stops proposing aliases as potential subroutine names (#1356)

Partially reverts #1355 by removing the gossiper, which was promising,
under low certainity, aliases as subroutine names. It turned to
produce name conflicts on many real binaries and, in general, was
wrong idea, as we from the start was using aliases as dump for
conflicting names.

Author: ivg

lib/bap/bap_project.ml

@@ -85,9 +85,11 @@ module Symbols = struct
       fun x ->
         let x = Int64.(x land mask) in
         Bitvec.(int64 x mod m) in
-    let add_alias aliases addr alias = Map.update aliases addr ~f:(function
+    let add_alias tab addr alias = {
+      tab with aliases = Map.update tab.aliases addr ~f:(function
         | None -> Set.singleton (module String) alias
-        | Some names -> Set.add names alias) in
+        | Some names -> Set.add names alias)
+    } in
     let pp_comma ppf () = Format.pp_print_string ppf ", " in
     let pp_addrs =
       Format.pp_print_list ~pp_sep:pp_comma Bitvec.pp
@@ -105,29 +107,26 @@ module Symbols = struct
       Seq.fold roots ~init:(Set.empty (module Bitvec_order))
         ~f:(fun xs x -> Set.add xs (to_addr x)) in
     let+ named_symbols = collect Image.Scheme.named_symbol in
-    let init = Bap_relation.empty Bitvec.compare String.compare in
-    Seq.fold named_symbols ~init ~f:(fun rel (data,name) ->
+    let init = {empty with roots},
+               Bap_relation.empty Bitvec.compare String.compare in
+    Seq.fold named_symbols ~init ~f:(fun (tab,rel) (data,name) ->
         let addr = to_addr data in
         if Set.mem roots addr && is_ident name
-        then Bap_relation.add rel (to_addr data) name
-        else rel) |> fun rel ->
-    Bap_relation.matching rel {empty with roots}
+        then tab,Bap_relation.add rel (to_addr data) name
+        else add_alias tab addr name, rel) |> fun (table,rel) ->
+    Bap_relation.matching rel table
       ~saturated:(fun k v t -> {
             t with names = Map.add_exn t.names k v
           })
-      ~unmatched:(fun reason t -> {
-            t with aliases = match reason with
+      ~unmatched:(fun reason t -> match reason with
           | Non_injective_fwd (addrs,name) ->
             info "the symbol %s has ambiguous addresses: %a@\n"
               name pp_addrs addrs;
-            List.fold addrs ~init:t.aliases ~f:(fun aliases addr ->
-                add_alias aliases addr name)
+            t
           | Non_injective_bwd (names,addr) ->
             info "the symbol at %a has ambiguous names: %a@\n"
               Bitvec.pp addr pp_names names;
-            List.fold names ~init:t.aliases ~f:(fun aliases name ->
-                add_alias aliases addr name)
-          })
+            t)
 
   let build_table t spec = match Ogre.eval (from_spec t) spec with
     | Ok x -> x
@@ -192,24 +191,6 @@ module Symbols = struct
       match Map.find aliases addr with
       | None -> Set.empty (module String)
       | Some aliases -> aliases
-
-  let gossiper = KB.Agent.register
-      ~package:"bap" "symbols-gossiper"
-      ~desc:"propses an alias as a possible name"
-      ~reliability:KB.Agent.unreliable
-
-  let gossiped_aliases : unit =
-    KB.Rule.(begin
-        declare "provides aliases as names" |>
-        require Image.Spec.slot |>
-        provide Theory.Label.possible_name |>
-        comment "uses aliases as an unreliable source of symbol names";
-      end);
-    KB.propose gossiper Theory.Label.possible_name @@ fun obj ->
-    let+ aliases = KB.collect Theory.Label.aliases obj in
-    match Set.find aliases ~f:is_ident with
-    | None -> Set.max_elt aliases
-    | ident -> ident
 end
 
 
@@ -233,6 +214,8 @@ let with_filename spec target _code memory path f =
       !!(Some unit)) f
 
 
+
+
 module State = struct
   open KB.Syntax
   module Dis = Bap_disasm_driver