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![Masami Hiramatsu](/assets/img/avatar_default.png)
Use the generic kretprobe trampoline handler. Use regs->ARM_fp for framepointer verification. Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/159870602406.1229682.10496730247473708592.stgit@devnote2
485 lines
12 KiB
C
485 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* arch/arm/kernel/kprobes.c
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*
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* Kprobes on ARM
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*
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* Abhishek Sagar <sagar.abhishek@gmail.com>
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* Copyright (C) 2006, 2007 Motorola Inc.
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*
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* Nicolas Pitre <nico@marvell.com>
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* Copyright (C) 2007 Marvell Ltd.
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*/
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#include <linux/kernel.h>
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#include <linux/kprobes.h>
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#include <linux/module.h>
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#include <linux/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/stringify.h>
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#include <asm/traps.h>
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#include <asm/opcodes.h>
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#include <asm/cacheflush.h>
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#include <linux/percpu.h>
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#include <linux/bug.h>
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#include <asm/patch.h>
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#include <asm/sections.h>
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#include "../decode-arm.h"
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#include "../decode-thumb.h"
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#include "core.h"
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#define MIN_STACK_SIZE(addr) \
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min((unsigned long)MAX_STACK_SIZE, \
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(unsigned long)current_thread_info() + THREAD_START_SP - (addr))
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#define flush_insns(addr, size) \
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flush_icache_range((unsigned long)(addr), \
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(unsigned long)(addr) + \
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(size))
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DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
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DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
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int __kprobes arch_prepare_kprobe(struct kprobe *p)
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{
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kprobe_opcode_t insn;
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kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
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unsigned long addr = (unsigned long)p->addr;
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bool thumb;
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kprobe_decode_insn_t *decode_insn;
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const union decode_action *actions;
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int is;
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const struct decode_checker **checkers;
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#ifdef CONFIG_THUMB2_KERNEL
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thumb = true;
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addr &= ~1; /* Bit 0 would normally be set to indicate Thumb code */
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insn = __mem_to_opcode_thumb16(((u16 *)addr)[0]);
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if (is_wide_instruction(insn)) {
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u16 inst2 = __mem_to_opcode_thumb16(((u16 *)addr)[1]);
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insn = __opcode_thumb32_compose(insn, inst2);
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decode_insn = thumb32_probes_decode_insn;
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actions = kprobes_t32_actions;
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checkers = kprobes_t32_checkers;
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} else {
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decode_insn = thumb16_probes_decode_insn;
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actions = kprobes_t16_actions;
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checkers = kprobes_t16_checkers;
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}
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#else /* !CONFIG_THUMB2_KERNEL */
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thumb = false;
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if (addr & 0x3)
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return -EINVAL;
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insn = __mem_to_opcode_arm(*p->addr);
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decode_insn = arm_probes_decode_insn;
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actions = kprobes_arm_actions;
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checkers = kprobes_arm_checkers;
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#endif
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p->opcode = insn;
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p->ainsn.insn = tmp_insn;
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switch ((*decode_insn)(insn, &p->ainsn, true, actions, checkers)) {
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case INSN_REJECTED: /* not supported */
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return -EINVAL;
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case INSN_GOOD: /* instruction uses slot */
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p->ainsn.insn = get_insn_slot();
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if (!p->ainsn.insn)
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return -ENOMEM;
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for (is = 0; is < MAX_INSN_SIZE; ++is)
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p->ainsn.insn[is] = tmp_insn[is];
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flush_insns(p->ainsn.insn,
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sizeof(p->ainsn.insn[0]) * MAX_INSN_SIZE);
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p->ainsn.insn_fn = (probes_insn_fn_t *)
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((uintptr_t)p->ainsn.insn | thumb);
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break;
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case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */
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p->ainsn.insn = NULL;
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break;
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}
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/*
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* Never instrument insn like 'str r0, [sp, +/-r1]'. Also, insn likes
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* 'str r0, [sp, #-68]' should also be prohibited.
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* See __und_svc.
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*/
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if ((p->ainsn.stack_space < 0) ||
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(p->ainsn.stack_space > MAX_STACK_SIZE))
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return -EINVAL;
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return 0;
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}
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void __kprobes arch_arm_kprobe(struct kprobe *p)
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{
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unsigned int brkp;
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void *addr;
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if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
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/* Remove any Thumb flag */
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addr = (void *)((uintptr_t)p->addr & ~1);
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if (is_wide_instruction(p->opcode))
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brkp = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION;
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else
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brkp = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION;
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} else {
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kprobe_opcode_t insn = p->opcode;
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addr = p->addr;
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brkp = KPROBE_ARM_BREAKPOINT_INSTRUCTION;
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if (insn >= 0xe0000000)
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brkp |= 0xe0000000; /* Unconditional instruction */
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else
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brkp |= insn & 0xf0000000; /* Copy condition from insn */
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}
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patch_text(addr, brkp);
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}
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/*
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* The actual disarming is done here on each CPU and synchronized using
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* stop_machine. This synchronization is necessary on SMP to avoid removing
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* a probe between the moment the 'Undefined Instruction' exception is raised
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* and the moment the exception handler reads the faulting instruction from
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* memory. It is also needed to atomically set the two half-words of a 32-bit
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* Thumb breakpoint.
