[llvm-readobj] Fixes malformed json on JSON printed corefiles

This patch fixes an issue where, when printing corefile notes with
llvm-readobj as json, the dumper generated llvm formatted output
which isn't valid json. This alters the dumper to, in the NT_FILE,
note use a JSON particular method and dump properly formatted json
data.
Prior to this patch the JSON output was formatted like:
```

    "Mapping": [
        "Start": 4096,
        "End": 8192,
        "Offset": 12288,
        "Filename": "/path/to/a.out"
    ],
    ...
```
Whereas now it is formatted as:
```

    "Mappings": [
        {
            "Start": 4096,
            "End": 8192,
            "Offset": 12288,
            "Filename": "/path/to/a.out"
        },
        ...
```
Which is valid.

Author: feg208

llvm/docs/ReleaseNotes.rst

@@ -238,6 +238,10 @@ Changes to the LLVM tools
   documented in `--help` output and the command guide. (`#90474
   <https://github.com/llvm/llvm-project/pull/90474>`)
 
+* llvm-readobj's LLVM output has changed format for ELF core files. The
+  NT_FILE note now has a map for the mapped files.
+  (`#92835 <https://github.com/llvm/llvm-project/pull/92835>`).
+
 Changes to LLDB
 ---------------------------------
 

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

@@ -3,6 +3,7 @@
 # RUN: yaml2obj %s -o %t.o
 # RUN: llvm-readelf --notes %t.o | FileCheck %s --check-prefix=GNU
 # RUN: llvm-readobj --notes %t.o | FileCheck %s --check-prefix=LLVM
+# RUN: llvm-readobj --elf-output-style=JSON --pretty-print --notes %t.o | FileCheck %s --check-prefix=JSON
 
 ## llvm-mc doesn't support generating ET_CORE files; the 'Content' field was
 ## generated with the following steps:
@@ -72,24 +73,62 @@ ProgramHeaders:
 # LLVM-NEXT:       Data size: 0x80
 # LLVM-NEXT:       Type: NT_FILE (mapped files)
 # LLVM-NEXT:       Page Size: 4096
-# LLVM-NEXT:       Mapping [
+# LLVM-NEXT:       Mappings [
+# LLVM-NEXT:        {
 # LLVM-NEXT:         Start: 0x1000
 # LLVM-NEXT:         End: 0x2000
 # LLVM-NEXT:         Offset: 0x3000
 # LLVM-NEXT:         Filename: /path/to/a.out
-# LLVM-NEXT:       ]
-# LLVM-NEXT:       Mapping [
+# LLVM-NEXT:        }
+# LLVM-NEXT:        {
 # LLVM-NEXT:         Start: 0x4000
 # LLVM-NEXT:         End: 0x5000
 # LLVM-NEXT:         Offset: 0x6000
 # LLVM-NEXT:         Filename: /path/to/libc.so
-# LLVM-NEXT:       ]
-# LLVM-NEXT:       Mapping [
+# LLVM-NEXT:        }
+# LLVM-NEXT:        {
 # LLVM-NEXT:         Start: 0x7000
 # LLVM-NEXT:         End: 0x8000
 # LLVM-NEXT:         Offset: 0x9000
 # LLVM-NEXT:         Filename: [stack]
-# LLVM-NEXT:       ]
-# LLVM-NEXT:     }
+# LLVM-NEXT:       }
+# LLVM-NEXT:     ]
 # LLVM-NEXT:   }
+# LLVM-NEXT: }
 # LLVM-NEXT: ]
+
+# JSON:      "Notes": [
+# JSON-NEXT:  {
+# JSON-NEXT:      "NoteSection": {
+# JSON-NEXT:          "Name": "<?>",
+# JSON-NEXT:          "Offset": 120,
+# JSON-NEXT:          "Size": 148,
+# JSON-NEXT:          "Note": {
+# JSON-NEXT:              "Owner": "CORE",
+# JSON-NEXT:              "Data size": 128,
+# JSON-NEXT:              "Type": "NT_FILE (mapped files)",
+# JSON-NEXT:              "Page Size": 4096,
+# JSON-NEXT:              "Mappings": [
+# JSON-NEXT:                {
+# JSON-NEXT:                  "Start": 4096,
+# JSON-NEXT:                  "End": 8192,
+# JSON-NEXT:                  "Offset": 12288,
+# JSON-NEXT:                  "Filename": "/path/to/a.out"
+# JSON-NEXT:                },
+# JSON-NEXT:                {
+# JSON-NEXT:                  "Start": 16384,
+# JSON-NEXT:                  "End": 20480,
+# JSON-NEXT:                  "Offset": 24576,
+# JSON-NEXT:                  "Filename": "/path/to/libc.so"
+# JSON-NEXT:                },
+# JSON-NEXT:                {
+# JSON-NEXT:                  "Start": 28672,
+# JSON-NEXT:                  "End": 32768,
+# JSON-NEXT:                  "Offset": 36864,
+# JSON-NEXT:                  "Filename": "[stack]"
+# JSON-NEXT:                }
+# JSON-NEXT:            ]
+# JSON-NEXT:          }
+# JSON-NEXT:      }
+# JSON-NEXT: }
+# JSON-NEXT: ]

llvm/tools/llvm-readobj/ELFDumper.cpp

@@ -7840,8 +7840,9 @@ static bool printLLVMOMPOFFLOADNoteLLVMStyle(uint32_t NoteType,
 
 static void printCoreNoteLLVMStyle(const CoreNote &Note, ScopedPrinter &W) {
   W.printNumber("Page Size", Note.PageSize);
+  ListScope D(W, "Mappings");
   for (const CoreFileMapping &Mapping : Note.Mappings) {
-    ListScope D(W, "Mapping");
+    DictScope D(W);
     W.printHex("Start", Mapping.Start);
     W.printHex("End", Mapping.End);
     W.printHex("Offset", Mapping.Offset);