x86, ptrace: support for branch trace store(BTS)

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Changes to the last version:
- split implementation into two layers: ds/bts and ptrace
- renamed TIF's
- save/restore ds save area msr in __switch_to_xtra()
- make block-stepping only look at BTF bit

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/asm-x86/processor_32.h b/include/asm-x86/processor_32.h
index 0d83da198127..9c0ab7f26bd9 100644
--- a/include/asm-x86/processor_32.h
+++ b/include/asm-x86/processor_32.h
@@ -360,6 +360,9 @@ struct thread_struct {
         unsigned long   io_bitmap_max;
 /* MSR_IA32_DEBUGCTLMSR value to switch in if TIF_DEBUGCTLMSR is set.  */
         unsigned long   debugctlmsr;
+/* Debug Store - if not 0 points to a DS Save Area configuration;
+ *               goes into MSR_IA32_DS_AREA */
+        unsigned long   ds_area_msr;
 };
 
 #define INIT_THREAD  {                                                  \