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442 lines
11 KiB
442 lines
11 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* arch/arm64/kernel/probes/kprobes.c |
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* |
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* Kprobes support for ARM64 |
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* |
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* Copyright (C) 2013 Linaro Limited. |
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* Author: Sandeepa Prabhu <[email protected]> |
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*/ |
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#include <linux/kasan.h> |
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#include <linux/kernel.h> |
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#include <linux/kprobes.h> |
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#include <linux/extable.h> |
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#include <linux/slab.h> |
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#include <linux/stop_machine.h> |
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#include <linux/sched/debug.h> |
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#include <linux/set_memory.h> |
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#include <linux/stringify.h> |
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#include <linux/vmalloc.h> |
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#include <asm/traps.h> |
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#include <asm/ptrace.h> |
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#include <asm/cacheflush.h> |
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#include <asm/debug-monitors.h> |
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#include <asm/daifflags.h> |
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#include <asm/system_misc.h> |
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#include <asm/insn.h> |
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#include <linux/uaccess.h> |
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#include <asm/irq.h> |
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#include <asm/sections.h> |
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#include "decode-insn.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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static void __kprobes |
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post_kprobe_handler(struct kprobe *, struct kprobe_ctlblk *, struct pt_regs *); |
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static void __kprobes arch_prepare_ss_slot(struct kprobe *p) |
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{ |
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kprobe_opcode_t *addr = p->ainsn.api.insn; |
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void *addrs[] = {addr, addr + 1}; |
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u32 insns[] = {p->opcode, BRK64_OPCODE_KPROBES_SS}; |
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/* prepare insn slot */ |
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aarch64_insn_patch_text(addrs, insns, 2); |
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flush_icache_range((uintptr_t)addr, (uintptr_t)(addr + MAX_INSN_SIZE)); |
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/* |
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* Needs restoring of return address after stepping xol. |
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*/ |
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p->ainsn.api.restore = (unsigned long) p->addr + |
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sizeof(kprobe_opcode_t); |
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} |
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static void __kprobes arch_prepare_simulate(struct kprobe *p) |
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{ |
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/* This instructions is not executed xol. No need to adjust the PC */ |
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p->ainsn.api.restore = 0; |
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} |
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static void __kprobes arch_simulate_insn(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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if (p->ainsn.api.handler) |
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p->ainsn.api.handler((u32)p->opcode, (long)p->addr, regs); |
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/* single step simulated, now go for post processing */ |
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post_kprobe_handler(p, kcb, regs); |
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} |
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int __kprobes arch_prepare_kprobe(struct kprobe *p) |
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{ |
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unsigned long probe_addr = (unsigned long)p->addr; |
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if (probe_addr & 0x3) |
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return -EINVAL; |
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/* copy instruction */ |
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p->opcode = le32_to_cpu(*p->addr); |
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if (search_exception_tables(probe_addr)) |
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return -EINVAL; |
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/* decode instruction */ |
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switch (arm_kprobe_decode_insn(p->addr, &p->ainsn)) { |
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case INSN_REJECTED: /* insn not supported */ |
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return -EINVAL; |
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case INSN_GOOD_NO_SLOT: /* insn need simulation */ |
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p->ainsn.api.insn = NULL; |
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break; |
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case INSN_GOOD: /* instruction uses slot */ |
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p->ainsn.api.insn = get_insn_slot(); |
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if (!p->ainsn.api.insn) |
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return -ENOMEM; |
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break; |
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} |
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/* prepare the instruction */ |
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if (p->ainsn.api.insn) |
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arch_prepare_ss_slot(p); |
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else |
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arch_prepare_simulate(p); |
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return 0; |
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} |
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void *alloc_insn_page(void) |
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{ |
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return __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END, |
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GFP_KERNEL, PAGE_KERNEL_ROX, VM_FLUSH_RESET_PERMS, |
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NUMA_NO_NODE, __builtin_return_address(0)); |
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} |
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/* arm kprobe: install breakpoint in text */ |
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void __kprobes arch_arm_kprobe(struct kprobe *p) |
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{ |
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void *addr = p->addr; |
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u32 insn = BRK64_OPCODE_KPROBES; |
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aarch64_insn_patch_text(&addr, &insn, 1); |
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} |
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/* disarm kprobe: remove breakpoint from text */ |
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void __kprobes arch_disarm_kprobe(struct kprobe *p) |
