[llvm-objcopy][MachO] Ignore all LC_SUB_* commands.

[drodriguez]

Summary

The LC_SUB_FRAMEWORK, LC_SUB_UMBRELLA, LC_SUB_CLIENT, and LC_SUB_LIBRARY
are used to indicate related libraries, binaries or framework names.
Their only payload is the string with the name of the object. Adding
those commands to the list of ignored/skipped load commands will avoid
an error that stop the process of copying/stripping and will copy their
contents verbatim.

Additionally, in order to have a test for this case, yaml2obj now
allows those four commands to contain a PayloadString.

[smeenai]

LGTM

llvm/test/tools/llvm-objcopy/MachO/sub-load-commands.test

7

Can we also cmp the before and after binaries? They should be identical, right?

[MaskRay]

I'll rename PayloadString to Content in D106759

[drodriguez]

In D106412#2903649, @MaskRay wrote:

I'll rename PayloadString to Content in D106759

Thanks. I will rename here, test again, and send and update.

llvm/test/tools/llvm-objcopy/MachO/sub-load-commands.test

7

I don't know. Probably. I will check and add the comparison if so.

[drodriguez]

• Rebase
• Use Content instead of PayloadString (adopting D106759)
• Use cmp in the test to check that objcopy does a perfect copy.

llvm/lib/ObjectYAML/MachOEmitter.cpp

 template <>
 size_t writeLoadCommandData<MachO::rpath_command>(MachOYAML::LoadCommand &LC,
                                                   raw_ostream &OS,
                                                   bool IsLittleEndian) {
   return writePayloadString(LC, OS);
 }
 
 template <>
+size_t writeLoadCommandData<MachO::sub_framework_command>(
+    MachOYAML::LoadCommand &LC, raw_ostream &OS, bool IsLittleEndian) {
+  return writePayloadString(LC, OS);
+}
+
+template <>
+size_t writeLoadCommandData<MachO::sub_umbrella_command>(
+    MachOYAML::LoadCommand &LC, raw_ostream &OS, bool IsLittleEndian) {
+  return writePayloadString(LC, OS);
+}
+
+template <>
+size_t writeLoadCommandData<MachO::sub_client_command>(
+    MachOYAML::LoadCommand &LC, raw_ostream &OS, bool IsLittleEndian) {
+  return writePayloadString(LC, OS);
+}
+
+template <>
+size_t writeLoadCommandData<MachO::sub_library_command>(
+    MachOYAML::LoadCommand &LC, raw_ostream &OS, bool IsLittleEndian) {
+  return writePayloadString(LC, OS);
+}
+
+template <>
 size_t writeLoadCommandData<MachO::build_version_command>(
     MachOYAML::LoadCommand &LC, raw_ostream &OS, bool IsLittleEndian) {
   size_t BytesWritten = 0;
   for (const auto &T : LC.Tools) {
     struct MachO::build_tool_version tool = T;
     if (IsLittleEndian != sys::IsLittleEndianHost)
       MachO::swapStruct(tool);
     OS.write(reinterpret_cast<const char *>(&tool),

llvm/lib/ObjectYAML/MachOYAML.cpp

 
 template <>
 void mapLoadCommandData<MachO::dylinker_command>(
     IO &IO, MachOYAML::LoadCommand &LoadCommand) {
   IO.mapOptional("Content", LoadCommand.Content);
 }
 
 template <>
+void mapLoadCommandData<MachO::sub_framework_command>(
+    IO &IO, MachOYAML::LoadCommand &LoadCommand) {
+  IO.mapOptional("Content", LoadCommand.Content);
+}
+
+template <>
+void mapLoadCommandData<MachO::sub_umbrella_command>(
+    IO &IO, MachOYAML::LoadCommand &LoadCommand) {
+  IO.mapOptional("Content", LoadCommand.Content);
+}
+
+template <>
+void mapLoadCommandData<MachO::sub_client_command>(
+    IO &IO, MachOYAML::LoadCommand &LoadCommand) {
+  IO.mapOptional("Content", LoadCommand.Content);
+}
+
+template <>
+void mapLoadCommandData<MachO::sub_library_command>(
+    IO &IO, MachOYAML::LoadCommand &LoadCommand) {
+  IO.mapOptional("Content", LoadCommand.Content);
+}
+
+template <>
 void mapLoadCommandData<MachO::build_version_command>(
     IO &IO, MachOYAML::LoadCommand &LoadCommand) {
   IO.mapOptional("Tools", LoadCommand.Tools);
 }
 
