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574e2b51 VK |
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 | ||
50913336 VK |
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) | |
46 | ARM_OK( .arm ) | |
47 | .endm | |
48 | ||
49 | .macro thumb_slot n | |
50 | .org sigreturn_codes + 12 * (\n) + 8 | |
51 | .thumb | |
52 | .endm | |
53 | ||
574e2b51 VK |
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 | ||
50913336 | 69 | .align |
574e2b51 VK |
70 | |
71 | sigreturn_codes: | |
72 | ||
73 | /* ARM sigreturn syscall code snippet */ | |
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74 | arm_slot 0 |
75 | ARM_OK( mov r7, #(__NR_sigreturn - __NR_SYSCALL_BASE) ) | |
76 | ARM_OK( swi #(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE) ) | |
574e2b51 VK |
77 | |
78 | /* Thumb sigreturn syscall code snippet */ | |
50913336 | 79 | thumb_slot 0 |
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80 | movs r7, #(__NR_sigreturn - __NR_SYSCALL_BASE) |
81 | swi #0 | |
82 | ||
83 | /* ARM sigreturn_rt syscall code snippet */ | |
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84 | arm_slot 1 |
85 | ARM_OK( mov r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE) ) | |
86 | ARM_OK( swi #(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE) ) | |
574e2b51 VK |
87 | |
88 | /* Thumb sigreturn_rt syscall code snippet */ | |
50913336 | 89 | thumb_slot 1 |
574e2b51 VK |
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 | */ | |
50913336 | 99 | arm_slot 2 |
574e2b51 VK |
100 | .space 4 |
101 | ||
102 | .size sigreturn_codes, . - sigreturn_codes |