[yaml2obj] - Allow overriding sh_name fields of the sections.

[grimar]

Summary

This is in line with the previous changes which allowed to override the sh_offset/sh_size
and should be useful for writing the test cases.
(I am going to use it for writing a test case for D66976).

[jhenderson]

include/llvm/ObjectYAML/ELFYAML.h

150

what -> which

153

in the sh_name

Perhaps worth mentioning that it does not affect the name stored in the string table.

test/tools/yaml2obj/elf-override-shname.yaml

2

set a custom

[grimar]

• Addressed review comments.

include/llvm/ObjectYAML/ELFYAML.h

153

it does not affect the name stored in the string table

I updated the test case to demonstrate this.

[jhenderson]

LGTM, with nit.

include/llvm/ObjectYAML/ELFYAML.h

154

Nit: missing trailing full stop

[MaskRay]

lib/ObjectYAML/ELFEmitter.cpp

400

// Override the fields if requested.

include/llvm/ObjectYAML/ELFYAML.h

struct Section {
   StringRef Name;
   ELF_SHT Type;
   Optional<ELF_SHF> Flags;
   llvm::yaml::Hex64 Address;
   StringRef Link;
   llvm::yaml::Hex64 AddressAlign;
   Optional<llvm::yaml::Hex64> EntSize;
 
-  // This can be used to override the sh_offset field. It does not place the
-  // section data at the offset specified. Useful for creating invalid objects.
-  Optional<llvm::yaml::Hex64> ShOffset;
-
-  // This can be used to override the sh_size field. It does not affect the
-  // content written.
-  Optional<llvm::yaml::Hex64> ShSize;
-
   // Usually sections are not created implicitly, but loaded from YAML.
   // When they are, this flag is used to signal about that.
   bool IsImplicit;
 
   Section(SectionKind Kind, bool IsImplicit = false)
       : Kind(Kind), IsImplicit(IsImplicit) {}
   virtual ~Section();
+
+  // The following members are used to override section fields which is
+  // useful for creating invalid objects.
+
+  // This can be used to override the offset stored in the sh_name field.
+  // It does not affect the name stored in the string table
+  Optional<llvm::yaml::Hex64> ShName;
+
+  // This can be used to override the sh_offset field. It does not place the
+  // section data at the offset specified.
+  Optional<llvm::yaml::Hex64> ShOffset;
+
+  // This can be used to override the sh_size field. It does not affect the
+  // content written.
+  Optional<llvm::yaml::Hex64> ShSize;
 };
 
 struct DynamicSection : Section {
   std::vector<DynamicEntry> Entries;
   Optional<yaml::BinaryRef> Content;
 
   DynamicSection() : Section(SectionKind::Dynamic) {}
 

lib/ObjectYAML/ELFEmitter.cpp

bool ELFState<ELFT>::initImplicitHeader(ELFState<ELFT> &State,
   else if (SecName == ".dynsym")
     State.initSymtabSectionHeader(Header, SymtabType::Dynamic, CBA, YAMLSec);
   else if (SecName == ".dynstr")
     State.initStrtabSectionHeader(Header, SecName, State.DotDynstr, CBA,
                                   YAMLSec);
   else
     return false;
 
-  // Override the sh_offset/sh_size fields if requested.
+  // Override the fields if requested.
   if (YAMLSec) {
+    if (YAMLSec->ShName)
+      Header.sh_name = *YAMLSec->ShName;
     if (YAMLSec->ShOffset)
       Header.sh_offset = *YAMLSec->ShOffset;
     if (YAMLSec->ShSize)
       Header.sh_size = *YAMLSec->ShSize;
   }
 
   return true;
 }
if (I == 0) {
       if (!writeSectionContent(SHeader, *S, CBA))
         return false;
     } else if (auto S = dyn_cast<ELFYAML::VerdefSection>(Sec)) {
       if (!writeSectionContent(SHeader, *S, CBA))
         return false;
     } else
       llvm_unreachable("Unknown section type");
 
     // Override the sh_offset/sh_size fields if requested.
     if (Sec) {
+      if (Sec->ShName)
+        SHeader.sh_name = *Sec->ShName;
       if (Sec->ShOffset)
         SHeader.sh_offset = *Sec->ShOffset;
       if (Sec->ShSize)
         SHeader.sh_size = *Sec->ShSize;
     }
   }
 
   return true;

lib/ObjectYAML/ELFYAML.cpp

static void commonSectionMapping(IO &IO, ELFYAML::Section &Section) {
   IO.mapRequired("Type", Section.Type);
   IO.mapOptional("Flags", Section.Flags);
   IO.mapOptional("Address", Section.Address, Hex64(0));
   IO.mapOptional("Link", Section.Link, StringRef());
   IO.mapOptional("AddressAlign", Section.AddressAlign, Hex64(0));
   IO.mapOptional("EntSize", Section.EntSize);
 