 void MappingTraits<MachOYAML::LoadCommand>::mapping(
     IO &IO, MachOYAML::LoadCommand &LoadCommand) {
   MachO::LoadCommandType TempCmd = static_cast<MachO::LoadCommandType>(

llvm/test/tools/llvm-objcopy/MachO/sub-load-commands.test

+## This test verifies that llvm-objcopy correctly ignores the LC_SUB_* load
+## commands.
+
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-objcopy %t %t2
+# RUN: cmp %t %t2
+# RUN: llvm-objdump --macho --private-headers %t2 | FileCheck %s
+
+--- !mach-o
+FileHeader:
+  magic:      0xFEEDFACF
+  cputype:    0x01000007
+  cpusubtype: 0x80000003
+  filetype:   0x00000002
+  ncmds:      4
+  sizeofcmds: 72
+  flags:      0x00200085
+  reserved:   0x00000000
+LoadCommands:
+  - cmd:          LC_SUB_FRAMEWORK
+    cmdsize:      16
+    umbrella:     12
+    Content:      'Bar'
+    ZeroPadBytes: 1
+  - cmd:          LC_SUB_UMBRELLA
+    cmdsize:      16
+    sub_umbrella: 12
+    Content:      'Foo'
+    ZeroPadBytes: 1
+  - cmd:          LC_SUB_LIBRARY
+    cmdsize:      24
+    sub_library:  12
+    Content:      'libfoo'
+    ZeroPadBytes: 6
+  - cmd:          LC_SUB_CLIENT
+    cmdsize:      16
+    client:       12
+    Content:      'bar'
+    ZeroPadBytes: 1
+
+# CHECK: Load command 0
+# CHECK:           cmd LC_SUB_FRAMEWORK
+# CHECK:       cmdsize 16
+# CHECK:      umbrella Bar (offset 12)
+# CHECK: Load command 1
+# CHECK:           cmd LC_SUB_UMBRELLA
+# CHECK:       cmdsize 16
+# CHECK:  sub_umbrella Foo (offset 12)
+# CHECK: Load command 2
+# CHECK:           cmd LC_SUB_LIBRARY
+# CHECK:       cmdsize 24
+# CHECK:   sub_library libfoo (offset 12)
+# CHECK: Load command 3
+# CHECK:           cmd LC_SUB_CLIENT
+# CHECK:       cmdsize 16
+# CHECK:        client bar (offset 12)

llvm/tools/llvm-objcopy/MachO/MachOLayoutBuilder.cpp

for (LoadCommand &LC : O.LoadCommands) {
     case MachO::LC_BUILD_VERSION:
     case MachO::LC_ID_DYLIB:
     case MachO::LC_LOAD_DYLIB:
     case MachO::LC_LOAD_WEAK_DYLIB:
     case MachO::LC_UUID:
     case MachO::LC_SOURCE_VERSION:
     case MachO::LC_THREAD:
     case MachO::LC_UNIXTHREAD:
+    case MachO::LC_SUB_FRAMEWORK:
+    case MachO::LC_SUB_UMBRELLA:
+    case MachO::LC_SUB_CLIENT:
+    case MachO::LC_SUB_LIBRARY:
       // Nothing to update.
       break;
     default:
       // Abort if it's unsupported in order to prevent corrupting the object.
       return createStringError(llvm::errc::not_supported,
                                "unsupported load command (cmd=0x%x)", cmd);
     }
   }