[PATCH] Remote GDB debugging stub (for i386)

[Lubomir Rintel <lkundrak@v3.sk>]

[-- Attachment #1: Type: text/plain, Size: 2040 bytes --]

Re-sending the GDB stub patch. The GDB protocol part, though being
largely rewritten, originates from GDB source tarball, which refers to
it as a Public Domain code.

Applies against today's CVS.

Is not much of use without debugging symbols, part 2 of patch [1]
preserves those. Neither is it of much use without being able to resolve
load addresses of modules, I will submit the GDB scripts shortly.

[1] http://lists.gnu.org/archive/html/grub-devel/2008-04/msg00080.html

Note that I found this hunk [2] lying around from 2006 when I wrote this
on NetBSD. I am not completely sure what does it do, but the changelog
from then suggests, that "grub_gdb_trapvec" from the gdb module was for
some reason resolved to 0 instead of its actual address. It might have
been dependent on the toolchain used, as I am not able to reproduce the
behavior on current Fedora 9.

[2] http://pastebin.com/f5c791966

2008-05-01:  Lubomir Rintel  <lkundrak@v3.sk>

        * conf/i386-pc.rmk: Add gdb module to the list of modules to be built.

        * term/i386/pc/serial.c (serial_hw_put): Let some useful serial
        driver functions be exported.
        (grub_serial_getkey): Likewise

        * kern/dl.c (grub_dl_resolve_symbols): Let the trapvec symbol be
        resolved correctly (instead of 0).

        * kern/i386/pc/startup.S: (prot_idt) Add region descriptor to hold
        protected mode IDT.
        (real_idt) IDT region dsecriptor that works in real mode
        (real_to_prot) Load protected mode idt IDT when returning to
        protected mode.

        * kern/i386/realmode.S: (prot_to_real) Save protected mode IDT and load
        real mode one before switching to real mode.

        * gdb/cstub.c: New file.
        * gdb/gdb.c:  New file.
        * gdb/i386/idt.c: New file.
        * gdb/i386/signal.c: New file.
        * gdb/i386/machdep.S: New file.
        * include/grub/gdb.h: New file.
        * include/grub/i386/gdb.h: New file.
        * include/grub/i386/pc/kernel.h: New file.

--
Lubomir Rintel (Was: Kundrak)

[-- Attachment #2: grub2-gdb-stub-v3.patch --]
[-- Type: text/x-patch, Size: 27666 bytes --]

2008-05-01:  Lubomir Rintel  <lkundrak@v3.sk>

        * conf/i386-pc.rmk: Add gdb module to the list of modules to be built.

        * term/i386/pc/serial.c (serial_hw_put): Let some useful serial
        driver functions be exported.
        (grub_serial_getkey): Likewise

        * kern/dl.c (grub_dl_resolve_symbols): Let the trapvec symbol be
        resolved correctly (instead of 0).

        * kern/i386/pc/startup.S: (prot_idt) Add region descriptor to hold
        protected mode IDT.
        (real_idt) IDT region dsecriptor that works in real mode
        (real_to_prot) Load protected mode idt IDT when returning to
        protected mode.

        * kern/i386/realmode.S: (prot_to_real) Save protected mode IDT and load
        real mode one before switching to real mode.

        * gdb/cstub.c: New file.
        * gdb/gdb.c:  New file.
        * gdb/i386/idt.c: New file.
        * gdb/i386/signal.c: New file.
        * gdb/i386/machdep.S: New file.
        * include/grub/gdb.h: New file.
        * include/grub/i386/gdb.h: New file.
        * include/grub/i386/pc/kernel.h: New file.

--- grub2/conf/i386-pc.rmk	2008-03-31 13:17:59.000000000 +0200
+++ grub2-gdb/conf/i386-pc.rmk	2008-05-01 12:11:48.000000000 +0200
@@ -155,7 +155,7 @@ pkglib_MODULES = biosdisk.mod _chain.mod
 	vbe.mod vbetest.mod vbeinfo.mod video.mod gfxterm.mod \
 	videotest.mod play.mod bitmap.mod tga.mod cpuid.mod serial.mod	\
 	ata.mod vga.mod memdisk.mod jpeg.mod png.mod pci.mod lspci.mod \
-	aout.mod _bsd.mod bsd.mod
+	aout.mod _bsd.mod bsd.mod gdb.mod
 
