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x86: fix 32-bit FRAME_POINTER chasing code

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The current x86 32 bit FRAME_POINTER chasing code has a nasty bug in
that the EBP tracer doesn't actually update the value of EBP it is
tracing, so that the code doesn't actually switch to the irq stack
properly.

The result is a truncated backtrace:

 WARNING: at timeroops.c:8 kerneloops_regression_test() (Not tainted)
 Pid: 0, comm: swapper Not tainted 2.6.24-0.77.rc4.git4.fc9 #1
  [<c040649a>] show_trace_log_lvl+0x1a/0x2f
  [<c0406d41>] show_trace+0x12/0x14
  [<c0407061>] dump_stack+0x6c/0x72
  [<e0258049>] kerneloops_regression_test+0x44/0x46 [timeroops]
  [<c04371ac>] run_timer_softirq+0x127/0x18f
  [<c0434685>] __do_softirq+0x78/0xff
  [<c0407759>] do_softirq+0x74/0xf7
  =======================

This patch fixes the code to update EBP properly, and to check the EIP
before printing (as the non-framepointer backtracer does) so that
the same test backtrace now looks like this:

 WARNING: at timeroops.c:8 kerneloops_regression_test()
 Pid: 0, comm: swapper Not tainted 2.6.24-rc7 #4
  [<c0405d17>] show_trace_log_lvl+0x1a/0x2f
  [<c0406681>] show_trace+0x12/0x14
  [<c0406ef2>] dump_stack+0x6a/0x70
  [<e01f6040>] kerneloops_regression_test+0x3b/0x3d [timeroops]
  [<c0426f07>] run_timer_softirq+0x11b/0x17c
  [<c04243ac>] __do_softirq+0x42/0x94
  [<c040704c>] do_softirq+0x50/0xb6
  [<c04242a9>] irq_exit+0x37/0x67
  [<c040714c>] do_IRQ+0x9a/0xaf
  [<c04057da>] common_interrupt+0x2e/0x34
  [<c05807fe>] cpuidle_idle_call+0x52/0x78
  [<c04034f3>] cpu_idle+0x46/0x60
  [<c05fbbd3>] rest_init+0x43/0x45
  [<c070aa3d>] start_kernel+0x279/0x27f
  =======================

This shows that the backtrace goes all the way down to user context now.
This bug was found during the port to 64 bit of the frame pointer backtracer.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Arjan van de Ven 2008-01-30 13:33:06 +01:00 committed by Ingo Molnar
parent 076f9776f5
commit 3d1f7cae88
1 changed files with 3 additions and 1 deletions
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4
arch/x86/kernel/traps_32.c
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@ -125,7 +125,8 @@ static inline unsigned long print_context_stack(struct thread_info *tinfo,
unsigned long addr;
addr = frame->return_address;
ops->address(data, addr);
if (__kernel_text_address(addr))
ops->address(data, addr);
/*
* break out of recursive entries (such as
* end_of_stack_stop_unwind_function). Also,
@ -133,6 +134,7 @@ static inline unsigned long print_context_stack(struct thread_info *tinfo,
* move downwards!
*/
next = frame->next_frame;
bp = (unsigned long) next;
if (next <= frame)
break;
frame = next;