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         p = get_kprobe((kprobe_opcode_t *)nip);
  30         if (unlikely(!p) || kprobe_disabled(p))
  31                 goto out;
  32
  33         kcb = get_kprobe_ctlblk();
  34         if (kprobe_running()) {
  35                 kprobes_inc_nmissed_count(p);
  36         } else {
  37                 /*
  38                  * On powerpc, NIP is *before* this instruction for the
  39                  * pre handler
  40                  */
  41                 regs_add_return_ip(regs, -MCOUNT_INSN_SIZE);
  42
  43                 __this_cpu_write(current_kprobe, p);
  44                 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
  45                 if (!p->pre_handler || !p->pre_handler(p, regs)) {
  46                         /*
  47                          * Emulate singlestep (and also recover regs->nip)
  48                          * as if there is a nop
  49                          */
  50                         regs_add_return_ip(regs, MCOUNT_INSN_SIZE);
  51                         if (unlikely(p->post_handler)) {
  52                                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
  53                                 p->post_handler(p, regs, 0);
  54                         }
  55                 }
  56                 /*
  57                  * If pre_handler returns !0, it changes regs->nip. We have to
  58                  * skip emulating post_handler.
  59                  */
  60                 __this_cpu_write(current_kprobe, NULL);
  61         }
  62 out:
  63         ftrace_test_recursion_unlock(bit);
  64 }
  65 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
  66
  67 int arch_prepare_kprobe_ftrace(struct kprobe *p)
  68 {
  69         p->ainsn.insn = NULL;
  70         p->ainsn.boostable = -1;
  71         return 0;
  72 }