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  */
  33 int __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
  43 static nokprobe_inline
  44 int __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
  62 int 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 }
  70 NOKPROBE_SYMBOL(skip_singlestep);
  71
  72 /* Ftrace callback handler for kprobes */
  73 void 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         }
 110 end:
 111         preempt_enable_no_resched();
 112 }
 113 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
 114
 115 int arch_prepare_kprobe_ftrace(struct kprobe *p)
 116 {
 117         p->ainsn.insn = NULL;
 118         p->ainsn.boostable = -1;
 119         return 0;
 120 }