Index: llvm/include/llvm/BinaryFormat/ELF.h
===================================================================
--- llvm/include/llvm/BinaryFormat/ELF.h
+++ llvm/include/llvm/BinaryFormat/ELF.h
@@ -107,13 +107,17 @@
   unsigned char getDataEncoding() const { return e_ident[EI_DATA]; }
 };
 
-// File types
+// File types.
+// See current registered ELF types at:
+//    http://www.sco.com/developers/gabi/latest/ch4.eheader.html
 enum {
   ET_NONE = 0,        // No file type
   ET_REL = 1,         // Relocatable file
   ET_EXEC = 2,        // Executable file
   ET_DYN = 3,         // Shared object file
   ET_CORE = 4,        // Core file
+  ET_LOOS = 0xfe00,   // Beginning of operating system-specific codes
+  ET_HIOS = 0xfeff,   // Operating system-specific
   ET_LOPROC = 0xff00, // Beginning of processor-specific codes
   ET_HIPROC = 0xffff  // Processor-specific
 };
Index: llvm/test/tools/llvm-readobj/ELF/file-types.test
===================================================================
--- llvm/test/tools/llvm-readobj/ELF/file-types.test
+++ llvm/test/tools/llvm-readobj/ELF/file-types.test
@@ -56,6 +56,17 @@
 # GNU-CORE: ELF Header:
 # GNU-CORE:   Type: CORE (Core file)
 
+## Test what we dump for an arbitrary unknown ELF type.
+# RUN: yaml2obj %s -DTYPE=0xFDFF -o %t.unknown
+# RUN: llvm-readobj -h %t.unknown | FileCheck %s --match-full-lines --check-prefix LLVM-UNNKNOWN
+# RUN: llvm-readelf -h %t.unknown | FileCheck %s --match-full-lines --check-prefix GNU-UNNKNOWN
+
+# LLVM-UNNKNOWN: ElfHeader {
+# LLVM-UNNKNOWN:   Type: 0xFDFF
+
+# GNU-UNNKNOWN: ELF Header:
+# GNU-UNNKNOWN:   Type: <unknown>: fdff
+
 # RUN: yaml2obj %s -DTYPE=0xfe00 -o %t6
 # RUN: llvm-readobj -h %t6 | FileCheck %s --match-full-lines --check-prefix LLVM-LOOS
 # RUN: llvm-readelf -h %t6 | FileCheck %s --match-full-lines --check-prefix GNU-LOOS
@@ -64,7 +75,7 @@
 # LLVM-LOOS:   Type: 0xFE00
 
 # GNU-LOOS: ELF Header:
-# GNU-LOOS:   Type: fe00
+# GNU-LOOS:   Type: OS Specific: (fe00)
 
 # RUN: yaml2obj %s -DTYPE=0xfeff -o %t7
 # RUN: llvm-readobj -h %t7 | FileCheck %s --match-full-lines --check-prefix LLVM-HIOS
@@ -74,7 +85,7 @@
 # LLVM-HIOS:   Type: 0xFEFF
 
 # GNU-HIOS: ELF Header:
-# GNU-HIOS:   Type: feff
+# GNU-HIOS:   Type: OS Specific: (feff)
 
 # RUN: yaml2obj %s -DTYPE=0xff00 -o %t8
 # RUN: llvm-readobj -h %t8 | FileCheck %s --match-full-lines --check-prefix LLVM-LOPROC
@@ -84,7 +95,7 @@
 # LLVM-LOPROC:   Type: 0xFF00
 
 # GNU-LOPROC: ELF Header:
-# GNU-LOPROC:   Type: ff00
+# GNU-LOPROC:   Type: Processor Specific: (ff00)
 
 # RUN: yaml2obj %s -DTYPE=0xffff -o %t9
 # RUN: llvm-readobj -h %t9 | FileCheck %s --match-full-lines --check-prefix LLVM-HIPROC
@@ -94,4 +105,4 @@
 # LLVM-HIPROC:   Type: 0xFFFF
 
