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llvm-mc/Mach-O: Sketch symbol table support.

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- The only .s syntax this honors right now is emitting labels, and some parts
   of the symbol table generation are wrong or faked.

 - This is enough to get nm to report such symbols... incorrectly, but still.

Also, fixed byte emission to extend the previous fragment if possible.

llvm-svn: 79739
This commit is contained in:
Daniel Dunbar 2009-08-22 10:13:24 +00:00
parent eef8b8ed05
commit d22c0d4d49
3 changed files with 296 additions and 38 deletions
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58
include/llvm/MC/MCAssembler.h
View File

@ -64,7 +64,7 @@ public:
// FIXME: This should be abstract, fix sentinel.
virtual uint64_t getMaxFileSize() const {
assert(0 && "Invalid getMaxFileSize call !");
assert(0 && "Invalid getMaxFileSize call!");
return 0;
};
@ -270,7 +270,6 @@ public:
unsigned getAlignment() const { return Alignment; }
void setAlignment(unsigned Value) { Alignment = Value; }
/// @name Section List Access
/// @{
@ -285,6 +284,8 @@ public:
size_t size() const { return Fragments.size(); }
bool empty() const { return Fragments.empty(); }
/// @}
/// @name Assembler Backend Support
/// @{
@ -300,13 +301,49 @@ public:
/// @}
};
// FIXME: Same concerns as with SectionData.
class MCSymbolData : public ilist_node<MCSymbolData> {
public:
MCSymbol &Symbol;
/// Fragment - The fragment this symbol's value is relative to, if any.
MCFragment *Fragment;
/// Offset - The offset to apply to the fragment address to form this symbol's
/// value.
uint64_t Offset;
public:
// Only for use as sentinel.
MCSymbolData();
MCSymbolData(MCSymbol &_Symbol, MCFragment *_Fragment, uint64_t _Offset,
MCAssembler *A = 0);
/// @name Accessors
/// @{
MCSymbol &getSymbol() const { return Symbol; }
MCFragment *getFragment() const { return Fragment; }
void setFragment(MCFragment *Value) { Fragment = Value; }
uint64_t getOffset() const { return Offset; }
void setOffset(uint64_t Value) { Offset = Value; }
/// @}
};
class MCAssembler {
public:
typedef iplist<MCSectionData> SectionDataListType;
typedef iplist<MCSymbolData> SymbolDataListType;
typedef SectionDataListType::const_iterator const_iterator;
typedef SectionDataListType::iterator iterator;
typedef SymbolDataListType::const_iterator const_symbol_iterator;
typedef SymbolDataListType::iterator symbol_iterator;
private:
MCAssembler(const MCAssembler&); // DO NOT IMPLEMENT
void operator=(const MCAssembler&); // DO NOT IMPLEMENT
@ -315,6 +352,8 @@ private:
iplist<MCSectionData> Sections;
iplist<MCSymbolData> Symbols;
private:
/// LayoutSection - Assign offsets and sizes to the fragments in the section
/// \arg SD, and update the section size. The section file offset should
@ -350,6 +389,21 @@ public:
size_t size() const { return Sections.size(); }
/// @}
/// @name Symbol List Access
/// @{
const SymbolDataListType &getSymbolList() const { return Symbols; }
SymbolDataListType &getSymbolList() { return Symbols; }
symbol_iterator symbol_begin() { return Symbols.begin(); }
const_symbol_iterator symbol_begin() const { return Symbols.begin(); }
symbol_iterator symbol_end() { return Symbols.end(); }
const_symbol_iterator symbol_end() const { return Symbols.end(); }
size_t symbol_size() const { return Symbols.size(); }
/// @}
};

