Because it can take spinlocks.
Suggested by Mathieu Desnoyers
Cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Remove most of the special cases for the debug IST stack. This is a
follow on clean up patch, it requires the bug fix patch that adds
orig_ist.
Signed-off-by: Keith Owens <kaos@ocs.com.au>
Signed-off-by: Andi Kleen <ak@suse.de>
And replace all users with ordinary smp_processor_id. The function
was originally added to get some basic oops information out even
if the GS register was corrupted. However that didn't
work for some anymore because printk is needed to print the oops
and it uses smp_processor_id() already. Also GS register corruptions
are not particularly common anymore.
This also helps the Xen port which would otherwise need to
do this in a special way because it can't access the local APIC.
Cc: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Implement pause_on_oops() on x86_64.
AK: I redid the patch to do the oops_enter/exit in the existing
oops_begin()/end(). This makes it much shorter.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Right now the kernel on x86-64 has a 100% lazy fpu behavior: after *every*
context switch a trap is taken for the first FPU use to restore the FPU
context lazily. This is of course great for applications that have very
sporadic or no FPU use (since then you avoid doing the expensive
save/restore all the time). However for very frequent FPU users... you
take an extra trap every context switch.
The patch below adds a simple heuristic to this code: After 5 consecutive
context switches of FPU use, the lazy behavior is disabled and the context
gets restored every context switch. If the app indeed uses the FPU, the
trap is avoided. (the chance of the 6th time slice using FPU after the
previous 5 having done so are quite high obviously).
After 256 switches, this is reset and lazy behavior is returned (until
there are 5 consecutive ones again). The reason for this is to give apps
that do longer bursts of FPU use still the lazy behavior back after some
time.
[akpm@osdl.org: place new task_struct field next to jit_keyring to save space]
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
This unifies the standard backtracer and the new stacktrace
in memory backtracer. The standard one is converted to use callbacks
and then reimplement stacktrace using new callbacks.
The main advantage is that stacktrace can now use the new dwarf2 unwinder
and avoid false positives in many cases.
I kept it simple to make sure the standard backtracer stays reliable.
Cc: mingo@elte.hu
Signed-off-by: Andi Kleen <ak@suse.de>
Instead of hackish manual parsing
Requires earlier i386 patchkit, but also fixes i386 early_printk again.
I removed some obsolete really early parameters which didn't do anything useful.
Also made a few parameters that needed it early (mostly oops printing setup)
Also removed one panic check that wasn't visible without
early console anyways (the early console is now initialized after that
panic)
This cleans up a lot of code.
Signed-off-by: Andi Kleen <ak@suse.de>
IO-APIC or local APIC can only be disabled at runtime anyways and
Kconfig has forced these options on for a long time now.
The Kconfigs are kept only now for the benefit of the shared acpi
boot.c code.
Signed-off-by: Andi Kleen <ak@suse.de>
When a unknown NMI happened the panic would claim a NMI watchdog timeout.
Also it would check the variable set by nmi_watchdog=panic and panic then.
Fix up the panic message to be generic
Unconditionally panic on unknown NMI when panic on unknown nmi is enabled.
Noticed by Jan Beulich
Cc: jbeulich@novell.com
Signed-off-by: Andi Kleen <ak@suse.de>
Clean up some of the output messages on the nmi error paths to make more
sense when they are displayed. This is mainly a cosmetic fix and
shouldn't impact any normal code path.
Signed-off-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Andi Kleen <ak@suse.de>
To quote Alan Cox:
The default Linux behaviour on an NMI of either memory or unknown is to
continue operation. For many environments such as scientific computing
it is preferable that the box is taken out and the error dealt with than
an uncorrected parity/ECC error get propogated.
A small number of systems do generate NMI's for bizarre random reasons
such as power management so the default is unchanged. In other respects
the new proc/sys entry works like the existing panic controls already in
that directory.
This is separate to the edac support - EDAC allows supported chipsets to
handle ECC errors well, this change allows unsupported cases to at least
panic rather than cause problems further down the line.
Signed-off-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Andi Kleen <ak@suse.de>
This patch cleans up the NMI interrupt path. Instead of being gated by if
the 'nmi callback' is set, the interrupt handler now calls everyone who is
registered on the die_chain and additionally checks the nmi watchdog,
reseting it if enabled. This allows more subsystems to hook into the NMI if
they need to (without being block by set_nmi_callback).
Signed-off-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Andi Kleen <ak@suse.de>
The values in init_tss.ist[] can change when an IST event occurs. Save
the original IST values for checking stack addresses when debugging or
doing stack traces.
