path: root/driver/Interp.ml

(* *********************************************************************)
(*                                                                     *)
(*              The Compcert verified compiler                         *)
(*                                                                     *)
(*          Xavier Leroy, INRIA Paris-Rocquencourt                     *)
(*                                                                     *)
(*  Copyright Institut National de Recherche en Informatique et en     *)
(*  Automatique.  All rights reserved.  This file is distributed       *)
(*  under the terms of the INRIA Non-Commercial License Agreement.     *)
(*                                                                     *)
(* *********************************************************************)

(* Interpreting CompCert C sources *)

type caml_float = float

open Format
open Camlcoq
open Datatypes
open BinPos
open BinInt
open AST
open Integers
open Floats
open Values
open Memory
open Globalenvs
open Events
open Ctypes
open Cop
open Csyntax
open Csem
open Clflags

(* Configuration *)

let trace = ref 1   (* 0 if quiet, 1 if normally verbose, 2 if full trace *)

type mode = First | Random | All

let mode = ref First

(* Printing events *)

let print_id_ofs p (id, ofs) =
  let id = extern_atom id and ofs = camlint_of_coqint ofs in
  if ofs = 0l
  then fprintf p " %s" id
  else fprintf p " %s%+ld" id ofs

let print_eventval p = function
  | EVint n -> fprintf p "%ld" (camlint_of_coqint n)
  | EVfloat f -> fprintf p "%F" (camlfloat_of_coqfloat f)
  | EVptr_global(id, ofs) -> fprintf p "&%a" print_id_ofs (id, ofs)

let print_eventval_list p = function
  | [] -> ()
  | v1 :: vl ->
      print_eventval p v1;
      List.iter (fun v -> fprintf p ",@ %a" print_eventval v) vl

let print_event p = function
  | Event_syscall(id, args, res) ->
      fprintf p "extcall %s(%a) -> %a"
                (extern_atom id)
                print_eventval_list args
                print_eventval res
  | Event_vload(chunk, id, ofs, res) ->
      fprintf p "volatile load %s[&%s%+ld] -> %a"
                (PrintAST.name_of_chunk chunk)
                (extern_atom id) (camlint_of_coqint ofs)
                print_eventval res
  | Event_vstore(chunk, id, ofs, arg) ->
      fprintf p "volatile store %s[&%s%+ld] <- %a"
                (PrintAST.name_of_chunk chunk)
                (extern_atom id) (camlint_of_coqint ofs)
                print_eventval arg
  | Event_annot(text, args) ->
      fprintf p "annotation \"%s\" %a"
                (extern_atom text)
                print_eventval_list args

(* Printing states *)

let name_of_fundef prog fd =
  let rec find_name = function
  | [] -> "<unknown function>"
  | (id, Gfun fd') :: rem ->
      if fd = fd' then extern_atom id else find_name rem
  | (id, Gvar v) :: rem ->
      find_name rem
  in find_name prog.prog_defs

let name_of_function prog fn =
  name_of_fundef prog (Internal fn)

let invert_local_variable e b =
  Maps.PTree.fold 
    (fun res id (b', _) -> if b = b' then Some id else res)
    e None

let print_pointer ge e p (b, ofs) =
  match invert_local_variable e b with
  | Some id -> print_id_ofs p (id, ofs)
  | None ->
      match Genv.invert_symbol ge b with
      | Some id -> print_id_ofs p (id, ofs)
      | None -> ()

let print_val = PrintCsyntax.print_value

let print_val_list p vl =
  match vl with
  | [] -> ()
  | v1 :: vl ->
      print_val p v1;
      List.iter (fun v -> fprintf p ",@ %a" print_val v) vl

let print_state p (prog, ge, s) =
  match s with
  | State(f, s, k, e, m) ->
      PrintCsyntax.print_pointer_hook := print_pointer ge e;
      fprintf p "in function %s, statement@ @[<hv 0>%a@]"
              (name_of_function prog f)
              PrintCsyntax.print_stmt s
  | ExprState(f, r, k, e, m) ->
      PrintCsyntax.print_pointer_hook := print_pointer ge e;
      fprintf p "in function %s, expression@ @[<hv 0>%a@]"
              (name_of_function prog f)
              PrintCsyntax.print_expr r
  | Callstate(fd, args, k, m) ->
      PrintCsyntax.print_pointer_hook := print_pointer ge Maps.PTree.empty;
      fprintf p "calling@ @[<hov 2>%s(%a)@]"
              (name_of_fundef prog fd)
              print_val_list args
  | Returnstate(res, k, m) ->
      PrintCsyntax.print_pointer_hook := print_pointer ge Maps.PTree.empty;
      fprintf p "returning@ %a"
              print_val res
  | Stuckstate ->
      fprintf p "stuck after an undefined expression"

