[llvm-objcopy][MachO] Rebuild the symbol/string table in the writer
Summary: Build the string table using StringTableBuilder, reassign symbol indices, and update symbol indices in relocations to allow adding/modifying/removing symbols from the object.
Reviewers: alexshap, rupprecht, jhenderson
Reviewed By: alexshap
Subscribers: mgorny, jakehehrlich, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D63309
llvm-svn: 364000
diff --git a/llvm/tools/llvm-objcopy/MachO/MachOWriter.cpp b/llvm/tools/llvm-objcopy/MachO/MachOWriter.cpp
index f0c0aee..74200c5 100644
--- a/llvm/tools/llvm-objcopy/MachO/MachOWriter.cpp
+++ b/llvm/tools/llvm-objcopy/MachO/MachOWriter.cpp
@@ -26,18 +26,10 @@
size_t MachOWriter::loadCommandsSize() const { return O.Header.SizeOfCmds; }
size_t MachOWriter::symTableSize() const {
- return O.SymTable.NameList.size() *
+ return O.SymTable.Symbols.size() *
(Is64Bit ? sizeof(MachO::nlist_64) : sizeof(MachO::nlist));
}
-size_t MachOWriter::strTableSize() const {
- size_t S = 0;
- for (const auto &Str : O.StrTable.Strings)
- S += Str.size();
- S += (O.StrTable.Strings.empty() ? 0 : O.StrTable.Strings.size() - 1);
- return S;
-}
-
size_t MachOWriter::totalSize() const {
// Going from tail to head and looking for an appropriate "anchor" to
// calculate the total size assuming that all the offsets are either valid
@@ -49,12 +41,12 @@
O.LoadCommands[*O.SymTabCommandIndex]
.MachOLoadCommand.symtab_command_data;
if (SymTabCommand.symoff) {
- assert((SymTabCommand.nsyms == O.SymTable.NameList.size()) &&
+ assert((SymTabCommand.nsyms == O.SymTable.Symbols.size()) &&
"Incorrect number of symbols");
Ends.push_back(SymTabCommand.symoff + symTableSize());
}
if (SymTabCommand.stroff) {
- assert((SymTabCommand.strsize == strTableSize()) &&
+ assert((SymTabCommand.strsize == StrTableBuilder.getSize()) &&
"Incorrect string table size");
Ends.push_back(SymTabCommand.stroff + SymTabCommand.strsize);
}
@@ -128,6 +120,14 @@
memcpy(B.getBufferStart(), &Header, HeaderSize);
}
+void MachOWriter::updateSymbolIndexes() {
+ uint32_t Index = 0;
+ for (auto &Symbol : O.SymTable.Symbols) {
+ Symbol->Index = Index;
+ Index++;
+ }
+}
+
void MachOWriter::writeLoadCommands() {
uint8_t *Begin = B.getBufferStart() + headerSize();
for (const auto &LC : O.LoadCommands) {
@@ -220,24 +220,32 @@
memcpy(B.getBufferStart() + Sec.Offset, Sec.Content.data(),
Sec.Content.size());
for (size_t Index = 0; Index < Sec.Relocations.size(); ++Index) {
- MachO::any_relocation_info R = Sec.Relocations[Index];
+ auto RelocInfo = Sec.Relocations[Index];
+ if (!RelocInfo.Scattered) {
+ auto *Info =
+ reinterpret_cast<MachO::relocation_info *>(&RelocInfo.Info);
+ Info->r_symbolnum = RelocInfo.Symbol->Index;
+ }
+
if (IsLittleEndian != sys::IsLittleEndianHost)
- MachO::swapStruct(R);
+ MachO::swapStruct(
+ reinterpret_cast<MachO::any_relocation_info &>(RelocInfo.Info));
memcpy(B.getBufferStart() + Sec.RelOff +
Index * sizeof(MachO::any_relocation_info),
- &R, sizeof(R));
+ &RelocInfo.Info, sizeof(RelocInfo.Info));
}
}
}
template <typename NListType>
-void writeNListEntry(const NListEntry &NLE, bool IsLittleEndian, char *&Out) {
+void writeNListEntry(const SymbolEntry &SE, bool IsLittleEndian, char *&Out,
+ uint32_t Nstrx) {
NListType ListEntry;
- ListEntry.n_strx = NLE.n_strx;
- ListEntry.n_type = NLE.n_type;
- ListEntry.n_sect = NLE.n_sect;
- ListEntry.n_desc = NLE.n_desc;
- ListEntry.n_value = NLE.n_value;
+ ListEntry.n_strx = Nstrx;
+ ListEntry.n_type = SE.n_type;
+ ListEntry.n_sect = SE.n_sect;
+ ListEntry.n_desc = SE.n_desc;
+ ListEntry.n_value = SE.n_value;
if (IsLittleEndian != sys::IsLittleEndianHost)
MachO::swapStruct(ListEntry);
@@ -251,15 +259,9 @@
