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authorBjörn Gustavsson <[email protected]>2016-05-30 14:37:27 +0200
committerBjörn Gustavsson <[email protected]>2016-05-31 13:03:24 +0200
commitb6e4235b7ce8851fdd37ba7308d2e58d8b996fd6 (patch)
tree6a4f3ea24b33ba1cc85039f1cbf11a3c22553dcd
parent64375c745822840f1b3c910b5bd60e663b107faa (diff)
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beam_validator: Strengthen validation of match states
We want to find bugs in the compiler during compilation. Validation of match contexts was weak, which could allow serious bugs in the generated code to slip through.
-rw-r--r--lib/compiler/src/beam_validator.erl80
1 files changed, 56 insertions, 24 deletions
diff --git a/lib/compiler/src/beam_validator.erl b/lib/compiler/src/beam_validator.erl
index 1cb90a043a..13aa31b7c9 100644
--- a/lib/compiler/src/beam_validator.erl
+++ b/lib/compiler/src/beam_validator.erl
@@ -161,9 +161,10 @@ validate_0(Module, [{function,Name,Ar,Entry,Code}|Fs], Ft) ->
% in the module (those that start with bs_start_match2).
}).
-%% Match state.
+%% Match context type.
-record(ms,
- {valid=0 :: non_neg_integer(), %Valid slots
+ {id=make_ref() :: reference(), %Unique ID.
+ valid=0 :: non_neg_integer(), %Valid slots
slots=0 :: non_neg_integer() %Number of slots
}).
@@ -834,7 +835,7 @@ kill_state_1(Vst) ->
%% The stackframe must be initialized.
%% The instruction will return to the instruction following the call.
call(Name, Live, #vst{current=St}=Vst) ->
- verify_live(Live, Vst),
+ verify_call_args(Name, Live, Vst),
verify_y_init(Vst),
case return_type(Name, Vst) of
Type when Type =/= exception ->
@@ -846,44 +847,74 @@ call(Name, Live, #vst{current=St}=Vst) ->
%% Tail call.
%% The stackframe must have a known size and be initialized.
%% Does not return to the instruction following the call.
-tail_call(Name, Live, Vst) ->
+tail_call(Name, Live, Vst0) ->
+ verify_y_init(Vst0),
+ Vst = deallocate(Vst0),
verify_call_args(Name, Live, Vst),
- verify_y_init(Vst),
verify_no_ct(Vst),
kill_state(Vst).
verify_call_args(_, 0, #vst{}) ->
ok;
verify_call_args({f,Lbl}, Live, Vst) when is_integer(Live)->
- Verify = fun(R) ->
- case get_move_term_type(R, Vst) of
- #ms{} ->
- verify_call_match_context(Lbl, Vst);
- _ ->
- ok
- end
- end,
- verify_call_args_1(Live, Verify, Vst);
+ verify_local_call(Lbl, Live, Vst);
verify_call_args(_, Live, Vst) when is_integer(Live)->
- Verify = fun(R) -> get_term_type(R, Vst) end,
- verify_call_args_1(Live, Verify, Vst);
+ verify_call_args_1(Live, Vst);
verify_call_args(_, Live, _) ->
error({bad_number_of_live_regs,Live}).
-verify_call_args_1(0, _, _) -> ok;
-verify_call_args_1(N, Verify, Vst) ->
+verify_call_args_1(0, _) -> ok;
+verify_call_args_1(N, Vst) ->
X = N - 1,
- Verify({x,X}),
- verify_call_args_1(X, Verify, Vst).
+ get_term_type({x,X}, Vst),
+ verify_call_args_1(X, Vst).
+
+verify_local_call(Lbl, Live, Vst) ->
+ case all_ms_in_x_regs(Live, Vst) of
+ [{R,Ctx}] ->
+ %% Verify that there is a suitable bs_start_match2 instruction.
+ verify_call_match_context(Lbl, R, Vst),
+
+ %% Since the callee has consumed the match context,
+ %% there must be no additional copies in Y registers.
+ #ms{id=Id} = Ctx,
+ case ms_in_y_regs(Id, Vst) of
+ [] ->
+ ok;
+ [_|_]=Ys ->
+ error({multiple_match_contexts,[R|Ys]})
+ end;
+ [_,_|_]=Xs0 ->
+ Xs = [R || {R,_} <- Xs0],
+ error({multiple_match_contexts,Xs});
+ [] ->
+ ok
+ end.
+
+all_ms_in_x_regs(0, _Vst) ->
+ [];
+all_ms_in_x_regs(Live0, Vst) ->
+ Live = Live0 - 1,
+ R = {x,Live},
+ case get_move_term_type(R, Vst) of
+ #ms{}=M ->
+ [{R,M}|all_ms_in_x_regs(Live, Vst)];
+ _ ->
+ all_ms_in_x_regs(Live, Vst)
+ end.
+
+ms_in_y_regs(Id, #vst{current=#st{y=Ys0}}) ->
+ Ys = gb_trees:to_list(Ys0),
+ [Y || {Y,#ms{id=OtherId}} <- Ys, OtherId =:= Id].
-verify_call_match_context(Lbl, #vst{ft=Ft}) ->
+verify_call_match_context(Lbl, Ctx, #vst{ft=Ft}) ->
case gb_trees:lookup(Lbl, Ft) of
none ->
error(no_bs_start_match2);
{value,[{test,bs_start_match2,_,_,[Ctx,_],Ctx}|_]} ->
ok;
- {value,[{test,bs_start_match2,_,_,[Bin,_,_],Ctx}|_]} ->
- error({binary_and_context_regs_different,Bin,Ctx})
+ {value,[{test,bs_start_match2,_,_,_,_}=I|_]} ->
+ error({unsuitable_bs_start_match2,I})
end.
allocate(Zero, Stk, Heap, Live, #vst{current=#st{numy=none}=St}=Vst0) ->
@@ -1388,7 +1419,8 @@ merge_types(bool, {atom,A}) ->
merge_bool(A);
merge_types({atom,A}, bool) ->
merge_bool(A);
-merge_types(#ms{valid=B0,slots=Slots}=M,#ms{valid=B1,slots=Slots}) ->
+merge_types(#ms{id=Id,valid=B0,slots=Slots}=M,
+ #ms{id=Id,valid=B1,slots=Slots}) ->
M#ms{valid=B0 bor B1,slots=Slots};
merge_types(#ms{}=M, _) ->
M;