(* Comparing memory states *)

let compare_mem m1 m2 = (* should permissions be taken into account? *)
  Pervasives.compare (m1.Mem.nextblock, m1.Mem.mem_contents)
                     (m2.Mem.nextblock, m1.Mem.mem_contents)

(* Comparing continuations *)

let some_expr = Evar(Coq_xH, Tvoid)

let rank_cont = function
  | Kstop -> 0
  | Kdo _ -> 1
  | Kseq _ -> 2
  | Kifthenelse _ -> 3
  | Kwhile1 _ -> 4
  | Kwhile2 _ -> 5
  | Kdowhile1 _ -> 6
  | Kdowhile2 _ -> 7
  | Kfor2 _ -> 8
  | Kfor3 _ -> 9
  | Kfor4 _ -> 10
  | Kswitch1 _ -> 11
  | Kswitch2 _ -> 12
  | Kreturn _ -> 13
  | Kcall _ -> 14

let rec compare_cont k1 k2 =
  if k1 == k2 then 0 else
  match k1, k2 with
  | Kstop, Kstop -> 0
  | Kdo k1, Kdo k2 -> compare_cont k1 k2
  | Kseq(s1, k1), Kseq(s2, k2) ->  
      let c = compare s1 s2 in if c <> 0 then c else compare_cont k1 k2
  | Kifthenelse(s1, s1', k1), Kifthenelse(s2, s2', k2) ->
      let c = compare (s1,s1') (s2,s2') in
      if c <> 0 then c else compare_cont k1 k2
  | Kwhile1(e1, s1, k1), Kwhile1(e2, s2, k2) ->
      let c = compare (e1,s1) (e2,s2) in
      if c <> 0 then c else compare_cont k1 k2
  | Kwhile2(e1, s1, k1), Kwhile2(e2, s2, k2) ->
      let c = compare (e1,s1) (e2,s2) in
      if c <> 0 then c else compare_cont k1 k2
  | Kdowhile1(e1, s1, k1), Kdowhile1(e2, s2, k2) ->
      let c = compare (e1,s1) (e2,s2) in
      if c <> 0 then c else compare_cont k1 k2
  | Kdowhile2(e1, s1, k1), Kdowhile2(e2, s2, k2) ->
      let c = compare (e1,s1) (e2,s2) in
      if c <> 0 then c else compare_cont k1 k2
  | Kfor2(e1, s1, s1', k1), Kfor2(e2, s2, s2', k2) ->
      let c = compare (e1,s1,s1') (e2,s2,s2') in
      if c <> 0 then c else compare_cont k1 k2
  | Kfor3(e1, s1, s1', k1), Kfor3(e2, s2, s2', k2) ->
      let c = compare (e1,s1,s1') (e2,s2,s2') in
      if c <> 0 then c else compare_cont k1 k2
  | Kfor4(e1, s1, s1', k1), Kfor4(e2, s2, s2', k2) ->
      let c = compare (e1,s1,s1') (e2,s2,s2') in
      if c <> 0 then c else compare_cont k1 k2
  | Kswitch1(sl1, k1), Kswitch1(sl2, k2) ->
      let c = compare sl1 sl2 in
      if c <> 0 then c else compare_cont k1 k2
  | Kreturn k1, Kreturn k2 ->
      compare_cont k1 k2
  | Kcall(f1, e1, c1, ty1, k1), Kcall(f2, e2, c2, ty2, k2) ->
      let c = compare (f1, e1, c1 some_expr, ty1) (f2, e2, c2 some_expr, ty2) in
      if c <> 0 then c else compare_cont k1 k2
  | _, _ ->
      compare (rank_cont k1) (rank_cont k2)

