1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * sigreturn_codes.S - code sinpets for sigreturn syscalls
4 *
5 * Created by:	Victor Kamensky, 2013-08-13
6 * Copyright:	(C) 2013  Linaro Limited
7 */
8
9#include <asm/assembler.h>
10#include <asm/asm-offsets.h>
11#include <asm/unistd.h>
12
13/*
14 * For ARM syscalls, we encode the syscall number into the instruction.
15 * With EABI, the syscall number has to be loaded into r7. As result
16 * ARM syscall sequence snippet will have move and svc in .arm encoding
17 *
18 * For Thumb syscalls, we pass the syscall number via r7.  We therefore
19 * need two 16-bit instructions in .thumb encoding
20 *
21 * Please note sigreturn_codes code are not executed in place. Instead
22 * they just copied by kernel into appropriate places. Code inside of
23 * arch/arm/kernel/signal.c is very sensitive to layout of these code
24 * snippets.
25 */
26
27/*
28 * In CPU_THUMBONLY case kernel arm opcodes are not allowed.
29 * Note in this case codes skips those instructions but it uses .org
30 * directive to keep correct layout of sigreturn_codes array.
31 */
32#ifndef CONFIG_CPU_THUMBONLY
33#define ARM_OK(code...)	code
34#else
35#define ARM_OK(code...)
36#endif
37
38	.macro arm_slot n
39	.org	sigreturn_codes + 12 * (\n)
40ARM_OK(	.arm	)
41	.endm
42
43	.macro thumb_slot n
44	.org	sigreturn_codes + 12 * (\n) + 8
45	.thumb
46	.endm
47
48	.macro arm_fdpic_slot n
49	.org	sigreturn_codes + 24 + 20 * (\n)
50ARM_OK(	.arm	)
51	.endm
52
53	.macro thumb_fdpic_slot n
54	.org	sigreturn_codes + 24 + 20 * (\n) + 12
55	.thumb
56	.endm
57
58
59#if __LINUX_ARM_ARCH__ <= 4
60	/*
61	 * Note we manually set minimally required arch that supports
62	 * required thumb opcodes for early arch versions. It is OK
63	 * for this file to be used in combination with other
64	 * lower arch variants, since these code snippets are only
65	 * used as input data.
66	 */
67	.arch armv4t
68#endif
69
70	.section .rodata
71	.global sigreturn_codes
72	.type	sigreturn_codes, #object
73
74	.align
75
76sigreturn_codes:
77
78	/* ARM sigreturn syscall code snippet */
79	arm_slot 0
80ARM_OK(	mov	r7, #(__NR_sigreturn - __NR_SYSCALL_BASE)	)
81ARM_OK(	swi	#(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE)	)
82
83	/* Thumb sigreturn syscall code snippet */
84	thumb_slot 0
85	movs	r7, #(__NR_sigreturn - __NR_SYSCALL_BASE)
86	swi	#0
87
88	/* ARM sigreturn_rt syscall code snippet */
89	arm_slot 1
90ARM_OK(	mov	r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE)	)
91ARM_OK(	swi	#(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE)	)
92
93	/* Thumb sigreturn_rt syscall code snippet */
94	thumb_slot 1
95	movs	r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE)
96	swi	#0
97
98	/* ARM sigreturn restorer FDPIC bounce code snippet */
99	arm_fdpic_slot 0
100ARM_OK(	ldr	r3, [sp, #SIGFRAME_RC3_OFFSET] )
101ARM_OK(	ldmia	r3, {r3, r9} )
102#ifdef CONFIG_ARM_THUMB
103ARM_OK(	bx	r3 )
104#else
105ARM_OK(	ret	r3 )
106#endif
107
108	/* Thumb sigreturn restorer FDPIC bounce code snippet */
109	thumb_fdpic_slot 0
110	ldr	r3, [sp, #SIGFRAME_RC3_OFFSET]
111	ldmia	r3, {r2, r3}
112	mov	r9, r3
113	bx	r2
114
115	/* ARM sigreturn_rt restorer FDPIC bounce code snippet */
116	arm_fdpic_slot 1
117ARM_OK(	ldr	r3, [sp, #RT_SIGFRAME_RC3_OFFSET] )
118ARM_OK(	ldmia	r3, {r3, r9} )
119#ifdef CONFIG_ARM_THUMB
120ARM_OK(	bx	r3 )
121#else
122ARM_OK(	ret	r3 )
123#endif
124
125	/* Thumb sigreturn_rt restorer FDPIC bounce code snippet */
126	thumb_fdpic_slot 1
127	ldr	r3, [sp, #RT_SIGFRAME_RC3_OFFSET]
128	ldmia	r3, {r2, r3}
129	mov	r9, r3
130	bx	r2
131
132	/*
133	 * Note on additional space: setup_return in signal.c
134	 * always copies the same number of words regardless whether
135	 * it is thumb case or not, so we need one additional padding
136	 * word after the last entry.
137	 */
138	.space	4
139
140	.size	sigreturn_codes, . - sigreturn_codes
141