[asm.js] [wasm] Store function start position for stack check

We did not associate any position to the stack check in the wasm
function prologue, hence a check failed later when trying to map the
non-existent position to the asm.js source position.

With this CL, we add a mapping to the source position table, mapping
the stack check call to byte offset 0 (which is distinct from any valid
instruction position). Also, we add another entry to the asm.js source
position sidetable, mapping byte offset 0 to the start source position
of the function body.

R=titzer@chromium.org, ahaas@chromium.org
BUG=chromium:677685

Review-Url: https://codereview.chromium.org/2609363004
Cr-Commit-Position: refs/heads/master@{#42130}

src/asmjs/asm-wasm-builder.cc

@@ -176,6 +176,11 @@ class AsmWasmBuilderImpl final : public AstVisitor<AsmWasmBuilderImpl> {
     }
     current_function_builder_ = LookupOrInsertFunction(decl->proxy()->var());
     scope_ = kFuncScope;
+
+    // Record start of the function, used as position for the stack check.
+    current_function_builder_->SetAsmFunctionStartPosition(
+        decl->fun()->start_position());
+
     RECURSE(Visit(decl->fun()));
     decl->set_fun(old_func);
     if (new_func_scope != nullptr) {

src/compiler/wasm-compiler.cc

@@ -488,17 +488,14 @@ void WasmGraphBuilder::StackCheck(wasm::WasmCodePosition position,
     stack_check.Chain(*control);
     Node* effect_true = *effect;
 
-    Node* effect_false;
     // Generate a call to the runtime if there is a stack check failure.
-    {
-      Node* node = BuildCallToRuntime(Runtime::kStackGuard, jsgraph(),
-                                      module_->instance->context, nullptr, 0,
-                                      effect, stack_check.if_false);
-      effect_false = node;
-    }
+    Node* call = BuildCallToRuntime(Runtime::kStackGuard, jsgraph(),
+                                    module_->instance->context, nullptr, 0,
+                                    effect, stack_check.if_false);
+    SetSourcePosition(call, position);
 
     Node* ephi = graph()->NewNode(jsgraph()->common()->EffectPhi(2),
-                                  effect_true, effect_false, stack_check.merge);
+                                  effect_true, call, stack_check.merge);
 
     *control = stack_check.merge;
     *effect = ephi;

src/runtime/runtime-test.cc

@@ -699,6 +699,13 @@ RUNTIME_FUNCTION(Runtime_IsAsmWasmCode) {
   return isolate->heap()->true_value();
 }
 
+RUNTIME_FUNCTION(Runtime_IsWasmCode) {
+  SealHandleScope shs(isolate);
+  DCHECK_EQ(1, args.length());
+  CONVERT_ARG_CHECKED(JSFunction, function, 0);
+  bool is_js_to_wasm = function->code()->kind() == Code::JS_TO_WASM_FUNCTION;
+  return isolate->heap()->ToBoolean(is_js_to_wasm);
+}
 
 #define ELEMENTS_KIND_CHECK_RUNTIME_FUNCTION(Name)       \
   RUNTIME_FUNCTION(Runtime_Has##Name) {                  \

src/runtime/runtime.h

@@ -906,6 +906,7 @@ namespace internal {
   F(SerializeWasmModule, 1, 1)                \
   F(DeserializeWasmModule, 2, 1)              \
   F(IsAsmWasmCode, 1, 1)                      \
+  F(IsWasmCode, 1, 1)                         \
   F(ValidateWasmInstancesChain, 2, 1)         \
   F(ValidateWasmModuleState, 1, 1)            \
   F(ValidateWasmOrphanedInstance, 1, 1)

src/wasm/function-body-decoder.cc

@@ -619,7 +619,9 @@ class WasmFullDecoder : public WasmDecoder {
     ssa_env->effect = start;
     SetEnv("initial", ssa_env);
     if (builder_) {
-      builder_->StackCheck(position());
+      // The function-prologue stack check is associated with position 0, which
+      // is never a position of any instruction in the function.
+      builder_->StackCheck(0);
     }
   }
 

