[llvm-objcopy] Add basic support for --rename-section

[rupprecht]

Summary

Add basic support for --rename-section=old=new to llvm-objcopy.

A full replacement for GNU objcopy requires also modifying flags (i.e. --rename-section=old=new,flag1,flag2); I'd like to keep that in a separate change to keep this simple.

[rupprecht]

Fixing no trailing \n in a test

[alexander-shaposhnikov]

tools/llvm-objcopy/Object.cpp

1087

nit: for iterators i think it's fine to use simply auto

tools/llvm-objcopy/llvm-objcopy.cpp

434

nit: for one-line "if" braces are not necessary, for instance, in https://llvm.org/docs/CodingStandards.html examples they are omitted

596

these error messages need to be tested (lines 597, 600)

[rupprecht]

Addressed all comments

[rupprecht]

tools/llvm-objcopy/llvm-objcopy.cpp

596

600 should already be covered by --check-prefix=MULTIPLE-RENAMES in test/tools/llvm-objcopy/rename-section.test, let me know if you meant something else.
Added a test case for bad format.

[alexander-shaposhnikov]

to me LG, but I'd wait for Jake as well

tools/llvm-objcopy/Object.cpp

1088

nit (braces)

[rupprecht]

Fixed braces

[jakehehrlich]

I want to keep the public interface of Object as small as possible but other than that LGTM

tools/llvm-objcopy/Object.cpp

1085

This should be done where the option is handled, not by adding a method.

tools/llvm-objcopy/Object.h

705

We don't need a rename section function because you can already loop over sections and update them.

[rupprecht]

Revert changes to Object; do the renaming in objcopy directly.

[rupprecht]

Thanks for the suggestion; removing the Object method will probably make the next change (updating flags) simpler.

test/tools/llvm-objcopy/rename-section-multiple.test

+# RUN: yaml2obj %s > %t
+# RUN: llvm-objcopy --rename-section=.test1=.test2 --rename-section=.test3=.test4 --rename-section=.test5=.test6 %t %t2
+# RUN: llvm-readobj -file-headers -sections -section-data %t2 | FileCheck %s
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .test1
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC ]
+    Content:        "c3c3c3c3"
+  - Name:            .test3
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC ]
+    Content:        "abababab"
+  - Name:            .test7
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC ]
+    Content:        "37373737"
+
+# CHECK: SectionHeaderCount: 7
+
+# CHECK: Name: .test2
+# CHECK: SectionData (
+# CHECK-NEXT:   0000: C3C3C3C3
+# CHECK-NEXT: )
+# CHECK: Name: .test4
+# CHECK: SectionData (
+# CHECK-NEXT:   0000: ABABABAB
+# CHECK-NEXT: )
+# CHECK: Name: .test7
+# CHECK: SectionData (
+# CHECK-NEXT:   0000: 37373737
+# CHECK-NEXT: )
+# CHECK: Name: .symtab
+# CHECK: Name: .strtab
+# CHECK: Name: .shstrtab

test/tools/llvm-objcopy/rename-section.test

+# RUN: yaml2obj %s > %t
+# RUN: llvm-objcopy --rename-section=.foo=.bar %t %t2
+# RUN: llvm-readobj -file-headers -sections -section-data %t2 | FileCheck %s
+# RUN: not llvm-objcopy --rename-section=.foo.bar --rename-section=.foo=.other %t %t2 2>&1 | FileCheck %s --check-prefix=BAD-FORMAT
+# RUN: not llvm-objcopy --rename-section=.foo=.bar --rename-section=.foo=.other %t %t2 2>&1 | FileCheck %s --check-prefix=MULTIPLE-RENAMES
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .foo
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC ]
+    Content:        "c3c3c3c3"
+
+# CHECK: SectionHeaderCount: 5
+
+# CHECK: Name: .bar
+# CHECK: SectionData (
+# CHECK-NEXT:   0000: C3C3C3C3
+# CHECK-NEXT: )
+# CHECK: Name: .symtab
+# CHECK: Name: .strtab
+# CHECK: Name: .shstrtab
+
+#BAD-FORMAT: Bad format for --rename-section
+#MULTIPLE-RENAMES: Already have a section rename for .foo

tools/llvm-objcopy/ObjcopyOpts.td

defm split_dwo : Eq<"split-dwo">,
                  MetaVarName<"dwo-file">,
                  HelpText<"Equivalent to extract-dwo on the input file to <dwo-file>, then strip-dwo on the input file">;
 defm add_gnu_debuglink : Eq<"add-gnu-debuglink">,
                          MetaVarName<"debug-file">,
                          HelpText<"Add a .gnu_debuglink for <debug-file>">;
 defm remove_section : Eq<"remove-section">,
                       MetaVarName<"section">,
                       HelpText<"Remove <section>">;
+defm rename_section : Eq<"rename-section">,
+                      MetaVarName<"old=new">,
+                      HelpText<"Renames a section from old to new">;
 defm redefine_symbol : Eq<"redefine-sym">,
                        MetaVarName<"old=new">,
                        HelpText<"Change the name of a symbol old to new">;
 def R : JoinedOrSeparate<["-"], "R">,
         Alias<remove_section>;
 defm keep : Eq<"keep">,
             MetaVarName<"section">,
             HelpText<"Keep <section>">;

tools/llvm-objcopy/Object.h

public:
   void sortSections();
   SectionTableRef sections() { return SectionTableRef(Sections); }
   ConstRange<SectionBase> sections() const {
     return make_pointee_range(Sections);
   }
   Range<Segment> segments() { return make_pointee_range(Segments); }
   ConstRange<Segment> segments() const { return make_pointee_range(Segments); }
 
