| Naveen N. Rao | ead514d | 2017-04-19 18:22:26 +0530 | [diff] [blame] | 1 | /* |
| 2 | * Dynamic Ftrace based Kprobes Optimization |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or modify |
| 5 | * it under the terms of the GNU General Public License as published by |
| 6 | * the Free Software Foundation; either version 2 of the License, or |
| 7 | * (at your option) any later version. |
| 8 | * |
| 9 | * This program is distributed in the hope that it will be useful, |
| 10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 12 | * GNU General Public License for more details. |
| 13 | * |
| 14 | * You should have received a copy of the GNU General Public License |
| 15 | * along with this program; if not, write to the Free Software |
| 16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 17 | * |
| 18 | * Copyright (C) Hitachi Ltd., 2012 |
| 19 | * Copyright 2016 Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> |
| 20 | * IBM Corporation |
| 21 | */ |
| 22 | #include <linux/kprobes.h> |
| 23 | #include <linux/ptrace.h> |
| 24 | #include <linux/hardirq.h> |
| 25 | #include <linux/preempt.h> |
| 26 | #include <linux/ftrace.h> |
| 27 | |
| 28 | static nokprobe_inline |
| 29 | int __skip_singlestep(struct kprobe *p, struct pt_regs *regs, |
| 30 | struct kprobe_ctlblk *kcb, unsigned long orig_nip) |
| 31 | { |
| 32 | /* |
| 33 | * Emulate singlestep (and also recover regs->nip) |
| 34 | * as if there is a nop |
| 35 | */ |
| 36 | regs->nip = (unsigned long)p->addr + MCOUNT_INSN_SIZE; |
| 37 | if (unlikely(p->post_handler)) { |
| 38 | kcb->kprobe_status = KPROBE_HIT_SSDONE; |
| 39 | p->post_handler(p, regs, 0); |
| 40 | } |
| 41 | __this_cpu_write(current_kprobe, NULL); |
| 42 | if (orig_nip) |
| 43 | regs->nip = orig_nip; |
| 44 | return 1; |
| 45 | } |
| 46 | |
| 47 | int skip_singlestep(struct kprobe *p, struct pt_regs *regs, |
| 48 | struct kprobe_ctlblk *kcb) |
| 49 | { |
| 50 | if (kprobe_ftrace(p)) |
| 51 | return __skip_singlestep(p, regs, kcb, 0); |
| 52 | else |
| 53 | return 0; |
| 54 | } |
| 55 | NOKPROBE_SYMBOL(skip_singlestep); |
| 56 | |
| 57 | /* Ftrace callback handler for kprobes */ |
| 58 | void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip, |
| 59 | struct ftrace_ops *ops, struct pt_regs *regs) |
| 60 | { |
| 61 | struct kprobe *p; |
| 62 | struct kprobe_ctlblk *kcb; |
| 63 | unsigned long flags; |
| 64 | |
| 65 | /* Disable irq for emulating a breakpoint and avoiding preempt */ |
| 66 | local_irq_save(flags); |
| 67 | hard_irq_disable(); |
| 68 | |
| 69 | p = get_kprobe((kprobe_opcode_t *)nip); |
| 70 | if (unlikely(!p) || kprobe_disabled(p)) |
| 71 | goto end; |
| 72 | |
| 73 | kcb = get_kprobe_ctlblk(); |
| 74 | if (kprobe_running()) { |
| 75 | kprobes_inc_nmissed_count(p); |
| 76 | } else { |
| 77 | unsigned long orig_nip = regs->nip; |
| 78 | |
| 79 | /* |
| 80 | * On powerpc, NIP is *before* this instruction for the |
| 81 | * pre handler |
| 82 | */ |
| 83 | regs->nip -= MCOUNT_INSN_SIZE; |
| 84 | |
| 85 | __this_cpu_write(current_kprobe, p); |
| 86 | kcb->kprobe_status = KPROBE_HIT_ACTIVE; |
| 87 | if (!p->pre_handler || !p->pre_handler(p, regs)) |
| 88 | __skip_singlestep(p, regs, kcb, orig_nip); |
| 89 | /* |
| 90 | * If pre_handler returns !0, it sets regs->nip and |
| 91 | * resets current kprobe. |
| 92 | */ |
| 93 | } |
| 94 | end: |
| 95 | local_irq_restore(flags); |
| 96 | } |
| 97 | NOKPROBE_SYMBOL(kprobe_ftrace_handler); |
| 98 | |
| 99 | int arch_prepare_kprobe_ftrace(struct kprobe *p) |
| 100 | { |
| 101 | p->ainsn.insn = NULL; |
| 102 | p->ainsn.boostable = -1; |
| 103 | return 0; |
| 104 | } |
