Cleanups
Clean up compile warnings in kgdboc.c and x86/kernel/kgdb.c
Add module event hooks for simplified debugging with gdb
Fixes
Fix kdb to stop paging with 'q' on bta and dmesg
Fix for data that scrolls off the vga console due to line wrapping
when using the kdb pager
New
The debug core registers for kernel module events which allows a
kernel aware gdb to automatically load symbols and break on entry
to a kernel module
Allow kgdboc=kdb to setup kdb on the vga console
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Merge tag 'for_linus-3.7' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/kgdb
Pull KGDB/KDB fixes and cleanups from Jason Wessel:
"Cleanups
- Clean up compile warnings in kgdboc.c and x86/kernel/kgdb.c
- Add module event hooks for simplified debugging with gdb
Fixes
- Fix kdb to stop paging with 'q' on bta and dmesg
- Fix for data that scrolls off the vga console due to line wrapping
when using the kdb pager
New
- The debug core registers for kernel module events which allows a
kernel aware gdb to automatically load symbols and break on entry
to a kernel module
- Allow kgdboc=kdb to setup kdb on the vga console"
* tag 'for_linus-3.7' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/kgdb:
tty/console: fix warnings in drivers/tty/serial/kgdboc.c
kdb,vt_console: Fix missed data due to pager overruns
kdb: Fix dmesg/bta scroll to quit with 'q'
kgdboc: Accept either kbd or kdb to activate the vga + keyboard kdb shell
kgdb,x86: fix warning about unused variable
mips,kgdb: fix recursive page fault with CONFIG_KPROBES
kgdb: Add module event hooks
Allow gdb to auto load kernel modules when it is attached,
which makes it trivially easy to debug module init functions
or pre-set breakpoints in a kernel module that has not loaded yet.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The new arch callback should manage NMIs that usually cause KGDB to
enter. That is, not all NMIs should be enabled/disabled, but only
those that issue kgdb_handle_exception().
We must mask it as serial-line interrupt can be used as an NMI, so
if the original KGDB-entry cause was say a breakpoint, then every
input to KDB console will cause KGDB to reenter, which we don't want.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
3.4: Fix an an Smatch warning that appeared in the 3.4 merge window
3.0: Fix kgdb test suite with SMP for all archs without HW single stepping
2.6.36: Fix kgdb sw breakpoints with CONFIG_DEBUG_RODATA=y limitations on x86
2.6.26: Fix oops on kgdb test suite with CONFIG_DEBUG_RODATA
Fix kgdb test suite with SMP for all archs with HW single stepping
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Merge tag 'for_linus-3.4-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/kgdb
Pull KGDB/KDB regression fixes from Jason Wessel:
- Fix a Smatch warning that appeared in the 3.4 merge window
- Fix kgdb test suite with SMP for all archs without HW single stepping
- Fix kgdb sw breakpoints with CONFIG_DEBUG_RODATA=y limitations on x86
- Fix oops on kgdb test suite with CONFIG_DEBUG_RODATA
- Fix kgdb test suite with SMP for all archs with HW single stepping
* tag 'for_linus-3.4-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/kgdb:
x86,kgdb: Fix DEBUG_RODATA limitation using text_poke()
kgdb,debug_core: pass the breakpoint struct instead of address and memory
kgdbts: (2 of 2) fix single step awareness to work correctly with SMP
kgdbts: (1 of 2) fix single step awareness to work correctly with SMP
kgdbts: Fix kernel oops with CONFIG_DEBUG_RODATA
kdb: Fix smatch warning on dbg_io_ops->is_console
There is extra state information that needs to be exposed in the
kgdb_bpt structure for tracking how a breakpoint was installed. The
debug_core only uses the the probe_kernel_write() to install
breakpoints, but this is not enough for all the archs. Some arch such
as x86 need to use text_poke() in order to install a breakpoint into a
read only page.
Passing the kgdb_bpt structure to kgdb_arch_set_breakpoint() and
kgdb_arch_remove_breakpoint() allows other archs to set the type
variable which indicates how the breakpoint was installed.
Cc: stable@vger.kernel.org # >= 2.6.36
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
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Merge tag 'split-asm_system_h-for-linus-20120328' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-asm_system
Pull "Disintegrate and delete asm/system.h" from David Howells:
"Here are a bunch of patches to disintegrate asm/system.h into a set of
separate bits to relieve the problem of circular inclusion
dependencies.
I've built all the working defconfigs from all the arches that I can
and made sure that they don't break.
The reason for these patches is that I recently encountered a circular
dependency problem that came about when I produced some patches to
optimise get_order() by rewriting it to use ilog2().
