Commit Graph

33 Commits

Author SHA1 Message Date
Matthew D Fleming
3a5d36716f Modify kdb_trap() so that it re-calls the dbbe_trap function as long as
the debugger back-end has changed.  This means that switching from ddb
to gdb no longer requires a "step" which can be dangerous on an
already-crashed kernel.

Also add a capability to get from the gdb back-end back to ddb, by
typing ^C in the console window.

While here, simplify kdb_sysctl_available() by using
sbuf_new_for_sysctl(), and use strlcpy() instead of strncpy() since the
strlcpy semantic is desired.

MFC after:	1 month
2011-02-18 22:25:11 +00:00
Andriy Gapon
10b2a365a0 debug.kdb.stop_cpus sysctl: hint that this is also a tunable
MFC after:	1 week
2010-09-30 16:47:01 +00:00
Andriy Gapon
61548876b1 kdb_backtrace: use stack_print_ddb instead of stack_print
This is a followup to r212964.
stack_print call chain obtains linker sx lock and thus potentially may
lead to a deadlock depending on a kind of a panic.
stack_print_ddb doesn't acquire any locks and it doesn't use any
facilities of ddb backend.
Using stack_print_ddb outside of DDB ifdef required taking a number of
helper functions from under it as well.

It is a good idea to rename linker_ddb_* and stack_*_ddb functions to
have 'unlocked' component in their name instead of 'ddb', because those
functions do not use any DDB services, but instead they provide unlocked
access to linker symbol information.  The latter was previously needed
only for DDB, hence the 'ddb' name component.

Alternative is to ditch unlocked versions altogether after implementing
proper panic handling:
1. stop other cpus upon a panic
2. make all non-spinlock lock operations (mutex, sx, rwlock) be a no-op
   when panicstr != NULL

Suggested by:	mdf
Discussed with:	attilio
MFC after:	2 weeks
2010-09-22 06:45:07 +00:00
Andriy Gapon
088acbb312 kdb_backtrace: stack(9)-based code to print backtrace without any backend
The idea is to add KDB and KDB_TRACE options to GENERIC kernels on
stable branches, so that at least the minimal information is produced
for non-specific panics like traps on page faults.
The GENERICs in stable branches seem to already include STACK option.

Reviewed by:	attilio
MFC after:	2 weeks
2010-09-21 15:07:44 +00:00
Andriy Gapon
1bdfff2252 fix a few cases where a string is passed via format argument instead of
via %s

Most of the cases looked harmless, but this is done for the sake of
correctness.  In one case it even allowed to drop an intermediate buffer.

Found by:	clang
MFC after:	2 week
2010-06-11 19:27:21 +00:00
Attilio Rao
dc6fbf6545 * Completely Remove the option STOP_NMI from the kernel. This option
has proven to have a good effect when entering KDB by using a NMI,
but it completely violates all the good rules about interrupts
disabled while holding a spinlock in other occasions.  This can be the
cause of deadlocks on events where a normal IPI_STOP is expected.
* Adds an new IPI called IPI_STOP_HARD on all the supported architectures.
This IPI is responsible for sending a stop message among CPUs using a
privileged channel when disponible. In other cases it just does match a
normal IPI_STOP.
Right now the IPI_STOP_HARD functionality uses a NMI on ia32 and amd64
architectures, while on the other has a normal IPI_STOP effect. It is
responsibility of maintainers to eventually implement an hard stop
when necessary and possible.
* Use the new IPI facility in order to implement a new userend SMP kernel
function called stop_cpus_hard(). That is specular to stop_cpu() but
it does use the privileged channel for the stopping facility.
* Let KDB use the newly introduced function stop_cpus_hard() and leave
stop_cpus() for all the other cases
* Disable interrupts on CPU0 when starting the process of APs suspension.
* Style cleanup and comments adding

This patch should fix the reboot/shutdown deadlocks many users are
constantly reporting on mailing lists.

Please don't forget to update your config file with the STOP_NMI
option removal

Reviewed by:	jhb
Tested by:	pho, bz, rink
Approved by:	re (kib)
2009-08-13 17:09:45 +00:00
Warner Losh
7cddab635b Spell NULL properly, use (void) rather than () for functions with no
parameters.  Mark two items as static that aren't used elsewhere...
2009-05-09 19:08:22 +00:00
Peter Wemm
43d7128c14 Expand kdb_alt_break a little, most commonly used with the option
ALT_BREAK_TO_DEBUGGER.  In addition to "Enter ~ ctrl-B" (to enter the
debugger), there is now "Enter ~ ctrl-P" (force panic) and
"Enter ~ ctrl-R" (request clean reboot, ala ctrl-alt-del on syscons).

We've used variations of this at work.  The force panic sequence is
best used with KDB_UNATTENDED for when you just want it to dump and
get on with it.

The reboot request is a safer way of getting into single user than
a power cycle.  eg: you've hosed the ability to log in (pam, rtld, etc).
It gives init the reboot signal, which causes an orderly reboot.

