Commit a80a0eb7 authored by Yang Shi's avatar Yang Shi Committed by Will Deacon

arm64: make irq_stack_ptr more robust

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.

Fixes: 132cd887 ("arm64: Modify stack trace and dump for use with irq_stack")
Acked-by: default avatarJames Morse <james.morse@arm.com>
Tested-by: default avatarJames Morse <james.morse@arm.com>
Signed-off-by: default avatarYang Shi <yang.shi@linaro.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent e04a28d4
......@@ -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 */
......
......@@ -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
* 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)
......
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