Re: [PATCH] powerpc/64: Initialise thread_info for emergency stacks

On Wed, 21 Jun 2017 12:01:37 +1000
Michael Ellerman [off-list ref] wrote:

Nicholas Piggin [off-list ref] writes:

quoted

diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index a941cc6fc3e9..5995e4b2996d 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h

@@ -62,6 +63,24 @@ struct thread_info {
 
 #define THREAD_SIZE_ORDER	(THREAD_SHIFT - PAGE_SHIFT)
 
+/*
+ * Emergency stacks are used for a range of things, from asynchronous
+ * NMIs (system reset, machine check) to synchronous, process context.
+ * Set HARDIRQ_OFFSET because we don't know exactly what context we
+ * come from or if it had a valid stack, which is about the best we
+ * can do.
+ * TODO: what to do with accounting?
+ */
+#define emstack_init_thread_info(ti, c)		\
+do {						\
+	(ti)->task = NULL;			\
+	(ti)->cpu = (c);			\
+	(ti)->preempt_count = HARDIRQ_OFFSET;	\
+	(ti)->local_flags = 0;			\
+	(ti)->flags = 0;			\
+	klp_init_thread_info(ti);		\
+} while (0)  

Why don't we just bzero() the whole thing? Like we do for the other
stacks?

Wouldn't hurt to.

Thanks,
Nick