llvm-mc/Mach-O: Add section padding where needed (to align the next section).
Also, simplify some of Mach-O writer code which can now use section addresses.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@80067 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MCAssembler.cpp b/lib/MC/MCAssembler.cpp
index 13c1932..26f6d5c 100644
--- a/lib/MC/MCAssembler.cpp
+++ b/lib/MC/MCAssembler.cpp
@@ -217,7 +217,7 @@
WriteString(Section.getSectionName(), 16);
WriteString(Section.getSegmentName(), 16);
Write32(SD.getAddress()); // address
- Write32(SD.getFileSize()); // size
+ Write32(SD.getSize()); // size
Write32(FileOffset);
assert(isPowerOf2_32(SD.getAlignment()) && "Invalid alignment!");
@@ -507,11 +507,6 @@
if (NumSymbols)
ComputeSymbolTable(Asm, StringTable, LocalSymbolData, ExternalSymbolData,
UndefinedSymbolData);
-
- // Compute the file offsets for all the sections in advance, so that we can
- // write things out in order.
- SmallVector<uint64_t, 16> SectionFileOffsets;
- SectionFileOffsets.resize(NumSections);
// The section data starts after the header, the segment load command (and
// section headers) and the symbol table.
@@ -525,27 +520,22 @@
LoadCommandsSize += SymtabLoadCommandSize + DysymtabLoadCommandSize;
}
- uint64_t FileOffset = Header32Size + LoadCommandsSize;
- uint64_t SectionDataStartOffset = FileOffset;
+ uint64_t SectionDataStart = Header32Size + LoadCommandsSize;
+ uint64_t SectionDataEnd = SectionDataStart;
uint64_t SectionDataSize = 0;
- unsigned Index = 0;
- for (MCAssembler::iterator it = Asm.begin(),
- ie = Asm.end(); it != ie; ++it, ++Index) {
- SectionFileOffsets[Index] = FileOffset;
- FileOffset += it->getFileSize();
- SectionDataSize += it->getFileSize();
+ if (!Asm.getSectionList().empty()) {
+ MCSectionData &SD = Asm.getSectionList().back();
+ SectionDataSize = SD.getAddress() + SD.getSize();
+ SectionDataEnd = SectionDataStart + SD.getAddress() + SD.getFileSize();
}
// Write the prolog, starting with the header and load command...
WriteHeader32(NumLoadCommands, LoadCommandsSize);
- WriteSegmentLoadCommand32(NumSections, SectionDataStartOffset,
- SectionDataSize);
+ WriteSegmentLoadCommand32(NumSections, SectionDataStart, SectionDataSize);
// ... and then the section headers.
- Index = 0;
- for (MCAssembler::iterator it = Asm.begin(),
- ie = Asm.end(); it != ie; ++it, ++Index)
- WriteSection32(*it, SectionFileOffsets[Index]);
+ for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
+ WriteSection32(*it, SectionDataStart + it->getAddress());
// Write the symbol table load command, if used.
if (NumSymbols) {
@@ -563,11 +553,10 @@
// If used, the indirect symbols are written after the section data.
if (NumIndirectSymbols)
- IndirectSymbolOffset = SectionDataStartOffset + SectionDataSize;
+ IndirectSymbolOffset = SectionDataEnd;
// The symbol table is written after the indirect symbol data.
- uint64_t SymbolTableOffset =
- SectionDataStartOffset + SectionDataSize + IndirectSymbolSize;
+ uint64_t SymbolTableOffset = SectionDataEnd + IndirectSymbolSize;
// The string table is written after symbol table.
uint64_t StringTableOffset =
@@ -675,6 +664,7 @@
: Section(_Section),
Alignment(1),
Address(~UINT64_C(0)),
+ Size(~UINT64_C(0)),
FileSize(~UINT64_C(0))
{
if (A)
@@ -701,26 +691,24 @@
MCAssembler::~MCAssembler() {
}
-void MCAssembler::LayoutSection(MCSectionData &SD) {
- uint64_t Offset = 0;
+void MCAssembler::LayoutSection(MCSectionData &SD, unsigned NextAlign) {
+ uint64_t Address = SD.getAddress();
for (MCSectionData::iterator it = SD.begin(), ie = SD.end(); it != ie; ++it) {
MCFragment &F = *it;
- F.setOffset(Offset);
+ F.setOffset(Address - SD.getAddress());
// Evaluate fragment size.
switch (F.getKind()) {
case MCFragment::FT_Align: {
MCAlignFragment &AF = cast<MCAlignFragment>(F);
- uint64_t AlignedOffset = RoundUpToAlignment(Offset, AF.getAlignment());
- uint64_t PaddingBytes = AlignedOffset - Offset;
-
- if (PaddingBytes > AF.getMaxBytesToEmit())
+ uint64_t Size = RoundUpToAlignment(Address, AF.getAlignment()) - Address;
+ if (Size > AF.getMaxBytesToEmit())
AF.setFileSize(0);
else
- AF.setFileSize(PaddingBytes);
+ AF.setFileSize(Size);
break;
}
@@ -735,22 +723,24 @@
if (!OF.getOffset().isAbsolute())
llvm_unreachable("FIXME: Not yet implemented!");
uint64_t OrgOffset = OF.getOffset().getConstant();
+ uint64_t Offset = Address - SD.getAddress();
// FIXME: We need a way to communicate this error.
if (OrgOffset < Offset)
llvm_report_error("invalid .org offset '" + Twine(OrgOffset) +
- "' (section offset '" + Twine(Offset) + "'");
+ "' (at offset '" + Twine(Offset) + "'");
F.setFileSize(OrgOffset - Offset);
break;
}
}
- Offset += F.getFileSize();
+ Address += F.getFileSize();
}
- // FIXME: Pad section?
- SD.setFileSize(Offset);
+ // Set the section sizes.
+ SD.setSize(Address - SD.getAddress());
+ SD.setFileSize(RoundUpToAlignment(Address, NextAlign) - SD.getAddress());
}
/// WriteFileData - Write the \arg F data to the output file.
@@ -836,16 +826,32 @@
ie = SD.end(); it != ie; ++it)
WriteFileData(OS, *it, MOW);
+ // Add section padding.
+ assert(SD.getFileSize() >= SD.getSize() && "Invalid section sizes!");
+ MOW.WriteZeros(SD.getFileSize() - SD.getSize());
+
assert(OS.tell() - Start == SD.getFileSize());
}
void MCAssembler::Finish() {
// Layout the sections and fragments.
uint64_t Address = 0;
- for (iterator it = begin(), ie = end(); it != ie; ++it) {
- it->setAddress(Address);
- LayoutSection(*it);
- Address += it->getFileSize();
+ for (iterator it = begin(), ie = end(); it != ie;) {
+ MCSectionData &SD = *it;
+
+ // Select the amount of padding alignment we need, based on either the next
+ // sections alignment or the default alignment.
+ //
+ // FIXME: This should probably match the native word size.
+ unsigned NextAlign = 4;
+ ++it;
+ if (it != ie)
+ NextAlign = it->getAlignment();
+
+ // Layout the section fragments and its size.
+ SD.setAddress(Address);
+ LayoutSection(SD, NextAlign);
+ Address += SD.getFileSize();
}
// Write the object file.