x86, ds: allow small debug store buffers

Check the buffer size more precisely to allow buffers for exactly
one element provided the base address is already properly aligned.

Add a debug store selftest.

Reported-by: Stephane Eranian <eranian@googlemail.com>
Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Cc: roland@redhat.com
Cc: eranian@googlemail.com
Cc: oleg@redhat.com
Cc: juan.villacis@intel.com
Cc: ak@linux.jf.intel.com
LKML-Reference: <20090403144606.139137000@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 3 deletions

diff --git a/arch/x86/kernel/ds_selftest.c b/arch/x86/kernel/ds_selftest.c
index a40b2533c71e..5f104a0ace66 100644
--- a/arch/x86/kernel/ds_selftest.c
+++ b/arch/x86/kernel/ds_selftest.c
@@ -16,8 +16,8 @@
 #include <asm/ds.h>
 
 
-#define BUFFER_SIZE     521 /* Intentionally chose an odd size. */
-
+#define BUFFER_SIZE             521     /* Intentionally chose an odd size. */
+#define SMALL_BUFFER_SIZE       24      /* A single bts entry. */
 
 struct ds_selftest_bts_conf {
         struct bts_tracer *tracer;
@@ -381,7 +381,7 @@ int ds_selftest_bts(void)
         conf.suspend = ds_suspend_bts_noirq;
         conf.resume = ds_resume_bts_noirq;
         conf.tracer =
-                ds_request_bts_task(current, buffer, BUFFER_SIZE,
+                ds_request_bts_task(current, buffer, SMALL_BUFFER_SIZE,
                                    NULL, (size_t)-1, BTS_KERNEL);
         local_irq_save(irq);
         ds_selftest_bts_cpu(&conf);