Do not assume .idata is zero-initialized.

rui314 · rui314 · commit c310742dc3e5 · 2018-11-30T16:34:56.000Z
We initialize .text section with 0xcc (INT3 instruction), so we need to explicitly write data even if it is zero if it can be in a .text section. If you specify /merge:.rdata=.text, .rdata (which contains .idata) is put to .text, so we need to do this. Fixes https://bugs.llvm.org/show_bug.cgi?id=39826 Differential Revision: https://reviews.llvm.org/D55098 llvm-svn: 348000
diff --git a/lld/COFF/Chunks.cpp b/lld/COFF/Chunks.cpp
@@ -619,6 +619,7 @@ uint32_t CommonChunk::getOutputCharacteristics() const {
 
 void StringChunk::writeTo(uint8_t *Buf) const {
   memcpy(Buf + OutputSectionOff, Str.data(), Str.size());
+  Buf[OutputSectionOff + Str.size()] = '\0';
 }
 
 ImportThunkChunkX64::ImportThunkChunkX64(Defined *S) : ImpSymbol(S) {
diff --git a/lld/COFF/DLL.cpp b/lld/COFF/DLL.cpp
@@ -416,6 +416,8 @@ class AddressTableChunk : public Chunk {
   size_t getSize() const override { return Size * 4; }
 
   void writeTo(uint8_t *Buf) const override {
+    memset(Buf + OutputSectionOff, 0, getSize());
+
     for (const Export &E : Config->Exports) {
       uint8_t *P = Buf + OutputSectionOff + E.Ordinal * 4;
       uint32_t Bit = 0;
diff --git a/lld/test/COFF/export.test b/lld/test/COFF/export.test
@@ -97,3 +97,12 @@ FORWARDER:  Ordinal      RVA  Name
 FORWARDER:        0        0
 FORWARDER:        1   0x1010  exportfn
 FORWARDER:        2           foo (forwarded to kernel32.foobar)
+
+# RUN: lld-link /out:%t.dll /dll %t.obj /merge:.rdata=.text /export:exportfn1 /export:exportfn2
+# RUN: llvm-objdump -p %t.dll | FileCheck -check-prefix=MERGE -match-full-lines %s
+
+MERGE:      DLL name: export.test.tmp.dll
+MERGE:      Ordinal      RVA  Name
+MERGE-NEXT:       0        0
+MERGE-NEXT:       1   0x1008  exportfn1
+MERGE-NEXT:       2   0x1010  exportfn2

Original file line number	Diff line number	Diff line change
`@@ -619,6 +619,7 @@ uint32_t CommonChunk::getOutputCharacteristics() const {`
`619`	`619`
`620`	`620`	`void StringChunk::writeTo(uint8_t *Buf) const {`
`621`	`621`	`memcpy(Buf + OutputSectionOff, Str.data(), Str.size());`
	`622`	`+ Buf[OutputSectionOff + Str.size()] = '\0';`
`622`	`623`	`}`
`623`	`624`
`624`	`625`	`ImportThunkChunkX64::ImportThunkChunkX64(Defined *S) : ImpSymbol(S) {`