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>

diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c
index c346d11..7a51498 100644 (file)
--- 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);