Consider a kernel crash in a module, simulated the following way:

 static int my_init(void)
 {
         char *map = (void *)0x5;
         *map = 3;
         return 0;
 }
 module_init(my_init);

When we turn off FRAME_POINTERs, the very first instruction in
that function causes a BUG. The problem is that we print IP in
the BUG report using %pB (from printk_address). And %pB
decrements the pointer by one to fix printing addresses of
functions with tail calls.

This was added in commit 71f9e598 ("x86, dumpstack: Use
%pB format specifier for stack trace") to fix the call stack
printouts.

So instead of correct output:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000005
  IP: [<ffffffffa01ac000>] my_init+0x0/0x10 [pb173]

We get:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000005
  IP: [<ffffffffa0152000>] 0xffffffffa0151fff

To fix that, we use %pS only for stack addresses printouts (via
newly added printk_stack_address) and %pB for regs->ip (via
printk_address). I.e. we revert to the old behaviour for all
except call stacks. And since from all those reliable is 1, we
remove that parameter from printk_address.
Signed-off-by: NJiri Slaby <jslaby@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: joe@perches.com
Cc: jirislaby@gmail.com
Link: http://lkml.kernel.org/r/1382706418-8435-1-git-send-email-jslaby@suse.czSigned-off-by: NIngo Molnar <mingo@kernel.org>

What was called show_registers() so far already showed a stack
trace for kernel faults, and kernel_stack_pointer() isn't even
valid to be used for faults from user mode, hence it was
pointless for show_regs() to call show_trace() after
show_registers().

Simply rename show_registers() to show_regs() and eliminate
the old definition.
Signed-off-by: NJan Beulich <jbeulich@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/4FAA3D3902000078000826E1@nat28.tlf.novell.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

[ poleg@redhat.com: no need to declare show_regs() in ptrace.h, sched.h does this ]
Signed-off-by: NMike Frysinger <vapier@gentoo.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Current stack dump code scans entire stack and check each entry
contains a pointer to kernel code. If CONFIG_FRAME_POINTER=y it
could mark whether the pointer is valid or not based on value of
the frame pointer. Invalid entries could be preceded by '?' sign.

However this was not going to happen because scan start point
was always higher than the frame pointer so that they could not
meet.

Commit 9c0729dc ("x86: Eliminate bp argument from the stack
tracing routines") delayed bp acquisition point, so the bp was
read in lower frame, thus all of the entries were marked
invalid.

This patch fixes this by reverting above commit while retaining
stack_frame() helper as suggested by Frederic Weisbecker.

End result looks like below:

before:

 [    3.508329] Call Trace:
 [    3.508551]  [<ffffffff814f35c9>] ? panic+0x91/0x199
 [    3.508662]  [<ffffffff814f3739>] ? printk+0x68/0x6a
 [    3.508770]  [<ffffffff81a981b2>] ? mount_block_root+0x257/0x26e
 [    3.508876]  [<ffffffff81a9821f>] ? mount_root+0x56/0x5a
 [    3.508975]  [<ffffffff81a98393>] ? prepare_namespace+0x170/0x1a9
 [    3.509216]  [<ffffffff81a9772b>] ? kernel_init+0x1d2/0x1e2
 [    3.509335]  [<ffffffff81003894>] ? kernel_thread_helper+0x4/0x10
 [    3.509442]  [<ffffffff814f6880>] ? restore_args+0x0/0x30
 [    3.509542]  [<ffffffff81a97559>] ? kernel_init+0x0/0x1e2
 [    3.509641]  [<ffffffff81003890>] ? kernel_thread_helper+0x0/0x10

after:

 [    3.522991] Call Trace:
 [    3.523351]  [<ffffffff814f35b9>] panic+0x91/0x199
 [    3.523468]  [<ffffffff814f3729>] ? printk+0x68/0x6a
 [    3.523576]  [<ffffffff81a981b2>] mount_block_root+0x257/0x26e
 [    3.523681]  [<ffffffff81a9821f>] mount_root+0x56/0x5a
 [    3.523780]  [<ffffffff81a98393>] prepare_namespace+0x170/0x1a9
 [    3.523885]  [<ffffffff81a9772b>] kernel_init+0x1d2/0x1e2
 [    3.523987]  [<ffffffff81003894>] kernel_thread_helper+0x4/0x10
 [    3.524228]  [<ffffffff814f6880>] ? restore_args+0x0/0x30
 [    3.524345]  [<ffffffff81a97559>] ? kernel_init+0x0/0x1e2
 [    3.524445]  [<ffffffff81003890>] ? kernel_thread_helper+0x0/0x10

