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/kprobes.c b/arch/x86/kernel/kprobes.c
index 7a880ad..f2f56c0 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -422,12 +422,22 @@
static void __kprobes clear_btf(void)
{
- /* XXX */
+ if (test_thread_flag(TIF_BLOCKSTEP)) {
+ unsigned long debugctl = get_debugctlmsr();
+
+ debugctl &= ~DEBUGCTLMSR_BTF;
+ update_debugctlmsr(debugctl);
+ }
}
static void __kprobes restore_btf(void)
{
- /* XXX */
+ if (test_thread_flag(TIF_BLOCKSTEP)) {
+ unsigned long debugctl = get_debugctlmsr();
+
+ debugctl |= DEBUGCTLMSR_BTF;
+ update_debugctlmsr(debugctl);
+ }
}
void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,