(* Comparing states *)

let rank_state = function
  | State _ -> 0
  | ExprState _ -> 1
  | Callstate _ -> 2
  | Returnstate _ -> 3
  | Stuckstate -> 4

let compare_state s1 s2 =
  if s1 == s2 then 0 else
  match s1, s2 with
  | State(f1,s1,k1,e1,m1), State(f2,s2,k2,e2,m2) ->
      let c = compare (f1,s1,e1) (f2,s2,e2) in if c <> 0 then c else
      let c = compare_cont k1 k2 in if c <> 0 then c else
      compare_mem m1 m2
  | ExprState(f1,r1,k1,e1,m1), ExprState(f2,r2,k2,e2,m2) ->
      let c = compare (f1,r1,e1) (f2,r2,e2) in if c <> 0 then c else
      let c = compare_cont k1 k2 in if c <> 0 then c else
      compare_mem m1 m2
  | Callstate(fd1,args1,k1,m1), Callstate(fd2,args2,k2,m2) ->
      let c = compare (fd1,args1) (fd2,args2) in if c <> 0 then c else
      let c = compare_cont k1 k2 in if c <> 0 then c else
      compare_mem m1 m2
  | Returnstate(res1,k1,m1), Returnstate(res2,k2,m2) ->
      let c = compare res1 res2 in if c <> 0 then c else
      let c = compare_cont k1 k2 in if c <> 0 then c else
      compare_mem m1 m2
  | _, _ ->
      compare (rank_state s1) (rank_state s2)

module StateSet =
  Set.Make(struct
             type t = state * Determinism.world
             let compare (s1,w1) (s2,w2) = compare_state s1 s2
           end)

(* Extract a string from a global pointer *)

let extract_string ge m id ofs =
  let b = Buffer.create 80 in
  let rec extract blk ofs =
    match Memory.Mem.load Mint8unsigned m blk ofs with
    | Some(Vint n) ->
        let c = Char.chr (Int32.to_int (camlint_of_coqint n)) in
        if c = '\000' then begin
          Some(Buffer.contents b)
        end else begin
          Buffer.add_char b c; 
          extract blk (coq_Zsucc ofs)
        end
    | _ ->
        None in
  match Genv.find_symbol ge id with
  | None -> None
  | Some blk -> extract blk ofs

(* Emulation of printf *)

(* All ISO C 99 formats except size modifiers [ll] (long long) and [L]
   (long double) *)

let re_conversion = Str.regexp
  "%[-+0# ]*[0-9]*\\(\\.[0-9]*\\)?\\([lhjzt]\\|hh\\)?\\([aAcdeEfgGinopsuxX%]\\)"

external format_float: string -> caml_float -> string
  = "caml_format_float"
external format_int32: string -> int32 -> string
  = "caml_int32_format"

let do_printf ge m fmt args =

  let b = Buffer.create 80 in
  let len = String.length fmt in

  let opt_search_forward pos =
    try Some(Str.search_forward re_conversion fmt pos)
    with Not_found -> None in

  let rec scan pos args =
    if pos < len then begin
    match opt_search_forward pos with
    | None ->
        Buffer.add_substring b fmt pos (len - pos)
    | Some pos1 ->
        Buffer.add_substring b fmt pos (pos1 - pos);
        let pat = Str.matched_string fmt
        and conv = Str.matched_group 3 fmt
        and pos' = Str.match_end() in
        match args, conv.[0] with
        | _, '%' ->
            Buffer.add_char b '%';
            scan pos' args
        | [], _ ->
            Buffer.add_string b "<missing argument>";
            scan pos' []
        | EVint i :: args', ('d'|'i'|'u'|'o'|'x'|'X'|'c') ->
            Buffer.add_string b (format_int32 pat (camlint_of_coqint i));
            scan pos' args'
        | EVfloat f :: args', ('f'|'e'|'E'|'g'|'G'|'a') ->
            Buffer.add_string b (format_float pat (camlfloat_of_coqfloat f));
            scan pos' args'
        | EVptr_global(id, ofs) :: args', 's' ->
            Buffer.add_string b
              (match extract_string ge m id ofs with
               | Some s -> s
               | None -> "<bad string>");
            scan pos' args'
        | EVptr_global(id, ofs) :: args', 'p' ->
            Printf.bprintf b "<&%s%+ld>" (extern_atom id) (camlint_of_coqint ofs);
            scan pos' args'
        | _ :: args', _ ->
            Buffer.add_string b "<formatting error>";
            scan pos' args'
    end
  in scan 0 args; Buffer.contents b

