add support for more magic breakpoints fix #55

bochs/.bochsrc

@@ -1271,13 +1271,22 @@ speaker: enabled=1, mode=sound, volume=15
 #=======================================================================
 # MAGIC_BREAK:
 # This enables the "magic breakpoint" feature when using the debugger.
-# The useless cpu instruction XCHG BX, BX causes Bochs to enter the
+# The useless cpu instructions XCHG %REGW, %REGW causes Bochs to enter the
 # debugger mode. This might be useful for software development.
 #
-# Example:
+# You can specify multiple at once:
+#
+# %cx %dx %bx %sp %bp %si %di
+#
+# Example for breaking on "XCHGW %DI, %DI" or "CHGW %SP, %SP" execution
+#   magic_break: enabled=1 %di %sp
+#
+# If nothing is specified, the default will be used: XCHGW %BX, %BX 
 #   magic_break: enabled=1
+#
+# Note: Windows XP ntldr can cause problems with XCHGW %BX, %BX
 #=======================================================================
-#magic_break: enabled=1
+# magic_break: enabled=1
 
 #=======================================================================
 # DEBUG_SYMBOLS:

bochs/bochs.h

@@ -271,7 +271,7 @@ void print_statistics_tree(bx_param_c *node, int level = 0);
 // defines for GDB stub
 void bx_gdbstub_init(void);
 void bx_gdbstub_break(void);
-int bx_gdbstub_check(unsigned int eip);
+int bx_gdbstub_check(Bit64u eip);
 #define GDBSTUB_STOP_NO_REASON   (0xac0)
 
 #if BX_SUPPORT_SMP
@@ -287,7 +287,7 @@ typedef struct {
   bool exceptions;
   bool print_timestamps;
 #if BX_DEBUGGER
-  bool magic_break_enabled;
+  Bit8u magic_break;
 #endif
 #if BX_GDBSTUB
   bool gdbstub_enabled;

bochs/bx_debug/dbg_main.cc

@@ -2283,6 +2283,55 @@ void bx_dbg_lyt(void)
   bx_nest_infile(layoutpath);
 }
 
+void bx_dbg_set_magic_bp_mask(Bit8u mask)
+{
+  bx_dbg.magic_break = mask;
+  dbg_printf("new magic breakpoint mask created: 0x%x\n", mask);
+}
+
+Bit8u bx_dbg_get_magic_bp_mask_from_str(const char *str)
+{
+  Bit8u new_mask = 0;
+
+  if (NULL == str)
+  {
+    return 0;
+  }
+
+  if (strstr(str, "%cx") != NULL)
+    {
+      new_mask |= 1 << 0;
+    }
+  if (strstr(str, "%dx") != NULL)
+    {
+      new_mask |= 1 << 1;
+    }
+  if (strstr(str, "%sp") != NULL)
+    {
+      new_mask |= 1 << 3;
+    }
+  if (strstr(str, "%bp") != NULL)
+    {
+      new_mask |= 1 << 4;
+    }
+  if (strstr(str, "%si") != NULL)
+    {
+      new_mask |= 1 << 5;
+    }
+  if (strstr(str, "%di") != NULL)
+    {
+      new_mask |= 1 << 6;
+    }
+
+  // %bx if not specified for backward compatibility
+  if (0 == new_mask || strstr(str, "%bx") != NULL)
+    {
+      new_mask |= 1 << 2; 
+    }
+
+  return new_mask;
+}
+
 void bx_dbg_print_guard_results(void)
 {
   unsigned cpu, i;
@@ -3141,6 +3190,11 @@ void bx_dbg_print_descriptor(Bit32u lo, Bit32u hi)
       default:
         // task, int, trap, or call gate.
         dbg_printf("target=0x%04x:0x%08x, DPL=%d", segment, offset, dpl);
+
+        const char *Sym = bx_dbg_disasm_symbolic_address(offset, 0);
+        if (Sym)
+          dbg_printf(" (%s)", Sym);
+
         break;
       }
     }
@@ -3786,7 +3840,7 @@ void bx_dbg_print_help(void)
   dbg_printf("h|help command - show short command description\n");
   dbg_printf("-*- Debugger control -*-\n");
   dbg_printf("    help, q|quit|exit, set, instrument, show, trace, trace-reg,\n");
-  dbg_printf("    trace-mem, u|disasm, ldsym, slist, addlyt, remlyt, lyt, source\n");
+  dbg_printf("    trace-mem, u|disasm, ldsym, setmagicbps, slist, addlyt, remlyt, lyt, source\n");
   dbg_printf("-*- Execution control -*-\n");
   dbg_printf("    c|cont|continue, s|step, p|n|next, modebp, vmexitbp\n");
   dbg_printf("-*- Breakpoint management -*-\n");

