xref: /openbmc/linux/arch/arm/kernel/phys2virt.S (revision bbaf1ff0) 
1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 *  Copyright (C) 1994-2002 Russell King
4 *  Copyright (c) 2003, 2020 ARM Limited
5 *  All Rights Reserved
6 */
7
8#include <linux/init.h>
9#include <linux/linkage.h>
10#include <asm/assembler.h>
11#include <asm/page.h>
12
13#ifdef __ARMEB__
14#define LOW_OFFSET	0x4
15#define HIGH_OFFSET	0x0
16#else
17#define LOW_OFFSET	0x0
18#define HIGH_OFFSET	0x4
19#endif
20
21/*
22 * __fixup_pv_table - patch the stub instructions with the delta between
23 *                    PHYS_OFFSET and PAGE_OFFSET, which is assumed to be
24 *                    2 MiB aligned.
25 *
26 * Called from head.S, which expects the following registers to be preserved:
27 *   r1 = machine no, r2 = atags or dtb,
28 *   r8 = phys_offset, r9 = cpuid, r10 = procinfo
29 */
30	__HEAD
31ENTRY(__fixup_pv_table)
32	mov	r0, r8, lsr #PAGE_SHIFT	@ convert to PFN
33	str_l	r0, __pv_phys_pfn_offset, r3
34
35	adr_l	r0, __pv_offset
36	subs	r3, r8, #PAGE_OFFSET	@ PHYS_OFFSET - PAGE_OFFSET
37	mvn	ip, #0
38	strcc	ip, [r0, #HIGH_OFFSET]	@ save to __pv_offset high bits
39	str	r3, [r0, #LOW_OFFSET]	@ save to __pv_offset low bits
40
41	mov	r0, r3, lsr #21		@ constant for add/sub instructions
42	teq	r3, r0, lsl #21 	@ must be 2 MiB aligned
43	bne	0f
44
45	adr_l	r4, __pv_table_begin
46	adr_l	r5, __pv_table_end
47	b	__fixup_a_pv_table
48
490:	mov	r0, r0			@ deadloop on error
50	b	0b
51ENDPROC(__fixup_pv_table)
52
53	.text
54__fixup_a_pv_table:
55	adr_l	r6, __pv_offset
56	ldr	r0, [r6, #HIGH_OFFSET]	@ pv_offset high word
57	ldr	r6, [r6, #LOW_OFFSET]	@ pv_offset low word
58	cmn	r0, #1
59#ifdef CONFIG_THUMB2_KERNEL
60	@
61	@ The Thumb-2 versions of the patchable sequences are
62	@
63	@ phys-to-virt:			movw	<reg>, #offset<31:21>
64	@				lsl	<reg>, #21
65	@				sub	<VA>, <PA>, <reg>
66	@
67	@ virt-to-phys (non-LPAE):	movw	<reg>, #offset<31:21>
68	@				lsl	<reg>, #21
69	@				add	<PA>, <VA>, <reg>
70	@
71	@ virt-to-phys (LPAE):		movw	<reg>, #offset<31:21>
72	@				lsl	<reg>, #21
73	@				adds	<PAlo>, <VA>, <reg>
74	@				mov	<PAhi>, #offset<39:32>
75	@				adc	<PAhi>, <PAhi>, #0
76	@
77	@ In the non-LPAE case, all patchable instructions are MOVW
78	@ instructions, where we need to patch in the offset into the
79	@ second halfword of the opcode (the 16-bit immediate is encoded
80	@ as imm4:i:imm3:imm8)
81	@
82	@       15       11 10  9           4 3    0  15  14  12 11 8 7    0
83	@      +-----------+---+-------------+------++---+------+----+------+
84	@ MOVW | 1 1 1 1 0 | i | 1 0 0 1 0 0 | imm4 || 0 | imm3 | Rd | imm8 |
85	@      +-----------+---+-------------+------++---+------+----+------+
86	@
87	@ In the LPAE case, we also need to patch in the high word of the
88	@ offset into the immediate field of the MOV instruction, or patch it
89	@ to a MVN instruction if the offset is negative. In this case, we
90	@ need to inspect the first halfword of the opcode, to check whether
91	@ it is MOVW or MOV/MVN, and to perform the MOV to MVN patching if
92	@ needed. The encoding of the immediate is rather complex for values
93	@ of i:imm3 != 0b0000, but fortunately, we never need more than 8 lower
94	@ order bits, which can be patched into imm8 directly (and i:imm3
95	@ cleared)
96	@
