From 4f4bcb6bc485751c0d5cc347930b2f0061aec30c Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Tue, 26 Mar 2019 18:31:29 +0100
Subject: [PATCH 184/204] powerpc/stackprotector: work around stack-guard init
 from atomic

This is invoked from the secondary CPU in atomic context. On x86 we use
tsc instead. On Power we XOR it against mftb() so lets use stack address
as the initial value.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/powerpc/include/asm/stackprotector.h |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Index: linux-6.6.58-rt45/arch/powerpc/include/asm/stackprotector.h
===================================================================
@ linux-6.6.58-rt45/arch/powerpc/include/asm/stackprotector.h:22 @
  */
 static __always_inline void boot_init_stack_canary(void)
 {
-	unsigned long canary = get_random_canary();
+	unsigned long canary;
 
+#ifndef CONFIG_PREEMPT_RT
+	canary = get_random_canary();
+#else
+	canary = ((unsigned long)&canary) & CANARY_MASK;
+#endif
 	current->stack_canary = canary;
 #ifdef CONFIG_PPC64
 	get_paca()->canary = canary;