path: root/checklink/Frameworks.ml

open Asm
open AST
open BinPos
open ELF_types
open Lens
open Library

type log_entry =
  | DEBUG   of string
  | ERROR   of string
  | INFO    of string
  | WARNING of string

type byte_chunk_desc =
  | ELF_header
  | ELF_progtab
  | ELF_shtab
  | ELF_section_strtab
  | ELF_symbol_strtab
  | Symtab_data        of elf32_sym
  | Symtab_function    of elf32_sym
  | Data_symbol        of elf32_sym
  | Function_symbol    of elf32_sym
  | Zero_symbol
  | Stub               of string
  | Jumptable
  | Float_literal      of float
  | Padding
  | Unknown            of string

(* This type specifies whether its argument was inferred by the tool or provided
   via a config file. *)
type 'a inferrable =
  | Inferred of 'a
  | Provided of 'a

let from_inferrable = function
| Inferred(x) -> x
| Provided(x) -> x

(** This framework is carried along while analyzing the whole ELF file.
*)
type e_framework = {
  elf: elf;
  log: log_entry list;
  (** Every time a chunk of the ELF file is checked, it is added to this list.
      The first two fields are the start and stop offsets, the third is an
      alignment constraint, the last is a description. *)
  chkd_bytes_list: (int32 * int32 * int * byte_chunk_desc) list;
  chkd_fun_syms: bool array;
  chkd_data_syms: bool array;
  (** The mapping from CompCert sections to ELF sections will be inferred along
      the way. This way, we can check things without prior knowledge of the
      linker script. The set holds conflicts for the mapping, if more than one
      mapping is inferred. These are reported once, at the end. *)
  section_map: (string inferrable * StringSet.t) StringMap.t;
  (** We will assign a virtual address to each register that can act as an SDA
      base register. *)
  sda_map: (int32 inferrable) IntMap.t;
  (** Contains the symbols that we expect to be missing from the .sdump files *)
  missing_syms: StringSet.t;
}

module PosOT = struct
  type t = positive
  let compare = Pervasives.compare
end

module PosMap = Map.Make(PosOT)

(** This framework is carried along while analyzing one .sdump file, which
    may contain multiple functions. *)
type s_framework = {
  ef: e_framework;
  program: Asm.program;
  (** Maps every CompCert ident to a string. This will not be the exact name of
      the symbol in the ELF file though: CompCert does some mangling for
      variadic functions, and some linkers do some versioning in their symbols.
  *)
  ident_to_name: (ident, string) Hashtbl.t;
  (** Maps a CompCert ident to a list of candidates symbol indices. We can only
      try to match symbols by name until we begin the analysis, so multiple
      static symbols might match a given name. The list will be narrowed down
      as we learn more about the contents of the symbol.
  *)
  ident_to_sym_ndx: (int list) PosMap.t;
  (** CompCert generates stubs for some functions, which we will aggregate as we
      discover them. *)
  stub_ident_to_vaddr: int32 PosMap.t;
  (** This structure is imported from CompCert's .sdump, and describes each
      atom. *)
  atoms: (ident, C2C.atom_info) Hashtbl.t;
}

(** This framework is carried while analyzing a single function. *)
type f_framework = {
  sf: s_framework;
  (** The symbol index of the current function. *)
  this_sym_ndx: int;
  (** The CompCert ident of the current function. *)
  this_ident: ident;
  (** A mapping from local labels to virtual addresses. *)
  label_to_vaddr: int32 PosMap.t;
  (** A list of all the labels encountered while processing the body. *)
  label_list: label list;
}