This uses bitops - and on the SH arch asm/bitops.h drags in
asm-generic/get_order.h by a circuituous route involving asm/system.h.
The main difficulty seems to be asm/system.h. It holds a number of
low level bits with no/few dependencies that are commonly used (eg.
memory barriers) and a number of bits with more dependencies that
aren't used in many places (eg. switch_to()).
These patches break asm/system.h up into the following core pieces:
(1) asm/barrier.h
Move memory barriers here. This already done for MIPS and Alpha.
(2) asm/switch_to.h
Move switch_to() and related stuff here.
(3) asm/exec.h
Move arch_align_stack() here. Other process execution related bits
could perhaps go here from asm/processor.h.
(4) asm/cmpxchg.h
Move xchg() and cmpxchg() here as they're full word atomic ops and
frequently used by atomic_xchg() and atomic_cmpxchg().
(5) asm/bug.h
Move die() and related bits.
(6) asm/auxvec.h
Move AT_VECTOR_SIZE_ARCH here.
Other arch headers are created as needed on a per-arch basis."
Fixed up some conflicts from other header file cleanups and moving code
around that has happened in the meantime, so David's testing is somewhat
weakened by that. We'll find out anything that got broken and fix it..
* tag 'split-asm_system_h-for-linus-20120328' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-asm_system: (38 commits)
Delete all instances of asm/system.h
Remove all #inclusions of asm/system.h
Add #includes needed to permit the removal of asm/system.h
Move all declarations of free_initmem() to linux/mm.h
Disintegrate asm/system.h for OpenRISC
Split arch_align_stack() out from asm-generic/system.h
Split the switch_to() wrapper out of asm-generic/system.h
Move the asm-generic/system.h xchg() implementation to asm-generic/cmpxchg.h
Create asm-generic/barrier.h
Make asm-generic/cmpxchg.h #include asm-generic/cmpxchg-local.h
Disintegrate asm/system.h for Xtensa
Disintegrate asm/system.h for Unicore32 [based on ver #3, changed by gxt]
Disintegrate asm/system.h for Tile
Disintegrate asm/system.h for Sparc
Disintegrate asm/system.h for SH
Disintegrate asm/system.h for Score
Disintegrate asm/system.h for S390
Disintegrate asm/system.h for PowerPC
Disintegrate asm/system.h for PA-RISC
Disintegrate asm/system.h for MN10300
...
Remove all #inclusions of asm/system.h preparatory to splitting and killing
it. Performed with the following command:
perl -p -i -e 's!^#\s*include\s*<asm/system[.]h>.*\n!!' `grep -Irl '^#\s*include\s*<asm/system[.]h>' *`
Signed-off-by: David Howells <dhowells@redhat.com>
Sometimes it is desirable to stop the kernel debugger before allowing
a system to reboot either with kdb or kgdb. This patch adds the
ability to turn the reboot notifier on and off or enter the debugger
and stop kernel execution before rebooting.
It is possible to change the setting after booting the kernel with the
following:
echo 1 > /sys/module/debug_core/parameters/kgdbreboot
It is also possible to change this setting using kdb / kgdb to
manipulate the variable directly.
Using KDB:
mm kgdbreboot 1
Using gdb:
set kgdbreboot=1
Reported-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The gdbstub and kdb should get detached if the system is rebooting.
Calling gdbstub_exit() will set the proper debug core state and send a
message to any debugger that is connected to correctly detach.
An attached debugger will receive the exit code from
include/linux/reboot.h based on SYS_HALT, SYS_REBOOT, etc...
Reported-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
This allows us to move duplicated code in <asm/atomic.h>
(atomic_inc_not_zero() for now) to <linux/atomic.h>
Signed-off-by: Arun Sharma <asharma@fb.com>
Reviewed-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Miller <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The kgdb_disable_hw_debug() was an architecture specific function for
disabling all hardware breakpoints on a per cpu basis when entering
the debug core.
This patch will remove the weak function kdbg_disable_hw_debug() and
change it into a call back which lives with the rest of hw breakpoint
call backs in struct kgdb_arch.
Signed-off-by: Dongdong Deng <dongdong.deng@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The kdb shell needs to enforce switching back to the original CPU that
took the exception before restoring normal kernel execution. Resuming
from a different CPU than what took the original exception will cause
problems with spin locks that are freed from the a different processor
than had taken the lock.
