x86, ptrace: Fix block-step
Implement ptrace-block-step using TIF_BLOCKSTEP which will set
DEBUGCTLMSR_BTF when set for a task while preserving any other
DEBUGCTLMSR bits.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100325135414.017536066@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c
index 7beba07..58de45e 100644
--- a/arch/x86/kernel/step.c
+++ b/arch/x86/kernel/step.c
@@ -169,9 +169,19 @@
* So noone should try to use debugger block stepping in a program
* that uses user-mode single stepping itself.
*/
- if (!enable_single_step(child))
- return;
- /* XXX */
+ 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);
+ }
}
void user_enable_single_step(struct task_struct *child)
@@ -189,7 +199,13 @@
/*
* Make sure block stepping (BTF) is disabled.
*/
- /* XXX */
+ 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);
+ }
/* Always clear TIF_SINGLESTEP... */
clear_tsk_thread_flag(child, TIF_SINGLESTEP);