![Keshavamurthy Anil S](/assets/img/avatar_default.png)
There is a window where a probe gets removed right after the probe is hit on some different cpu. In this case probe handlers can't find a matching probe instance related to break address. In this case we need to read the original instruction at break address to see if that is not a break/int3 instruction and recover safely. Previous code had a bug where we were not checking for the above race in case of reentrant probes and the below patch fixes this race. Tested on IA64, Powerpc, x86_64. Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
469 lines
12 KiB
C
469 lines
12 KiB
C
/*
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* Kernel Probes (KProbes)
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* arch/ppc64/kernel/kprobes.c
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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) IBM Corporation, 2002, 2004
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*
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* 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
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* Probes initial implementation ( includes contributions from
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* Rusty Russell).
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* 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
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* interface to access function arguments.
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* 2004-Nov Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
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* for PPC64
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*/
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#include <linux/config.h>
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#include <linux/kprobes.h>
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#include <linux/ptrace.h>
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#include <linux/preempt.h>
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#include <asm/cacheflush.h>
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#include <asm/kdebug.h>
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#include <asm/sstep.h>
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DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
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DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
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int __kprobes arch_prepare_kprobe(struct kprobe *p)
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{
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int ret = 0;
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kprobe_opcode_t insn = *p->addr;
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if ((unsigned long)p->addr & 0x03) {
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printk("Attempt to register kprobe at an unaligned address\n");
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ret = -EINVAL;
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} else if (IS_MTMSRD(insn) || IS_RFID(insn)) {
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printk("Cannot register a kprobe on rfid or mtmsrd\n");
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ret = -EINVAL;
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}
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/* insn must be on a special executable page on ppc64 */
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if (!ret) {
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p->ainsn.insn = get_insn_slot();
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if (!p->ainsn.insn)
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ret = -ENOMEM;
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}
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if (!ret) {
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memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
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p->opcode = *p->addr;
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}
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return ret;
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}
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void __kprobes arch_arm_kprobe(struct kprobe *p)
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{
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*p->addr = BREAKPOINT_INSTRUCTION;
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flush_icache_range((unsigned long) p->addr,
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(unsigned long) p->addr + sizeof(kprobe_opcode_t));
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}
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void __kprobes arch_disarm_kprobe(struct kprobe *p)
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{
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*p->addr = p->opcode;
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flush_icache_range((unsigned long) p->addr,
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(unsigned long) p->addr + sizeof(kprobe_opcode_t));
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}
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void __kprobes arch_remove_kprobe(struct kprobe *p)
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{
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down(&kprobe_mutex);
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free_insn_slot(p->ainsn.insn);
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up(&kprobe_mutex);
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}
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static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
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{
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kprobe_opcode_t insn = *p->ainsn.insn;
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regs->msr |= MSR_SE;
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/* single step inline if it is a trap variant */
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if (is_trap(insn))
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regs->nip = (unsigned long)p->addr;
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else
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regs->nip = (unsigned long)p->ainsn.insn;
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}
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static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
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{
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kcb->prev_kprobe.kp = kprobe_running();
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kcb->prev_kprobe.status = kcb->kprobe_status;
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kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
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}
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static inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
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{
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__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
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kcb->kprobe_status = kcb->prev_kprobe.status;
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kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
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}
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static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
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struct kprobe_ctlblk *kcb)
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{
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__get_cpu_var(current_kprobe) = p;
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kcb->kprobe_saved_msr = regs->msr;
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}
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/* Called with kretprobe_lock held */
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void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
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struct pt_regs *regs)
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{
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struct kretprobe_instance *ri;
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if ((ri = get_free_rp_inst(rp)) != NULL) {
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ri->rp = rp;
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ri->task = current;
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ri->ret_addr = (kprobe_opcode_t *)regs->link;
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/* Replace the return addr with trampoline addr */
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regs->link = (unsigned long)kretprobe_trampoline;
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add_rp_inst(ri);
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} else {
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rp->nmissed++;
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}
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}
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static inline int kprobe_handler(struct pt_regs *regs)
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{
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struct kprobe *p;
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int ret = 0;
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unsigned int *addr = (unsigned int *)regs->nip;
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struct kprobe_ctlblk *kcb;
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/*
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* We don't want to be preempted for the entire
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* duration of kprobe processing
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*/
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preempt_disable();
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kcb = get_kprobe_ctlblk();
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/* Check we're not actually recursing */
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if (kprobe_running()) {
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p = get_kprobe(addr);
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if (p) {
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kprobe_opcode_t insn = *p->ainsn.insn;
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if (kcb->kprobe_status == KPROBE_HIT_SS &&
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is_trap(insn)) {
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regs->msr &= ~MSR_SE;
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regs->msr |= kcb->kprobe_saved_msr;
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goto no_kprobe;
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}
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/* We have reentered the kprobe_handler(), since
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* another probe was hit while within the handler.
