| 1 | /* SPDX-License-Identifier: GPL-2.0-only */ |
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| 2 | /* |
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| 3 | * sigreturn_codes.S - code sinpets for sigreturn syscalls |
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| 4 | * |
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| 5 | * Created by: Victor Kamensky, 2013-08-13 |
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| 6 | * Copyright: (C) 2013 Linaro Limited |
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| 7 | */ |
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| 8 | |
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| 9 | #include <asm/assembler.h> |
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| 10 | #include <asm/asm-offsets.h> |
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| 11 | #include <asm/unistd.h> |
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| 12 | |
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| 13 | /* |
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| 14 | * For ARM syscalls, we encode the syscall number into the instruction. |
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| 15 | * With EABI, the syscall number has to be loaded into r7. As result |
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| 16 | * ARM syscall sequence snippet will have move and svc in .arm encoding |
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| 17 | * |
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| 18 | * For Thumb syscalls, we pass the syscall number via r7. We therefore |
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| 19 | * need two 16-bit instructions in .thumb encoding |
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| 20 | * |
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| 21 | * Please note sigreturn_codes code are not executed in place. Instead |
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| 22 | * they just copied by kernel into appropriate places. Code inside of |
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| 23 | * arch/arm/kernel/signal.c is very sensitive to layout of these code |
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| 24 | * snippets. |
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| 25 | */ |
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| 26 | |
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| 27 | /* |
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| 28 | * In CPU_THUMBONLY case kernel arm opcodes are not allowed. |
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| 29 | * Note in this case codes skips those instructions but it uses .org |
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| 30 | * directive to keep correct layout of sigreturn_codes array. |
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| 31 | */ |
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| 32 | #ifndef CONFIG_CPU_THUMBONLY |
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| 33 | #define ARM_OK(code...) code |
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| 34 | #else |
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| 35 | #define ARM_OK(code...) |
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| 36 | #endif |
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| 37 | |
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| 38 | .macro arm_slot n |
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| 39 | .org sigreturn_codes + 12 * (\n) |
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| 40 | ARM_OK( .arm ) |
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| 41 | .endm |
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| 42 | |
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| 43 | .macro thumb_slot n |
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| 44 | .org sigreturn_codes + 12 * (\n) + 8 |
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| 45 | .thumb |
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| 46 | .endm |
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| 47 | |
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| 48 | .macro arm_fdpic_slot n |
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| 49 | .org sigreturn_codes + 24 + 20 * (\n) |
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| 50 | ARM_OK( .arm ) |
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| 51 | .endm |
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| 52 | |
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| 53 | .macro thumb_fdpic_slot n |
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| 54 | .org sigreturn_codes + 24 + 20 * (\n) + 12 |
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| 55 | .thumb |
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| 56 | .endm |
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| 57 | |
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| 58 | |
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| 59 | #if __LINUX_ARM_ARCH__ <= 4 |
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| 60 | /* |
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| 61 | * Note we manually set minimally required arch that supports |
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| 62 | * required thumb opcodes for early arch versions. It is OK |
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| 63 | * for this file to be used in combination with other |
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| 64 | * lower arch variants, since these code snippets are only |
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| 65 | * used as input data. |
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| 66 | */ |
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| 67 | .arch armv4t |
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| 68 | #endif |
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| 69 | |
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| 70 | .section .rodata |
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| 71 | .global sigreturn_codes |
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| 72 | .type sigreturn_codes, #object |
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| 73 | |
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| 74 | .align |
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| 75 | |
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| 76 | sigreturn_codes: |
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| 77 | |
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| 78 | /* ARM sigreturn syscall code snippet */ |
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| 79 | arm_slot 0 |
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| 80 | ARM_OK( mov r7, #(__NR_sigreturn - __NR_SYSCALL_BASE) ) |
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| 81 | ARM_OK( swi #(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE) ) |
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| 82 | |
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| 83 | /* Thumb sigreturn syscall code snippet */ |
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| 84 | thumb_slot 0 |
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| 85 | movs r7, #(__NR_sigreturn - __NR_SYSCALL_BASE) |
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| 86 | swi #0 |
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| 87 | |
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| 88 | /* ARM sigreturn_rt syscall code snippet */ |
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| 89 | arm_slot 1 |
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| 90 | ARM_OK( mov r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE) ) |
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| 91 | ARM_OK( swi #(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE) ) |
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| 92 | |
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| 93 | /* Thumb sigreturn_rt syscall code snippet */ |
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| 94 | thumb_slot 1 |
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| 95 | movs r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE) |
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| 96 | swi #0 |
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| 97 | |
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| 98 | /* ARM sigreturn restorer FDPIC bounce code snippet */ |
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| 99 | arm_fdpic_slot 0 |
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| 100 | ARM_OK( ldr r3, [sp, #SIGFRAME_RC3_OFFSET] ) |
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| 101 | ARM_OK( ldmia r3, {r3, r9} ) |
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| 102 | #ifdef CONFIG_ARM_THUMB |
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| 103 | ARM_OK( bx r3 ) |
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| 104 | #else |
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| 105 | ARM_OK( ret r3 ) |
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| 106 | #endif |
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| 107 | |
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| 108 | /* Thumb sigreturn restorer FDPIC bounce code snippet */ |
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| 109 | thumb_fdpic_slot 0 |
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| 110 | ldr r3, [sp, #SIGFRAME_RC3_OFFSET] |
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| 111 | ldmia r3, {r2, r3} |
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| 112 | mov r9, r3 |
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| 113 | bx r2 |
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| 114 | |
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| 115 | /* ARM sigreturn_rt restorer FDPIC bounce code snippet */ |
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| 116 | arm_fdpic_slot 1 |
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| 117 | ARM_OK( ldr r3, [sp, #RT_SIGFRAME_RC3_OFFSET] ) |
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| 118 | ARM_OK( ldmia r3, {r3, r9} ) |
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| 119 | #ifdef CONFIG_ARM_THUMB |
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| 120 | ARM_OK( bx r3 ) |
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| 121 | #else |
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| 122 | ARM_OK( ret r3 ) |
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| 123 | #endif |
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| 124 | |
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| 125 | /* Thumb sigreturn_rt restorer FDPIC bounce code snippet */ |
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| 126 | thumb_fdpic_slot 1 |
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| 127 | ldr r3, [sp, #RT_SIGFRAME_RC3_OFFSET] |
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| 128 | ldmia r3, {r2, r3} |
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| 129 | mov r9, r3 |
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| 130 | bx r2 |
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| 131 | |
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| 132 | /* |
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| 133 | * Note on additional space: setup_return in signal.c |
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| 134 | * always copies the same number of words regardless whether |
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| 135 | * it is thumb case or not, so we need one additional padding |
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| 136 | * word after the last entry. |
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| 137 | */ |
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| 138 | .space 4 |
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| 139 | |
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| 140 | .size sigreturn_codes, . - sigreturn_codes |
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| 141 | |
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