From 9579837a6d267cd289d92ca7607fe5e645a6703c Mon Sep 17 00:00:00 2001
From: Beuc <beuc@beuc.net>
Date: Thu, 5 Jul 2018 19:11:56 +0200
Subject: [PATCH] emterpreter: explicit error message on emterpreter stack
 overflow (#6754) (#6774)

---
 emscripten.py         |  2 ++
 src/preamble.js       |  6 ++++++
 tools/emterpretify.py | 10 ++++++----
 tools/js-optimizer.js |  4 +++-
 4 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/emscripten.py b/emscripten.py
index 0db04ff3d12f..4ca8dc65ac02 100755
--- a/emscripten.py
+++ b/emscripten.py
@@ -1224,6 +1224,8 @@ def create_basic_funcs(function_table_sigs):
     basic_funcs += ['abortOnCannotGrowMemory']
   if shared.Settings.STACK_OVERFLOW_CHECK:
     basic_funcs += ['abortStackOverflow']
+  if shared.Settings.EMTERPRETIFY:
+    basic_funcs += ['abortStackOverflowEmterpreter']
   if shared.Settings.SAFE_HEAP:
     if asm_safe_heap():
       basic_funcs += ['segfault', 'alignfault', 'ftfault']
diff --git a/src/preamble.js b/src/preamble.js
index 55b6ab5cf4e2..41acd4514c9c 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -938,6 +938,12 @@ function abortStackOverflow(allocSize) {
 }
 #endif
 
+#if EMTERPRETIFY
+function abortStackOverflowEmterpreter() {
+  abort("Emterpreter stack overflow! Decrease the recursion level or increase EMT_STACK_MAX in tools/emterpretify.py (current value " + EMT_STACK_MAX + ").");
+}
+#endif
+
 #if ABORTING_MALLOC
 function abortOnCannotGrowMemory() {
 #if WASM
diff --git a/tools/emterpretify.py b/tools/emterpretify.py
index b6225dc9567e..98d4e6a14947 100755
--- a/tools/emterpretify.py
+++ b/tools/emterpretify.py
@@ -479,8 +479,9 @@ def handle_async_post_call():
 
 CASES[ROPCODES['INTCALL']] = '''
     lz = HEAPU8[(HEAP32[pc + 4 >> 2] | 0) + 1 | 0] | 0; // FUNC inst, see definition above; we read params here
-    ly = 0;
-    assert(((EMTSTACKTOP + 8|0) <= (EMT_STACK_MAX|0))|0); // for return value
+    ly = 0;''' + ('''
+    if (((EMTSTACKTOP + 8|0) > (EMT_STACK_MAX|0))|0) // for return value
+      abortStackOverflowEmterpreter(); ''' if ASSERTIONS else '') + '''
     %s
      %s
       while ((ly|0) < (lz|0)) {
@@ -701,8 +702,9 @@ def process(code):
   '' if not ASYNC else 'HEAP32[EMTSTACKTOP>>2] = pc;\n',
   push_stacktop(zero),
   ROPCODES['FUNC'],
-  (''' EMTSTACKTOP = EMTSTACKTOP + (lx ''' + (' + 1 ' if ASYNC else '') + '''<< 3) | 0;
- assert(((EMTSTACKTOP|0) <= (EMT_STACK_MAX|0))|0);\n''' + (' if ((asyncState|0) != 2) {' if ASYNC else '')) if not zero else '',
+  (''' EMTSTACKTOP = EMTSTACKTOP + (lx ''' + (' + 1 ' if ASYNC else '') + '''<< 3) | 0;\n''' +
+    (''' if (((EMTSTACKTOP|0) > (EMT_STACK_MAX|0))|0) abortStackOverflowEmterpreter();\n''' if ASSERTIONS else '') +
+    (' if ((asyncState|0) != 2) {' if ASYNC else '')) if not zero else '',
   ' } else { pc = (HEAP32[sp - 4 >> 2] | 0) - 8 | 0; }' if ASYNC else '',
   main_loop,
 ))
diff --git a/tools/js-optimizer.js b/tools/js-optimizer.js
index b5ef85f702f5..a3ff77abaa0a 100644
--- a/tools/js-optimizer.js
+++ b/tools/js-optimizer.js
@@ -7574,7 +7574,9 @@ function emterpretify(ast) {
         func[3].push(srcToStat('sp = EMTSTACKTOP;'));
         var stackBytes = finalLocals*8;
         func[3].push(srcToStat('EMTSTACKTOP = EMTSTACKTOP + ' + stackBytes + ' | 0;'));
-        func[3].push(srcToStat('assert(((EMTSTACKTOP|0) <= (EMT_STACK_MAX|0))|0);'));
+        if (ASSERTIONS) {
+          func[3].push(srcToStat('if (((EMTSTACKTOP|0) > (EMT_STACK_MAX|0))|0) abortStackOverflowEmterpreter();'));
+        }
         asmData.vars['x'] = ASM_INT;
         func[3].push(srcToStat('while ((x | 0) < ' + stackBytes + ') { HEAP32[sp + x >> 2] = HEAP32[x >> 2] | 0; x = x + 4 | 0; }'));
       }