From 0a144d1fc4bebefcc74b0cb63fe76809bc041789 Mon Sep 17 00:00:00 2001
From: Rickard Green <rickard@erlang.org>
Date: Fri, 17 Feb 2017 15:26:01 +0100
Subject: Ensure prim_eval:'receive' wont clobber def_arg_reg[0]

def_arg_reg[0] is used for storage of timeout instruction
when a 'receive after' is executed. When a process was
scheduled out inside prim_eval:'receive'/0 due to a function
call, def_arg_reg[0] was overwritten due to storage of live
registers.

prim_eval:'receive'/2 now calls arg_reg_alloc/0 which
bumps all reductions and then calls arg_reg_alloc/7
which will cause an allocation of a new arg_reg array
since def_arg_reg only can hold 6 values. This ensures
that the timeout instruction in def_arg_reg[0] used
for the timeout wont be overwritten.
---
 erts/preloaded/ebin/prim_eval.beam | Bin 1300 -> 1448 bytes
 erts/preloaded/src/prim_eval.S     |  41 ++++++++++++++++++++++++++++++-------
 2 files changed, 34 insertions(+), 7 deletions(-)

(limited to 'erts/preloaded')

diff --git a/erts/preloaded/ebin/prim_eval.beam b/erts/preloaded/ebin/prim_eval.beam
index a50a628a27..49fd62490e 100644
Binary files a/erts/preloaded/ebin/prim_eval.beam and b/erts/preloaded/ebin/prim_eval.beam differ
diff --git a/erts/preloaded/src/prim_eval.S b/erts/preloaded/src/prim_eval.S
index e7f09a870c..c6623f8e03 100644
--- a/erts/preloaded/src/prim_eval.S
+++ b/erts/preloaded/src/prim_eval.S
@@ -26,7 +26,7 @@
 
 {attributes, []}.
 
-{labels, 10}.
+{labels, 14}.
 
 
 {function, 'receive', 2, 2}.
@@ -36,6 +36,9 @@
     {allocate,2,2}.
     {move,{x,1},{y,0}}.
     {move,{x,0},{y,1}}.
+    %% Call arg_reg_alloc() in order to ensure
+    %% that def_arg_reg[0] isn't clobbered
+    {call,0,{f,7}}.
   {label,3}.
     {loop_rec,{f,5},{x,0}}.
     {move,{y,1},{x,1}}.
@@ -53,19 +56,43 @@
     {deallocate,2}.
     return.
 
-
-{function, module_info, 0, 8}.
+{function, arg_reg_alloc, 0, 7}.
   {label,6}.
-    {func_info,{atom,prim_eval},{atom,module_info},0}.
+    {func_info,{atom,prim_eval},{atom,arg_reg_alloc},0}.
   {label,7}.
+    {allocate,0,0}.
+    {move,{integer,134217727},{x,0}}.
+    {call_ext,1,{extfunc,erlang,bump_reductions,1}}.
+    {move,{atom,true},{x,3}}.
+    {move,{atom,true},{x,4}}.
+    {move,{atom,true},{x,2}}.
+    {move,{atom,true},{x,5}}.
+    {move,{atom,true},{x,1}}.
+    {move,{atom,true},{x,6}}.
+    {move,{atom,true},{x,0}}.
+    {call_last,7,{f,9},0}.
+
+
+{function, arg_reg_alloc, 7, 9}.
+  {label,8}.
+    {func_info,{atom,prim_eval},{atom,arg_reg_alloc},7}.
+  {label,9}.
+    {move,{atom,ok},{x,0}}.
+    return.
+
+
+{function, module_info, 0, 11}.
+  {label,10}.
+    {func_info,{atom,prim_eval},{atom,module_info},0}.
+  {label,11}.
     {move,{atom,prim_eval},{x,0}}.
     {call_ext_only,1,{extfunc,erlang,get_module_info,1}}.
 
 
-{function, module_info, 1, 10}.
-  {label,8}.
+{function, module_info, 1, 13}.
+  {label,12}.
     {func_info,{atom,prim_eval},{atom,module_info},1}.
-  {label,9}.
+  {label,13}.
     {move,{x,0},{x,1}}.
     {move,{atom,prim_eval},{x,0}}.
     {call_ext_only,2,{extfunc,erlang,get_module_info,2}}.
-- 
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