97	@      15       11 10  9        5         0  15  14  12 11 8 7    0
98	@     +-----------+---+---------------------++---+------+----+------+
99	@ MOV | 1 1 1 1 0 | i | 0 0 0 1 0 0 1 1 1 1 || 0 | imm3 | Rd | imm8 |
100	@ MVN | 1 1 1 1 0 | i | 0 0 0 1 1 0 1 1 1 1 || 0 | imm3 | Rd | imm8 |
101	@     +-----------+---+---------------------++---+------+----+------+
102	@
103	moveq	r0, #0x200000		@ set bit 21, mov to mvn instruction
104	lsrs	r3, r6, #29		@ isolate top 3 bits of displacement
105	ubfx	r6, r6, #21, #8		@ put bits 28:21 into the MOVW imm8 field
106	bfi	r6, r3, #12, #3		@ put bits 31:29 into the MOVW imm3 field
107	b	.Lnext
108.Lloop:	add	r7, r4
109	adds	r4, #4			@ clears Z flag
110#ifdef CONFIG_ARM_LPAE
111	ldrh	ip, [r7]
112ARM_BE8(rev16	ip, ip)
113	tst	ip, #0x200		@ MOVW has bit 9 set, MVN has it clear
114	bne	0f			@ skip to MOVW handling (Z flag is clear)
115	bic	ip, #0x20		@ clear bit 5 (MVN -> MOV)
116	orr	ip, ip, r0, lsr #16	@ MOV -> MVN if offset < 0
117ARM_BE8(rev16	ip, ip)
118	strh	ip, [r7]
119	@ Z flag is set
1200:
121#endif
122	ldrh	ip, [r7, #2]
123ARM_BE8(rev16	ip, ip)
124	and	ip, #0xf00		@ clear everything except Rd field
125	orreq	ip, r0			@ Z flag set -> MOV/MVN -> patch in high bits
126	orrne	ip, r6			@ Z flag clear -> MOVW -> patch in low bits
127ARM_BE8(rev16	ip, ip)
128	strh	ip, [r7, #2]
129#else
130#ifdef CONFIG_CPU_ENDIAN_BE8
131@ in BE8, we load data in BE, but instructions still in LE
132#define PV_BIT24	0x00000001
133#define PV_IMM8_MASK	0xff000000
134#define PV_IMMR_MSB	0x00080000
135#else
136#define PV_BIT24	0x01000000
137#define PV_IMM8_MASK	0x000000ff
138#define PV_IMMR_MSB	0x00000800
139#endif
140
141	@
142	@ The ARM versions of the patchable sequences are
143	@
144	@ phys-to-virt:			sub	<VA>, <PA>, #offset<31:24>, lsl #24
145	@				sub	<VA>, <PA>, #offset<23:16>, lsl #16
146	@
147	@ virt-to-phys (non-LPAE):	add	<PA>, <VA>, #offset<31:24>, lsl #24
148	@				add	<PA>, <VA>, #offset<23:16>, lsl #16
149	@
150	@ virt-to-phys (LPAE):		movw	<reg>, #offset<31:20>
151	@				adds	<PAlo>, <VA>, <reg>, lsl #20
152	@				mov	<PAhi>, #offset<39:32>
153	@				adc	<PAhi>, <PAhi>, #0
154	@
155	@ In the non-LPAE case, all patchable instructions are ADD or SUB
156	@ instructions, where we need to patch in the offset into the
157	@ immediate field of the opcode, which is emitted with the correct
158	@ rotation value. (The effective value of the immediate is imm12<7:0>
159	@ rotated right by [2 * imm12<11:8>] bits)
160	@
161	@      31   28 27      23 22  20 19  16 15  12 11    0
162	@      +------+-----------------+------+------+-------+
163	@  ADD | cond | 0 0 1 0 1 0 0 0 |  Rn  |  Rd  | imm12 |
164	@  SUB | cond | 0 0 1 0 0 1 0 0 |  Rn  |  Rd  | imm12 |
165	@  MOV | cond | 0 0 1 1 1 0 1 0 |  Rn  |  Rd  | imm12 |
166	@  MVN | cond | 0 0 1 1 1 1 1 0 |  Rn  |  Rd  | imm12 |
167	@      +------+-----------------+------+------+-------+
168	@
169	@ In the LPAE case, we use a MOVW instruction to carry the low offset
170	@ word, and patch in the high word of the offset into the immediate
171	@ field of the subsequent MOV instruction, or patch it to a MVN
172	@ instruction if the offset is negative. We can distinguish MOVW
173	@ instructions based on bits 23:22 of the opcode, and ADD/SUB can be
174	@ distinguished from MOV/MVN (all using the encodings above) using
175	@ bit 24.
