kprobes/x86: Remove IRQ disabling from ftrace-based/optimized kprobes

Kkprobes don't need to disable IRQs if they are called from the
ftrace/jump trampoline code, because Documentation/kprobes.txt says:

  -----
  Probe handlers are run with preemption disabled.  Depending on the
  architecture and optimization state, handlers may also run with
  interrupts disabled (e.g., kretprobe handlers and optimized kprobe
  handlers run without interrupt disabled on x86/x86-64).
  -----

So let's remove IRQ disabling from those handlers.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/150581534039.32348.11331736206004264553.stgit@devbox
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c
index bcfee4f69b0e5312c78849dfea95dde23e29ca99..8dc0161cec8f470f365220097f9b0f97a252c803 100644 (file)
--- a/arch/x86/kernel/kprobes/ftrace.c
+++ b/arch/x86/kernel/kprobes/ftrace.c
@@ -61,14 +61,11 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
 {
        struct kprobe *p;
        struct kprobe_ctlblk *kcb;
-       unsigned long flags;
-
-       /* Disable irq for emulating a breakpoint and avoiding preempt */
-       local_irq_save(flags);
 
+       /* Preempt is disabled by ftrace */
        p = get_kprobe((kprobe_opcode_t *)ip);
        if (unlikely(!p) || kprobe_disabled(p))
-               goto end;
+               return;
 
        kcb = get_kprobe_ctlblk();
        if (kprobe_running()) {
@@ -91,8 +88,6 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
                 * resets current kprobe, and keep preempt count +1.
                 */
        }
-end:
-       local_irq_restore(flags);
 }
 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
 

diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index 32c35cb3550cf1605d78b240b29b7ed4e0af06b8..e941136e24d834b20b4c15670f0d7a9fd6def1a1 100644 (file)
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -154,13 +154,10 @@ STACK_FRAME_NON_STANDARD(optprobe_template_func);
 static void
 optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
 {
-       unsigned long flags;
-
        /* This is possible if op is under delayed unoptimizing */
        if (kprobe_disabled(&op->kp))
                return;
 
-       local_irq_save(flags);
        preempt_disable();
        if (kprobe_running()) {
                kprobes_inc_nmissed_count(&op->kp);
@@ -182,7 +179,6 @@ optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
                __this_cpu_write(current_kprobe, NULL);
        }
        preempt_enable_no_resched();
-       local_irq_restore(flags);
 }
 NOKPROBE_SYMBOL(optimized_callback);