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[WebAssembly] Fix for use of uninitialized member in WasmObjectWriter.cpp

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Currently, section indices may be passed uninitialized by value if
writing the section fails. Removes section indices form class
initialization and returns them from the write{Code,Data}Section
function calls instead.

Patch by Gui Andrade!

Differential Revision: https://reviews.llvm.org/D81702
This commit is contained in:
Sam Clegg 2020-06-23 14:59:18 -07:00
parent 5f2e7e7476
commit 28b30ccf89
1 changed files with 13 additions and 16 deletions
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29
lib/MC/WasmObjectWriter.cpp
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@ -224,11 +224,8 @@ class WasmObjectWriter : public MCObjectWriter {
// Relocations for fixing up references in the code section.
std::vector<WasmRelocationEntry> CodeRelocations;
uint32_t CodeSectionIndex;
// Relocations for fixing up references in the data section.
std::vector<WasmRelocationEntry> DataRelocations;
uint32_t DataSectionIndex;
// Index values to use for fixing up call_indirect type indices.
// Maps function symbols to the index of the type of the function
@ -335,9 +332,9 @@ private:
void writeExportSection(ArrayRef<wasm::WasmExport> Exports);
void writeElemSection(ArrayRef<uint32_t> TableElems);
void writeDataCountSection();
void writeCodeSection(const MCAssembler &Asm, const MCAsmLayout &Layout,
ArrayRef<WasmFunction> Functions);
void writeDataSection(const MCAsmLayout &Layout);
uint32_t writeCodeSection(const MCAssembler &Asm, const MCAsmLayout &Layout,
ArrayRef<WasmFunction> Functions);
uint32_t writeDataSection(const MCAsmLayout &Layout);
void writeEventSection(ArrayRef<wasm::WasmEventType> Events);
void writeGlobalSection(ArrayRef<wasm::WasmGlobal> Globals);
void writeRelocSection(uint32_t SectionIndex, StringRef Name,
@ -894,15 +891,14 @@ void WasmObjectWriter::writeDataCountSection() {
endSection(Section);
}
void WasmObjectWriter::writeCodeSection(const MCAssembler &Asm,
const MCAsmLayout &Layout,
ArrayRef<WasmFunction> Functions) {
uint32_t WasmObjectWriter::writeCodeSection(const MCAssembler &Asm,
const MCAsmLayout &Layout,
ArrayRef<WasmFunction> Functions) {
if (Functions.empty())
return;
return 0;
SectionBookkeeping Section;
startSection(Section, wasm::WASM_SEC_CODE);
CodeSectionIndex = Section.Index;
encodeULEB128(Functions.size(), W.OS);
@ -922,15 +918,15 @@ void WasmObjectWriter::writeCodeSection(const MCAssembler &Asm,
applyRelocations(CodeRelocations, Section.ContentsOffset, Layout);
endSection(Section);
return Section.Index;
}
void WasmObjectWriter::writeDataSection(const MCAsmLayout &Layout) {
uint32_t WasmObjectWriter::writeDataSection(const MCAsmLayout &Layout) {
if (DataSegments.empty())
return;
return 0;
SectionBookkeeping Section;
startSection(Section, wasm::WASM_SEC_DATA);
DataSectionIndex = Section.Index;
encodeULEB128(DataSegments.size(), W.OS); // count
@ -952,6 +948,7 @@ void WasmObjectWriter::writeDataSection(const MCAsmLayout &Layout) {
applyRelocations(DataRelocations, Section.ContentsOffset, Layout);
endSection(Section);
return Section.Index;
}
void WasmObjectWriter::writeRelocSection(
@ -1698,8 +1695,8 @@ uint64_t WasmObjectWriter::writeObject(MCAssembler &Asm,
writeExportSection(Exports);
writeElemSection(TableElems);
writeDataCountSection();
writeCodeSection(Asm, Layout, Functions);
writeDataSection(Layout);
uint32_t CodeSectionIndex = writeCodeSection(Asm, Layout, Functions);
uint32_t DataSectionIndex = writeDataSection(Layout);
for (auto &CustomSection : CustomSections)
writeCustomSection(CustomSection, Asm, Layout);
writeLinkingMetaDataSection(SymbolInfos, InitFuncs, Comdats);