Support -headerpad cmdline option

[pete]

Summary

Hi Lang

(Note this depends on http://reviews.llvm.org/D15943).

This extends the header pad generation we have to also support the -headerpad *size* option.

Similarly to ld64, if both -headerpad_max_install_names and -headerpad are passed, then we take the maximum of the two.

Comments welcome.

Thanks,
Pete

[pete]

Updated test case to include tests for -headerpad combined with -headerpad_max_install_names

[pete]

Updated given that D15943 no longer passes a context to writeBinary

include/lld/ReaderWriter/MachOLinkingContext.h

   uint64_t baseAddress() const { return _baseAddress; }
   void setBaseAddress(uint64_t baseAddress) { _baseAddress = baseAddress; }
 
+  uint64_t headerPad() const { return _headerPad; }
+  void setHeaderPad(uint64_t headerPad) { _headerPad = headerPad; }
+
   bool padHeaderPaths() const { return _padHeaderPaths; }
   void setPadHeaderPaths(bool padHeaderPaths) {
     _padHeaderPaths = padHeaderPaths;

   uint64_t _pageSize;
   uint64_t _baseAddress;
   uint64_t _stackSize;
+  // Note, _headerPad is 32 as that leaves enough space for code signing to be
+  // done after linking.
+  uint64_t _headerPad;
   uint32_t _compatibilityVersion;
   uint32_t _currentVersion;
   StringRef _installName;

lib/Driver/DarwinLdDriver.cpp

     ctx.setStackSize(stackSizeVal);
   }
 
+  // Handle headerpad
+  if (llvm::opt::Arg *headerPad = parsedArgs.getLastArg(OPT_headerpad)) {
+    uint64_t headerPadVal;
+    if (parseNumberBase16(headerPad->getValue(), headerPadVal)) {
+      diagnostics << "error: headerpad expects a hex number\n";
+      return false;
+    }
+
+    ctx.setHeaderPad(headerPadVal);
+  }
+
   // Handle -headerpad_max_install_names
   if (parsedArgs.getLastArg(OPT_headerpad_max_install_names))
     ctx.setPadHeaderPaths(true);

lib/Driver/DarwinLdOptions.td

      HelpText<"Add path to the runpath search path list for image being created">;
 def headerpad_max_install_names : Flag<["-"], "headerpad_max_install_names">,
      HelpText<"Pads paths up to MAXPATHLEN for use with install_name_tool">;
+def headerpad : Separate<["-"], "headerpad">,
+     HelpText<"Pads the header by the given (hex) number of bytes (default=32b)">;
 
 def t : Flag<["-"], "t">,
      HelpText<"Print the names of the input files as ld processes them">;

lib/ReaderWriter/MachO/MachOLinkingContext.cpp

     : _outputMachOType(MH_EXECUTE), _outputMachOTypeStatic(false),
       _doNothing(false), _pie(false), _arch(arch_unknown), _os(OS::macOSX),
       _osMinVersion(0), _pageZeroSize(0), _pageSize(4096), _baseAddress(0),
-      _stackSize(0), _compatibilityVersion(0), _currentVersion(0),
-      _flatNamespace(false), _padHeaderPaths(false),
+      _stackSize(0), _headerPad(32), _compatibilityVersion(0),
+      _currentVersion(0), _flatNamespace(false), _padHeaderPaths(false),
       _undefinedMode(UndefinedMode::error),
       _deadStrippableDylib(false), _printAtoms(false), _testingFileUsage(false),
       _keepPrivateExterns(false), _demangle(false), _archHandler(nullptr),

lib/ReaderWriter/MachO/MachONormalizedFile.h

   PackedVersion               currentVersion = 0; // dylibs only
   bool                        hasUUID = false;
   bool                        padHeaderPaths = false;
+  Hex32                       headerPad = 0;
   std::vector<StringRef>      rpaths;
   Hex64                       entryAddress = 0;
   Hex64                       stackSize = 0;

lib/ReaderWriter/MachO/MachONormalizedFileBinaryWriter.cpp

       _swap(!MachOLinkingContext::isHostEndian(file.arch)),
       _bigEndianArch(MachOLinkingContext::isBigEndian(file.arch)),
       _padHeaderPaths(file.padHeaderPaths),
-      _seg1addr(INT64_MAX) {
+      _seg1addr(INT64_MAX),
+      _headerPad(file.headerPad) {
   _startOfLoadCommands = _is64 ? sizeof(mach_header_64) : sizeof(mach_header);
   const size_t segCommandBaseSize =
           (_is64 ? sizeof(segment_command_64) : sizeof(segment_command));

 }
 
 void MachOFileLayout::padHeader() {
-  _headerPad = 0;
   if (!_padHeaderPaths)
     return;
 