176	@
177	@      31   28 27      23 22  20 19  16 15  12 11    0
178	@      +------+-----------------+------+------+-------+
179	@ MOVW | cond | 0 0 1 1 0 0 0 0 | imm4 |  Rd  | imm12 |
180	@      +------+-----------------+------+------+-------+
181	@
182	moveq	r0, #0x400000		@ set bit 22, mov to mvn instruction
183	mov	r3, r6, lsr #16		@ put offset bits 31-16 into r3
184	mov	r6, r6, lsr #24		@ put offset bits 31-24 into r6
185	and	r3, r3, #0xf0		@ only keep offset bits 23-20 in r3
186	b	.Lnext
187.Lloop:	ldr	ip, [r7, r4]
188#ifdef CONFIG_ARM_LPAE
189	tst	ip, #PV_BIT24		@ ADD/SUB have bit 24 clear
190	beq	1f
191ARM_BE8(rev	ip, ip)
192	tst	ip, #0xc00000		@ MOVW has bits 23:22 clear
193	bic	ip, ip, #0x400000	@ clear bit 22
194	bfc	ip, #0, #12		@ clear imm12 field of MOV[W] instruction
195	orreq	ip, ip, r6, lsl #4	@ MOVW -> mask in offset bits 31-24
196	orreq	ip, ip, r3, lsr #4	@ MOVW -> mask in offset bits 23-20
197	orrne	ip, ip, r0		@ MOV  -> mask in offset bits 7-0 (or bit 22)
198ARM_BE8(rev	ip, ip)
199	b	2f
2001:
201#endif
202	tst	ip, #PV_IMMR_MSB		@ rotation value >= 16 ?
203	bic	ip, ip, #PV_IMM8_MASK
204	orreq	ip, ip, r6 ARM_BE8(, lsl #24)	@ mask in offset bits 31-24
205	orrne	ip, ip, r3 ARM_BE8(, lsl #24)	@ mask in offset bits 23-20
2062:
207	str	ip, [r7, r4]
208	add	r4, r4, #4
209#endif
210
211.Lnext:
212	cmp	r4, r5
213	ldrcc	r7, [r4]		@ use branch for delay slot
214	bcc	.Lloop
215	ret	lr
216ENDPROC(__fixup_a_pv_table)
217
218ENTRY(fixup_pv_table)
219	stmfd	sp!, {r4 - r7, lr}
220	mov	r4, r0			@ r0 = table start
221	add	r5, r0, r1		@ r1 = table size
222	bl	__fixup_a_pv_table
223	ldmfd	sp!, {r4 - r7, pc}
224ENDPROC(fixup_pv_table)
225
226	.data
227	.align	2
228	.globl	__pv_phys_pfn_offset
229	.type	__pv_phys_pfn_offset, %object
230__pv_phys_pfn_offset:
231	.word	0
232	.size	__pv_phys_pfn_offset, . -__pv_phys_pfn_offset
233
234	.globl	__pv_offset
235	.type	__pv_offset, %object
236__pv_offset:
237	.quad	0
238	.size	__pv_offset, . -__pv_offset
239