- add triple fault recovery code

2002-03-12 09:15:12 +00:00 · 2002-03-12 09:15:12 +00:00 · 141cfd2b2f
parent 502a48057b
commit 141cfd2b2f
1 changed files with 139 additions and 0 deletions
--- a/bochs/patches/patch.triple-fault-recover
+++ b/bochs/patches/patch.triple-fault-recover
@ -0,0 +1,139 @@
+----------------------------------------------------------------------
+Patch name: patch.triple-fault-recover
+Author: Bryce Denney
+Date: Tue Mar 12 01:10:48 EST 2002
+
+Detailed description:
+See SF bug [ #526484 ] simulator dumps core
+
+When a triple fault occurs, Bochs panics.  If you continue through the panic,
+it will generally produce another exception and panic again at an even deeper
+stack level.  To recover from this potentially infinite recursion, I set
+a boolean variable called special_unwind_stack to true.  This variable causes
+the interrupt() and exception() functions to return immediately instead of
+creating more exception conditions, and allows the user to reenter the debugger
+after the triple fault.  Note that special_unwind_stack causes bochs to NOT
+emulate the hardware behavior correctly.  The correct behavior would be to
+reboot.  (Rebooting, if it is ever implemented, will need some kind of
+unwinding too.)
+
+Patch was created with:
+  cvs diff -u
+Apply patch to what version:
+  current cvs
+Instructions:
+  To patch, go to main bochs directory.
+  Type "patch -p0 < THIS_PATCH_FILE".
+----------------------------------------------------------------------
+? debug/Makefile
+? debug/.debug.h.swp
+? cpu/Makefile
+Index: debug/dbg_main.cc
+===================================================================
+RCS file: /cvsroot/bochs/bochs/debug/dbg_main.cc,v
+retrieving revision 1.37
+diff -u -r1.37 dbg_main.cc
+--- debug/dbg_main.cc	15 Feb 2002 22:58:06 -0000	1.37
+++ debug/dbg_main.cc	12 Mar 2002 09:11:00 -0000
+@@ -1520,6 +1520,7 @@
+ 
+ #if BX_NUM_SIMULATORS >= 2
+   bx_guard.interrupt_requested = 0;
+  bx_guard.special_unwind_stack = 0;
+   while (1) {
+     if ( !bx_dbg_cosimulateN(bx_debugger.icount_quantum) )
+       break;
+@@ -1533,6 +1534,7 @@
+ 
+ 
+   bx_guard.interrupt_requested = 0;
+  bx_guard.special_unwind_stack = 0;
+ 	int stop = 0;
+ 	int which = -1;
+ 	while (!stop) {
+@@ -1608,6 +1610,7 @@
+ 
+ #if BX_NUM_SIMULATORS >= 2
+   bx_guard.interrupt_requested = 0;
+  bx_guard.special_unwind_stack = 0;
+   bx_dbg_cosimulateN(count);
+ #else
+   // single CPU
+Index: debug/debug.h
+===================================================================
+RCS file: /cvsroot/bochs/bochs/debug/debug.h,v
+retrieving revision 1.10
+diff -u -r1.10 debug.h
+--- debug/debug.h	28 Nov 2001 18:37:12 -0000	1.10
+++ debug/debug.h	12 Mar 2002 09:11:00 -0000
+@@ -257,6 +257,18 @@
+   // user typed Ctrl-C, requesting simulator stop at next convient spot
+   volatile Boolean interrupt_requested;
+ 
+  // when a triple fault occurs, Bochs panics.  If you continue through
+  // the panic, it will generally produce another exception and panic
+  // again at an even deeper stack level.  To recover from this potentially
+  // infinite recursion, I set special_unwind_stack to true.  This causes
+  // the interrupt() and exception() functions to return immediately instead
+  // of creating more exception conditions, and allows the user to reenter the
+  // debugger after the triple fault.  Note that special_unwind_stack causes
+  // bochs to NOT emulate the hardware behavior correctly.  The correct
+  // behavior would be to reboot.  (Rebooting, if it is ever implemented,
+  // will need some kind of unwinding too.)
+  Boolean special_unwind_stack;
+
+   // booleans to control whether simulator should report events
+   // to debug controller
+   struct {
+Index: cpu/exception.cc
+===================================================================
+RCS file: /cvsroot/bochs/bochs/cpu/exception.cc,v
+retrieving revision 1.9
+diff -u -r1.9 exception.cc
+--- cpu/exception.cc	3 Oct 2001 13:10:37 -0000	1.9
+++ cpu/exception.cc	12 Mar 2002 09:11:01 -0000
+@@ -63,6 +63,10 @@
+ #endif
+ #endif
+ 
+  if (bx_guard.special_unwind_stack) {
+    BX_INFO (("interrupt() returning early because special_unwind_stack is set"));
+    return;
+  }
+ //BX_DEBUG(( "::interrupt(%u)", vector ));
+ 
+   BX_INSTR_INTERRUPT(vector);
+@@ -572,6 +576,11 @@
+   Bit8u    exception_type;
+   unsigned prev_errno;
+ 
+  if (bx_guard.special_unwind_stack) {
+    BX_INFO (("exception() returning early because special_unwind_stack is set"));
+    return;
+  }
+
+ //BX_DEBUG(( "::exception(%u)", vector ));
+ 
+   BX_INSTR_EXCEPTION(vector);
+@@ -593,6 +602,9 @@
+   BX_CPU_THIS_PTR errorno++;
+   if (BX_CPU_THIS_PTR errorno >= 3) {
+     BX_PANIC(("exception(): 3rd exception with no resolution"));
+    BX_ERROR(("WARNING: Any simulation after this point is completely bogus."));
+    bx_guard.special_unwind_stack = true;
+    return;
+     }
+ 
+   /* careful not to get here with curr_exception[1]==DOUBLE_FAULT */
+@@ -600,7 +612,10 @@
+ 
+   /* if 1st was a double fault (software INT?), then shutdown */
+   if ( (BX_CPU_THIS_PTR errorno==2) && (BX_CPU_THIS_PTR curr_exception[0]==BX_ET_DOUBLE_FAULT) ) {
+-    BX_PANIC(("exception(): tripple fault encountered"));
+    BX_PANIC(("exception(): triple fault encountered"));
+    BX_ERROR(("WARNING: Any simulation after this point is completely bogus."));
+    bx_guard.special_unwind_stack = true;
+    return;
+     }
+ 
+   /* ??? this is not totally correct, should be done depending on