[llvm-readobj] Print section type values for unknown sections.

[mattd]

Summary

This patch displays a hexadecimal section value (Elf_Shdr::sh_type) or section-relative offset when printing unknown sections.

Here is a subset of the output (ignoring the fields following "Type" when dumping an ELF's GNU --section-headers table).
Section Headers:

[Nr] Name              Type
[16] android_rel       LOOS+0x1
[17] android_rela      LOOS+0x2
[27] unknown           0x1000: <unknown>
[28] loos              LOOS+0
[30] hios              VERSYM
[31] loproc            LOPROC+0
[33] hiproc            LOPROC+0xFFFFFFF
[34] louser            LOUSER+0
[36] hiuser            LOUSER+0x7FFFFFFF

As a comparison, the previous output looked something like the above, but with a blank "Type" field:

[Nr] Name              Type
[27] unknown
[28] loos
[30] hios              VERSYM
[31] loproc
[33] hiproc
[34] louser
[36] hiuser

This fixes PR40773

[Bigcheese]

lgtm

Should the +0 be +0x0 so that it's always a hex digit? Or is the +0 what the binutils already output?

[mattd]

In D58701#1411546, @Bigcheese wrote:

lgtm

Should the +0 be +0x0 so that it's always a hex digit? Or is the +0 what the binutils already output?

Thanks for the quick review! GNU's readelf output's "+0" in this case, without the "0x" prefix.

[Bigcheese]

Then I'm fine with the patch as is.

[rupprecht]

Thanks!

[MaskRay]

llvm/tools/llvm-readobj/ELFDumper.cpp

2941 ↗

(On Diff #188481)

How about folding SHT_LO{OS,PROC<USER}* cases into getSectionTypeOffsetString?

[jhenderson]

llvm/test/tools/llvm-readobj/elf-section-types.test

103 ↗

(On Diff #188481)

As these are well-known to LLVM values, it might be worth filing a bug and adding a TODO here to make them ANDROID_REL and ANDROID_RELA, similar to the original FIXME comment. Or just fix them in this patch.

115 ↗

(On Diff #188481)

GNU_NEXT -> GNU-NEXT here onwards.

126 ↗

(On Diff #188481)

FWIW, there's an odd mis-match here versus the LLVM testing, which doesn't test .shstrtab. When I wrote this test, I just wanted one of each section type, i.e. I didn't need to test both .strtab and .shstrtab. I don't mind both being there, but then you should also add .shstrtab to LLVM.

llvm/tools/llvm-readobj/ELFDumper.cpp

2941 ↗

(On Diff #188481)

+1 to this, especially for SHT_HI*, since those are no different either way.

I don't think we should handle these types specially in this case, but we can if we are keen for exact GNU output identity. Personally, I'd just favour simpler code and let them print as SHT_LOOS+0x0 etc.

[mattd]

• Fixed the test case (removed underscore typo, and extraneous shstrtab test).
• Emit ANDROID_REL ANDROID_RELA instead of section offsets.
• Modified the range check, allowing us to remove some now redundant code for printing the lower-bound section names.

[jhenderson]

LGTM.

llvm/trunk/test/tools/llvm-readobj/elf-section-types.test

 # LLVM: Name: gnu_verdef
 # LLVM: Type: SHT_GNU_verdef
 # LLVM: Name: gnu_verneed
 # LLVM: Type: SHT_GNU_verneed
 # LLVM: Name: unknown
 # LLVM: Type: Unknown (0x1000)
 # LLVM: Name: loos
 # LLVM: Type: Unknown (0x60000000)
+# LLVM: Name: fooos
+# LLVM: Type: Unknown (0x60000F00)
 # LLVM: Name: hios
 # LLVM: Type: SHT_GNU_versym
 # LLVM: Name: loproc
 # LLVM: Type: Unknown (0x70000000)
+# LLVM: Name: fooproc
+# LLVM: Type: Unknown (0x70000F00)
 # LLVM: Name: hiproc
 # LLVM: Type: Unknown (0x7FFFFFFF)
 # LLVM: Name: louser
 # LLVM: Type: Unknown (0x80000000)
+# LLVM: Name: foouser
+# LLVM: Type: Unknown (0x80000F00)
 # LLVM: Name: hiuser
 # LLVM: Type: Unknown (0xFFFFFFFF)
 # LLVM: Name: .symtab
 # LLVM: Type: SHT_SYMTAB
 # LLVM: Name: .strtab
 # LLVM: Type: SHT_STRTAB
 
