RE: symbolic debug of loadable modules with kgdb light

[Caz Yokoyama <cazyokoyama@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 6137 bytes --]

This patch generalizes remotebreak. It becomes an enum string from a
Boolean. It may be "Ctrl-C", "BREAK" or "BREAK-g". When it is "BREAK-g", gdb
also sends BREAK g to connect to Linux kernel when it starts.

Index: gdb/remote.c
===================================================================
RCS file: /cvs/src/src/gdb/remote.c,v
retrieving revision 1.366
diff -c -r1.366 remote.c
*** gdb/remote.c	31 Jul 2009 22:15:15 -0000	1.366
--- gdb/remote.c	7 Aug 2009 03:50:30 -0000
***************
*** 546,558 ****
     this can go away.  */
  static int wait_forever_enabled_p = 1;
  
  
! /* 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 int remote_break;
  
  /* 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
--- 546,575 ----
     this can go away.  */
  static int wait_forever_enabled_p = 1;
  
+ /* This variable chooses whether to send a ^C, a break or a break g
+    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. For interrupting Linux kernel, a break and g is
+    expected which is Magic SysReq g.  */
+ const char bs_Crtl_C[] = "Ctrl-C";
+ const char bs_BREAK[] = "BREAK";
+ const char bs_BREAK_g[] = "BREAK-g";
+ static const char *remotebreak_enum[] = {
+   bs_Crtl_C,
+   bs_BREAK,
+   bs_BREAK_g,
+   NULL
+ };
+ const char *remotebreak_string = bs_Crtl_C;
  
! static void show_remotebreak(struct ui_file *file, int from_tty,
! 			      struct cmd_list_element *c,
! 			      const char *value)
! {
!   fprintf_unfiltered (file, "remote systems expect %s to be
interrupted\n",
! 		      remotebreak_string);
! }
  
  /* 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
***************
*** 2601,2606 ****
--- 2618,2629 ----
    /* Ack any packet which the remote side has already sent.  */
    serial_write (remote_desc, "+", 1);
  
+   /* send break sequence on debugging Linux kernel */
+   if (remotebreak_string == bs_BREAK_g) {
+     serial_send_break (remote_desc);
+     serial_write (remote_desc, "g", 1);
+   }
+ 
    /* 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.  */
***************
*** 4011,4022 ****
    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);
  }
  
  /* This is the generic stop called via the target vector. When a target
--- 4034,4048 ----
    if (rs->cached_wait_status)
      return;
  
!   /* Send ^C, a break or a break g, depending on user preference.  */
!   if (remotebreak_string == bs_Crtl_C) {
!       serial_write (remote_desc, "\003", 1);
!   } else if (remotebreak_string == bs_BREAK) {
!       serial_send_break (remote_desc);
!   } else if (remotebreak_string == bs_BREAK_g) {
      serial_send_break (remote_desc);
!     serial_write (remote_desc, "g", 1);
!   }
  }
  
  /* This is the generic stop called via the target vector. When a target
***************
*** 9051,9062 ****
  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."), _("\
! 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.  */
! 			   &setlist, &showlist);
  
    /* Install commands for configuring memory read/write packets.  */
  
--- 9077,9088 ----
  terminating `#' character and checksum."),
  	   &maintenancelist);
  
!   add_setshow_enum_cmd ("remotebreak", class_support,
! 			remotebreak_enum, &remotebreak_string, _("\
! Set remote break sequence."), _("\
! Show remote break sequence."), NULL,
! 			NULL, show_remotebreak,
! 			&setlist, &showlist);
  
    /* Install commands for configuring memory read/write packets.  */
  
-caz

-----Original Message-----
From: Caz Yokoyama [mailto:caz@caztech.com] 
Sent: Friday, May 15, 2009 3:26 PM
To: 'Michael Snyder'
Cc: 'Daniel Jacobowitz'; 'Pedro Alves'; 'gdb-patches@sourceware.org';
'tromey@redhat.com'; 'Joel Brobecker'
Subject: RE: symbolic debug of loadable modules with kgdb light

I have no objection regarding generic way of sending a BREAK. However, I had
two reasons to introduce linux-kgdb.
1) Someone suggested me the same several months ago. Nobody implemented.
2) I need some way to specify debugging linux kernel by using kgdb for
symbolic debug of loadable modules.
-caz

-----Original Message-----
From: Michael Snyder [mailto:msnyder@vmware.com] 
Sent: Friday, May 15, 2009 3:14 PM
To: Caz Yokoyama
Cc: 'Daniel Jacobowitz'; 'Pedro Alves'; gdb-patches@sourceware.org;
tromey@redhat.com; 'Joel Brobecker'
Subject: Re: symbolic debug of loadable modules with kgdb light

I think we need a generic way to send a BREAK
(whatever that may mean) to the target from the
command line.  Like maybe a "BREAK" command.