src/wasm/module-decoder.cc

@@ -1202,11 +1202,15 @@ AsmJsOffsetsResult DecodeAsmJsOffsets(const byte* tables_start,
       decoder.error("illegal asm function offset table size");
     }
     const byte* table_end = decoder.pc() + size;
-    uint32_t locals_size = decoder.consume_u32("locals size");
+    uint32_t locals_size = decoder.consume_u32v("locals size");
+    int function_start_position = decoder.consume_u32v("function start pos");
     int last_byte_offset = locals_size;
-    int last_asm_position = 0;
+    int last_asm_position = function_start_position;
     std::vector<AsmJsOffsetEntry> func_asm_offsets;
     func_asm_offsets.reserve(size / 4);  // conservative estimation
+    // Add an entry for the stack check, associated with position 0.
+    func_asm_offsets.push_back(
+        {0, function_start_position, function_start_position});
     while (decoder.ok() && decoder.pc() < table_end) {
       last_byte_offset += decoder.consume_u32v("byte offset delta");
       int call_position =

src/wasm/wasm-module-builder.cc

@@ -152,7 +152,7 @@ void WasmFunctionBuilder::SetName(Vector<const char> name) {
 
 void WasmFunctionBuilder::AddAsmWasmOffset(int call_position,
                                            int to_number_position) {
-  // We only want to emit one mapping per byte offset:
+  // We only want to emit one mapping per byte offset.
   DCHECK(asm_offsets_.size() == 0 || body_.size() > last_asm_byte_offset_);
 
   DCHECK_LE(body_.size(), kMaxUInt32);
@@ -168,6 +168,15 @@ void WasmFunctionBuilder::AddAsmWasmOffset(int call_position,
   last_asm_source_position_ = to_number_position;
 }
 
+void WasmFunctionBuilder::SetAsmFunctionStartPosition(int position) {
+  DCHECK_EQ(0, asm_func_start_source_position_);
+  DCHECK_LE(0, position);
+  // Must be called before emitting any asm.js source position.
+  DCHECK_EQ(0, asm_offsets_.size());
+  asm_func_start_source_position_ = position;
+  last_asm_source_position_ = position;
+}
+
 void WasmFunctionBuilder::WriteSignature(ZoneBuffer& buffer) const {
   buffer.write_u32v(signature_index_);
 }
@@ -201,14 +210,19 @@ void WasmFunctionBuilder::WriteBody(ZoneBuffer& buffer) const {
 }
 
 void WasmFunctionBuilder::WriteAsmWasmOffsetTable(ZoneBuffer& buffer) const {
-  if (asm_offsets_.size() == 0) {
+  if (asm_func_start_source_position_ == 0 && asm_offsets_.size() == 0) {
     buffer.write_size(0);
     return;
   }
-  buffer.write_size(asm_offsets_.size() + kInt32Size);
+  size_t locals_enc_size = LEBHelper::sizeof_u32v(locals_.Size());
+  size_t func_start_size =
+      LEBHelper::sizeof_u32v(asm_func_start_source_position_);
+  buffer.write_size(asm_offsets_.size() + locals_enc_size + func_start_size);
   // Offset of the recorded byte offsets.
   DCHECK_GE(kMaxUInt32, locals_.Size());
-  buffer.write_u32(static_cast<uint32_t>(locals_.Size()));
+  buffer.write_u32v(static_cast<uint32_t>(locals_.Size()));
+  // Start position of the function.
+  buffer.write_u32v(asm_func_start_source_position_);
   buffer.write(asm_offsets_.begin(), asm_offsets_.size());
 }
 

src/wasm/wasm-module-builder.h

@@ -135,6 +135,7 @@ class V8_EXPORT_PRIVATE WasmFunctionBuilder : public ZoneObject {
   void ExportAs(Vector<const char> name);
   void SetName(Vector<const char> name);
   void AddAsmWasmOffset(int call_position, int to_number_position);
+  void SetAsmFunctionStartPosition(int position);
 
