ptrace/x86: Introduce set_task_blockstep() helper

No functional changes, preparation for the next fix and for uprobes
single-step fixes.

Move the code playing with TIF_BLOCKSTEP/DEBUGCTLMSR_BTF into the
new helper, set_task_blockstep().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

1 files changed, 21 insertions, 20 deletions

diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c
index c346d1161488..7a514986ca09 100644
--- a/arch/x86/kernel/step.c
+++ b/arch/x86/kernel/step.c
@@ -157,6 +157,21 @@ static int enable_single_step(struct task_struct *child)
         return 1;
 }
 
+static void set_task_blockstep(struct task_struct *task, bool on)
+{
+        unsigned long debugctl;
+
+        debugctl = get_debugctlmsr();
+        if (on) {
+                debugctl |= DEBUGCTLMSR_BTF;
+                set_tsk_thread_flag(task, TIF_BLOCKSTEP);
+        } else {
+                debugctl &= ~DEBUGCTLMSR_BTF;
+                clear_tsk_thread_flag(task, TIF_BLOCKSTEP);
+        }
+        update_debugctlmsr(debugctl);
+}
+
 /*
  * Enable single or block step.
  */
@@ -169,19 +184,10 @@ static void enable_step(struct task_struct *child, bool block)
          * So no one should try to use debugger block stepping in a program
          * that uses user-mode single stepping itself.
          */
-        if (enable_single_step(child) && block) {
-                unsigned long debugctl = get_debugctlmsr();
-
-                debugctl |= DEBUGCTLMSR_BTF;
-                update_debugctlmsr(debugctl);
-                set_tsk_thread_flag(child, TIF_BLOCKSTEP);
-        } else if (test_tsk_thread_flag(child, TIF_BLOCKSTEP)) {
-                unsigned long debugctl = get_debugctlmsr();
-
-                debugctl &= ~DEBUGCTLMSR_BTF;
-                update_debugctlmsr(debugctl);
-                clear_tsk_thread_flag(child, TIF_BLOCKSTEP);
-        }
+        if (enable_single_step(child) && block)
+                set_task_blockstep(child, true);
+        else if (test_tsk_thread_flag(child, TIF_BLOCKSTEP))
+                set_task_blockstep(child, false);
 }
 
 void user_enable_single_step(struct task_struct *child)
@@ -199,13 +205,8 @@ void user_disable_single_step(struct task_struct *child)
         /*
          * Make sure block stepping (BTF) is disabled.
          */
-        if (test_tsk_thread_flag(child, TIF_BLOCKSTEP)) {
-                unsigned long debugctl = get_debugctlmsr();
-
-                debugctl &= ~DEBUGCTLMSR_BTF;
-                update_debugctlmsr(debugctl);
-                clear_tsk_thread_flag(child, TIF_BLOCKSTEP);
-        }
+        if (test_tsk_thread_flag(child, TIF_BLOCKSTEP))
+                set_task_blockstep(child, false);
 
         /* Always clear TIF_SINGLESTEP... */
         clear_tsk_thread_flag(child, TIF_SINGLESTEP);