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