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* We here save the original kprobes variables and
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* just single step on the instruction of the new probe
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* without calling any user handlers.
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*/
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save_previous_kprobe(kcb);
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set_current_kprobe(p, regs, kcb);
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kcb->kprobe_saved_msr = regs->msr;
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kprobes_inc_nmissed_count(p);
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prepare_singlestep(p, regs);
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kcb->kprobe_status = KPROBE_REENTER;
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return 1;
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} else {
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if (*addr != BREAKPOINT_INSTRUCTION) {
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/* If trap variant, then it belongs not to us */
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kprobe_opcode_t cur_insn = *addr;
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if (is_trap(cur_insn))
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goto no_kprobe;
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/* The breakpoint instruction was removed by
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* another cpu right after we hit, no further
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* handling of this interrupt is appropriate
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*/
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ret = 1;
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goto no_kprobe;
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}
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p = __get_cpu_var(current_kprobe);
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if (p->break_handler && p->break_handler(p, regs)) {
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goto ss_probe;
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}
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}
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goto no_kprobe;
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}
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p = get_kprobe(addr);
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if (!p) {
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if (*addr != BREAKPOINT_INSTRUCTION) {
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/*
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* PowerPC has multiple variants of the "trap"
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* instruction. If the current instruction is a
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* trap variant, it could belong to someone else
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*/
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kprobe_opcode_t cur_insn = *addr;
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if (is_trap(cur_insn))
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goto no_kprobe;
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/*
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* The breakpoint instruction was removed right
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* after we hit it. Another cpu has removed
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* either a probepoint or a debugger breakpoint
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* at this address. In either case, no further
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* handling of this interrupt is appropriate.
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*/
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ret = 1;
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}
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/* Not one of ours: let kernel handle it */
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goto no_kprobe;
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}
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kcb->kprobe_status = KPROBE_HIT_ACTIVE;
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set_current_kprobe(p, regs, kcb);
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if (p->pre_handler && p->pre_handler(p, regs))
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/* handler has already set things up, so skip ss setup */
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return 1;
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ss_probe:
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prepare_singlestep(p, regs);
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kcb->kprobe_status = KPROBE_HIT_SS;
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return 1;
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no_kprobe:
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preempt_enable_no_resched();
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return ret;
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}
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/*
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* Function return probe trampoline:
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* - init_kprobes() establishes a probepoint here
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* - When the probed function returns, this probe
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* causes the handlers to fire
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*/
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void kretprobe_trampoline_holder(void)
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{
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asm volatile(".global kretprobe_trampoline\n"
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"kretprobe_trampoline:\n"
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"nop\n");
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}
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/*
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* Called when the probe at kretprobe trampoline is hit
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*/
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int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
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{
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struct kretprobe_instance *ri = NULL;
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struct hlist_head *head;
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struct hlist_node *node, *tmp;
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unsigned long flags, orig_ret_address = 0;
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unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
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spin_lock_irqsave(&kretprobe_lock, flags);
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head = kretprobe_inst_table_head(current);
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/*
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* It is possible to have multiple instances associated with a given
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* task either because an multiple functions in the call path
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* have a return probe installed on them, and/or more then one return
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* return probe was registered for a target function.
