From: Rui Ueyama <ruiu@google.com>
Date: Tue, 12 Jan 2016 23:28:42 +0000 (+0000)
Subject: COFF: Teach llvm-objdump how to dump DLL forwarder symbols.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=68e634ada892effbd66e5c909cbf706175864dfa;p=llvm

COFF: Teach llvm-objdump how to dump DLL forwarder symbols.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@257539 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/include/llvm/Object/COFF.h b/include/llvm/Object/COFF.h
index 1b0e2e36bd5..3e69c3e6e5d 100644
--- a/include/llvm/Object/COFF.h
+++ b/include/llvm/Object/COFF.h
@@ -858,6 +858,9 @@ public:
   std::error_code getExportRVA(uint32_t &Result) const;
   std::error_code getSymbolName(StringRef &Result) const;
 
+  std::error_code isForwarder(bool &Result) const;
+  std::error_code getForwardTo(StringRef &Result) const;
+
 private:
   const export_directory_table_entry *ExportTable;
   uint32_t Index;
diff --git a/lib/Object/COFFObjectFile.cpp b/lib/Object/COFFObjectFile.cpp
index 1f2111759a0..4cd6aff5f17 100644
--- a/lib/Object/COFFObjectFile.cpp
+++ b/lib/Object/COFFObjectFile.cpp
@@ -1336,6 +1336,30 @@ ExportDirectoryEntryRef::getSymbolName(StringRef &Result) const {
   return std::error_code();
 }
 
+std::error_code ExportDirectoryEntryRef::isForwarder(bool &Result) const {
+  const data_directory *DataEntry;
+  if (auto EC = OwningObject->getDataDirectory(COFF::EXPORT_TABLE, DataEntry))
+    return EC;
+  uint32_t RVA;
+  if (auto EC = getExportRVA(RVA))
+    return EC;
+  uint32_t Begin = DataEntry->RelativeVirtualAddress;
+  uint32_t End = DataEntry->RelativeVirtualAddress + DataEntry->Size;
+  Result = (Begin <= RVA && RVA < End);
+  return std::error_code();
+}
+
+std::error_code ExportDirectoryEntryRef::getForwardTo(StringRef &Result) const {
+  uint32_t RVA;
+  if (auto EC = getExportRVA(RVA))
+    return EC;
+  uintptr_t IntPtr = 0;
+  if (auto EC = OwningObject->getRvaPtr(RVA, IntPtr))
+    return EC;
+  Result = StringRef(reinterpret_cast<const char *>(IntPtr));
+  return std::error_code();
+}
+
 bool ImportedSymbolRef::
 operator==(const ImportedSymbolRef &Other) const {
   return Entry32 == Other.Entry32 && Entry64 == Other.Entry64
diff --git a/tools/llvm-objdump/COFFDump.cpp b/tools/llvm-objdump/COFFDump.cpp
index f286351614a..5d21b3320e7 100644
--- a/tools/llvm-objdump/COFFDump.cpp
+++ b/tools/llvm-objdump/COFFDump.cpp
@@ -358,13 +358,30 @@ static void printExportTable(const COFFObjectFile *Obj) {
     uint32_t RVA;
     if (I->getExportRVA(RVA))
       return;
-    outs() << format("    % 4d %# 8x", Ordinal, RVA);
+    bool IsForwarder;
+    if (I->isForwarder(IsForwarder))
+      return;
+
+    if (IsForwarder) {
+      // Export table entries can be used to re-export symbols that
+      // this COFF file is imported from some DLLs. This is rare.
+      // In most cases IsForwarder is false.
+      outs() << format("    % 4d         ", Ordinal);
+    } else {
+      outs() << format("    % 4d %# 8x", Ordinal, RVA);
+    }
 
     StringRef Name;
     if (I->getSymbolName(Name))
       continue;
     if (!Name.empty())
       outs() << "  " << Name;
+    if (IsForwarder) {
+      StringRef S;
+      if (I->getForwardTo(S))
+        return;
+      outs() << " (forwarded to " << S << ")";
+    }
     outs() << "\n";
   }
 }