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Commit 0f94eb63 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Ingo Molnar
Browse files

kprobes/x86: Boost probes when reentering 



Integrate prepare_singlestep() into setup_singlestep() to boost
up reenter probes, if possible.

Signed-off-by: default avatarMasami Hiramatsu <mhiramat@redhat.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Anders Kaseorg <andersk@ksplice.com>
Cc: Tim Abbott <tabbott@ksplice.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
LKML-Reference: <20100225133423.6725.12071.stgit@localhost6.localdomain6>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent b2be84df

arch/x86/kernel/kprobes.c

+26 −22
Original line number Diff line number Diff line
@@ -406,18 +406,6 @@ static void __kprobes restore_btf(void) 
		update_debugctlmsr(current->thread.debugctlmsr);

}



static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)

{

	clear_btf();

	regs->flags |= X86_EFLAGS_TF;

	regs->flags &= ~X86_EFLAGS_IF;

	/* single step inline if the instruction is an int3 */

	if (p->opcode == BREAKPOINT_INSTRUCTION)

		regs->ip = (unsigned long)p->addr;

	else

		regs->ip = (unsigned long)p->ainsn.insn;

}



void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,

				      struct pt_regs *regs)

{
@@ -430,19 +418,38 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, 
}



static void __kprobes setup_singlestep(struct kprobe *p, struct pt_regs *regs,

				       struct kprobe_ctlblk *kcb)

				       struct kprobe_ctlblk *kcb, int reenter)

{

#if !defined(CONFIG_PREEMPT)

	if (p->ainsn.boostable == 1 && !p->post_handler) {

		/* Boost up -- we can execute copied instructions directly */

		if (!reenter)

			reset_current_kprobe();

		/*

		 * Reentering boosted probe doesn't reset current_kprobe,

		 * nor set current_kprobe, because it doesn't use single

		 * stepping.

		 */

		regs->ip = (unsigned long)p->ainsn.insn;

		preempt_enable_no_resched();

		return;

	}

#endif

	prepare_singlestep(p, regs);

	if (reenter) {

		save_previous_kprobe(kcb);

		set_current_kprobe(p, regs, kcb);

		kcb->kprobe_status = KPROBE_REENTER;

	} else

		kcb->kprobe_status = KPROBE_HIT_SS;

	/* Prepare real single stepping */

	clear_btf();

	regs->flags |= X86_EFLAGS_TF;

	regs->flags &= ~X86_EFLAGS_IF;

	/* single step inline if the instruction is an int3 */

	if (p->opcode == BREAKPOINT_INSTRUCTION)

		regs->ip = (unsigned long)p->addr;

	else

		regs->ip = (unsigned long)p->ainsn.insn;

}



/*
@@ -456,11 +463,8 @@ static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs, 
	switch (kcb->kprobe_status) {

	case KPROBE_HIT_SSDONE:

	case KPROBE_HIT_ACTIVE:

		save_previous_kprobe(kcb);

		set_current_kprobe(p, regs, kcb);

		kprobes_inc_nmissed_count(p);

		prepare_singlestep(p, regs);

		kcb->kprobe_status = KPROBE_REENTER;

		setup_singlestep(p, regs, kcb, 1);

		break;

	case KPROBE_HIT_SS:

		/* A probe has been hit in the codepath leading up to, or just
@@ -535,13 +539,13 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) 
			 * more here.

			 */

			if (!p->pre_handler || !p->pre_handler(p, regs))

				setup_singlestep(p, regs, kcb);

				setup_singlestep(p, regs, kcb, 0);

			return 1;

		}

	} else if (kprobe_running()) {

		p = __get_cpu_var(current_kprobe);

		if (p->break_handler && p->break_handler(p, regs)) {

			setup_singlestep(p, regs, kcb);

			setup_singlestep(p, regs, kcb, 0);

			return 1;

		}

	} /* else: not a kprobe fault; let the kernel handle it */