(* Implementing external functions *)

let re_stub = Str.regexp "\\$[if]*$"

let chop_stub name = Str.replace_first re_stub "" name

let (>>=) opt f = match opt with None -> None | Some arg -> f arg

let rec world ge m =
  Determinism.World(world_io ge m, world_vload ge m, world_vstore ge m)

and world_io ge m id args =
  match chop_stub(extern_atom id), args with
  | "printf", EVptr_global(id, ofs) :: args' ->
      flush stderr;
      begin match extract_string ge m id ofs with
      | Some fmt -> print_string (do_printf ge m fmt args')
      | None -> print_string "<bad printf>\n"
      end;
      flush stdout;
      Some(EVint Integers.Int.zero, world ge m)
  | _, _ ->
      None

and world_vload ge m chunk id ofs =
  Genv.find_symbol ge id >>= fun b ->
  Mem.load chunk m b ofs >>= fun v ->
  Cexec.eventval_of_val ge v (type_of_chunk chunk) >>= fun ev ->
  Some(ev, world ge m)

and world_vstore ge m chunk id ofs ev =
  Genv.find_symbol ge id >>= fun b ->
  Cexec.val_of_eventval ge ev (type_of_chunk chunk) >>= fun v ->
  Mem.store chunk m b ofs v >>= fun m' ->
  Some(world ge m')

let do_event p ge time w ev =
  if !trace >= 1 then
    fprintf p "@[<hov 2>Time %d: observable event: %a@]@."
              time print_event ev;
  (* Return new world after external action *)
  match ev with
  | Event_vstore(chunk, id, ofs, v) ->
      begin match Determinism.nextworld_vstore w chunk id ofs v with
      | None -> assert false
      | Some w' -> w'
      end
  | _ -> w

let rec do_events p ge time w t =
  match t with
  | [] -> w
  | ev :: t' -> do_events p ge time (do_event p ge time w ev) t'

(* Debugging stuck expressions *)

let (|||) a b = a || b (* strict boolean or *)

let diagnose_stuck_expr p ge w f a kont e m =
  let rec diagnose k a =
  (* diagnose subexpressions first *)
  let found =
    match k, a with
    | LV, Ederef(r, ty) -> diagnose RV r
    | LV, Efield(r, f, ty) -> diagnose RV r
    | RV, Evalof(l, ty) -> diagnose LV l
    | RV, Eaddrof(l, ty) -> diagnose LV l
    | RV, Eunop(op, r1, ty) -> diagnose RV r1
    | RV, Ebinop(op, r1, r2, ty) -> diagnose RV r1 ||| diagnose RV r2
    | RV, Ecast(r1, ty) -> diagnose RV r1
    | RV, Econdition(r1, r2, r3, ty) -> diagnose RV r1
    | RV, Eassign(l1, r2, ty) -> diagnose LV l1 ||| diagnose RV r2
    | RV, Eassignop(op, l1, r2, tyres, ty) -> diagnose LV l1 ||| diagnose RV r2
    | RV, Epostincr(id, l, ty) -> diagnose LV l
    | RV, Ecomma(r1, r2, ty) -> diagnose RV r1
    | RV, Eparen(r1, ty) -> diagnose RV r1
    | RV, Ecall(r1, rargs, ty) -> diagnose RV r1 ||| diagnose_list rargs
    | _, _ -> false in
  if found then true else begin
    let l = Cexec.step_expr ge e w k a m in
    if List.exists (fun (ctx,red) -> red = Cexec.Stuckred) l then begin
      PrintCsyntax.print_pointer_hook := print_pointer ge e;
      fprintf p "@[<hov 2>Stuck subexpression:@ %a@]@."
              PrintCsyntax.print_expr a;
      true
    end else false
  end

  and diagnose_list al =
    match al with
    | Enil -> false
    | Econs(a1, al') -> diagnose RV a1 ||| diagnose_list al'

  in diagnose RV a

let diagnose_stuck_state p ge w = function
  | ExprState(f,a,k,e,m) -> ignore(diagnose_stuck_expr p ge w f a k e m)
  | _ -> ()

