[PATCH] x86_64: Save original IST values for checking stack addresses

The values in init_tss.ist[] can change when an IST event occurs.  Save
the original IST values for checking stack addresses when debugging or
doing stack traces.

Signed-off-by: Keith Owens <kaos@ocs.com.au>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 8 insertions, 2 deletions

diff --git a/arch/x86_64/kernel/init_task.c b/arch/x86_64/kernel/init_task.c
index ce31d904d601..3dc5854ba21e 100644
--- a/arch/x86_64/kernel/init_task.c
+++ b/arch/x86_64/kernel/init_task.c
@@ -46,4 +46,9 @@ EXPORT_SYMBOL(init_task);
  */ 
 DEFINE_PER_CPU(struct tss_struct, init_tss) ____cacheline_internodealigned_in_smp = INIT_TSS;
 
+/* Copies of the original ist values from the tss are only accessed during
+ * debugging, no special alignment required.
+ */
+DEFINE_PER_CPU(struct orig_ist, orig_ist);
+
 #define ALIGN_TO_4K __attribute__((section(".data.init_task")))
diff --git a/arch/x86_64/kernel/setup64.c b/arch/x86_64/kernel/setup64.c
index 6fe58a634b5f..417de564456e 100644
--- a/arch/x86_64/kernel/setup64.c
+++ b/arch/x86_64/kernel/setup64.c
@@ -189,6 +189,7 @@ void __cpuinit cpu_init (void)
 {
         int cpu = stack_smp_processor_id();
         struct tss_struct *t = &per_cpu(init_tss, cpu);
+        struct orig_ist *orig_ist = &per_cpu(orig_ist, cpu);
         unsigned long v; 
         char *estacks = NULL; 
         struct task_struct *me;
@@ -256,7 +257,7 @@ void __cpuinit cpu_init (void)
                         estacks += EXCEPTION_STKSZ;
                         break;
                 }
-                t->ist[v] = (unsigned long)estacks;
+                orig_ist->ist[v] = t->ist[v] = (unsigned long)estacks;
         }
 
         t->io_bitmap_base = offsetof(struct tss_struct, io_bitmap);
diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c
index 5e00af54af65..b1249774d1e8 100644
--- a/arch/x86_64/kernel/traps.c
+++ b/arch/x86_64/kernel/traps.c
@@ -178,7 +178,7 @@ static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
                         break;
 #endif
                 default:
-                        end = per_cpu(init_tss, cpu).ist[k];
+                        end = per_cpu(orig_ist, cpu).ist[k];
                         break;
                 }
                 /*