Add h/w watchpoint support to x86-linux, win32-i386.

	* Makefile.in (SFILES): Add i386-low.c
	(i386_low_h): Define.
	(i386-low.o): Add dependencies.
	(linux-x86-low.o): Add i386-low.h dependency.
	(win32-i386-low.o): Ditto.
	* i386-low.c: New file.
	* i386-low.h: New file.
	* configure.srv (i[34567]86-*-cygwin*): Add i386-low.o to srv_tgtobj.
	(i[34567]86-*-linux*, i[34567]86-*-mingw*, x86_64-*-linux*): Ditto.
	* linux-low.c (linux_add_process): Initialize arch_private.
	(linux_remove_process): Free arch_private.
	(add_lwp): Initialize arch_private.
	(delete_lwp): Free arch_private.
	(linux_resume_one_lwp): Call the_low_target.prepare_to_resume if
	provided.
	* linux-low.h (process_info_private): New member arch_private.
	(lwp_info): New member arch_private.
	(linux_target_ops): New members new_process, new_thread,
	prepare_to_resume.
	(ptid_of): New macro.
	* linux-x86-low.c: Include stddef.h, i386-low.h.
	(arch_process_info): New struct.
	(arch_lwp_info): New struct.
	(x86_linux_dr_get, x86_linux_dr_set): New functions.
	(i386_dr_low_set_addr, i386_dr_low_set_control): New functions.
	(i386_dr_low_get_status): New function.
	(x86_insert_point, x86_remove_point): New functions.
	(x86_stopped_by_watchpoint): New function.
	(x86_stopped_data_address): New function.
	(x86_linux_new_process, x86_linux_new_thread): New functions.
	(x86_linux_prepare_to_resume): New function.
	(the_low_target): Add entries for insert_point, remove_point,
	stopped_by_watchpoint, stopped_data_address, new_process, new_thread,
	prepare_to_resume.
	* server.c (debug_hw_points): New global.
	(monitor_show_help): Document set debug-hw-points.
	(handle_query): Process "set debug-hw-points".
	* server.h (debug_hw_points): Declare.
	(paddress): Declare.
	* utils.c (NUMCELLS, CELLSIZE): New macros.
	(get_sell, xsnprintf, paddress): New functions.
	* win32-arm-low.c (the_low_target): Add entries for insert_point,
	remove_point, stopped_by_watchpoint, stopped_data_address.
	* win32-i386-low.c: Include i386-low.h.
	(debug_reg_state): Replaces dr.
	(i386_dr_low_set_addr, i386_dr_low_set_control): New functions.
	(i386_dr_low_get_status): New function.
	(i386_insert_point, i386_remove_point): New functions.
	(i386_stopped_by_watchpoint): New function.
	(i386_stopped_data_address): New function.
	(i386_initial_stuff): Update.
	(get_thread_context,set_thread_context,i386_thread_added): Update.
	(the_low_target): Add entries for insert_point,
	remove_point, stopped_by_watchpoint, stopped_data_address.
	* win32-low.c (win32_insert_watchpoint): New function.
	(win32_remove_watchpoint): New function.
	(win32_stopped_by_watchpoint): New function.
	(win32_stopped_data_address): New function.
	(win32_target_ops): Add entries for insert_watchpoint,
	remove_watchpoint, stopped_by_watchpoint, stopped_data_address.
	* win32-low.h (win32_target_ops): New members insert_point,
	remove_point, stopped_by_watchpoint, stopped_data_address.

2 files changed, 686 insertions, 0 deletions

diff --git a/gdb/gdbserver/i386-low.c b/gdb/gdbserver/i386-low.c
new file mode 100644
index 0000000..c3d0336
--- /dev/null
+++ b/gdb/gdbserver/i386-low.c
@@ -0,0 +1,577 @@
+/* Debug register code for the i386.
