[llvm-readelf] - Start recognizing 'PT_OPENBSD_*' segment types.

[grimar]

Summary

Its a follow-up for D85830, it stops ignoring 'PT_OPENBSD_*' segment types.
Now them are recognized properly.

Note: GNU readelf does not recognize them, though perhaps it shouldn't.
Anyways, it was reported to binutils: https://sourceware.org/bugzilla/show_bug.cgi?id=26405#c0

[MaskRay]

GNU readelf does not handle them properly, I've reported a bug to binutils: https://sourceware.org/bugzilla/show_bug.cgi?id=26405#c0

PT_LOOS through PT_HIOS - Values in this inclusive range are reserved for operating system-specific semantics.

I think it is entirely fair for readelf not to decode them. PT_OPENBSD_BOOTDATA may be a legacy thing. PT_OPENBSD_RANDOMIZE and PT_OPENBSD_WXNEEDED have some references. I think we choose to display the strings just because that makes code simpler.

[jhenderson]

On the basis that this makes the code simpler, and there's no strong motivation not to do this, LGTM.

We might want to consider a strategy for better deciding when to interpret these and other OS-specific segment types however, since not all OSes will support them, and in the worst case, there could even be duplicate meanings for a given value. The alternative to supporting them would be to remove them from the program header definition, of course.

[grimar]

In D86208#2229879, @jhenderson wrote:

We might want to consider a strategy for better deciding when to interpret these and other OS-specific segment types however, since not all OSes will support them

We can just check for ELFOSABI_OPENBSD I think.

llvm/test/tools/llvm-readobj/ELF/program-headers.test

 # ELF32-NEXT:  SHLIB          0x000314 0x00001000 0x00001000 0x00001 0x00001     0x1
 # ELF32-NEXT:  TLS            0x000322 0x00004000 0x00004000 0x00001 0x00001     0x1
 # ELF32-NEXT:  <unknown>: 0x60000000 0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
 # ELF32-NEXT:  GNU_EH_FRAME   0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
 # ELF32-NEXT:  SUNW_UNWIND    0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
 # ELF32-NEXT:  GNU_STACK      0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
 # ELF32-NEXT:  GNU_RELRO      0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
 # ELF32-NEXT:  GNU_PROPERTY   0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
-# ELF32-NEXT:  <unknown>: 0x65a3dbe6 0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
-# ELF32-NEXT:  <unknown>: 0x65a3dbe7 0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
-# ELF32-NEXT:  <unknown>: 0x65a41be6 0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
+# ELF32-NEXT:  OPENBSD_RANDOMIZE 0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
+# ELF32-NEXT:  OPENBSD_WXNEEDED 0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
+# ELF32-NEXT:  OPENBSD_BOOTDATA 0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
 # ELF32-NEXT:  <unknown>: 0x6fffffff 0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
 # ELF32-NEXT:  <unknown>: 0x70000000 0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
 # ELF32-NEXT:  <unknown>: 0x70000001 0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
 # ELF32-NEXT:  <unknown>: 0x70000002 0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
 # ELF32-NEXT:  <unknown>: 0x70000003 0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
 # ELF32-NEXT:  <unknown>: 0x7fffffff 0x000314 0x00001000 0x00001000 0x00003 0x00003     0x1
 # ELF32-EMPTY:
 

 # ELF64-NEXT:  SHLIB          0x000548 0x0000000000001000 0x0000000000001000 0x000001 0x000001     0x1
 # ELF64-NEXT:  TLS            0x000556 0x0000000000004000 0x0000000000004000 0x000001 0x000001     0x1
 # ELF64-NEXT:  <unknown>: 0x60000000 0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
 # ELF64-NEXT:  GNU_EH_FRAME   0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
 # ELF64-NEXT:  SUNW_UNWIND    0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
 # ELF64-NEXT:  GNU_STACK      0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
 # ELF64-NEXT:  GNU_RELRO      0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
 # ELF64-NEXT:  GNU_PROPERTY   0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
-# ELF64-NEXT:  <unknown>: 0x65a3dbe6 0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
-# ELF64-NEXT:  <unknown>: 0x65a3dbe7 0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
-# ELF64-NEXT:  <unknown>: 0x65a41be6 0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
+# ELF64-NEXT:  OPENBSD_RANDOMIZE 0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
+# ELF64-NEXT:  OPENBSD_WXNEEDED 0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
+# ELF64-NEXT:  OPENBSD_BOOTDATA 0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
 # ELF64-NEXT:  <unknown>: 0x6fffffff 0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
 # ELF64-NEXT:  <unknown>: 0x70000000 0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
 # ELF64-NEXT:  <unknown>: 0x70000001 0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
 # ELF64-NEXT:  <unknown>: 0x70000002 0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
 # ELF64-NEXT:  <unknown>: 0x70000003 0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
 # ELF64-NEXT:  <unknown>: 0x7fffffff 0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003     0x1
 # ELF64-EMPTY:
 

llvm/tools/llvm-readobj/ELFDumper.cpp

switch (Type) {
     LLVM_READOBJ_ENUM_CASE(ELF, PT_OPENBSD_BOOTDATA);
   default:
     return "";
   }
 }
 
 static std::string getGNUPtType(unsigned Arch, unsigned Type) {
   StringRef Seg = segmentTypeToString(Arch, Type);
-  // GNU doesn't recognize PT_OPENBSD_*.
-  if (Seg.empty() || Seg.startswith("PT_OPENBSD_"))
+  if (Seg.empty())
     return std::string("<unknown>: ") + to_string(format_hex(Type, 1));
 
   // E.g. "PT_ARM_EXIDX" -> "EXIDX".
   if (Seg.startswith("PT_ARM_"))
     return Seg.drop_front(7).str();
 
   // E.g. "PT_MIPS_REGINFO" -> "REGINFO".
   if (Seg.startswith("PT_MIPS_"))