1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * arch/arm/probes/kprobes/actions-common.c
4 *
5 * Copyright (C) 2011 Jon Medhurst <tixy@yxit.co.uk>.
6 *
7 * Some contents moved here from arch/arm/include/asm/kprobes-arm.c which is
8 * Copyright (C) 2006, 2007 Motorola Inc.
9 */
10
11#include <linux/kernel.h>
12#include <linux/kprobes.h>
13#include <asm/opcodes.h>
14
15#include "core.h"
16
17
18static void __kprobes simulate_ldm1stm1(probes_opcode_t insn,
19		struct arch_probes_insn *asi,
20		struct pt_regs *regs)
21{
22	int rn = (insn >> 16) & 0xf;
23	int lbit = insn & (1 << 20);
24	int wbit = insn & (1 << 21);
25	int ubit = insn & (1 << 23);
26	int pbit = insn & (1 << 24);
27	long *addr = (long *)regs->uregs[rn];
28	int reg_bit_vector;
29	int reg_count;
30
31	reg_count = 0;
32	reg_bit_vector = insn & 0xffff;
33	while (reg_bit_vector) {
34		reg_bit_vector &= (reg_bit_vector - 1);
35		++reg_count;
36	}
37
38	if (!ubit)
39		addr -= reg_count;
40	addr += (!pbit == !ubit);
41
42	reg_bit_vector = insn & 0xffff;
43	while (reg_bit_vector) {
44		int reg = __ffs(reg_bit_vector);
45		reg_bit_vector &= (reg_bit_vector - 1);
46		if (lbit)
47			regs->uregs[reg] = *addr++;
48		else
49			*addr++ = regs->uregs[reg];
50	}
51
52	if (wbit) {
53		if (!ubit)
54			addr -= reg_count;
55		addr -= (!pbit == !ubit);
56		regs->uregs[rn] = (long)addr;
57	}
58}
59
60static void __kprobes simulate_stm1_pc(probes_opcode_t insn,
61	struct arch_probes_insn *asi,
62	struct pt_regs *regs)
63{
64	unsigned long addr = regs->ARM_pc - 4;
65
66	regs->ARM_pc = (long)addr + str_pc_offset;
67	simulate_ldm1stm1(insn, asi, regs);
68	regs->ARM_pc = (long)addr + 4;
69}
70
71static void __kprobes simulate_ldm1_pc(probes_opcode_t insn,
72	struct arch_probes_insn *asi,
73	struct pt_regs *regs)
74{
75	simulate_ldm1stm1(insn, asi, regs);
76	load_write_pc(regs->ARM_pc, regs);
77}
78
79static void __kprobes
80emulate_generic_r0_12_noflags(probes_opcode_t insn,
81	struct arch_probes_insn *asi, struct pt_regs *regs)
82{
83	register void *rregs asm("r1") = regs;
84	register void *rfn asm("lr") = asi->insn_fn;
85
86	__asm__ __volatile__ (
87ARM(		"stmdb	sp!, {%[regs], r11}	\n\t"	)
88THUMB(		"stmdb	sp!, {%[regs], r7}	\n\t"	)
89		"ldmia	%[regs], {r0-r12}	\n\t"
90#if __LINUX_ARM_ARCH__ >= 6
91		"blx	%[fn]			\n\t"
92#else
93		"str	%[fn], [sp, #-4]!	\n\t"
94		"adr	lr, 1f			\n\t"
95		"ldr	pc, [sp], #4		\n\t"
96		"1:				\n\t"
97#endif
98		"ldr	lr, [sp], #4		\n\t" /* lr = regs */
99		"stmia	lr, {r0-r12}		\n\t"
100ARM(		"ldr	r11, [sp], #4		\n\t"	)
101THUMB(		"ldr	r7, [sp], #4		\n\t"	)
102		: [regs] "=r" (rregs), [fn] "=r" (rfn)
103		: "0" (rregs), "1" (rfn)
104		: "r0", "r2", "r3", "r4", "r5", "r6", ARM("r7") THUMB("r11"),
105		  "r8", "r9", "r10", "r12", "memory", "cc"
106		);
107}
108
109static void __kprobes
110emulate_generic_r2_14_noflags(probes_opcode_t insn,
111	struct arch_probes_insn *asi, struct pt_regs *regs)
112{
113	emulate_generic_r0_12_noflags(insn, asi,
114		(struct pt_regs *)(regs->uregs+2));
115}
116
117static void __kprobes
118emulate_ldm_r3_15(probes_opcode_t insn,
119	struct arch_probes_insn *asi, struct pt_regs *regs)
120{
121	emulate_generic_r0_12_noflags(insn, asi,
122		(struct pt_regs *)(regs->uregs+3));
123	load_write_pc(regs->ARM_pc, regs);
124}
125
126enum probes_insn __kprobes
127kprobe_decode_ldmstm(probes_opcode_t insn, struct arch_probes_insn *asi,
128		const struct decode_header *h)
129{
130	probes_insn_handler_t *handler = 0;
131	unsigned reglist = insn & 0xffff;
132	int is_ldm = insn & 0x100000;
133	int rn = (insn >> 16) & 0xf;
134
135	if (rn <= 12 && (reglist & 0xe000) == 0) {
136		/* Instruction only uses registers in the range R0..R12 */
137		handler = emulate_generic_r0_12_noflags;
138
139	} else if (rn >= 2 && (reglist & 0x8003) == 0) {
140		/* Instruction only uses registers in the range R2..R14 */
141		rn -= 2;
142		reglist >>= 2;
143		handler = emulate_generic_r2_14_noflags;
144
145	} else if (rn >= 3 && (reglist & 0x0007) == 0) {
146		/* Instruction only uses registers in the range R3..R15 */
147		if (is_ldm && (reglist & 0x8000)) {
148			rn -= 3;
149			reglist >>= 3;
150			handler = emulate_ldm_r3_15;
151		}
152	}
153
154	if (handler) {
155		/* We can emulate the instruction in (possibly) modified form */
156		asi->insn[0] = __opcode_to_mem_arm((insn & 0xfff00000) |
157						   (rn << 16) | reglist);
158		asi->insn_handler = handler;
159		return INSN_GOOD;
160	}
161
162	/* Fallback to slower simulation... */
163	if (reglist & 0x8000)
164		handler = is_ldm ? simulate_ldm1_pc : simulate_stm1_pc;
165	else
166		handler = simulate_ldm1stm1;
167	asi->insn_handler = handler;
168	return INSN_GOOD_NO_SLOT;
169}
170
171