x86: debugctlmsr arch_has_block_step
This implements user-mode step-until-branch on x86 using the BTF bit
in MSR_IA32_DEBUGCTLMSR. It's just like single-step, only less so.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/traps_32.c b/arch/x86/kernel/traps_32.c
index 02d1e1e..9b0bbd5 100644
--- a/arch/x86/kernel/traps_32.c
+++ b/arch/x86/kernel/traps_32.c
@@ -837,6 +837,12 @@
get_debugreg(condition, 6);
+ /*
+ * The processor cleared BTF, so don't mark that we need it set.
+ */
+ clear_tsk_thread_flag(tsk, TIF_DEBUGCTLMSR);
+ tsk->thread.debugctlmsr = 0;
+
if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code,
SIGTRAP) == NOTIFY_STOP)
return;