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Commit e6349a95 authored by Ananth N Mavinakayanahalli's avatar Ananth N Mavinakayanahalli Committed by Paul Mackerras
Browse files

[POWERPC] kprobes: Eliminate sstep exception if instruction can be emulated 



For cases when probes are placed on instructions that can be emulated,
don't take the single-step exception.

Signed-off-by: default avatarAnanth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
parent 6888199f

arch/powerpc/kernel/kprobes.c

+35 −1
Original line number Diff line number Diff line
@@ -59,12 +59,14 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p) 
	}



	if (!ret) {

		memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));

		memcpy(p->ainsn.insn, p->addr,

				MAX_INSN_SIZE * sizeof(kprobe_opcode_t));

		p->opcode = *p->addr;

		flush_icache_range((unsigned long)p->ainsn.insn,

			(unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));

	}



	p->ainsn.boostable = 0;

	return ret;

}
@@ -232,6 +234,38 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) 
		return 1;



ss_probe:

	if (p->ainsn.boostable >= 0) {

		unsigned int insn = *p->ainsn.insn;



		/* regs->nip is also adjusted if emulate_step returns 1 */

		ret = emulate_step(regs, insn);

		if (ret > 0) {

			/*

			 * Once this instruction has been boosted

			 * successfully, set the boostable flag

			 */

			if (unlikely(p->ainsn.boostable == 0))

				p->ainsn.boostable = 1;



			if (p->post_handler)

				p->post_handler(p, regs, 0);



			kcb->kprobe_status = KPROBE_HIT_SSDONE;

			reset_current_kprobe();

			preempt_enable_no_resched();

			return 1;

		} else if (ret < 0) {

			/*

			 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.

			 * So, we should never get here... but, its still

			 * good to catch them, just in case...

			 */

			printk("Can't step on instruction %x\n", insn);

			BUG();

		} else if (ret == 0)

			/* This instruction can't be boosted */

			p->ainsn.boostable = -1;

	}

	prepare_singlestep(p, regs);

	kcb->kprobe_status = KPROBE_HIT_SS;

	return 1;

include/asm-powerpc/kprobes.h

+5 −0
Original line number Diff line number Diff line
@@ -87,6 +87,11 @@ extern void arch_remove_kprobe(struct kprobe *p); 
struct arch_specific_insn {

	/* copy of original instruction */

	kprobe_opcode_t *insn;

	/*

	 * Set in kprobes code, initially to 0. If the instruction can be

	 * eumulated, this is set to 1, if not, to -1.

	 */

	int boostable;

};



struct prev_kprobe {