Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 1 | // Copyright 2012 the V8 project authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #ifndef V8_DEBUG_LIVEEDIT_H_ |
| 6 | #define V8_DEBUG_LIVEEDIT_H_ |
| 7 | |
| 8 | |
| 9 | // Live Edit feature implementation. |
| 10 | // User should be able to change script on already running VM. This feature |
| 11 | // matches hot swap features in other frameworks. |
| 12 | // |
| 13 | // The basic use-case is when user spots some mistake in function body |
| 14 | // from debugger and wishes to change the algorithm without restart. |
| 15 | // |
| 16 | // A single change always has a form of a simple replacement (in pseudo-code): |
| 17 | // script.source[positions, positions+length] = new_string; |
| 18 | // Implementation first determines, which function's body includes this |
| 19 | // change area. Then both old and new versions of script are fully compiled |
| 20 | // in order to analyze, whether the function changed its outer scope |
| 21 | // expectations (or number of parameters). If it didn't, function's code is |
| 22 | // patched with a newly compiled code. If it did change, enclosing function |
| 23 | // gets patched. All inner functions are left untouched, whatever happened |
| 24 | // to them in a new script version. However, new version of code will |
| 25 | // instantiate newly compiled functions. |
| 26 | |
| 27 | |
| 28 | #include "src/allocation.h" |
| 29 | #include "src/compiler.h" |
| 30 | |
| 31 | namespace v8 { |
| 32 | namespace internal { |
| 33 | |
| 34 | // This class collects some specific information on structure of functions |
| 35 | // in a particular script. It gets called from compiler all the time, but |
| 36 | // actually records any data only when liveedit operation is in process; |
| 37 | // in any other time this class is very cheap. |
| 38 | // |
| 39 | // The primary interest of the Tracker is to record function scope structures |
| 40 | // in order to analyze whether function code maybe safely patched (with new |
| 41 | // code successfully reading existing data from function scopes). The Tracker |
| 42 | // also collects compiled function codes. |
| 43 | class LiveEditFunctionTracker { |
| 44 | public: |
| 45 | explicit LiveEditFunctionTracker(Isolate* isolate, FunctionLiteral* fun); |
| 46 | ~LiveEditFunctionTracker(); |
| 47 | void RecordFunctionInfo(Handle<SharedFunctionInfo> info, |
| 48 | FunctionLiteral* lit, Zone* zone); |
| 49 | void RecordRootFunctionInfo(Handle<Code> code); |
| 50 | |
| 51 | static bool IsActive(Isolate* isolate); |
| 52 | |
| 53 | private: |
| 54 | Isolate* isolate_; |
| 55 | }; |
| 56 | |
| 57 | |
| 58 | class LiveEdit : AllStatic { |
| 59 | public: |
| 60 | // Describes how exactly a frame has been dropped from stack. |
| 61 | enum FrameDropMode { |
| 62 | // No frame has been dropped. |
| 63 | FRAMES_UNTOUCHED, |
| 64 | // The top JS frame had been calling debug break slot stub. Patch the |
| 65 | // address this stub jumps to in the end. |
| 66 | FRAME_DROPPED_IN_DEBUG_SLOT_CALL, |
| 67 | // The top JS frame had been calling some C++ function. The return address |
| 68 | // gets patched automatically. |
| 69 | FRAME_DROPPED_IN_DIRECT_CALL, |
| 70 | FRAME_DROPPED_IN_RETURN_CALL, |
| 71 | CURRENTLY_SET_MODE |
| 72 | }; |
| 73 | |
| 74 | static void InitializeThreadLocal(Debug* debug); |
| 75 | |
| 76 | static bool SetAfterBreakTarget(Debug* debug); |
| 77 | |
| 78 | MUST_USE_RESULT static MaybeHandle<JSArray> GatherCompileInfo( |
| 79 | Handle<Script> script, |
| 80 | Handle<String> source); |
| 81 | |
| 82 | static void ReplaceFunctionCode(Handle<JSArray> new_compile_info_array, |
| 83 | Handle<JSArray> shared_info_array); |
| 84 | |
| 85 | static void FunctionSourceUpdated(Handle<JSArray> shared_info_array); |
| 86 | |
| 87 | // Updates script field in FunctionSharedInfo. |
