arch/powerpc/kernel/kprobes-ftrace.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Dynamic Ftrace based Kprobes Optimization
   4  *
   5  * Copyright (C) Hitachi Ltd., 2012
   6  * Copyright 2016 Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
   7  *                IBM Corporation
   8  */
   9 #include <linux/kprobes.h>
  10 #include <linux/ptrace.h>
  11 #include <linux/hardirq.h>
  12 #include <linux/preempt.h>
  13 #include <linux/ftrace.h>
  14
  15 /* Ftrace callback handler for kprobes */
  16 void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip,
  17                            struct ftrace_ops *ops, struct pt_regs *regs)
  18 {
  19         struct kprobe *p;
  20         struct kprobe_ctlblk *kcb;
  21
  22         p = get_kprobe((kprobe_opcode_t *)nip);
  23         if (unlikely(!p) || kprobe_disabled(p))
  24                 return;
  25
  26         kcb = get_kprobe_ctlblk();
  27         if (kprobe_running()) {
  28                 kprobes_inc_nmissed_count(p);
  29         } else {
  30                 /*
  31                  * On powerpc, NIP is *before* this instruction for the
  32                  * pre handler
  33                  */
  34                 regs->nip -= MCOUNT_INSN_SIZE;
  35
  36                 __this_cpu_write(current_kprobe, p);
  37                 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
  38                 if (!p->pre_handler || !p->pre_handler(p, regs)) {
  39                         /*
  40                          * Emulate singlestep (and also recover regs->nip)
  41                          * as if there is a nop
  42                          */
  43                         regs->nip += MCOUNT_INSN_SIZE;
  44                         if (unlikely(p->post_handler)) {
  45                                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
  46                                 p->post_handler(p, regs, 0);
  47                         }
  48                 }
  49                 /*
  50                  * If pre_handler returns !0, it changes regs->nip. We have to
  51                  * skip emulating post_handler.
  52                  */
  53                 __this_cpu_write(current_kprobe, NULL);
  54         }
  55 }
  56 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
  57
  58 int arch_prepare_kprobe_ftrace(struct kprobe *p)
  59 {
  60         p->ainsn.insn = NULL;
  61         p->ainsn.boostable = -1;
  62         return 0;
  63 }