bochs/bx_debug/debug.h

@@ -76,6 +76,8 @@ bool bx_dbg_register_debug_info(const char *devname, void *dev);
 void bx_dbg_addlyt(const char* new_layoutpath);
 void bx_dbg_remlyt(void);
 void bx_dbg_lyt(void);
+void bx_dbg_set_magic_bp_mask(Bit8u mask);
+Bit8u bx_dbg_get_magic_bp_mask_from_str(const char *str);
 bool bx_dbg_read_linear(unsigned which_cpu, bx_address laddr, unsigned len, Bit8u *buf);
 bool bx_dbg_write_linear(unsigned which_cpu, bx_address laddr, unsigned len, Bit8u *buf);
 Bit16u bx_dbg_get_selector_value(unsigned int seg_no);

bochs/bx_debug/lexer.l

@@ -146,6 +146,7 @@ read            { bxlval.sval = strdup(bxtext); return(BX_TOKEN_READ); }
 w|write         { bxlval.sval = strdup(bxtext); return(BX_TOKEN_WRITE); }
 show            { bxlval.sval = strdup(bxtext); return(BX_TOKEN_SHOW); }
 ldsym           { bxlval.sval = strdup(bxtext); return(BX_TOKEN_LOAD_SYMBOLS); }
+setmagicbps     { bxlval.sval = strdup(bxtext); return(BX_TOKEN_SET_MAGIC_BREAK_POINTS); }
 symbols         { bxlval.sval = strdup(bxtext); return(BX_TOKEN_SYMBOLS); }
 slist           { bxlval.sval = strdup(bxtext); return(BX_TOKEN_LIST_SYMBOLS); }
 global          { bxlval.sval = strdup(bxtext); return(BX_TOKEN_GLOBAL); }

bochs/bx_debug/parser.y

@@ -113,6 +113,7 @@ Bit64u eval_value;
 %token <sval> BX_TOKEN_WRITE
 %token <sval> BX_TOKEN_SHOW
 %token <sval> BX_TOKEN_LOAD_SYMBOLS
+%token <sval> BX_TOKEN_SET_MAGIC_BREAK_POINTS
 %token <sval> BX_TOKEN_SYMBOLS
 %token <sval> BX_TOKEN_LIST_SYMBOLS
 %token <sval> BX_TOKEN_GLOBAL
@@ -200,6 +201,7 @@ command:
     | vmexitbp_command
     | print_stack_command
     | backtrace_command
+    | set_magic_break_points_command
     | watch_point_command
     | page_command
     | tlb_command
@@ -459,6 +461,19 @@ symbol_command:
       }
     ;
 
+set_magic_break_points_command:
+      BX_TOKEN_SET_MAGIC_BREAK_POINTS '\n'
+      {
+        bx_dbg_set_magic_bp_mask(0);
+        free($1);
+      }
+    | BX_TOKEN_SET_MAGIC_BREAK_POINTS BX_TOKEN_STRING '\n'
+      {
+        bx_dbg_set_magic_bp_mask(bx_dbg_get_magic_bp_mask_from_str($2));
+        free($1); free($2);
+      }
+    ;
+
 where_command:
       BX_TOKEN_WHERE '\n'
       {
@@ -1158,6 +1173,11 @@ help_command:
          dbg_printf("ldsym [global] <filename> [offset] - load symbols from file\n");
          free($1);free($2);
        }
+     | BX_TOKEN_HELP BX_TOKEN_SET_MAGIC_BREAK_POINTS '\n'
+       {
+         dbg_printf("setmagicbps \"%%cx %%dx %%bx %%sp %%bp %%si %%di\" - changes magic breakpoints. You can specify multiple at once. Using the setmagicbps command without any arguments will disable all of them\n");
+         free($1);free($2);
+       }
      | BX_TOKEN_HELP BX_TOKEN_LIST_SYMBOLS '\n'
        {
          dbg_printf("slist [string] - list symbols whose preffix is string (same as 'info symbols')\n");

bochs/config.cc

@@ -45,6 +45,11 @@
 #undef getenv
 #endif
 
+#ifdef WIN32
+#define DIRECTORY_SEPARATOR "\\"
+#else
+#define DIRECTORY_SEPARATOR "/"
+#endif
 