Signed-off-by: Keith Owens <kaos@ocs.com.au>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The unwinder fallback logic still had potential for falling through to
the legacy stack trace code without printing an indication (at once
serving as a separator) of this.
Further, the stack pointer retrieval for the fallback should be as
restrictive as possible (in order to avoid having the legacy stack
tracer try to access invalid memory). The patch tightens that, but
this could certainly be further improved.
Also making the call_trace command line option now conditional upon
CONFIG_STACK_UNWIND (as it's meaningless otherwise).
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Previously the message was "Fatal exception: panic_on_oops", as introduced
in a recent patch whith removed a somewhat dangerous call to ssleep() in
the panic_on_oops path. However, Paul Mackerras suggested that this was
somewhat confusing, leadind people to believe that it was panic_on_oops
that was the root cause of the fatal exception. On his suggestion, this
patch changes the message to simply "Fatal exception". A suitable oops
message should already have been displayed.
Signed-off-by: Simon Horman <horms@verge.net.au>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This patch is part of an effort to unify the panic_on_oops behaviour across
all architectures that implement it.
It was pointed out to me by Andi Kleen that if an oops has occured in
interrupt context, then calling sleep() in the oops path will only cause a
panic, and that it would be really better for it not to be in the path at
all.
This patch removes the ssleep() call and reworks the console message
accordinly. I have a slght concern that the resulting console message is
too long, feedback welcome.
For powerpc it also unifies the 32bit and 64bit behaviour.
Fror x86_64, this patch only updates the console message, as ssleep() is
already not present.
Signed-off-by: Horms <horms@verge.net.au>
Acked-by: Paul Mackerras <paulus@samba.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Andi Kleen <ak@muc.de>
Cc: Chris Zankel <chris@zankel.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The dwarf2 unwinder currently often gets stuck because a lot
of assembly code doesn't have proper dwarf2 annotiation yet.
This currently often happens with __down. Should fix this by
adding proper dwarf2 annotation to all inline assembly. However
until that's done we need a quick fix for 2.6.18 to avoid
incomplete backtraces.
So when this happens dump the rest of the stack with the old unwinder
instead of silently not dumping it. There was already a optional
"both" mode that dumped both, but that was too ugly.
I also clarified the headers for the different backtraces a bit.
Also add a clear error message for missing dwarf2
annotation that people can work on.
And I removed a dead variable left over from Ingo's changes.
Cc: mingo@elte.hu
Cc: jbeulich@novell.com
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
{un}register_die_notifier() is used by kdb... document this so that future
"remove dead export" rounds can skip this export.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Document stack frame nesting internals some more.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Beautify x86_64 stacktraces to be more readable.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Only exports for assembler files are left in x8664_ksyms.c
Originally inspired by a patch from Al Viro
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Defaulting to a value not evenly divisible by four makes little sense,
as four values are displayed per line (and hence the rest of the line
would otherwise be wasted).
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
If no unwinding is possible at all for a certain exception instance,
fall back to the old style call trace instead of not showing any trace
at all.
Also, allow setting the stack trace mode at the command line.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
These are the x86_64-specific pieces to enable reliable stack traces. The
only restriction with this is that it currently cannot unwind across the
interrupt->normal stack boundary, as that transition is lacking proper
annotation.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Early development of x86-64 Linux was in CVS, but that hasn't been
the case for a long time now. Remove the obsolete $Id$s.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Extends an earlier patch from John Blackwood to more exception handlers
that also run on the exception stacks.
Expand the use of preempt_conditional_{sti,cli} to all cases where
interrupts are to be re-enabled during exception handling while running
on an IST stack.
Based on original patch from Jan Beulich.
Cc: John Blackwood <john.blackwood@ccur.com>
Cc: jbeulich@novell.com
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Playing with NMI watchdog on x86_64, I discovered that it didn't
do what I expected. It always panic-ed, even when it didn't
happen from interrupt context. This patch solves that
problem for me. Also, in this case, do_exit() will be called
with interrupts disabled, I believe. Would it be wise to also
call local_irq_enable() after nmi_exit()?
[Yes I added it -AK]
Currently, on x86_64, any NMI watchdog timeout will cause a panic
because the irq count will always be set to be in an interrupt
when do_exit() is called from die_nmi(). If we add nmi_exit() to
the die_nmi() call (since the nmi will never exit "normally")
it seems to solve this problem. The following small program
can be used to trigger the NMI watchdog to reproduce this:
main ()
{
iopl(3);
for (;;) asm("cli");
}
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I noticed this when poking around in this area.
The oops_begin() function in x86_64 would only conditionally claim
the die_lock if the call is nested, but oops_end() would always
release the spinlock. This patch adds a nest count for the die lock
so that the release of the lock is only done on the final oops_end().
