x86: add debug of invalid per_cpu map accesses

Provide a means to trap usages of per_cpu map variables before
they are setup.  Define CONFIG_DEBUG_PER_CPU_MAPS to activate.

Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 15 insertions, 0 deletions

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 88420af98140..0a82b889d76e 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -47,6 +47,18 @@ config DEBUG_PAGEALLOC
           This results in a large slowdown, but helps to find certain types
           of memory corruptions.
 
+config DEBUG_PER_CPU_MAPS
+        bool "Debug access to per_cpu maps"
+        depends on DEBUG_KERNEL
+        depends on X86_64_SMP
+        default n
+        help
+          Say Y to verify that the per_cpu map being accessed has
+          been setup.  Adds a fair amount of code to kernel memory
+          and decreases performance.
+
+          Say N if unsure.
+
 config DEBUG_RODATA
         bool "Write protect kernel read-only data structures"
         depends on DEBUG_KERNEL
diff --git a/arch/x86/mm/numa_64.c b/arch/x86/mm/numa_64.c
index 5d24dc1ec237..e157cb274b25 100644
--- a/arch/x86/mm/numa_64.c
+++ b/arch/x86/mm/numa_64.c
@@ -37,6 +37,9 @@ u16 x86_cpu_to_node_map_init[NR_CPUS] = {
 void *x86_cpu_to_node_map_early_ptr;
 DEFINE_PER_CPU(u16, x86_cpu_to_node_map) = NUMA_NO_NODE;
 EXPORT_PER_CPU_SYMBOL(x86_cpu_to_node_map);
+#ifdef  CONFIG_DEBUG_PER_CPU_MAPS
+EXPORT_SYMBOL(x86_cpu_to_node_map_early_ptr);
+#endif
 
 u16 apicid_to_node[MAX_LOCAL_APIC] __cpuinitdata = {
         [0 ... MAX_LOCAL_APIC-1] = NUMA_NO_NODE