/* SPDX-License-Identifier: GPL-2.0-or-later
 * -*- mode: asm -*-
 *
 *  linux/arch/m68k/kernel/entry.S
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 * Linux/m68k support by Hamish Macdonald
 *
 * 68060 fixes by Jesper Skov
 *
 */

/*
 * entry.S  contains the system-call and fault low-level handling routines.
 * This also contains the timer-interrupt handler, as well as all interrupts
 * and faults that can result in a task-switch.
 *
 * NOTE: This code handles signal-recognition, which happens every time
 * after a timer-interrupt and after each system call.
 *
 */

/*
 * 12/03/96 Jes: Currently we only support m68k single-cpu systems, so
 *               all pointers that used to be 'current' are now entry
 *               number 0 in the 'current_set' list.
 *
 *  6/05/00 RZ:  addedd writeback completion after return from sighandler
 *               for 68040
 */

#include <linux/linkage.h>
#include <asm/errno.h>
#include <asm/setup.h>
#include <asm/traps.h>
#include <asm/unistd.h>
#include <asm/asm-offsets.h>
#include <asm/entry.h>

.globl system_call, buserr, trap, resume
.globl sys_call_table
.globl __sys_fork, __sys_clone, __sys_vfork
.globl bad_interrupt
.globl auto_irqhandler_fixup
.globl user_irqvec_fixup

.text
ENTRY(__sys_fork)
        SAVE_SWITCH_STACK
        jbsr    sys_fork
        lea     %sp@(24),%sp
        rts

ENTRY(__sys_clone)
        SAVE_SWITCH_STACK
        pea     %sp@(SWITCH_STACK_SIZE)
        jbsr    m68k_clone
        lea     %sp@(28),%sp
        rts

ENTRY(__sys_vfork)
        SAVE_SWITCH_STACK
        jbsr    sys_vfork
        lea     %sp@(24),%sp
        rts

ENTRY(__sys_clone3)
        SAVE_SWITCH_STACK
        pea     %sp@(SWITCH_STACK_SIZE)
        jbsr    m68k_clone3
        lea     %sp@(28),%sp
        rts

ENTRY(sys_sigreturn)
        SAVE_SWITCH_STACK
        movel   %sp,%a1                         | switch_stack pointer
        lea     %sp@(SWITCH_STACK_SIZE),%a0     | pt_regs pointer
        lea     %sp@(-84),%sp                   | leave a gap
        movel   %a1,%sp@-
        movel   %a0,%sp@-
        jbsr    do_sigreturn
        jra     1f                              | shared with rt_sigreturn()

ENTRY(sys_rt_sigreturn)
        SAVE_SWITCH_STACK
        movel   %sp,%a1                         | switch_stack pointer
        lea     %sp@(SWITCH_STACK_SIZE),%a0     | pt_regs pointer
        lea     %sp@(-84),%sp                   | leave a gap
        movel   %a1,%sp@-
        movel   %a0,%sp@-
        | stack contents:
        |   [original pt_regs address] [original switch_stack address]
        |   [gap] [switch_stack] [pt_regs] [exception frame]
        jbsr    do_rt_sigreturn

1:
        | stack contents now:
        |   [original pt_regs address] [original switch_stack address]
        |   [unused part of the gap] [moved switch_stack] [moved pt_regs]
        |   [replacement exception frame]
        | return value of do_{rt_,}sigreturn() points to moved switch_stack.

        movel   %d0,%sp                         | discard the leftover junk
        RESTORE_SWITCH_STACK
        | stack contents now is just [syscall return address] [pt_regs] [frame]
        | return pt_regs.d0
        movel   %sp@(PT_OFF_D0+4),%d0
        rts

ENTRY(buserr)
        SAVE_ALL_INT
        GET_CURRENT(%d0)
        movel   %sp,%sp@-               | stack frame pointer argument
        jbsr    buserr_c
        addql   #4,%sp
        jra     ret_from_exception

ENTRY(trap)
        SAVE_ALL_INT
        GET_CURRENT(%d0)
        movel   %sp,%sp@-               | stack frame pointer argument
        jbsr    trap_c
        addql   #4,%sp
        jra     ret_from_exception

        | After a fork we jump here directly from resume,
        | so that %d1 contains the previous task
        | schedule_tail now used regardless of CONFIG_SMP
ENTRY(ret_from_fork)
        movel   %d1,%sp@-
        jsr     schedule_tail
        addql   #4,%sp
        jra     ret_from_exception

