[llvm-readobj] Add support for reading OpenBSD ELF core notes.

Notes generated in OpenBSD core files provide additional information
about the kernel state and CPU registers. These notes are described
in core.5, which can be viewed here: https://man.openbsd.org/core.5

Differential Revision: https://reviews.llvm.org/D111966

Author: fcambus

llvm/include/llvm/BinaryFormat/ELF.h

@@ -1602,6 +1602,16 @@ enum {
   NT_FREEBSD_PROCSTAT_AUXV = 16,
 };
 
+// OpenBSD core note types.
+enum {
+  NT_OPENBSD_PROCINFO = 10,
+  NT_OPENBSD_AUXV = 11,
+  NT_OPENBSD_REGS = 20,
+  NT_OPENBSD_FPREGS = 21,
+  NT_OPENBSD_XFPREGS = 22,
+  NT_OPENBSD_WCOOKIE = 23,
+};
+
 // AMDGPU-specific section indices.
 enum {
   SHN_AMDGPU_LDS = 0xff00, // Variable in LDS; symbol encoded like SHN_COMMON

llvm/lib/ObjectYAML/ELFYAML.cpp

@@ -155,6 +155,13 @@ void ScalarEnumerationTraits<ELFYAML::ELF_NT>::enumeration(
   ECase(NT_FREEBSD_PROCSTAT_OSREL);
   ECase(NT_FREEBSD_PROCSTAT_PSSTRINGS);
   ECase(NT_FREEBSD_PROCSTAT_AUXV);
+  // OpenBSD core note types.
+  ECase(NT_OPENBSD_PROCINFO);
+  ECase(NT_OPENBSD_AUXV);
+  ECase(NT_OPENBSD_REGS);
+  ECase(NT_OPENBSD_FPREGS);
+  ECase(NT_OPENBSD_XFPREGS);
+  ECase(NT_OPENBSD_WCOOKIE);
   // AMD specific notes. (Code Object V2)
   ECase(NT_AMD_HSA_CODE_OBJECT_VERSION);
   ECase(NT_AMD_HSA_HSAIL);

