[llvm-objcopy] Use SHT_NOTE for added note sections.

Summary:
Fix llvm-objcopy to add .note sections as SHT_NOTEs. GNU objcopy overrides section flags for special sections. For `.note` sections (with the exception of `.note.GNU-stack`), SHT_NOTE is used.

Many other sections are special cased by libbfd, but `.note` is the only special section I can seem to find being used with objcopy --add-section.

See `.note` in context of the full list of special sections here: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob;f=bfd/elf.c;h=eb3e1828e9c651678b95a1dcbc3b124783d1d2be;hb=HEAD#l2675

Reviewers: jhenderson, alexshap, jakehehrlich, espindola

Reviewed By: jhenderson

Subscribers: emaste, arichardson, llvm-commits

Differential Revision: https://reviews.llvm.org/D56570

llvm-svn: 351204

llvm/test/tools/llvm-objcopy/ELF/add-note.test

@@ -0,0 +1,36 @@
+# Verify that --add-section can be used to add a note section which is
+# successfully interpreted by tools that read notes.
+
+# Add [namesz, descsz, type, name, desc] for a build id.
+# RUN: echo -e -n "\x04\x00\x00\x00" >  %t-note.bin
+# RUN: echo -e -n "\x10\x00\x00\x00" >> %t-note.bin
+# RUN: echo -e -n "\x03\x00\x00\x00" >> %t-note.bin
+# RUN: echo -e -n "GNU\x00"          >> %t-note.bin
+# RUN: echo -e -n "\x00\x01\x02\x03" >> %t-note.bin
+# RUN: echo -e -n "\x04\x05\x06\x07" >> %t-note.bin
+# RUN: echo -e -n "\x08\x09\x0a\x0b" >> %t-note.bin
+# RUN: echo -e -n "\x0c\x0d\x0e\x0f" >> %t-note.bin
+
+# RUN: yaml2obj %s > %t.o
+# RUN: llvm-objcopy --add-section=.note.gnu.build-id=%t-note.bin %t.o %t-with-note.o
+# RUN: llvm-readobj --notes %t-with-note.o | FileCheck %s
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+
+# CHECK:      Notes [
+# CHECK-NEXT:   NoteSection {
+# CHECK-NEXT:     Offset:
+# CHECK-NEXT:     Size:
+# CHECK-NEXT:     Note {
+# CHECK-NEXT:       Owner: GNU
+# CHECK-NEXT:       Data size: 0x10
+# CHECK-NEXT:       Type: NT_GNU_BUILD_ID
+# CHECK-NEXT:       Build ID: 000102030405060708090a0b0c0d0e0f
+# CHECK-NEXT:     }
+# CHECK-NEXT:   }
+# CHECK-NEXT: ]

llvm/test/tools/llvm-objcopy/ELF/add-section-special.test

@@ -0,0 +1,22 @@
+# Check the properties of added sections.
+# By default, sections are SHT_PROGBITS, but .note sections (excluding
+# .note.GNU-stack) are SHT_NOTE sections.
+
+# RUN: yaml2obj %s > %t.o
+# RUN: llvm-objcopy --add-section=.foo=/dev/null %t.o %t-foo.o
+# RUN: llvm-objcopy --add-section=.note.foo=/dev/null %t.o %t-regular-note.o
+# RUN: llvm-objcopy --add-section=.note.GNU-stack=/dev/null %t.o %t-gnu-stack.o
+# RUN: llvm-readelf --sections %t-foo.o | FileCheck %s --check-prefix=NORMAL
+# RUN: llvm-readelf --sections %t-regular-note.o | FileCheck %s --check-prefix=NOTE
+# RUN: llvm-readelf --sections %t-gnu-stack.o | FileCheck %s --check-prefix=GNU-STACK
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+
+# NORMAL:    .foo            PROGBITS
+# NOTE:      .note.foo       NOTE
+# GNU-STACK: .note.GNU-stack PROGBITS

llvm/tools/llvm-objcopy/ELF/ELFObjcopy.cpp

@@ -499,17 +499,21 @@ static void handleArgs(const CopyConfig &Config, Object &Obj,
 
   if (!Config.AddSection.empty()) {
     for (const auto &Flag : Config.AddSection) {
-      auto SecPair = Flag.split("=");
-      auto SecName = SecPair.first;
-      auto File = SecPair.second;
-      auto BufOrErr = MemoryBuffer::getFile(File);
+      std::pair<StringRef, StringRef> SecPair = Flag.split("=");
+      StringRef SecName = SecPair.first;
+      StringRef File = SecPair.second;
+      ErrorOr<std::unique_ptr<MemoryBuffer>> BufOrErr =
+          MemoryBuffer::getFile(File);
       if (!BufOrErr)
         reportError(File, BufOrErr.getError());
-      auto Buf = std::move(*BufOrErr);
-      auto BufPtr = reinterpret_cast<const uint8_t *>(Buf->getBufferStart());
-      auto BufSize = Buf->getBufferSize();
-      Obj.addSection<OwnedDataSection>(SecName,
-                                       ArrayRef<uint8_t>(BufPtr, BufSize));
+      std::unique_ptr<MemoryBuffer> Buf = std::move(*BufOrErr);
+      ArrayRef<uint8_t> Data(
+          reinterpret_cast<const uint8_t *>(Buf->getBufferStart()),
+          Buf->getBufferSize());
+      OwnedDataSection &NewSection =
+          Obj.addSection<OwnedDataSection>(SecName, Data);
+      if (SecName.startswith(".note") && SecName != ".note.GNU-stack")
+        NewSection.Type = SHT_NOTE;
     }
   }