hw-breakpoints: reset bits in dr6 after the corresponding exception is handled

This patch resets the bit in dr6 after the corresponding exception is
handled in code, so that we keep a clean track of the current virtual debug
status register.

[ Impact: keep track of breakpoints triggering completion ]

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index 7b5169d2b000..b5b1848c5336 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -54,6 +54,7 @@
 #include <asm/pgtable.h>
 #include <asm/uaccess.h>
 #include <asm/alternative.h>
+#include <asm/debugreg.h>
 
 void jprobe_return_end(void);
 
@@ -967,8 +968,14 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
                         ret = NOTIFY_STOP;
                 break;
         case DIE_DEBUG:
-                if (post_kprobe_handler(args->regs))
+                if (post_kprobe_handler(args->regs)) {
+                        /*
+                         * Reset the BS bit in dr6 (pointed by args->err) to
+                         * denote completion of processing
+                         */
+                        (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;
                         ret = NOTIFY_STOP;
+                }
                 break;
         case DIE_GPF:
                 /*