[llvm-objcopy] Ignore -B --binary-architecture=

GNU objcopy documents that -B is only useful with architecture-less
input (i.e. "binary" or "ihex"). After D67144, -O defaults to -I, and
-B is essentially a NOP.

* If -O is binary/ihex, GNU objcopy ignores -B.
* If -O is elf*, -B provides the e_machine field in GNU objcopy.

So to convert a blob to an ELF, `-I binary -B i386:x86-64 -O elf64-x86-64` has to be specified.

`-I binary -B i386:x86-64 -O elf64-x86-64` creates an ELF with its
e_machine field set to EM_NONE in GNU objcopy, but a regular x86_64 ELF
in elftoolchain elfcopy. Follow the elftoolchain approach (ignoring -B)
to simplify code. Users that expect their command line portable should
specify -B.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D67215

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@371914 91177308-0d34-0410-b5e6-96231b3b80d8

docs/CommandGuide/llvm-objcopy.rst

@@ -43,6 +43,10 @@ multiple file formats.
  starts with ".note". Otherwise, it will have type `SHT_PROGBITS`. Can be
  specified multiple times to add multiple sections.
 
+.. option:: --binary-architecture <arch>, -B
+
+ Ignored for compatibility.
+
 .. option:: --disable-deterministic-archives, -U
 
  Use real values for UIDs, GIDs and timestamps when updating archive member
@@ -181,23 +185,6 @@ them.
  Allow llvm-objcopy to remove sections even if it would leave invalid section
  references. Any invalid sh_link fields will be set to zero.
 
-.. option:: --binary-architecture <arch>, -B
-
- Specify the architecture to use, when transforming an architecture-less format
- (e.g. binary) to another format. Valid options are:
-
- - `aarch64`
- - `arm`
- - `i386`
- - `i386:x86-64`
- - `mips`
- - `powerpc:common64`
- - `riscv:rv32`
- - `riscv:rv64`
- - `sparc`
- - `sparcel`
- - `x86-64`
-
 .. option:: --build-id-link-dir <dir>
 
  Set the directory used by :option:`--build-id-link-input` and

test/tools/llvm-objcopy/ELF/binary-input-error.test

@@ -1,6 +1,4 @@
 # RUN: echo abcd > %t.txt
 
-# RUN: not llvm-objcopy -I binary -B xyz %t.txt %t.o 2>&1 \
-# RUN:   | FileCheck %s --check-prefix=BAD-BINARY-ARCH
-
-# BAD-BINARY-ARCH: invalid architecture: 'xyz'
+## -B is ignored.
+# RUN: llvm-objcopy -I binary -B xyz %t.txt %t.o

tools/llvm-objcopy/CopyConfig.cpp

@@ -258,29 +258,6 @@ static Expected<NewSymbolInfo> parseNewSymbolInfo(StringRef FlagValue,
   return SI;
 }
 
-static const StringMap<MachineInfo> ArchMap{
-    // Name, {EMachine, 64bit, LittleEndian}
-    {"aarch64", {ELF::EM_AARCH64, true, true}},
-    {"arm", {ELF::EM_ARM, false, true}},
-    {"i386", {ELF::EM_386, false, true}},
-    {"i386:x86-64", {ELF::EM_X86_64, true, true}},
-    {"mips", {ELF::EM_MIPS, false, false}},
-    {"powerpc:common64", {ELF::EM_PPC64, true, true}},
-    {"riscv:rv32", {ELF::EM_RISCV, false, true}},
-    {"riscv:rv64", {ELF::EM_RISCV, true, true}},
-    {"sparc", {ELF::EM_SPARC, false, false}},
-    {"sparcel", {ELF::EM_SPARC, false, true}},
-    {"x86-64", {ELF::EM_X86_64, true, true}},
-};
-
-static Expected<const MachineInfo &> getMachineInfo(StringRef Arch) {
-  auto Iter = ArchMap.find(Arch);
-  if (Iter == std::end(ArchMap))
-    return createStringError(errc::invalid_argument,
-                             "invalid architecture: '%s'", Arch.str().c_str());
-  return Iter->getValue();
-}
-
 struct TargetInfo {
   FileFormat Format;
   MachineInfo Machine;
@@ -489,15 +466,6 @@ Expected<DriverConfig> parseObjcopyOptions(ArrayRef<const char *> ArgsArr) {
                            .Case("binary", FileFormat::Binary)
                            .Case("ihex", FileFormat::IHex)
                            .Default(FileFormat::Unspecified);
-  if (Config.InputFormat == FileFormat::Binary) {
-    auto BinaryArch = InputArgs.getLastArgValue(OBJCOPY_binary_architecture);
-    if (!BinaryArch.empty()) {
-      Expected<const MachineInfo &> MI = getMachineInfo(BinaryArch);
-      if (!MI)
-        return MI.takeError();
-      Config.BinaryArch = *MI;
-    }
-  }
 
   if (opt::Arg *A = InputArgs.getLastArg(OBJCOPY_new_symbol_visibility)) {
     const uint8_t Invalid = 0xff;

tools/llvm-objcopy/CopyConfig.h

@@ -128,8 +128,6 @@ struct CopyConfig {
   StringRef OutputFilename;
   FileFormat OutputFormat;
 
