1/*
2 * sigreturn_codes.S - code sinpets for sigreturn syscalls
3 *
4 * Created by:	Victor Kamensky, 2013-08-13
5 * Copyright:	(C) 2013  Linaro Limited
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 * GNU General Public License for more details.
15 */
16
17#include <asm/assembler.h>
18#include <asm/asm-offsets.h>
19#include <asm/unistd.h>
20
21/*
22 * For ARM syscalls, we encode the syscall number into the instruction.
23 * With EABI, the syscall number has to be loaded into r7. As result
24 * ARM syscall sequence snippet will have move and svc in .arm encoding
25 *
26 * For Thumb syscalls, we pass the syscall number via r7.  We therefore
27 * need two 16-bit instructions in .thumb encoding
28 *
29 * Please note sigreturn_codes code are not executed in place. Instead
30 * they just copied by kernel into appropriate places. Code inside of
31 * arch/arm/kernel/signal.c is very sensitive to layout of these code
32 * snippets.
33 */
34
35/*
36 * In CPU_THUMBONLY case kernel arm opcodes are not allowed.
37 * Note in this case codes skips those instructions but it uses .org
38 * directive to keep correct layout of sigreturn_codes array.
39 */
40#ifndef CONFIG_CPU_THUMBONLY
41#define ARM_OK(code...)	code
42#else
43#define ARM_OK(code...)
44#endif
45
46	.macro arm_slot n
47	.org	sigreturn_codes + 12 * (\n)
48ARM_OK(	.arm	)
49	.endm
50
51	.macro thumb_slot n
52	.org	sigreturn_codes + 12 * (\n) + 8
53	.thumb
54	.endm
55
56	.macro arm_fdpic_slot n
57	.org	sigreturn_codes + 24 + 20 * (\n)
58ARM_OK(	.arm	)
59	.endm
60
61	.macro thumb_fdpic_slot n
62	.org	sigreturn_codes + 24 + 20 * (\n) + 12
63	.thumb
64	.endm
65
66
67#if __LINUX_ARM_ARCH__ <= 4
68	/*
69	 * Note we manually set minimally required arch that supports
70	 * required thumb opcodes for early arch versions. It is OK
71	 * for this file to be used in combination with other
72	 * lower arch variants, since these code snippets are only
73	 * used as input data.
74	 */
75	.arch armv4t
76#endif
77
78	.section .rodata
79	.global sigreturn_codes
80	.type	sigreturn_codes, #object
81
82	.align
83
84sigreturn_codes:
85
86	/* ARM sigreturn syscall code snippet */
87	arm_slot 0
88ARM_OK(	mov	r7, #(__NR_sigreturn - __NR_SYSCALL_BASE)	)
89ARM_OK(	swi	#(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE)	)
90
91	/* Thumb sigreturn syscall code snippet */
92	thumb_slot 0
93	movs	r7, #(__NR_sigreturn - __NR_SYSCALL_BASE)
94	swi	#0
95
96	/* ARM sigreturn_rt syscall code snippet */
97	arm_slot 1
98ARM_OK(	mov	r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE)	)
99ARM_OK(	swi	#(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE)	)
100
101	/* Thumb sigreturn_rt syscall code snippet */
102	thumb_slot 1
103	movs	r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE)
104	swi	#0
105
106	/* ARM sigreturn restorer FDPIC bounce code snippet */
107	arm_fdpic_slot 0
108ARM_OK(	ldr	r3, [sp, #SIGFRAME_RC3_OFFSET] )
109ARM_OK(	ldmia	r3, {r3, r9} )
110#ifdef CONFIG_ARM_THUMB
111ARM_OK(	bx	r3 )
112#else
113ARM_OK(	ret	r3 )
114#endif
115
116	/* Thumb sigreturn restorer FDPIC bounce code snippet */
117	thumb_fdpic_slot 0
118	ldr	r3, [sp, #SIGFRAME_RC3_OFFSET]
119	ldmia	r3, {r2, r3}
120	mov	r9, r3
121	bx	r2
122
123	/* ARM sigreturn_rt restorer FDPIC bounce code snippet */
124	arm_fdpic_slot 1
125ARM_OK(	ldr	r3, [sp, #RT_SIGFRAME_RC3_OFFSET] )
126ARM_OK(	ldmia	r3, {r3, r9} )
127#ifdef CONFIG_ARM_THUMB
128ARM_OK(	bx	r3 )
129#else
130ARM_OK(	ret	r3 )
131#endif
132
133	/* Thumb sigreturn_rt restorer FDPIC bounce code snippet */
134	thumb_fdpic_slot 1
135	ldr	r3, [sp, #RT_SIGFRAME_RC3_OFFSET]
136	ldmia	r3, {r2, r3}
137	mov	r9, r3
138	bx	r2
139
140	/*
141	 * Note on additional space: setup_return in signal.c
142	 * always copies the same number of words regardless whether
143	 * it is thumb case or not, so we need one additional padding
144	 * word after the last entry.
145	 */
146	.space	4
147
148	.size	sigreturn_codes, . - sigreturn_codes
149