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 <[email protected]>
   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         if (unlikely(kprobe_ftrace_disabled))
  25                 return;
  26
  27         bit = ftrace_test_recursion_trylock(nip, parent_nip);
  28         if (bit < 0)
  29                 return;
  30
  31         regs = ftrace_get_regs(fregs);
  32         p = get_kprobe((kprobe_opcode_t *)nip);
  33         if (unlikely(!p) || kprobe_disabled(p))
  34                 goto out;
  35
  36         kcb = get_kprobe_ctlblk();
  37         if (kprobe_running()) {
  38                 kprobes_inc_nmissed_count(p);
  39         } else {
  40                 /*
  41                  * On powerpc, NIP is *before* this instruction for the
  42                  * pre handler
  43                  */
  44                 regs_add_return_ip(regs, -MCOUNT_INSN_SIZE);
  45
  46                 __this_cpu_write(current_kprobe, p);
  47                 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
  48                 if (!p->pre_handler || !p->pre_handler(p, regs)) {
  49                         /*
  50                          * Emulate singlestep (and also recover regs->nip)
  51                          * as if there is a nop
  52                          */
  53                         regs_add_return_ip(regs, MCOUNT_INSN_SIZE);
  54                         if (unlikely(p->post_handler)) {
  55                                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
  56                                 p->post_handler(p, regs, 0);
  57                         }
  58                 }
  59                 /*
  60                  * If pre_handler returns !0, it changes regs->nip. We have to
  61                  * skip emulating post_handler.
  62                  */
  63                 __this_cpu_write(current_kprobe, NULL);
  64         }
  65 out:
  66         ftrace_test_recursion_unlock(bit);
  67 }
  68 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
  69
  70 int arch_prepare_kprobe_ftrace(struct kprobe *p)
  71 {
  72         p->ainsn.insn = NULL;
  73         p->ainsn.boostable = -1;
  74         return 0;
  75 }