   // pad the header with enough space for each path to grow to MAXPATHLEN.
   // FIXME!: We need to get the max path in a reliable way.
   const unsigned maxpathlen = 1024;
-  size_t padding = 0;
+  uint32_t padding = 0;
   for (const DependentDylib &dep : _file.dependentDylibs) {
     size_t size = pointerAlign(dep.path.size()+1);
     if (size < maxpathlen)

       padding += maxpathlen - size;
   }
 
-  _headerPad = padding;
+  _headerPad = std::max(padding, _headerPad);
 }
 
 static bool overlaps(const Segment &s1, const Segment &s2) {

lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp

   normFile.pageSize = context.pageSize();
   normFile.rpaths = context.rpaths();
   normFile.padHeaderPaths = context.padHeaderPaths();
+  normFile.headerPad = context.headerPad();
   util.addDependentDylibs(atomFile, normFile);
   util.copySegmentInfo(normFile);
   util.copySectionInfo(normFile);

test/mach-o/headerpad.yaml

+# RUN: lld -flavor darwin -arch x86_64 -dylib %s \
+# RUN:     -install_name /usr/lib/libfoo.dylib %p/Inputs/libSystem.yaml -o %t1.dylib
+# RUN: lld -flavor darwin -arch x86_64 -dylib %s \
+# RUN:     -install_name /usr/lib/libfoo.dylib %p/Inputs/libSystem.yaml -headerpad 0x1000 -o %t2.dylib
+# RUN: llvm-objdump -headers %t1.dylib | FileCheck %s --check-prefix=UNPADDED
+# RUN: llvm-objdump -headers %t2.dylib | FileCheck %s --check-prefix=PADDED
+# RUN: not lld -flavor darwin -arch x86_64 -headerpad hithere %s >/dev/null 2> %t
+# RUN: FileCheck < %t %s --check-prefix=CHECK-ERROR-NOTHEX
+
+# UNPADDED: Sections:
+# UNPADDED-NEXT: Idx Name          Size      Address          Type
+# UNPADDED-NEXT:   0 __text        000001a0 0000000000000e60 TEXT
+
+# PADDED: Sections:
+# PADDED-NEXT: Idx Name          Size      Address          Type
+# PADDED-NEXT:   0 __text        000001a0 0000000000001e60 TEXT
+
+# CHECK-ERROR-NOTHEX: error: headerpad expects a hex number
+
+--- !mach-o
+arch:            x86_64
+file-type:       MH_OBJECT
+flags:           [ MH_SUBSECTIONS_VIA_SYMBOLS ]
+sections:
+  - segment:         __TEXT
+    section:         __text
+    type:            S_REGULAR
+    attributes:      [ S_ATTR_PURE_INSTRUCTIONS, S_ATTR_SOME_INSTRUCTIONS ]
+    address:         0x0000000000000000
+    content:         [ 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+                       0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55 ]
+global-symbols:
+  - name:            _foo
+    type:            N_SECT
+    scope:           [ N_EXT ]
+    sect:            1
+    value:           0x0000000000000000
+
+...

test/mach-o/headerpad_max_install_names.yaml

 # RUN:     -install_name /usr/lib/libfoo.dylib %p/Inputs/libSystem.yaml -o %t1.dylib
 # RUN: lld -flavor darwin -arch x86_64 -dylib %s \
 # RUN:     -install_name /usr/lib/libfoo.dylib %p/Inputs/libSystem.yaml -headerpad_max_install_names -o %t2.dylib
+# RUN: lld -flavor darwin -arch x86_64 -dylib %s \
+# RUN:     -install_name /usr/lib/libfoo.dylib %p/Inputs/libSystem.yaml -headerpad_max_install_names -headerpad 0x100 -o %t3.dylib
+# RUN: lld -flavor darwin -arch x86_64 -dylib %s \
+# RUN:     -install_name /usr/lib/libfoo.dylib %p/Inputs/libSystem.yaml -headerpad_max_install_names -headerpad 0x2000 -o %t4.dylib
 # RUN: llvm-objdump -headers %t1.dylib | FileCheck %s --check-prefix=UNPADDED
 # RUN: llvm-objdump -headers %t2.dylib | FileCheck %s --check-prefix=PADDED
+# RUN: llvm-objdump -headers %t3.dylib | FileCheck %s --check-prefix=PADDED
+# RUN: llvm-objdump -headers %t4.dylib | FileCheck %s --check-prefix=HEADERPAD
 #
 # Note, this test contains a very large text section.  The load commands and header are typically around 0x200
 # bytes.  This large text section then grows from a page alignment down towards the end of the loads commands.

 # UNPADDED-NEXT: Idx Name          Size      Address          Type
 # UNPADDED-NEXT:   0 __text        00000c28 00000000000003d8 TEXT
 
+# This case is for only passing -headerpad_max_install_names or additionally passing a -headerpad
+# which is small enough that the calculated -headerpad_max_install_names is still used.
 # PADDED: Sections:
 # PADDED-NEXT: Idx Name          Size      Address          Type
 # PADDED-NEXT:   0 __text        00000c28 00000000000013d8 TEXT
 
+# This case is for passing -headerpad_max_install_names, but also a much large -headerpad and so we
+# use the value in -headerpad
+# HEADERPAD: Sections:
+# HEADERPAD-NEXT: Idx Name          Size      Address          Type
+# HEADERPAD-NEXT:   0 __text        00000c28 00000000000023d8 TEXT
+
 --- !mach-o
 arch:            x86_64
 file-type:       MH_OBJECT