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