Signed-off-by: Corey Minyard <minyard@acm.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
o Start booting into the capture kernel after an Oops if system is in a
unrecoverable state. System will boot into the capture kernel, if one is
pre-loaded by the user, and capture the kernel core dump.
o One of the following conditions should be true to trigger the booting of
capture kernel.
- panic_on_oops is set.
- pid of current thread is 0
- pid of current thread is 1
- Oops happened inside interrupt context.
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The boot cmdline is parsed in parse_early_param() and
parse_args(,unknown_bootoption).
And __setup() is used in obsolete_checksetup().
start_kernel()
-> parse_args()
-> unknown_bootoption()
-> obsolete_checksetup()
If __setup()'s callback (->setup_func()) returns 1 in
obsolete_checksetup(), obsolete_checksetup() thinks a parameter was
handled.
If ->setup_func() returns 0, obsolete_checksetup() tries other
->setup_func(). If all ->setup_func() that matched a parameter returns 0,
a parameter is seted to argv_init[].
Then, when runing /sbin/init or init=app, argv_init[] is passed to the app.
If the app doesn't ignore those arguments, it will warning and exit.
This patch fixes a wrong usage of it, however fixes obvious one only.
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The kernel's implementation of notifier chains is unsafe. There is no
protection against entries being added to or removed from a chain while the
chain is in use. The issues were discussed in this thread:
http://marc.theaimsgroup.com/?l=linux-kernel&m=113018709002036&w=2
We noticed that notifier chains in the kernel fall into two basic usage
classes:
"Blocking" chains are always called from a process context
and the callout routines are allowed to sleep;
"Atomic" chains can be called from an atomic context and
the callout routines are not allowed to sleep.
We decided to codify this distinction and make it part of the API. Therefore
this set of patches introduces three new, parallel APIs: one for blocking
notifiers, one for atomic notifiers, and one for "raw" notifiers (which is
really just the old API under a new name). New kinds of data structures are
used for the heads of the chains, and new routines are defined for
registration, unregistration, and calling a chain. The three APIs are
explained in include/linux/notifier.h and their implementation is in
kernel/sys.c.
With atomic and blocking chains, the implementation guarantees that the chain
links will not be corrupted and that chain callers will not get messed up by
entries being added or removed. For raw chains the implementation provides no
guarantees at all; users of this API must provide their own protections. (The
idea was that situations may come up where the assumptions of the atomic and
blocking APIs are not appropriate, so it should be possible for users to
handle these things in their own way.)
There are some limitations, which should not be too hard to live with. For
atomic/blocking chains, registration and unregistration must always be done in
a process context since the chain is protected by a mutex/rwsem. Also, a
callout routine for a non-raw chain must not try to register or unregister
entries on its own chain. (This did happen in a couple of places and the code
had to be changed to avoid it.)
Since atomic chains may be called from within an NMI handler, they cannot use
spinlocks for synchronization. Instead we use RCU. The overhead falls almost
entirely in the unregister routine, which is okay since unregistration is much
less frequent that calling a chain.
Here is the list of chains that we adjusted and their classifications. None
of them use the raw API, so for the moment it is only a placeholder.
ATOMIC CHAINS
-------------
arch/i386/kernel/traps.c: i386die_chain
arch/ia64/kernel/traps.c: ia64die_chain
arch/powerpc/kernel/traps.c: powerpc_die_chain
arch/sparc64/kernel/traps.c: sparc64die_chain
arch/x86_64/kernel/traps.c: die_chain
drivers/char/ipmi/ipmi_si_intf.c: xaction_notifier_list
kernel/panic.c: panic_notifier_list
kernel/profile.c: task_free_notifier
net/bluetooth/hci_core.c: hci_notifier
net/ipv4/netfilter/ip_conntrack_core.c: ip_conntrack_chain
net/ipv4/netfilter/ip_conntrack_core.c: ip_conntrack_expect_chain
net/ipv6/addrconf.c: inet6addr_chain
net/netfilter/nf_conntrack_core.c: nf_conntrack_chain
net/netfilter/nf_conntrack_core.c: nf_conntrack_expect_chain
net/netlink/af_netlink.c: netlink_chain
BLOCKING CHAINS
---------------
arch/powerpc/platforms/pseries/reconfig.c: pSeries_reconfig_chain
arch/s390/kernel/process.c: idle_chain
arch/x86_64/kernel/process.c idle_notifier
drivers/base/memory.c: memory_chain
drivers/cpufreq/cpufreq.c cpufreq_policy_notifier_list
drivers/cpufreq/cpufreq.c cpufreq_transition_notifier_list
drivers/macintosh/adb.c: adb_client_list
drivers/macintosh/via-pmu.c sleep_notifier_list
drivers/macintosh/via-pmu68k.c sleep_notifier_list
drivers/macintosh/windfarm_core.c wf_client_list
drivers/usb/core/notify.c usb_notifier_list
drivers/video/fbmem.c fb_notifier_list
kernel/cpu.c cpu_chain
kernel/module.c module_notify_list
kernel/profile.c munmap_notifier
kernel/profile.c task_exit_notifier
kernel/sys.c reboot_notifier_list
net/core/dev.c netdev_chain
net/decnet/dn_dev.c: dnaddr_chain
net/ipv4/devinet.c: inetaddr_chain
It's possible that some of these classifications are wrong. If they are,
please let us know or submit a patch to fix them. Note that any chain that
gets called very frequently should be atomic, because the rwsem read-locking
used for blocking chains is very likely to incur cache misses on SMP systems.