+
+   Copyright (C) 2009
+   Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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 3 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, see <http://www.gnu.org/licenses/>.  */
+
+#include "server.h"
+#include "target.h"
+#include "i386-low.h"
+
+/* Support for 8-byte wide hw watchpoints.  */
+#ifndef TARGET_HAS_DR_LEN_8
+/* NOTE: sizeof (long) == 4 on win64.  */
+#define TARGET_HAS_DR_LEN_8 (sizeof (void *) == 8)
+#endif
+
+enum target_hw_bp_type
+  {
+    hw_write   = 0,	/* Common  HW watchpoint */
+    hw_read    = 1,	/* Read    HW watchpoint */
+    hw_access  = 2,	/* Access  HW watchpoint */
+    hw_execute = 3	/* Execute HW breakpoint */
+  };
+
+/* DR7 Debug Control register fields.  */
+
+/* How many bits to skip in DR7 to get to R/W and LEN fields.  */
+#define DR_CONTROL_SHIFT	16
+/* How many bits in DR7 per R/W and LEN field for each watchpoint.  */
+#define DR_CONTROL_SIZE		4
+
+/* Watchpoint/breakpoint read/write fields in DR7.  */
+#define DR_RW_EXECUTE	(0x0)	/* Break on instruction execution.  */
+#define DR_RW_WRITE	(0x1)	/* Break on data writes.  */
+#define DR_RW_READ	(0x3)	/* Break on data reads or writes.  */
+
+/* This is here for completeness.  No platform supports this
+   functionality yet (as of March 2001).  Note that the DE flag in the
+   CR4 register needs to be set to support this.  */
+#ifndef DR_RW_IORW
+#define DR_RW_IORW	(0x2)	/* Break on I/O reads or writes.  */
+#endif
+
+/* Watchpoint/breakpoint length fields in DR7.  The 2-bit left shift
+   is so we could OR this with the read/write field defined above.  */
+#define DR_LEN_1	(0x0 << 2) /* 1-byte region watch or breakpoint.  */
+#define DR_LEN_2	(0x1 << 2) /* 2-byte region watch.  */
+#define DR_LEN_4	(0x3 << 2) /* 4-byte region watch.  */
+#define DR_LEN_8	(0x2 << 2) /* 8-byte region watch (AMD64).  */
+
+/* Local and Global Enable flags in DR7.
+
+   When the Local Enable flag is set, the breakpoint/watchpoint is
+   enabled only for the current task; the processor automatically
+   clears this flag on every task switch.  When the Global Enable flag
+   is set, the breakpoint/watchpoint is enabled for all tasks; the
+   processor never clears this flag.
+
+   Currently, all watchpoint are locally enabled.  If you need to
+   enable them globally, read the comment which pertains to this in
+   i386_insert_aligned_watchpoint below.  */
+#define DR_LOCAL_ENABLE_SHIFT	0 /* Extra shift to the local enable bit.  */
+#define DR_GLOBAL_ENABLE_SHIFT	1 /* Extra shift to the global enable bit.  */
+#define DR_ENABLE_SIZE		2 /* Two enable bits per debug register.  */
+
+/* Local and global exact breakpoint enable flags (a.k.a. slowdown
+   flags).  These are only required on i386, to allow detection of the
+   exact instruction which caused a watchpoint to break; i486 and
+   later processors do that automatically.  We set these flags for
+   backwards compatibility.  */
+#define DR_LOCAL_SLOWDOWN	(0x100)
+#define DR_GLOBAL_SLOWDOWN	(0x200)
+
+/* Fields reserved by Intel.  This includes the GD (General Detect
+   Enable) flag, which causes a debug exception to be generated when a
+   MOV instruction accesses one of the debug registers.