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{ |
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void *addr = p->addr; |
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aarch64_insn_patch_text(&addr, &p->opcode, 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.api.insn) { |
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free_insn_slot(p->ainsn.api.insn, 0); |
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p->ainsn.api.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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__this_cpu_write(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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__this_cpu_write(current_kprobe, p); |
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} |
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/* |
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* Mask all of DAIF while executing the instruction out-of-line, to keep things |
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* simple and avoid nesting exceptions. Interrupts do have to be disabled since |
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* the kprobe state is per-CPU and doesn't get migrated. |
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*/ |
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static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb, |
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struct pt_regs *regs) |
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{ |
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kcb->saved_irqflag = regs->pstate & DAIF_MASK; |
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regs->pstate |= DAIF_MASK; |
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} |
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static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb, |
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struct pt_regs *regs) |
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{ |
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regs->pstate &= ~DAIF_MASK; |
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regs->pstate |= kcb->saved_irqflag; |
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} |
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static void __kprobes setup_singlestep(struct kprobe *p, |
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struct pt_regs *regs, |
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struct kprobe_ctlblk *kcb, int reenter) |
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{ |
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unsigned long slot; |
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if (reenter) { |
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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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} else { |
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kcb->kprobe_status = KPROBE_HIT_SS; |
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} |
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if (p->ainsn.api.insn) { |
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/* prepare for single stepping */ |
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slot = (unsigned long)p->ainsn.api.insn; |
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kprobes_save_local_irqflag(kcb, regs); |
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instruction_pointer_set(regs, slot); |
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} else { |
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/* insn simulation */ |
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arch_simulate_insn(p, regs); |
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} |
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} |
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static int __kprobes reenter_kprobe(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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switch (kcb->kprobe_status) { |
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case KPROBE_HIT_SSDONE: |
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case KPROBE_HIT_ACTIVE: |
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kprobes_inc_nmissed_count(p); |
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setup_singlestep(p, regs, kcb, 1); |
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break; |
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case KPROBE_HIT_SS: |
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case KPROBE_REENTER: |
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pr_warn("Unrecoverable kprobe detected.\n"); |
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dump_kprobe(p); |
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BUG(); |
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break; |
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default: |
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WARN_ON(1); |
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return 0; |
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} |
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return 1; |
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} |
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static void __kprobes |
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post_kprobe_handler(struct kprobe *cur, struct kprobe_ctlblk *kcb, struct pt_regs *regs) |
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{ |
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/* return addr restore if non-branching insn */ |
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if (cur->ainsn.api.restore != 0) |
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instruction_pointer_set(regs, cur->ainsn.api.restore); |
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/* restore back original saved kprobe 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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return; |
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} |
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/* call post handler */ |
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kcb->kprobe_status = KPROBE_HIT_SSDONE; |
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if (cur->post_handler) |
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cur->post_handler(cur, regs, 0); |
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reset_current_kprobe(); |
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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 ip points 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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instruction_pointer_set(regs, (unsigned long) cur->addr); |
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if (!instruction_pointer(regs)) |
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BUG(); |
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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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kprobes_restore_local_irqflag(kcb, regs); |
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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 first. |
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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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/* |
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* In case the user-specified fault handler returned |
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* zero, try to fix up. |
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*/ |
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if (fixup_exception(regs)) |
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return 1; |
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} |
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return 0; |
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} |
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static void __kprobes kprobe_handler(struct pt_regs *regs) |
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{ |
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struct kprobe *p, *cur_kprobe; |
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struct kprobe_ctlblk *kcb; |
