http://sourceware.org/ml/gdb-patches/2015-02/msg00733.html

Subject: [PATCH 4/8] remote+docs: software/hardware breakpoint traps

This adjusts target remote to tell the core whether a trap was caused

by a breakpoint.

To that end, the patch teaches GDB about new RSP stop reasons "T05

swbreak" and "T05 hwbreak", that remote targets report back to GDB,

similarly to how "T05 watch" indicates a stop caused by a watchpoint.

Because targets that can report these events are expected to

themselves adjust the PC after a software breakpoint, these new stop

reasons must only be reported if the stub is talking to a GDB that

understands them.  Because of that, the use of the new stop reasons

needs to be handshaked on initial connection, using the qSupported

mechanism.  GDB simply sends "swbreak+" in its qSupports query, and

the stub reports back "swbreak+" too.

Because these new stop reasons are required to fix a fundamental

non-stop mode problem, this commit extends the remote non-stop intro

section in the manual, documenting the events as required.

To be clear, GDB will still cope with remote targets that don't

support these new stop reasons; it will behave just like today.

Tested on x86-64 Fedora 20, native and gdbserver.

gdb/ChangeLog:

2015-02-25  Pedro Alves  <palves@redhat.com>

	* NEWS: Mention the new "swbreak" and "hwbreak" stop reasons.

	* remote.c (struct remote_state) <remote_stopped_by_watchpoint_p>:

	Delete field.

	<stop_reason>: New field.

	(PACKET_swbreak_feature, PACKET_hwbreak_feature): New enum values.

	(packet_set_cmd_state): New function.

	(remote_protocol_features): Register the "swbreak" and "hwbreak"

	features.

	(remote_query_supported): If not disabled with the corresponding

	"set remote foo-packet" command, report support for the swbreak

	and hwbreak features.

	(struct stop_reply) <remote_stopped_by_watchpoint_p>: Delete

	field.

	<stop_reason>: New field.

	(remote_parse_stop_reply): Handle "swbreak" and "hwbreak".

	(remote_wait_as): Adjust.

	(remote_stopped_by_sw_breakpoint)

	(remote_supports_stopped_by_sw_breakpoint)

	(remote_stopped_by_hw_breakpoint)

	(remote_supports_stopped_by_hw_breakpoint): New functions.

	(remote_stopped_by_watchpoint): New function.

	(init_remote_ops): Install them.

	(_initialize_remote): Register new "set/show remote

	swbreak-feature-packet" and "set/show remote

	swbreak-feature-packet" commands.

gdb/doc/ChangeLog:

2015-02-25  Pedro Alves  <palves@redhat.com>

	* gdb.texinfo (Remote Configuration): Document the "set/show

	remote swbreak-feature-packet" and "set/show remote

	hwbreak-feature-packet" commands.

	(Packets) <Z0>: Add cross link to the "swbreak" stop reason's

	decription.

	(Stop Reply Packets): Document the swbreak and hwbreak stop

	reasons.

	(General Query Packets): Document the swbreak and hwbreak

	qSupported features.

	(Remote Non-Stop): Explain that swbreak and hwbreak are required.

---

 gdb/NEWS            |  10 +++++

 gdb/doc/gdb.texinfo |  80 +++++++++++++++++++++++++++++++++++

 gdb/remote.c        | 119 ++++++++++++++++++++++++++++++++++++++++++++++++----

 3 files changed, 200 insertions(+), 9 deletions(-)

Index: gdb-7.6.1/gdb/remote.c

===================================================================

--- gdb-7.6.1.orig/gdb/remote.c	2016-03-13 19:41:32.258628611 +0100

+++ gdb-7.6.1/gdb/remote.c	2016-03-13 19:42:35.787094677 +0100

@@ -728,6 +728,9 @@

 /* This is non-zero if target stopped for a watchpoint.  */

 static int remote_stopped_by_watchpoint_p;

+/* RHEL: TARGET_STOPPED_BY_HW_BREAKPOINT */

+static int stopped_by_hw_breakpoint;

+

 static struct target_ops remote_ops;

 static struct target_ops extended_remote_ops;

@@ -1289,11 +1292,24 @@

   PACKET_Qbtrace_off,

   PACKET_Qbtrace_bts,

   PACKET_qXfer_btrace,

+

+  /* Support for hwbreak+ feature.  */

+  PACKET_hwbreak_feature,

+

   PACKET_MAX

 };

 static struct packet_config remote_protocol_packets[PACKET_MAX];

+/* Returns the packet's corresponding "set remote foo-packet" command

+   state.  See struct packet_config for more details.  */

+

+static enum auto_boolean

+packet_set_cmd_state (int packet)

