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/unistd.h>
18
19/*
20 * For ARM syscalls, we encode the syscall number into the instruction.
21 * With EABI, the syscall number has to be loaded into r7. As result
22 * ARM syscall sequence snippet will have move and svc in .arm encoding
23 *
24 * For Thumb syscalls, we pass the syscall number via r7.  We therefore
25 * need two 16-bit instructions in .thumb encoding
26 *
27 * Please note sigreturn_codes code are not executed in place. Instead
28 * they just copied by kernel into appropriate places. Code inside of
29 * arch/arm/kernel/signal.c is very sensitive to layout of these code
30 * snippets.
31 */
32
33/*
34 * In CPU_THUMBONLY case kernel arm opcodes are not allowed.
35 * Note in this case codes skips those instructions but it uses .org
36 * directive to keep correct layout of sigreturn_codes array.
37 */
38#ifndef CONFIG_CPU_THUMBONLY
39#define ARM_OK(code...)	code
40#else
41#define ARM_OK(code...)
42#endif
43
44	.macro arm_slot n
45	.org	sigreturn_codes + 12 * (\n)
46ARM_OK(	.arm	)
47	.endm
48
49	.macro thumb_slot n
50	.org	sigreturn_codes + 12 * (\n) + 8
51	.thumb
52	.endm
53
54#if __LINUX_ARM_ARCH__ <= 4
55	/*
56	 * Note we manually set minimally required arch that supports
57	 * required thumb opcodes for early arch versions. It is OK
58	 * for this file to be used in combination with other
59	 * lower arch variants, since these code snippets are only
60	 * used as input data.
61	 */
62	.arch armv4t
63#endif
64
65	.section .rodata
66	.global sigreturn_codes
67	.type	sigreturn_codes, #object
68
69	.align
70
71sigreturn_codes:
72
73	/* ARM sigreturn syscall code snippet */
74	arm_slot 0
75ARM_OK(	mov	r7, #(__NR_sigreturn - __NR_SYSCALL_BASE)	)
76ARM_OK(	swi	#(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE)	)
77
78	/* Thumb sigreturn syscall code snippet */
79	thumb_slot 0
80	movs	r7, #(__NR_sigreturn - __NR_SYSCALL_BASE)
81	swi	#0
82
83	/* ARM sigreturn_rt syscall code snippet */
84	arm_slot 1
85ARM_OK(	mov	r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE)	)
86ARM_OK(	swi	#(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE)	)
87
88	/* Thumb sigreturn_rt syscall code snippet */
89	thumb_slot 1
90	movs	r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE)
91	swi	#0
92
93	/*
94	 * Note on addtional space: setup_return in signal.c
95	 * algorithm uses two words copy regardless whether
96	 * it is thumb case or not, so we need additional
97	 * word after real last entry.
98	 */
99	arm_slot 2
100	.space	4
101
102	.size	sigreturn_codes, . - sigreturn_codes
103