RE: symbolic debug of loadable modules with kgdb light

[Caz Yokoyama <cazyokoyama@gmail.com>]

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Hello Joel and Eli,
Here is the patch which integrates your inputs. Even though I carefully look
through your inputs, there may be missing. Let me know if you find.

Notes:
- Use Ctrl-C, BREAK and SysRq-g according to Eli's suggestion.
- "make info" in gdb/doc has no complain.
- I always test the connection with Linux kernel.
- I did manual test like "help remote interrupt-sequence" and see its
output.
- I ran "make check". Let me know if you want its output.
-caz

-----Original Message-----
From: Joel Brobecker [mailto:brobecker@adacore.com] 
Sent: Wednesday, September 30, 2009 1:12 PM
To: Eli Zaretskii
Cc: Caz Yokoyama; pedro@codesourcery.com; gdb-patches@sourceware.org
Subject: Re: symbolic debug of loadable modules with kgdb light

> > +@item set interrupt-sequence
> > +@cindex interrupt remote programs
> > +@cindex select control-c, break or sysrq-g

BTW: It should be "set remote interrupt-sequence". Same for "show remote
interrupt-sequence".

-- 
Joel

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Index: gdb/ChangeLog
===================================================================
RCS file: /cvs/src/src/gdb/ChangeLog,v
retrieving revision 1.10923
diff -u -r1.10923 ChangeLog
--- gdb/ChangeLog	29 Sep 2009 16:27:05 -0000	1.10923
+++ gdb/ChangeLog	1 Oct 2009 03:32:17 -0000
@@ -1,3 +1,17 @@
+2009-09-30  Kazuyoshi Caz Yokoyama  <caz@caztech.com>
+
+        * remote.c (interrupt_sequence_control_c)
+        (interrupt_sequence_break, interrupt_sequence_sysrq_g)
+        (interrupt_sequence_modes): New constants.
+        (interrupt_sequence_mode, interrupt_on_connect): New variable.
+	(show_interrupt_sequence): New function.
+        (set_remotebreak, show_remotebreak): New function.
+	(send_interrupt_sequence: New function.
+	(remote_start_remote): Call send_interrupt_sequence if interrupt_on_connect.
+	(remote_stop_as): Call send_interrupt_sequence.
+	(_initialize_remote): Add interrupt-sequence and interrupt-on-connect,
+	modify remotebreak to call set_remotebreak and show_remotebreak.
+
 2009-09-29  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
 	* ia64-tdep.c (ia64_convert_from_func_ptr_addr): New variable buf.
Index: gdb/NEWS
===================================================================
RCS file: /cvs/src/src/gdb/NEWS,v
retrieving revision 1.331
diff -u -r1.331 NEWS
--- gdb/NEWS	15 Sep 2009 03:30:04 -0000	1.331
+++ gdb/NEWS	1 Oct 2009 03:32:18 -0000
@@ -3,6 +3,9 @@
 
 *** Changes since GDB 6.8
 
+* "set/show remotebreak" command is deprecated. Use "set/show remote
+interrupt-sequence" instead.
+
 * GDB now has an interface for JIT compilation.  Applications that
 dynamically generate code can create symbol files in memory and register
 them with GDB.  For users, the feature should work transparently, and
@@ -234,6 +237,20 @@
 
 * New commands (for set/show, see "New options" below)
 
+set remote interrupt-sequence [Ctrl-C | BREAK | SysRq-g]
+show remote interrupt-sequence
+  Allow the user to select one of ^C, a break or Magic SysRq g as the
+  sequence to the remote target in order to interrupt the execution.
+  Ctrl-C is a default.  Some system prefers BREAK which is high level of
+  serial line for some certain time.  Linux kernel prefers SysRq-g, a.k.a
+  Magic SysRq. It is BREAK signal and character 'g'.
+
+set remote interrupt-on-connect [on | off]
+show remote interrupt-on-connect
+  When interrupt-on-connect is ON, gdb sends interrupt-sequence to
+  remote target when gdb connects to it.  This is needed when you debug
+  Linux kernel.
+
 catch syscall [NAME(S) | NUMBER(S)]
   Catch system calls.  Arguments, which should be names of system
   calls or their numbers, mean catch only those syscalls.  Without
Index: gdb/remote.c
===================================================================
RCS file: /cvs/src/src/gdb/remote.c,v
retrieving revision 1.372
diff -u -r1.372 remote.c
--- gdb/remote.c	10 Sep 2009 22:47:56 -0000	1.372
+++ gdb/remote.c	1 Oct 2009 03:32:21 -0000
@@ -546,14 +546,76 @@
    this can go away.  */
 static int wait_forever_enabled_p = 1;
 
