[WebAssembly] Add support for init functions linking metadata

Summary:
This change lays the groundwork lowering of @llvm.global_ctors
and @llvm.global_dtors for the wasm object format.  Some parts
of this patch are subset of: https://reviews.llvm.org/D40759

See https://github.com/WebAssembly/tool-conventions/issues/25

Subscribers: jfb, dschuff, jgravelle-google, aheejin, sunfish

Differential Revision: https://reviews.llvm.org/D41208

llvm-svn: 320742

1 files changed, 20 insertions, 1 deletions

diff --git a/llvm/lib/Object/WasmObjectFile.cpp b/llvm/lib/Object/WasmObjectFile.cpp
index 8d4c15a..677fccc 100644
--- a/llvm/lib/Object/WasmObjectFile.cpp
+++ b/llvm/lib/Object/WasmObjectFile.cpp
@@ -398,6 +398,21 @@ Error WasmObjectFile::parseLinkingSection(const uint8_t *Ptr,
       }
       break;
     }
+    case wasm::WASM_INIT_FUNCS: {
+      uint32_t Count = readVaruint32(Ptr);
+      LinkingData.InitFunctions.reserve(Count);
+      for (uint32_t i = 0; i < Count; i++) {
+        wasm::WasmInitFunc Init;
+        Init.Priority = readVaruint32(Ptr);
+        Init.FunctionIndex = readVaruint32(Ptr);
+        if (!isValidFunctionIndex(Init.FunctionIndex))
+          return make_error<GenericBinaryError>("Invalid function index: " +
+                                                    Twine(Init.FunctionIndex),
+                                                object_error::parse_failed);
+        LinkingData.InitFunctions.emplace_back(Init);
+      }
+      break;
+    }
     default:
       Ptr += Size;
       break;
@@ -656,9 +671,13 @@ Error WasmObjectFile::parseExportSection(const uint8_t *Ptr, const uint8_t *End)
   return Error::success();
 }
 
+bool WasmObjectFile::isValidFunctionIndex(uint32_t Index) const {
+  return Index < FunctionTypes.size() + NumImportedFunctions;
+}
+
 Error WasmObjectFile::parseStartSection(const uint8_t *Ptr, const uint8_t *End) {
   StartFunction = readVaruint32(Ptr);
-  if (StartFunction >= FunctionTypes.size())
+  if (!isValidFunctionIndex(StartFunction))
     return make_error<GenericBinaryError>("Invalid start function",
                                           object_error::parse_failed);
   return Error::success();