 # GNU-HIPROC: ELF Header:
-# GNU-HIPROC:   Type: ffff
+# GNU-HIPROC:   Type: Processor Specific: (ffff)
Index: llvm/test/tools/llvm-readobj/ELF/types.test
===================================================================
--- llvm/test/tools/llvm-readobj/ELF/types.test
+++ /dev/null
@@ -1,65 +0,0 @@
-# Show that llvm-readobj can handle all standard ELF types.
-# RUN: yaml2obj %s -DTYPE=ET_NONE -o %t.none
-# RUN: llvm-readobj --file-headers %t.none | FileCheck %s --check-prefix=LLVM-NONE
-# RUN: llvm-readelf --file-headers %t.none | FileCheck %s --check-prefix=GNU-NONE
-
-# LLVM-NONE: Type: None (0x0)
-# GNU-NONE:  Type: NONE (none)
-
---- !ELF
-FileHeader:
-  Class: ELFCLASS64
-  Data:  ELFDATA2LSB
-  Type:  [[TYPE]]
-
-# RUN: yaml2obj %s -DTYPE=ET_REL -o %t.rel
-# RUN: llvm-readobj --file-headers %t.rel | FileCheck %s --check-prefix=LLVM-REL
-# RUN: llvm-readelf --file-headers %t.rel | FileCheck %s --check-prefix=GNU-REL
-
-# LLVM-REL: Type: Relocatable (0x1)
-# GNU-REL:  Type: REL (Relocatable file)
-
-# RUN: yaml2obj %s -DTYPE=ET_EXEC -o %t.exec
-# RUN: llvm-readobj --file-headers %t.exec | FileCheck %s --check-prefix=LLVM-EXEC
-# RUN: llvm-readelf --file-headers %t.exec | FileCheck %s --check-prefix=GNU-EXEC
-
-# LLVM-EXEC: Type: Executable (0x2)
-# GNU-EXEC:  Type: EXEC (Executable file)
-
-# RUN: yaml2obj %s -DTYPE=ET_DYN -o %t.so
-# RUN: llvm-readobj --file-headers %t.so | FileCheck %s --check-prefix=LLVM-SO
-# RUN: llvm-readelf --file-headers %t.so | FileCheck %s --check-prefix=GNU-SO
-
-# LLVM-SO: Type: SharedObject (0x3)
-# GNU-SO:  Type: DYN (Shared object file)
-
-# RUN: yaml2obj %s -DTYPE=ET_CORE -o %t.core
-# RUN: llvm-readobj --file-headers %t.core | FileCheck %s --check-prefix=LLVM-CORE
-# RUN: llvm-readelf --file-headers %t.core | FileCheck %s --check-prefix=GNU-CORE
-
-# LLVM-CORE: Type: Core (0x4)
-# GNU-CORE:  Type: CORE (Core file)
-
-# Show that llvm-readobj can handle an unknown ELF type.
-# RUN: yaml2obj %s -DTYPE=0x42 -o %t.unknown
-# RUN: llvm-readobj --file-headers %t.unknown | FileCheck %s --check-prefix=LLVM-UNKNOWN
-# RUN: llvm-readelf --file-headers %t.unknown | FileCheck %s --check-prefix=GNU-UNKNOWN
-
-# LLVM-UNKNOWN: Type: 0x42
-# GNU-UNKNOWN:  Type: 42
-
-# Show that llvm-readobj can handle an unknown OS-specific ELF type.
-# RUN: yaml2obj %s -DTYPE=0xfe00 -o %t.os
-# RUN: llvm-readobj --file-headers %t.os | FileCheck %s --check-prefix=LLVM-OS
-# RUN: llvm-readelf --file-headers %t.os | FileCheck %s --check-prefix=GNU-OS
-
-# LLVM-OS: Type: 0xFE00
-# GNU-OS:  Type: fe00
-
-# Show that llvm-readobj can handle an unknown machine-specific ELF type.
-# RUN: yaml2obj %s -DTYPE=0xff00 -o %t.proc
-# RUN: llvm-readobj --file-headers %t.proc | FileCheck %s --check-prefix=LLVM-PROC
-# RUN: llvm-readelf --file-headers %t.proc | FileCheck %s --check-prefix=GNU-PROC
-
-# LLVM-PROC: Type: 0xFF00
-# GNU-PROC:  Type: ff00
Index: llvm/tools/llvm-readobj/ELFDumper.cpp
===================================================================
--- llvm/tools/llvm-readobj/ELFDumper.cpp
+++ llvm/tools/llvm-readobj/ELFDumper.cpp
@@ -3526,8 +3526,20 @@
   printFields(OS, "OS/ABI:", Str);
   printFields(OS,
               "ABI Version:", std::to_string(e.e_ident[ELF::EI_ABIVERSION]));
+
   Str = printEnum(e.e_type, makeArrayRef(ElfObjectFileType));
+  if (e.e_type >= ET_LOPROC) {
+    Str = "Processor Specific: (" + Str + ")";
+  } else if (e.e_type >= ET_LOOS) {
+    Str = "OS Specific: (" + Str + ")";
+  } else if (makeArrayRef(ElfObjectFileType).end() ==
+             llvm::find_if(ElfObjectFileType,
+                           [&](const EnumEntry<unsigned> &E) {
+                             return E.Value == e.e_type;
+                           }))
+    Str = "<unknown>: " + Str;
   printFields(OS, "Type:", Str);
+
   Str = printEnum(e.e_machine, makeArrayRef(ElfMachineType));
   printFields(OS, "Machine:", Str);
   Str = "0x" + to_hexString(e.e_version);