From 47ce11a2b6519f9c7843223ea8e561eb71ea5896 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Thu, 30 Jun 2011 19:04:56 +0200 Subject: [PATCH] x86: Fetch stack from regs when possible in dump_trace() When regs are passed to dump_stack(), we fetch the frame pointer from the regs but the stack pointer is taken from the current frame. Thus the frame and stack pointers may not come from the same context. For example this can result in the unwinder to think the context is in irq, due to the current value of the stack, but the frame pointer coming from the regs points to a frame from another place. It then tries to fix up the irq link but ends up dereferencing a random frame pointer that doesn't belong to the irq stack: [ 9131.706906] ------------[ cut here ]------------ [ 9131.707003] WARNING: at arch/x86/kernel/dumpstack_64.c:129 dump_trace+0x2aa/0x330() [ 9131.707003] Hardware name: AMD690VM-FMH [ 9131.707003] Perf: bad frame pointer = 0000000000000005 in callchain [ 9131.707003] Modules linked in: [ 9131.707003] Pid: 1050, comm: perf Not tainted 3.0.0-rc3+ #181 [ 9131.707003] Call Trace: [ 9131.707003] [] warn_slowpath_common+0x7a/0xb0 [ 9131.707003] [] warn_slowpath_fmt+0x41/0x50 [ 9131.707003] [] ? bad_to_user+0x6d/0x10be [ 9131.707003] [] dump_trace+0x2aa/0x330 [ 9131.707003] [] ? native_sched_clock+0x13/0x50 [ 9131.707003] [] perf_callchain_kernel+0x54/0x70 [ 9131.707003] [] perf_prepare_sample+0x19f/0x2a0 [ 9131.707003] [] __perf_event_overflow+0x16c/0x290 [ 9131.707003] [] ? __perf_event_overflow+0x130/0x290 [ 9131.707003] [] ? native_sched_clock+0x13/0x50 [ 9131.707003] [] ? sched_clock+0x9/0x10 [ 9131.707003] [] ? T.375+0x15/0x90 [ 9131.707003] [] ? trace_hardirqs_on_caller+0x64/0x180 [ 9131.707003] [] ? trace_hardirqs_off+0xd/0x10 [ 9131.707003] [] perf_event_overflow+0x14/0x20 [ 9131.707003] [] perf_swevent_hrtimer+0x11c/0x130 [ 9131.707003] [] ? error_exit+0x51/0xb0 [ 9131.707003] [] __run_hrtimer+0x83/0x1e0 [ 9131.707003] [] ? perf_event_overflow+0x20/0x20 [ 9131.707003] [] hrtimer_interrupt+0x106/0x250 [ 9131.707003] [] ? trace_hardirqs_off_thunk+0x3a/0x3c [ 9131.707003] [] smp_apic_timer_interrupt+0x53/0x90 [ 9131.707003] [] apic_timer_interrupt+0x13/0x20 [ 9131.707003] [] ? error_exit+0x51/0xb0 [ 9131.707003] [] ? error_exit+0x4c/0xb0 [ 9131.707003] ---[ end trace b2560d4876709347 ]--- Fix this by simply taking the stack pointer from regs->sp when regs are provided. Signed-off-by: Frederic Weisbecker Cc: Ingo Molnar Cc: Thomas Gleixner Cc: H. Peter Anvin Cc: Peter Zijlstra Cc: Arnaldo Carvalho de Melo --- arch/x86/kernel/dumpstack_64.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c index e71c98d3c0d..788295cbe4a 100644 --- a/arch/x86/kernel/dumpstack_64.c +++ b/arch/x86/kernel/dumpstack_64.c @@ -155,9 +155,12 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs, task = current; if (!stack) { - stack = &dummy; - if (task && task != current) + if (regs) + stack = (unsigned long *)regs->sp; + else if (task && task != current) stack = (unsigned long *)task->thread.sp; + else + stack = &dummy; } if (!bp) -- 2.41.0