 # For biosdisk.mod.
 biosdisk_mod_SOURCES = disk/i386/pc/biosdisk.c
@@ -322,4 +322,11 @@ bsd_mod_SOURCES = loader/i386/bsd_normal
 bsd_mod_CFLAGS = $(COMMON_CFLAGS)
 bsd_mod_LDFLAGS = $(COMMON_LDFLAGS)
 
+# For gdb.mod
+gdb_mod_SOURCES = gdb/cstub.c gdb/gdb.c gdb/i386/idt.c \
+	gdb/i386/machdep.S gdb/i386/signal.c
+gdb_mod_CFLAGS = $(COMMON_CFLAGS)
+gdb_mod_LDFLAGS = $(COMMON_LDFLAGS)
+gdb_mod_ASFLAGS = $(COMMON_ASFLAGS)
+
 include $(srcdir)/conf/common.mk
--- grub2/gdb/cstub.c	1970-01-01 01:00:00.000000000 +0100
+++ grub2-gdb/gdb/cstub.c	2008-05-01 10:57:57.000000000 +0200
@@ -0,0 +1,362 @@
+/* cstub.c - machine independent portion of remote GDB stub */
+/*
+ *  Copyright (C) 2006  Lubomir Kundrak
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <grub/misc.h>
+#include <grub/cpu/gdb.h>
+#include <grub/gdb.h>
+
+static const char hexchars[] = "0123456789abcdef";
+int grub_gdb_regs[GRUB_MACHINE_NR_REGS];
+
+#define GRUB_GDB_COMBUF_SIZE 400	/* At least sizeof(grub_gdb_regs)*2 are needed for
+					   register packets.  */
+static char grub_gdb_inbuf[GRUB_GDB_COMBUF_SIZE];
+static char grub_gdb_outbuf[GRUB_GDB_COMBUF_SIZE];
+
+int (*grub_gdb_getchar) ();
+void (*grub_gdb_putchar) (int);
+
+static int
+hex (ch)
+     char ch;
+{
+  if ((ch >= 'a') && (ch <= 'f'))
+    return (ch - 'a' + 10);
+  if ((ch >= '0') && (ch <= '9'))
+    return (ch - '0');
+  if ((ch >= 'A') && (ch <= 'F'))
+    return (ch - 'A' + 10);
+  return (-1);
+}
+
+/* Scan for the sequence $<data>#<checksum>.  */
+static char *
+grub_gdb_getpacket (void)
+{
+  char *buffer = &grub_gdb_inbuf[0];
+  unsigned char checksum;
+  unsigned char xmitcsum;
+  int count;
+  char ch;
+
+  while (1)
+    {
+      /* Wait around for the start character, ignore all other
+         characters.  */
+      while ((ch = grub_gdb_getchar ()) != '$');
+
+    retry:
+      checksum = 0;
+      xmitcsum = -1;
+      count = 0;
+
+      /* Now read until a # or end of buffer is found.  */
+      while (count < GRUB_GDB_COMBUF_SIZE)
+	{
+	  ch = grub_gdb_getchar ();
+	  if (ch == '$')
+	    goto retry;
+	  if (ch == '#')
+	    break;
+	  checksum += ch;
+	  buffer[count] = ch;
+	  count = count + 1;
+	}
+      buffer[count] = 0;
+
+      if (ch == '#')
+	{
+	  ch = grub_gdb_getchar ();
+	  xmitcsum = hex (ch) << 4;
+	  ch = grub_gdb_getchar ();
+	  xmitcsum += hex (ch);
+
+	  if (checksum != xmitcsum)
+	    {
+	      grub_dprintf ("gdb",
+			    "bad checksum.  My count = 0x%x, sent=0x%x. buf=%s\n",
+			    checksum, xmitcsum, buffer);
+	      grub_gdb_putchar ('-');	/* Failed checksum.  */
+	    }
+	  else
+	    {
+	      grub_gdb_putchar ('+');	/* Successful transfer.  */
+
+	      /* If a sequence char is present, reply the sequence ID.  */
+	      if (buffer[2] == ':')
+		{
+		  grub_gdb_putchar (buffer[0]);
+		  grub_gdb_putchar (buffer[1]);
+
+		  return &buffer[3];
+		}
+	      return &buffer[0];
+	    }
+	}
+    }
+}
+
+/* Send the packet in buffer.  */
+static void
+grub_gdb_putpacket (char *buffer)
+{
+  unsigned char checksum;
+  int count;
+  char ch;
+
+  /* $<packet info>#<checksum>.  */
+  do
+    {
+      grub_gdb_putchar ('$');
+      checksum = 0;
+      count = 0;
+
+      while ((ch = buffer[count]))
+	{