(However, if the chain's callout routines may sleep then the chain cannot be
atomic.)
The patch set was written by Alan Stern and Chandra Seetharaman, incorporating
material written by Keith Owens and suggestions from Paul McKenney and Andrew
Morton.
[jes@sgi.com: restructure the notifier chain initialization macros]
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Jes Sorensen <jes@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
- adjust limits of GDT/IDT pseudo-descriptors (some were off by one)
- move empty_zero_page into .bss.page_aligned
- move cpu_gdt_table into .data.page_aligned
- move idt_table into .bss
- align inital_code and init_rsp
- eliminate pointless (re-)declaration of idt_table in traps.c
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Attached is a small code style cleanup patch that resulted from my
skimming through the arch/x86_64/kernel/traps.c code to figure out what
went haywire.
Signed-off-by: Roberto Nibali <ratz@drugphish.ch>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
While the modular aspect of the respective i386 patch doesn't apply to
x86-64 (as the top level page directory entry is shared between modules
and the base kernel), handlers registered with register_die_notifier()
are still under similar constraints for touching ioremap()ed or
vmalloc()ed memory. The likelihood of this problem becoming visible is
of course significantly lower, as the assigned virtual addresses would
have to cross a 2**39 byte boundary. This is because the callback gets
invoked
(a) in the page fault path before the top level page table propagation
gets carried out (hence a fault to propagate the top level page table
entry/entries mapping to module's code/data would nest infinitly) and
(b) in the NMI path, where nested faults must absolutely not happen,
since otherwise the IRET from the nested fault re-enables NMIs,
potentially resulting in nested NMI occurences.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
We found a problem with x86_64 kernels with preemption enabled, where
having multiple tasks doing ptrace singlesteps around the same time will
cause the system to 'oops'. The problem seems that a task can get
preempted out of the do_debug() processing while it is running on the
DEBUG_STACK stack. If another task on that same cpu then enters do_debug()
and uses the same per-cpu DEBUG_STACK stack, the previous preempted tasks's
stack contents can be corrupted, and the system will oops when the
preempted task is context switched back in again.
The typical oops looks like the following:
Unable to handle kernel paging request at ffffffffffffffae RIP: <ffffffff805452a1>{thread_return+34}
PGD 103027 PUD 102429067 PMD 0
Oops: 0002 [1] PREEMPT SMP
CPU 0
Modules linked in:
Pid: 3786, comm: ssdd Not tainted 2.6.15.2 #1
RIP: 0010:[<ffffffff805452a1>] <ffffffff805452a1>{thread_return+34}
RSP: 0018:ffffffff80824058 EFLAGS: 000136c2
RAX: ffff81017e12cea0 RBX: 0000000000000000 RCX: 00000000c0000100
RDX: 0000000000000000 RSI: ffff8100f7856e20 RDI: ffff81017e12cea0
RBP: 0000000000000046 R08: ffff8100f68a6000 R09: 0000000000000000
R10: 0000000000000000 R11: ffff81017e12cea0 R12: ffff81000c2d53e8
R13: ffff81017f5b3be8 R14: ffff81000c0036e0 R15: 000001056cbfc899
FS: 00002aaaaaad9b00(0000) GS:ffffffff80883800(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: ffffffffffffffae CR3: 00000000f6fcf000 CR4: 00000000000006e0
Process ssdd (pid: 3786, threadinfo ffff8100f68a6000, task ffff8100f7856e20)
Stack: ffffffff808240d8 ffffffff8012a84a ffff8100055f6c00 0000000000000020
0000000000000001 ffff81000c0036e0 ffffffff808240b8 0000000000000000
0000000000000000 0000000000000000
Call Trace: <#DB>
<ffffffff8012a84a>{try_to_wake_up+985}
<ffffffff8012c0d3>{kick_process+87}
<ffffffff8013b262>{signal_wake_up+48}
<ffffffff8013b5ce>{specific_send_sig_info+179}
<ffffffff80546abc>{_spin_unlock_irqrestore+27}
<ffffffff8013b67c>{force_sig_info+159}
<ffffffff801103a0>{do_debug+289} <ffffffff80110278>{sync_regs+103}
<ffffffff8010ed9a>{paranoid_userspace+35}
Unable to handle kernel paging request at 00007fffffb7d000 RIP: <ffffffff8010f2e4>{show_trace+465}
PGD f6f25067 PUD f6fcc067 PMD f6957067 PTE 0
Oops: 0000 [2] PREEMPT SMP
This patch disables preemptions for the task upon entry to do_debug(), before
interrupts are reenabled, and then disables preemption before exiting
do_debug(), after disabling interrupts. I've noticed that the task can be
preempted either at the end of an interrupt, or on the call to
force_sig_info() on the spin_unlock_irqrestore() processing. It might be
better to attempt to code a fix in entry.S around the code that calls
do_debug().