(** A few lenses that prove useful for manipulating frameworks.
*)

let sf_ef: (s_framework, e_framework) Lens.t = {
  get = (fun sf -> sf.ef);
  set = (fun ef sf -> { sf with ef = ef });
}

let ff_sf: (f_framework, s_framework) Lens.t = {
  get = (fun ff -> ff.sf);
  set = (fun sf ff -> { ff with sf = sf });
}

let ff_ef = ff_sf |-- sf_ef

let log = {
  get = (fun ef -> ef.log);
  set = (fun l ef -> { ef with log = l });
}

let section_map = {
  get = (fun ef -> ef.section_map);
  set = (fun m ef -> { ef with section_map = m });
}

let sda_map = {
  get = (fun ef -> ef.sda_map);
  set = (fun m ef -> { ef with sda_map = m });
}

let ident_to_sym_ndx = {
  get = (fun sf -> sf.ident_to_sym_ndx);
  set = (fun i sf -> { sf with ident_to_sym_ndx = i });
}

let stub_ident_to_vaddr = {
  get = (fun sf -> sf.stub_ident_to_vaddr);
  set = (fun i sf -> { sf with stub_ident_to_vaddr = i });
}

(** Adds a range to the checked bytes list.
*)
let add_range (start: int32) (length: int32) (align: int) (bcd: byte_chunk_desc)
    (efw: e_framework): e_framework =
  assert (0l <= start && 0l < length);
  let stop = Safe32.(start + length - 1l) in
  {
    efw with
      chkd_bytes_list =
      (* Float constants can appear several times in the code, we don't
         want to add them multiple times *)
      if (List.exists
            (fun (a, b, _, _) -> a = start && b = stop)
            efw.chkd_bytes_list)
      then efw.chkd_bytes_list
      else (start, stop, align, bcd) :: efw.chkd_bytes_list;
  }

(** Some useful combinators to make it all work.
*)

(* external ( >>> ) : 'a -> ('a -> 'b) -> 'b = "%revapply" *)
let ( >>> ) (a: 'a) (f: 'a -> 'b): 'b = f a

let ( >>^ ) (a: 'a or_err) (f: 'a -> 'b): 'b or_err =
  match a with
  | ERR(s) -> ERR(s)
  | OK(x) -> OK(f x)

let ( >>= ) (a: 'a or_err) (f: 'a -> 'b or_err): 'b or_err =
  match a with
  | ERR(s) -> ERR(s)
  | OK(x) -> f x

let ( ^%=? ) (lens: ('a, 'b) Lens.t) (transf: 'b -> 'b or_err)
    (arg: 'a): 'a or_err =
  let focus = arg |. lens in
  match transf focus with
  | OK(res) -> OK((lens ^= res) arg)
  | ERR(s) -> ERR(s)

(** Finally, some printers.
*)

let format_logtype = Printf.sprintf "%10s"

let string_of_log_entry show_debug entry =
  match entry with
  | DEBUG(s)   -> if show_debug then (format_logtype "DEBUG: ") ^ s else ""
  | ERROR(s)   -> (format_logtype "ERROR: ") ^ s
  | INFO(s)    -> (format_logtype "INFO: ") ^ s
  | WARNING(s) -> (format_logtype "WARNING: ") ^ s

let fatal s = failwith ((format_logtype "FATAL: ") ^ s)

let verbose_elfmap = ref false

let string_of_byte_chunk_desc = function
| ELF_header -> "ELF header"
| ELF_progtab -> "ELF program header table"
| ELF_shtab -> "ELF section header table"
| ELF_section_strtab -> "ELF section string table"
| ELF_symbol_strtab -> "ELF symbol string table"
| Symtab_data(s) -> "Data symbol table entry: " ^ s.st_name
| Symtab_function(s) -> "Function symbol table entry: " ^ s.st_name
| Data_symbol(s) -> "Data symbol: " ^ s.st_name
| Function_symbol(s) -> "Function symbol: " ^ s.st_name
| Zero_symbol -> "Symbol 0"
| Stub(s) -> "Stub for: " ^ s
| Jumptable -> "Jump table"
| Float_literal(f) -> "Float literal: " ^ string_of_float f
| Padding -> "Padding"
| Unknown(s) -> "???" ^ (if !verbose_elfmap then s else "")