[yaml2obj]Re-allow dynamic sections to have raw content

Recently, support was added to yaml2obj to allow dynamic sections to
have a list of entries, to make it easier to write tests with dynamic
sections. However, this change also removed the ability to provide
custom contents to the dynamic section, making it hard to test
malformed contents (e.g. because the section is not a valid size to
contain an array of entries). This change reinstates this. An error is
emitted if raw content and dynamic entries are both specified.

Reviewed by: grimar, ruiu

Differential Review: https://reviews.llvm.org/D58543

llvm-svn: 354770

Author: jh7370

llvm/include/llvm/ObjectYAML/ELFYAML.h

@@ -141,6 +141,7 @@ struct Section {
 
 struct DynamicSection : Section {
   std::vector<DynamicEntry> Entries;
+  Optional<yaml::BinaryRef> Content;
 
   DynamicSection() : Section(SectionKind::Dynamic) {}
 

llvm/lib/ObjectYAML/ELFYAML.cpp

@@ -855,6 +855,7 @@ static void commonSectionMapping(IO &IO, ELFYAML::Section &Section) {
 static void sectionMapping(IO &IO, ELFYAML::DynamicSection &Section) {
   commonSectionMapping(IO, Section);
   IO.mapOptional("Entries", Section.Entries);
+  IO.mapOptional("Content", Section.Content);
 }
 
 static void sectionMapping(IO &IO, ELFYAML::RawContentSection &Section) {

llvm/test/tools/yaml2obj/dynamic-section-raw-content.yaml

@@ -0,0 +1,44 @@
+# Show that yaml2obj can handle a dynamic section with raw content instead of
+# entries. Also show that it rejects raw content when entries are also provided.
+
+# RUN: yaml2obj --docnum=1 %s -o %t1
+# RUN: llvm-readobj -x .dynamic --sections %t1 | FileCheck %s --check-prefix=RAW
+
+# RAW:      Name: .dynamic
+# RAW-NEXT: Type: SHT_DYNAMIC
+# RAW-NEXT: Flags [
+# RAW-NEXT: ]
+# RAW-NEXT: Address:
+# RAW-NEXT: Offset:
+# RAW-NEXT: Size: 5
+
+# RAW:      Hex dump of section '.dynamic':
+# RAW-NEXT: 0x00000000 01234567 89 {{.*}}
+
+# RUN: not yaml2obj --docnum=2 %s -o %t2 2>&1 | FileCheck %s --check-prefix=ERR
+# ERR: Cannot specify both raw content and explicit entries for dynamic section '.dynamic'.
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_EXEC
+  Machine: EM_X86_64
+Sections:
+  - Name: .dynamic
+    Type: SHT_DYNAMIC
+    Content: "0123456789"
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_EXEC
+  Machine: EM_X86_64
+Sections:
+  - Name:    .dynamic
+    Type:    SHT_DYNAMIC
+    Content: "0123456789"
+    Entries:
+      - Tag:   DT_STRSZ
+        Value: 0

llvm/tools/yaml2obj/yaml2elf.cpp

@@ -169,7 +169,7 @@ class ELFState {
   bool writeSectionContent(Elf_Shdr &SHeader,
                            const ELFYAML::MipsABIFlags &Section,
                            ContiguousBlobAccumulator &CBA);
-  void writeSectionContent(Elf_Shdr &SHeader,
+  bool writeSectionContent(Elf_Shdr &SHeader,
                            const ELFYAML::DynamicSection &Section,
                            ContiguousBlobAccumulator &CBA);
   bool hasDynamicSymbols() const;
@@ -309,7 +309,8 @@ bool ELFState<ELFT>::initSectionHeaders(std::vector<Elf_Shdr> &SHeaders,
       // so just to setup the section offset.
       CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
     } else if (auto S = dyn_cast<ELFYAML::DynamicSection>(Sec.get())) {
-      writeSectionContent(SHeader, *S, CBA);
+      if (!writeSectionContent(SHeader, *S, CBA))
+        return false;
     } else if (auto S = dyn_cast<ELFYAML::SymverSection>(Sec.get())) {
       writeSectionContent(SHeader, *S, CBA);
     } else if (auto S = dyn_cast<ELFYAML::VerneedSection>(Sec.get())) {
@@ -713,15 +714,26 @@ bool ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
 }
 
 template <class ELFT>
-void ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
+bool ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
                                          const ELFYAML::DynamicSection &Section,
                                          ContiguousBlobAccumulator &CBA) {
   typedef typename ELFT::uint uintX_t;
 
   assert(Section.Type == llvm::ELF::SHT_DYNAMIC &&
          "Section type is not SHT_DYNAMIC");
 
-  SHeader.sh_size = 2 * sizeof(uintX_t) * Section.Entries.size();
+  if (!Section.Entries.empty() && Section.Content) {
+    WithColor::error()
+        << "Cannot specify both raw content and explicit entries "
+           "for dynamic section '"
+        << Section.Name << "'.\n";
+    return false;
+  }
+
+  if (Section.Content)
+    SHeader.sh_size = Section.Content->binary_size();
+  else
+    SHeader.sh_size = 2 * sizeof(uintX_t) * Section.Entries.size();
   if (Section.EntSize)
     SHeader.sh_entsize = *Section.EntSize;
   else
@@ -732,6 +744,10 @@ void ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
     support::endian::write<uintX_t>(OS, DE.Tag, ELFT::TargetEndianness);
     support::endian::write<uintX_t>(OS, DE.Val, ELFT::TargetEndianness);
   }
+  if (Section.Content)
+    Section.Content->writeAsBinary(OS);
+
+  return true;
 }
 
 template <class ELFT> bool ELFState<ELFT>::buildSectionIndex() {