LXR linux/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
  13static 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
  78const 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 */
  87static 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 */
 100const struct decode_checker t16_stack_checker[NUM_PROBES_T16_ACTIONS] = {
 101        [PROBES_T16_PUSH] = {.checker = t16_check_stack},
 102};
 103