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518 lines
13 KiB
518 lines
13 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* Kernel Probes (KProbes) |
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* arch/mips/kernel/kprobes.c |
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* |
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* Copyright 2006 Sony Corp. |
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* Copyright 2010 Cavium Networks |
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* |
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* Some portions copied from the powerpc version. |
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* |
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* Copyright (C) IBM Corporation, 2002, 2004 |
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*/ |
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#include <linux/kprobes.h> |
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#include <linux/preempt.h> |
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#include <linux/uaccess.h> |
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#include <linux/kdebug.h> |
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#include <linux/slab.h> |
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#include <asm/ptrace.h> |
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#include <asm/branch.h> |
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#include <asm/break.h> |
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#include "probes-common.h" |
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static const union mips_instruction breakpoint_insn = { |
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.b_format = { |
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.opcode = spec_op, |
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.code = BRK_KPROBE_BP, |
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.func = break_op |
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} |
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}; |
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static const union mips_instruction breakpoint2_insn = { |
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.b_format = { |
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.opcode = spec_op, |
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.code = BRK_KPROBE_SSTEPBP, |
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.func = break_op |
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} |
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}; |
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DEFINE_PER_CPU(struct kprobe *, current_kprobe); |
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DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); |
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static int __kprobes insn_has_delayslot(union mips_instruction insn) |
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{ |
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return __insn_has_delay_slot(insn); |
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} |
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/* |
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* insn_has_ll_or_sc function checks whether instruction is ll or sc |
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* one; putting breakpoint on top of atomic ll/sc pair is bad idea; |
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* so we need to prevent it and refuse kprobes insertion for such |
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* instructions; cannot do much about breakpoint in the middle of |
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* ll/sc pair; it is upto user to avoid those places |
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*/ |
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static int __kprobes insn_has_ll_or_sc(union mips_instruction insn) |
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{ |
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int ret = 0; |
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switch (insn.i_format.opcode) { |
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case ll_op: |
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case lld_op: |
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case sc_op: |
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case scd_op: |
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ret = 1; |
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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 arch_prepare_kprobe(struct kprobe *p) |
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{ |
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union mips_instruction insn; |
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union mips_instruction prev_insn; |
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int ret = 0; |
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insn = p->addr[0]; |
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if (insn_has_ll_or_sc(insn)) { |
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pr_notice("Kprobes for ll and sc instructions are not" |
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"supported\n"); |
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ret = -EINVAL; |
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goto out; |
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} |
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if (copy_from_kernel_nofault(&prev_insn, p->addr - 1, |
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sizeof(mips_instruction)) == 0 && |
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insn_has_delayslot(prev_insn)) { |
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pr_notice("Kprobes for branch delayslot are not supported\n"); |
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ret = -EINVAL; |
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goto out; |
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} |
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if (__insn_is_compact_branch(insn)) { |
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pr_notice("Kprobes for compact branches are not supported\n"); |
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ret = -EINVAL; |
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goto out; |
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} |
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/* insn: must be on special executable page on mips. */ |
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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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goto out; |
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} |
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/* |
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* In the kprobe->ainsn.insn[] array we store the original |
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* instruction at index zero and a break trap instruction at |
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* index one. |
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* |
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* On MIPS arch if the instruction at probed address is a |
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* branch instruction, we need to execute the instruction at |
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* Branch Delayslot (BD) at the time of probe hit. As MIPS also |
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* doesn't have single stepping support, the BD instruction can |
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* not be executed in-line and it would be executed on SSOL slot |
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* using a normal breakpoint instruction in the next slot. |
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* So, read the instruction and save it for later execution. |
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*/ |
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if (insn_has_delayslot(insn)) |
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memcpy(&p->ainsn.insn[0], p->addr + 1, sizeof(kprobe_opcode_t)); |
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else |
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memcpy(&p->ainsn.insn[0], p->addr, sizeof(kprobe_opcode_t)); |
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p->ainsn.insn[1] = breakpoint2_insn; |
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p->opcode = *p->addr; |
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out: |
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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_insn; |
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flush_insn_slot(p); |
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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_insn_slot(p); |
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} |
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void __kprobes arch_remove_kprobe(struct kprobe *p) |
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{ |
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if (p->ainsn.insn) { |
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free_insn_slot(p->ainsn.insn, 0); |
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p->ainsn.insn = NULL; |
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} |
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} |
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static 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.old_SR = kcb->kprobe_old_SR; |
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kcb->prev_kprobe.saved_SR = kcb->kprobe_saved_SR; |
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kcb->prev_kprobe.saved_epc = kcb->kprobe_saved_epc; |
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} |
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static void restore_previous_kprobe(struct kprobe_ctlblk *kcb) |
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{ |
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__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); |
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kcb->kprobe_status = kcb->prev_kprobe.status; |
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kcb->kprobe_old_SR = kcb->prev_kprobe.old_SR; |
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kcb->kprobe_saved_SR = kcb->prev_kprobe.saved_SR; |
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kcb->kprobe_saved_epc = kcb->prev_kprobe.saved_epc; |
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} |
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static 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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__this_cpu_write(current_kprobe, p); |
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kcb->kprobe_saved_SR = kcb->kprobe_old_SR = (regs->cp0_status & ST0_IE); |
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kcb->kprobe_saved_epc = regs->cp0_epc; |
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} |
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/** |
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* evaluate_branch_instrucion - |
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* |
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* Evaluate the branch instruction at probed address during probe hit. The |
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* result of evaluation would be the updated epc. The insturction in delayslot |
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* would actually be single stepped using a normal breakpoint) on SSOL slot. |
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* |
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* The result is also saved in the kprobe control block for later use, |
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* in case we need to execute the delayslot instruction. The latter will be |
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* false for NOP instruction in dealyslot and the branch-likely instructions |
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* when the branch is taken. And for those cases we set a flag as |
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* SKIP_DELAYSLOT in the kprobe control block |
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*/ |
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static int evaluate_branch_instruction(struct kprobe *p, struct pt_regs *regs, |
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struct kprobe_ctlblk *kcb) |