+	  grub_gdb_putchar (ch);
+	  checksum += ch;
+	  count += 1;
+	}
+
+      grub_gdb_putchar ('#');
+      grub_gdb_putchar (hexchars[checksum >> 4]);
+      grub_gdb_putchar (hexchars[checksum % 16]);
+    }
+  while (grub_gdb_getchar () != '+');
+}
+
+/* Convert the memory pointed to by mem into hex, placing result in buf.
+   Return a pointer to the last char put in buf (NULL).  */
+static char *
+grub_gdb_mem2hex (char *mem, char *buf, int count)
+{
+  int i;
+  unsigned char ch;
+
+  for (i = 0; i < count; i++)
+    {
+      ch = *mem++;
+      *buf++ = hexchars[ch >> 4];
+      *buf++ = hexchars[ch % 16];
+    }
+  *buf = 0;
+  return (buf);
+}
+
+/* Convert the hex array pointed to by buf into binary to be placed in mem.
+   Return a pointer to the character after the last byte written.  */
+static char *
+grub_gdb_hex2mem (char *buf, char *mem, int count)
+{
+  int i;
+  unsigned char ch;
+
+  for (i = 0; i < count; i++)
+    {
+      ch = hex (*buf++) << 4;
+      ch = ch + hex (*buf++);
+      *mem++ = ch;
+    }
+  return (mem);
+}
+
+/* Convert hex characters to int and return the number of characters
+   processed.  */
+static int
+grub_gdb_hex2int (char **ptr, int *int_value)
+{
+  int num_chars = 0;
+  int hex_value;
+
+  *int_value = 0;
+
+  while (**ptr)
+    {
+      hex_value = hex (**ptr);
+      if (hex_value >= 0)
+	{
+	  *int_value = (*int_value << 4) | hex_value;
+	  num_chars++;
+	}
+      else
+	break;
+
+      (*ptr)++;
+    }
+
+  return (num_chars);
+}
+
+/* This function does all command procesing for interfacing to gdb.  */
+void
+grub_gdb_trap (int trap_no)
+{
+  int sig_no;
+  int stepping;
+  int addr;
+  int length;
+  char *ptr;
+  int newPC;
+
+  sig_no = grub_gdb_trap2sig (trap_no);
+
+  ptr = grub_gdb_outbuf;
+
+  /* Reply to host that an exception has occurred.  */
+
+  *ptr++ = 'T';	/* Notify gdb with signo, PC, FP and SP.  */
+
+  *ptr++ = hexchars[sig_no >> 4];
+  *ptr++ = hexchars[sig_no & 0xf];
+
+  /* Stack pointer.  */
+  *ptr++ = hexchars[SP];
+  *ptr++ = ':';
+  ptr = grub_gdb_mem2hex ((char *) &grub_gdb_regs[ESP], ptr, 4);
+  *ptr++ = ';';
+
+  /* Frame pointer.  */
+  *ptr++ = hexchars[FP];
+  *ptr++ = ':';
+  ptr = grub_gdb_mem2hex ((char *) &grub_gdb_regs[EBP], ptr, 4);
+  *ptr++ = ';';
+
+  /* Program counter.  */
+  *ptr++ = hexchars[PC];
+  *ptr++ = ':';
+  ptr = grub_gdb_mem2hex ((char *) &grub_gdb_regs[PC], ptr, 4);
+  *ptr++ = ';';
+
+  *ptr = '\0';
+
+  grub_gdb_putpacket (grub_gdb_outbuf);
+
+  stepping = 0;
+
+  while (1 == 1)
+    {
+      grub_gdb_outbuf[0] = 0;
+      ptr = grub_gdb_getpacket ();
+
+      switch (*ptr++)
+	{
+	case '?':
+	  grub_gdb_outbuf[0] = 'S';
+	  grub_gdb_outbuf[1] = hexchars[sig_no >> 4];
+	  grub_gdb_outbuf[2] = hexchars[sig_no % 16];
+	  grub_gdb_outbuf[3] = 0;
+	  break;
+
+	/* Return values of the CPU registers.  */
+	case 'g':
+	  grub_gdb_mem2hex ((char *) grub_gdb_regs, grub_gdb_outbuf,
+			    sizeof (grub_gdb_regs));
+	  break;
+
+	/* Set values of the CPU registers -- return OK.  */
+	case 'G':
+	  grub_gdb_hex2mem (ptr, (char *) grub_gdb_regs,
+			    sizeof (grub_gdb_regs));
+	  grub_strcpy (grub_gdb_outbuf, "OK");
+	  break;
+
+	/* Set the value of a single CPU register -- return OK.  */
