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/*
* sigreturn_codes.S - code sinpets for sigreturn syscalls
*
* Created by: Victor Kamensky, 2013-08-13
* Copyright: (C) 2013 Linaro Limited
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <asm/assembler.h>
#include <asm/asm-offsets.h>
#include <asm/unistd.h>
/*
* For ARM syscalls, we encode the syscall number into the instruction.
* With EABI, the syscall number has to be loaded into r7. As result
* ARM syscall sequence snippet will have move and svc in .arm encoding
*
* For Thumb syscalls, we pass the syscall number via r7. We therefore
* need two 16-bit instructions in .thumb encoding
*
* Please note sigreturn_codes code are not executed in place. Instead
* they just copied by kernel into appropriate places. Code inside of
* arch/arm/kernel/signal.c is very sensitive to layout of these code
* snippets.
*/
/*
* In CPU_THUMBONLY case kernel arm opcodes are not allowed.
* Note in this case codes skips those instructions but it uses .org
* directive to keep correct layout of sigreturn_codes array.
*/
#ifndef CONFIG_CPU_THUMBONLY
#define ARM_OK(code...) code
#else
#define ARM_OK(code...)
#endif
.macro arm_slot n
.org sigreturn_codes + 12 * (\n)
ARM_OK( .arm )
.endm
.macro thumb_slot n
.org sigreturn_codes + 12 * (\n) + 8
.thumb
.endm
.macro arm_fdpic_slot n
.org sigreturn_codes + 24 + 20 * (\n)
ARM_OK( .arm )
.endm
.macro thumb_fdpic_slot n
.org sigreturn_codes + 24 + 20 * (\n) + 12
.thumb
.endm
#if __LINUX_ARM_ARCH__ <= 4
/*
* Note we manually set minimally required arch that supports
* required thumb opcodes for early arch versions. It is OK
* for this file to be used in combination with other
* lower arch variants, since these code snippets are only
* used as input data.
*/
.arch armv4t
#endif
.section .rodata
.global sigreturn_codes
.type sigreturn_codes, #object
.align
sigreturn_codes:
/* ARM sigreturn syscall code snippet */
arm_slot 0
ARM_OK( mov r7, #(__NR_sigreturn - __NR_SYSCALL_BASE) )
ARM_OK( swi #(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE) )
/* Thumb sigreturn syscall code snippet */
thumb_slot 0
movs r7, #(__NR_sigreturn - __NR_SYSCALL_BASE)
swi #0
/* ARM sigreturn_rt syscall code snippet */
arm_slot 1
ARM_OK( mov r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE) )
ARM_OK( swi #(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE) )
/* Thumb sigreturn_rt syscall code snippet */
thumb_slot 1
movs r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE)
swi #0
/* ARM sigreturn restorer FDPIC bounce code snippet */
arm_fdpic_slot 0
ARM_OK( ldr r3, [sp, #SIGFRAME_RC3_OFFSET] )
ARM_OK( ldmia r3, {r3, r9} )
#ifdef CONFIG_ARM_THUMB
ARM_OK( bx r3 )
#else
ARM_OK( ret r3 )
#endif
/* Thumb sigreturn restorer FDPIC bounce code snippet */
thumb_fdpic_slot 0
ldr r3, [sp, #SIGFRAME_RC3_OFFSET]
ldmia r3, {r2, r3}
mov r9, r3
bx r2
/* ARM sigreturn_rt restorer FDPIC bounce code snippet */
arm_fdpic_slot 1
ARM_OK( ldr r3, [sp, #RT_SIGFRAME_RC3_OFFSET] )
ARM_OK( ldmia r3, {r3, r9} )
#ifdef CONFIG_ARM_THUMB
ARM_OK( bx r3 )
#else
ARM_OK( ret r3 )
#endif
/* Thumb sigreturn_rt restorer FDPIC bounce code snippet */
thumb_fdpic_slot 1
ldr r3, [sp, #RT_SIGFRAME_RC3_OFFSET]
ldmia r3, {r2, r3}
mov r9, r3
bx r2
/*
* Note on additional space: setup_return in signal.c
* always copies the same number of words regardless whether
* it is thumb case or not, so we need one additional padding
* word after the last entry.
*/
.space 4
.size sigreturn_codes, . - sigreturn_codes
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