+
+   FIXME: My Intel manual says we should use 0xF800, not 0xFC00.  */
+#define DR_CONTROL_RESERVED	(0xFC00)
+
+/* Auxiliary helper macros.  */
+
+/* A value that masks all fields in DR7 that are reserved by Intel.  */
+#define I386_DR_CONTROL_MASK	(~DR_CONTROL_RESERVED)
+
+/* The I'th debug register is vacant if its Local and Global Enable
+   bits are reset in the Debug Control register.  */
+#define I386_DR_VACANT(state, i) \
+  (((state)->dr_control_mirror & (3 << (DR_ENABLE_SIZE * (i)))) == 0)
+
+/* Locally enable the break/watchpoint in the I'th debug register.  */
+#define I386_DR_LOCAL_ENABLE(state, i) \
+  do { \
+    (state)->dr_control_mirror |= \
+      (1 << (DR_LOCAL_ENABLE_SHIFT + DR_ENABLE_SIZE * (i))); \
+  } while (0)
+
+/* Globally enable the break/watchpoint in the I'th debug register.  */
+#define I386_DR_GLOBAL_ENABLE(state, i) \
+  do { \
+    (state)->dr_control_mirror |= \
+      (1 << (DR_GLOBAL_ENABLE_SHIFT + DR_ENABLE_SIZE * (i))); \
+  } while (0)
+
+/* Disable the break/watchpoint in the I'th debug register.  */
+#define I386_DR_DISABLE(state, i) \
+  do { \
+    (state)->dr_control_mirror &= \
+      ~(3 << (DR_ENABLE_SIZE * (i))); \
+  } while (0)
+
+/* Set in DR7 the RW and LEN fields for the I'th debug register.  */
+#define I386_DR_SET_RW_LEN(state, i,rwlen) \
+  do { \
+    (state)->dr_control_mirror &= \
+      ~(0x0f << (DR_CONTROL_SHIFT + DR_CONTROL_SIZE * (i))); \
+    (state)->dr_control_mirror |= \
+      ((rwlen) << (DR_CONTROL_SHIFT + DR_CONTROL_SIZE * (i))); \
+  } while (0)
+
+/* Get from DR7 the RW and LEN fields for the I'th debug register.  */
+#define I386_DR_GET_RW_LEN(state, i) \
+  (((state)->dr_control_mirror \
+    >> (DR_CONTROL_SHIFT + DR_CONTROL_SIZE * (i))) & 0x0f)
+
+/* Did the watchpoint whose address is in the I'th register break?  */
+#define I386_DR_WATCH_HIT(state,i) ((state)->dr_status_mirror & (1 << (i)))
+
+/* A macro to loop over all debug registers.  */
+#define ALL_DEBUG_REGISTERS(i)	for (i = 0; i < DR_NADDR; i++)
+
+/* Types of operations supported by i386_handle_nonaligned_watchpoint.  */
+typedef enum { WP_INSERT, WP_REMOVE, WP_COUNT } i386_wp_op_t;
+
+/* Implementation.  */
+
+/* Clear the reference counts and forget everything we knew about the
+   debug registers.  */
+
+void
+i386_low_init_dregs (struct i386_debug_reg_state *state)
+{
+  int i;
+
+  ALL_DEBUG_REGISTERS (i)
+    {
+      state->dr_mirror[i] = 0;
+      state->dr_ref_count[i] = 0;
+    }
+  state->dr_control_mirror = 0;
+  state->dr_status_mirror  = 0;
+}
+
+/* Print the values of the mirrored debug registers.  This is enabled via
+   the "set debug-hw-points 1" monitor command.  */
+
+static void
+i386_show_dr (struct i386_debug_reg_state *state,
+	      const char *func, CORE_ADDR addr,
+	      int len, enum target_hw_bp_type type)
+{
+  int i;
+
+  fprintf (stderr, "%s", func);
+  if (addr || len)
+    fprintf (stderr, " (addr=%lx, len=%d, type=%s)",
+	     (unsigned long) addr, len,
+	     type == hw_write ? "data-write"
+	     : (type == hw_read ? "data-read"
+		: (type == hw_access ? "data-read/write"
+		   : (type == hw_execute ? "instruction-execute"
+		      /* FIXME: if/when I/O read/write
+			 watchpoints are supported, add them
+			 here.  */
+		      : "??unknown??"))));
+  fprintf (stderr, ":\n");
+  fprintf (stderr, "\tCONTROL (DR7): %08x          STATUS (DR6): %08x\n",
+	   state->dr_control_mirror, state->dr_status_mirror);
+  ALL_DEBUG_REGISTERS (i)
+    {
+      fprintf (stderr, "\
+\tDR%d: addr=0x%s, ref.count=%d  DR%d: addr=0x%s, ref.count=%d\n",
+	      i, paddress (state->dr_mirror[i]),
+	      state->dr_ref_count[i],
+	      i + 1, paddress (state->dr_mirror[i + 1]),
