[wasm] Restrict exception section according to spec.

The placement of the exceptipon section is by now restricted to be in
between the Global and the Import section. This changes our validation
to check this stricter requirement now.

R=clemensh@chromium.org
TEST=unittests/WasmModuleVerifyTest
BUG=v8:8091

Change-Id: Ib3ea625fd4df93bffda47ced09e6969159f7ac70
Reviewed-on: https://chromium-review.googlesource.com/c/1356504Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57962}

src/wasm/module-decoder.cc

@@ -360,7 +360,7 @@ class ModuleDecoderImpl : public Decoder {
         return CheckSectionOrder(section_code, kElementSectionCode,
                                  kCodeSectionCode);
       case kExceptionSectionCode:
-        return CheckSectionOrder(section_code, kImportSectionCode,
+        return CheckSectionOrder(section_code, kGlobalSectionCode,
                                  kExportSectionCode);
       default:
         UNREACHABLE();

test/mjsunit/wasm/wasm-constants.js

@@ -64,7 +64,7 @@ let kStartSectionCode = 8;       // Start function declaration
 let kElementSectionCode = 9;     // Elements section
 let kCodeSectionCode = 10;       // Function code
 let kDataSectionCode = 11;       // Data segments
-let kExceptionSectionCode = 12;  // Exception section (must appear before code section)
+let kExceptionSectionCode = 12;  // Exception section (between Global & Export)
 
 // Name section types
 let kModuleNameCode = 0;

test/unittests/wasm/module-decoder-unittest.cc

@@ -576,26 +576,26 @@ TEST_F(WasmModuleVerifyTest, ExceptionSectionAfterExport) {
                 "The Exception section must appear before the Export section");
 }
 
-TEST_F(WasmModuleVerifyTest, ExceptionSectionBeforeImport) {
+TEST_F(WasmModuleVerifyTest, ExceptionSectionBeforeGlobal) {
   static const byte data[] = {SECTION(Exception, ENTRY_COUNT(0)),
-                              SECTION(Import, ENTRY_COUNT(0))};
+                              SECTION(Global, ENTRY_COUNT(0))};
   FAIL_IF_NO_EXPERIMENTAL_EH(data);
 
   WASM_FEATURE_SCOPE(eh);
   ModuleResult result = DecodeModule(data, data + sizeof(data));
-  EXPECT_NOT_OK(result, "unexpected section: Import");
+  EXPECT_NOT_OK(result, "unexpected section: Global");
 }
 
-TEST_F(WasmModuleVerifyTest, ExceptionSectionAfterTypeBeforeImport) {
-  STATIC_ASSERT(kTypeSectionCode + 1 == kImportSectionCode);
-  static const byte data[] = {SECTION(Type, ENTRY_COUNT(0)),
+TEST_F(WasmModuleVerifyTest, ExceptionSectionAfterMemoryBeforeGlobal) {
+  STATIC_ASSERT(kMemorySectionCode + 1 == kGlobalSectionCode);
+  static const byte data[] = {SECTION(Memory, ENTRY_COUNT(0)),
                               SECTION(Exception, ENTRY_COUNT(0)),
-                              SECTION(Import, ENTRY_COUNT(0))};
+                              SECTION(Global, ENTRY_COUNT(0))};
   FAIL_IF_NO_EXPERIMENTAL_EH(data);
 
   WASM_FEATURE_SCOPE(eh);
   ModuleResult result = DecodeModule(data, data + sizeof(data));
-  EXPECT_NOT_OK(result, "unexpected section: Import");
+  EXPECT_NOT_OK(result, "unexpected section: Global");
 }
 
 TEST_F(WasmModuleVerifyTest, ExceptionImport) {