 -v5:
   * fix build breakage with oprofile

 -v4:
   * use 0 instead of regs->bp
   * separate out printk changes

 -v3:
   * apply comment from Frederic
   * add a couple of printk fixes
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Soren Sandmann <ssp@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Robert Richter <robert.richter@amd.com>
LKML-Reference: <1300416006-3163-1-git-send-email-namhyung@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

With no caller left, the function and the DIE_NMIWATCHDOG
enumerator can both go away.
Signed-off-by: NJan Beulich <jbeulich@novell.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Don Zickus <dzickus@redhat.com>
LKML-Reference: <4D5D521C0200007800032702@vpn.id2.novell.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

With priorities in place and no one really understanding the difference between
DIE_NMI and DIE_NMI_IPI, just remove DIE_NMI_IPI and convert everyone to DIE_NMI.

This also simplifies default_do_nmi() a little bit.  Instead of calling the
die_notifier in both the if and else part, just pull it out and call it before
the if-statement.  This has the side benefit of avoiding a call to the ioport
to see if there is an external NMI sitting around until after the (more frequent)
internal NMIs are dealt with.
Patch-Inspired-by: NHuang Ying <ying.huang@intel.com>
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1294348732-15030-5-git-send-email-dzickus@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The various stack tracing routines take a 'bp' argument in which the
caller is supposed to provide the base pointer to use, or 0 if doesn't
have one. Since bp is garbage whenever CONFIG_FRAME_POINTER is not
defined, this means all callers in principle should either always pass
0, or be conditional on CONFIG_FRAME_POINTER.

However, there are only really three use cases for stack tracing:

(a) Trace the current task, including IRQ stack if any
(b) Trace the current task, but skip IRQ stack
(c) Trace some other task

In all cases, if CONFIG_FRAME_POINTER is not defined, bp should just
be 0.  If it _is_ defined, then

- in case (a) bp should be gotten directly from the CPU's register, so
  the caller should pass NULL for regs,

- in case (b) the caller should should pass the IRQ registers to
  dump_trace(),

- in case (c) bp should be gotten from the top of the task's stack, so
  the caller should pass NULL for regs.

Hence, the bp argument is not necessary because the combination of
task and regs is sufficient to determine an appropriate value for bp.

This patch introduces a new inline function stack_frame(task, regs)
that computes the desired bp. This function is then called from the
two versions of dump_stack().
Signed-off-by: NSoren Sandmann <ssp@redhat.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arjan van de Ven <arjan@infradead.org>,
Cc: Frederic Weisbecker <fweisbec@gmail.com>,
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>,
LKML-Reference: <m3oc9rop28.fsf@dhcp-100-3-82.bos.redhat.com>>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

This replaces Version 1 of this patch, which broke the build when
CONFIG_KEXEC and CONFIG_CRASH_DUMP were configured off.  In that case
the storage for the 'in_crash_kexec' flag was never built.

This version defines that flag as 0 if CONFIG_KEXEC is not set.
The patch is tested with all combinations of those two options.
Signed-off-by: NCliff Wickman <cpw@sgi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <E1OiZcw-0001Hb-2g@eag09.americas.sgi.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

UV NMI callback's should not write stack dumps when a kdump is to be written.

When invoking the crash kernel to write a dump, kdump_nmi_shootdown_cpus()
uses NMI's to get all the cpu's to save their register context and halt.

But the NMI interrupt handler runs a callback list.  This patch sets a flag
to prevent any of those callbacks from interfering with the halt of the cpu.

For UV, which currently has the only callback to which this is relevant, the
uv_handle_nmi() callback should not do dumping of stacks.