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*
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* We can handle this because:
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* - instances are always inserted at the head of the list
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* - when multiple return probes are registered for the same
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* function, the first instance's ret_addr will point to the
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* real return address, and all the rest will point to
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* kretprobe_trampoline
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*/
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hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
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if (ri->task != current)
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/* another task is sharing our hash bucket */
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continue;
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if (ri->rp && ri->rp->handler)
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ri->rp->handler(ri, regs);
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orig_ret_address = (unsigned long)ri->ret_addr;
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recycle_rp_inst(ri);
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if (orig_ret_address != trampoline_address)
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/*
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* This is the real return address. Any other
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* instances associated with this task are for
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* other calls deeper on the call stack
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*/
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break;
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}
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BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
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regs->nip = orig_ret_address;
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reset_current_kprobe();
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spin_unlock_irqrestore(&kretprobe_lock, flags);
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preempt_enable_no_resched();
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/*
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* By returning a non-zero value, we are telling
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* kprobe_handler() that we don't want the post_handler
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* to run (and have re-enabled preemption)
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*/
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return 1;
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}
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/*
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* Called after single-stepping. p->addr is the address of the
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* instruction whose first byte has been replaced by the "breakpoint"
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* instruction. To avoid the SMP problems that can occur when we
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* temporarily put back the original opcode to single-step, we
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* single-stepped a copy of the instruction. The address of this
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* copy is p->ainsn.insn.
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*/
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static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
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{
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int ret;
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unsigned int insn = *p->ainsn.insn;
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regs->nip = (unsigned long)p->addr;
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ret = emulate_step(regs, insn);
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if (ret == 0)
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regs->nip = (unsigned long)p->addr + 4;
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}
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static inline int post_kprobe_handler(struct pt_regs *regs)
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{
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struct kprobe *cur = kprobe_running();
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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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if (!cur)
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return 0;
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if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
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kcb->kprobe_status = KPROBE_HIT_SSDONE;
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cur->post_handler(cur, regs, 0);
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}
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resume_execution(cur, regs);
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regs->msr |= kcb->kprobe_saved_msr;
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/*Restore back the original saved kprobes variables and continue. */
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if (kcb->kprobe_status == KPROBE_REENTER) {
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restore_previous_kprobe(kcb);
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goto out;
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}
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reset_current_kprobe();
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out:
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preempt_enable_no_resched();
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/*
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* if somebody else is singlestepping across a probe point, msr
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* will have SE set, in which case, continue the remaining processing
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* of do_debug, as if this is not a probe hit.
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*/
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if (regs->msr & MSR_SE)
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return 0;
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return 1;
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}
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static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
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{
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struct kprobe *cur = kprobe_running();
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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
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return 1;
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if (kcb->kprobe_status & KPROBE_HIT_SS) {
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resume_execution(cur, regs);
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regs->msr &= ~MSR_SE;
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regs->msr |= kcb->kprobe_saved_msr;
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reset_current_kprobe();
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preempt_enable_no_resched();
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}
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return 0;
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}
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/*
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* Wrapper routine to for handling exceptions.
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*/
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int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
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unsigned long val, void *data)
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{
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struct die_args *args = (struct die_args *)data;
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int ret = NOTIFY_DONE;
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switch (val) {
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case DIE_BPT:
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if (kprobe_handler(args->regs))
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ret = NOTIFY_STOP;
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break;
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case DIE_SSTEP:
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if (post_kprobe_handler(args->regs))
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ret = NOTIFY_STOP;
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break;
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case DIE_PAGE_FAULT:
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/* kprobe_running() needs smp_processor_id() */
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preempt_disable();
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if (kprobe_running() &&
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kprobe_fault_handler(args->regs, args->trapnr))
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ret = NOTIFY_STOP;
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preempt_enable();
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break;
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default:
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break;
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}
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return ret;
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}
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int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
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{
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struct jprobe *jp = container_of(p, struct jprobe, kp);
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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
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/* setup return addr to the jprobe handler routine */
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regs->nip = (unsigned long)(((func_descr_t *)jp->entry)->entry);
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regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
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return 1;
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}
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void __kprobes jprobe_return(void)
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{
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asm volatile("trap" ::: "memory");
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}
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void __kprobes jprobe_return_end(void)
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{
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};
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int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
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{
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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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/*
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* FIXME - we should ideally be validating that we got here 'cos
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* of the "trap" in jprobe_return() above, before restoring the
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* saved regs...
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*/
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memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
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preempt_enable_no_resched();
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return 1;
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}
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static struct kprobe trampoline_p = {
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.addr = (kprobe_opcode_t *) &kretprobe_trampoline,
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.pre_handler = trampoline_probe_handler
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};
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int __init arch_init_kprobes(void)
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{
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return register_kprobe(&trampoline_p);
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}
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