RE: symbolic debug of loadable modules with kgdb light

Caz Yokoyama
2009-08-07T04:06:17Z

[-- 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. */