ARM kprobes: core code
This is a full implementation of Kprobes including Jprobes and Kretprobes support. This ARM implementation does not follow the usual kprobes double- exception model. The traditional model is where the initial kprobes breakpoint calls kprobe_handler(), which returns from exception to execute the instruction in its original context, then immediately re-enters after a second breakpoint (or single-stepping exception) into post_kprobe_handler(), each time the probe is hit.. The ARM implementation only executes one kprobes exception per hit, so no post_kprobe_handler() phase. All side-effects from the kprobe'd instruction are resolved before returning from the initial exception. As a result, all instructions are _always_ effectively boosted regardless of the type of instruction, and even regardless of whether or not there is a post-handler for the probe. Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com> Signed-off-by: Quentin Barnes <qbarnes@gmail.com> Signed-off-by: Nicolas Pitre <nico@marvell.com>
This commit is contained in:
Abhishek Sagar
Russell King
parent
35aa1df432
commit
24ba613c9d
@ -19,7 +19,7 @@ obj-$(CONFIG_ISA_DMA) += dma-isa.o
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obj-$(CONFIG_PCI) += bios32.o isa.o
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obj-$(CONFIG_SMP) += smp.o
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obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o
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obj-$(CONFIG_KPROBES) += kprobes-decode.o
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obj-$(CONFIG_KPROBES) += kprobes.o kprobes-decode.o
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obj-$(CONFIG_OABI_COMPAT) += sys_oabi-compat.o
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obj-$(CONFIG_CRUNCH) += crunch.o crunch-bits.o
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453
arch/arm/kernel/kprobes.c
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453
arch/arm/kernel/kprobes.c
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@ -0,0 +1,453 @@
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/*
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* arch/arm/kernel/kprobes.c
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*
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* Kprobes on ARM
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*
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* Abhishek Sagar <sagar.abhishek@gmail.com>
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* Copyright (C) 2006, 2007 Motorola Inc.
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*
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* Nicolas Pitre <nico@marvell.com>
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* Copyright (C) 2007 Marvell Ltd.
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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 version 2 as
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* published by the Free Software Foundation.
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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 GNU
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* General Public License for more details.
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*/
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#include <linux/kernel.h>
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#include <linux/kprobes.h>
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#include <linux/module.h>
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#include <linux/stringify.h>
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#include <asm/traps.h>
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#include <asm/cacheflush.h>
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/*
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* This undefined instruction must be unique and
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* reserved solely for kprobes' use.
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*/
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#define KPROBE_BREAKPOINT_INSTRUCTION 0xe7f001f8
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#define MIN_STACK_SIZE(addr) \
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min((unsigned long)MAX_STACK_SIZE, \
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(unsigned long)current_thread_info() + THREAD_START_SP - (addr))
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#define flush_insns(addr, cnt) \
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flush_icache_range((unsigned long)(addr), \
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(unsigned long)(addr) + \
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sizeof(kprobe_opcode_t) * (cnt))
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/* Used as a marker in ARM_pc to note when we're in a jprobe. */
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#define JPROBE_MAGIC_ADDR 0xffffffff
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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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kprobe_opcode_t insn;
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kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
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unsigned long addr = (unsigned long)p->addr;
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int is;
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if (addr & 0x3)
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return -EINVAL;
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insn = *p->addr;
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p->opcode = insn;
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p->ainsn.insn = tmp_insn;
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switch (arm_kprobe_decode_insn(insn, &p->ainsn)) {
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case INSN_REJECTED: /* not supported */
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return -EINVAL;
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case INSN_GOOD: /* instruction uses slot */
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p->ainsn.insn = get_insn_slot();
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if (!p->ainsn.insn)
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return -ENOMEM;
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for (is = 0; is < MAX_INSN_SIZE; ++is)
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p->ainsn.insn[is] = tmp_insn[is];
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flush_insns(&p->ainsn.insn, MAX_INSN_SIZE);
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break;
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case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */
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p->ainsn.insn = NULL;
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break;
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}
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return 0;
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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 = KPROBE_BREAKPOINT_INSTRUCTION;
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flush_insns(p->addr, 1);
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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_insns(p->addr, 1);
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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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mutex_lock(&kprobe_mutex);
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free_insn_slot(p->ainsn.insn, 0);
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mutex_unlock(&kprobe_mutex);
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p->ainsn.insn = NULL;
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}
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}
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static void __kprobes 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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}
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static void __kprobes 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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}
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static void __kprobes set_current_kprobe(struct kprobe *p)
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{
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__get_cpu_var(current_kprobe) = p;
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}
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static void __kprobes singlestep(struct kprobe *p, struct pt_regs *regs,
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struct kprobe_ctlblk *kcb)
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{
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regs->ARM_pc += 4;
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p->ainsn.insn_handler(p, regs);
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}
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/*
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* Called with IRQs disabled. IRQs must remain disabled from that point
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* all the way until processing this kprobe is complete. The current
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* kprobes implementation cannot process more than one nested level of
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* kprobe, and that level is reserved for user kprobe handlers, so we can't
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* risk encountering a new kprobe in an interrupt handler.
