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#if __LINUX_ARM_ARCH__ <= 4
34	/*
35	 * Note we manually set minimally required arch that supports
36	 * required thumb opcodes for early arch versions. It is OK
37	 * for this file to be used in combination with other
38	 * lower arch variants, since these code snippets are only
39	 * used as input data.
40	 */
41	.arch armv4t
42#endif
43
44	.section .rodata
45	.global sigreturn_codes
46	.type	sigreturn_codes, #object
47
48	.arm
49
50sigreturn_codes:
51
52	/* ARM sigreturn syscall code snippet */
53	mov	r7, #(__NR_sigreturn - __NR_SYSCALL_BASE)
54	swi	#(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE)
55
56	/* Thumb sigreturn syscall code snippet */
57	.thumb
58	movs	r7, #(__NR_sigreturn - __NR_SYSCALL_BASE)
59	swi	#0
60
61	/* ARM sigreturn_rt syscall code snippet */
62	.arm
63	mov	r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE)
64	swi	#(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE)
65
66	/* Thumb sigreturn_rt syscall code snippet */
67	.thumb
68	movs	r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE)
69	swi	#0
70
71	/*
72	 * Note on addtional space: setup_return in signal.c
73	 * algorithm uses two words copy regardless whether
74	 * it is thumb case or not, so we need additional
75	 * word after real last entry.
76	 */
77	.arm
78	.space	4
79
80	.size	sigreturn_codes, . - sigreturn_codes
81