1 /* 2 * arch/arm/probes/kprobes/checkers-thumb.c 3 * 4 * Copyright (C) 2014 Huawei Inc. 5 * 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. 9 * 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. 14 */ 15 16 #include <linux/kernel.h> 17 #include "../decode.h" 18 #include "../decode-thumb.h" 19 #include "checkers.h" 20 21 static enum probes_insn __kprobes t32_check_stack(probes_opcode_t insn, 22 struct arch_probes_insn *asi, 23 const struct decode_header *h) 24 { 25 /* 26 * PROBES_T32_LDMSTM, PROBES_T32_LDRDSTRD and PROBES_T32_LDRSTR 27 * may get here. Simply mark all normal insns as STACK_USE_NONE. 28 */ 29 static const union decode_item table[] = { 30 31 /* 32 * First, filter out all ldr insns to make our life easier. 33 * Following load insns may come here: 34 * LDM, LDRD, LDR. 35 * In T32 encoding, bit 20 is enough for distinguishing 36 * load and store. All load insns have this bit set, when 37 * all store insns have this bit clear. 38 */ 39 DECODE_CUSTOM (0x00100000, 0x00100000, STACK_USE_NONE), 40 41 /* 42 * Mark all 'STR{,B,H}, Rt, [Rn, Rm]' as STACK_USE_UNKNOWN 43 * if Rn or Rm is SP. T32 doesn't encode STRD. 44 */ 45 /* xx | Rn | Rt | | Rm |*/ 46 /* STR (register) 1111 1000 0100 xxxx xxxx 0000 00xx xxxx */ 47 /* STRB (register) 1111 1000 0000 xxxx xxxx 0000 00xx xxxx */ 48 /* STRH (register) 1111 1000 0010 xxxx xxxx 0000 00xx xxxx */ 49 /* INVALID INSN 1111 1000 0110 xxxx xxxx 0000 00xx xxxx */ 50 /* By Introducing INVALID INSN, bit 21 and 22 can be ignored. */ 51 DECODE_OR (0xff9f0fc0, 0xf80d0000), 52 DECODE_CUSTOM (0xff900fcf, 0xf800000d, STACK_USE_UNKNOWN), 53 54 55 /* xx | Rn | Rt | PUW| imm8 |*/ 56 /* STR (imm 8) 1111 1000 0100 1101 xxxx 110x xxxx xxxx */ 57 /* STRB (imm 8) 1111 1000 0000 1101 xxxx 110x xxxx xxxx */ 58 /* STRH (imm 8) 1111 1000 0010 1101 xxxx 110x xxxx xxxx */ 59 /* INVALID INSN 1111 1000 0110 1101 xxxx 110x xxxx xxxx */ 60 /* Only consider U == 0 and P == 1: strx rx, [sp, #-<imm>] */ 61 DECODE_CUSTOM (0xff9f0e00, 0xf80d0c00, STACK_USE_FIXED_0XX), 62 63 /* For STR{,B,H} (imm 12), offset is always positive, so ignore them. */ 64 65 /* P U W | Rn | Rt | Rt2| imm8 |*/ 66 /* STRD (immediate) 1110 1001 01x0 1101 xxxx xxxx xxxx xxxx */ 67 /* 68 * Only consider U == 0 and P == 1. 69 * Also note that STRD in T32 encoding is special: 70 * imm = ZeroExtend(imm8:'00', 32) 71 */ 72 DECODE_CUSTOM (0xffdf0000, 0xe94d0000, STACK_USE_T32STRD), 73 74 /* | Rn | */ 75 /* STMDB 1110 1001 00x0 1101 xxxx xxxx xxxx xxxx */ 76 DECODE_CUSTOM (0xffdf0000, 0xe90d0000, STACK_USE_STMDX), 77 78 /* fall through */ 79 DECODE_CUSTOM (0, 0, STACK_USE_NONE), 80 DECODE_END 81 }; 82 83 return probes_decode_insn(insn, asi, table, false, false, stack_check_actions, NULL); 84 } 85 86 const struct decode_checker t32_stack_checker[NUM_PROBES_T32_ACTIONS] = { 87 [PROBES_T32_LDMSTM] = {.checker = t32_check_stack}, 88 [PROBES_T32_LDRDSTRD] = {.checker = t32_check_stack}, 89 [PROBES_T32_LDRSTR] = {.checker = t32_check_stack}, 90 }; 91 92 /* 93 * See following comments. This insn must be 'push'. 94 */ 95 static enum probes_insn __kprobes t16_check_stack(probes_opcode_t insn, 96 struct arch_probes_insn *asi, 97 const struct decode_header *h) 98 { 99 unsigned int reglist = insn & 0x1ff; 100 asi->stack_space = hweight32(reglist) * 4; 101 return INSN_GOOD; 102 } 103 104 /* 105 * T16 encoding is simple: only the 'push' insn can need extra stack space. 106 * Other insns, like str, can only use r0-r7 as Rn. 107 */ 108 const struct decode_checker t16_stack_checker[NUM_PROBES_T16_ACTIONS] = { 109 [PROBES_T16_PUSH] = {.checker = t16_check_stack}, 110 }; 111