+/* Allow the user to specify what sequence to send to the remote
+   when he requests a program interruption: Although ^C is usually
+   what remote systems expect (this is the default, here), it is
+   sometimes preferable to send a break.  On other systems such
+   as the Linux kernel, a break followed by g, which is Magic SysRq g
+   is required in order to interrupt the execution.  */
+const char interrupt_sequence_control_c[] = "Ctrl-C";
+const char interrupt_sequence_break[] = "BREAK";
+const char interrupt_sequence_sysrq_g[] = "SysRq-g";
+static const char *interrupt_sequence_modes[] =
+  {
+    interrupt_sequence_control_c,
+    interrupt_sequence_break,
+    interrupt_sequence_sysrq_g,
+    NULL
+  };
+static const char *interrupt_sequence_mode = interrupt_sequence_control_c;
 
-/* This variable chooses whether to send a ^C or a break when the user
-   requests program interruption.  Although ^C is usually what remote
-   systems expect, and that is the default here, sometimes a break is
-   preferable instead.  */
+static void
+show_interrupt_sequence (struct ui_file *file, int from_tty,
+			 struct cmd_list_element *c,
+			 const char *value)
+{
+  if (interrupt_sequence_mode == interrupt_sequence_control_c)
+    fprintf_filtered (file,
+		      _("Send the ASCII ETX character (Ctrl-c) "
+			"to the remote target to interrupt the "
+			"execution of the program.\n"));
+  else if (interrupt_sequence_mode == interrupt_sequence_break)
+    fprintf_filtered (file,
+		      _("send a break signal to the remote target "
+			"to interrupt the execution of the program.\n"));
+  else if (interrupt_sequence_mode == interrupt_sequence_sysrq_g)
+    fprintf_filtered (file,
+		      _("Send a break signal and 'g' a.k.a. SysRq-g and Magic SysRq to "
+			"the remote target to interrupt the execution "
+			"of Linux kernel.\n"));
+  else
+    internal_error (__FILE__, __LINE__,
+		    _("Invalid value for interrupt_sequence_mode: %s."),
+		    interrupt_sequence_mode);
+}
 
+/* This boolean variable specifies whether interrupt_sequence is sent
+   to remote target when gdb starts. This is mostly needed when you debug
+   Linux kernel. Linux kernel expects BREAK g which is Magic SysRq for
+   connecting gdb.  */
+static int interrupt_on_connect = 0;
+
+/* This variable is used to implement the "set/show remotebreak" commands.
+   Since these commands are now deprecated in favor of "set/show remote
+   interrupt-sequence", it no longer has any effect on the code.  */
 static int remote_break;
 
+static void
+set_remotebreak (char *args, int from_tty, struct cmd_list_element *c)
+{
+  if (remote_break)
+    interrupt_sequence_mode = interrupt_sequence_break;
+  else
+    interrupt_sequence_mode = interrupt_sequence_control_c;
+}
+
+static void
+show_remotebreak (struct ui_file *file, int from_tty,
+		  struct cmd_list_element *c,
+		  const char *value)
+{
+}
+
 /* Descriptor for I/O to remote machine.  Initialize it to NULL so that
    remote_open knows that we don't have a file open when the program
    starts.  */
@@ -2585,6 +2647,25 @@
   int extended_p;
 };
 
