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

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * arch/arm/probes/kprobes/checkers-thumb.c
   4  *
   5  * Copyright (C) 2014 Huawei Inc.
   6  */
   7
   8 #include <linux/kernel.h>
   9 #include "../decode.h"
  10 #include "../decode-thumb.h"
  11 #include "checkers.h"
  12
  13 static enum probes_insn __kprobes t32_check_stack(probes_opcode_t insn,
  14                 struct arch_probes_insn *asi,
  15                 const struct decode_header *h)
  16 {
  17         /*
  18          * PROBES_T32_LDMSTM, PROBES_T32_LDRDSTRD and PROBES_T32_LDRSTR
  19          * may get here. Simply mark all normal insns as STACK_USE_NONE.
  20          */
  21         static const union decode_item table[] = {
  22
  23                 /*
  24                  * First, filter out all ldr insns to make our life easier.
  25                  * Following load insns may come here:
  26                  * LDM, LDRD, LDR.
  27                  * In T32 encoding, bit 20 is enough for distinguishing
  28                  * load and store. All load insns have this bit set, when
  29                  * all store insns have this bit clear.
  30                  */
  31                 DECODE_CUSTOM   (0x00100000, 0x00100000, STACK_USE_NONE),
  32
  33                 /*
  34                  * Mark all 'STR{,B,H}, Rt, [Rn, Rm]' as STACK_USE_UNKNOWN
  35                  * if Rn or Rm is SP. T32 doesn't encode STRD.
  36                  */
  37                 /*                                 xx | Rn | Rt |         | Rm |*/
  38                 /* STR (register)       1111 1000 0100 xxxx xxxx 0000 00xx xxxx */
  39                 /* STRB (register)      1111 1000 0000 xxxx xxxx 0000 00xx xxxx */
  40                 /* STRH (register)      1111 1000 0010 xxxx xxxx 0000 00xx xxxx */
  41                 /* INVALID INSN         1111 1000 0110 xxxx xxxx 0000 00xx xxxx */
  42                 /* By Introducing INVALID INSN, bit 21 and 22 can be ignored. */
  43                 DECODE_OR       (0xff9f0fc0, 0xf80d0000),
  44                 DECODE_CUSTOM   (0xff900fcf, 0xf800000d, STACK_USE_UNKNOWN),
  45
  46
  47                 /*                                 xx | Rn | Rt | PUW|   imm8  |*/
  48                 /* STR (imm 8)          1111 1000 0100 1101 xxxx 110x xxxx xxxx */
  49                 /* STRB (imm 8)         1111 1000 0000 1101 xxxx 110x xxxx xxxx */
  50                 /* STRH (imm 8)         1111 1000 0010 1101 xxxx 110x xxxx xxxx */
  51                 /* INVALID INSN         1111 1000 0110 1101 xxxx 110x xxxx xxxx */
  52                 /* Only consider U == 0 and P == 1: strx rx, [sp, #-<imm>] */
  53                 DECODE_CUSTOM   (0xff9f0e00, 0xf80d0c00, STACK_USE_FIXED_0XX),
  54
  55                 /* For STR{,B,H} (imm 12), offset is always positive, so ignore them. */
  56
  57                 /*                              P U W | Rn | Rt | Rt2|   imm8  |*/
  58                 /* STRD (immediate)     1110 1001 01x0 1101 xxxx xxxx xxxx xxxx */
  59                 /*
  60                  * Only consider U == 0 and P == 1.
  61                  * Also note that STRD in T32 encoding is special:
  62                  * imm = ZeroExtend(imm8:'00', 32)
  63                  */
  64                 DECODE_CUSTOM   (0xffdf0000, 0xe94d0000, STACK_USE_T32STRD),
  65
  66                 /*                                    | Rn | */
  67                 /* STMDB                1110 1001 00x0 1101 xxxx xxxx xxxx xxxx */
  68                 DECODE_CUSTOM   (0xffdf0000, 0xe90d0000, STACK_USE_STMDX),
  69
  70                 /* fall through */
  71                 DECODE_CUSTOM   (0, 0, STACK_USE_NONE),
  72                 DECODE_END
  73         };
  74
  75         return probes_decode_insn(insn, asi, table, false, false, stack_check_actions, NULL);
  76 }
  77
  78 const struct decode_checker t32_stack_checker[NUM_PROBES_T32_ACTIONS] = {
  79         [PROBES_T32_LDMSTM] = {.checker = t32_check_stack},
  80         [PROBES_T32_LDRDSTRD] = {.checker = t32_check_stack},
  81         [PROBES_T32_LDRSTR] = {.checker = t32_check_stack},
  82 };
  83
  84 /*
  85  * See following comments. This insn must be 'push'.
  86  */
  87 static enum probes_insn __kprobes t16_check_stack(probes_opcode_t insn,
  88                 struct arch_probes_insn *asi,
  89                 const struct decode_header *h)
  90 {
  91         unsigned int reglist = insn & 0x1ff;
  92         asi->stack_space = hweight32(reglist) * 4;
  93         return INSN_GOOD;
  94 }
  95
  96 /*
  97  * T16 encoding is simple: only the 'push' insn can need extra stack space.
  98  * Other insns, like str, can only use r0-r7 as Rn.
  99  */
 100 const struct decode_checker t16_stack_checker[NUM_PROBES_T16_ACTIONS] = {
 101         [PROBES_T16_PUSH] = {.checker = t16_check_stack},
 102 };