Merging r352082:

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r352082 | ruiu | 2019-01-24 20:02:31 +0100 (Thu, 24 Jan 2019) | 15 lines

Fix broken export table if .rdata is merged with .text.

Previously, we assumed that .rdata is zero-filled, so when writing
an COFF import table, we didn't write anything if the data is zero.
That assumption was wrong because .rdata can be merged with .text.
If .rdata is merged with .text, they are initialized with 0xcc which
is a trap instruction.

This patch removes that assumption from code.

Should be merged to 8.0 branch as this is a regression.

Fixes https://bugs.llvm.org/show_bug.cgi?id=39826

Differential Revision: https://reviews.llvm.org/D57168
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llvm-svn: 352135

lld/COFF/DLL.cpp

@@ -47,6 +47,7 @@ class HintNameChunk : public Chunk {
   }
 
   void writeTo(uint8_t *Buf) const override {
+    memset(Buf + OutputSectionOff, 0, getSize());
     write16le(Buf + OutputSectionOff, Hint);
     memcpy(Buf + OutputSectionOff + 2, Name.data(), Name.size());
   }
@@ -63,7 +64,10 @@ class LookupChunk : public Chunk {
   size_t getSize() const override { return Config->Wordsize; }
 
   void writeTo(uint8_t *Buf) const override {
-    write32le(Buf + OutputSectionOff, HintName->getRVA());
+    if (Config->is64())
+      write64le(Buf + OutputSectionOff, HintName->getRVA());
+    else
+      write32le(Buf + OutputSectionOff, HintName->getRVA());
   }
 
   Chunk *HintName;
@@ -99,6 +103,8 @@ class ImportDirectoryChunk : public Chunk {
   size_t getSize() const override { return sizeof(ImportDirectoryTableEntry); }
 
   void writeTo(uint8_t *Buf) const override {
+    memset(Buf + OutputSectionOff, 0, getSize());
+
     auto *E = (coff_import_directory_table_entry *)(Buf + OutputSectionOff);
     E->ImportLookupTableRVA = LookupTab->getRVA();
     E->NameRVA = DLLName->getRVA();
@@ -118,6 +124,10 @@ class NullChunk : public Chunk {
   bool hasData() const override { return false; }
   size_t getSize() const override { return Size; }
 
+  void writeTo(uint8_t *Buf) const override {
+    memset(Buf + OutputSectionOff, 0, Size);
+  }
+
 private:
   size_t Size;
 };
@@ -160,6 +170,8 @@ class DelayDirectoryChunk : public Chunk {
   }
 
   void writeTo(uint8_t *Buf) const override {
+    memset(Buf + OutputSectionOff, 0, getSize());
+
     auto *E = (delay_import_directory_table_entry *)(Buf + OutputSectionOff);
     E->Attributes = 1;
     E->Name = DLLName->getRVA();
@@ -392,6 +404,8 @@ class ExportDirectoryChunk : public Chunk {
   }
 
   void writeTo(uint8_t *Buf) const override {
+    memset(Buf + OutputSectionOff, 0, getSize());
+
     auto *E = (export_directory_table_entry *)(Buf + OutputSectionOff);
     E->NameRVA = DLLName->getRVA();
     E->OrdinalBase = 0;

lld/test/COFF/imports.test

@@ -34,3 +34,16 @@ IMPORT-NEXT:   Symbol: ExitProcess (0)
 IMPORT-NEXT:   Symbol:  (50)
 IMPORT-NEXT:   Symbol: MessageBoxA (1)
 IMPORT-NEXT: }
+
+# RUN: lld-link /out:%t.exe /entry:main /subsystem:console /merge:.rdata=.text \
+# RUN:   %p/Inputs/hello64.obj %p/Inputs/std64.lib /include:ExitProcess
+# RUN: llvm-readobj -coff-imports %t.exe | FileCheck -check-prefix=MERGE %s
+
+MERGE:      Import {
+MERGE-NEXT:   Name: std64.dll
+MERGE-NEXT:   ImportLookupTableRVA: 0x1090
+MERGE-NEXT:   ImportAddressTableRVA: 0x10B0
+MERGE-NEXT:   Symbol: ExitProcess (0)
+MERGE-NEXT:   Symbol:  (50)
+MERGE-NEXT:   Symbol: MessageBoxA (1)
+MERGE-NEXT: }