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