I've taken my best guess at what the !x86 and non-sio code changes
should be.

This also makes sio release its spinlock before calling KDB/DDB.
2008-05-04 23:29:38 +00:00
Robert Watson
3de213cc00 Add a new 'why' argument to kdb_enter(), and a set of constants to use
for that argument.  This will allow DDB to detect the broad category of
reason why the debugger has been entered, which it can use for the
purposes of deciding which DDB script to run.

Assign approximate why values to all current consumers of the
kdb_enter() interface.
2007-12-25 17:52:02 +00:00
Jeff Roberson
b61ce5b0e6 - Move all of the PS_ flags into either p_flag or td_flags.
- p_sflag was mostly protected by PROC_LOCK rather than the PROC_SLOCK or
   previously the sched_lock.  These bugs have existed for some time.
 - Allow swapout to try each thread in a process individually and then
   swapin the whole process if any of these fail.  This allows us to move
   most scheduler related swap flags into td_flags.
 - Keep ki_sflag for backwards compat but change all in source tools to
   use the new and more correct location of P_INMEM.

Reported by:	pho
Reviewed by:	attilio, kib
Approved by:	re (kensmith)
2007-09-17 05:31:39 +00:00
Yaroslav Tykhiy
42ccd54fec Add a funny sysctl: debug.kdb.trap_code .
It is similar to debug.kdb.trap, except for it tries to cause a page fault
via a call to an invalid pointer.  This can highlight differences between
a fault on data access vs. a fault on code call some CPUs might have.

This appeared as a test for a work \
Sponsored by: RiNet (Cronyx Plus LLC)
2006-06-18 12:27:59 +00:00
Ed Maste
374875fa56 Add a description for sysctl -d. 2006-06-17 02:58:18 +00:00
Marcel Moolenaar
39eb1d1263 Increment kdb_active after we stopped the other CPUs and decrement
kdb_active before we restart them. This avoids false positives on
restarted CPUs when they test for kdb_active while kdb_trap() is
still finishing up.
2006-04-04 00:40:20 +00:00
Marcel Moolenaar
bfcdefd8aa Eliminate HAVE_STOPPEDPCBS. On ia64 the PCPU holds a pointer to the
PCB in which the context of stopped CPUs is stored. To access this
PCB from KDB, we introduce a new define, called KDB_STOPPEDPCB. The
definition, when present, lives in <machine/kdb.h> and abstracts
where MD code saves the context. Define KDB_STOPPEDPCB on i386,
amd64, alpha and sparc64 in accordance to previous code.
2006-04-03 22:51:47 +00:00
Marcel Moolenaar
5991a4f811 In kdb_trap(), change the type of the local variable 'intr' from int
to register_t, as intr_disable() returns the latter and register_t
may be wider than int.

Pointed out by: marius@
2006-04-03 20:55:52 +00:00
Marcel Moolenaar
2fae8f5aed Replace critical_enter() and critical_exit() in kdb_trap() with
intr_disable() and intr_restore() resp. Previously, critical
regions would have interrupts disabled, but that was changed.
Consequently, the debugger could run with interrupts enabled.
This could cause problems for the low-level console code where
received characters would trigger an interrupt that causes
the interrupt handler to read the character instead of the
cngetc() function.
2006-04-03 17:48:09 +00:00
John Baldwin
091e8307d0 Add stoppcbs[] arrays on Alpha and sparc64 and have each CPU save its
current context in the IPI_STOP handler so that we can get accurate stack
traces of threads on other CPUs on these two archs like we do now on i386
and amd64.

Tested on:	alpha, sparc64
2005-11-03 21:08:20 +00:00
Peter Wemm
40c9966a37 Commit something we found useful at work at one point. Add sysctls for
debug.kdb.panic and debug.kdb.trap alongside the existing debug.kdb.enter
sysctl.  'panic' causes a panic, and 'trap' causes a page fault.  We used
these to ensure that crash dumps succeed from those two common failure
modes.  This avoids the need for creating a 'panic' kld module.
2005-10-26 22:40:07 +00:00
John Baldwin
58553b9925 Rename the KDB_STOP_NMI kernel option to STOP_NMI and make it apply to all
IPI_STOP IPIs.
- Change the i386 and amd64 MD IPI code to send an NMI if STOP_NMI is
  enabled if an attempt is made to send an IPI_STOP IPI.  If the kernel
  option is enabled, there is also a sysctl to change the behavior at
  runtime (debug.stop_cpus_with_nmi which defaults to enabled).  This
  includes removing stop_cpus_nmi() and making ipi_nmi_selected() a
  private function for i386 and amd64.
- Fix ipi_all(), ipi_all_but_self(), and ipi_self() on i386 and amd64 to
  properly handle bitmapped IPIs as well as IPI_STOP IPIs when STOP_NMI is
  enabled.
- Fix ipi_nmi_handler() to execute the restart function on the first CPU
  that is restarted making use of atomic_readandclear() rather than
  assuming that the BSP is always included in the set of restarted CPUs.
  Also, the NMI handler didn't clear the function pointer meaning that
  subsequent stop and restarts could execute the function again.
- Define a new macro HAVE_STOPPEDPCBS on i386 and amd64 to control the use
  of stoppedpcbs[] and always enable it for i386 and amd64 instead of
  being dependent on KDB_STOP_NMI.  It works fine in both the NMI and
  non-NMI cases.
2005-10-24 21:04:19 +00:00
John Baldwin
6b1e0d75b0 - Various small whitespace and style nits.
- Use PCPU_GET(cpumask) in preference to 1 << PCPU_GET(cpuid) in a few
  places.
2005-10-24 20:31:04 +00:00
Robert Watson
667285c4e3 If KDB_STOP_NMI is compiled into the kernel, default
debug.kdb.stop_cpus_with_nmi to 1 rather than 0.