The special logic in dbg_cpu_switch() can go away entirely with
because the state of what cpus want to be masters or slaves will
remain unchanged between entry and exit of the debug_core exception
context.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
For quite some time there have been problems with memory barriers and
various races with NMI on multi processor systems using the kernel
debugger. The algorithm for entering the kernel debug core and
resuming kernel execution was racy and had several known edge case
problems with attempting to debug something on a heavily loaded system
using breakpoints that are hit repeatedly and quickly.
The prior "locking" design entry worked as follows:
* The atomic counter kgdb_active was used with atomic exchange in
order to elect a master cpu out of all the cpus that may have
taken a debug exception.
* The master cpu increments all elements of passive_cpu_wait[].
* The master cpu issues the round up cpus message.
* Each "slave cpu" that enters the debug core increments its own
element in cpu_in_kgdb[].
* Each "slave cpu" spins on passive_cpu_wait[] until it becomes 0.
* The master cpu debugs the system.
The new scheme removes the two arrays of atomic counters and replaces
them with 2 single counters. One counter is used to count the number
of cpus waiting to become a master cpu (because one or more hit an
exception). The second counter is use to indicate how many cpus have
entered as slave cpus.
The new entry logic works as follows:
* One or more cpus enters via kgdb_handle_exception() and increments
the masters_in_kgdb. Each cpu attempts to get the spin lock called
dbg_master_lock.
* The master cpu sets kgdb_active to the current cpu.
* The master cpu takes the spinlock dbg_slave_lock.
* The master cpu asks to round up all the other cpus.
* Each slave cpu that is not already in kgdb_handle_exception()
will enter and increment slaves_in_kgdb. Each slave will now spin
try_locking on dbg_slave_lock.
* The master cpu waits for the sum of masters_in_kgdb and slaves_in_kgdb
to be equal to the sum of the online cpus.
* The master cpu debugs the system.
In the new design the kgdb_active can only be changed while holding
dbg_master_lock. Stress testing has not turned up any further
entry/exit races that existed in the prior locking design. The prior
locking design suffered from atomic variables not being truly atomic
(in the capacity as used by kgdb) along with memory barrier races.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Dongdong Deng <dongdong.deng@windriver.com>
The slave cpus do not have the hw breakpoints disabled upon entry to
the debug_core and as a result could cause unrecoverable recursive
faults on badly placed breakpoints, or get out of sync with the arch
specific hw breakpoint operations.
This patch addresses the problem by invoking kgdb_disable_hw_debug()
earlier in kgdb_enter_cpu for each cpu that enters the debug core.
The hw breakpoint dis/enable flow should be:
master_debug_cpu slave_debug_cpu
\ /
kgdb_cpu_enter
|
kgdb_disable_hw_debug --> uninstall pre-enabled hw_breakpoint
|
do add/rm dis/enable operates to hw_breakpoints on master_debug_cpu..
|
correct_hw_break --> correct/install the enabled hw_breakpoint
|
leave_kgdb
Signed-off-by: Dongdong Deng <dongdong.deng@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
When returning from the kernel debugger reset the rcu jiffies_stall
value to prevent the rcu stall detector from sending NMI events which
invoke a stack dump for each cpu in the system.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Move the various clock and watch dog syncs to a single function in
advance of adding another sync for the rcu stall detector.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Noone is using tty argument so let's get rid of it.
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Acked-by: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/linux-2.6-kgdb:
debug_core,kdb: fix crash when arch does not have single step
kgdb,x86: use macro HBP_NUM to replace magic number 4
kgdb,mips: remove unused kgdb_cpu_doing_single_step operations
mm,kdb,kgdb: Add a debug reference for the kdb kmap usage
KGDB: Remove set but unused newPC
ftrace,kdb: Allow dumping a specific cpu's buffer with ftdump
ftrace,kdb: Extend kdb to be able to dump the ftrace buffer
kgdb,powerpc: Replace hardcoded offset by BREAK_INSTR_SIZE
arm,kgdb: Add ability to trap into debugger on notify_die
gdbstub: do not directly use dbg_reg_def[] in gdb_cmd_reg_set()
gdbstub: Implement gdbserial 'p' and 'P' packets
kgdb,arm: Individual register get/set for arm
kgdb,mips: Individual register get/set for mips
kgdb,x86: Individual register get/set for x86
kgdb,kdb: individual register set and and get API
gdbstub: Optimize kgdb's "thread:" response for the gdb serial protocol
kgdb: remove custom hex_to_bin()implementation
When an arch such as mips and microblaze does not implement either HW
or software single stepping the debug core should re-enter kdb. The
kdb code will properly ignore the single step operation. Attempting
to single step the kernel without software or hardware support causes
unpredictable kernel crashes.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Immediately following an exit from the kdb shell the kgdb_connected
variable should be set to zero, unless there are breakpoints planted.
