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};