239
lib/MC/MCAssembler.cpp
View File

@ -9,6 +9,8 @@
#include "llvm/MC/MCAssembler.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/Support/DataTypes.h"
@ -18,7 +20,10 @@
using namespace llvm;
namespace {
class MachObjectWriter;
static void WriteFileData(raw_ostream &OS, const MCSectionData &SD,
MachObjectWriter &MOW);
class MachObjectWriter {
// See <mach-o/loader.h>.
@ -31,13 +36,18 @@ class MachObjectWriter {
static const unsigned Header64Size = 32;
static const unsigned SegmentLoadCommand32Size = 56;
static const unsigned Section32Size = 68;
static const unsigned SymtabLoadCommandSize = 24;
static const unsigned DysymtabLoadCommandSize = 80;
static const unsigned Nlist32Size = 12;
enum HeaderFileType {
HFT_Object = 0x1
};
enum LoadCommandType {
LCT_Segment = 0x1
LCT_Segment = 0x1,
LCT_Symtab = 0x2,
LCT_Dysymtab = 0xb
};
raw_ostream &OS;
@ -102,7 +112,7 @@ public:
/// @}
void WriteHeader32(unsigned NumSections) {
void WriteHeader32(unsigned NumLoadCommands, unsigned LoadCommandsSize) {
// struct mach_header (28 bytes)
uint64_t Start = OS.tell();
@ -119,25 +129,19 @@ public:
Write32(HFT_Object);
// Object files have a single load command, the segment.
Write32(1);
Write32(SegmentLoadCommand32Size + NumSections * Section32Size);
Write32(NumLoadCommands);
Write32(LoadCommandsSize);
Write32(0); // Flags
assert(OS.tell() - Start == Header32Size);
}
void WriteLoadCommandHeader(uint32_t Cmd, uint32_t CmdSize) {
assert((CmdSize & 0x3) == 0 && "Invalid size!");
Write32(Cmd);
Write32(CmdSize);
}
/// WriteSegmentLoadCommand32 - Write a 32-bit segment load command.
///
/// \arg NumSections - The number of sections in this segment.
/// \arg SectionDataSize - The total size of the sections.
void WriteSegmentLoadCommand32(unsigned NumSections,
uint64_t SectionDataStartOffset,
uint64_t SectionDataSize) {
// struct segment_command (56 bytes)
@ -150,8 +154,7 @@ public:
WriteString("", 16);
Write32(0); // vmaddr
Write32(SectionDataSize); // vmsize
Write32(Header32Size + SegmentLoadCommand32Size +
NumSections * Section32Size); // file offset
Write32(SectionDataStartOffset); // file offset
Write32(SectionDataSize); // file size
Write32(0x7); // maxprot
Write32(0x7); // initprot
@ -187,18 +190,137 @@ public:
assert(OS.tell() - Start == Section32Size);
}
void WriteProlog(MCAssembler &Asm) {
void WriteSymtabLoadCommand(uint32_t SymbolOffset, uint32_t NumSymbols,
uint32_t StringTableOffset,
uint32_t StringTableSize) {
// struct symtab_command (24 bytes)
uint64_t Start = OS.tell();
(void) Start;
Write32(LCT_Symtab);
Write32(SymtabLoadCommandSize);
Write32(SymbolOffset);
Write32(NumSymbols);
Write32(StringTableOffset);
Write32(StringTableSize);
assert(OS.tell() - Start == SymtabLoadCommandSize);
}
void WriteDysymtabLoadCommand(uint32_t FirstLocalSymbol,
uint32_t NumLocalSymbols,
uint32_t FirstExternalSymbol,
uint32_t NumExternalSymbols,
uint32_t FirstUndefinedSymbol,
uint32_t NumUndefinedSymbols,
uint32_t IndirectSymbolOffset,
uint32_t NumIndirectSymbols) {
// struct dysymtab_command (80 bytes)
uint64_t Start = OS.tell();
(void) Start;
Write32(LCT_Dysymtab);
Write32(DysymtabLoadCommandSize);
Write32(FirstLocalSymbol);
Write32(NumLocalSymbols);
Write32(FirstExternalSymbol);
Write32(NumExternalSymbols);
Write32(FirstUndefinedSymbol);
Write32(NumUndefinedSymbols);
Write32(0); // tocoff
Write32(0); // ntoc
Write32(0); // modtaboff
Write32(0); // nmodtab
Write32(0); // extrefsymoff
Write32(0); // nextrefsyms
Write32(IndirectSymbolOffset);
Write32(NumIndirectSymbols);
Write32(0); // extreloff
Write32(0); // nextrel
Write32(0); // locreloff
Write32(0); // nlocrel
assert(OS.tell() - Start == DysymtabLoadCommandSize);
}
void WriteNlist32(uint32_t StringIndex, uint8_t Type, uint8_t Sect,
int16_t Desc, uint32_t Value) {
// struct nlist (12 bytes)
Write32(StringIndex);
Write8(Type);
Write8(Sect);
Write16(Desc);
Write32(Value);
}
/// ComputeStringTable - Compute the string table, for use in the symbol
/// table.
///
/// \param StringTable [out] - The string table data.
/// \param StringIndexMap [out] - Map from symbol names to offsets in the
/// string table.
void ComputeStringTable(MCAssembler &Asm, SmallString<256> &StringTable,
StringMap<uint64_t> &StringIndexMap) {
// Build the string table.
//
// FIXME: Does 'as' ever bother to compress this when we have a suffix
// match?
// Index 0 is always the empty string.
StringTable += '\x00';
for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
ie = Asm.symbol_end(); it != ie; ++it) {
