/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * sigreturn_codes.S - code sinpets for sigreturn syscalls
 *
 * Created by:  Victor Kamensky, 2013-08-13
 * Copyright:   (C) 2013  Linaro Limited
 */

#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