The 'in_crash_kexec' flag is defined as an extern in kdebug.h firstly
because x2apic_uv_x.c includes it.  Secondly because some future callback
might need the flag to know that it should not enter the debugger.
(Such a scenario was in fact present in the 2.6.32 kernel, SuSE distribution,
 where a call to kdb needed to be avoided.)
Signed-off-by: NCliff Wickman <cpw@sgi.com>
LKML-Reference: <E1ObLvt-0005UZ-Va@eag09.americas.sgi.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Change header guards named "ASM_X86__*" to "_ASM_X86_*" since:

a. the double underscore is ugly and pointless.
b. no leading underscore violates namespace constraints.
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

Currently the low-level function to dump user-passed registers on i386 is
called __show_registers() whereas on x86-64 it's called __show_regs(). Unify
the API to simplify porting of kmemcheck to x86-64.
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>
Acked-by: NVegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

This patch is the result of an automatic script that consolidates the
format of all the headers in include/asm-x86/.

The format:

1. No leading underscore. Names with leading underscores are reserved.
2. Pathname components are separated by two underscores. So we can
   distinguish between mm_types.h and mm/types.h.
3. Everything except letters and numbers are turned into single
   underscores.
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

kmmio.c handles the list of mmio probes with callbacks, list of traced
pages, and attaching into the page fault handler and die notifier. It
arms, traps and disarms the given pages, this is the core of mmiotrace.

mmio-mod.c is a user interface, hooking into ioremap functions and
registering the mmio probes. It also decodes the required information
from trapped mmio accesses via the pre and post callbacks in each probe.
Currently, hooking into ioremap functions works by redefining the symbols
of the target (binary) kernel module, so that it calls the traced
versions of the functions.

The most notable changes done since the last discussion are:
- kmmio.c is a built-in, not part of the module
- direct call from fault.c to kmmio.c, removing all dynamic hooks
- prepare for unregistering probes at any time
- make kmmio re-initializable and accessible to more than one user
- rewrite kmmio locking to remove all spinlocks from page fault path

Can I abuse call_rcu() like I do in kmmio.c:unregister_kmmio_probe()
or is there a better way?

The function called via call_rcu() itself calls call_rcu() again,
will this work or break? There I need a second grace period for RCU
after the first grace period for page faults.

Mmiotrace itself (mmio-mod.c) is still a module, I am going to attack
that next. At some point I will start looking into how to make mmiotrace
a tracer component of ftrace (thanks for the hint, Ingo). Ftrace should
make the user space part of mmiotracing as simple as
'cat /debug/trace/mmio > dump.txt'.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

The custom page fault handler list is replaced with a single function
pointer. All related functions and variables are renamed for
mmiotrace.
Signed-off-by: NPekka Paalanen <pq@iki.fi>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: pq@iki.fi
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Provides kernel modules a way to register custom page fault handlers.
On every page fault this will call a list of registered functions. The
functions may handle the fault and force do_page_fault() to return
immediately.

This functionality is similar to the now removed page fault notifiers.
Custom page fault handlers are used by debugging and reverse engineering
tools. Mmiotrace is one such tool and a patch to add it into the tree
will follow.

The custom page fault handlers are called earlier in do_page_fault()
than the page fault notifiers were.
Signed-off-by: NPekka Paalanen <pq@iki.fi>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

This patch fixes the hang regression with kgdb when the NMI interrupt
comes in while the master core is returning from an exception.

Adjust the NMI logic such that KGDB will not stop NMI exceptions from
occurring by in general returning NOTIFY_DONE.  It is not possible to
distinguish the debug NMI sync vs the normal NMI apic interrupt so
kgdb needs to catch the unknown NMI if it the debugger was previously
active on one of the cpus.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

dump_pagetable() can now become static.
Signed-off-by: NAdrian Bunk <bunk@kernel.org>
Acked-by: NArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

For enhancing the 32 bit EBP based backtracer, I need the capability
for the backtracer to tell it's customer that an entry is either
reliable or unreliable, and the backtrace printing code then needs to
print the unreliable ones slightly different.

This patch adds the basic capability, the next patch will add a user
of this capability.
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Enable CONFIG_EMBEDDED to select CONFIG_EARLY_PRINTK on 64-bit as well.

saves ~2K:

   text    data     bss     dec     hex filename
   7290283 3672091 1907848 12870222         c4624e vmlinux.before
   7288373 3671795 1907848 12868016         c459b0 vmlinux.after
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

This requires making die() return a value, making its callers honor
this (and be prepared that it may return), and making oops_end() have
two additional parameters.
Signed-off-by: NJan Beulich <jbeulich@novell.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Move them and fixup some users.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The 64 bit variant has additional function prototypes which do no harm
for 32 bit.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Move the headers to include/asm-x86 and fixup the
header install make rules
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>