[llvm-objdump] Start on -chained_fixups for llvm-otool

And --chained-fixups for llvm-objdump.

For now, this only prints the dyld_chained_fixups_header and adds
plumbing for the flag. This will be expanded in future commits.

When Apple's effort to upstream their chained fixups code continues,
we'll replace this code with the then-upstreamed code. But we need
something in the meantime for testing ld64.lld's chained fixups
code.

Update chained-fixups.yaml with a file that actually contains
the chained fixup data (`LinkEditData` doesn't encode it yet,
so use `__LINKEDIT` via `--raw-segment=data`).

Differential Revision: https://reviews.llvm.org/D131890

1 files changed, 49 insertions, 2 deletions

diff --git a/llvm/tools/llvm-objdump/MachODump.cpp b/llvm/tools/llvm-objdump/MachODump.cpp
index cdbecd5..a2593cf 100644
--- a/llvm/tools/llvm-objdump/MachODump.cpp
+++ b/llvm/tools/llvm-objdump/MachODump.cpp
@@ -81,6 +81,7 @@ bool objdump::DataInCode;
 bool objdump::FunctionStarts;
 bool objdump::LinkOptHints;
 bool objdump::InfoPlist;
+bool objdump::ChainedFixups;
 bool objdump::DyldInfo;
 bool objdump::DylibsUsed;
 bool objdump::DylibId;
@@ -112,6 +113,7 @@ void objdump::parseMachOOptions(const llvm::opt::InputArgList &InputArgs) {
   FunctionStarts = InputArgs.hasArg(OBJDUMP_function_starts);
   LinkOptHints = InputArgs.hasArg(OBJDUMP_link_opt_hints);
   InfoPlist = InputArgs.hasArg(OBJDUMP_info_plist);
+  ChainedFixups = InputArgs.hasArg(OBJDUMP_chained_fixups);
   DyldInfo = InputArgs.hasArg(OBJDUMP_dyld_info);
   DylibsUsed = InputArgs.hasArg(OBJDUMP_dylibs_used);
   DylibId = InputArgs.hasArg(OBJDUMP_dylib_id);
@@ -1193,6 +1195,48 @@ static void printMachOChainedFixups(object::MachOObjectFile *Obj) {
     reportError(std::move(Err), Obj->getFileName());
 }
 
+static void
+PrintChainedFixupsHeader(const MachO::dyld_chained_fixups_header &H) {
+  outs() << "chained fixups header (LC_DYLD_CHAINED_FIXUPS)\n";
+  outs() << "  fixups_version = " << H.fixups_version << '\n';
+  outs() << "  starts_offset  = " << H.starts_offset << '\n';
+  outs() << "  imports_offset = " << H.imports_offset << '\n';
+  outs() << "  symbols_offset = " << H.symbols_offset << '\n';
+  outs() << "  imports_count  = " << H.imports_count << '\n';
+
+  outs() << "  imports_format = " << H.imports_format;
+  switch (H.imports_format) {
+  case llvm::MachO::DYLD_CHAINED_IMPORT:
+    outs() << " (DYLD_CHAINED_IMPORT)";
+    break;
+  case llvm::MachO::DYLD_CHAINED_IMPORT_ADDEND:
+    outs() << " (DYLD_CHAINED_IMPORT_ADDEND)";
+    break;
+  case llvm::MachO::DYLD_CHAINED_IMPORT_ADDEND64:
+    outs() << " (DYLD_CHAINED_IMPORT_ADDEND64)";
+    break;
+  }
+  outs() << '\n';
+
+  outs() << "  symbols_format = " << H.symbols_format;
+  if (H.symbols_format == llvm::MachO::DYLD_CHAINED_SYMBOL_ZLIB)
+    outs() << " (zlib compressed)";
+  outs() << '\n';
+}
+
+static void PrintChainedFixups(MachOObjectFile *O) {
+  // MachOObjectFile::getChainedFixupsHeader() reads LC_DYLD_CHAINED_FIXUPS.
+  // FIXME: Support chained fixups in __TEXT,__chain_starts section too.
+  auto ChainedFixupHeader =
+      unwrapOrError(O->getChainedFixupsHeader(), O->getFileName());
+  if (!ChainedFixupHeader)
+    return;
+
+  PrintChainedFixupsHeader(*ChainedFixupHeader);
+
+  // FIXME: Print more things.
+}
+
 static void PrintDyldInfo(MachOObjectFile *O) {
   outs() << "dyld information:" << '\n';
   printMachOChainedFixups(O);
@@ -1916,8 +1960,9 @@ static void ProcessMachO(StringRef Name, MachOObjectFile *MachOOF,
   // UniversalHeaders or ArchiveHeaders.
   if (Disassemble || Relocations || PrivateHeaders || ExportsTrie || Rebase ||
       Bind || SymbolTable || LazyBind || WeakBind || IndirectSymbols ||
-      DataInCode || FunctionStarts || LinkOptHints || DyldInfo || DylibsUsed ||
-      DylibId || Rpaths || ObjcMetaData || (!FilterSections.empty())) {
+      DataInCode || FunctionStarts || LinkOptHints || ChainedFixups ||
+      DyldInfo || DylibsUsed || DylibId || Rpaths || ObjcMetaData ||
+      (!FilterSections.empty())) {
     if (LeadingHeaders) {
       outs() << Name;
       if (!ArchiveMemberName.empty())
@@ -1986,6 +2031,8 @@ static void ProcessMachO(StringRef Name, MachOObjectFile *MachOOF,
     DumpSectionContents(FileName, MachOOF, Verbose);
   if (InfoPlist)
     DumpInfoPlistSectionContents(FileName, MachOOF);
+  if (ChainedFixups)
+    PrintChainedFixups(MachOOF);
   if (DyldInfo)
     PrintDyldInfo(MachOOF);
   if (DylibsUsed)