+	case 'P':
+	  {
+	    int regno;
+
+	    if (grub_gdb_hex2int (&ptr, &regno) && *ptr++ == '=')
+	      if (regno >= 0 && regno < GRUB_MACHINE_NR_REGS)
+		{
+		  grub_gdb_hex2mem (ptr, (char *) &grub_gdb_regs[regno], 4);
+		  grub_strcpy (grub_gdb_outbuf, "OK");
+		  break;
+		}
+	    grub_strcpy (grub_gdb_outbuf, "E01");
+	    break;
+	  }
+
+	/* mAA..AA,LLLL: Read LLLL bytes at address AA..AA.  */
+	case 'm':
+	  /* Try to read %x,%x.  Set ptr = 0 if successful.  */
+	  if (grub_gdb_hex2int (&ptr, &addr))
+	    if (*(ptr++) == ',')
+	      if (grub_gdb_hex2int (&ptr, &length))
+		{
+		  ptr = 0;
+		  grub_gdb_mem2hex ((char *) addr, grub_gdb_outbuf, length);
+		}
+	  if (ptr)
+	    {
+	      grub_strcpy (grub_gdb_outbuf, "E01");
+	    }
+	  break;
+
+	/* MAA..AA,LLLL: Write LLLL bytes at address AA.AA -- return OK.  */
+	case 'M':
+	  /* Try to read %x,%x.  Set ptr = 0 if successful.  */
+	  if (grub_gdb_hex2int (&ptr, &addr))
+	    if (*(ptr++) == ',')
+	      if (grub_gdb_hex2int (&ptr, &length))
+		if (*(ptr++) == ':')
+		  {
+		    grub_gdb_hex2mem (ptr, (char *) addr, length);
+		    grub_strcpy (grub_gdb_outbuf, "OK");
+		    ptr = 0;
+		  }
+	  if (ptr)
+	    {
+	      grub_strcpy (grub_gdb_outbuf, "E02");
+	    }
+	  break;
+
+	/* sAA..AA: Step one instruction from AA..AA(optional).  */
+	case 's':
+	  stepping = 1;
+
+	/* cAA..AA: Continue at address AA..AA(optional).  */
+	case 'c':
+	  /* try to read optional parameter, pc unchanged if no parm */
+	  if (grub_gdb_hex2int (&ptr, &addr))
+	    grub_gdb_regs[PC] = addr;
+
+	  newPC = grub_gdb_regs[PC];
+
+	  /* Clear the trace bit.  */
+	  grub_gdb_regs[PS] &= 0xfffffeff;
+
+	  /* Set the trace bit if we're stepping.  */
+	  if (stepping)
+	    grub_gdb_regs[PS] |= 0x100;
+
+	  return;
+	  break;
+
+	/* Kill the program.  */
+	case 'k':
+	  /* Do nothing.  */
+	  return;
+	  break;
+	}
+
+      /* Reply to the request.  */
+      grub_gdb_putpacket (grub_gdb_outbuf);
+    }
+}
+
--- grub2/gdb/gdb.c	1970-01-01 01:00:00.000000000 +0100
+++ grub2-gdb/gdb/gdb.c	2008-05-01 10:57:57.000000000 +0200
@@ -0,0 +1,61 @@
+/* gdb.c - gdb remote stub module */
+/*
+ *  Copyright (C) 2003  Free Software Foundation, Inc.
+ *  Copyright (C) 2006  Lubomir Kundrak
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <grub/types.h>
+#include <grub/misc.h>
+#include <grub/mm.h>
+#include <grub/err.h>
+#include <grub/dl.h>
+#include <grub/normal.h>
+#include <grub/term.h>
+#include <grub/cpu/gdb.h>
+#include <grub/gdb.h>
+
+extern int grub_serial_getkey ();
+extern void serial_hw_put (int);
+
+static grub_err_t
+grub_cmd_break (struct grub_arg_list *state __attribute__ ((unused)),
+		int argc __attribute__ ((unused)),
+		char **args __attribute__ ((unused)))
+{
+  grub_printf ("Now connect the remote debugger, please.\n");
+  grub_gdb_breakpoint ();
+  return 0;
+}
+
+GRUB_MOD_INIT (gdb)
+{
+  (void) mod;			/* To stop warning.  */
+
+  grub_gdb_getchar = &grub_serial_getkey;
+  grub_gdb_putchar = &serial_hw_put;
+
+  grub_gdb_idtinit ();
+  grub_register_command ("break", grub_cmd_break, GRUB_COMMAND_FLAG_BOTH,
+			 "break", "Break into debugger", 0);
+}
+
+GRUB_MOD_FINI (gdb)
+{
+  grub_unregister_command ("break");
