Implement objdump --section-headers for MachO

examples/dune

@@ -1,6 +1,7 @@
 (executables
- (names decodedline_elf decodedline_macho functions read_buildid read_stapsdt_probes)
- (libraries owee unix))
+ (names decodedline_elf decodedline_macho functions read_buildid read_stapsdt_probes
+        objdump)
+ (libraries owee unix cmdliner))
 
 (alias
  (name runtest)

examples/objdump.ml

@@ -0,0 +1,71 @@
+(**
+    OCaml implementation of objdump for MachO binaries.
+    should be equivalent to
+
+    objdump --section-headers <binaries>
+*)
+let cpu_type_to_string = function
+  | `X86 -> "x86_32"
+  | `X86_64 -> "x86_64"
+  | `ARM -> "arm32"
+  | `ARM64 -> "arm64"
+  | `POWERPC -> "ppc32"
+  | `POWERPC64 -> "ppc64"
+  | _unknown -> "unknown"
+
+let on_segment f = function
+  | Owee_macho.LC_SEGMENT_64 segment | Owee_macho.LC_SEGMENT_32 segment ->
+    let lazy segment = segment in
+    f segment
+  | _ -> ()
+
+let iter_sections f segment =
+  Array.iter (f segment) segment.Owee_macho.seg_sections
+
+let debug_section index (_segment : Owee_macho.segment) (section : Owee_macho.section) =
+  Printf.printf "%3i %-16s %08Lx %016Lx %-10s\n" index
+    section.sec_sectname
+    section.sec_size
+    section.sec_addr
+    section.sec_segname
+
+let print_summary file (header : Owee_macho.header) =
+  Printf.printf "\n%s:\tfile format mach-o %s\n\n" file (cpu_type_to_string header.cpu_type)
+
+let print_section_headers file =
+  let open Printf in
+  let buffer = Owee_buf.map_binary file in
+  let header, commands = Owee_macho.read buffer in
+
+  print_summary file header;
+  printf "Sections: \n";
+  printf "%3s %-16s %-8s %-16s %-10s\n" "Idx" "Name" "Size" "VMA" "Type";
+  List.iteri (fun index -> on_segment (iter_sections (debug_section index))) commands
+
+let run section_headers files () =
+  match section_headers with
+  | true -> List.iter print_section_headers files
+  | false ->
+     Printf.printf "Section headers flag required please call with `--section-headers`.\n";
+     exit(2)
+
+open Cmdliner
+
+let section_headers =
+  let doc = "Display summaries of the headers for each section.." in
+  let info = Arg.(info ["section-headers"] ~doc) in
+  Arg.value (Arg.flag info)
+
+let files =
+  let doc = "Object FILEs to read." in
+  Arg.(non_empty & pos_all file [] & info [] ~docv:"FILE" ~doc)
+
+let section_headers_t =
+  Term.(const run $ section_headers $ files $ const ())
+
+let cmd =
+  let doc = "OCaml object file dumper." in
+  let info = Cmd.info "objdump" ~doc in
+  Cmd.v info section_headers_t
+
+let () = exit @@ Cmd.eval ~catch:true cmd