arch/arm64/kernel/insn.c

   1 /*
   2  * Copyright (C) 2013 Huawei Ltd.
   3  * Author: Jiang Liu <liuj97@gmail.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16  */
  17 #include <linux/compiler.h>
  18 #include <linux/kernel.h>
  19 #include <asm/insn.h>
  20
  21 static int aarch64_insn_encoding_class[] = {
  22         AARCH64_INSN_CLS_UNKNOWN,
  23         AARCH64_INSN_CLS_UNKNOWN,
  24         AARCH64_INSN_CLS_UNKNOWN,
  25         AARCH64_INSN_CLS_UNKNOWN,
  26         AARCH64_INSN_CLS_LDST,
  27         AARCH64_INSN_CLS_DP_REG,
  28         AARCH64_INSN_CLS_LDST,
  29         AARCH64_INSN_CLS_DP_FPSIMD,
  30         AARCH64_INSN_CLS_DP_IMM,
  31         AARCH64_INSN_CLS_DP_IMM,
  32         AARCH64_INSN_CLS_BR_SYS,
  33         AARCH64_INSN_CLS_BR_SYS,
  34         AARCH64_INSN_CLS_LDST,
  35         AARCH64_INSN_CLS_DP_REG,
  36         AARCH64_INSN_CLS_LDST,
  37         AARCH64_INSN_CLS_DP_FPSIMD,
  38 };
  39
  40 enum aarch64_insn_encoding_class __kprobes aarch64_get_insn_class(u32 insn)
  41 {
  42         return aarch64_insn_encoding_class[(insn >> 25) & 0xf];
  43 }
  44
  45 /* NOP is an alias of HINT */
  46 bool __kprobes aarch64_insn_is_nop(u32 insn)
  47 {
  48         if (!aarch64_insn_is_hint(insn))
  49                 return false;
  50
  51         switch (insn & 0xFE0) {
  52         case AARCH64_INSN_HINT_YIELD:
  53         case AARCH64_INSN_HINT_WFE:
  54         case AARCH64_INSN_HINT_WFI:
  55         case AARCH64_INSN_HINT_SEV:
  56         case AARCH64_INSN_HINT_SEVL:
  57                 return false;
  58         default:
  59                 return true;
  60         }
  61 }
  62
  63 static bool __kprobes __aarch64_insn_hotpatch_safe(u32 insn)
  64 {
  65         if (aarch64_get_insn_class(insn) != AARCH64_INSN_CLS_BR_SYS)
  66                 return false;
  67
  68         return  aarch64_insn_is_b(insn) ||
  69                 aarch64_insn_is_bl(insn) ||
  70                 aarch64_insn_is_svc(insn) ||
  71                 aarch64_insn_is_hvc(insn) ||
  72                 aarch64_insn_is_smc(insn) ||
  73                 aarch64_insn_is_brk(insn) ||
  74                 aarch64_insn_is_nop(insn);
  75 }
  76
  77 /*
  78  * ARM Architecture Reference Manual for ARMv8 Profile-A, Issue A.a
  79  * Section B2.6.5 "Concurrent modification and execution of instructions":
  80  * Concurrent modification and execution of instructions can lead to the
  81  * resulting instruction performing any behavior that can be achieved by
  82  * executing any sequence of instructions that can be executed from the
  83  * same Exception level, except where the instruction before modification
  84  * and the instruction after modification is a B, BL, NOP, BKPT, SVC, HVC,
  85  * or SMC instruction.
  86  */
  87 bool __kprobes aarch64_insn_hotpatch_safe(u32 old_insn, u32 new_insn)
  88 {
  89         return __aarch64_insn_hotpatch_safe(old_insn) &&
  90                __aarch64_insn_hotpatch_safe(new_insn);
  91 }