[PATCH] poison invalid cpus

[Olaf Hering <olh@suse.de>]

from Anton Blanchard <anton@samba.org>
Novell bug145459

Ensure that per cpu access to !possible cpus causes a fault instead of silent
corruption.

Signed-off-by: Olaf Hering <olh@suse.de>

 arch/powerpc/kernel/setup_64.c |    8 ++++++++
 1 files changed, 8 insertions(+)

Index: linux-2.6.16-rc1-git3/arch/powerpc/kernel/setup_64.c
===================================================================
--- linux-2.6.16-rc1-git3.orig/arch/powerpc/kernel/setup_64.c
+++ linux-2.6.16-rc1-git3/arch/powerpc/kernel/setup_64.c
@@ -670,6 +670,14 @@ void __init setup_per_cpu_areas(void)
 		size = PERCPU_ENOUGH_ROOM;
 #endif
 
+	/*
+	 * Poison invalid cpus, with lots of high bits set this should
+	 * always fault
+	 */
+	for (i = 0; i < NR_CPUS; i++) {
+		paca[i].data_offset = 0xeeeeeeeeeeeeeeeeULL;
+	}
+
 	for_each_cpu(i) {
 		ptr = alloc_bootmem_node(NODE_DATA(cpu_to_node(i)), size);
 		if (!ptr)
-- 
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