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 ftrace_regs *fregs)
  18 {
  19         struct kprobe *p;
  20         struct kprobe_ctlblk *kcb;
  21         struct pt_regs *regs;
  22         int bit;
  23
  24         bit = ftrace_test_recursion_trylock(nip, parent_nip);
  25         if (bit < 0)
  26                 return;
  27
  28         regs = ftrace_get_regs(fregs);
  29         preempt_disable_notrace();
  30         p = get_kprobe((kprobe_opcode_t *)nip);
  31         if (unlikely(!p) || kprobe_disabled(p))
  32                 goto out;
  33
  34         kcb = get_kprobe_ctlblk();
  35         if (kprobe_running()) {
  36                 kprobes_inc_nmissed_count(p);
  37         } else {
  38                 /*
  39                  * On powerpc, NIP is *before* this instruction for the
  40                  * pre handler
  41                  */
  42                 regs->nip -= MCOUNT_INSN_SIZE;
  43
  44                 __this_cpu_write(current_kprobe, p);
  45                 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
  46                 if (!p->pre_handler || !p->pre_handler(p, regs)) {
  47                         /*
  48                          * Emulate singlestep (and also recover regs->nip)
  49                          * as if there is a nop
  50                          */
  51                         regs->nip += 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                 }
  57                 /*
  58                  * If pre_handler returns !0, it changes regs->nip. We have to
  59                  * skip emulating post_handler.
  60                  */
  61                 __this_cpu_write(current_kprobe, NULL);
  62         }
  63 out:
  64         preempt_enable_notrace();
  65         ftrace_test_recursion_unlock(bit);
  66 }
  67 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
  68
  69 int arch_prepare_kprobe_ftrace(struct kprobe *p)
  70 {
  71         p->ainsn.insn = NULL;
  72         p->ainsn.boostable = -1;
  73         return 0;
  74 }