[PATCH] D57168: Fix broken export table if .rdata is merged with .text.

[Rui Ueyama via Phabricator via llvm-commits]

ruiu created this revision.
ruiu added reviewers: rnk, llvm-commits.

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


https://reviews.llvm.org/D57168

Files:
  lld/COFF/DLL.cpp
  lld/test/COFF/imports.test


Index: lld/test/COFF/imports.test
===================================================================
--- lld/test/COFF/imports.test
+++ lld/test/COFF/imports.test
@@ -34,3 +34,16 @@
 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: }
Index: lld/COFF/DLL.cpp
===================================================================
--- lld/COFF/DLL.cpp
+++ lld/COFF/DLL.cpp
@@ -46,6 +46,7 @@
   }
 
   void writeTo(uint8_t *Buf) const override {
+    memset(Buf + OutputSectionOff, 0, getSize());
     write16le(Buf + OutputSectionOff, Hint);
     memcpy(Buf + OutputSectionOff + 2, Name.data(), Name.size());
   }
@@ -62,7 +63,10 @@
   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;
@@ -98,6 +102,8 @@
   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();
@@ -117,6 +123,10 @@
   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;
 };
@@ -159,6 +169,8 @@
   }
 
   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();
@@ -391,6 +403,8 @@
   }
 
   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;
@@ -458,6 +472,8 @@
   size_t getSize() const override { return Size * 2; }
 
   void writeTo(uint8_t *Buf) const override {
+    memset(Buf + OutputSectionOff, 0, getSize());
+
     uint8_t *P = Buf + OutputSectionOff;
     for (Export &E : Config->Exports) {
       if (E.Noname)


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