2 * arch/arm64/kernel/probes/decode-insn.c
4 * Copyright (C) 2013 Linaro Limited.
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
16 #include <linux/kernel.h>
17 #include <linux/kprobes.h>
18 #include <linux/module.h>
19 #include <asm/kprobes.h>
21 #include <asm/sections.h>
23 #include "decode-insn.h"
24 #include "simulate-insn.h"
26 static bool __kprobes aarch64_insn_is_steppable(u32 insn)
29 * Branch instructions will write a new value into the PC which is
30 * likely to be relative to the XOL address and therefore invalid.
31 * Deliberate generation of an exception during stepping is also not
32 * currently safe. Lastly, MSR instructions can do any number of nasty
33 * things we can't handle during single-stepping.
35 if (aarch64_get_insn_class(insn) == AARCH64_INSN_CLS_BR_SYS) {
36 if (aarch64_insn_is_branch(insn) ||
37 aarch64_insn_is_msr_imm(insn) ||
38 aarch64_insn_is_msr_reg(insn) ||
39 aarch64_insn_is_exception(insn) ||
40 aarch64_insn_is_eret(insn))
44 * The MRS instruction may not return a correct value when
45 * executing in the single-stepping environment. We do make one
46 * exception, for reading the DAIF bits.
48 if (aarch64_insn_is_mrs(insn))
49 return aarch64_insn_extract_system_reg(insn)
50 != AARCH64_INSN_SPCLREG_DAIF;
53 * The HINT instruction is is problematic when single-stepping,
54 * except for the NOP case.
56 if (aarch64_insn_is_hint(insn))
57 return aarch64_insn_is_nop(insn);
63 * Instructions which load PC relative literals are not going to work
64 * when executed from an XOL slot. Instructions doing an exclusive
65 * load/store are not going to complete successfully when single-step
66 * exception handling happens in the middle of the sequence.
68 if (aarch64_insn_uses_literal(insn) ||
69 aarch64_insn_is_exclusive(insn))
76 * INSN_REJECTED If instruction is one not allowed to kprobe,
77 * INSN_GOOD If instruction is supported and uses instruction slot,
78 * INSN_GOOD_NO_SLOT If instruction is supported but doesn't use its slot.
80 static enum kprobe_insn __kprobes
81 arm_probe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
84 * Instructions reading or modifying the PC won't work from the XOL
87 if (aarch64_insn_is_steppable(insn))
90 if (aarch64_insn_is_bcond(insn)) {
91 asi->handler = simulate_b_cond;
92 } else if (aarch64_insn_is_cbz(insn) ||
93 aarch64_insn_is_cbnz(insn)) {
94 asi->handler = simulate_cbz_cbnz;
95 } else if (aarch64_insn_is_tbz(insn) ||
96 aarch64_insn_is_tbnz(insn)) {
97 asi->handler = simulate_tbz_tbnz;
98 } else if (aarch64_insn_is_adr_adrp(insn)) {
99 asi->handler = simulate_adr_adrp;
100 } else if (aarch64_insn_is_b(insn) ||
101 aarch64_insn_is_bl(insn)) {
102 asi->handler = simulate_b_bl;
103 } else if (aarch64_insn_is_br(insn) ||
104 aarch64_insn_is_blr(insn) ||
105 aarch64_insn_is_ret(insn)) {
106 asi->handler = simulate_br_blr_ret;
107 } else if (aarch64_insn_is_ldr_lit(insn)) {
108 asi->handler = simulate_ldr_literal;
109 } else if (aarch64_insn_is_ldrsw_lit(insn)) {
110 asi->handler = simulate_ldrsw_literal;
113 * Instruction cannot be stepped out-of-line and we don't
116 return INSN_REJECTED;
119 return INSN_GOOD_NO_SLOT;
122 static bool __kprobes
123 is_probed_address_atomic(kprobe_opcode_t *scan_start, kprobe_opcode_t *scan_end)
125 while (scan_start > scan_end) {
127 * atomic region starts from exclusive load and ends with
130 if (aarch64_insn_is_store_ex(le32_to_cpu(*scan_start)))
132 else if (aarch64_insn_is_load_ex(le32_to_cpu(*scan_start)))
140 enum kprobe_insn __kprobes
141 arm_kprobe_decode_insn(kprobe_opcode_t *addr, struct arch_specific_insn *asi)
143 enum kprobe_insn decoded;
144 kprobe_opcode_t insn = le32_to_cpu(*addr);
145 kprobe_opcode_t *scan_start = addr - 1;
146 kprobe_opcode_t *scan_end = addr - MAX_ATOMIC_CONTEXT_SIZE;
147 #if defined(CONFIG_MODULES) && defined(MODULES_VADDR)
151 if (addr >= (kprobe_opcode_t *)_text &&
152 scan_end < (kprobe_opcode_t *)_text)
153 scan_end = (kprobe_opcode_t *)_text;
154 #if defined(CONFIG_MODULES) && defined(MODULES_VADDR)
157 mod = __module_address((unsigned long)addr);
158 if (mod && within_module_init((unsigned long)addr, mod) &&
159 !within_module_init((unsigned long)scan_end, mod))
160 scan_end = (kprobe_opcode_t *)mod->init_layout.base;
161 else if (mod && within_module_core((unsigned long)addr, mod) &&
162 !within_module_core((unsigned long)scan_end, mod))
163 scan_end = (kprobe_opcode_t *)mod->core_layout.base;
167 decoded = arm_probe_decode_insn(insn, asi);
169 if (decoded == INSN_REJECTED ||
170 is_probed_address_atomic(scan_start, scan_end))
171 return INSN_REJECTED;