+{

+  return remote_protocol_packets[packet].detect;

+}

+

 static void

 set_remote_protocol_packet_cmd (char *args, int from_tty,

 				struct cmd_list_element *c)

@@ -4017,7 +4033,8 @@

   { "Qbtrace:off", PACKET_DISABLE, remote_supported_packet, PACKET_Qbtrace_off },

   { "Qbtrace:bts", PACKET_DISABLE, remote_supported_packet, PACKET_Qbtrace_bts },

   { "qXfer:btrace:read", PACKET_DISABLE, remote_supported_packet,

-    PACKET_qXfer_btrace }

+    PACKET_qXfer_btrace },

+  { "hwbreak", PACKET_DISABLE, remote_supported_packet, PACKET_hwbreak_feature }

 };

 static char *remote_support_xml;

@@ -4086,6 +4103,9 @@

       q = remote_query_supported_append (q, "multiprocess+");

+      if (packet_set_cmd_state (PACKET_hwbreak_feature) != AUTO_BOOLEAN_FALSE)

+	q = remote_query_supported_append (q, "hwbreak+");

+

       if (remote_support_xml)

 	q = remote_query_supported_append (q, remote_support_xml);

@@ -5202,6 +5222,9 @@

   int stopped_by_watchpoint_p;

   CORE_ADDR watch_data_address;

+  /* RHEL: TARGET_STOPPED_BY_HW_BREAKPOINT */

+  int stopped_by_hw_breakpoint;

+

   int solibs_changed;

   int replay_event;

@@ -5467,6 +5490,7 @@

   event->solibs_changed = 0;

   event->replay_event = 0;

   event->stopped_by_watchpoint_p = 0;

+  event->stopped_by_hw_breakpoint = 0;

   event->regcache = NULL;

   event->core = -1;

@@ -5522,6 +5546,23 @@

 		  p = unpack_varlen_hex (++p1, &addr);

 		  event->watch_data_address = (CORE_ADDR) addr;

 		}

+	      else if (strncmp (p, "hwbreak", p1 - p) == 0)

+		{

+		  event->stopped_by_hw_breakpoint = 1;

+

+		  /* Make sure the stub doesn't forget to indicate support

+		     with qSupported.  */

+		  //if (packet_support (PACKET_hwbreak_feature) != PACKET_ENABLE)

+		  //  error (_("Unexpected hwbreak stop reason"));

+

+		  /* See above.  */

+		  //p = skip_to_semicolon (p1 + 1);

+		  p1++;

+		  p_temp = p1;

+		  while (*p_temp && *p_temp != ';')

+		    p_temp++;

+		  p = p_temp;

+		}

 	      else if (strncmp (p, "library", p1 - p) == 0)

 		{

 		  p1++;

@@ -5783,6 +5824,7 @@

       remote_stopped_by_watchpoint_p = stop_reply->stopped_by_watchpoint_p;

       remote_watch_data_address = stop_reply->watch_data_address;

+      stopped_by_hw_breakpoint = stop_reply->stopped_by_hw_breakpoint;

       remote_notice_new_inferior (ptid, 0);

       demand_private_info (ptid)->core = stop_reply->core;

@@ -8310,6 +8352,16 @@

   return -1;

 }

+/* The to_stopped_by_hw_breakpoint method of target remote.  */

+

+static int

+remote_stopped_by_hw_breakpoint (struct target_ops *ops)

+{

+  struct remote_state *rs = get_remote_state ();

+

+  return stopped_by_hw_breakpoint;

+}

+

 static int

 remote_stopped_by_watchpoint (void)

 {

@@ -11372,6 +11424,7 @@

   remote_ops.to_files_info = remote_files_info;

   remote_ops.to_insert_breakpoint = remote_insert_breakpoint;

   remote_ops.to_remove_breakpoint = remote_remove_breakpoint;

+  remote_ops.to_stopped_by_hw_breakpoint = remote_stopped_by_hw_breakpoint;

   remote_ops.to_stopped_by_watchpoint = remote_stopped_by_watchpoint;

   remote_ops.to_stopped_data_address = remote_stopped_data_address;

   remote_ops.to_watchpoint_addr_within_range =

@@ -12010,6 +12063,9 @@

   add_packet_config_cmd (&remote_protocol_packets[PACKET_qXfer_btrace],

        "qXfer:btrace", "read-btrace", 0);

+  add_packet_config_cmd (&remote_protocol_packets[PACKET_hwbreak_feature],

+                         "hwbreak-feature", "hwbreak-feature", 0);

+

   /* Keep the old ``set remote Z-packet ...'' working.  Each individual

      Z sub-packet has its own set and show commands, but users may

      have sets to this variable in their .gdbinit files (or in their