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Use the ability to pwrite to simplify the ELF writer.

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Now we don't have to do 2 synchronized passes to compute offsets and then
write the file.

This also includes a fix for the corner case of seeking in /dev/null. It
is not an error, but on some systems (Linux) the returned offset is
always 0. An error is signaled by returning -1. This is checked by
the existing tests now that "clang -o /dev/null ..." seeks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234952 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola 2015-04-14 22:54:16 +00:00
parent c98092e28d
commit 83ed6b7814
2 changed files with 35 additions and 48 deletions
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81
lib/MC/ELFObjectWriter.cpp
View File

@ -92,14 +92,11 @@ class ELFObjectWriter : public MCObjectWriter {
static bool isLocal(const MCSymbolData &Data, bool isUsedInReloc);
static bool IsELFMetaDataSection(const MCSectionData &SD);
static uint64_t DataSectionSize(const MCSectionData &SD);
static uint64_t GetSectionFileSize(const MCAsmLayout &Layout,
const MCSectionData &SD);
static uint64_t GetSectionAddressSize(const MCAsmLayout &Layout,
const MCSectionData &SD);
void WriteDataSectionData(MCAssembler &Asm,
const MCAsmLayout &Layout,
const MCSectionELF &Section);
void writeDataSectionData(MCAssembler &Asm, const MCAsmLayout &Layout,
const MCSectionData &SD);
/// Helper struct for containing some precomputed information on symbols.
struct ELFSymbolData {
@ -201,7 +198,6 @@ class ELFObjectWriter : public MCObjectWriter {
}
void WriteHeader(const MCAssembler &Asm,
uint64_t SectionHeaderOffset,
unsigned NumberOfSections);
void WriteSymbol(SymbolTableWriter &Writer, ELFSymbolData &MSD,
@ -409,7 +405,6 @@ ELFObjectWriter::~ELFObjectWriter()
// Emit the ELF header.
void ELFObjectWriter::WriteHeader(const MCAssembler &Asm,
uint64_t SectionHeaderOffset,
unsigned NumberOfSections) {
// ELF Header
// ----------
@ -443,7 +438,7 @@ void ELFObjectWriter::WriteHeader(const MCAssembler &Asm,
Write32(ELF::EV_CURRENT); // e_version
WriteWord(0); // e_entry, no entry point in .o file
WriteWord(0); // e_phoff, no program header for .o
WriteWord(SectionHeaderOffset); // e_shoff = sec hdr table off in bytes
WriteWord(0); // e_shoff = sec hdr table off in bytes
// e_flags = whatever the target wants
Write32(Asm.getELFHeaderEFlags());
@ -1532,13 +1527,6 @@ uint64_t ELFObjectWriter::DataSectionSize(const MCSectionData &SD) {
return Ret;
}
uint64_t ELFObjectWriter::GetSectionFileSize(const MCAsmLayout &Layout,
const MCSectionData &SD) {
if (IsELFMetaDataSection(SD))
return DataSectionSize(SD);
return Layout.getSectionFileSize(&SD);
}
uint64_t ELFObjectWriter::GetSectionAddressSize(const MCAsmLayout &Layout,
const MCSectionData &SD) {
if (IsELFMetaDataSection(SD))
@ -1546,14 +1534,9 @@ uint64_t ELFObjectWriter::GetSectionAddressSize(const MCAsmLayout &Layout,
return Layout.getSectionAddressSize(&SD);
}
void ELFObjectWriter::WriteDataSectionData(MCAssembler &Asm,
void ELFObjectWriter::writeDataSectionData(MCAssembler &Asm,
const MCAsmLayout &Layout,
const MCSectionELF &Section) {
const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
uint64_t Padding = OffsetToAlignment(OS.tell(), SD.getAlignment());
WriteZeros(Padding);
const MCSectionData &SD) {
if (IsELFMetaDataSection(SD)) {
for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
++i) {
@ -1655,45 +1638,49 @@ void ELFObjectWriter::WriteObject(MCAssembler &Asm,
const_cast<MCAsmLayout&>(Layout),
SectionIndexMap);
uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
uint64_t HeaderSize = is64Bit() ? sizeof(ELF::Elf64_Ehdr) :
sizeof(ELF::Elf32_Ehdr);
uint64_t FileOff = HeaderSize;
std::vector<const MCSectionELF*> Sections;
ComputeSectionOrder(Asm, Sections);
unsigned NumSections = Sections.size();
SectionOffsetMapTy SectionOffsetMap;
for (unsigned i = 0; i < NumSections; ++i) {
const MCSectionELF &Section = *Sections[i];
const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
// Remember the offset into the file for this section.
SectionOffsetMap[&Section] = FileOff;
// Get the size of the section in the output file (including padding).
FileOff += GetSectionFileSize(Layout, SD);
}
FileOff = RoundUpToAlignment(FileOff, NaturalAlignment);
const unsigned SectionHeaderOffset = FileOff;
// Write out the ELF header ...
WriteHeader(Asm, SectionHeaderOffset, NumSections + 1);
WriteHeader(Asm, NumSections + 1);
// ... then the sections ...
for (unsigned i = 0; i < NumSections; ++i)
WriteDataSectionData(Asm, Layout, *Sections[i]);
for (unsigned i = 0; i < NumSections; ++i) {
const MCSectionELF &Section = *Sections[i];
const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
uint64_t Padding = OffsetToAlignment(OS.tell(), SD.getAlignment());
WriteZeros(Padding);
// Remember the offset into the file for this section.
SectionOffsetMap[&Section] = OS.tell();
writeDataSectionData(Asm, Layout, SD);
}
uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
uint64_t Padding = OffsetToAlignment(OS.tell(), NaturalAlignment);
WriteZeros(Padding);
const unsigned SectionHeaderOffset = OS.tell();
// ... then the section header table ...
writeSectionHeader(Asm, GroupMap, Layout, SectionIndexMap, SectionOffsetMap);
if (is64Bit()) {
uint64_t Val = SectionHeaderOffset;
if (sys::IsLittleEndianHost != IsLittleEndian)
sys::swapByteOrder(Val);
OS.pwrite(reinterpret_cast<char *>(&Val), sizeof(Val),
offsetof(ELF::Elf64_Ehdr, e_shoff));
} else {
uint32_t Val = SectionHeaderOffset;
if (sys::IsLittleEndianHost != IsLittleEndian)
sys::swapByteOrder(Val);
OS.pwrite(reinterpret_cast<char *>(&Val), sizeof(Val),
offsetof(ELF::Elf32_Ehdr, e_shoff));
}
}
bool ELFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(

2
lib/Support/raw_ostream.cpp
View File

@ -625,7 +625,7 @@ void raw_fd_ostream::close() {
uint64_t raw_fd_ostream::seek(uint64_t off) {
flush();
pos = ::lseek(FD, off, SEEK_SET);
if (pos != off)
if (pos == (uint64_t)-1)
error_detected();
return pos;
}