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572 lines
15 KiB
572 lines
15 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* Kernel Probes (KProbes) |
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* |
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* Copyright (C) IBM Corporation, 2002, 2004 |
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* |
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* 2002-Oct Created by Vamsi Krishna S <[email protected]> Kernel |
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* Probes initial implementation ( includes contributions from |
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* Rusty Russell). |
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* 2004-July Suparna Bhattacharya <[email protected]> added jumper probes |
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* interface to access function arguments. |
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* 2004-Nov Ananth N Mavinakayanahalli <[email protected]> kprobes port |
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* for PPC64 |
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*/ |
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|
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#include <linux/kprobes.h> |
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#include <linux/ptrace.h> |
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#include <linux/preempt.h> |
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#include <linux/extable.h> |
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#include <linux/kdebug.h> |
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#include <linux/slab.h> |
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#include <linux/moduleloader.h> |
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#include <asm/code-patching.h> |
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#include <asm/cacheflush.h> |
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#include <asm/sstep.h> |
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#include <asm/sections.h> |
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#include <asm/inst.h> |
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#include <asm/set_memory.h> |
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#include <linux/uaccess.h> |
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|
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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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|
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struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}}; |
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|
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bool arch_within_kprobe_blacklist(unsigned long addr) |
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{ |
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return (addr >= (unsigned long)__kprobes_text_start && |
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addr < (unsigned long)__kprobes_text_end) || |
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(addr >= (unsigned long)_stext && |
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addr < (unsigned long)__head_end); |
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} |
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kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset) |
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{ |
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kprobe_opcode_t *addr = NULL; |
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|
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#ifdef PPC64_ELF_ABI_v2 |
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/* PPC64 ABIv2 needs local entry point */ |
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addr = (kprobe_opcode_t *)kallsyms_lookup_name(name); |
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if (addr && !offset) { |
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#ifdef CONFIG_KPROBES_ON_FTRACE |
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unsigned long faddr; |
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/* |
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* Per livepatch.h, ftrace location is always within the first |
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* 16 bytes of a function on powerpc with -mprofile-kernel. |
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*/ |
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faddr = ftrace_location_range((unsigned long)addr, |
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(unsigned long)addr + 16); |
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if (faddr) |
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addr = (kprobe_opcode_t *)faddr; |
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else |
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#endif |
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addr = (kprobe_opcode_t *)ppc_function_entry(addr); |
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} |
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#elif defined(PPC64_ELF_ABI_v1) |
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/* |
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* 64bit powerpc ABIv1 uses function descriptors: |
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* - Check for the dot variant of the symbol first. |
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* - If that fails, try looking up the symbol provided. |
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* |
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* This ensures we always get to the actual symbol and not |
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* the descriptor. |
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* |
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* Also handle <module:symbol> format. |
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*/ |
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char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN]; |
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bool dot_appended = false; |
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const char *c; |
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ssize_t ret = 0; |
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int len = 0; |
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if ((c = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) { |
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c++; |
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len = c - name; |
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memcpy(dot_name, name, len); |
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} else |
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c = name; |
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if (*c != '\0' && *c != '.') { |
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dot_name[len++] = '.'; |
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dot_appended = true; |
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} |
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ret = strscpy(dot_name + len, c, KSYM_NAME_LEN); |
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if (ret > 0) |
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addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name); |
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/* Fallback to the original non-dot symbol lookup */ |
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if (!addr && dot_appended) |
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addr = (kprobe_opcode_t *)kallsyms_lookup_name(name); |
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#else |
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addr = (kprobe_opcode_t *)kallsyms_lookup_name(name); |
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#endif |
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return addr; |
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} |
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void *alloc_insn_page(void) |
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{ |
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void *page; |
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page = module_alloc(PAGE_SIZE); |
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if (!page) |
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return NULL; |
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if (strict_module_rwx_enabled()) { |
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set_memory_ro((unsigned long)page, 1); |
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set_memory_x((unsigned long)page, 1); |
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} |
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return page; |
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} |
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int arch_prepare_kprobe(struct kprobe *p) |
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{ |
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int ret = 0; |
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struct kprobe *prev; |
