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

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 `Content`.

Differential Revision: https://reviews.llvm.org/D106412

llvm/lib/ObjectYAML/MachOEmitter.cpp

@@ -183,6 +183,30 @@ size_t writeLoadCommandData<MachO::rpath_command>(MachOYAML::LoadCommand &LC,
   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) {

llvm/lib/ObjectYAML/MachOYAML.cpp

@@ -233,6 +233,30 @@ void mapLoadCommandData<MachO::dylinker_command>(
   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) {

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

@@ -0,0 +1,56 @@
+## 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

@@ -380,6 +380,10 @@ Error MachOLayoutBuilder::layoutTail(uint64_t Offset) {
     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: