[llvm-readelf/llvm-readobj] - Check version of SHT_GNU_verdef section entries when dumping.

[grimar]

Summary

Elfxx_Verdef contains the following field:

vd_version
Version revision. 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)

Our code should check the struct version for correctness. This patch does that.
(This will help to simplify or eliminate ELFDumper<ELFT>::LoadVersionDefs() which
has it's own logic to parse version definitions for no reason. It checks the struct version currently).

[jhenderson]

LGTM, with one suggestion.

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

238

This can be simplified to "Check how we handle a version definition entry with an unsupported version."

There may be other places where this sort of suggestion applies too. Sorry for not highlighting it before.

[grimar]

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

238

Thanks!

[MaskRay]

LG, though I think whether the != 1 is there does not matter (FTR gold has a version mismatch diagnostic but readelf doesn't).

http://refspecs.linuxbase.org/LSB_1.3.0/gLSB/gLSB/symverdefs.html

Use https://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/symversion.html

[grimar]

In D70810#1763446, @MaskRay wrote:

LG, though I think whether the != 1 is there does not matter (FTR gold has a version mismatch diagnostic but readelf doesn't).

I think it just a bug of readelf. I believe it is unlikely that structure will change in incompatible way, but if it is, readelf will fail.

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

FileHeader:
   Type:    ET_DYN
   Machine: EM_X86_64
 Sections:
   - Name:    .gnu.version_d
     Type:    SHT_GNU_verdef
     Link:    .dynstr
     Info:    0x1
     Entries:
-      - Version:    0
+      - Version:    1
         Flags:      0
         VersionNdx: 0
         Hash:       0
         Names:
           - FOO
     ShSize: 1
 DynamicSymbols:
   - Name: foo
FileHeader:
   Type:    ET_DYN
   Machine: EM_X86_64
 Sections:
   - Name:    .gnu.version_d
     Type:    SHT_GNU_verdef
     Link:    .dynstr
     Info:    0x1
     Entries:
-      - Version:    0
+      - Version:    1
         Flags:      0
         VersionNdx: 0
         Hash:       0
         Names:
           - FOO
     ShSize: 21
 DynamicSymbols:
   - Name: foo
 
 ## Check that we can dump a SHT_GNU_verdef section properly even if it contains version names strings
 ## that overrun the linked string table.
 
 # RUN: yaml2obj %s --docnum=6 -o %t6
 # RUN: llvm-readobj -V %t6 2>&1 | FileCheck %s --check-prefix=PAST-STRTAB-END-LLVM --implicit-check-not="warning:" -DFILE=%t6
 # RUN: llvm-readelf -V %t6 2>&1 | FileCheck %s --check-prefix=PAST-STRTAB-END-GNU --implicit-check-not="warning:" -DFILE=%t6
 
 # PAST-STRTAB-END-LLVM:      VersionDefinitions [
 # PAST-STRTAB-END-LLVM-NEXT:   Definition {
-# PAST-STRTAB-END-LLVM-NEXT:     Version: 0
+# PAST-STRTAB-END-LLVM-NEXT:     Version: 1
 # PAST-STRTAB-END-LLVM-NEXT:     Flags [ (0x0)
 # PAST-STRTAB-END-LLVM-NEXT:     ]
 # PAST-STRTAB-END-LLVM-NEXT:     Index: 0
 # PAST-STRTAB-END-LLVM-NEXT:     Hash: 0
 # PAST-STRTAB-END-LLVM-NEXT:     Name: <invalid vda_name: 5>
 # PAST-STRTAB-END-LLVM-NEXT:     Predecessors: []
 # PAST-STRTAB-END-LLVM-NEXT:   }
 # PAST-STRTAB-END-LLVM-NEXT: ]
 
 # PAST-STRTAB-END-GNU:      Version definition section '.gnu.version_d' contains 1 entries:
 # PAST-STRTAB-END-GNU-NEXT:  Addr: 0000000000000000  Offset: 0x000040  Link: 2 (.strtab)
-# PAST-STRTAB-END-GNU-NEXT:   0x0000: Rev: 0  Flags: none  Index: 0  Cnt: 1  Name: <invalid vda_name: 5>
+# PAST-STRTAB-END-GNU-NEXT:   0x0000: Rev: 1  Flags: none  Index: 0  Cnt: 1  Name: <invalid vda_name: 5>
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_DYN
   Machine: EM_X86_64
 Sections:
   - Name:    .gnu.version_d
     Type:    SHT_GNU_verdef
     Link:    .strtab
     Info:    0x1
     Entries:
-      - Version:    0
+      - Version:    1
         Flags:      0
         VersionNdx: 0
         Hash:       0
         Names:
           - FOO
   - Name: .strtab
     Type: SHT_STRTAB
 DynamicSymbols:

 Sections:
   - Type: Fill
     Size: 0x1
   - Name: .gnu.version_d
     Type: SHT_GNU_verdef
     Link: .dynstr
     Info: 0x1
     Entries:
-      - Version:    0
+      - Version:    1
         Flags:      0
         VersionNdx: 0
         Hash:       0
         Names:
           - FOO
 DynamicSymbols:
   - Name: foo
 
FileHeader:
   Machine: EM_X86_64
 Sections:
   - Name:  .gnu.version_d
     Type:  SHT_GNU_verdef
     Flags: [ SHF_ALLOC ]
     Link:  .dynstr
     Info:  0x1
 ## The byte offset to the auxiliary entry is 0x13, i.e. it is not correctly aligned in memory.
-    Content: "0000000000000100000000001300000000000000"
+    Content: "0100000000000100000000001300000000000000"
 DynamicSymbols:
   - Name:    foo
     Binding: STB_GLOBAL
+
+## Check how we handle the case when a version definition entry has an unsupported version.
+
+# RUN: yaml2obj %s --docnum=9 -o %t9
+# RUN: llvm-readobj -V %t9 2>&1 | FileCheck %s --check-prefix=UNSUPPORTED-VERSION -DFILE=%t9
+# RUN: llvm-readelf -V %t9 2>&1 | FileCheck %s --check-prefix=UNSUPPORTED-VERSION -DFILE=%t9
+
+# UNSUPPORTED-VERSION: warning: '[[FILE]]': unable to dump SHT_GNU_verdef section with index 1: version 65278 is not yet supported
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name: .gnu.version_d
+    Type: SHT_GNU_verdef
+    Link: .dynstr
+    Info: 0x1
+    Entries:
+      - Version:    0xfefe
+        Flags:      0
+        VersionNdx: 0
+        Hash:       0
+        Names: []
+DynamicSymbols:
+  - Name: foo

llvm/tools/llvm-readobj/ELFDumper.cpp

if (VerdefBuf + sizeof(Elf_Verdef) > End)
                          " goes past the end of the section");
 
     if (uintptr_t(VerdefBuf) % sizeof(uint32_t) != 0)
       return createError(
           "invalid SHT_GNU_verdef section with index " + Twine(SecNdx) +
           ": found a misaligned version definition entry at offset 0x" +
           Twine::utohexstr(VerdefBuf - Start));
 
+    unsigned Version = *reinterpret_cast<const Elf_Half *>(VerdefBuf);
+    if (Version != 1)
+      return createError("unable to dump SHT_GNU_verdef section with index " +
+                         Twine(SecNdx) + ": version " + Twine(Version) +
+                         " is not yet supported");
+
     const Elf_Verdef *D = reinterpret_cast<const Elf_Verdef *>(VerdefBuf);
     VerDef &VD = *Ret.emplace(Ret.end());
     VD.Offset = VerdefBuf - Start;
     VD.Version = D->vd_version;
     VD.Flags = D->vd_flags;
     VD.Ndx = D->vd_ndx;
     VD.Cnt = D->vd_cnt;
     VD.Hash = D->vd_hash;