arm64: make irq_stack_ptr more robust

[deliverable/linux.git] / arch / arm64 / kernel / stacktrace.c

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 4fad9787ab46ed04bf36873e8f7f7eb724beb262..d9751a4769e758b220181d6a400bd5a238c2cedb 100644 (file)
--- 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 */
@@ -64,8 +63,8 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
                return -EINVAL;
 
        frame->sp = fp + 0x10;
-       frame->fp = *(unsigned long *)(fp);
-       frame->pc = *(unsigned long *)(fp + 8);
+       frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
+       frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
        if (tsk && tsk->ret_stack &&