+  /* FIXME: restore old IDTR.  */
+}
+
--- grub2/gdb/i386/idt.c	1970-01-01 01:00:00.000000000 +0100
+++ grub2-gdb/gdb/i386/idt.c	2008-05-01 10:57:57.000000000 +0200
@@ -0,0 +1,61 @@
+/* idt.c - routines for constructing IDT fot the GDB stub */
+/*
+ *  Copyright (C) 2006  Lubomir Kundrak
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <grub/machine/memory.h>
+#include <grub/misc.h>
+#include <grub/cpu/gdb.h>
+#include <grub/gdb.h>
+
+struct gate grub_gdb_idt[GRUB_GDB_LAST_TRAP + 1];
+
+/* Sets up a gate descriptor in the IDT table.  */
+static void
+grub_idt_gate (struct gate *gate, void (*offset) (), int selector,
+               int type, int dpl)
+{
+  gate->offset_lo = (int) offset & 0xffff;
+  gate->selector = selector & 0xffff;
+  gate->xx = 0;
+  gate->type = type & 0x1f;
+  gate->dpl = dpl & 0x3;
+  gate->present = 1;
+  gate->offset_hi = ((int) offset >> 16) & 0xffff;
+}
+
+/* Set up interrupt and trap handler descriptors in IDT.  */
+void
+grub_gdb_idtinit ()
+{
+  int i;
+  struct region r;
+
+  for (i = 0; i <= GRUB_GDB_LAST_TRAP; i++)
+    {
+      grub_idt_gate (&grub_gdb_idt[i],
+		     grub_gdb_trapvec[i],
+		     GRUB_MEMORY_MACHINE_PROT_MODE_CSEG,
+                     GRUB_CPU_TRAP_GATE, 0);
+    }
+
+  r.base = (int) grub_gdb_idt;
+  r.limit = sizeof (grub_gdb_idt) - 1;
+
+  grub_idt_load (&r);
+}
+
--- grub2/gdb/i386/machdep.S	1970-01-01 01:00:00.000000000 +0100
+++ grub2-gdb/gdb/i386/machdep.S	2008-05-01 10:57:57.000000000 +0200
@@ -0,0 +1,193 @@
+/* machdep.S - machine dependent assembly routines for the GDB stub */
+/*
+ *  Copyright (C) 2006  Lubomir Kundrak
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#define ASM	1
+#include <grub/cpu/gdb.h>
+
+#define EC_PRESENT	1
+#define EC_ABSENT	0
+
+#define GRUB_GDB_STACKSIZE	40000
+
+/*
+ * The .data index for the address vector.
+ */
+
+#define	VECTOR		1
+
+.globl grub_gdb_trap
+.globl grub_gdb_regs
+
+.data
+.globl grub_gdb_stack
+.space GRUB_GDB_STACKSIZE
+grub_gdb_stack:
+
+/*
+ * Supplemental macros for register saving/restoration
+ * on exception handler entry/leave.
+ */
+
+.macro save32 reg ndx
+	movl \reg, grub_gdb_regs+(\ndx * 4)
+.endm
+
+.macro save16 reg ndx
+	mov $0, %eax
+	movw \reg, grub_gdb_regs+(\ndx * 4)
+	movw %ax, grub_gdb_regs+(\ndx * 4 + 2)
+	movl grub_gdb_regs+(EAX * 4), %eax
+.endm
+
+.macro load32 ndx reg
+	movl grub_gdb_regs+(\ndx * 4), \reg
+.endm
+
+.macro load16 ndx reg
+	movw grub_gdb_regs+(\ndx * 4), \reg
+.endm
+
+.macro save_context
+	save32 %eax EAX
+	save32 %ecx ECX
+	save32 %edx EDX
+	save32 %ebx EBX
+	save32 %ebp EBP
+	save32 %esi ESI
+	save32 %edi EDI
+
+	popl %ebx
+	save32 %ebx EIP
+	popl %ebx
+	save32 %ebx CS
+	popl %ebx
+	save32 %ebx EFLAGS
+
+	save32 %esp ESP
+
+	save16 %ds DS
+	save16 %es ES
+	save16 %fs FS
+	save16 %gs GS
+	save16 %ss SS
+.endm
+
+.macro load_context
+	load16 SS %ss
+	load32 ESP %esp
+
+	load32 EBP %ebp
+	load32 ESI %esi
+	load32 EDI %edi
+
+	load16 DS %ds
+	load16 ES %es
+	load16 FS %fs
+	load16 GS %gs
+
+	load32 EFLAGS %eax
+	pushl %eax
+	load32 CS %eax
+	pushl %eax
+	load32 EIP %eax
+	pushl %eax
+
+	load32 EBX %ebx
+	load32 EDX %edx
+	load32 ECX %ecx
+	load32 EAX %eax
+.endm
+
+/*
+ * This macro creates handlers for a given range of exception numbers
