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dd0bb688ea
Error injection is sloppy and very ad-hoc. BPF could fill this niche perfectly with it's kprobe functionality. We could make sure errors are only triggered in specific call chains that we care about with very specific situations. Accomplish this with the bpf_override_funciton helper. This will modify the probe'd callers return value to the specified value and set the PC to an override function that simply returns, bypassing the originally probed function. This gives us a nice clean way to implement systematic error injection for all of our code paths. Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Josef Bacik <jbacik@fb.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: David S. Miller <davem@davemloft.net>
113 lines
3 KiB
C
113 lines
3 KiB
C
/*
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* Dynamic Ftrace based Kprobes Optimization
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright (C) Hitachi Ltd., 2012
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*/
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#include <linux/kprobes.h>
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#include <linux/ptrace.h>
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#include <linux/hardirq.h>
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#include <linux/preempt.h>
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#include <linux/ftrace.h>
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#include "common.h"
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static nokprobe_inline
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int __skip_singlestep(struct kprobe *p, struct pt_regs *regs,
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struct kprobe_ctlblk *kcb, unsigned long orig_ip)
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{
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/*
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* Emulate singlestep (and also recover regs->ip)
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* as if there is a 5byte nop
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*/
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regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE;
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if (unlikely(p->post_handler)) {
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kcb->kprobe_status = KPROBE_HIT_SSDONE;
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p->post_handler(p, regs, 0);
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}
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__this_cpu_write(current_kprobe, NULL);
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if (orig_ip)
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regs->ip = orig_ip;
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return 1;
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}
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int skip_singlestep(struct kprobe *p, struct pt_regs *regs,
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struct kprobe_ctlblk *kcb)
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{
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if (kprobe_ftrace(p))
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return __skip_singlestep(p, regs, kcb, 0);
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else
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return 0;
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}
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NOKPROBE_SYMBOL(skip_singlestep);
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/* Ftrace callback handler for kprobes */
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void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
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struct ftrace_ops *ops, struct pt_regs *regs)
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{
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struct kprobe *p;
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struct kprobe_ctlblk *kcb;
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unsigned long flags;
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/* Disable irq for emulating a breakpoint and avoiding preempt */
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local_irq_save(flags);
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p = get_kprobe((kprobe_opcode_t *)ip);
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if (unlikely(!p) || kprobe_disabled(p))
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goto end;
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kcb = get_kprobe_ctlblk();
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if (kprobe_running()) {
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kprobes_inc_nmissed_count(p);
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} else {
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unsigned long orig_ip = regs->ip;
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/* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
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regs->ip = ip + sizeof(kprobe_opcode_t);
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__this_cpu_write(current_kprobe, p);
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kcb->kprobe_status = KPROBE_HIT_ACTIVE;
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if (!p->pre_handler || !p->pre_handler(p, regs))
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__skip_singlestep(p, regs, kcb, orig_ip);
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/*
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* If pre_handler returns !0, it sets regs->ip and
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* resets current kprobe.
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*/
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}
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end:
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local_irq_restore(flags);
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}
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NOKPROBE_SYMBOL(kprobe_ftrace_handler);
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int arch_prepare_kprobe_ftrace(struct kprobe *p)
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{
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p->ainsn.insn = NULL;
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p->ainsn.boostable = false;
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return 0;
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}
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asmlinkage void override_func(void);
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asm(
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".type override_func, @function\n"
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"override_func:\n"
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" ret\n"
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".size override_func, .-override_func\n"
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);
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void arch_ftrace_kprobe_override_function(struct pt_regs *regs)
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{
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regs->ip = (unsigned long)&override_func;
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}
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NOKPROBE_SYMBOL(arch_ftrace_kprobe_override_function);
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