arch/arm/probes/kprobes/checkers-thumb.c

   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 };