StringRef Name = it->getSymbol().getName();
uint64_t &Entry = StringIndexMap[Name];
if (!Entry) {
Entry = StringTable.size();
StringTable += Name;
StringTable += '\x00';
}
}
// The string table is padded to a multiple of 4.
//
// FIXME: Check to see if this varies per arch.
while (StringTable.size() % 4)
StringTable += '\x00';
}
void WriteObject(MCAssembler &Asm) {
unsigned NumSections = Asm.size();
// Compute symbol table information.
SmallString<256> StringTable;
StringMap<uint64_t> StringIndexMap;
unsigned NumSymbols = Asm.symbol_size();
// No symbol table command is written if there are no symbols.
if (NumSymbols)
ComputeStringTable(Asm, StringTable, StringIndexMap);
// 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
// the section headers.
uint64_t FileOffset = Header32Size + SegmentLoadCommand32Size +
NumSections * Section32Size;
// The section data starts after the header, the segment load command (and
// section headers) and the symbol table.
unsigned NumLoadCommands = 1;
uint64_t LoadCommandsSize =
SegmentLoadCommand32Size + NumSections * Section32Size;
// Add the symbol table load command sizes, if used.
if (NumSymbols) {
NumLoadCommands += 2;
LoadCommandsSize += SymtabLoadCommandSize + DysymtabLoadCommandSize;
}
uint64_t FileOffset = Header32Size + LoadCommandsSize;
uint64_t SectionDataStartOffset = FileOffset;
uint64_t SectionDataSize = 0;
unsigned Index = 0;
for (MCAssembler::iterator it = Asm.begin(),
@ -209,20 +331,67 @@ public:
}
// Write the prolog, starting with the header and load command...
WriteHeader32(NumSections);
WriteSegmentLoadCommand32(NumSections, SectionDataSize);
WriteHeader32(NumLoadCommands, LoadCommandsSize);
WriteSegmentLoadCommand32(NumSections, SectionDataStartOffset,
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]);
// Write the symbol table load command, if used.
if (NumSymbols) {
// The string table is written after all the section data.
uint64_t SymbolTableOffset = SectionDataStartOffset + SectionDataSize;
uint64_t StringTableOffset =
SymbolTableOffset + NumSymbols * Nlist32Size;
WriteSymtabLoadCommand(SymbolTableOffset, NumSymbols,
StringTableOffset, StringTable.size());
// FIXME: Get correct symbol indices and counts.
unsigned FirstLocalSymbol = 0;
unsigned NumLocalSymbols = NumSymbols;
unsigned FirstExternalSymbol = NumLocalSymbols;
unsigned NumExternalSymbols = 0;
unsigned FirstUndefinedSymbol = NumLocalSymbols;
unsigned NumUndefinedSymbols = 0;
unsigned IndirectSymbolOffset = 0;
unsigned NumIndirectSymbols = 0;
WriteDysymtabLoadCommand(FirstLocalSymbol, NumLocalSymbols,
FirstExternalSymbol, NumExternalSymbols,
FirstUndefinedSymbol, NumUndefinedSymbols,
IndirectSymbolOffset, NumIndirectSymbols);
}
// Write the actual section data.
for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
WriteFileData(OS, *it, *this);
// Write the symbol table data, if used.
if (NumSymbols) {
// FIXME: Check that offsets match computed ones.
// FIXME: These need to be reordered, both to segregate into categories
// as well as to order some sublists.
// Write the symbol table entries.
for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
ie = Asm.symbol_end(); it != ie; ++it) {
MCSymbol &Sym = it->getSymbol();
uint64_t Index = StringIndexMap[Sym.getName()];
assert(Index && "Invalid index!");
WriteNlist32(Index, /*FIXME: Type=*/0, /*FIXME: Sect=*/0,
/*FIXME: Desc=*/0, /*FIXME: Value=*/0);
}
// Write the string table.
OS << StringTable.str();
}
}
};
}
/* *** */
MCFragment::MCFragment() : Kind(FragmentType(~0)) {
@ -254,6 +423,18 @@ MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
/* *** */
MCSymbolData::MCSymbolData() : Symbol(*(MCSymbol*)0) {}
MCSymbolData::MCSymbolData(MCSymbol &_Symbol, MCFragment *_Fragment,
uint64_t _Offset, MCAssembler *A)
: Symbol(_Symbol), Fragment(_Fragment), Offset(_Offset)
{
if (A)
A->getSymbolList().push_back(this);
}
/* *** */
MCAssembler::MCAssembler(raw_ostream &_OS) : OS(_OS) {}
MCAssembler::~MCAssembler() {
@ -400,15 +581,9 @@ void MCAssembler::Finish() {
for (iterator it = begin(), ie = end(); it != ie; ++it)
LayoutSection(*it);
// Write the object file.
MachObjectWriter MOW(OS);
// Write the prolog, followed by the data for all the sections & fragments.
MOW.WriteProlog(*this);
// FIXME: This should move into the Mach-O writer, it should have control over
// what goes where.
for (iterator it = begin(), ie = end(); it != ie; ++it)
WriteFileData(OS, *it, MOW);
MOW.WriteObject(*this);
OS.flush();
}