-  // Only applicable for --input-format=binary
-  MachineInfo BinaryArch;
   // Only applicable when --output-format!=binary (e.g. elf64-x86-64).
   Optional<MachineInfo> OutputArch;
 

tools/llvm-objcopy/ELF/ELFObjcopy.cpp

@@ -737,7 +737,7 @@ Error executeObjcopyOnIHex(const CopyConfig &Config, MemoryBuffer &In,
   IHexReader Reader(&In);
   std::unique_ptr<Object> Obj = Reader.create();
   const ElfType OutputElfType =
-      getOutputElfType(Config.OutputArch.getValueOr(Config.BinaryArch));
+    getOutputElfType(Config.OutputArch.getValueOr(MachineInfo()));
   if (Error E = handleArgs(Config, *Obj, Reader, OutputElfType))
     return E;
   return writeOutput(Config, *Obj, Out, OutputElfType);
@@ -747,13 +747,13 @@ Error executeObjcopyOnRawBinary(const CopyConfig &Config, MemoryBuffer &In,
                                 Buffer &Out) {
   uint8_t NewSymbolVisibility =
       Config.NewSymbolVisibility.getValueOr((uint8_t)ELF::STV_DEFAULT);
-  BinaryReader Reader(Config.BinaryArch, &In, NewSymbolVisibility);
+  BinaryReader Reader(&In, NewSymbolVisibility);
   std::unique_ptr<Object> Obj = Reader.create();
 
   // Prefer OutputArch (-O<format>) if set, otherwise fallback to BinaryArch
   // (-B<arch>).
   const ElfType OutputElfType =
-      getOutputElfType(Config.OutputArch.getValueOr(Config.BinaryArch));
+      getOutputElfType(Config.OutputArch.getValueOr(MachineInfo()));
   if (Error E = handleArgs(Config, *Obj, Reader, OutputElfType))
     return E;
   return writeOutput(Config, *Obj, Out, OutputElfType);

tools/llvm-objcopy/ELF/Object.cpp

@@ -1112,7 +1112,7 @@ void BasicELFBuilder::initFileHeader() {
   Obj->OSABI = ELFOSABI_NONE;
   Obj->ABIVersion = 0;
   Obj->Entry = 0x0;
-  Obj->Machine = EMachine;
+  Obj->Machine = EM_NONE;
   Obj->Version = 1;
 }
 
@@ -1606,7 +1606,7 @@ Writer::~Writer() {}
 Reader::~Reader() {}
 
 std::unique_ptr<Object> BinaryReader::create() const {
-  return BinaryELFBuilder(MInfo.EMachine, MemBuf, NewSymbolVisibility).build();
+  return BinaryELFBuilder(MemBuf, NewSymbolVisibility).build();
 }
 
 Expected<std::vector<IHexRecord>> IHexReader::parse() const {

tools/llvm-objcopy/ELF/Object.h

@@ -873,7 +873,6 @@ using object::OwningBinary;
 
 class BasicELFBuilder {
 protected:
-  uint16_t EMachine;
   std::unique_ptr<Object> Obj;
 
   void initFileHeader();
@@ -883,8 +882,7 @@ protected:
   void initSections();
 
 public:
-  BasicELFBuilder(uint16_t EM)
-      : EMachine(EM), Obj(std::make_unique<Object>()) {}
+  BasicELFBuilder() : Obj(std::make_unique<Object>()) {}
 };
 
 class BinaryELFBuilder : public BasicELFBuilder {
@@ -893,8 +891,8 @@ class BinaryELFBuilder : public BasicELFBuilder {
   void addData(SymbolTableSection *SymTab);
 
 public:
-  BinaryELFBuilder(uint16_t EM, MemoryBuffer *MB, uint8_t NewSymbolVisibility)
-      : BasicELFBuilder(EM), MemBuf(MB),
+  BinaryELFBuilder(MemoryBuffer *MB, uint8_t NewSymbolVisibility)
+      : BasicELFBuilder(), MemBuf(MB),
         NewSymbolVisibility(NewSymbolVisibility) {}
 
   std::unique_ptr<Object> build();
@@ -907,7 +905,7 @@ class IHexELFBuilder : public BasicELFBuilder {
 
 public:
   IHexELFBuilder(const std::vector<IHexRecord> &Records)
-      : BasicELFBuilder(ELF::EM_386), Records(Records) {}
+      : BasicELFBuilder(), Records(Records) {}
 
   std::unique_ptr<Object> build();
 };
@@ -942,14 +940,12 @@ public:
 };
 
 class BinaryReader : public Reader {
-  const MachineInfo &MInfo;
   MemoryBuffer *MemBuf;
   uint8_t NewSymbolVisibility;
 
 public:
-  BinaryReader(const MachineInfo &MI, MemoryBuffer *MB,
-               const uint8_t NewSymbolVisibility)
-      : MInfo(MI), MemBuf(MB), NewSymbolVisibility(NewSymbolVisibility) {}
+  BinaryReader(MemoryBuffer *MB, const uint8_t NewSymbolVisibility)
+      : MemBuf(MB), NewSymbolVisibility(NewSymbolVisibility) {}
   std::unique_ptr<Object> create() const override;
 };
 

tools/llvm-objcopy/ObjcopyOpts.td

@@ -1,8 +1,7 @@
 include "CommonOpts.td"
 
 defm binary_architecture
-    : Eq<"binary-architecture", "Used when transforming an architecture-less "
-                                "format (such as binary) to another format">;
+    : Eq<"binary-architecture", "Ignored for compatibility">;
 def B : JoinedOrSeparate<["-"], "B">,
         Alias<binary_architecture>,
         HelpText<"Alias for --binary-architecture">;