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*/
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struct patch {
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void *addr;
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unsigned int insn;
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};
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static int __kprobes_remove_breakpoint(void *data)
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{
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struct patch *p = data;
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__patch_text(p->addr, p->insn);
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return 0;
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}
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void __kprobes kprobes_remove_breakpoint(void *addr, unsigned int insn)
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{
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struct patch p = {
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.addr = addr,
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.insn = insn,
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};
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stop_machine_cpuslocked(__kprobes_remove_breakpoint, &p,
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cpu_online_mask);
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}
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void __kprobes arch_disarm_kprobe(struct kprobe *p)
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{
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kprobes_remove_breakpoint((void *)((uintptr_t)p->addr & ~1),
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p->opcode);
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}
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void __kprobes arch_remove_kprobe(struct kprobe *p)
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{
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if (p->ainsn.insn) {
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free_insn_slot(p->ainsn.insn, 0);
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p->ainsn.insn = NULL;
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}
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}
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static void __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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static void __kprobes
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singlestep_skip(struct kprobe *p, struct pt_regs *regs)
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{
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#ifdef CONFIG_THUMB2_KERNEL
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regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
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if (is_wide_instruction(p->opcode))
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regs->ARM_pc += 4;
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else
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regs->ARM_pc += 2;
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#else
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regs->ARM_pc += 4;
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#endif
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}
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static inline void __kprobes
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singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb)
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{
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p->ainsn.insn_singlestep(p->opcode, &p->ainsn, regs);
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}
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/*
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* Called with IRQs disabled. IRQs must remain disabled from that point
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* all the way until processing this kprobe is complete. The current
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* kprobes implementation cannot process more than one nested level of
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* kprobe, and that level is reserved for user kprobe handlers, so we can't
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* risk encountering a new kprobe in an interrupt handler.
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*/
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void __kprobes kprobe_handler(struct pt_regs *regs)
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{
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struct kprobe *p, *cur;
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struct kprobe_ctlblk *kcb;
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kcb = get_kprobe_ctlblk();
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cur = kprobe_running();
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#ifdef CONFIG_THUMB2_KERNEL
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/*
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* First look for a probe which was registered using an address with
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* bit 0 set, this is the usual situation for pointers to Thumb code.
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* If not found, fallback to looking for one with bit 0 clear.
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*/
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p = get_kprobe((kprobe_opcode_t *)(regs->ARM_pc | 1));
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if (!p)
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p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
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#else /* ! CONFIG_THUMB2_KERNEL */
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p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
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#endif
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if (p) {
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if (!p->ainsn.insn_check_cc(regs->ARM_cpsr)) {
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/*
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* Probe hit but conditional execution check failed,
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* so just skip the instruction and continue as if
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* nothing had happened.
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* In this case, we can skip recursing check too.
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*/
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singlestep_skip(p, regs);
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} else if (cur) {
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/* Kprobe is pending, so we're recursing. */
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switch (kcb->kprobe_status) {
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case KPROBE_HIT_ACTIVE:
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case KPROBE_HIT_SSDONE:
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case KPROBE_HIT_SS:
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/* A pre- or post-handler probe got us here. */
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kprobes_inc_nmissed_count(p);
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save_previous_kprobe(kcb);
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set_current_kprobe(p);
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kcb->kprobe_status = KPROBE_REENTER;
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singlestep(p, regs, kcb);
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restore_previous_kprobe(kcb);
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break;
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case KPROBE_REENTER:
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/* A nested probe was hit in FIQ, it is a BUG */
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pr_warn("Unrecoverable kprobe detected.\n");
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dump_kprobe(p);
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fallthrough;
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default:
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/* impossible cases */
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BUG();
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}
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} else {
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/* Probe hit and conditional execution check ok. */
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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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kcb->kprobe_status = KPROBE_HIT_SS;
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singlestep(p, regs, kcb);
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if (p->post_handler) {
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kcb->kprobe_status = KPROBE_HIT_SSDONE;
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p->post_handler(p, regs, 0);
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}
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}
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reset_current_kprobe();
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}
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} else {
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/*
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* The probe was removed and a race is in progress.
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* There is nothing we can do about it. Let's restart
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* the instruction. By the time we can restart, the
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* real instruction will be there.