MFC after:	3 days
2005-09-27 21:12:05 +00:00
Peter Wemm
f0c6706de9 Move the KDB_STOP_NMI option from opt_global.h to opt_kdb.h
Approved by:	re
2005-06-29 23:23:16 +00:00
Doug White
fdc9713bf7 Implement an alternate method to stop CPUs when entering DDB. Normally we use
a regular IPI vector, but this vector is blocked when interrupts are disabled.
With "options KDB_STOP_NMI" and debug.kdb.stop_cpus_with_nmi set, KDB will
send an NMI to each CPU instead. The code also has a context-stuffing
feature which helps ddb extract the state of processes running on the
stopped CPUs.

KDB_STOP_NMI is only useful with SMP and complains if SMP is not defined.
This feature only applies to i386 and amd64 at the moment, but could be
used on other architectures with the appropriate MD bits.

Submitted by:	ups
2005-04-30 20:01:00 +00:00
Warner Losh
9454b2d864 /* -> /*- for copyright notices, minor format tweaks as necessary 2005-01-06 23:35:40 +00:00
Stephan Uphoff
f742a1edcd Zero terminate empty sting in kdb_sysctl_available.
Approved by:    sam (mentor)
MFC after: 1 week
2004-10-21 01:11:25 +00:00
Marcel Moolenaar
e6aa723212 Fix a bug introduced in the previous commit: kdb_cpu_trap() gets to
the trapframe via kdb_frame, but kdb_frame was not initialized until
after the call to kdb_cpu_trap(). Ergo: kdb_cpu_trap() was moved too
far up.

Pointy hat: marcel
2004-09-26 06:48:59 +00:00
Marcel Moolenaar
ddf4122592 Move makectx() after kdb_cpu_trap(), so the PCB will have possible MD
corrections made to the trapframe. This is more logical.
2004-09-17 22:27:23 +00:00
Robert Watson
d963815baf Make debug.kdb.stop_cpus also a TUNABLE() so it can be set prior to boot
to help debug early nasty hangs.
2004-08-22 15:10:52 +00:00
Robert Watson
d8939d82cb Add a new sysctl, debug.kdb.stop_cpus, which controls whether or not we
attempt to IPI other cpus when entering the debugger in order to stop
them while in the debugger.  The default remains to issue the stop;
however, that can result in a hang if another cpu has interrupts disabled
and is spinning, since the IPI won't be received and the KDB will wait
indefinitely.  We probably need to add a timeout, but this is a useful
stopgap in the mean time.

Reviewed by:	marcel
2004-08-15 02:06:27 +00:00
Marcel Moolenaar
3d4f313695 Add kdb_thr_from_pid(), which given a PID returns the first thread
in the process. This is useful when working from or with a process.
2004-07-21 04:49:48 +00:00
Marcel Moolenaar
3bcd2440db Make kdb_dbbe_select() available as an interface function. This allows
changing the backend from outside the KDB frontend. For example from
within a backend. Rewrite kdb_sysctl_current to make use of this
function as well.
2004-07-12 01:15:55 +00:00
Marcel Moolenaar
a8bfba1a27 Fix braino: Make sure there is a current backend before we return its
name in the debug.kdb.current sysctl. All other dereferences are
properly guarded, but this one was overlooked.

Reported by: Morten Rodal (morten at rodal dot no)
2004-07-11 15:22:43 +00:00
Marcel Moolenaar
cbc174356c Introduce the KDB debugger frontend. The frontend provides a framework
in which multiple (presumably different) debugger backends can be
configured and which provides basic services to those backends.
Besides providing services to backends, it also serves as the single
point of contact for any and all code that wants to make use of the
debugger functions, such as entering the debugger or handling of the
alternate break sequence. For this purpose, the frontend has been
made non-optional.
All debugger requests are forwarded or handed over to the current
backend, if applicable. Selection of the current backend is done by
the debug.kdb.current sysctl. A list of configured backends can be
obtained with the debug.kdb.available sysctl. One can enter the
debugger by writing to the debug.kdb.enter sysctl.
2004-07-10 18:40:12 +00:00