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

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

Reviewers: jhenderson, rupprecht, Bigcheese

Reviewed By: jhenderson, rupprecht, Bigcheese

Subscribers: MaskRay, Bigcheese, srhines, jdoerfert, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58701

llvm-svn: 355014

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

@@ -63,14 +63,20 @@
 # 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
@@ -94,10 +100,8 @@
 # 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
@@ -107,8 +111,18 @@
 # 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:
@@ -186,15 +200,21 @@ Sections:
     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:

llvm/tools/llvm-readobj/ELFDumper.cpp

@@ -2830,7 +2830,21 @@ template <class ELFT> void GNUStyle<ELFT>::printRelocations(const ELFO *Obj) {
     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) {
@@ -2903,6 +2917,10 @@ std::string getSectionTypeString(unsigned Arch, unsigned Type) {
     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";
@@ -2926,7 +2944,7 @@ std::string getSectionTypeString(unsigned Arch, unsigned Type) {
   case SHT_GNU_versym:
     return "VERSYM";
   default:
-    return "";
+    return getSectionTypeOffsetString(Type);
   }
   return "";
 }