[llvm-readobj][RISCV] Support dumping PT_RISCV_ATTRIBUTES

This patch drops the prefix `PT_RISCV_` when dumping `PT_RISCV_ATTRIBUTES`.

GNU readelf dumps it as `RISCV_ATTRIBUT`. Because GNU readelf uses
something like `%-14.14s` so only the first 14 bytes are printed.

Differential Revision: https://reviews.llvm.org/D128493

llvm/include/llvm/BinaryFormat/ELF.h

@@ -1371,6 +1371,9 @@ enum {
   PT_MIPS_RTPROC = 0x70000001,   // Runtime procedure table.
   PT_MIPS_OPTIONS = 0x70000002,  // Options segment.
   PT_MIPS_ABIFLAGS = 0x70000003, // Abiflags segment.
+
+  // RISCV program header types.
+  PT_RISCV_ATTRIBUTES = 0x70000003,
 };
 
 // Segment flag bits.

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

@@ -554,8 +554,8 @@ ProgramHeaders:
     VAddr:    0x1000
     FirstSec: .foo.begin
     LastSec:  .foo.end
-## Case 21: the PT_MIPS_ABIFLAGS segment.
-  - Type:     0x70000003 ## PT_MIPS_ABIFLAGS
+## Case 21: the PT_MIPS_ABIFLAGS/PT_RISCV_ATTRIBUTES segment.
+  - Type:     0x70000003 ## PT_MIPS_ABIFLAGS/PT_RISCV_ATTRIBUTES
     VAddr:    0x1000
     FirstSec: .foo.begin
     LastSec:  .foo.end
@@ -600,6 +600,15 @@ ProgramHeaders:
 # MIPS-LLVM:      ProgramHeader {
 # MIPS-LLVM-NEXT:   Type: PT_MIPS_ABIFLAGS (0x70000003)
 
+## CHECK how we dump RISCV specific program headers.
+# RUN: yaml2obj --docnum=1 -DBITS=64 -DMACHINE=EM_RISCV %s -o %triscv.elf
+# RUN: llvm-readelf --program-headers %triscv.elf | FileCheck %s --check-prefix=RISCV-GNU
+# RUN: llvm-readobj --program-headers %triscv.elf | FileCheck %s --check-prefix=RISCV-LLVM
+
+# RISCV-GNU:       ATTRIBUTES  0x000548 0x0000000000001000 0x0000000000001000 0x000003 0x000003 0x1
+# RISCV-LLVM:      ProgramHeader {
+# RISCV-LLVM:        Type: PT_RISCV_ATTRIBUTES (0x70000003)
+
 ## Check that llvm-readelf reports a warning when a program interpreter
 ## name is non-null-terminated or when PT_INTERP has an offset that
 ## goes past the end of the file.

llvm/tools/llvm-readobj/ELFDumper.cpp

@@ -1390,6 +1390,8 @@ static StringRef segmentTypeToString(unsigned Arch, unsigned Type) {
       LLVM_READOBJ_ENUM_CASE(ELF, PT_MIPS_ABIFLAGS);
     }
     break;
+  case ELF::EM_RISCV:
+    switch (Type) { LLVM_READOBJ_ENUM_CASE(ELF, PT_RISCV_ATTRIBUTES); }
   }
 
   switch (Type) {
@@ -1430,6 +1432,10 @@ static std::string getGNUPtType(unsigned Arch, unsigned Type) {
   if (Seg.consume_front("PT_MIPS_"))
     return Seg.str();
 
+  // E.g. "PT_RISCV_ATTRIBUTES"
+  if (Seg.consume_front("PT_RISCV_"))
+    return Seg.str();
+
   // E.g. "PT_LOAD" -> "LOAD".
   assert(Seg.startswith("PT_"));
   return Seg.drop_front(3).str();