linux-toradex.git/arch/x86/kernel/dumpstack_64.c, branch v3.0.44

x86, dumpstack: Correct stack dump info when frame pointer is available

2011-03-18T09:51:42+00:00

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 9c0729dc8062 ("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]  [] ? panic+0x91/0x199
 [    3.508662]  [] ? printk+0x68/0x6a
 [    3.508770]  [] ? mount_block_root+0x257/0x26e
 [    3.508876]  [] ? mount_root+0x56/0x5a
 [    3.508975]  [] ? prepare_namespace+0x170/0x1a9
 [    3.509216]  [] ? kernel_init+0x1d2/0x1e2
 [    3.509335]  [] ? kernel_thread_helper+0x4/0x10
 [    3.509442]  [] ? restore_args+0x0/0x30
 [    3.509542]  [] ? kernel_init+0x0/0x1e2
 [    3.509641]  [] ? kernel_thread_helper+0x0/0x10

after:

 [    3.522991] Call Trace:
 [    3.523351]  [] panic+0x91/0x199
 [    3.523468]  [] ? printk+0x68/0x6a
 [    3.523576]  [] mount_block_root+0x257/0x26e
 [    3.523681]  [] mount_root+0x56/0x5a
 [    3.523780]  [] prepare_namespace+0x170/0x1a9
 [    3.523885]  [] kernel_init+0x1d2/0x1e2
 [    3.523987]  [] kernel_thread_helper+0x4/0x10
 [    3.524228]  [] ? restore_args+0x0/0x30
 [    3.524345]  [] ? kernel_init+0x0/0x1e2
 [    3.524445]  [] ? 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: Namhyung Kim 
Acked-by: Peter Zijlstra 
Acked-by: Frederic Weisbecker 
Cc: Soren Sandmann 
Cc: Paul Mackerras 
Cc: Arnaldo Carvalho de Melo 
Cc: Robert Richter 
LKML-Reference: <1300416006-3163-1-git-send-email-namhyung@gmail.com>
Signed-off-by: Ingo Molnar

x86-64: Don't use pointer to out-of-scope variable in dump_trace()

2011-01-24T21:46:15+00:00

In arch/x86/kernel/dumpstack_64.c::dump_trace() we have this code:

...
  		if (!stack) {
  			unsigned long dummy;
  			stack = &dummy;
  			if (task && task != current)
  				stack = (unsigned long *)task->thread.sp;
  		}

  		bp = stack_frame(task, regs);
  		/*
  		 * Print function call entries in all stacks, starting at the
  		 * current stack address. If the stacks consist of nested
  		 * exceptions
  		 */
  		tinfo = task_thread_info(task);

  		for (;;) {
  			char *id;
  			unsigned long *estack_end;
  			estack_end = in_exception_stack(cpu, (unsigned long)stack,
  							&used, &id);
...

You'll notice that we assign to 'stack' the address of the variable
'dummy' which is only in-scope inside the 'if (!stack)'. So when we later
access stack (at the end of the above, and assuming we did not take the
'if (task && task != current)' branch) we'll be using the address of a
variable that is no longer in scope. I believe this patch is the proper
fix, but I freely admit that I'm not 100% certain.

Signed-off-by: Jesper Juhl 
LKML-Reference: 
Signed-off-by: H. Peter Anvin

x86: Eliminate bp argument from the stack tracing routines

2010-11-18T13:37:34+00:00

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: Soren Sandmann 
Acked-by: Steven Rostedt 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: H. Peter Anvin 
Cc: Peter Zijlstra 
Cc: Arjan van de Ven ,
Cc: Frederic Weisbecker ,
Cc: Arnaldo Carvalho de Melo ,
LKML-Reference: >
Signed-off-by: Frederic Weisbecker

x86, printk: Get rid of <0> from stack output

2010-10-23T18:03:03+00:00

The stack output currently looks like this:

 7fffffffffffffff 0000000a00000000 ffffffff81093341 0000000000000046
<0> ffff88003a545fd8 0000000000000000 0000000000000000 00007fffa39769c0
<0> ffff88003e403f58 ffffffff8102fc4c ffff88003e403f58 ffff88003e403f78

The superfluous <0> are caused by recent printk KERN_CONT
change. <*> is now ignored in printk unless some text follows
the level and even then it still has to be the first in the
format message.

Note that the log_lvl parameter is now completely ignored in
show_stack_log_lvl and the stack is dumped with the default
level (like for quite some time already). It behaves the same as
the rest of the dump, function traces are dumped in the very
same manner. Only Code and maybe some lines are printed with
EMERG level.

Unfortunately I see no way how to fix this conceptually to have
the whole oops/BUG/panic output with the same level, so this
removed only the superfluous characters for the time being.