Caz Yokoyama wrote:
> Yes, that is correct.
> -caz
> -----Original Message-----
> From: Daniel Jacobowitz [mailto:drow@false.org] 
> Sent: Friday, May 15, 2009 2:34 PM
> To: Pedro Alves
> Cc: gdb-patches@sourceware.org; Caz Yokoyama; tromey@redhat.com; 'Joel
> Brobecker'
> Subject: Re: symbolic debug of loadable modules with kgdb light
> 
> On Fri, May 15, 2009 at 10:23:57PM +0100, Pedro Alves wrote:
>> Sounds like you need to fix kgdb instead.  Why would it need
>> a 'g' on connection?
> 
> BREAK on a serial (or network maybe?) console is magic sysrq; this is
> sysrq-g, probably for debuG.
> 

[-- Attachment #2: remotebreak.patch --]
[-- Type: application/octet-stream, Size: 4407 bytes --]

Index: gdb/remote.c
===================================================================
RCS file: /cvs/src/src/gdb/remote.c,v
retrieving revision 1.366
diff -c -r1.366 remote.c
*** gdb/remote.c	31 Jul 2009 22:15:15 -0000	1.366
--- gdb/remote.c	7 Aug 2009 03:50:30 -0000
***************
*** 546,558 ****
     this can go away.  */
  static int wait_forever_enabled_p = 1;
  
  
! /* 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 int remote_break;
  
  /* 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
--- 546,575 ----
     this can go away.  */
  static int wait_forever_enabled_p = 1;
  
+ /* This variable chooses whether to send a ^C, a break or a break g
+    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. For interrupting Linux kernel, a break and g is
+    expected which is Magic SysReq g.  */
+ const char bs_Crtl_C[] = "Ctrl-C";
+ const char bs_BREAK[] = "BREAK";
+ const char bs_BREAK_g[] = "BREAK-g";
+ static const char *remotebreak_enum[] = {
+   bs_Crtl_C,
+   bs_BREAK,
+   bs_BREAK_g,
+   NULL
+ };
+ const char *remotebreak_string = bs_Crtl_C;
  
! static void show_remotebreak(struct ui_file *file, int from_tty,
! 			      struct cmd_list_element *c,
! 			      const char *value)
! {
!   fprintf_unfiltered (file, "remote systems expect %s to be interrupted\n",
! 		      remotebreak_string);
! }
  
  /* 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
***************
*** 2601,2606 ****
--- 2618,2629 ----
    /* Ack any packet which the remote side has already sent.  */
    serial_write (remote_desc, "+", 1);
  
+   /* send break sequence on debugging Linux kernel */
+   if (remotebreak_string == bs_BREAK_g) {
+     serial_send_break (remote_desc);
+     serial_write (remote_desc, "g", 1);
+   }
+ 
    /* 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.  */
***************
*** 4011,4022 ****
    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);
  }
  
  /* This is the generic stop called via the target vector. When a target
--- 4034,4048 ----
    if (rs->cached_wait_status)
      return;
  
!   /* Send ^C, a break or a break g, depending on user preference.  */
!   if (remotebreak_string == bs_Crtl_C) {
!       serial_write (remote_desc, "\003", 1);
!   } else if (remotebreak_string == bs_BREAK) {
!       serial_send_break (remote_desc);
!   } else if (remotebreak_string == bs_BREAK_g) {
      serial_send_break (remote_desc);
!     serial_write (remote_desc, "g", 1);
!   }
  }
  
  /* This is the generic stop called via the target vector. When a target
***************
*** 9051,9062 ****
  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."), _("\
! 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.  */
! 			   &setlist, &showlist);
  
    /* Install commands for configuring memory read/write packets.  */
  
--- 9077,9088 ----
  terminating `#' character and checksum."),
  	   &maintenancelist);
  
!   add_setshow_enum_cmd ("remotebreak", class_support,
! 			remotebreak_enum, &remotebreak_string, _("\
! Set remote break sequence."), _("\
! Show remote break sequence."), NULL,
! 			NULL, show_remotebreak,
! 			&setlist, &showlist);
  
    /* Install commands for configuring memory read/write packets.  */