Messages in this thread | | | Date | Fri, 12 Feb 2016 13:47:12 +0000 | From | James Morse <> | Subject | Re: [PATCH] arm64: make irq_stack_ptr more robust |
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Hi!
On 11/02/16 21:53, Yang Shi wrote: > Switching between stacks is only valid if we are tracing ourselves while on the > irq_stack, so it is only valid when in current and non-preemptible context, > otherwise is is just zeroed off.
Given it was picked up with CONFIG_DEBUG_PREEMPT:
Fixes: 132cd887b5c5 ("arm64: Modify stack trace and dump for use with irq_stack")
> Signed-off-by: Yang Shi <yang.shi@linaro.org> > --- > arch/arm64/kernel/stacktrace.c | 13 ++++++------- > arch/arm64/kernel/traps.c | 11 ++++++++++- > 2 files changed, 16 insertions(+), 8 deletions(-) > > diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c > index 12a18cb..d9751a4 100644 > --- a/arch/arm64/kernel/stacktrace.c > +++ b/arch/arm64/kernel/stacktrace.c > @@ -44,14 +44,13 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) > unsigned long irq_stack_ptr; > > /* > - * Use raw_smp_processor_id() to avoid false-positives from > - * CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() on sleeping > - * task stacks, we can be pre-empted in this case, so > - * {raw_,}smp_processor_id() may give us the wrong value. Sleeping > - * tasks can't ever be on an interrupt stack, so regardless of cpu, > - * the checks will always fail. > + * Switching between stacks is valid when tracing current and in > + * non-preemptible context. > */ > - irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id()); > + if (tsk == current && !preemptible()) > + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); > + else > + irq_stack_ptr = 0; > > low = frame->sp; > /* irq stacks are not THREAD_SIZE aligned */ > diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c > index cbedd72..7d8db3a 100644 > --- a/arch/arm64/kernel/traps.c > +++ b/arch/arm64/kernel/traps.c > @@ -146,9 +146,18 @@ static void dump_instr(const char *lvl, struct pt_regs *regs) > static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) > { > struct stackframe frame; > - unsigned long irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); > + unsigned long irq_stack_ptr; > int skip; > > + /* > + * Switching between stacks is valid when tracing current and in
Nit: Two spaces: "between[ ][ ]stacks"
> + * non-preemptible context. > + */ > + if (tsk == current && !preemptible()) > + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); > + else > + irq_stack_ptr = 0; > + > pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); > > if (!tsk) >
Neither file includes 'linux/preempt.h' for the definition of preemptible(). (I can't talk: I should have included smp.h for smp_processor_id())
Acked-by: James Morse <james.morse@arm.com> Tested-by: James Morse <james.morse@arm.com>
Thanks!
James
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