If the kgdb_connected variable is not zeroed out with kdb, it is
impossible to turn off kdb.
This patch is merely a work around for now, the real fix will check
for the breakpoints.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
pavel@suse.cz no longer works, replace it with working address.
Signed-off-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
The kernel debugger can operate well before mm_init(), but the x86
hardware breakpoint code which uses the perf api requires that the
kernel allocators are initialized.
This means the kernel debug core needs to provide an optional arch
specific call back to allow the initialization functions to run after
the kernel has been further initialized.
The kdb shell already had a similar restriction with an early
initialization and late initialization. The kdb_init() was moved into
the debug core's version of the late init which is called
dbg_late_init();
CC: kgdb-bugreport@lists.sourceforge.net
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
It is highly desirable to trap into kdb on panic. The debug core will
attempt to register as the first in line for the panic notifier.
CC: Ingo Molnar <mingo@elte.hu>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Some kgdb I/O modules require the ability to create a breakpoint
tasklet, such as kgdboc and external modules such as kgdboe. The
breakpoint tasklet is used as an asynchronous entry point into the
debugger which will have a different function scope than the current
execution path where it might not be safe to have an inline
breakpoint. This is true of some of the kgdb I/O drivers which share
code with kgdb and rest of the kernel users.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The only way the debugger can handle a trap in inside rcu_lock,
notify_die, or atomic_notifier_call_chain without a triple fault is
to have a low level "first opportunity handler" in the int3 exception
handler.
Generally this will be something the vast majority of folks will not
need, but for those who need it, it is added as a kernel .config
option called KGDB_LOW_LEVEL_TRAP.
CC: Ingo Molnar <mingo@elte.hu>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: H. Peter Anvin <hpa@zytor.com>
CC: x86@kernel.org
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Remove all the references to the kgdb_post_primary_code. This
function serves no useful purpose because you can obtain the same
information from the "struct kgdb_state *ks" from with in the
debugger, if for some reason you want the data.
Also remove the unintentional duplicate assignment for ks->ex_vector.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
One of the driving forces behind integrating another front end (kdb)
to the debug core is to allow front end commands to be accessible via
gdb's monitor command. It is true that you could write gdb macros to
get certain data, but you may want to just use gdb to access the
commands that are available in the kdb front end.
This patch implements the Rcmd gdb stub packet. In gdb you access
this with the "monitor" command. For instance you could type "monitor
help", "monitor lsmod" or "monitor ps A" etc...
There is no error checking or command restrictions on what you can and
cannot access at this point. Doing something like trying to set
breakpoints with the monitor command is going to cause nothing but
problems. Perhaps in the future only the commands that are actually
known to work with the gdb monitor command will be available.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The design of the kdb shell requires that every device that can
provide input to kdb have a polling routine that exits immediately if
there is no character available. This is required in order to get the
page scrolling mechanism working.
Changing the kernel debugger I/O API to require all polling character
routines to exit immediately if there is no data allows the kernel
debugger to process multiple input channels.
NO_POLL_CHAR will be the return code to the polling routine when ever
there is no character available.
CC: linux-serial@vger.kernel.org
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
These are the minimum changes to the kgdb core in order to enable an
API to connect a new front end (kdb) to the debug core.
This patch introduces the dbg_kdb_mode variable controls where the
user level I/O is routed. It will be routed to the gdbstub (kgdb) or
to the kdb front end which is a simple shell available over the kgdboc
connection.
You can switch back and forth between kdb or the gdb stub mode of
operation dynamically. From gdb stub mode you can blindly type
"$3#33", or from the kdb mode you can enter "kgdb" to switch to the
gdb stub.
The logic in the debug core depends on kdb to look for the typical gdb
connection sequences and return immediately with KGDB_PASS_EVENT if a
gdb serial command sequence is detected. That should allow a
reasonably seamless transition between kdb -> gdb without leaving the
kernel exception state. The two gdb serial queries that kdb is
responsible for detecting are the "?" and "qSupported" packets.
CC: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Martin Hicks <mort@sgi.com>
Split the former kernel/kgdb.c into debug_core.c which contains the
kernel debugger exception logic and to the gdbstub.c which contains
the logic for allowing gdb to talk to the debug core.
This also created a private include file called debug_core.h which
contains all the definitions to glue the debug_core to any other
debugger connections.
CC: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Move kgdb.c in preparation to separate the gdbstub from the debug
core and exception handling.
CC: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Linus Torvalds