| 88 | static void SetFunctionScript(Handle<JSValue> function_wrapper, |
| 89 | Handle<Object> script_handle); |
| 90 | |
| 91 | static void PatchFunctionPositions(Handle<JSArray> shared_info_array, |
| 92 | Handle<JSArray> position_change_array); |
| 93 | |
| 94 | // For a script updates its source field. If old_script_name is provided |
| 95 | // (i.e. is a String), also creates a copy of the script with its original |
| 96 | // source and sends notification to debugger. |
| 97 | static Handle<Object> ChangeScriptSource(Handle<Script> original_script, |
| 98 | Handle<String> new_source, |
| 99 | Handle<Object> old_script_name); |
| 100 | |
| 101 | // In a code of a parent function replaces original function as embedded |
| 102 | // object with a substitution one. |
| 103 | static void ReplaceRefToNestedFunction(Handle<JSValue> parent_function_shared, |
| 104 | Handle<JSValue> orig_function_shared, |
| 105 | Handle<JSValue> subst_function_shared); |
| 106 | |
| 107 | // Find open generator activations, and set corresponding "result" elements to |
| 108 | // FUNCTION_BLOCKED_ACTIVE_GENERATOR. |
| 109 | static bool FindActiveGenerators(Handle<FixedArray> shared_info_array, |
| 110 | Handle<FixedArray> result, int len); |
| 111 | |
| 112 | // Checks listed functions on stack and return array with corresponding |
| 113 | // FunctionPatchabilityStatus statuses; extra array element may |
| 114 | // contain general error message. Modifies the current stack and |
| 115 | // has restart the lowest found frames and drops all other frames above |
| 116 | // if possible and if do_drop is true. |
| 117 | static Handle<JSArray> CheckAndDropActivations( |
| 118 | Handle<JSArray> old_shared_array, Handle<JSArray> new_shared_array, |
| 119 | bool do_drop); |
| 120 | |
| 121 | // Restarts the call frame and completely drops all frames above it. |
| 122 | // Return error message or NULL. |
| 123 | static const char* RestartFrame(JavaScriptFrame* frame); |
| 124 | |
| 125 | // A copy of this is in liveedit.js. |
| 126 | enum FunctionPatchabilityStatus { |
| 127 | FUNCTION_AVAILABLE_FOR_PATCH = 1, |
| 128 | FUNCTION_BLOCKED_ON_ACTIVE_STACK = 2, |
| 129 | FUNCTION_BLOCKED_ON_OTHER_STACK = 3, |
| 130 | FUNCTION_BLOCKED_UNDER_NATIVE_CODE = 4, |
| 131 | FUNCTION_REPLACED_ON_ACTIVE_STACK = 5, |
| 132 | FUNCTION_BLOCKED_UNDER_GENERATOR = 6, |
| 133 | FUNCTION_BLOCKED_ACTIVE_GENERATOR = 7, |
| 134 | FUNCTION_BLOCKED_NO_NEW_TARGET_ON_RESTART = 8 |
| 135 | }; |
| 136 | |
| 137 | // Compares 2 strings line-by-line, then token-wise and returns diff in form |
| 138 | // of array of triplets (pos1, pos1_end, pos2_end) describing list |
| 139 | // of diff chunks. |
| 140 | static Handle<JSArray> CompareStrings(Handle<String> s1, |
| 141 | Handle<String> s2); |
| 142 | |
| 143 | // Architecture-specific constant. |
| 144 | static const bool kFrameDropperSupported; |
| 145 | |
| 146 | /** |
| 147 | * Defines layout of a stack frame that supports padding. This is a regular |
| 148 | * internal frame that has a flexible stack structure. LiveEdit can shift |
| 149 | * its lower part up the stack, taking up the 'padding' space when additional |
| 150 | * stack memory is required. |
| 151 | * Such frame is expected immediately above the topmost JavaScript frame. |
| 152 | * |
| 153 | * Stack Layout: |
| 154 | * --- Top |
| 155 | * LiveEdit routine frames |
| 156 | * --- |
| 157 | * C frames of debug handler |
| 158 | * --- |
| 159 | * ... |
| 160 | * --- |
| 161 | * An internal frame that has n padding words: |
| 162 | * - any number of words as needed by code -- upper part of frame |
| 163 | * - padding size: a Smi storing n -- current size of padding |
| 164 | * - padding: n words filled with kPaddingValue in form of Smi |
| 165 | * - 3 context/type words of a regular InternalFrame |
| 166 | * - fp |
| 167 | * --- |