+ * and adds their addresses to the grub_gdb_trapvec array.
+ */
+
+.macro ent ec beg end=0
+
+	/*
+	 * Wrapper body itself.
+	 */
+
+	.text
+1:	
+	.if \ec
+		add $4,%esp
+	.endif
+
+	save_context
+	mov	$grub_gdb_stack, %esp
+	mov	$\beg, %eax	/* trap number */
+	call	grub_gdb_trap
+	load_context
+	iret
+
+	/*
+	 * Address entry in trapvec array.
+	 */
+
+	.data VECTOR
+	.long 1b
+
+	/*
+	 * Next... (recursion).
+	 */
+
+	.if \end-\beg > 0
+		ent \ec "(\beg+1)" \end
+	.endif
+.endm
+
+/*
+ * Here does the actual construction of the address array and handlers
+ * take place.
+ */
+
+.data VECTOR
+.globl grub_gdb_trapvec
+grub_gdb_trapvec:
+	ent EC_ABSENT	0 7
+	ent EC_PRESENT	8
+	ent EC_ABSENT	9
+	ent EC_PRESENT	10 14
+	/*
+	 * You may have to split this further or as(1)
+	 * will complain about nesting being too deep.
+	 */
+	ent EC_ABSENT	15 GRUB_GDB_LAST_TRAP
+
+/*
+ * Random stuff
+ */
+
+.text
+.globl grub_gdb_breakpoint
+grub_gdb_breakpoint:
+	int $3
+	ret
+
+.globl grub_idt_load
+grub_idt_load:
+        lidt    (%eax)
+        ret
+
+.end
+
+OMG, Bunnies!
+
--- grub2/gdb/i386/signal.c	1970-01-01 01:00:00.000000000 +0100
+++ grub2-gdb/gdb/i386/signal.c	2008-05-01 10:57:57.000000000 +0200
@@ -0,0 +1,53 @@
+/* idt.c - routines for constructing IDT fot the GDB stub */
+/*
+ *  Copyright (C) 2006  Lubomir Kundrak
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <grub/machine/memory.h>
+#include <grub/misc.h>
+#include <grub/cpu/gdb.h>
+#include <grub/gdb.h>
+
+/* Converting CPU trap number to UNIX signal number as
+   described in System V ABI i386 Processor Supplement, 3-25.  */
+int
+grub_gdb_trap2sig (int trap_no)
+{
+  int signals[] = {
+    SIGFPE,			/* 0:   Divide error fault              */
+    SIGTRAP,			/* 1:   Single step trap fault          */
+    SIGABRT,			/* 2:   # Nonmaskable interrupt         */
+    SIGTRAP,			/* 3:   Breakpoint trap                 */
+    SIGSEGV,			/* 4:   Overflow trap                   */
+    SIGSEGV,			/* 5:   Bounds check fault              */
+    SIGILL,			/* 6:   Invalid opcode fault            */
+    SIGFPE,			/* 7:   No coprocessor fault            */
+    SIGABRT,			/* 8:   # Double fault abort            */
+    SIGSEGV,			/* 9:   Coprocessor overrun abort       */
+    SIGSEGV,			/* 10:  Invalid TSS fault               */
+    SIGSEGV,			/* 11:  Segment not present fault       */
+    SIGSEGV,			/* 12:  Stack exception fault           */
+    SIGSEGV,			/* 13:  General protection fault abort  */
+    SIGSEGV,			/* 14:  Page fault                      */
+    SIGABRT,			/* 15:  (reserved)                      */
+    SIGFPE,			/* 16:  Coprocessor error fault         */
+    SIGUSR1			/* other                                */
+  };
+
+  return signals[trap_no < 17 ? trap_no : 17];
+}
+
--- grub2/genmk.rb	2008-04-17 16:14:10.000000000 +0200
+++ grub2-gdb/genmk.rb	2008-05-01 10:57:14.000000000 +0200
@@ -101,10 +101,11 @@ class PModule
     mod_obj = mod_src.suffix('o')
     defsym = 'def-' + @name.suffix('lst')
     undsym = 'und-' + @name.suffix('lst')
+    exec = @name.suffix('elf')
     mod_name = File.basename(@name, '.mod')
     symbolic_name = mod_name.sub(/\.[^\.]*$/, '')
     