+/* Send interrupt_sequence to remote target.  */
+static void
+send_interrupt_sequence ()
+{
+  if (interrupt_sequence_mode == interrupt_sequence_control_c)
+    serial_write (remote_desc, "\x03", 1);
+  else if (interrupt_sequence_mode == interrupt_sequence_break)
+    serial_send_break (remote_desc);
+  else if (interrupt_sequence_mode == interrupt_sequence_sysrq_g)
+    {
+      serial_send_break (remote_desc);
+      serial_write (remote_desc, "g", 1);
+    }
+  else
+    internal_error (__FILE__, __LINE__,
+		    _("Invalid value for interrupt_sequence_mode: %s."),
+		    interrupt_sequence_mode);
+}
+
 static void
 remote_start_remote (struct ui_out *uiout, void *opaque)
 {
@@ -2598,6 +2679,9 @@
   /* Ack any packet which the remote side has already sent.  */
   serial_write (remote_desc, "+", 1);
 
+  if (interrupt_on_connect)
+    send_interrupt_sequence ();
+
   /* The first packet we send to the target is the optional "supported
      packets" request.  If the target can answer this, it will tell us
      which later probes to skip.  */
@@ -4021,12 +4105,8 @@
   if (rs->cached_wait_status)
     return;
 
-  /* Send a break or a ^C, depending on user preference.  */
-
-  if (remote_break)
-    serial_send_break (remote_desc);
-  else
-    serial_write (remote_desc, "\003", 1);
+  /* Send interrupt_sequence to remote target.  */
+  send_interrupt_sequence ();
 }
 
 /* This is the generic stop called via the target vector. When a target
@@ -8993,6 +9073,10 @@
 _initialize_remote (void)
 {
   struct remote_state *rs;
+  struct cmd_list_element *cmd;
+  /* I can't use the same string for lookup_cmd(). Cause segment fault.  */
+  static char *_set_remotebreak_ = "remotebreak";
+  static char *_show_remotebreak_ = "remotebreak";
 
   /* architecture specific data */
   remote_gdbarch_data_handle =
@@ -9056,12 +9140,33 @@
 terminating `#' character and checksum."),
 	   &maintenancelist);
 
-  add_setshow_boolean_cmd ("remotebreak", no_class, &remote_break, _("\
-Set whether to send break if interrupted."), _("\
-Show whether to send break if interrupted."), _("\
+  add_setshow_boolean_cmd ("remotebreak", class_obscure, &remote_break, _("\
+Deprecated. Use \"set remote interrupt-sequence [control-c|break]\" instead."), _("\
+Deprecated. Use \"show remote interrupt-sequence\" instead."), _("\
 If set, a break, instead of a cntrl-c, is sent to the remote target."),
-			   NULL, NULL, /* FIXME: i18n: Whether to send break if interrupted is %s.  */
+			   set_remotebreak, show_remotebreak,
 			   &setlist, &showlist);
+  cmd = lookup_cmd (&_set_remotebreak_, setlist, "", -1, 1);
+  deprecate_cmd (cmd, "set remote interrupt-sequence");
+  cmd = lookup_cmd (&_show_remotebreak_, showlist, "", -1, 1);
+  deprecate_cmd (cmd, "show remote interrupt-sequence");
+
+  add_setshow_enum_cmd ("interrupt-sequence", class_support,
+			interrupt_sequence_modes, &interrupt_sequence_mode, _("\
+Set interrupt sequence to remote target."), _("\
+Show interrupt sequence to remote target."), _("\
+Valid value is \"Ctrl-C\", \"BREAK\" or \"SysRq-g\". The default is \"Ctrl-C\"."),
+			NULL, show_interrupt_sequence,
+			&remote_set_cmdlist,
+			&remote_show_cmdlist);
+
+  add_setshow_boolean_cmd ("interrupt-on-connect", class_support,
+			   &interrupt_on_connect, _("\
+Set whether interrupt-sequence is sent to remote target when gdb connects to."), _("		\
+Show whether interrupt-sequence is sent to remote target when gdb connects to."), _("		\
+If set, interrupt sequence is sent to remote target."),
+			   NULL, NULL,
+			   &remote_set_cmdlist, &remote_show_cmdlist);
 