 const char **config_interface_list;
 const char **display_library_list;
@@ -852,7 +857,7 @@ void bx_init_options()
       "Pathname of ROM image to load",
       "", BX_PATHNAME_LEN);
   path->set_format("Name of ROM BIOS image: %s");
-  sprintf(name, "%s/BIOS-bochs-latest", (char *)get_builtin_variable("BXSHARE"));
+  sprintf(name, "%s" DIRECTORY_SEPARATOR "BIOS-bochs-latest", (char *)get_builtin_variable("BXSHARE"));
   path->set_initial_val(name);
   bx_param_num_c *romaddr = new bx_param_num_c(rom,
       "address",
@@ -876,7 +881,7 @@ void bx_init_options()
       "Pathname of VGA ROM image to load",
       "", BX_PATHNAME_LEN);
   path->set_format("Name of VGA BIOS image: %s");
-  sprintf(name, "%s/VGABIOS-lgpl-latest", get_builtin_variable("BXSHARE"));
+  sprintf(name, "%s" DIRECTORY_SEPARATOR "VGABIOS-lgpl-latest", get_builtin_variable("BXSHARE"));
   path->set_initial_val(name);
   vgarom->set_options(vgarom->SERIES_ASK);
 
@@ -3142,6 +3147,7 @@ static int parse_line_formatted(const char *context, int num_params, char *param
 #endif
   } else if (!strcmp(params[0], "magic_break")) {
 #if BX_DEBUGGER
+    bx_dbg.magic_break = 0;
     if (num_params != 2) {
       PARSE_ERR(("%s: magic_break directive: wrong # args.", context));
     }
@@ -3150,14 +3156,15 @@ static int parse_line_formatted(const char *context, int num_params, char *param
     }
     if (params[1][8] == '0') {
       BX_INFO(("Ignoring magic break points"));
-      bx_dbg.magic_break_enabled = 0;
     }
-    else if (params[1][8] == '1') {
-      BX_INFO(("Stopping on magic break points"));
-      bx_dbg.magic_break_enabled = 1;
+    else if (params[1][8] == '1'){
+      {
+        bx_dbg_set_magic_bp_mask(bx_dbg_get_magic_bp_mask_from_str(params[1]));
+        BX_INFO(("Stopping on magic break points, mask: 0x%x", bx_dbg.magic_break));
+      }
     }
     else {
-      PARSE_ERR(("%s: magic_break directive malformed.", context));
+      PARSE_ERR(("%s: magic_break directive malformed", context));
     }
 #else
     PARSE_WARN(("%s: Bochs is not compiled with internal debugger support", context));
@@ -3401,7 +3408,7 @@ int bx_write_debugger_options(FILE *fp)
 {
 #if BX_DEBUGGER
   fprintf(fp, "debugger_log: %s\n", SIM->get_param_string(BXPN_DEBUGGER_LOG_FILENAME)->getptr());
-  fprintf(fp, "magic_break: enabled=%d\n", bx_dbg.magic_break_enabled);
+  fprintf(fp, "magic_break: enabled=1 0x%x\n", bx_dbg.magic_break);
   // TODO: debug symbols
 #endif
 #if BX_GDBSTUB

bochs/cpu/cpu.cc

@@ -775,7 +775,12 @@ bool BX_CPU_C::dbg_instruction_epilog(void)
 
 #if BX_GDBSTUB
   if (bx_dbg.gdbstub_enabled) {
-    unsigned reason = bx_gdbstub_check(EIP);
+    unsigned reason =
+#if BX_SUPPORT_X86_64 == 0
+        bx_gdbstub_check(EIP);
+#else
+        bx_gdbstub_check(RIP);
+#endif
     if (reason != GDBSTUB_STOP_NO_REASON) return(1);
   }
 #endif

bochs/cpu/data_xfer16.cc

@@ -219,8 +219,16 @@ void BX_CPP_AttrRegparmN(1) BX_CPU_C::XCHG_EwGwR(bxInstruction_c *i)
   Bit16u op1_16, op2_16;
 
 #if BX_DEBUGGER
-  // Note for mortals: the instruction to trigger this is "xchgw %bx,%bx"
-  if (bx_dbg.magic_break_enabled && (i->src() == 3) && (i->dst() == 3))
+  /* Note for mortals: the instruction to trigger this is "xchgw %regw,%regw"
+    66:87C9  | xchg cx,cx  | 1000011111 001 001 -> 1
+    66:87D2  | xchg dx,dx  | 1000011111 010 010 -> 2
+    66:87DB  | xchg bx,bx  | 1000011111 011 011 -> 3
+    66:87E4  | xchg sp,sp  | 1000011111 100 100 -> 4
+    66:87ED  | xchg bp,bp  | 1000011111 101 101 -> 5
+    66:87F6  | xchg si,si  | 1000011111 110 110 -> 6
+    66:87FF  | xchg di,di  | 1000011111 111 111 -> 7
+  */
+  if (bx_dbg.magic_break && i->src() == i->dst() && (bx_dbg.magic_break & (1 << (i->src() - 1))))
   {
     BX_CPU_THIS_PTR magic_break = 1;
     BX_NEXT_INSTR(i);