+	      state->dr_ref_count[i + 1]);
+      i++;
+    }
+}
+
+/* Return the value of a 4-bit field for DR7 suitable for watching a
+   region of LEN bytes for accesses of type TYPE.  LEN is assumed to
+   have the value of 1, 2, or 4.  */
+
+static unsigned
+i386_length_and_rw_bits (int len, enum target_hw_bp_type type)
+{
+  unsigned rw;
+
+  switch (type)
+    {
+      case hw_execute:
+	rw = DR_RW_EXECUTE;
+	break;
+      case hw_write:
+	rw = DR_RW_WRITE;
+	break;
+      case hw_read:
+	/* The i386 doesn't support data-read watchpoints.  */
+      case hw_access:
+	rw = DR_RW_READ;
+	break;
+#if 0
+	/* Not yet supported.  */
+      case hw_io_access:
+	rw = DR_RW_IORW;
+	break;
+#endif
+      default:
+	error ("\
+Invalid hardware breakpoint type %d in i386_length_and_rw_bits.\n",
+			(int) type);
+    }
+
+  switch (len)
+    {
+      case 1:
+	return (DR_LEN_1 | rw);
+      case 2:
+	return (DR_LEN_2 | rw);
+      case 4:
+	return (DR_LEN_4 | rw);
+      case 8:
+        if (TARGET_HAS_DR_LEN_8)
+ 	  return (DR_LEN_8 | rw);
+      default:
+	error ("\
+Invalid hardware breakpoint length %d in i386_length_and_rw_bits.\n", len);
+    }
+}
+
+/* Insert a watchpoint at address ADDR, which is assumed to be aligned
+   according to the length of the region to watch.  LEN_RW_BITS is the
+   value of the bits from DR7 which describes the length and access
+   type of the region to be watched by this watchpoint.  Return 0 on
+   success, -1 on failure.  */
+
+static int
+i386_insert_aligned_watchpoint (struct i386_debug_reg_state *state,
+				CORE_ADDR addr, unsigned len_rw_bits)
+{
+  int i;
+
+  /* First, look for an occupied debug register with the same address
+     and the same RW and LEN definitions.  If we find one, we can
+     reuse it for this watchpoint as well (and save a register).  */
+  ALL_DEBUG_REGISTERS (i)
+    {
+      if (!I386_DR_VACANT (state, i)
+	  && state->dr_mirror[i] == addr
+	  && I386_DR_GET_RW_LEN (state, i) == len_rw_bits)
+	{
+	  state->dr_ref_count[i]++;
+	  return 0;
+	}
+    }
+
+  /* Next, look for a vacant debug register.  */
+  ALL_DEBUG_REGISTERS (i)
+    {
+      if (I386_DR_VACANT (state, i))
+	break;
+    }
+
+  /* No more debug registers!  */
+  if (i >= DR_NADDR)
+    return -1;
+
+  /* Now set up the register I to watch our region.  */
+
+  /* Record the info in our local mirrored array.  */
+  state->dr_mirror[i] = addr;
+  state->dr_ref_count[i] = 1;
+  I386_DR_SET_RW_LEN (state, i, len_rw_bits);
+  /* Note: we only enable the watchpoint locally, i.e. in the current
+     task.  Currently, no i386 target allows or supports global
+     watchpoints; however, if any target would want that in the
+     future, GDB should probably provide a command to control whether
+     to enable watchpoints globally or locally, and the code below
+     should use global or local enable and slow-down flags as
+     appropriate.  */
+  I386_DR_LOCAL_ENABLE (state, i);
+  state->dr_control_mirror |= DR_LOCAL_SLOWDOWN;
+  state->dr_control_mirror &= I386_DR_CONTROL_MASK;
+
+  /* Finally, actually pass the info to the inferior.  */
+  i386_dr_low_set_addr (state, i);
+  i386_dr_low_set_control (state);
+
+  return 0;
+}
+
+/* Remove a watchpoint at address ADDR, which is assumed to be aligned
+   according to the length of the region to watch.  LEN_RW_BITS is the
+   value of the bits from DR7 which describes the length and access
+   type of the region watched by this watchpoint.  Return 0 on
+   success, -1 on failure.  */
+
+static int
+i386_remove_aligned_watchpoint (struct i386_debug_reg_state *state,
+				CORE_ADDR addr, unsigned len_rw_bits)
+{
+  int i, retval = -1;
+
+  ALL_DEBUG_REGISTERS (i)