   /* Install commands for configuring memory read/write packets.  */
 
Index: gdb/doc/ChangeLog
===================================================================
RCS file: /cvs/src/src/gdb/doc/ChangeLog,v
retrieving revision 1.958
diff -u -r1.958 ChangeLog
--- gdb/doc/ChangeLog	26 Sep 2009 16:47:13 -0000	1.958
+++ gdb/doc/ChangeLog	1 Oct 2009 03:32:23 -0000
@@ -1,3 +1,8 @@
+2009-09-30  Kazuyoshi Caz Yokoyama  <caz@caztech.com>
+
+	* gdb.texinfo (Remote Configuration): Add "set/show remote interrupt-sequence" and
+	"set/show remote interrupt-on-connect" command.
+
 2009-09-26  Pierre Muller  <muller@ics.u-strasbg.fr>
 
 	* gdb.texinfo (Cygwin Native): Mention support for Ctrl-BREAK.
Index: gdb/doc/gdb.texinfo
===================================================================
RCS file: /cvs/src/src/gdb/doc/gdb.texinfo,v
retrieving revision 1.629
diff -u -r1.629 gdb.texinfo
--- gdb/doc/gdb.texinfo	26 Sep 2009 16:47:13 -0000	1.629
+++ gdb/doc/gdb.texinfo	1 Oct 2009 03:32:36 -0000
@@ -15011,6 +15011,33 @@
 target system.  If it is not set, the target will use a default
 filename (e.g.@: the last program run).
 
+@item set remote interrupt-sequence
+@cindex interrupt remote programs
+@cindex select Ctrl-C, BREAK or SysRq-g
+Allow the user to specify what sequence @value{GDBN} sends to the remote target
+when you type @samp{Ctrl-c} to interrupt the program running
+on the remote target.  Although @samp{Ctrl-C} is usually
+what remote systems expect (this is the default, here), it is
+sometimes preferable to send a @code{BREAK}.  When debugging the Linux kernel,
+a @code{BREAK} followed by @code{g}, which is
+Magic SysRq g is required in order to interrupt the execution.
+
+@item show interrupt-sequence
+Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK} followed by @code{g}
+is sent by @value{GDBN} to interrupt the remote program.
+@code{BREAK} followed by @code{g} is also known as Magic SysRq.
+
+@item set remote interrupt-on-connect
+@cindex send interrupt-sequence on start
+Specify whether interrupt_sequence is sent
+to remote target when @value{GDBN} connects to it.  This is mostly needed when you debug
+Linux kernel.  Linux kernel expects @code{BREAK} followed by @code{g} which is Magic SysRq
+in order to connect @value{GDBN}.
+
+@item show interrupt-on-connect
+Show whether interrupt-sequence is sent
+to remote target when @value{GDBN} connects to it.
+
 @kindex set tcp
 @kindex show tcp
 @item set tcp auto-retry on
@@ -29817,9 +29844,9 @@
 @cindex interrupts (remote protocol)
 
 When a program on the remote target is running, @value{GDBN} may
-attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
-control of which is specified via @value{GDBN}'s @samp{remotebreak}
-setting (@pxref{set remotebreak}).
+attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
+a @code{BREAK} followed by @code{g},
+control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
 
 The precise meaning of @code{BREAK} is defined by the transport
 mechanism and may, in fact, be undefined.  @value{GDBN} does not
@@ -29836,6 +29863,11 @@
 (@pxref{X packet}), used for binary downloads, may include an unescaped
 @code{0x03} as part of its packet.
 
+@code{BREAK} followed by @code{g} is also known as Magic SysRq and is
+@code{BREAK} and @code{g}.
+When Linux kernel receives this sequence from serial port,
+it stops execution and connects to gdb.
+
 Stubs are not required to recognize these interrupt mechanisms and the
 precise meaning associated with receipt of the interrupt is
 implementation defined.  If the target supports debugging of multiple