minor key.
+ if (!READ_FIELD(this, kTypeFeedbackInfoOffset)->IsSmi()) {
+ WRITE_FIELD(this, kTypeFeedbackInfoOffset, NULL);
+ }
+}
+
+
Object* Code::type_feedback_info() {
ASSERT(kind() == FUNCTION);
return raw_type_feedback_info();
=======================================
--- /branches/bleeding_edge/src/objects.h Tue Nov 5 10:05:03 2013 UTC
+++ /branches/bleeding_edge/src/objects.h Tue Nov 5 10:14:48 2013 UTC
@@ -5198,6 +5198,15 @@
void ReplaceNthCell(int n, Cell* replace_with);
+ // The entire code object including its header is copied verbatim to the
+ // snapshot so that it can be written in one, fast, memcpy during
+ // deserialization. The deserializer will overwrite some pointers, rather
+ // like a runtime linker, but the random allocation addresses used in the
+ // mksnapshot process would still be present in the unlinked snapshot
data,
+ // which would make snapshot production non-reproducible. This method
wipes
+ // out the to-be-overwritten header data for reproducible snapshots.
+ inline void WipeOutHeader();
+
class ExtraICStateStrictMode: public BitField<StrictModeFlag, 0, 1> {};
class ExtraICStateKeyedAccessStoreMode:
public BitField<KeyedAccessStoreMode, 1, 4> {}; // NOLINT
=======================================
--- /branches/bleeding_edge/src/serialize.cc Tue Nov 5 09:40:36 2013 UTC
+++ /branches/bleeding_edge/src/serialize.cc Tue Nov 5 10:14:48 2013 UTC
@@ -1774,12 +1774,31 @@
// can't serialize any other kinds of external strings.
UNREACHABLE();
}
+
+
+static Code* CloneCodeObject(HeapObject* code) {
+ Address copy = new byte[code->Size()];
+ OS::MemCopy(copy, code->address(), code->Size());
+ return Code::cast(HeapObject::FromAddress(copy));
+}
+
+
+static void WipeOutRelocations(Code* code) {
+ int mode_mask =
+ RelocInfo::kCodeTargetMask |
+ RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT) |
+ RelocInfo::ModeMask(RelocInfo::EXTERNAL_REFERENCE) |
+ RelocInfo::ModeMask(RelocInfo::RUNTIME_ENTRY);
+ for (RelocIterator it(code, mode_mask); !it.done(); it.next()) {
+ it.rinfo()->WipeOut();
+ }
+}
int Serializer::ObjectSerializer::OutputRawData(
Address up_to, Serializer::ObjectSerializer::ReturnSkip return_skip) {
Address object_start = object_->address();
- Address base = object_start + bytes_processed_so_far_;
+ int base = bytes_processed_so_far_;
int up_to_offset = static_cast<int>(up_to - object_start);
int to_skip = up_to_offset - bytes_processed_so_far_;
int bytes_to_output = to_skip;
@@ -1809,10 +1828,22 @@
sink_->Put(kRawData, "RawData");
sink_->PutInt(bytes_to_output, "length");
}
+
+ // To make snapshots reproducible, we need to wipe out all pointers in
code.
+ if (code_object_) {
+ Code* code = CloneCodeObject(object_);
+ WipeOutRelocations(code);
+ // We need to wipe out the header fields *after* wiping out the
+ // relocations, because some of these fields are needed for the
latter.
+ code->WipeOutHeader();
+ object_start = code->address();
+ }
+
+ const char* description = code_object_ ? "Code" : "Byte";
for (int i = 0; i < bytes_to_output; i++) {
- unsigned int data = base[i];
- sink_->PutSection(data, "Byte");
+ sink_->PutSection(object_start[base + i], description);
}
+ if (code_object_) delete[] object_start;
}
if (to_skip != 0 && return_skip == kIgnoringReturn) {
sink_->Put(kSkip, "Skip");
=======================================
--- /branches/bleeding_edge/src/x64/assembler-x64-inl.h Tue Nov 5 09:40:36
2013 UTC
+++ /branches/bleeding_edge/src/x64/assembler-x64-inl.h Tue Nov 5 10:14:48
2013 UTC
@@ -362,6 +362,18 @@
host(), NULL, cell);
}
}
+
+
+void RelocInfo::WipeOut() {
+ if (IsEmbeddedObject(rmode_) || IsExternalReference(rmode_)) {
+ Memory::Address_at(pc_) = NULL;
+ } else if (IsCodeTarget(rmode_) || IsRuntimeEntry(rmode_)) {
+ // Effectively write zero into the relocation.
+ Assembler::set_target_address_at(pc_, pc_ + sizeof(int32_t));
+ } else {
+ UNREACHABLE();
+ }
+}
bool RelocInfo::IsPatchedReturnSequence() {
--
--
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