   void WriteSignature(ZoneBuffer& buffer) const;
   void WriteExports(ZoneBuffer& buffer) const;
@@ -171,6 +172,7 @@ class V8_EXPORT_PRIVATE WasmFunctionBuilder : public ZoneObject {
   ZoneBuffer asm_offsets_;
   uint32_t last_asm_byte_offset_ = 0;
   uint32_t last_asm_source_position_ = 0;
+  uint32_t asm_func_start_source_position_ = 0;
 };
 
 class WasmTemporary {

test/mjsunit/regress/regress-677685.js

+// Copyright 2017 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.
+
+// Flags: --ignition-staging --stack-size=100
+
+function Module(stdlib) {
+  "use asm";
+
+  var fround = stdlib.Math.fround;
+
+  // f: double -> float
+  function f(a) {
+    a = +a;
+    return fround(a);
+  }
+
+  return { f: f };
+}
+
+var f = Module({ Math: Math }).f;
+
+function runNearStackLimit()  {
+  function g() { try { g(); } catch(e) { f(); } };
+  g();
+}
+
+(function () {
+  function g() {}
+
+  runNearStackLimit(g);
+})();

test/mjsunit/wasm/asm-wasm-stack.js

@@ -16,8 +16,7 @@ function checkPreformattedStack(e, expected_lines) {
   }
 }
 
-function checkFunctionsOnCallsites(e, locations) {
-  var stack = e.stack;
+function printCallsites(stack) {
   print('callsite objects (size ' + stack.length + '):');
   for (var i = 0; i < stack.length; ++i) {
     var s = stack[i];
@@ -25,33 +24,47 @@ function checkFunctionsOnCallsites(e, locations) {
         ' [' + i + '] ' + s.getFunctionName() + ' (' + s.getFileName() + ':' +
         s.getLineNumber() + ':' + s.getColumnNumber() + ')');
   }
-  assertEquals(locations.length, stack.length, 'stack size');
-  for (var i = 0; i < locations.length; ++i) {
+}
+
+function checkCallsiteArray(stack, expected) {
+  assertEquals(expected.length, stack.length, 'stack size');
+  for (var i = 0; i < expected.length; ++i) {
     var cs = stack[i];
     assertMatches('^' + filename + '$', cs.getFileName(), 'file name at ' + i);
-    assertEquals(
-        locations[i][0], cs.getFunctionName(), 'function name at ' + i);
-    assertEquals(locations[i][1], cs.getLineNumber(), 'line number at ' + i);
-    assertEquals(
-        locations[i][2], cs.getColumnNumber(), 'column number at ' + i);
+    assertEquals(expected[i][0], cs.getFunctionName(), 'function name at ' + i);
+    assertEquals(expected[i][1], cs.getLineNumber(), 'line number at ' + i);
+    assertEquals(expected[i][2], cs.getColumnNumber(), 'column number at ' + i);
     assertNotNull(cs.getThis(), 'receiver should be global');
     assertEquals(stack[0].getThis(), cs.getThis(), 'receiver should be global');
   }
 }
 
+function checkFunctionsOnCallsites(e, expected) {
+  printCallsites(e.stack);
+  checkCallsiteArray(e.stack, expected);
+}
+
+function checkTopFunctionsOnCallsites(e, expected) {
+  printCallsites(e.stack);
+  assertTrue(
+      e.stack.length >= expected.length, 'expected at least ' +
+          expected.length + ' callsites, got ' + e.stack.length);
+  checkCallsiteArray(e.stack.slice(0, expected.length), expected);
+}
+
 function throwException() {
   throw new Error('exception from JS');
 }
 
-function generateWasmFromAsmJs(stdlib, foreign, heap) {
+function generateWasmFromAsmJs(stdlib, foreign) {
   'use asm';
   var throwFunc = foreign.throwFunc;
   function callThrow() {
     throwFunc();
   }
   function redirectFun(i) {
-    i = i|0;
-    switch (i|0) {
+    i = i | 0;
+    switch (i | 0) {
       case 0: callThrow(); break;
       case 1: redirectFun(0); break;
       case 2: redirectFun(1); break;
@@ -61,7 +74,8 @@ function generateWasmFromAsmJs(stdlib, foreign, heap) {
 }
 
