From 3105c314beff5c9b226d8e863d32c4329706353c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Fri, 24 Nov 2017 12:50:25 +0100
Subject: Fix purging of modules with "fake literals"

When compiling Erlang source code, the literal area for the
module can only contain data types that have a literal
syntax.

However, it is possible to sneak in other data types
(such as references) in the literal pool by compiling from
abstract or assembly code. Those "fake literals" would work
fine, but would crash the runtime system when the module containing
the literals was purged.

Although fake literals are not officially supported, the
runtime should not crash when attempting to use them.
Therefore, fix the garbage collection of literals and releasing
of literal areas.

https://bugs.erlang.org/browse/ERL-508
---
 erts/emulator/test/code_SUITE.erl | 60 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 59 insertions(+), 1 deletion(-)

(limited to 'erts/emulator/test/code_SUITE.erl')

diff --git a/erts/emulator/test/code_SUITE.erl b/erts/emulator/test/code_SUITE.erl
index 77321aa50f..dca600bc7b 100644
--- a/erts/emulator/test/code_SUITE.erl
+++ b/erts/emulator/test/code_SUITE.erl
@@ -25,6 +25,7 @@
          multi_proc_purge/1, t_check_old_code/1,
          external_fun/1,get_chunk/1,module_md5/1,
          constant_pools/1,constant_refc_binaries/1,
+         fake_literals/1,
          false_dependency/1,coverage/1,fun_confusion/1,
          t_copy_literals/1, t_copy_literals_frags/1]).
 
@@ -38,7 +39,8 @@ all() ->
      call_purged_fun_code_reload, call_purged_fun_code_there,
      multi_proc_purge, t_check_old_code, external_fun, get_chunk,
      module_md5,
-     constant_pools, constant_refc_binaries, false_dependency,
+     constant_pools, constant_refc_binaries, fake_literals,
+     false_dependency,
      coverage, fun_confusion, t_copy_literals, t_copy_literals_frags].
 
 init_per_suite(Config) ->
@@ -554,6 +556,62 @@ wait_for_memory_deallocations() ->
             wait_for_memory_deallocations()
     end.
 
+fake_literals(_Config) ->
+    Mod = fake__literals__module,
+    try
+        do_fake_literals(Mod)
+    after
+        _ = code:purge(Mod),
+        _ = code:delete(Mod),
+        _ = code:purge(Mod),
+        _ = code:delete(Mod)
+    end,
+    ok.
+
+do_fake_literals(Mod) ->
+    Tid = ets:new(test, []),
+    ExtTerms = get_external_terms(),
+    Term0 = {self(),make_ref(),Tid,fun() -> ok end,ExtTerms},
+    Terms = [begin
+                 make_literal_module(Mod, Term0),
+                 Mod:term()
+             end || _ <- lists:seq(1, 10)],
+    verify_lit_terms(Terms, Term0),
+    true = ets:delete(Tid),
+    ok.
+
+make_literal_module(Mod, Term) ->
+    Exp = [{term,0}],
+    Attr = [],
+    Fs = [{function,term,0,2,
+           [{label,1},
+            {line,[]},
+            {func_info,{atom,Mod},{atom,term},0},
+            {label,2},
+            {move,{literal,Term},{x,0}},
+            return]}],
+    Asm = {Mod,Exp,Attr,Fs,2},
+    {ok,Mod,Beam} = compile:forms(Asm, [from_asm,binary,report]),
+    code:load_binary(Mod, atom_to_list(Mod), Beam).
+
+verify_lit_terms([H|T], Term) ->
+    case H =:= Term of
+        true ->
+            verify_lit_terms(T, Term);
+        false ->
+            error({bad_term,H})
+    end;
+verify_lit_terms([], _) ->
+    ok.
+
+get_external_terms() ->
+    {ok,Node} =	test_server:start_node(?FUNCTION_NAME, slave, []),
+    Ref = rpc:call(Node, erlang, make_ref, []),
+    Ports = rpc:call(Node, erlang, ports, []),
+    Pid = rpc:call(Node, erlang, self, []),
+    _ = test_server:stop_node(Node),
+    {Ref,hd(Ports),Pid}.
+
 %% OTP-7559: c_p->cp could contain garbage and create a false dependency
 %% to a module in a process. (Thanks to Richard Carlsson.)
 false_dependency(Config) when is_list(Config) ->
-- 
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