[lld] r221212 - PECOFF: Use the string table for long section names in EXEs/DLLs
David Majnemer
david.majnemer at gmail.com
Mon Nov 3 16:53:57 PST 2014
Author: majnemer
Date: Mon Nov 3 18:53:57 2014
New Revision: 221212
URL: http://llvm.org/viewvc/llvm-project?rev=221212&view=rev
Log:
PECOFF: Use the string table for long section names in EXEs/DLLs
Normally, PE files have section names of eight characters or less.
However, this is problematic for DWARF because DWARF section names are
things like .debug_aranges.
Instead of truncating the section name, redirect the section name into
the string table.
Differential Revision: http://reviews.llvm.org/D6104
Modified:
lld/trunk/lib/ReaderWriter/PECOFF/WriterPECOFF.cpp
lld/trunk/test/pecoff/long-section-name.test
Modified: lld/trunk/lib/ReaderWriter/PECOFF/WriterPECOFF.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/PECOFF/WriterPECOFF.cpp?rev=221212&r1=221211&r2=221212&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/PECOFF/WriterPECOFF.cpp (original)
+++ lld/trunk/lib/ReaderWriter/PECOFF/WriterPECOFF.cpp Mon Nov 3 18:53:57 2014
@@ -65,6 +65,7 @@ public:
enum Kind {
kindHeader,
kindSection,
+ kindStringTable,
kindAtomChunk
};
@@ -151,6 +152,10 @@ public:
_peHeader.AddressOfEntryPoint = address;
}
+ void setPointerToSymbolTable(uint32_t rva) {
+ _coffHeader.PointerToSymbolTable = rva;
+ }
+
private:
llvm::object::coff_file_header _coffHeader;
PEHeader _peHeader;
@@ -171,6 +176,37 @@ private:
std::vector<SectionChunk *> _sections;
};
+class StringTableChunk : public Chunk {
+public:
+ StringTableChunk() : Chunk(kindStringTable) {}
+
+ static bool classof(const Chunk *c) {
+ return c->getKind() == kindStringTable;
+ }
+
+ uint32_t addSectionName(StringRef sectionName) {
+ if (_stringTable.empty())
+ _stringTable.insert(_stringTable.begin(), 4, 0);
+ uint32_t offset = _stringTable.size();
+ _stringTable.insert(_stringTable.end(), sectionName.begin(),
+ sectionName.end());
+ _stringTable.push_back('\0');
+ return offset;
+ }
+
+ uint64_t size() const override { return _stringTable.size(); }
+
+ void write(uint8_t *buffer) override {
+ if (_stringTable.empty())
+ return;
+ *reinterpret_cast<ulittle32_t *>(_stringTable.data()) = _stringTable.size();
+ std::memcpy(buffer, _stringTable.data(), _stringTable.size());
+ }
+
+private:
+ std::vector<char> _stringTable;
+};
+
class SectionChunk : public Chunk {
public:
uint64_t onDiskSize() const override {
@@ -191,15 +227,20 @@ public:
uint64_t getVirtualAddress() { return _virtualAddress; }
virtual void setVirtualAddress(uint32_t rva) { _virtualAddress = rva; }
+ uint32_t getStringTableOffset() const { return _stringTableOffset; }
+ void setStringTableOffset(uint32_t offset) { _stringTableOffset = offset; }
+
protected:
SectionChunk(Kind kind, StringRef sectionName, uint32_t characteristics)
: Chunk(kind), _sectionName(sectionName),
- _characteristics(characteristics), _virtualAddress(0) {}
+ _characteristics(characteristics), _virtualAddress(0),
+ _stringTableOffset(0) {}
private:
StringRef _sectionName;
const uint32_t _characteristics;
uint64_t _virtualAddress;
+ uint32_t _stringTableOffset;
};
/// An AtomChunk represents a section containing atoms.
@@ -750,15 +791,15 @@ llvm::object::coff_section
SectionHeaderTableChunk::createSectionHeader(SectionChunk *chunk) {
llvm::object::coff_section header;
- // Section name must be equal to or less than 8 characters in the
- // executable. Longer names will be truncated.
+ // We have extended the COFF specification by allowing section names to be
+ // greater than eight characters. We achieve this by adding the section names
+ // to the string table. Binutils' linker, ld, performs the same trick.
StringRef sectionName = chunk->getSectionName();
-
- // Name field must be NUL-padded. If the name is exactly 8 byte long,
- // there's no terminating NUL.