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struct ppc_inst insn = ppc_inst_read(p->addr); |
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if ((unsigned long)p->addr & 0x03) { |
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printk("Attempt to register kprobe at an unaligned address\n"); |
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ret = -EINVAL; |
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} else if (IS_MTMSRD(insn) || IS_RFID(insn)) { |
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printk("Cannot register a kprobe on mtmsr[d]/rfi[d]\n"); |
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ret = -EINVAL; |
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} else if ((unsigned long)p->addr & ~PAGE_MASK && |
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ppc_inst_prefixed(ppc_inst_read(p->addr - 1))) { |
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printk("Cannot register a kprobe on the second word of prefixed instruction\n"); |
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ret = -EINVAL; |
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} |
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preempt_disable(); |
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prev = get_kprobe(p->addr - 1); |
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preempt_enable_no_resched(); |
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if (prev && ppc_inst_prefixed(ppc_inst_read(prev->ainsn.insn))) { |
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printk("Cannot register a kprobe on the second word of prefixed instruction\n"); |
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ret = -EINVAL; |
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} |
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/* insn must be on a special executable page on ppc64. This is |
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* not explicitly required on ppc32 (right now), but it doesn't hurt */ |
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if (!ret) { |
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p->ainsn.insn = get_insn_slot(); |
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if (!p->ainsn.insn) |
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ret = -ENOMEM; |
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} |
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if (!ret) { |
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patch_instruction(p->ainsn.insn, insn); |
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p->opcode = ppc_inst_val(insn); |
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} |
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p->ainsn.boostable = 0; |
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return ret; |
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} |
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NOKPROBE_SYMBOL(arch_prepare_kprobe); |
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void arch_arm_kprobe(struct kprobe *p) |
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{ |
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WARN_ON_ONCE(patch_instruction(p->addr, ppc_inst(BREAKPOINT_INSTRUCTION))); |
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} |
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NOKPROBE_SYMBOL(arch_arm_kprobe); |
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void arch_disarm_kprobe(struct kprobe *p) |
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{ |
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WARN_ON_ONCE(patch_instruction(p->addr, ppc_inst(p->opcode))); |
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} |
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NOKPROBE_SYMBOL(arch_disarm_kprobe); |
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void 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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NOKPROBE_SYMBOL(arch_remove_kprobe); |
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static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs) |
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{ |
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enable_single_step(regs); |
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/* |
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* On powerpc we should single step on the original |
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* instruction even if the probed insn is a trap |
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* variant as values in regs could play a part in |
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* if the trap is taken or not |
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*/ |
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regs_set_return_ip(regs, (unsigned long)p->ainsn.insn); |
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} |
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static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb) |
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{ |
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kcb->prev_kprobe.kp = kprobe_running(); |
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kcb->prev_kprobe.status = kcb->kprobe_status; |
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kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr; |
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} |
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static nokprobe_inline 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_saved_msr = kcb->prev_kprobe.saved_msr; |
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} |
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static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs, |
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struct kprobe_ctlblk *kcb) |
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{ |
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__this_cpu_write(current_kprobe, p); |
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kcb->kprobe_saved_msr = regs->msr; |
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} |
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bool arch_kprobe_on_func_entry(unsigned long offset) |
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{ |
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#ifdef PPC64_ELF_ABI_v2 |
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#ifdef CONFIG_KPROBES_ON_FTRACE |
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return offset <= 16; |
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#else |
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return offset <= 8; |
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#endif |
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#else |
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return !offset; |
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#endif |
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} |
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void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs) |
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{ |
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ri->ret_addr = (kprobe_opcode_t *)regs->link; |
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ri->fp = NULL; |
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/* Replace the return addr with trampoline addr */ |
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regs->link = (unsigned long)kretprobe_trampoline; |
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} |
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NOKPROBE_SYMBOL(arch_prepare_kretprobe); |
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static int try_to_emulate(struct kprobe *p, struct pt_regs *regs) |
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{ |
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int ret; |
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struct ppc_inst insn = ppc_inst_read(p->ainsn.insn); |
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/* regs->nip is also adjusted if emulate_step returns 1 */ |
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ret = emulate_step(regs, insn); |
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if (ret > 0) { |
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/* |
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* Once this instruction has been boosted |
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* successfully, set the boostable flag |
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*/ |
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if (unlikely(p->ainsn.boostable == 0)) |
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p->ainsn.boostable = 1; |
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} else if (ret < 0) { |
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/* |
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* We don't allow kprobes on mtmsr(d)/rfi(d), etc. |
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* So, we should never get here... but, its still |
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* good to catch them, just in case... |
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*/ |