+    {
+      if (!I386_DR_VACANT (state, i)
+	  && state->dr_mirror[i] == addr
+	  && I386_DR_GET_RW_LEN (state, i) == len_rw_bits)
+	{
+	  if (--state->dr_ref_count[i] == 0) /* No longer in use?  */
+	    {
+	      /* Reset our mirror.  */
+	      state->dr_mirror[i] = 0;
+	      I386_DR_DISABLE (state, i);
+	      /* Reset it in the inferior.  */
+	      i386_dr_low_set_control (state);
+	      i386_dr_low_set_addr (state, i);
+	    }
+	  retval = 0;
+	}
+    }
+
+  return retval;
+}
+
+/* Insert or remove a (possibly non-aligned) watchpoint, or count the
+   number of debug registers required to watch a region at address
+   ADDR whose length is LEN for accesses of type TYPE.  Return 0 on
+   successful insertion or removal, a positive number when queried
+   about the number of registers, or -1 on failure.  If WHAT is not a
+   valid value, bombs through internal_error.  */
+
+static int
+i386_handle_nonaligned_watchpoint (struct i386_debug_reg_state *state,
+				   i386_wp_op_t what, CORE_ADDR addr, int len,
+				   enum target_hw_bp_type type)
+{
+  int retval = 0, status = 0;
+  int max_wp_len = TARGET_HAS_DR_LEN_8 ? 8 : 4;
+
+  static const int size_try_array[8][8] =
+  {
+    {1, 1, 1, 1, 1, 1, 1, 1},	/* Trying size one.  */
+    {2, 1, 2, 1, 2, 1, 2, 1},	/* Trying size two.  */
+    {2, 1, 2, 1, 2, 1, 2, 1},	/* Trying size three.  */
+    {4, 1, 2, 1, 4, 1, 2, 1},	/* Trying size four.  */
+    {4, 1, 2, 1, 4, 1, 2, 1},	/* Trying size five.  */
+    {4, 1, 2, 1, 4, 1, 2, 1},	/* Trying size six.  */
+    {4, 1, 2, 1, 4, 1, 2, 1},	/* Trying size seven.  */
+    {8, 1, 2, 1, 4, 1, 2, 1},	/* Trying size eight.  */
+  };
+
+  while (len > 0)
+    {
+      int align = addr % max_wp_len;
+      /* Four (eight on AMD64) is the maximum length a debug register
+	 can watch.  */
+      int try = (len > max_wp_len ? (max_wp_len - 1) : len - 1);
+      int size = size_try_array[try][align];
+
+      if (what == WP_COUNT)
+	{
+	  /* size_try_array[] is defined such that each iteration
+	     through the loop is guaranteed to produce an address and a
+	     size that can be watched with a single debug register.
+	     Thus, for counting the registers required to watch a
+	     region, we simply need to increment the count on each
+	     iteration.  */
+	  retval++;
+	}
+      else
+	{
+	  unsigned len_rw = i386_length_and_rw_bits (size, type);
+
+	  if (what == WP_INSERT)
+	    status = i386_insert_aligned_watchpoint (state, addr, len_rw);
+	  else if (what == WP_REMOVE)
+	    status = i386_remove_aligned_watchpoint (state, addr, len_rw);
+	  else
+	    fatal ("\
+Invalid value %d of operation in i386_handle_nonaligned_watchpoint.\n",
+		   (int) what);
+
+	  /* We keep the loop going even after a failure, because some
+	     of the other aligned watchpoints might still succeed
+	     (e.g. if they watch addresses that are already watched,
+	     in which case we just increment the reference counts of
+	     occupied debug registers).  If we break out of the loop
+	     too early, we could cause those addresses watched by
+	     other watchpoints to be disabled when breakpoint.c reacts
+	     to our failure to insert this watchpoint and tries to
+	     remove it.  */
+	  if (status)
+	    retval = status;
+	}
+
+      addr += size;
+      len -= size;
+    }
+
+  return retval;
+}
+
+#define Z_PACKET_WRITE_WP '2'
+#define Z_PACKET_READ_WP '3'
+#define Z_PACKET_ACCESS_WP '4'
+
+/* Map the protocol watchpoint type TYPE to enum target_hw_bp_type.  */
+
+static enum target_hw_bp_type
+Z_packet_to_hw_type (char type)
+{
+  switch (type)
+    {
+    case Z_PACKET_WRITE_WP:
+      return hw_write;
+    case Z_PACKET_READ_WP:
+      return hw_read;
+    case Z_PACKET_ACCESS_WP:
+      return hw_access;
+    default:
+      fatal ("Z_packet_to_hw_type: bad watchpoint type %c", type);
+    }
+}
+
+/* Insert a watchpoint to watch a memory region which starts at
+   address ADDR and whose length is LEN bytes.  Watch memory accesses
+   of the type TYPE_FROM_PACKET.  Return 0 on success, -1 on failure.  */
+
+int
+i386_low_insert_watchpoint (struct i386_debug_reg_state *state,
+			    char type_from_packet, CORE_ADDR addr, int len)
+{
+  int retval;
+  enum target_hw_bp_type type = Z_packet_to_hw_type (type_from_packet);
+
+  if (((len != 1 && len != 2 && len != 4)
+       && !(TARGET_HAS_DR_LEN_8 && len == 8))
+      || addr % len != 0)
+    {
+      retval = i386_handle_nonaligned_watchpoint (state, WP_INSERT,
+						  addr, len, type);
+    }
+  else
+    {
+      unsigned len_rw = i386_length_and_rw_bits (len, type);
+
+      retval = i386_insert_aligned_watchpoint (state, addr, len_rw);
+    }
+
+  if (debug_hw_points)
+    i386_show_dr (state, "insert_watchpoint", addr, len, type);
+
+  return retval;
+}
+
+/* Remove a watchpoint that watched the memory region which starts at
+   address ADDR, whose length is LEN bytes, and for accesses of the
+   type TYPE_FROM_PACKET.  Return 0 on success, -1 on failure.  */
+
+int
+i386_low_remove_watchpoint (struct i386_debug_reg_state *state,
+			    char type_from_packet, CORE_ADDR addr, int len)
+{
+  int retval;
+  enum target_hw_bp_type type = Z_packet_to_hw_type (type_from_packet);
+
+  if (((len != 1 && len != 2 && len != 4)
+       && !(TARGET_HAS_DR_LEN_8 && len == 8))
+      || addr % len != 0)
+    {
+      retval = i386_handle_nonaligned_watchpoint (state, WP_REMOVE,
+						  addr, len, type);
+    }
+  else
+    {
+      unsigned len_rw = i386_length_and_rw_bits (len, type);
+
+      retval = i386_remove_aligned_watchpoint (state, addr, len_rw);
+    }
+
+  if (debug_hw_points)
+    i386_show_dr (state, "remove_watchpoint", addr, len, type);
+
+  return retval;
+}
+
+/* Return non-zero if we can watch a memory region that starts at
+   address ADDR and whose length is LEN bytes.  */
+
+int
+i386_low_region_ok_for_watchpoint (struct i386_debug_reg_state *state,
+				   CORE_ADDR addr, int len)
+{
+  int nregs;
+
+  /* Compute how many aligned watchpoints we would need to cover this
+     region.  */
+  nregs = i386_handle_nonaligned_watchpoint (state, WP_COUNT,
+					     addr, len, hw_write);
+  return nregs <= DR_NADDR ? 1 : 0;
+}
+
+/* If the inferior has some break/watchpoint that triggered, set the
+   address associated with that break/watchpoint and return true.
+   Otherwise, return false.  */
+
+int
+i386_low_stopped_data_address (struct i386_debug_reg_state *state,
+			       CORE_ADDR *addr_p)
+{
+  CORE_ADDR addr = 0;
+  int i;
+  int rc = 0;
+
+  /* Get dr_status_mirror for use by I386_DR_WATCH_HIT.  */
+  i386_dr_low_get_status (state);
+
+  ALL_DEBUG_REGISTERS (i)
+    {
+      if (I386_DR_WATCH_HIT (state, i)
+	  /* This second condition makes sure DRi is set up for a data
+	     watchpoint, not a hardware breakpoint.  The reason is
+	     that GDB doesn't call the target_stopped_data_address
+	     method except for data watchpoints.  In other words, I'm
+	     being paranoiac.  */
+	  && I386_DR_GET_RW_LEN (state, i) != 0)
+	{
+	  addr = state->dr_mirror[i];
+	  rc = 1;
+	  if (debug_hw_points)
+	    i386_show_dr (state, "watchpoint_hit", addr, -1, hw_write);
+	}
+    }
+
+  if (debug_hw_points && addr == 0)
+    i386_show_dr (state, "stopped_data_addr", 0, 0, hw_write);
+
+  if (rc)
+    *addr_p = addr;
+  return rc;
+}
+
+/* Return true if the inferior has some watchpoint that triggered.
