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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
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