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printk("Can't step on instruction %s\n", ppc_inst_as_str(insn)); |
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BUG(); |
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} else { |
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/* |
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* If we haven't previously emulated this instruction, then it |
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* can't be boosted. Note it down so we don't try to do so again. |
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* |
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* If, however, we had emulated this instruction in the past, |
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* then this is just an error with the current run (for |
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* instance, exceptions due to a load/store). We return 0 so |
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* that this is now single-stepped, but continue to try |
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* emulating it in subsequent probe hits. |
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*/ |
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if (unlikely(p->ainsn.boostable != 1)) |
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p->ainsn.boostable = -1; |
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} |
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return ret; |
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} |
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NOKPROBE_SYMBOL(try_to_emulate); |
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int kprobe_handler(struct pt_regs *regs) |
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{ |
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struct kprobe *p; |
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int ret = 0; |
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unsigned int *addr = (unsigned int *)regs->nip; |
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struct kprobe_ctlblk *kcb; |
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if (user_mode(regs)) |
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return 0; |
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if (!(regs->msr & MSR_IR) || !(regs->msr & MSR_DR)) |
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return 0; |
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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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p = get_kprobe(addr); |
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if (!p) { |
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unsigned int instr; |
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if (get_kernel_nofault(instr, addr)) |
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goto no_kprobe; |
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if (instr != BREAKPOINT_INSTRUCTION) { |
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/* |
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* PowerPC has multiple variants of the "trap" |
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* instruction. If the current instruction is a |
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* trap variant, it could belong to someone else |
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*/ |
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if (is_trap(instr)) |
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goto no_kprobe; |
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/* |
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* The breakpoint instruction was removed right |
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* after we hit it. Another cpu has removed |
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* either a probepoint or a debugger breakpoint |
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* at this address. In either case, no further |
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* handling of this interrupt is appropriate. |
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*/ |
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ret = 1; |
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} |
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/* Not one of ours: let kernel handle it */ |
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goto no_kprobe; |
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} |
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/* Check we're not actually recursing */ |
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if (kprobe_running()) { |
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kprobe_opcode_t insn = *p->ainsn.insn; |
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if (kcb->kprobe_status == KPROBE_HIT_SS && is_trap(insn)) { |
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/* Turn off 'trace' bits */ |
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regs_set_return_msr(regs, |
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(regs->msr & ~MSR_SINGLESTEP) | |
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kcb->kprobe_saved_msr); |
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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 another probe |
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* was hit while within the handler. We here save the original |
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* kprobes variables and just single step on the instruction of |
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* the new probe 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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kcb->kprobe_status = KPROBE_REENTER; |
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if (p->ainsn.boostable >= 0) { |
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ret = try_to_emulate(p, regs); |
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if (ret > 0) { |
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restore_previous_kprobe(kcb); |
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preempt_enable_no_resched(); |
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return 1; |
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} |
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} |
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prepare_singlestep(p, regs); |
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return 1; |
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} |
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kcb->kprobe_status = KPROBE_HIT_ACTIVE; |
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set_current_kprobe(p, regs, kcb); |
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if (p->pre_handler && p->pre_handler(p, regs)) { |
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/* handler changed execution path, 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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if (p->ainsn.boostable >= 0) { |
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ret = try_to_emulate(p, regs); |
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if (ret > 0) { |
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if (p->post_handler) |
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p->post_handler(p, regs, 0); |
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kcb->kprobe_status = KPROBE_HIT_SSDONE; |
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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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} |
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prepare_singlestep(p, regs); |
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kcb->kprobe_status = KPROBE_HIT_SS; |
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return 1; |
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no_kprobe: |
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preempt_enable_no_resched(); |
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return ret; |
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} |
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NOKPROBE_SYMBOL(kprobe_handler); |
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/* |
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* Function return probe trampoline: |
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* - init_kprobes() establishes a probepoint here |
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* - When the probed function returns, this probe |
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* causes the handlers to fire |
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*/ |
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asm(".global kretprobe_trampoline\n" |
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".type kretprobe_trampoline, @function\n" |
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"kretprobe_trampoline:\n" |
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"nop\n" |
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"blr\n" |
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".size kretprobe_trampoline, .-kretprobe_trampoline\n"); |