- std::memset(header.Name, 0, sizeof(header.Name));
- std::strncpy(header.Name, sectionName.data(),
- std::min(sizeof(header.Name), sectionName.size()));
+ std::memset(header.Name, 0, llvm::COFF::NameSize);
+ if (uint32_t stringTableOffset = chunk->getStringTableOffset())
+ sprintf(header.Name, "/%u", stringTableOffset);
+ else
+ std::strncpy(header.Name, sectionName.data(), sectionName.size());
uint32_t characteristics = chunk->getCharacteristics();
header.VirtualSize = chunk->size();
@@ -873,7 +914,8 @@ private:
void addChunk(Chunk *chunk);
void addSectionChunk(std::unique_ptr<SectionChunk> chunk,
- SectionHeaderTableChunk *table);
+ SectionHeaderTableChunk *table,
+ StringTableChunk *stringTable);
void setImageSizeOnDisk();
uint64_t
calcSectionSize(llvm::COFF::SectionCharacteristics sectionType) const;
@@ -974,10 +1016,12 @@ void PECOFFWriter::build(const File &lin
auto *peHeader = new PEHeaderChunk<PEHeader>(_ctx);
auto *dataDirectory = new DataDirectoryChunk();
auto *sectionTable = new SectionHeaderTableChunk();
+ auto *stringTable = new StringTableChunk();
addChunk(dosStub);
addChunk(peHeader);
addChunk(dataDirectory);
addChunk(sectionTable);
+ addChunk(stringTable);
// Create sections and add the atoms to them.
for (auto i : atoms) {
@@ -986,7 +1030,7 @@ void PECOFFWriter::build(const File &lin
std::unique_ptr<SectionChunk> section(
new AtomChunk(_ctx, sectionName, contents));
if (section->size() > 0)
- addSectionChunk(std::move(section), sectionTable);
+ addSectionChunk(std::move(section), sectionTable, stringTable);
}
// Build atom to its RVA map.
@@ -1001,13 +1045,18 @@ void PECOFFWriter::build(const File &lin
std::unique_ptr<SectionChunk> baseReloc(new BaseRelocChunk(_chunks, _ctx));
if (baseReloc->size()) {
SectionChunk &ref = *baseReloc;
- addSectionChunk(std::move(baseReloc), sectionTable);
+ addSectionChunk(std::move(baseReloc), sectionTable, stringTable);
dataDirectory->setField(DataDirectoryIndex::BASE_RELOCATION_TABLE,
ref.getVirtualAddress(), ref.size());
}
}
setImageSizeOnDisk();
+ // N.B. Currently released versions of dumpbin do not appropriately handle
+ // symbol tables which NumberOfSymbols set to zero but a non-zero
+ // PointerToSymbolTable.
+ if (stringTable->size())
+ peHeader->setPointerToSymbolTable(stringTable->fileOffset());
for (std::unique_ptr<Chunk> &chunk : _chunks) {
SectionChunk *section = dyn_cast<SectionChunk>(chunk.get());
@@ -1180,12 +1229,19 @@ void PECOFFWriter::addChunk(Chunk *chunk
}
void PECOFFWriter::addSectionChunk(std::unique_ptr<SectionChunk> chunk,
- SectionHeaderTableChunk *table) {
+ SectionHeaderTableChunk *table,
+ StringTableChunk *stringTable) {
SectionChunk &ref = *chunk;
_chunks.push_back(std::move(chunk));
table->addSection(&ref);
_numSections++;
+ StringRef sectionName = ref.getSectionName();
+ if (sectionName.size() > llvm::COFF::NameSize) {
+ uint32_t stringTableOffset = stringTable->addSectionName(sectionName);
+ ref.setStringTableOffset(stringTableOffset);
+ }
+
// Compute and set the starting address of sections when loaded in
// memory. They are different from positions on disk because sections need
// to be sector-aligned on disk but page-aligned in memory.
Modified: lld/trunk/test/pecoff/long-section-name.test
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/pecoff/long-section-name.test?rev=221212&r1=221211&r2=221212&view=diff
==============================================================================
--- lld/trunk/test/pecoff/long-section-name.test (original)
+++ lld/trunk/test/pecoff/long-section-name.test Mon Nov 3 18:53:57 2014
@@ -4,4 +4,4 @@
# RUN: /merge:.text=.longsectionname -- %t.obj
# RUN: llvm-readobj -sections %t.exe | FileCheck %s
-CHECK: Name: .longsec (2E 6C 6F 6E 67 73 65 63)
+CHECK: Name: .longsectionname (2F 34 00 00 00 00 00 00)
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