+  void renameSections(const StringMap<StringRef> &SectionsToRename);
   void removeSections(std::function<bool(const SectionBase &)> ToRemove);
   void removeSymbols(function_ref<bool(const Symbol &)> ToRemove);
   template <class T, class... Ts> T &addSection(Ts &&... Args) {
     auto Sec = llvm::make_unique<T>(std::forward<Ts>(Args)...);
     auto Ptr = Sec.get();
     Sections.emplace_back(std::move(Sec));
     return *Ptr;
   }

tools/llvm-objcopy/Object.cpp

 void Object::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) {
   if (!SymbolTable)
     return;
 
   for (const SecPtr &Sec : Sections)
     Sec->removeSymbols(ToRemove);
 }
 
+void Object::renameSections(const StringMap<StringRef> &SectionsToRename) {
+  for (const SecPtr &Sec : Sections) {
+    const auto Iter = SectionsToRename.find(Sec->Name);
+    if (Iter != SectionsToRename.end()) {
+      Sec->Name = Iter->second;
+    }
+  }
+}
+
 void Object::sortSections() {
   // Put all sections in offset order. Maintain the ordering as closely as
   // possible while meeting that demand however.
   auto CompareSections = [](const SecPtr &A, const SecPtr &B) {
     return A->OriginalOffset < B->OriginalOffset;
   };
   std::stable_sort(std::begin(this->Sections), std::end(this->Sections),
                    CompareSections);

tools/llvm-objcopy/llvm-objcopy.cpp

struct CopyConfig {
   std::vector<StringRef> Keep;
   std::vector<StringRef> OnlyKeep;
   std::vector<StringRef> AddSection;
   std::vector<StringRef> SymbolsToLocalize;
   std::vector<StringRef> SymbolsToGlobalize;
   std::vector<StringRef> SymbolsToWeaken;
   std::vector<StringRef> SymbolsToRemove;
   std::vector<StringRef> SymbolsToKeep;
+  StringMap<StringRef> SectionsToRename;
   StringMap<StringRef> SymbolsToRename;
   bool StripAll = false;
   bool StripAllGNU = false;
   bool StripDebug = false;
   bool StripSections = false;
   bool StripNonAlloc = false;
   bool StripDWO = false;
   bool StripUnneeded = false;
RemovePred = [&Obj, RemovePred](const SectionBase &Sec) {
       if (&Sec == Obj.SymbolTable || &Sec == Obj.SymbolTable->getStrTab())
         return false;
       return RemovePred(Sec);
     };
   }
 
   Obj.removeSections(RemovePred);
 
+  if (!Config.SectionsToRename.empty())
+    Obj.renameSections(Config.SectionsToRename);
+
   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);
       if (!BufOrErr)
         reportError(File, BufOrErr.getError());
static CopyConfig ParseObjcopyOptions(ArrayRef<const char *> ArgsArr) {
   for (auto Arg : InputArgs.filtered(OBJCOPY_redefine_symbol)) {
     if (!StringRef(Arg->getValue()).contains('='))
       error("Bad format for --redefine-sym");
     auto Old2New = StringRef(Arg->getValue()).split('=');
     if (!Config.SymbolsToRename.insert(Old2New).second)
       error("Multiple redefinition of symbol " + Old2New.first);
   }
 
+  for (auto Arg : InputArgs.filtered(OBJCOPY_rename_section)) {
+    if (!StringRef(Arg->getValue()).contains('='))
+      error("Bad format for --rename-section");
+    auto Old2New = StringRef(Arg->getValue()).split('=');
+    if (!Config.SectionsToRename.insert(Old2New).second)
+      error("Already have a section rename for " + Old2New.first);
+  }
+
   for (auto Arg : InputArgs.filtered(OBJCOPY_remove_section))
     Config.ToRemove.push_back(Arg->getValue());
   for (auto Arg : InputArgs.filtered(OBJCOPY_keep))
     Config.Keep.push_back(Arg->getValue());
   for (auto Arg : InputArgs.filtered(OBJCOPY_only_keep))
     Config.OnlyKeep.push_back(Arg->getValue());
   for (auto Arg : InputArgs.filtered(OBJCOPY_add_section))
     Config.AddSection.push_back(Arg->getValue());