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*/
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}
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}
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static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
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{
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unsigned long flags;
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local_irq_save(flags);
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kprobe_handler(regs);
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local_irq_restore(flags);
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return 0;
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}
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int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
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{
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struct kprobe *cur = kprobe_running();
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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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switch (kcb->kprobe_status) {
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case KPROBE_HIT_SS:
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case KPROBE_REENTER:
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/*
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* We are here because the instruction being single
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* stepped caused a page fault. We reset the current
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* kprobe and the PC to point back to the probe address
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* and allow the page fault handler to continue as a
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* normal page fault.
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*/
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regs->ARM_pc = (long)cur->addr;
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if (kcb->kprobe_status == KPROBE_REENTER) {
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restore_previous_kprobe(kcb);
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} else {
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reset_current_kprobe();
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}
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break;
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case KPROBE_HIT_ACTIVE:
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case KPROBE_HIT_SSDONE:
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/*
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* We increment the nmissed count for accounting,
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* we can also use npre/npostfault count for accounting
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* these specific fault cases.
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*/
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kprobes_inc_nmissed_count(cur);
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/*
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* We come here because instructions in the pre/post
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* handler caused the page_fault, this could happen
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* if handler tries to access user space by
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* copy_from_user(), get_user() etc. Let the
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* user-specified handler try to fix it.
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*/
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if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
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return 1;
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break;
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default:
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break;
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}
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return 0;
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}
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int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
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unsigned long val, void *data)
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{
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/*
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* notify_die() is currently never called on ARM,
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* so this callback is currently empty.
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*/
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return NOTIFY_DONE;
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}
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/*
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* When a retprobed function returns, trampoline_handler() is called,
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* calling the kretprobe's handler. We construct a struct pt_regs to
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* give a view of registers r0-r11 to the user return-handler. This is
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* not a complete pt_regs structure, but that should be plenty sufficient
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* for kretprobe handlers which should normally be interested in r0 only
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* anyway.
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*/
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void __naked __kprobes kretprobe_trampoline(void)
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{
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__asm__ __volatile__ (
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"stmdb sp!, {r0 - r11} \n\t"
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"mov r0, sp \n\t"
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"bl trampoline_handler \n\t"
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"mov lr, r0 \n\t"
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"ldmia sp!, {r0 - r11} \n\t"
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#ifdef CONFIG_THUMB2_KERNEL
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"bx lr \n\t"
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#else
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"mov pc, lr \n\t"
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#endif
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: : : "memory");
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}
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/* Called from kretprobe_trampoline */
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static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
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{
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return (void *)kretprobe_trampoline_handler(regs, &kretprobe_trampoline,
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(void *)regs->ARM_fp);
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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->ARM_lr;
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ri->fp = (void *)regs->ARM_fp;
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/* Replace the return addr with trampoline addr. */
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regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
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}
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int __kprobes arch_trampoline_kprobe(struct kprobe *p)
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{
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return 0;
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}
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#ifdef CONFIG_THUMB2_KERNEL
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static struct undef_hook kprobes_thumb16_break_hook = {
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.instr_mask = 0xffff,
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.instr_val = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION,
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.cpsr_mask = MODE_MASK,
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.cpsr_val = SVC_MODE,
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.fn = kprobe_trap_handler,
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};
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static struct undef_hook kprobes_thumb32_break_hook = {
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.instr_mask = 0xffffffff,
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.instr_val = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION,
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.cpsr_mask = MODE_MASK,
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.cpsr_val = SVC_MODE,
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.fn = kprobe_trap_handler,
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};
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#else /* !CONFIG_THUMB2_KERNEL */
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static struct undef_hook kprobes_arm_break_hook = {
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.instr_mask = 0x0fffffff,
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.instr_val = KPROBE_ARM_BREAKPOINT_INSTRUCTION,
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.cpsr_mask = MODE_MASK,
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.cpsr_val = SVC_MODE,
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.fn = kprobe_trap_handler,
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};
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#endif /* !CONFIG_THUMB2_KERNEL */
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int __init arch_init_kprobes()
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{
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arm_probes_decode_init();
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#ifdef CONFIG_THUMB2_KERNEL
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register_undef_hook(&kprobes_thumb16_break_hook);
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register_undef_hook(&kprobes_thumb32_break_hook);
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#else
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register_undef_hook(&kprobes_arm_break_hook);
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#endif
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return 0;
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}
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bool arch_within_kprobe_blacklist(unsigned long addr)
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{
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void *a = (void *)addr;
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return __in_irqentry_text(addr) ||
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in_entry_text(addr) ||
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in_idmap_text(addr) ||
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memory_contains(__kprobes_text_start, __kprobes_text_end, a, 1);
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}
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