37
lib/MC/MCMachOStreamer.cpp
View File

@ -26,6 +26,27 @@ class MCMachOStreamer : public MCStreamer {
MCSectionData *CurSectionData;
DenseMap<const MCSection*, MCSectionData*> SectionMap;
DenseMap<const MCSymbol*, MCSymbolData*> SymbolMap;
private:
MCFragment *getCurrentFragment() const {
assert(CurSectionData && "No current section!");
if (!CurSectionData->empty())
return &CurSectionData->getFragmentList().back();
return 0;
}
MCSymbolData &getSymbolData(MCSymbol &Symbol) {
MCSymbolData *&Entry = SymbolMap[&Symbol];
if (!Entry)
Entry = new MCSymbolData(Symbol, 0, 0, &Assembler);
return *Entry;
}
public:
MCMachOStreamer(MCContext &Context, raw_ostream &_OS)
@ -92,10 +113,16 @@ void MCMachOStreamer::SwitchSection(const MCSection *Section) {
void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
assert(CurSection && "Cannot emit before setting section!");
llvm_unreachable("FIXME: Not yet implemented!");
MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
if (!F)
F = new MCDataFragment(CurSectionData);
MCSymbolData &SD = getSymbolData(*Symbol);
assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
SD.setFragment(F);
SD.setOffset(F->getContents().size());
Symbol->setSection(*CurSection);
}
@ -138,7 +165,9 @@ void MCMachOStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
}
void MCMachOStreamer::EmitBytes(const StringRef &Data) {
MCDataFragment *DF = new MCDataFragment(CurSectionData);
MCDataFragment *DF = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
if (!DF)
DF = new MCDataFragment(CurSectionData);
DF->getContents().append(Data.begin(), Data.end());
}
@ -154,7 +183,7 @@ void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
CurSectionData);
// Update the maximum alignment on the current section if necessary
// Update the maximum alignment on the current section if necessary.
if (ByteAlignment > CurSectionData->getAlignment())
CurSectionData->setAlignment(ByteAlignment);
}