Just for illustration:

<4>Process kworker/0:0 (pid: 0, threadinfo ffff88003c8a6000, task ffff88003c85c100)
<0>Stack:
<4> ffffffff818022c0 0000000a00000001 0000000000000001 0000000000000046
<4> ffff88003c8a7fd8 0000000000000001 ffff88003c8a7e58 0000000000000000
<4> ffff88003e503f48 ffffffff8102fc4c ffff88003e503f48 ffff88003e503f68
<0>Call Trace:
<0> 
<4> [] ? call_softirq+0x1c/0x30 ...
<0>Code: 00 01 00 00 65 8b 04 25 80 c5 00 00 c7 45 ...

Signed-off-by: Jiri Slaby 
Cc: jirislaby@gmail.com
Cc: Linus Torvalds 
Cc: Andrew Morton 
LKML-Reference: <1287586131-16222-1-git-send-email-jslaby@suse.cz>
Signed-off-by: Ingo Molnar

x86: Unify dumpstack.h and stacktrace.h

2010-06-08T21:29:52+00:00

arch/x86/include/asm/stacktrace.h and arch/x86/kernel/dumpstack.h
declare headers of objects that deal with the same topic.
Actually most of the files that include stacktrace.h also include
dumpstack.h

Although dumpstack.h seems more reserved for internals of stack
traces, those are quite often needed to define specialized stack
trace operations. And perf event arch headers are going to need
access to such low level operations anyway. So don't continue to
bother with dumpstack.h as it's not anymore about isolated deep
internals.

v2: fix struct stack_frame definition conflict in sysprof

Signed-off-by: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: H. Peter Anvin 
Cc: Thomas Gleixner 
Cc: Soeren Sandmann

perf/x86-64: Use frame pointer to walk on irq and process stacks

2010-03-10T13:26:40+00:00

We were using the frame pointer based stack walker on every
contexts in x86-32, but not in x86-64 where we only use the
seven-league boots on the exception stacks.

Use it also on irq and process stacks. This utterly accelerate
the captures.

Signed-off-by: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Paul Mackerras 
Cc: Arnaldo Carvalho de Melo

Merge commit 'v2.6.34-rc1' into perf/urgent

2010-03-09T16:11:53+00:00

Conflicts:
	tools/perf/util/probe-event.c

Merge reason: Pick up -rc1 and resolve the conflict as well.

Signed-off-by: Ingo Molnar

Merge branch 'perf/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing into perf/urgent

2010-03-04T11:27:39+00:00

x86/stacktrace: Don't dereference bad frame pointers

2010-03-03T03:07:23+00:00

Callers of a stacktrace might pass bad frame pointers. Those
are usually checked for safety in stack walking helpers before
any dereferencing, but this is not the case when we need to go
through one more frame pointer that backlinks the irq stack to
the previous one, as we don't have any reliable address boudaries
to compare this frame pointer against.

This raises crashes when we record callchains for ftrace events
with perf because we don't use the right helpers to capture
registers there. We get wrong frame pointers as we call
task_pt_regs() even on kernel threads, which is a wrong thing
as it gives us the initial state of any kernel threads freshly
created. This is even not what we want for user tasks. What we want
is a hot snapshot of registers when the ftrace event triggers, not
the state before a task entered the kernel.

This requires more thoughts to do it correctly though.
So first put a guardian to ensure the given frame pointer
can be dereferenced to avoid crashes. We'll think about how to fix
the callers in a subsequent patch.

Signed-off-by: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: Thomas Gleixner 
Cc: H. Peter Anvin 
Cc: Peter Zijlstra 
Cc: Paul Mackerras 
Cc: Steven Rostedt 
Cc: 2.6.33.x 
Cc: Arnaldo Carvalho de Melo

Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2010-02-28T18:20:25+00:00

* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (172 commits)
  perf_event, amd: Fix spinlock initialization
  perf_event: Fix preempt warning in perf_clock()
  perf tools: Flush maps on COMM events
  perf_events, x86: Split PMU definitions into separate files
  perf annotate: Handle samples not at objdump output addr boundaries
  perf_events, x86: Remove superflous MSR writes
  perf_events: Simplify code by removing cpu argument to hw_perf_group_sched_in()
  perf_events, x86: AMD event scheduling
  perf_events: Add new start/stop PMU callbacks
  perf_events: Report the MMAP pgoff value in bytes
  perf annotate: Defer allocating sym_priv->hist array
  perf symbols: Improve debugging information about symtab origins
  perf top: Use a macro instead of a constant variable
  perf symbols: Check the right return variable
  perf/scripts: Tag syscall_name helper as not yet available
  perf/scripts: Add perf-trace-python Documentation
  perf/scripts: Remove unnecessary PyTuple resizes
  perf/scripts: Add syscall tracing scripts
  perf/scripts: Add Python scripting engine
  perf/scripts: Remove check-perf-trace from listed scripts
  ...

Fix trivial conflict in tools/perf/util/probe-event.c