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![Masami Hiramatsu](/assets/img/avatar_default.png)
Since now there is kretprobe_trampoline_addr() for referring the address of kretprobe trampoline code, we don't need to access kretprobe_trampoline directly. Make it harder to refer by renaming it to __kretprobe_trampoline(). Link: https://lkml.kernel.org/r/163163045446.489837.14510577516938803097.stgit@devnote2 Suggested-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
562 lines
15 KiB
C
562 lines
15 KiB
C
// 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 <vamsi_krishna@in.ibm.com> Kernel
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* Probes initial implementation ( includes contributions from
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* Rusty Russell).
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* 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
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* interface to access function arguments.
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* 2004-Nov Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
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* for PPC64
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*/
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#include <linux/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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DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
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DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
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struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
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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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#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 (!IS_ENABLED(CONFIG_BOOKE) &&
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(!(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, 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.
|
|
*/
|
|
if (regs->msr & MSR_SINGLESTEP)
|
|
return 0;
|
|
|
|
return 1;
|
|
}
|
|
NOKPROBE_SYMBOL(kprobe_post_handler);
|
|
|
|
int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
|
|
{
|
|
struct kprobe *cur = kprobe_running();
|
|
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
|
|
const struct exception_table_entry *entry;
|
|
|
|
switch(kcb->kprobe_status) {
|
|
case KPROBE_HIT_SS:
|
|
case KPROBE_REENTER:
|
|
/*
|
|
* We are here because the instruction being single
|
|
* stepped caused a page fault. We reset the current
|
|
* kprobe and the nip points back to the probe address
|
|
* and allow the page fault handler to continue as a
|
|
* normal page fault.
|
|
*/
|
|
regs_set_return_ip(regs, (unsigned long)cur->addr);
|
|
/* Turn off 'trace' bits */
|
|
regs_set_return_msr(regs,
|
|
(regs->msr & ~MSR_SINGLESTEP) |
|
|
kcb->kprobe_saved_msr);
|
|
if (kcb->kprobe_status == KPROBE_REENTER)
|
|
restore_previous_kprobe(kcb);
|
|
else
|
|
reset_current_kprobe();
|
|
preempt_enable_no_resched();
|
|
break;
|
|
case KPROBE_HIT_ACTIVE:
|
|
case KPROBE_HIT_SSDONE:
|
|
/*
|
|
* In case the user-specified fault handler returned
|
|
* zero, try to fix up.
|
|
*/
|
|
if ((entry = search_exception_tables(regs->nip)) != NULL) {
|
|
regs_set_return_ip(regs, extable_fixup(entry));
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* fixup_exception() could not handle it,
|
|
* Let do_page_fault() fix it.
|
|
*/
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
return 0;
|
|
}
|
|
NOKPROBE_SYMBOL(kprobe_fault_handler);
|
|
|
|
static struct kprobe trampoline_p = {
|
|
.addr = (kprobe_opcode_t *) &__kretprobe_trampoline,
|
|
.pre_handler = trampoline_probe_handler
|
|
};
|
|
|
|
int __init arch_init_kprobes(void)
|
|
{
|
|
return register_kprobe(&trampoline_p);
|
|
}
|
|
|
|
int arch_trampoline_kprobe(struct kprobe *p)
|
|
{
|
|
if (p->addr == (kprobe_opcode_t *)&__kretprobe_trampoline)
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
NOKPROBE_SYMBOL(arch_trampoline_kprobe);
|