+   Otherwise return false.  */
+
+int
+i386_low_stopped_by_watchpoint (struct i386_debug_reg_state *state)
+{
+  CORE_ADDR addr = 0;
+  return i386_low_stopped_data_address (state, &addr);
+}
diff --git a/gdb/gdbserver/i386-low.h b/gdb/gdbserver/i386-low.h
new file mode 100644
index 0000000..8b56ad0
--- /dev/null
+++ b/gdb/gdbserver/i386-low.h
@@ -0,0 +1,109 @@
+/* Misc. low level support for i386.
+
+   Copyright (C) 2009
+   Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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 3 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, see <http://www.gnu.org/licenses/>.  */
+
+/* Support for hardware watchpoints and breakpoints using the i386
+   debug registers.
+
+   This provides several functions for inserting and removing
+   hardware-assisted breakpoints and watchpoints, testing if one or
+   more of the watchpoints triggered and at what address, checking
+   whether a given region can be watched, etc.
+
+   The functions below implement debug registers sharing by reference
+   counts, and allow to watch regions up to 16 bytes long
+   (32 bytes on 64 bit hosts).  */
+
+
+/* Debug registers' indices.  */
+#define DR_FIRSTADDR 0
+#define DR_LASTADDR  3
+#define DR_NADDR     4 /* The number of debug address registers.  */
+#define DR_STATUS    6
+#define DR_CONTROL   7
+
+/* Global state needed to track h/w watchpoints.  */
+
+struct i386_debug_reg_state
+{
+  /* Mirror the inferior's DRi registers.  We keep the status and
+     control registers separated because they don't hold addresses.  */
+  CORE_ADDR dr_mirror[DR_NADDR];
+  unsigned dr_status_mirror, dr_control_mirror;
+
+  /* Reference counts for each debug register.  */
+  int dr_ref_count[DR_NADDR];
+};
+
+/* Initialize STATE.  */
+extern void i386_low_init_dregs (struct i386_debug_reg_state *state);
+
+/* Insert a watchpoint to watch a memory region which starts at
+   address ADDR and whose length is LEN bytes.  Watch memory accesses
+   of the type TYPE_FROM_PACKET.  Return 0 on success, -1 on failure.  */
+extern int i386_low_insert_watchpoint (struct i386_debug_reg_state *state,
+				       char type_from_packet, CORE_ADDR addr,
+				       int len);
+
+/* Remove a watchpoint that watched the memory region which starts at
+   address ADDR, whose length is LEN bytes, and for accesses of the
+   type TYPE_FROM_PACKET.  Return 0 on success, -1 on failure.  */
+extern int i386_low_remove_watchpoint (struct i386_debug_reg_state *state,
+				       char type_from_packet, CORE_ADDR addr,
+				       int len);
+
+/* Return non-zero if we can watch a memory region that starts at
+   address ADDR and whose length is LEN bytes.  */
+extern int i386_low_region_ok_for_watchpoint (struct i386_debug_reg_state *state,
+					      CORE_ADDR addr, int len);
+
+/* If the inferior has some break/watchpoint that triggered, set the
+   address associated with that break/watchpoint and return true.
+   Otherwise, return false.  */
+extern int i386_low_stopped_data_address (struct i386_debug_reg_state *state,
+					  CORE_ADDR *addr_p);
+
+/* Return true if the inferior has some watchpoint that triggered.
+   Otherwise return false.  */
+extern int i386_low_stopped_by_watchpoint (struct i386_debug_reg_state *state);
+
+/* Each target needs to provide several low-level functions
+   that will be called to insert watchpoints and hardware breakpoints
+   into the inferior, remove them, and check their status.  These
+   functions are:
+
+      i386_dr_low_set_control  -- set the debug control (DR7)
+				  register to a given value
+
+      i386_dr_low_set_addr     -- put an address into one debug register
+
+      i386_dr_low_get_status   -- return the value of the debug
+				  status (DR6) register.
+*/
+
+/* Update the inferior's debug register REGNUM from STATE.  */
+extern void i386_dr_low_set_addr (const struct i386_debug_reg_state *state,
+				  int regnum);
+
+/* Update the inferior's DR7 debug control register from STATE.  */
+extern void i386_dr_low_set_control (const struct i386_debug_reg_state *state);
+
+/* Get the value of the inferior's DR6 debug status register
+   and record it in STATE.  */
+extern void i386_dr_low_get_status (struct i386_debug_reg_state *state);