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unsigned long addr = instruction_pointer(regs); |
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kcb = get_kprobe_ctlblk(); |
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cur_kprobe = kprobe_running(); |
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p = get_kprobe((kprobe_opcode_t *) addr); |
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if (p) { |
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if (cur_kprobe) { |
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if (reenter_kprobe(p, regs, kcb)) |
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return; |
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} else { |
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/* Probe hit */ |
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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 will |
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* modify the execution path and no need to single |
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* stepping. Let's just reset current kprobe and exit. |
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*/ |
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if (!p->pre_handler || !p->pre_handler(p, regs)) { |
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setup_singlestep(p, regs, kcb, 0); |
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} else |
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reset_current_kprobe(); |
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} |
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} |
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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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* Return back to original instruction, and continue. |
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*/ |
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} |
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static int __kprobes |
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kprobe_breakpoint_ss_handler(struct pt_regs *regs, unsigned int esr) |
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{ |
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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); |
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unsigned long addr = instruction_pointer(regs); |
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struct kprobe *cur = kprobe_running(); |
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if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS | KPROBE_REENTER)) && |
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((unsigned long)&cur->ainsn.api.insn[1] == addr)) { |
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kprobes_restore_local_irqflag(kcb, regs); |
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post_kprobe_handler(cur, kcb, regs); |
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return DBG_HOOK_HANDLED; |
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} |
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/* not ours, kprobes should ignore it */ |
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return DBG_HOOK_ERROR; |
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} |
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static struct break_hook kprobes_break_ss_hook = { |
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.imm = KPROBES_BRK_SS_IMM, |
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.fn = kprobe_breakpoint_ss_handler, |
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}; |
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static int __kprobes |
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kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr) |
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{ |
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kprobe_handler(regs); |
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return DBG_HOOK_HANDLED; |
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} |
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static struct break_hook kprobes_break_hook = { |
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.imm = KPROBES_BRK_IMM, |
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.fn = kprobe_breakpoint_handler, |
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}; |
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/* |
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* Provide a blacklist of symbols identifying ranges which cannot be kprobed. |
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* This blacklist is exposed to userspace via debugfs (kprobes/blacklist). |
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*/ |
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int __init arch_populate_kprobe_blacklist(void) |
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{ |
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int ret; |
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ret = kprobe_add_area_blacklist((unsigned long)__entry_text_start, |
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(unsigned long)__entry_text_end); |
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if (ret) |
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return ret; |
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ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start, |
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(unsigned long)__irqentry_text_end); |
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if (ret) |
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return ret; |
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ret = kprobe_add_area_blacklist((unsigned long)__idmap_text_start, |
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(unsigned long)__idmap_text_end); |
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if (ret) |
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return ret; |
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ret = kprobe_add_area_blacklist((unsigned long)__hyp_text_start, |
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(unsigned long)__hyp_text_end); |
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if (ret || is_kernel_in_hyp_mode()) |
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return ret; |
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ret = kprobe_add_area_blacklist((unsigned long)__hyp_idmap_text_start, |
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(unsigned long)__hyp_idmap_text_end); |
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return ret; |
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} |
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void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs) |
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{ |
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return (void *)kretprobe_trampoline_handler(regs, &kretprobe_trampoline, |
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(void *)kernel_stack_pointer(regs)); |
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} |
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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[30]; |
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ri->fp = (void *)kernel_stack_pointer(regs); |
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/* replace return addr (x30) with trampoline */ |
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regs->regs[30] = (long)&kretprobe_trampoline; |
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} |
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int __kprobes arch_trampoline_kprobe(struct kprobe *p) |
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{ |
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return 0; |
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} |
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int __init arch_init_kprobes(void) |
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{ |
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register_kernel_break_hook(&kprobes_break_hook); |
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register_kernel_break_hook(&kprobes_break_ss_hook); |
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return 0; |
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}
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