-    "CLEANFILES += #{@name} #{mod_obj} #{mod_src} #{pre_obj} #{objs_str} #{undsym}
+    "CLEANFILES += #{@name} #{mod_obj} #{mod_src} #{pre_obj} #{objs_str} #{undsym} #{exec}
 ifneq ($(#{prefix}_EXPORTS),no)
 CLEANFILES += #{defsym}
 DEFSYMFILES += #{defsym}
@@ -112,10 +113,13 @@ endif
 MOSTLYCLEANFILES += #{deps_str}
 UNDSYMFILES += #{undsym}
 
-#{@name}: #{pre_obj} #{mod_obj}
+#{@name}: #{exec}
+	-rm -f $@
+	$(OBJCOPY) --strip-unneeded -K grub_mod_init -K grub_mod_fini -R .note -R .comment $^ $@
+
+#{exec}: #{pre_obj} #{mod_obj}
 	-rm -f $@
 	$(TARGET_CC) $(#{prefix}_LDFLAGS) $(TARGET_LDFLAGS) -Wl,-r,-d -o $@ $^
-	$(STRIP) --strip-unneeded -K grub_mod_init -K grub_mod_fini -R .note -R .comment $@
 
 #{pre_obj}: $(#{prefix}_DEPENDENCIES) #{objs_str}
 	-rm -f $@
--- grub2/include/grub/gdb.h	1970-01-01 01:00:00.000000000 +0100
+++ grub2-gdb/include/grub/gdb.h	2008-05-01 10:57:57.000000000 +0200
@@ -0,0 +1,38 @@
+/* gdb.h - Various definitions for the remote GDB stub */
+/*
+ *  Copyright (C) 2006  Lubomir Kundrak
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef GRUB_GDB_HEADER
+#define GRUB_GDB_HEADER		1
+
+#define SIGFPE		8
+#define SIGTRAP		5
+#define SIGABRT		6
+#define SIGSEGV		11
+#define SIGILL		4
+#define SIGUSR1		30
+/* We probably don't need other ones.  */
+
+extern int (*grub_gdb_getchar) ();
+extern void (*grub_gdb_putchar) (int);
+
+void grub_gdb_breakpoint ();
+int grub_gdb_trap2sig (int);
+
+#endif /* ! GRUB_GDB_HEADER */
+
--- grub2/include/grub/i386/gdb.h	1970-01-01 01:00:00.000000000 +0100
+++ grub2-gdb/include/grub/i386/gdb.h	2008-05-01 10:57:57.000000000 +0200
@@ -0,0 +1,80 @@
+/* i386/gdb.h - i386 specific definitions for the remote GDB stub */
+/*
+ *  Copyright (C) 2006	Lubomir Kundrak
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef GRUB_GDB_CPU_HEADER
+#define GRUB_GDB_CPU_HEADER	1
+
+#define GRUB_GDB_LAST_TRAP	31
+/* You may have to edit the bottom of machdep.S when adjusting
+   GRUB_GDB_LAST_TRAP.	*/
+#define GRUB_MACHINE_NR_REGS	16
+
+#define	EAX	0
+#define	ECX	1
+#define	EDX	2
+#define	EBX	3
+#define	ESP	4
+#define	EBP	5
+#define	ESI	6
+#define	EDI	7
+#define	EIP	8
+#define	EFLAGS	9
+#define	CS	10
+#define	SS	11
+#define	DS	12
+#define	ES	13
+#define	FS	14
+#define	GS	15
+
+#define PC	EIP
+#define FP	EBP
+#define SP	ESP
+#define PS	EFLAGS
+
+#ifndef ASM
+
+#include <grub/gdb.h>
+
+#define GRUB_CPU_TRAP_GATE	15
+
+struct gate
+{
+  unsigned offset_lo:16;
+  unsigned selector:16;
+  unsigned xx:8;
+  unsigned type:5;	/* GRUB_CPU_TRAP_GATE */
+  unsigned dpl:2;
+  unsigned present:1;
+  unsigned offset_hi:16;
+} __attribute__ ((packed));
+
+struct region
+{
+  unsigned limit:16;
+  unsigned base:32;
+} __attribute__ ((packed));
+
+extern void (*grub_gdb_trapvec[]) ();
+extern void grub_gdb_breakpoint ();
+extern void grub_idt_load (struct region *);
+extern void grub_gdb_idtinit ();
+
+#endif /* ! ASM */
+#endif /* ! GRUB_GDB_CPU_HEADER */
+
--- grub2/include/grub/i386/pc/kernel.h	2008-03-24 05:13:36.000000000 +0100
+++ grub2-gdb/include/grub/i386/pc/kernel.h	2008-05-01 14:14:08.000000000 +0200
@@ -44,7 +44,7 @@
 #define GRUB_KERNEL_MACHINE_DATA_END		0x50
 