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*/
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void __kprobes kprobe_handler(struct pt_regs *regs)
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{
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struct kprobe *p, *cur;
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struct kprobe_ctlblk *kcb;
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kprobe_opcode_t *addr = (kprobe_opcode_t *)regs->ARM_pc;
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kcb = get_kprobe_ctlblk();
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cur = kprobe_running();
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p = get_kprobe(addr);
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if (p) {
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if (cur) {
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/* Kprobe is pending, so we're recursing. */
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switch (kcb->kprobe_status) {
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case KPROBE_HIT_ACTIVE:
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case KPROBE_HIT_SSDONE:
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/* A pre- or post-handler probe got us here. */
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kprobes_inc_nmissed_count(p);
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save_previous_kprobe(kcb);
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set_current_kprobe(p);
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kcb->kprobe_status = KPROBE_REENTER;
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singlestep(p, regs, kcb);
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restore_previous_kprobe(kcb);
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break;
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default:
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/* impossible cases */
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BUG();
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}
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} else {
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set_current_kprobe(p);
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kcb->kprobe_status = KPROBE_HIT_ACTIVE;
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/*
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* If we have no pre-handler or it returned 0, we
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* continue with normal processing. If we have a
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* pre-handler and it returned non-zero, it prepped
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* for calling the break_handler below on re-entry,
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* so get out doing nothing more here.
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*/
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if (!p->pre_handler || !p->pre_handler(p, regs)) {
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kcb->kprobe_status = KPROBE_HIT_SS;
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singlestep(p, regs, kcb);
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if (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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reset_current_kprobe();
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}
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}
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} else if (cur) {
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/* We probably hit a jprobe. Call its break handler. */
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if (cur->break_handler && cur->break_handler(cur, regs)) {
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kcb->kprobe_status = KPROBE_HIT_SS;
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singlestep(cur, regs, kcb);
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if (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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}
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reset_current_kprobe();
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} else {
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/*
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* The probe was removed and a race is in progress.
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* There is nothing we can do about it. Let's restart
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* the instruction. By the time we can restart, the
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* real instruction will be there.
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*/
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}
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}
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static int kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
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{
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kprobe_handler(regs);
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return 0;
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}
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int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
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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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switch (kcb->kprobe_status) {
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case KPROBE_HIT_SS:
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case KPROBE_REENTER:
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/*
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* We are here because the instruction being single
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* stepped caused a page fault. We reset the current
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* kprobe and the PC to point back to the probe address
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* and allow the page fault handler to continue as a
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* normal page fault.
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*/
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regs->ARM_pc = (long)cur->addr;
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if (kcb->kprobe_status == KPROBE_REENTER) {
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restore_previous_kprobe(kcb);
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} else {
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reset_current_kprobe();
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}
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break;
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case KPROBE_HIT_ACTIVE:
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case KPROBE_HIT_SSDONE:
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/*
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* We increment the nmissed count for accounting,
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* we can also use npre/npostfault count for accounting
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* these specific fault cases.
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*/
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kprobes_inc_nmissed_count(cur);
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/*
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* We come here because instructions in the pre/post
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* handler caused the page_fault, this could happen
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* if handler tries to access user space by
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* copy_from_user(), get_user() etc. Let the
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* user-specified handler try to fix it.
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*/
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if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
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return 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 0;
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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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/*
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* notify_die() is currently never called on ARM,
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* so this callback is currently empty.
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*/
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return NOTIFY_DONE;
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}
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/*
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* When a retprobed function returns, trampoline_handler() is called,
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* calling the kretprobe's handler. We construct a struct pt_regs to
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* give a view of registers r0-r11 to the user return-handler. This is
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* not a complete pt_regs structure, but that should be plenty sufficient
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* for kretprobe handlers which should normally be interested in r0 only
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* anyway.
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*/
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static void __attribute__((naked)) __kprobes kretprobe_trampoline(void)
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{
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__asm__ __volatile__ (
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"stmdb sp!, {r0 - r11} \n\t"
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"mov r0, sp \n\t"
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"bl trampoline_handler \n\t"
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"mov lr, r0 \n\t"
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"ldmia sp!, {r0 - r11} \n\t"
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"mov pc, lr \n\t"
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: : : "memory");
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}
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/* Called from kretprobe_trampoline */
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static __used __kprobes void *trampoline_handler(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, empty_rp;
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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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INIT_HLIST_HEAD(&empty_rp);
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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 multiple functions in the call path have
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* a return probe installed on them, and/or more than one return
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* 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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__get_cpu_var(current_kprobe) = &ri->rp->kp;
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get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
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ri->rp->handler(ri, regs);
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__get_cpu_var(current_kprobe) = NULL;
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}
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orig_ret_address = (unsigned long)ri->ret_addr;
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recycle_rp_inst(ri, &empty_rp);
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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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kretprobe_assert(ri, orig_ret_address, trampoline_address);
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spin_unlock_irqrestore(&kretprobe_lock, flags);
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hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
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hlist_del(&ri->hlist);
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kfree(ri);
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}
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return (void *)orig_ret_address;
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}
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/* Called with kretprobe_lock held. */
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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->ARM_lr;
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/* Replace the return addr with trampoline addr. */
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regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
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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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long sp_addr = regs->ARM_sp;
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kcb->jprobe_saved_regs = *regs;
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memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
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regs->ARM_pc = (long)jp->entry;
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regs->ARM_cpsr |= PSR_I_BIT;
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preempt_disable();
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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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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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__asm__ __volatile__ (
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/*
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* Setup an empty pt_regs. Fill SP and PC fields as
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* they're needed by longjmp_break_handler.
