[llvm-readelf/llvm-readobj] - Check the version of SHT_GNU_verneed section entries.

[grimar]

Summary

It is a follow-up for D70826 and it is similar to D70810.

SHT_GNU_verneed contains the following fields:
vn_version: Version of structure. This value is currently set to 1, and will be reset
if the versioning implementation is incompatibly altered.
(https://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/symversion.html)

We should check it for correctness.

[jhenderson]

LGTM.

llvm/test/tools/llvm-readobj/elf-verneed-invalid.test

- Name:  .gnu.version_r
     Type:  SHT_GNU_verneed
     Flags: [ SHF_ALLOC ]
     Info:  1
     Link:  .dynstr
 ## The byte offset to the auxiliary entry is 0x11, i.e. it is not correctly aligned in memory.
     Content: "0100010001000000110000000000000000000000"
 DynamicSymbols:
   - Name: foo
+
+## Check how we handle the case when a dependency definition entry has an unsupported version.
+
+# RUN: yaml2obj %s --docnum=12 -o %t12
+# RUN: llvm-readobj -V %t12 2>&1 | FileCheck %s --check-prefix=UNSUPPORTED-VERSION -DFILE=%t12
+# RUN: llvm-readelf -V %t12 2>&1 | FileCheck %s --check-prefix=UNSUPPORTED-VERSION -DFILE=%t12
+
+# UNSUPPORTED-VERSION: warning: '[[FILE]]': unable to dump SHT_GNU_verneed section with index 1: version 65278 is not yet supported
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_EXEC
+  Machine: EM_X86_64
+Sections:
+  - Name:  .gnu.version_r
+    Type:  SHT_GNU_verneed
+    Flags: [ SHF_ALLOC ]
+    Info:  1
+    Link:  .dynstr
+    Dependencies:
+      - Version: 0xfefe
+        File:    foo
+        Entries:
+          - Name:  'foo'
+            Hash:  0
+            Flags: 0
+            Other: 0
+DynamicSymbols:
+  - Name: foo

llvm/tools/llvm-readobj/ELFDumper.cpp

if (VerneedBuf + sizeof(Elf_Verdef) > End)
                          " goes past the end of the section");
 
     if (uintptr_t(VerneedBuf) % sizeof(uint32_t) != 0)
       return createError(
           "invalid SHT_GNU_verneed section with index " + Twine(SecNdx) +
           ": found a misaligned version dependency entry at offset 0x" +
           Twine::utohexstr(VerneedBuf - Start));
 
+    unsigned Version = *reinterpret_cast<const Elf_Half *>(VerneedBuf);
+    if (Version != 1)
+      return createError("unable to dump SHT_GNU_verneed section with index " +
+                         Twine(SecNdx) + ": version " + Twine(Version) +
+                         " is not yet supported");
+
     const Elf_Verneed *Verneed =
         reinterpret_cast<const Elf_Verneed *>(VerneedBuf);
 
     VerNeed &VN = *Ret.emplace(Ret.end());
     VN.Version = Verneed->vn_version;
     VN.Cnt = Verneed->vn_cnt;
     VN.Offset = VerneedBuf - Start;