arch/x86/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  */
   7 #include <linux/kprobes.h>
   8 #include <linux/ptrace.h>
   9 #include <linux/hardirq.h>
  10 #include <linux/preempt.h>
  11 #include <linux/ftrace.h>
  12
  13 #include "common.h"
  14
  15 /* Ftrace callback handler for kprobes -- called under preempt disabled */
  16 void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
  17                            struct ftrace_ops *ops, struct ftrace_regs *fregs)
  18 {
  19         struct pt_regs *regs = ftrace_get_regs(fregs);
  20         struct kprobe *p;
  21         struct kprobe_ctlblk *kcb;
  22         int bit;
  23
  24         bit = ftrace_test_recursion_trylock(ip, parent_ip);
  25         if (bit < 0)
  26                 return;
  27
  28         p = get_kprobe((kprobe_opcode_t *)ip);
  29         if (unlikely(!p) || kprobe_disabled(p))
  30                 goto out;
  31
  32         kcb = get_kprobe_ctlblk();
  33         if (kprobe_running()) {
  34                 kprobes_inc_nmissed_count(p);
  35         } else {
  36                 unsigned long orig_ip = regs->ip;
  37                 /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
  38                 regs->ip = ip + sizeof(kprobe_opcode_t);
  39
  40                 __this_cpu_write(current_kprobe, p);
  41                 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
  42                 if (!p->pre_handler || !p->pre_handler(p, regs)) {
  43                         /*
  44                          * Emulate singlestep (and also recover regs->ip)
  45                          * as if there is a 5byte nop
  46                          */
  47                         regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE;
  48                         if (unlikely(p->post_handler)) {
  49                                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
  50                                 p->post_handler(p, regs, 0);
  51                         }
  52                         regs->ip = orig_ip;
  53                 }
  54                 /*
  55                  * If pre_handler returns !0, it changes regs->ip. We have to
  56                  * skip emulating post_handler.
  57                  */
  58                 __this_cpu_write(current_kprobe, NULL);
  59         }
  60 out:
  61         ftrace_test_recursion_unlock(bit);
  62 }
  63 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
  64
  65 int arch_prepare_kprobe_ftrace(struct kprobe *p)
  66 {
  67         p->ainsn.insn = NULL;
  68         p->ainsn.boostable = false;
  69         return 0;
  70 }