llvm/test/tools/llvm-readobj/ELF/note-openbsd-core.test

@@ -0,0 +1,69 @@
+## Test that note values are interpreted correctly for OpenBSD core files.
+# RUN: yaml2obj %s -o %t.o
+# RUN: llvm-readelf --notes %t.o | FileCheck %s --check-prefix=GNU --strict-whitespace
+# RUN: llvm-readobj --notes %t.o | FileCheck %s --check-prefix=LLVM --strict-whitespace
+
+--- !ELF
+FileHeader:
+  Class: ELFCLASS64
+  Data:  ELFDATA2LSB
+  Type:  ET_CORE
+Sections:
+  - Name: .note.foo
+    Type: SHT_NOTE
+    Notes:
+      - Name: OpenBSD
+        Type: NT_OPENBSD_PROCINFO
+      - Name: OpenBSD
+        Type: NT_OPENBSD_AUXV
+      - Name: OpenBSD
+        Type: NT_OPENBSD_WCOOKIE
+      - Name: OpenBSD@31337
+        Type: NT_OPENBSD_REGS
+      - Name: OpenBSD@31337
+        Type: NT_OPENBSD_FPREGS
+ProgramHeaders:
+  - Type:     PT_NOTE
+    FirstSec: .note.foo
+    LastSec:  .note.foo
+
+# GNU:      Displaying notes found at file offset 0x00000078 with length 0x00000074:
+# GNU-NEXT:   Owner                Data size 	Description
+# GNU-NEXT:   OpenBSD              0x00000000	NT_OPENBSD_PROCINFO (procinfo structure)
+# GNU-NEXT:   OpenBSD              0x00000000	NT_OPENBSD_AUXV (ELF auxiliary vector data)
+# GNU-NEXT:   OpenBSD              0x00000000	NT_OPENBSD_WCOOKIE (window cookie)
+# GNU-NEXT:   OpenBSD@31337        0x00000000	NT_OPENBSD_REGS (regular registers)
+# GNU-NEXT:   OpenBSD@31337        0x00000000	NT_OPENBSD_FPREGS (floating point registers)
+
+# LLVM:      Notes [
+# LLVM-NEXT:   NoteSection {
+# LLVM-NEXT:     Name: <?>
+# LLVM-NEXT:     Offset: 0x78
+# LLVM-NEXT:     Size: 0x74
+# LLVM-NEXT:     Note {
+# LLVM-NEXT:       Owner: OpenBSD
+# LLVM-NEXT:       Data size: 0x0
+# LLVM-NEXT:       Type: NT_OPENBSD_PROCINFO (procinfo structure)
+# LLVM-NEXT:     }
+# LLVM-NEXT:     Note {
+# LLVM-NEXT:       Owner: OpenBSD
+# LLVM-NEXT:       Data size: 0x0
+# LLVM-NEXT:       Type: NT_OPENBSD_AUXV (ELF auxiliary vector data)
+# LLVM-NEXT:     }
+# LLVM-NEXT:     Note {
+# LLVM-NEXT:       Owner: OpenBSD
+# LLVM-NEXT:       Data size: 0x0
+# LLVM-NEXT:       Type: NT_OPENBSD_WCOOKIE (window cookie)
+# LLVM-NEXT:     }
+# LLVM-NEXT:     Note {
+# LLVM-NEXT:       Owner: OpenBSD@31337
+# LLVM-NEXT:       Data size: 0x0
+# LLVM-NEXT:       Type: NT_OPENBSD_REGS (regular registers)
+# LLVM-NEXT:     }
+# LLVM-NEXT:     Note {
+# LLVM-NEXT:       Owner: OpenBSD@31337
+# LLVM-NEXT:       Data size: 0x0
+# LLVM-NEXT:       Type: NT_OPENBSD_FPREGS (floating point registers)
+# LLVM-NEXT:     }
+# LLVM-NEXT:   }
+# LLVM-NEXT: ]

llvm/tools/llvm-readobj/ELFDumper.cpp

@@ -5331,6 +5331,14 @@ const NoteType FreeBSDNoteTypes[] = {
      "NT_FREEBSD_FEATURE_CTL (FreeBSD feature control)"},
 };
 
+const NoteType OpenBSDCoreNoteTypes[] = {
+    {ELF::NT_OPENBSD_PROCINFO, "NT_OPENBSD_PROCINFO (procinfo structure)"},
+    {ELF::NT_OPENBSD_AUXV, "NT_OPENBSD_AUXV (ELF auxiliary vector data)"},
+    {ELF::NT_OPENBSD_REGS, "NT_OPENBSD_REGS (regular registers)"},
+    {ELF::NT_OPENBSD_FPREGS, "NT_OPENBSD_FPREGS (floating point registers)"},
+    {ELF::NT_OPENBSD_WCOOKIE, "NT_OPENBSD_WCOOKIE (window cookie)"},
+};
+
 const NoteType AMDNoteTypes[] = {
     {ELF::NT_AMD_HSA_CODE_OBJECT_VERSION,
      "NT_AMD_HSA_CODE_OBJECT_VERSION (AMD HSA Code Object Version)"},
@@ -5443,6 +5451,13 @@ StringRef getNoteTypeName(const typename ELFT::Note &Note, unsigned ELFType) {
       return FindNote(FreeBSDNoteTypes);
     }
   }
+  if (Name.startswith("OpenBSD") && ELFType == ELF::ET_CORE) {
+    // OpenBSD also places the generic core notes in the OpenBSD namespace.
+    StringRef Result = FindNote(OpenBSDCoreNoteTypes);
+    if (!Result.empty())
+      return Result;
+    return FindNote(CoreNoteTypes);
+  }
   if (Name == "AMD")
     return FindNote(AMDNoteTypes);
   if (Name == "AMDGPU")