[PATCH 3.4 139/214] ptrace/x86: Introduce set_task_blockstep() helper

Greg Kroah-Hartman
2014-06-05T04:42:47Z

From: Oleg Nesterov <oleg@redhat.com>

commit 848e8f5f0ad3169560c516fff6471be65f76e69f upstream.

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Rui Xiang <rui.xiang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/kernel/step.c | 41 +++++++++++++++++++++--------------------
1 file changed, 21 insertions(+), 20 deletions(-)

--- a/arch/x86/kernel/step.c
+++ b/arch/x86/kernel/step.c
@@ -157,6 +157,21 @@ static int enable_single_step(struct tas
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_stru
* 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 tas
/*
* 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);