From a19b2e3d783964d48d2b494439648e929bcdc976 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Tue, 19 Sep 2017 19:02:20 +0900 Subject: [PATCH] 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 Cc: Alexei Starovoitov Cc: Alexei Starovoitov Cc: Ananth N Mavinakayanahalli Cc: Linus Torvalds Cc: Paul E . McKenney Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/150581534039.32348.11331736206004264553.stgit@devbox Signed-off-by: Ingo Molnar --- arch/x86/kernel/kprobes/ftrace.c | 9 ++------- arch/x86/kernel/kprobes/opt.c | 4 ---- 2 files changed, 2 insertions(+), 11 deletions(-) diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c index bcfee4f69b..8dc0161 100644 --- 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 32c35cb..e941136 100644 --- 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); -- 2.7.4