   // obj2yaml does not dump these fields. They are expected to be empty when we
-  // are producing YAML, because yaml2obj sets appropriate values for sh_offset
-  // and sh_size automatically when they are not explicitly defined.
+  // are producing YAML, because yaml2obj sets appropriate values for them
+  // automatically when they are not explicitly defined.
   assert(!IO.outputting() ||
          (!Section.ShOffset.hasValue() && !Section.ShSize.hasValue()));
+  IO.mapOptional("ShName", Section.ShName);
   IO.mapOptional("ShOffset", Section.ShOffset);
   IO.mapOptional("ShSize", Section.ShSize);
 }
 
 static void sectionMapping(IO &IO, ELFYAML::DynamicSection &Section) {
   commonSectionMapping(IO, Section);
   IO.mapOptional("Entries", Section.Entries);
   IO.mapOptional("Content", Section.Content);

test/tools/yaml2obj/elf-override-shname.yaml

+## Check we are able to set a custom sh_name field for different sections
+## and that doing this does not affect the names stored in the string table.
+
+# RUN: yaml2obj %s -o %t1
+# RUN: llvm-readobj --sections --section-data %t1 | FileCheck %s
+
+# CHECK:      Index: 1
+# CHECK-NEXT: Name:{{.* }}(1)
+# CHECK:      Index: 2
+# CHECK-NEXT: Name:{{.* }}(2)
+# CHECK:      Index: 3
+# CHECK-NEXT: Name:{{.* }}(3)
+# CHECK:      Index: 4
+# CHECK-NEXT: Name:{{.* }}(4)
+# CHECK:      Index: 5
+# CHECK-NEXT: Name:{{.* }}(5)
+# CHECK:      Index: 6
+# CHECK-NEXT: Name:{{.* }}(6)
+# CHECK:      Index: 7
+# CHECK-NEXT: Name:{{.* }}(7)
+# CHECK:      Index: 8
+# CHECK-NEXT: Name:{{.* }}(8)
+# CHECK:      Index: 9
+# CHECK-NEXT: Name:{{.* }}(9)
+# CHECK:      Index: 10
+# CHECK-NEXT: Name:{{.* }}(10)
+# CHECK:      Index: 11
+# CHECK-NEXT: Name:{{.* }}(11)
+
+# CHECK:      Name: .shstrtab
+# CHECK:      SectionData (
+# CHECK-NEXT:  |..nobits..regula|
+# CHECK-NEXT:  |r..gnu.version_r|
+# CHECK-NEXT:  |..group..gnu.ver|
+# CHECK-NEXT:  |sion..dynsym..gn|
+# CHECK-NEXT:  |u.version_d..dyn|
+# CHECK-NEXT:  |amic..shstrtab..|
+# CHECK-NEXT:  |strtab..symtab..|
+# CHECK-NEXT:  |rela.|
+# CHECK-NEXT: )
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_X86_64
+Sections:
+  - Name: .dynsym
+    Type: SHT_DYNSYM
+    ShName: 0x000000001
+  - Name: .symtab
+    Type: SHT_SYMTAB
+    ShName: 0x000000002
+  - Name: .dynamic
+    Type: SHT_DYNAMIC
+    ShName: 0x000000003
+  - Name: .rela
+    Type: SHT_RELA
+    ShName: 0x000000004
+  - Name: .nobits
+    Type: SHT_NOBITS
+    ShName: 0x000000005
+  - Name: .group
+    Type: SHT_GROUP
+    Info: 0
+    ShName: 0x000000006
+    Members:
+  - Name: .gnu.version
+    Type: SHT_GNU_versym
+    Entries: [ ]
+    ShName: 0x000000007
+  - Name: .gnu.version_r
+    Type: SHT_GNU_verneed
+    Info: 0x0000000000000001
+    ShName: 0x000000008
+    Dependencies:
+  - Name: .gnu.version_d
+    Type: SHT_GNU_verdef
+    Info: 0x0000000000000001
+    ShName: 0x000000009
+    Entries:
+  - Name: .regular
+    Type: SHT_PROGBITS
+    ShName: 0x00000000A
+  - Name: .strtab
+    Type: SHT_STRTAB
+    ShName: 0x00000000B