const MachO::symtab_command &SymTabCommand =
O.LoadCommands[*O.SymTabCommandIndex]
.MachOLoadCommand.symtab_command_data;
- assert((SymTabCommand.nsyms == O.SymTable.NameList.size()) &&
- "Incorrect number of symbols");
- char *Out = (char *)B.getBufferStart() + SymTabCommand.symoff;
- for (auto NLE : O.SymTable.NameList) {
- if (Is64Bit)
- writeNListEntry<MachO::nlist_64>(NLE, IsLittleEndian, Out);
- else
- writeNListEntry<MachO::nlist>(NLE, IsLittleEndian, Out);
- }
+
+ uint8_t *StrTable = (uint8_t *)B.getBufferStart() + SymTabCommand.stroff;
+ StrTableBuilder.write(StrTable);
}
void MachOWriter::writeStringTable() {
@@ -268,17 +270,17 @@
const MachO::symtab_command &SymTabCommand =
O.LoadCommands[*O.SymTabCommandIndex]
.MachOLoadCommand.symtab_command_data;
- char *Out = (char *)B.getBufferStart() + SymTabCommand.stroff;
- assert((SymTabCommand.strsize == strTableSize()) &&
- "Incorrect string table size");
- for (size_t Index = 0; Index < O.StrTable.Strings.size(); ++Index) {
- memcpy(Out, O.StrTable.Strings[Index].data(),
- O.StrTable.Strings[Index].size());
- Out += O.StrTable.Strings[Index].size();
- if (Index + 1 != O.StrTable.Strings.size()) {
- memcpy(Out, "\0", 1);
- Out += 1;
- }
+
+ char *SymTable = (char *)B.getBufferStart() + SymTabCommand.symoff;
+ for (auto Iter = O.SymTable.Symbols.begin(), End = O.SymTable.Symbols.end();
+ Iter != End; Iter++) {
+ SymbolEntry *Sym = Iter->get();
+ auto Nstrx = StrTableBuilder.getOffset(Sym->Name);
+
+ if (Is64Bit)
+ writeNListEntry<MachO::nlist_64>(*Sym, IsLittleEndian, SymTable, Nstrx);
+ else
+ writeNListEntry<MachO::nlist>(*Sym, IsLittleEndian, SymTable, Nstrx);
}
}
@@ -420,10 +422,10 @@
// are already sorted by the those types.
void MachOWriter::updateDySymTab(MachO::macho_load_command &MLC) {
uint32_t NumLocalSymbols = 0;
- auto Iter = O.SymTable.NameList.begin();
- auto End = O.SymTable.NameList.end();
+ auto Iter = O.SymTable.Symbols.begin();
+ auto End = O.SymTable.Symbols.end();
for (; Iter != End; Iter++) {
- if (Iter->n_type & (MachO::N_EXT | MachO::N_PEXT))
+ if ((*Iter)->n_type & (MachO::N_EXT | MachO::N_PEXT))
break;
NumLocalSymbols++;
@@ -431,7 +433,7 @@
uint32_t NumExtDefSymbols = 0;
for (; Iter != End; Iter++) {
- if ((Iter->n_type & MachO::N_TYPE) == MachO::N_UNDF)
+ if (((*Iter)->n_type & MachO::N_TYPE) == MachO::N_UNDF)
break;
NumExtDefSymbols++;
@@ -443,7 +445,7 @@
MLC.dysymtab_command_data.nextdefsym = NumExtDefSymbols;
MLC.dysymtab_command_data.iundefsym = NumLocalSymbols + NumExtDefSymbols;
MLC.dysymtab_command_data.nundefsym =
- O.SymTable.NameList.size() - (NumLocalSymbols + NumExtDefSymbols);
+ O.SymTable.Symbols.size() - (NumLocalSymbols + NumExtDefSymbols);
}
// Recomputes and updates offset and size fields in load commands and sections
@@ -512,8 +514,9 @@
auto cmd = MLC.load_command_data.cmd;
switch (cmd) {
case MachO::LC_SYMTAB:
+ MLC.symtab_command_data.nsyms = O.SymTable.Symbols.size();
+ MLC.symtab_command_data.strsize = StrTableBuilder.getSize();
MLC.symtab_command_data.symoff = Offset;
- MLC.symtab_command_data.nsyms = O.SymTable.NameList.size();
Offset += NListSize * MLC.symtab_command_data.nsyms;
MLC.symtab_command_data.stroff = Offset;
Offset += MLC.symtab_command_data.strsize;
@@ -554,8 +557,15 @@
return Error::success();
}
+void MachOWriter::constructStringTable() {
+ for (std::unique_ptr<SymbolEntry> &Sym : O.SymTable.Symbols)
+ StrTableBuilder.add(Sym->Name);
+ StrTableBuilder.finalize();
+}
+
Error MachOWriter::finalize() {
updateSizeOfCmds();
+ constructStringTable();
if (auto E = layout())
return E;
@@ -568,6 +578,7 @@
return E;
memset(B.getBufferStart(), 0, totalSize());
writeHeader();
+ updateSymbolIndexes();
writeLoadCommands();
writeSections();
writeTail();