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
A kprobe executes IRET early and that could cause NMI recursion
and stack corruption.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
When building in a separate objtree, file names produced by BUG() & Co. can
get fairly long; printing only the first 50 characters may thus result in
(almost) no useful information. The following change makes it so that rather
the last 50 characters of the filename get printed.
Signed-Off-By: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Especially under Xen, where the console cannot be adjusted to more than 25
lines, it is fairly important that the information displayed during a panic
is as compact as possible. Below adjustments work towards that.
Signed-Off-By: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
It was set as an NMI, but the NMI bit always forces an interrupt
to end up at vector 2. So it was never used. Remove.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I would like to throw out a suggestion for a possible change in the way that
the debug register traps are handled in do_debug() when the trap occurs
in kernel-mode.
In the x86_64 version of do_debug(), the code will skip around sending
a SIGTRAP to the current task if the trap occurred while in kernel mode.
On the i386-side of things, if the access happens to occur in kernel mode
(say during a read(2) of user's buffer that matches the address of a
debug register trap), then the do_debug() routine for i386 will go ahead
and call send_sigtrap() and send the SIGTRAP signal. The send_sigtrap()
code will also set the info.si_addr to NULL in this case (even though I
don't understand why, since the SIGTRAP siginfo processing doesn't use
the si_addr field...).
So I would like to suggest that the x86_64 do_debug() routine also
follow this type of behavior and have it go ahead and send the
SIGTRAP signal to the current task, even if the debug register trap
happens to have occurred in kernel mode. I have taken a stab at
a patch for this change below. (It includes the i386-ish change
for setting si_addr to NULL when the trap occurred in kernel mode.)
It seems like a useful feature to be able to 'watch' a user location that
might also be modified in the kernel via a system service call, and have the
debugger report that information back to the user, rather than to just
silently ignore the trap.
Additionally, I realize that users that pull in a kernel debugger such as
KGDB into their kernel might want to remove this change below when they add
in KGDB support. However, they could alternatively look at the current
task's thread.debugreg[] values to see if the trap occurred due to KGDB
or instead because of a user-space debugger trap, and still honor the
user SIGTRAP processing (instead of the KGDB breakpoint processing)
if the trap matches up with the thread.debugreg[] registers.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This
- switches the INT3 handler to run on an IST stack (to cope with
breakpoints set by a kernel debugger on places where the kernel's
%gs base hasn't been set up, yet); the IST stack used is shared with
the INT1 handler's
[AK: this also allows setting a kprobe on the interrupt/exception entry
points]
- allows nesting of INT1/INT3 handlers so that one can, with a kernel
debugger, debug (at least) the user-mode portions of the INT1/INT3
handling; the nesting isn't actively enabled here since a kernel-
debugger-free kernel doesn't need it
Signed-Off-By: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Since a double fault always implies that kernel data structures are
corrupt, this fault should neither be handed to user mode handling,
nor should the handler allow resuming the faulting code stream (since
architecturally this isn't a fault, but an abort).
Note that this slightly depends on the previously submitted patch
adjusting the prototype of notify_die() (a compiler warning will result
without that other patch).
AK: Removed obsolete CONFIG_CHECKING code, added comments
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This adjusts things so that handlers of the die() notifier will have
sufficient information about the trap currently being handled. It also
adjusts the notify_die() prototype to (again) match that of i386.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