 # GNU: [ 0]                         NULL
 # GNU-NEXT: progbits                PROGBITS
 # GNU-NEXT: rela                    RELA
 # GNU-NEXT: hash                    HASH
 # GNU-NEXT: dynamic                 DYNAMIC
 # GNU-NEXT: note                    NOTE
 # GNU-NEXT: nobits                  NOBITS
 # GNU-NEXT: rel                     REL
 # GNU-NEXT: shlib                   SHLIB
 # GNU-NEXT: dynsym                  DYNSYM
 # GNU-NEXT: init_array              INIT_ARRAY
 # GNU-NEXT: fini_array              FINI_ARRAY
 # GNU-NEXT: preinit_array           PREINIT_ARRAY
 # GNU-NEXT: group                   GROUP
 # GNU-NEXT: symtab_shndx            SYMTAB SECTION INDICES
 # GNU-NEXT: relr                    RELR
-## FIXME: These next two lines should print something like ANDROID_REL and ANDROID_RELA.
-## See https://bugs.llvm.org/show_bug.cgi?id=40773.
-# GNU-NEXT: android_rel                      0000000000000000
-# GNU-NEXT: android_rela                     0000000000000000
+# GNU-NEXT: android_rel             ANDROID_REL
+# GNU-NEXT: android_rela            ANDROID_RELA
 # GNU-NEXT: android_relr            RELR
 # GNU-NEXT: llvm_odrtab             LLVM_ODRTAB
 # GNU-NEXT: linker_options          LLVM_LINKER_OPTIONS
 # GNU-NEXT: llvm_call_graph_profile LLVM_CALL_GRAPH_PROFILE
 # GNU-NEXT: llvm_addrsig            LLVM_ADDRSIG
 # GNU-NEXT: gnu_attributes          ATTRIBUTES
 # GNU-NEXT: gnu_hash                GNU_HASH
 # GNU-NEXT: gnu_verdef              VERDEF
 # GNU-NEXT: gnu_verneed             VERNEED
-## TODO: Add testing for unknown section types in GNU output style.
-## See https://bugs.llvm.org/show_bug.cgi?id=40773.
+# GNU-NEXT: unknown                 0x1000: <unknown>
+# GNU-NEXT: loos                    LOOS+0x0
+# GNU-NEXT: fooos                   LOOS+0xF00
+# GNU-NEXT: hios                    VERSYM
+# GNU-NEXT: loproc                  LOPROC+0x0
+# GNU-NEXT: fooproc                 LOPROC+0xF00
+# GNU-NEXT: hiproc                  LOPROC+0xFFFFFFF
+# GNU-NEXT: louser                  LOUSER+0x0
+# GNU-NEXT: foouser                 LOUSER+0xF00
+# GNU-NEXT: hiuser                  LOUSER+0x7FFFFFFF
+# GNU-NEXT: .symtab                 SYMTAB
+# GNU-NEXT: .strtab                 STRTAB
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_REL
   Machine: EM_X86_64
 Sections:
Sections:
   - Name: gnu_verneed
     Type: SHT_GNU_verneed
     Info: 0
     Dependencies:
   - Name: unknown
     Type: 0x1000
   - Name: loos
     Type: 0x60000000
+  - Name: fooos
+    Type: 0x60000F00
   - Name: hios
     Type: 0x6fffffff
     Entries: []
   - Name: loproc
     Type: 0x70000000
+  - Name: fooproc
+    Type: 0x70000F00
   - Name: hiproc
     Type: 0x7fffffff
   - Name: louser
     Type: 0x80000000
+  - Name: foouser
+    Type: 0x80000F00
   - Name: hiuser
     Type: 0xffffffff
 Symbols:
   Global:
     - Name: foo