| 168 | * Topmost JavaScript frame |
| 169 | * --- |
| 170 | * ... |
| 171 | * --- Bottom |
| 172 | */ |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 173 | // A number of words that should be reserved on stack for the LiveEdit use. |
| 174 | // Stored on stack in form of Smi. |
| 175 | static const int kFramePaddingInitialSize = 1; |
| 176 | // A value that padding words are filled with (in form of Smi). Going |
| 177 | // bottom-top, the first word not having this value is a counter word. |
| 178 | static const int kFramePaddingValue = kFramePaddingInitialSize + 1; |
| 179 | }; |
| 180 | |
| 181 | |
| 182 | // A general-purpose comparator between 2 arrays. |
| 183 | class Comparator { |
| 184 | public: |
| 185 | // Holds 2 arrays of some elements allowing to compare any pair of |
| 186 | // element from the first array and element from the second array. |
| 187 | class Input { |
| 188 | public: |
| 189 | virtual int GetLength1() = 0; |
| 190 | virtual int GetLength2() = 0; |
| 191 | virtual bool Equals(int index1, int index2) = 0; |
| 192 | |
| 193 | protected: |
| 194 | virtual ~Input() {} |
| 195 | }; |
| 196 | |
| 197 | // Receives compare result as a series of chunks. |
| 198 | class Output { |
| 199 | public: |
| 200 | // Puts another chunk in result list. Note that technically speaking |
| 201 | // only 3 arguments actually needed with 4th being derivable. |
| 202 | virtual void AddChunk(int pos1, int pos2, int len1, int len2) = 0; |
| 203 | |
| 204 | protected: |
| 205 | virtual ~Output() {} |
| 206 | }; |
| 207 | |
| 208 | // Finds the difference between 2 arrays of elements. |
| 209 | static void CalculateDifference(Input* input, |
| 210 | Output* result_writer); |
| 211 | }; |
| 212 | |
| 213 | |
| 214 | |
| 215 | // Simple helper class that creates more or less typed structures over |
| 216 | // JSArray object. This is an adhoc method of passing structures from C++ |
| 217 | // to JavaScript. |
| 218 | template<typename S> |
| 219 | class JSArrayBasedStruct { |
| 220 | public: |
| 221 | static S Create(Isolate* isolate) { |
| 222 | Factory* factory = isolate->factory(); |
| 223 | Handle<JSArray> array = factory->NewJSArray(S::kSize_); |
| 224 | return S(array); |
| 225 | } |
| 226 | |
| 227 | static S cast(Object* object) { |
| 228 | JSArray* array = JSArray::cast(object); |
| 229 | Handle<JSArray> array_handle(array); |
| 230 | return S(array_handle); |
| 231 | } |
| 232 | |
| 233 | explicit JSArrayBasedStruct(Handle<JSArray> array) : array_(array) { |
| 234 | } |
| 235 | |
| 236 | Handle<JSArray> GetJSArray() { |
| 237 | return array_; |
| 238 | } |
| 239 | |
| 240 | Isolate* isolate() const { |
| 241 | return array_->GetIsolate(); |
| 242 | } |
| 243 | |
| 244 | protected: |
| 245 | void SetField(int field_position, Handle<Object> value) { |
| 246 | Object::SetElement(isolate(), array_, field_position, value, SLOPPY) |
| 247 | .Assert(); |
| 248 | } |
| 249 | |
| 250 | void SetSmiValueField(int field_position, int value) { |
| 251 | SetField(field_position, Handle<Smi>(Smi::FromInt(value), isolate())); |
| 252 | } |
| 253 | |
| 254 | Handle<Object> GetField(int field_position) { |
Ben Murdoch | da12d29 | 2016-06-02 14:46:10 +0100 | [diff] [blame] | 255 | return JSReceiver::GetElement(isolate(), array_, field_position) |
| 256 | .ToHandleChecked(); |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 257 | } |
| 258 | |
| 259 | int GetSmiValueField(int field_position) { |
| 260 | Handle<Object> res = GetField(field_position); |
| 261 | return Handle<Smi>::cast(res)->value(); |
| 262 | } |
| 263 | |
| 264 | private: |
| 265 | Handle<JSArray> array_; |
| 266 | }; |
| 267 | |
| 268 | |
| 269 | // Represents some function compilation details. This structure will be used |
| 270 | // from JavaScript. It contains Code object, which is kept wrapped |
