From 7469bcb69af0f7f1961cc7c1d995e87452c4a3d6 Mon Sep 17 00:00:00 2001
From: Stanislav Shwartsman <stlintel@gmail.com>
Date: Sun, 5 Nov 2023 07:08:36 +0200
Subject: [PATCH] =?UTF-8?q?measure=20host=20stack=20depth=20during=20simul?=
 =?UTF-8?q?ation=20to=20avoid=20excessive=20chainin=E2=80=A6=20(#119)?=
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…g depth

never allow beyong 64K stack
---
 bochs/cpu/cpu.cc | 20 ++++++++++++++++++--
 bochs/cpu/cpu.h  |  4 ++++
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/bochs/cpu/cpu.cc b/bochs/cpu/cpu.cc
index 44a62b9ba..c5214e3d8 100644
--- a/bochs/cpu/cpu.cc
+++ b/bochs/cpu/cpu.cc
@@ -51,6 +51,12 @@ jmp_buf BX_CPU_C::jmp_buf_env;
 
 void BX_CPU_C::cpu_loop(void)
 {
+#if BX_SUPPORT_HANDLERS_CHAINING_SPEEDUPS
+  volatile Bit8u stack_anchor = 0;
+
+  BX_CPU_THIS_PTR cpuloop_stack_anchor = &stack_anchor;
+#endif
+
 #if BX_DEBUGGER
   BX_CPU_THIS_PTR break_point = 0;
   BX_CPU_THIS_PTR magic_break = 0;
@@ -249,18 +255,28 @@ bxICacheEntry_c* BX_CPU_C::getICacheEntry(void)
 // The function is called after taken branch instructions and tries to link the branch to the next trace
 void BX_CPP_AttrRegparmN(1) BX_CPU_C::linkTrace(bxInstruction_c *i)
 {
+  volatile Bit8u stack_anchor = 0;
+
 #if BX_SUPPORT_SMP
   if (BX_SMP_PROCESSORS > 1)
     return;
 #endif
 
-#define BX_HANDLERS_CHAINING_MAX_DEPTH 1000
+#define BX_HANDLERS_CHAINING_MAX_LINK_DEPTH 1000
 
   // do not allow extreme trace link depth / avoid host stack overflow
   // (could happen with badly compiled instruction handlers)
   static Bit32u linkDepth = 0;
 
-  if (BX_CPU_THIS_PTR async_event || ++linkDepth > BX_HANDLERS_CHAINING_MAX_DEPTH) {
+  if (BX_CPU_THIS_PTR async_event || ++linkDepth > BX_HANDLERS_CHAINING_MAX_LINK_DEPTH) {
+    linkDepth = 0;
+    return;
+  }
+
+#define BX_HANDLERS_CHAINING_MAX_STACK_DEPTH 0x10000
+
+  size_t stack_depth = BX_CPU_THIS_PTR cpuloop_stack_anchor - &stack_anchor;
+  if (stack_depth > BX_HANDLERS_CHAINING_MAX_STACK_DEPTH) {
     linkDepth = 0;
     return;
   }
diff --git a/bochs/cpu/cpu.h b/bochs/cpu/cpu.h
index 2617d5b88..8bd1ae19b 100644
--- a/bochs/cpu/cpu.h
+++ b/bochs/cpu/cpu.h
@@ -1139,6 +1139,10 @@ public: // for now...
   static jmp_buf jmp_buf_env;
   unsigned last_exception_type;
 
+#if BX_SUPPORT_HANDLERS_CHAINING_SPEEDUPS
+  const volatile Bit8u *cpuloop_stack_anchor = NULL;
+#endif
+
   // Boundaries of current code page, based on EIP
   bx_address eipPageBias;
   Bit32u     eipPageWindowSize;