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