(* Exploration *)

let do_step p prog ge time (s, w) =
  if !trace >= 2 then
    fprintf p "@[<hov 2>Time %d: %a@]@." time print_state (prog, ge, s);
  match Cexec.at_final_state s with
  | Some r ->
      if !trace >= 1 then begin
        fprintf p "Time %d: program terminated (exit code = %ld)@."
                  time (camlint_of_coqint r);
        []
      end else begin
        exit (Int32.to_int (camlint_of_coqint r))
      end
  | None ->
      let l = Cexec.do_step ge w s in
      if l = [] || List.exists (fun (t,s) -> s = Stuckstate) l then begin
        pp_set_max_boxes p 1000;
        fprintf p "@[<hov 2>Stuck state: %a@]@." print_state (prog, ge, s);
        diagnose_stuck_state p ge w s;
        fprintf p "ERROR: Undefined behavior@.";
        exit 126
      end else begin
        List.map (fun (t, s') -> (s', do_events p ge time w t)) l
      end

let rec explore p prog ge time ss =
  let succs =
    StateSet.fold (fun sw l -> do_step p prog ge time sw @ l) ss [] in
  if succs <> [] then begin
    let ss' =
      match !mode with
      | First -> StateSet.singleton (List.hd succs)
      | Random -> StateSet.singleton (List.nth succs (Random.int (List.length succs)))
      | All -> List.fold_right StateSet.add succs StateSet.empty in
    explore p prog ge (time + 1) ss'
  end

(* The variant of the source program used to build the world for
   executing events.  
   Volatile variables are turned into non-volatile ones, so that
     reads and writes can be performed.
   Readonly variables are kept, for string literals in particular.
   Writable variables are turned into empty vars, so that
     reads and writes just fail.
   Functions are preserved, although they are not used. *)

let world_program prog =
  let change_def (id, gd) =
    match gd with
    | Gvar gv ->
        let gv' =
          if gv.gvar_volatile then
            {gv with gvar_readonly = false; gvar_volatile = false}
          else if gv.gvar_readonly then
            gv
          else
            {gv with gvar_init = []} in
        (id, Gvar gv')
    | Gfun fd ->
        (id, gd) in
 {prog with prog_defs = List.map change_def prog.prog_defs}

(* Massaging the program to get a suitable "main" function *)

let change_main_function p old_main old_main_ty =
  let old_main = Evalof(Evar(old_main, old_main_ty), old_main_ty) in
  let arg1 = Eval(Vint(coqint_of_camlint 0l), type_int32s) in
  let arg2 = arg1 in
  let body =
    Sreturn(Some(Ecall(old_main, Econs(arg1, Econs(arg2, Enil)), type_int32s))) in
  let new_main_fn =
    { fn_return = type_int32s; fn_params = []; fn_vars = []; fn_body = body } in
  let new_main_id = intern_string "___main" in
  { prog_main = new_main_id;
    prog_defs = (new_main_id, Gfun(Internal new_main_fn)) :: p.prog_defs }

let rec find_main_function name = function
  | [] -> None
  | (id, Gfun fd) :: gdl -> if id = name then Some fd else find_main_function name gdl
  | (id, Gvar v) :: gdl -> find_main_function name gdl

let fixup_main p =
  match find_main_function p.prog_main p.prog_defs with
  | None ->
      fprintf err_formatter "ERROR: no main() function";
      None
  | Some main_fd ->
      match type_of_fundef main_fd with
      | Tfunction(Tnil, Tint(I32, Signed, _)) ->
          Some p
      | Tfunction(Tcons(Tint _, Tcons(Tpointer(Tpointer(Tint(I8,_,_),_),_), Tnil)),
                  Tint _) as ty ->
          Some (change_main_function p p.prog_main ty)
      | _ ->
          fprintf err_formatter "ERROR: wrong type for main() function";
          None

(* Execution of a whole program *)

let execute prog =
  Random.self_init();
  let p = std_formatter in
  pp_set_max_indent p 30;
  pp_set_max_boxes p 10;
  match fixup_main prog with
  | None -> ()
  | Some prog1 ->
      let wprog = world_program prog1 in
      let wge = Genv.globalenv wprog in
      match Genv.init_mem wprog with
      | None ->
          fprintf p "ERROR: World memory state undefined@."
      | Some wm ->
      match Cexec.do_initial_state prog1 with
      | None ->
          fprintf p "ERROR: Initial state undefined@."
      | Some(ge, s) ->
          explore p prog1 ge 0 (StateSet.singleton (s, world wge wm))