llvm/trunk/tools/llvm-readobj/ELFDumper.cpp

case ELF::SHT_ANDROID_RELA:
         printRelocation(Obj, SymTab, R, Sec.sh_type == ELF::SHT_ANDROID_RELA);
       break;
     }
   }
   if (!HasRelocSections)
     OS << "\nThere are no relocations in this file.\n";
 }
 
-std::string getSectionTypeString(unsigned Arch, unsigned Type) {
+// Print the offset of a particular section from anyone of the ranges:
+// [SHT_LOOS, SHT_HIOS], [SHT_LOPROC, SHT_HIPROC], [SHT_LOUSER, SHT_HIUSER].
+// If 'Type' does not fall within any of those ranges, then a string is
+// returned as '<unknown>' followed by the type value.
+static std::string getSectionTypeOffsetString(unsigned Type) {
+  if (Type >= SHT_LOOS && Type <= SHT_HIOS)
+    return "LOOS+0x" + to_hexString(Type - SHT_LOOS);
+  else if (Type >= SHT_LOPROC && Type <= SHT_HIPROC)
+    return "LOPROC+0x" + to_hexString(Type - SHT_LOPROC);
+  else if (Type >= SHT_LOUSER && Type <= SHT_HIUSER)
+    return "LOUSER+0x" + to_hexString(Type - SHT_LOUSER);
+  return "0x" + to_hexString(Type) + ": <unknown>";
+}
+
+static std::string getSectionTypeString(unsigned Arch, unsigned Type) {
   using namespace ELF;
 
   switch (Arch) {
   case EM_ARM:
     switch (Type) {
     case SHT_ARM_EXIDX:
       return "ARM_EXIDX";
     case SHT_ARM_PREEMPTMAP:
static std::string getSectionTypeString(unsigned Arch, unsigned Type) {
   case SHT_FINI_ARRAY:
     return "FINI_ARRAY";
   case SHT_PREINIT_ARRAY:
     return "PREINIT_ARRAY";
   case SHT_GROUP:
     return "GROUP";
   case SHT_SYMTAB_SHNDX:
     return "SYMTAB SECTION INDICES";
+  case SHT_ANDROID_REL:
+    return "ANDROID_REL";
+  case SHT_ANDROID_RELA:
+    return "ANDROID_RELA";
   case SHT_RELR:
   case SHT_ANDROID_RELR:
     return "RELR";
   case SHT_LLVM_ODRTAB:
     return "LLVM_ODRTAB";
   case SHT_LLVM_LINKER_OPTIONS:
     return "LLVM_LINKER_OPTIONS";
   case SHT_LLVM_CALL_GRAPH_PROFILE:
     return "LLVM_CALL_GRAPH_PROFILE";
   case SHT_LLVM_ADDRSIG:
     return "LLVM_ADDRSIG";
   // FIXME: Parse processor specific GNU attributes
   case SHT_GNU_ATTRIBUTES:
     return "ATTRIBUTES";
   case SHT_GNU_HASH:
     return "GNU_HASH";
   case SHT_GNU_verdef:
     return "VERDEF";
   case SHT_GNU_verneed:
     return "VERNEED";
   case SHT_GNU_versym:
     return "VERSYM";
   default:
-    return "";
+    return getSectionTypeOffsetString(Type);
   }
   return "";
 }
 
 template <class ELFT>
 void GNUStyle<ELFT>::printSectionHeaders(const ELFO *Obj) {
   unsigned Bias = ELFT::Is64Bits ? 0 : 8;
   ArrayRef<Elf_Shdr> Sections = unwrapOrError(Obj->sections());