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*/
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"sub sp, %0, %1 \n\t"
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"ldr r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
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"str %0, [sp, %2] \n\t"
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"str r0, [sp, %3] \n\t"
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"mov r0, sp \n\t"
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"bl kprobe_handler \n\t"
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/*
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* Return to the context saved by setjmp_pre_handler
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* and restored by longjmp_break_handler.
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*/
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"ldr r0, [sp, %4] \n\t"
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"msr cpsr_cxsf, r0 \n\t"
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"ldmia sp, {r0 - pc} \n\t"
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:
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: "r" (kcb->jprobe_saved_regs.ARM_sp),
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"I" (sizeof(struct pt_regs)),
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"J" (offsetof(struct pt_regs, ARM_sp)),
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"J" (offsetof(struct pt_regs, ARM_pc)),
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"J" (offsetof(struct pt_regs, ARM_cpsr))
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: "memory", "cc");
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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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long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
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long orig_sp = regs->ARM_sp;
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struct jprobe *jp = container_of(p, struct jprobe, kp);
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if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
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if (orig_sp != stack_addr) {
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struct pt_regs *saved_regs =
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(struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
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printk("current sp %lx does not match saved sp %lx\n",
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orig_sp, stack_addr);
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printk("Saved registers for jprobe %p\n", jp);
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show_regs(saved_regs);
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printk("Current registers\n");
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show_regs(regs);
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BUG();
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}
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*regs = kcb->jprobe_saved_regs;
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memcpy((void *)stack_addr, kcb->jprobes_stack,
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MIN_STACK_SIZE(stack_addr));
|
||||
preempt_enable_no_resched();
|
||||
return 1;
|
||||
}
|
||||
return 0;
|
||||
}
|
||||
|
||||
static struct undef_hook kprobes_break_hook = {
|
||||
.instr_mask = 0xffffffff,
|
||||
.instr_val = KPROBE_BREAKPOINT_INSTRUCTION,
|
||||
.cpsr_mask = MODE_MASK,
|
||||
.cpsr_val = SVC_MODE,
|
||||
.fn = kprobe_trap_handler,
|
||||
};
|
||||
|
||||
int __init arch_init_kprobes()
|
||||
{
|
||||
arm_kprobe_decode_init();
|
||||
register_undef_hook(&kprobes_break_hook);
|
||||
return 0;
|
||||
}
|
||||
@ -18,6 +18,16 @@
|
||||
|
||||
#include <linux/types.h>
|
||||
#include <linux/ptrace.h>
|
||||
#include <linux/percpu.h>
|
||||
|
||||
#define ARCH_SUPPORTS_KRETPROBES
|
||||
#define __ARCH_WANT_KPROBES_INSN_SLOT
|
||||
#define MAX_INSN_SIZE 2
|
||||
#define MAX_STACK_SIZE 64 /* 32 would probably be OK */
|
||||
|
||||
#define regs_return_value(regs) ((regs)->ARM_r0)
|
||||
#define flush_insn_slot(p) do { } while (0)
|
||||
#define kretprobe_blacklist_size 0
|
||||
|
||||
typedef u32 kprobe_opcode_t;
|
||||
|
||||
@ -30,6 +40,25 @@ struct arch_specific_insn {
|
||||
kprobe_insn_handler_t *insn_handler;
|
||||
};
|
||||
|
||||
struct prev_kprobe {
|
||||
struct kprobe *kp;
|
||||
unsigned int status;
|
||||
};
|
||||
|
||||
/* per-cpu kprobe control block */
|
||||
struct kprobe_ctlblk {
|
||||
unsigned int kprobe_status;
|
||||
struct prev_kprobe prev_kprobe;
|
||||
struct pt_regs jprobe_saved_regs;
|
||||
char jprobes_stack[MAX_STACK_SIZE];
|
||||
};
|
||||
|
||||
void arch_remove_kprobe(struct kprobe *);
|
||||
|
||||
int kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr);
|
||||
int kprobe_exceptions_notify(struct notifier_block *self,
|
||||
unsigned long val, void *data);
|
||||
|
||||
enum kprobe_insn {
|
||||
INSN_REJECTED,
|
||||
INSN_GOOD,
|
||||
|
||||
Loading…
Reference in New Issue
Block a user