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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 trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) |
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{ |
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unsigned long orig_ret_address; |
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orig_ret_address = __kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL); |
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/* |
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* We get here through one of two paths: |
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* 1. by taking a trap -> kprobe_handler() -> here |
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* 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here |
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* |
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* When going back through (1), we need regs->nip to be setup properly |
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* as it is used to determine the return address from the trap. |
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* For (2), since nip is not honoured with optprobes, we instead setup |
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* the link register properly so that the subsequent 'blr' in |
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* kretprobe_trampoline jumps back to the right instruction. |
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* |
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* For nip, we should set the address to the previous instruction since |
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* we end up emulating it in kprobe_handler(), which increments the nip |
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* again. |
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*/ |
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regs_set_return_ip(regs, orig_ret_address - 4); |
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regs->link = orig_ret_address; |
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return 0; |
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} |
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NOKPROBE_SYMBOL(trampoline_probe_handler); |
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/* |
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* Called after single-stepping. p->addr is the address of the |
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* instruction whose first byte has been replaced by the "breakpoint" |
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* instruction. To avoid the SMP problems that can occur when we |
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* temporarily put back the original opcode to single-step, we |
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* single-stepped a copy of the instruction. The address of this |
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* copy is p->ainsn.insn. |
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*/ |
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int kprobe_post_handler(struct pt_regs *regs) |
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{ |
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int len; |
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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 || user_mode(regs)) |
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return 0; |
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len = ppc_inst_len(ppc_inst_read(cur->ainsn.insn)); |
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/* make sure we got here for instruction we have a kprobe on */ |
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if (((unsigned long)cur->ainsn.insn + len) != regs->nip) |
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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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/* Adjust nip to after the single-stepped instruction */ |
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regs_set_return_ip(regs, (unsigned long)cur->addr + len); |
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regs_set_return_msr(regs, regs->msr | kcb->kprobe_saved_msr); |
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/*Restore back the original saved kprobes variables and continue. */ |
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if (kcb->kprobe_status == KPROBE_REENTER) { |
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restore_previous_kprobe(kcb); |
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goto out; |
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} |
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reset_current_kprobe(); |
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out: |
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preempt_enable_no_resched(); |
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/* |
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* if somebody else is singlestepping across a probe point, msr |
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* will have DE/SE set, in which case, continue the remaining processing |
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* of do_debug, as if this is not a probe hit. |
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*/ |
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if (regs->msr & MSR_SINGLESTEP) |
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return 0; |
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return 1; |
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} |
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NOKPROBE_SYMBOL(kprobe_post_handler); |
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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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const struct exception_table_entry *entry; |
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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 nip 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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regs_set_return_ip(regs, (unsigned long)cur->addr); |
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/* Turn off 'trace' bits */ |
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regs_set_return_msr(regs, |
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(regs->msr & ~MSR_SINGLESTEP) | |
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kcb->kprobe_saved_msr); |
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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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preempt_enable_no_resched(); |
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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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* 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 ((entry = search_exception_tables(regs->nip)) != NULL) { |
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regs_set_return_ip(regs, extable_fixup(entry)); |
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return 1; |
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} |
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/* |
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* fixup_exception() could not handle it, |
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* Let do_page_fault() fix it. |
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*/ |
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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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NOKPROBE_SYMBOL(kprobe_fault_handler); |
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|
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unsigned long arch_deref_entry_point(void *entry) |
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{ |
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#ifdef PPC64_ELF_ABI_v1 |
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if (!kernel_text_address((unsigned long)entry)) |
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return ppc_global_function_entry(entry); |
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else |
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#endif |
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return (unsigned long)entry; |
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} |
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NOKPROBE_SYMBOL(arch_deref_entry_point); |
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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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|
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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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|
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int 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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|
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return 0; |
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} |
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NOKPROBE_SYMBOL(arch_trampoline_kprobe);
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|