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| 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 | +} |
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