| 271 | // into a BlindReference for sanitizing reasons. |
| 272 | class FunctionInfoWrapper : public JSArrayBasedStruct<FunctionInfoWrapper> { |
| 273 | public: |
| 274 | explicit FunctionInfoWrapper(Handle<JSArray> array) |
| 275 | : JSArrayBasedStruct<FunctionInfoWrapper>(array) { |
| 276 | } |
| 277 | |
| 278 | void SetInitialProperties(Handle<String> name, int start_position, |
| 279 | int end_position, int param_num, int literal_count, |
| 280 | int parent_index); |
| 281 | |
| 282 | void SetFunctionCode(Handle<Code> function_code, |
| 283 | Handle<HeapObject> code_scope_info); |
| 284 | |
| 285 | void SetFunctionScopeInfo(Handle<Object> scope_info_array) { |
| 286 | this->SetField(kFunctionScopeInfoOffset_, scope_info_array); |
| 287 | } |
| 288 | |
| 289 | void SetSharedFunctionInfo(Handle<SharedFunctionInfo> info); |
| 290 | |
| 291 | int GetLiteralCount() { |
| 292 | return this->GetSmiValueField(kLiteralNumOffset_); |
| 293 | } |
| 294 | |
| 295 | int GetParentIndex() { |
| 296 | return this->GetSmiValueField(kParentIndexOffset_); |
| 297 | } |
| 298 | |
| 299 | Handle<Code> GetFunctionCode(); |
| 300 | |
| 301 | MaybeHandle<TypeFeedbackVector> GetFeedbackVector(); |
| 302 | |
| 303 | Handle<Object> GetCodeScopeInfo(); |
| 304 | |
| 305 | int GetStartPosition() { |
| 306 | return this->GetSmiValueField(kStartPositionOffset_); |
| 307 | } |
| 308 | |
| 309 | int GetEndPosition() { return this->GetSmiValueField(kEndPositionOffset_); } |
| 310 | |
| 311 | private: |
| 312 | static const int kFunctionNameOffset_ = 0; |
| 313 | static const int kStartPositionOffset_ = 1; |
| 314 | static const int kEndPositionOffset_ = 2; |
| 315 | static const int kParamNumOffset_ = 3; |
| 316 | static const int kCodeOffset_ = 4; |
| 317 | static const int kCodeScopeInfoOffset_ = 5; |
| 318 | static const int kFunctionScopeInfoOffset_ = 6; |
| 319 | static const int kParentIndexOffset_ = 7; |
| 320 | static const int kSharedFunctionInfoOffset_ = 8; |
| 321 | static const int kLiteralNumOffset_ = 9; |
| 322 | static const int kSize_ = 10; |
| 323 | |
| 324 | friend class JSArrayBasedStruct<FunctionInfoWrapper>; |
| 325 | }; |
| 326 | |
| 327 | |
| 328 | // Wraps SharedFunctionInfo along with some of its fields for passing it |
| 329 | // back to JavaScript. SharedFunctionInfo object itself is additionally |
| 330 | // wrapped into BlindReference for sanitizing reasons. |
| 331 | class SharedInfoWrapper : public JSArrayBasedStruct<SharedInfoWrapper> { |
| 332 | public: |
| 333 | static bool IsInstance(Handle<JSArray> array) { |
| 334 | if (array->length() != Smi::FromInt(kSize_)) return false; |
| 335 | Handle<Object> element( |
Ben Murdoch | da12d29 | 2016-06-02 14:46:10 +0100 | [diff] [blame] | 336 | JSReceiver::GetElement(array->GetIsolate(), array, kSharedInfoOffset_) |
| 337 | .ToHandleChecked()); |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 338 | if (!element->IsJSValue()) return false; |
| 339 | return Handle<JSValue>::cast(element)->value()->IsSharedFunctionInfo(); |
| 340 | } |
| 341 | |
| 342 | explicit SharedInfoWrapper(Handle<JSArray> array) |
| 343 | : JSArrayBasedStruct<SharedInfoWrapper>(array) { |
| 344 | } |
| 345 | |
| 346 | void SetProperties(Handle<String> name, |
| 347 | int start_position, |
| 348 | int end_position, |
| 349 | Handle<SharedFunctionInfo> info); |
| 350 | |
| 351 | Handle<SharedFunctionInfo> GetInfo(); |
| 352 | |
| 353 | private: |
| 354 | static const int kFunctionNameOffset_ = 0; |
| 355 | static const int kStartPositionOffset_ = 1; |
| 356 | static const int kEndPositionOffset_ = 2; |
| 357 | static const int kSharedInfoOffset_ = 3; |
| 358 | static const int kSize_ = 4; |
| 359 | |
| 360 | friend class JSArrayBasedStruct<SharedInfoWrapper>; |
| 361 | }; |
| 362 | |
| 363 | } // namespace internal |
| 364 | } // namespace v8 |
| 365 | |
| 366 | #endif /* V8_DEBUG_LIVEEDIT_H_ */ |