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Write the section header string table directly to the output stream.

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Instead of accumulating the content in a fragment first, just write it
to the output stream.

Also put it first in the section table, so that we never have to worry
about its index being >= SHN_LORESERVE.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236145 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola
2015-04-29 20:25:24 +00:00
parent b241283669
commit 58a854d447
14 changed files with 134 additions and 124 deletions
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68
lib/MC/ELFObjectWriter.cpp
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@ -247,6 +247,9 @@ class ELFObjectWriter : public MCObjectWriter {
void WriteRelocations(MCAssembler &Asm, const MCAsmLayout &Layout);
void
createSectionHeaderStringTable(MCAssembler &Asm,
std::vector<const MCSectionELF *> &Sections);
void CreateMetadataSections(MCAssembler &Asm, const MCAsmLayout &Layout,
std::vector<const MCSectionELF *> &Sections);
@ -452,10 +455,8 @@ void ELFObjectWriter::WriteHeader(const MCAssembler &Asm,
Write16(NumberOfSections);
// e_shstrndx = Section # of '.shstrtab'
if (ShstrtabIndex >= ELF::SHN_LORESERVE)
Write16(ELF::SHN_XINDEX);
else
Write16(ShstrtabIndex);
assert(ShstrtabIndex < ELF::SHN_LORESERVE);
Write16(ShstrtabIndex);
}
uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &Data,
@ -1372,6 +1373,21 @@ void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm,
}
}
void ELFObjectWriter::createSectionHeaderStringTable(
MCAssembler &Asm, std::vector<const MCSectionELF *> &Sections) {
const MCSectionELF *ShstrtabSection = Sections[ShstrtabIndex - 1];
Asm.getOrCreateSectionData(*ShstrtabSection);
for (MCSectionData &SD : Asm) {
const MCSectionELF &Section =
static_cast<const MCSectionELF &>(SD.getSection());
ShStrTabBuilder.add(Section.getSectionName());
}
ShStrTabBuilder.finalize(StringTableBuilder::ELF);
OS << ShStrTabBuilder.data();
}
void ELFObjectWriter::CreateMetadataSections(
MCAssembler &Asm, const MCAsmLayout &Layout,
std::vector<const MCSectionELF *> &Sections) {
@ -1380,14 +1396,6 @@ void ELFObjectWriter::CreateMetadataSections(
unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
// We construct .shstrtab, .symtab and .strtab in this order to match gnu as.
const MCSectionELF *ShstrtabSection =
Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0);
MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
ShstrtabSD.setAlignment(1);
ShstrtabIndex = Sections.size() + 1;
Sections.push_back(ShstrtabSection);
const MCSectionELF *SymtabSection =
Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
EntrySize, "");
@ -1410,18 +1418,6 @@ void ELFObjectWriter::CreateMetadataSections(
F = new MCDataFragment(&StrtabSD);
F->getContents().append(StrTabBuilder.data().begin(),
StrTabBuilder.data().end());
F = new MCDataFragment(&ShstrtabSD);
// Section header string table.
for (auto it = Asm.begin(), ie = Asm.end(); it != ie; ++it) {
const MCSectionELF &Section =
static_cast<const MCSectionELF&>(it->getSection());
ShStrTabBuilder.add(Section.getSectionName());
}
ShStrTabBuilder.finalize(StringTableBuilder::ELF);
F->getContents().append(ShStrTabBuilder.data().begin(),
ShStrTabBuilder.data().end());
}
void ELFObjectWriter::createIndexedSections(
@ -1430,6 +1426,12 @@ void ELFObjectWriter::createIndexedSections(
SectionIndexMapTy &SectionIndexMap) {
MCContext &Ctx = Asm.getContext();
const MCSectionELF *ShstrtabSection =
Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0);
Sections.push_back(ShstrtabSection);
ShstrtabIndex = Sections.size();
assert(ShstrtabIndex == 1);
// Build the groups
for (const MCSectionData &SD : Asm) {
const MCSectionELF &Section =
@ -1537,9 +1539,7 @@ void ELFObjectWriter::writeSectionHeader(
// Null section first.
uint64_t FirstSectionSize =
(NumSections + 1) >= ELF::SHN_LORESERVE ? NumSections + 1 : 0;
uint32_t FirstSectionLink =
ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0;
WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0);
WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, 0, 0, 0, 0);
for (unsigned i = 0; i < NumSections; ++i) {
const MCSectionELF &Section = *Sections[i];
@ -1576,15 +1576,16 @@ void ELFObjectWriter::WriteObject(MCAssembler &Asm,
CreateMetadataSections(Asm, Layout, Sections);
unsigned NumSections = Asm.size();
unsigned NumSections = Asm.size() + 1;
SectionOffsetsTy SectionOffsets;
// Write out the ELF header ...
WriteHeader(Asm, NumSections + 1);
// ... then the sections ...
for (const MCSectionELF *Section : Sections) {
const MCSectionData &SD = Asm.getOrCreateSectionData(*Section);
SectionOffsets.push_back(std::make_pair(0, 0));
for (auto I = ++Sections.begin(), E = Sections.end(); I != E; ++I) {
const MCSectionData &SD = Asm.getOrCreateSectionData(**I);
uint64_t Padding = OffsetToAlignment(OS.tell(), SD.getAlignment());
WriteZeros(Padding);
@ -1595,6 +1596,13 @@ void ELFObjectWriter::WriteObject(MCAssembler &Asm,
SectionOffsets.push_back(std::make_pair(SecStart, SecEnd));
}
{
uint64_t SecStart = OS.tell();
createSectionHeaderStringTable(Asm, Sections);
uint64_t SecEnd = OS.tell();
SectionOffsets[0] = std::make_pair(SecStart, SecEnd);
}
uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
uint64_t Padding = OffsetToAlignment(OS.tell(), NaturalAlignment);
WriteZeros(Padding);