LXR linux/arch/powerpc/kernel/kprobes-ftrace.c

   1/*
   2 * Dynamic Ftrace based Kprobes Optimization
   3 *
   4 * This program is free software; you can redistribute it and/or modify
   5 * it under the terms of the GNU General Public License as published by
   6 * the Free Software Foundation; either version 2 of the License, or
   7 * (at your option) any later version.
   8 *
   9 * This program is distributed in the hope that it will be useful,
  10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 * GNU General Public License for more details.
  13 *
  14 * You should have received a copy of the GNU General Public License
  15 * along with this program; if not, write to the Free Software
  16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17 *
  18 * Copyright (C) Hitachi Ltd., 2012
  19 * Copyright 2016 Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
  20 *                IBM Corporation
  21 */
  22#include <linux/kprobes.h>
  23#include <linux/ptrace.h>
  24#include <linux/hardirq.h>
  25#include <linux/preempt.h>
  26#include <linux/ftrace.h>
  27
  28/*
  29 * This is called from ftrace code after invoking registered handlers to
  30 * disambiguate regs->nip changes done by jprobes and livepatch. We check if
  31 * there is an active jprobe at the provided address (mcount location).
  32 */
  33int __is_active_jprobe(unsigned long addr)
  34{
  35        if (!preemptible()) {
  36                struct kprobe *p = raw_cpu_read(current_kprobe);
  37                return (p && (unsigned long)p->addr == addr) ? 1 : 0;
  38        }
  39
  40        return 0;
  41}
  42
  43static nokprobe_inline
  44int __skip_singlestep(struct kprobe *p, struct pt_regs *regs,
  45                      struct kprobe_ctlblk *kcb, unsigned long orig_nip)
  46{
  47        /*
  48         * Emulate singlestep (and also recover regs->nip)
  49         * as if there is a nop
  50         */
  51        regs->nip = (unsigned long)p->addr + MCOUNT_INSN_SIZE;
  52        if (unlikely(p->post_handler)) {
  53                kcb->kprobe_status = KPROBE_HIT_SSDONE;
  54                p->post_handler(p, regs, 0);
  55        }
  56        __this_cpu_write(current_kprobe, NULL);
  57        if (orig_nip)
  58                regs->nip = orig_nip;
  59        return 1;
  60}
  61
  62int skip_singlestep(struct kprobe *p, struct pt_regs *regs,
  63                    struct kprobe_ctlblk *kcb)
  64{
  65        if (kprobe_ftrace(p))
  66                return __skip_singlestep(p, regs, kcb, 0);
  67        else
  68                return 0;
  69}
  70NOKPROBE_SYMBOL(skip_singlestep);
  71
  72/* Ftrace callback handler for kprobes */
  73void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip,
  74                           struct ftrace_ops *ops, struct pt_regs *regs)
  75{
  76        struct kprobe *p;
  77        struct kprobe_ctlblk *kcb;
  78
  79        preempt_disable();
  80
  81        p = get_kprobe((kprobe_opcode_t *)nip);
  82        if (unlikely(!p) || kprobe_disabled(p))
  83                goto end;
  84
  85        kcb = get_kprobe_ctlblk();
  86        if (kprobe_running()) {
  87                kprobes_inc_nmissed_count(p);
  88        } else {
  89                unsigned long orig_nip = regs->nip;
  90
  91                /*
  92                 * On powerpc, NIP is *before* this instruction for the
  93                 * pre handler
  94                 */
  95                regs->nip -= MCOUNT_INSN_SIZE;
  96
  97                __this_cpu_write(current_kprobe, p);
  98                kcb->kprobe_status = KPROBE_HIT_ACTIVE;
  99                if (!p->pre_handler || !p->pre_handler(p, regs))
 100                        __skip_singlestep(p, regs, kcb, orig_nip);
 101                else {
 102                        /*
 103                         * If pre_handler returns !0, it sets regs->nip and
 104                         * resets current kprobe. In this case, we should not
 105                         * re-enable preemption.
 106                         */
 107                        return;
 108                }
 109        }
 110end:
 111        preempt_enable_no_resched();
 112}
 113NOKPROBE_SYMBOL(kprobe_ftrace_handler);
 114
 115int arch_prepare_kprobe_ftrace(struct kprobe *p)
 116{
 117        p->ainsn.insn = NULL;
 118        p->ainsn.boostable = -1;
 119        return 0;
 120}
 121