[llvm-readobj] Add GNU style dumper for .gnu.version_d section

[Higuoxing]

Summary

This patch adds GNU style dumper for .gnu.version_d section

[Higuoxing]

llvm/tools/llvm-readobj/ELFDumper.cpp

3453

In GNU readelf, there's no limit on the number of predecessors. For example, if one symbol has more than one parents, GNU readelf will give:

Parent 1: VERSION1
Parent 2: VERSION0
...

Shall we do the same thing in llvm-readelf ?

[jhenderson]

llvm/tools/llvm-readobj/ELFDumper.cpp

3417

Given that much of this code is a copy of the LLVMStyle, that indicates that it should be shared somehow. I don't know if in this file, or in the Object library somewhere makes sense, but I think the only distinction should be how to print the output.

3453

Is there a good reason to limit it? If not, I don't think we should. However, I get the feeling that this is a different patch, since we should do it in LLVM style too, unless there's a good reason not to.

[Higuoxing]

llvm/tools/llvm-readobj/ELFDumper.cpp

3417

Yes, I agree. I would like to improve this in the future.

3453

I had asked @grimar about this in https://reviews.llvm.org/D21552

I think it's good to be robust when dumping some uncommon object files.

[jhenderson]

llvm/tools/llvm-readobj/ELFDumper.cpp

3417

I don't think we should delay it to the future. It should be done either as part of, or more likely prior to this patch.

3453

By robust, I think we should handle all cases we reasonably can. However, as this is already a limitation, I don't think we need to change it in this patch, but it can be in a follow-up.

[Higuoxing]

llvm/tools/llvm-readobj/ELFDumper.cpp

3417

Sure, I will do that first. Thanks.

[Higuoxing]

Abandon Revision. @grimar has implemented it in https://reviews.llvm.org/D62520

llvm/test/tools/llvm-readobj/elf-versioninfo.test

 GNU-VERDEF: 0x000000006ffffffc VERDEF               0x25c
 GNU-VERDEF: 0x000000006ffffffd VERDEFNUM            3
 
 GNU-VERDEF:      Version symbols section '.gnu.version' contains 8 entries:
 GNU-VERDEF-NEXT:  Addr: 000000000000024c  Offset: 0x00024c  Link: 1 (.dynsym)
 GNU-VERDEF-NEXT:   000:   0 (*local*)       1 (*global*)      1 (*global*)      3 (VERSION2)
 GNU-VERDEF-NEXT:   004:   1 (*global*)      2 (VERSION1)      2 (VERSION1)      3 (VERSION2)
 
-GNU-VERDEF: Dumper for .gnu.version_d is not implemented
+GNU-VERDEF:       Version definition section '.gnu.version_d' contains 3 entries:
+GNU-VERDEF-NEXT:   Addr: 0x000000000000025c  Offset: 0x00025c  Link: 2 (.dynstr)
+GNU-VERDEF-NEXT:   000000: Rev: 1  Flags: BASE  Index: 1  Cnt: 1  Name: blah
+GNU-VERDEF-NEXT:   0x001c: Rev: 1  Flags: 0     Index: 2  Cnt: 1  Name: VERSION1
+GNU-VERDEF-NEXT:   0x0038: Rev: 1  Flags: 0     Index: 3  Cnt: 2  Name: VERSION2
+GNU-VERDEF-NEXT:   0x0054: Parent 1: VERSION1
 
 RUN: llvm-readobj -V %p/Inputs/verneed.elf-x86-64 | FileCheck %s --check-prefix=LLVM-VERNEED
 RUN: llvm-readelf -V %p/Inputs/verneed.elf-x86-64 | FileCheck %s --check-prefix=GNU-VERNEED
 
 LLVM-VERNEED:       SHT_GNU_verneed {
 LLVM-VERNEED-NEXT:   Dependency {
 LLVM-VERNEED-NEXT:     Version: 1
 LLVM-VERNEED-NEXT:     Count: 2

llvm/tools/llvm-readobj/ELFDumper.cpp

 }
 
 template <class ELFT>
 void GNUStyle<ELFT>::printVersionDefinitionSection(const ELFFile<ELFT> *Obj,
                                                    const Elf_Shdr *Sec) {
   if (!Sec)
     return;
 
+  const uint8_t *SecStartAddress =
+      reinterpret_cast<const uint8_t *>(Obj->base() + Sec->sh_offset);
+  const uint8_t *SecEndAddress = SecStartAddress + Sec->sh_size;
+  const uint8_t *VerdefBuf = SecStartAddress;
+  const Elf_Shdr *StrTab = unwrapOrError(Obj->getSection(Sec->sh_link));
+
+  StringRef StrTabName = unwrapOrError(Obj->getSectionName(StrTab));
   StringRef SecName = unwrapOrError(Obj->getSectionName(Sec));
-  OS << "Dumper for " << SecName << " is not implemented\n";
+  uint32_t Entries = Sec->sh_info;
+  OS << "Version definition section '" << SecName << "' contains " << Entries
+     << " entries:\n"
+     << "  Addr: " << format_hex(Sec->sh_addr, 18)
+     << "  Offset: " << format_hex(Sec->sh_offset, 8)
+     << "  Link: " << Sec->sh_link << " (" << StrTabName << ")\n";
+
+  for (uint32_t VerdefOffset = 0, VerdefIndex = 0; VerdefIndex < Entries;
+       VerdefIndex++) {
+    if (VerdefBuf + sizeof(Elf_Verdef) > SecEndAddress)
+      // FIXME: report_fatal_error is not a good way to report error. We should
+      // emit a parsing error here and below.
+      report_fatal_error("invalid offset in the section");
+
+    const Elf_Verdef *Verdef = reinterpret_cast<const Elf_Verdef *>(VerdefBuf);
+
+    OS << format("  %#06x:", VerdefOffset) << " Rev: " << Verdef->vd_version
+       << "  Flags: "
+       << printEnum(Verdef->vd_flags, makeArrayRef(SymVersionFlags))
+       << "  Index: " << Verdef->vd_ndx << "  Cnt: " << Verdef->vd_cnt
+       << "  Name: "
+       << StringRef((const char *)Obj->base() + StrTab->sh_offset +
+                    Verdef->getAux()->vda_name)
+       << '\n';
+
+    if (!Verdef->vd_cnt)
+      report_fatal_error("at least one definition string must exist");
+    if (Verdef->vd_cnt > 2)
+      report_fatal_error("more than one predecessor is not expected");
+
+    if (Verdef->vd_cnt == 2) {
+      const uint8_t *VerdauxBuf =
+          VerdefBuf + Verdef->vd_aux + Verdef->getAux()->vda_next;
+      const Elf_Verdaux *Verdaux =
+          reinterpret_cast<const Elf_Verdaux *>(VerdauxBuf);
+
+      OS << format("  %#06x: Parent 1: ",
+                   VerdefOffset + Verdef->vd_aux + Verdef->getAux()->vda_next)
+         << StringRef((const char *)Obj->base() + StrTab->sh_offset +
+                      Verdaux->vda_name)
+         << '\n';
+    }
+    VerdefBuf += Verdef->vd_next;
+    VerdefOffset += Verdef->vd_next;
+  }
+  OS << '\n';
 }
 
 template <class ELFT>
 void GNUStyle<ELFT>::printVersionDependencySection(const ELFFile<ELFT> *Obj,
                                                    const Elf_Shdr *Sec) {
   if (!Sec)
     return;