 /* The size of the first region which won't be compressed.  */
-#define GRUB_KERNEL_MACHINE_RAW_SIZE		0x4A0
+#define GRUB_KERNEL_MACHINE_RAW_SIZE		0x4BC
 
 #ifndef ASM_FILE
 
--- grub2/kern/i386/pc/startup.S	2008-03-30 06:13:47.000000000 +0200
+++ grub2-gdb/kern/i386/pc/startup.S	2008-05-01 12:02:57.000000000 +0200
@@ -276,6 +276,15 @@ VARIABLE(grub_apm_bios_info)
 	.word	0	/* cseg_len */
 	.word	0	/* cseg_16_len */
 	.word	0	/* dseg_16_len */
+
+/* IDT region descriptors */
+VARIABLE(prot_idt)
+	.word	0xffff			/* limit */
+	.long	0x0			/* addr */
+
+VARIABLE(real_idt)
+	.word	0xffff			/* limit */
+	.long	0x0			/* addr */
 	
 	.p2align	2	/* force 4-byte alignment */
 	
@@ -327,6 +336,9 @@ protcseg:
 	/* zero %eax */
 	xorl	%eax, %eax
 
+	/* real mode IDT is no longer pertinent */
+	lidt prot_idt
+
 	/* return on the old (or initialized) stack! */
 	ret
 
@@ -1097,7 +1109,6 @@ xsmap:
 	popl	%ebp
 	ret
 
-	
 /*
  * void grub_console_real_putchar (int c)
  *
--- grub2/kern/i386/realmode.S	2007-10-17 22:04:23.000000000 +0200
+++ grub2-gdb/kern/i386/realmode.S	2008-05-01 12:03:06.000000000 +0200
@@ -120,6 +120,10 @@ prot_to_real:
 	/* just in case, set GDT */
 	lgdt	gdtdesc
 
+	/* our protected mode IDT would cause trouble in real mode */
+	sidt prot_idt
+	lidt real_idt
+
 	/* save the protected mode stack */
 	movl	%esp, %eax
 	movl	%eax, protstack
--- grub2/term/i386/pc/serial.c	2007-12-30 09:52:06.000000000 +0100
+++ grub2-gdb/term/i386/pc/serial.c	2008-05-01 10:58:41.000000000 +0200
@@ -79,7 +79,7 @@ serial_hw_get_port (const unsigned short
 }
 
 /* Fetch a key.  */
-static int
+int
 serial_hw_fetch (void)
 {
   if (grub_inb (serial_settings.port + UART_LSR) & UART_DATA_READY)
@@ -89,7 +89,7 @@ serial_hw_fetch (void)
 }
 
 /* Put a character.  */
-static void
+void
 serial_hw_put (const int c)
 {
   unsigned int timeout = 100000;
@@ -247,7 +247,7 @@ grub_serial_checkkey (void)
 }
 
 /* The serial version of getkey.  */
-static int
+int
 grub_serial_getkey (void)
 {
   int c;