 (function PreformattedStackTraceFromJS() {
-  var fun = generateWasmFromAsmJs(this, {throwFunc: throwException}, undefined);
+  var fun = generateWasmFromAsmJs(this, {throwFunc: throwException});
+  assertTrue(%IsWasmCode(fun));
   var e = null;
   try {
     fun(0);
@@ -71,11 +85,11 @@ function generateWasmFromAsmJs(stdlib, foreign, heap) {
   assertInstanceof(e, Error, 'exception should have been thrown');
   checkPreformattedStack(e, [
     '^Error: exception from JS$',
-    '^ *at throwException \\(' + filename + ':43:9\\)$',
-    '^ *at callThrow \\(' + filename + ':50:5\\)$',
-    '^ *at redirectFun \\(' + filename + ':55:15\\)$',
-    '^ *at PreformattedStackTraceFromJS \\(' + filename + ':67:5\\)$',
-    '^ *at ' + filename + ':80:3$'
+    '^ *at throwException \\(' + filename + ':56:9\\)$',
+    '^ *at callThrow \\(' + filename + ':63:5\\)$',
+    '^ *at redirectFun \\(' + filename + ':68:15\\)$',
+    '^ *at PreformattedStackTraceFromJS \\(' + filename + ':81:5\\)$',
+    '^ *at ' + filename + ':94:3$'
   ]);
 })();
 
@@ -85,7 +99,8 @@ Error.prepareStackTrace = function(error, frames) {
 };
 
 (function CallsiteObjectsFromJS() {
-  var fun = generateWasmFromAsmJs(this, {throwFunc: throwException}, undefined);
+  var fun = generateWasmFromAsmJs(this, {throwFunc: throwException});
+  assertTrue(%IsWasmCode(fun));
   var e = null;
   try {
     fun(2);
@@ -94,12 +109,40 @@ Error.prepareStackTrace = function(error, frames) {
   }
   assertInstanceof(e, Error, 'exception should have been thrown');
   checkFunctionsOnCallsites(e, [
-    ['throwException', 43, 9],         // --
-    ['callThrow', 50, 5],              // --
-    ['redirectFun', 55, 15],            // --
-    ['redirectFun', 56, 15],            // --
-    ['redirectFun', 57, 15],            // --
-    ['CallsiteObjectsFromJS', 91, 5],  // --
-    [null, 105, 3]
+    ['throwException', 56, 9],          // --
+    ['callThrow', 63, 5],               // --
+    ['redirectFun', 68, 15],            // --
+    ['redirectFun', 69, 15],            // --
+    ['redirectFun', 70, 15],            // --
+    ['CallsiteObjectsFromJS', 106, 5],  // --
+    [null, 120, 3]
+  ]);
+})();
+
+function generateOverflowWasmFromAsmJs() {
+  'use asm';
+  function f(a) {
+    a = a | 0;
+    return f(a) | 0;
+  }
+  return f;
+}
+
+(function StackOverflowPosition() {
+  var fun = generateOverflowWasmFromAsmJs();
+  assertTrue(%IsWasmCode(fun));
+  var e = null;
+  try {
+    fun(2);
+  } catch (ex) {
+    e = ex;
+  }
+  // TODO(wasm): Re-enable the check once 673297 is fixed.
+  //assertInstanceof(e, RangeError, 'RangeError should have been thrown');
+  checkTopFunctionsOnCallsites(e, [
+    ['f', 124, 13],  // --
+    ['f', 126, 12],  // --
+    ['f', 126, 12],  // --
+    ['f', 126, 12]   // --
   ]);
 })();

test/mjsunit/wasm/stack.js

@@ -145,5 +145,13 @@ Error.prepareStackTrace = function(error, frames) {
     fail("expected wasm exception");
   } catch (e) {
     assertEquals("Maximum call stack size exceeded", e.message, "trap reason");
+    assertTrue(e.stack.length >= 4, "expected at least 4 stack entries");
+    verifyStack(e.stack.splice(0, 4), [
+        // isWasm     function  line  pos  file
+        [    true, "recursion",    0,   0, null],
+        [    true, "recursion",    0,   3, null],
+        [    true, "recursion",    0,   3, null],
+        [    true, "recursion",    0,   3, null]
+    ]);
   }
 })();