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{ |
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union mips_instruction insn = p->opcode; |
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long epc; |
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int ret = 0; |
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epc = regs->cp0_epc; |
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if (epc & 3) |
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goto unaligned; |
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if (p->ainsn.insn->word == 0) |
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kcb->flags |= SKIP_DELAYSLOT; |
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else |
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kcb->flags &= ~SKIP_DELAYSLOT; |
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ret = __compute_return_epc_for_insn(regs, insn); |
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if (ret < 0) |
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return ret; |
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if (ret == BRANCH_LIKELY_TAKEN) |
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kcb->flags |= SKIP_DELAYSLOT; |
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kcb->target_epc = regs->cp0_epc; |
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return 0; |
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unaligned: |
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pr_notice("%s: unaligned epc - sending SIGBUS.\n", current->comm); |
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force_sig(SIGBUS); |
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return -EFAULT; |
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} |
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static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs, |
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struct kprobe_ctlblk *kcb) |
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{ |
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int ret = 0; |
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regs->cp0_status &= ~ST0_IE; |
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/* single step inline if the instruction is a break */ |
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if (p->opcode.word == breakpoint_insn.word || |
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p->opcode.word == breakpoint2_insn.word) |
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regs->cp0_epc = (unsigned long)p->addr; |
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else if (insn_has_delayslot(p->opcode)) { |
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ret = evaluate_branch_instruction(p, regs, kcb); |
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if (ret < 0) { |
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pr_notice("Kprobes: Error in evaluating branch\n"); |
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return; |
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} |
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} |
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regs->cp0_epc = (unsigned long)&p->ainsn.insn[0]; |
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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 "break 0" |
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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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* This function prepares to return from the post-single-step |
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* breakpoint trap. In case of branch instructions, the target |
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* epc to be restored. |
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*/ |
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static void __kprobes resume_execution(struct kprobe *p, |
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struct pt_regs *regs, |
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struct kprobe_ctlblk *kcb) |
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{ |
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if (insn_has_delayslot(p->opcode)) |
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regs->cp0_epc = kcb->target_epc; |
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else { |
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unsigned long orig_epc = kcb->kprobe_saved_epc; |
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regs->cp0_epc = orig_epc + 4; |
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} |
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} |
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static int __kprobes 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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kprobe_opcode_t *addr; |
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struct kprobe_ctlblk *kcb; |
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addr = (kprobe_opcode_t *) regs->cp0_epc; |
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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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if (kcb->kprobe_status == KPROBE_HIT_SS && |
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p->ainsn.insn->word == breakpoint_insn.word) { |
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regs->cp0_status &= ~ST0_IE; |
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regs->cp0_status |= kcb->kprobe_saved_SR; |
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goto no_kprobe; |
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} |
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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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kprobes_inc_nmissed_count(p); |
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prepare_singlestep(p, regs, kcb); |
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kcb->kprobe_status = KPROBE_REENTER; |
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if (kcb->flags & SKIP_DELAYSLOT) { |
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resume_execution(p, regs, kcb); |
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restore_previous_kprobe(kcb); |
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preempt_enable_no_resched(); |
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} |
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return 1; |
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} else if (addr->word != breakpoint_insn.word) { |
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/* |
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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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} |
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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->word != breakpoint_insn.word) { |
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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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set_current_kprobe(p, regs, kcb); |
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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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/* handler has already set things up, so skip ss setup */ |
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reset_current_kprobe(); |
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preempt_enable_no_resched(); |
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return 1; |
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} |
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prepare_singlestep(p, regs, kcb); |
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if (kcb->flags & SKIP_DELAYSLOT) { |
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kcb->kprobe_status = KPROBE_HIT_SSDONE; |
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if (p->post_handler) |
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p->post_handler(p, regs, 0); |
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resume_execution(p, regs, kcb); |
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preempt_enable_no_resched(); |
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} else |
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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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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, kcb); |
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regs->cp0_status |= kcb->kprobe_saved_SR; |
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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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return 1; |
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} |
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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, kcb); |
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regs->cp0_status |= kcb->kprobe_old_SR; |
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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 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_BREAK: |
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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_SSTEPBP: |
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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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/* |
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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 causes the |
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* handlers to fire |
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*/ |
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static void __used kretprobe_trampoline_holder(void) |
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{ |
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asm volatile( |
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".set push\n\t" |
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/* Keep the assembler from reordering and placing JR here. */ |
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".set noreorder\n\t" |
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"nop\n\t" |
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".global kretprobe_trampoline\n" |
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"kretprobe_trampoline:\n\t" |
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"nop\n\t" |
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".set pop" |
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: : : "memory"); |
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} |
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void kretprobe_trampoline(void); |
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void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, |
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struct pt_regs *regs) |
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{ |
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ri->ret_addr = (kprobe_opcode_t *) regs->regs[31]; |
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ri->fp = NULL; |
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/* Replace the return addr with trampoline addr */ |
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regs->regs[31] = (unsigned long)kretprobe_trampoline; |
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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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static int __kprobes trampoline_probe_handler(struct kprobe *p, |
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struct pt_regs *regs) |
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{ |
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instruction_pointer(regs) = __kretprobe_trampoline_handler(regs, |
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kretprobe_trampoline, NULL); |
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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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int __kprobes arch_trampoline_kprobe(struct kprobe *p) |
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{ |
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if (p->addr == (kprobe_opcode_t *)kretprobe_trampoline) |
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return 1; |
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return 0; |
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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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