ENTRY(ret_from_kernel_thread)
        | a3 contains the kernel thread payload, d7 - its argument
        movel   %d1,%sp@-
        jsr     schedule_tail
        movel   %d7,(%sp)
        jsr     %a3@
        addql   #4,%sp
        jra     ret_from_exception

#if defined(CONFIG_COLDFIRE) || !defined(CONFIG_MMU)

#ifdef TRAP_DBG_INTERRUPT

.globl dbginterrupt
ENTRY(dbginterrupt)
        SAVE_ALL_INT
        GET_CURRENT(%d0)
        movel   %sp,%sp@-               /* stack frame pointer argument */
        jsr     dbginterrupt_c
        addql   #4,%sp
        jra     ret_from_exception
#endif

ENTRY(reschedule)
        /* save top of frame */
        pea     %sp@
        jbsr    set_esp0
        addql   #4,%sp
        pea     ret_from_exception
        jmp     schedule

ENTRY(ret_from_user_signal)
        moveq #__NR_sigreturn,%d0
        trap #0

ENTRY(ret_from_user_rt_signal)
        movel #__NR_rt_sigreturn,%d0
        trap #0

#else

do_trace_entry:
        movel   #-ENOSYS,%sp@(PT_OFF_D0)| needed for strace
        subql   #4,%sp
        SAVE_SWITCH_STACK
        jbsr    syscall_trace_enter
        RESTORE_SWITCH_STACK
        addql   #4,%sp
        addql   #1,%d0                  | optimization for cmpil #-1,%d0
        jeq     ret_from_syscall
        movel   %sp@(PT_OFF_ORIG_D0),%d0
        cmpl    #NR_syscalls,%d0
        jcs     syscall
        jra     ret_from_syscall
badsys:
        movel   #-ENOSYS,%sp@(PT_OFF_D0)
        jra     ret_from_syscall

do_trace_exit:
        subql   #4,%sp
        SAVE_SWITCH_STACK
        jbsr    syscall_trace_leave
        RESTORE_SWITCH_STACK
        addql   #4,%sp
        jra     .Lret_from_exception

ENTRY(system_call)
        SAVE_ALL_SYS

        GET_CURRENT(%d1)
        movel   %d1,%a1

        | save top of frame
        movel   %sp,%curptr@(TASK_THREAD+THREAD_ESP0)

        | syscall trace?
        tstb    %a1@(TINFO_FLAGS+2)
        jmi     do_trace_entry
        | seccomp filter active?
        btst    #5,%a1@(TINFO_FLAGS+2)
        bnes    do_trace_entry
        cmpl    #NR_syscalls,%d0
        jcc     badsys
syscall:
        jbsr    @(sys_call_table,%d0:l:4)@(0)
        movel   %d0,%sp@(PT_OFF_D0)     | save the return value
ret_from_syscall:
        |oriw   #0x0700,%sr
        movel   %curptr@(TASK_STACK),%a1
        movew   %a1@(TINFO_FLAGS+2),%d0
        jne     syscall_exit_work
1:      RESTORE_ALL

syscall_exit_work:
        btst    #5,%sp@(PT_OFF_SR)      | check if returning to kernel
        bnes    1b                      | if so, skip resched, signals
        lslw    #1,%d0
        jcs     do_trace_exit
        jmi     do_delayed_trace
        lslw    #8,%d0
        jne     do_signal_return
        pea     resume_userspace
        jra     schedule


ENTRY(ret_from_exception)
.Lret_from_exception:
        btst    #5,%sp@(PT_OFF_SR)      | check if returning to kernel
        bnes    1f                      | if so, skip resched, signals
        | only allow interrupts when we are really the last one on the
        | kernel stack, otherwise stack overflow can occur during
        | heavy interrupt load
        andw    #ALLOWINT,%sr

resume_userspace:
        movel   %curptr@(TASK_STACK),%a1
        moveb   %a1@(TINFO_FLAGS+3),%d0
        jne     exit_work
1:      RESTORE_ALL

exit_work:
        | save top of frame
        movel   %sp,%curptr@(TASK_THREAD+THREAD_ESP0)
        lslb    #1,%d0
        jne     do_signal_return
        pea     resume_userspace
        jra     schedule


do_signal_return:
        |andw   #ALLOWINT,%sr
        subql   #4,%sp                  | dummy return address
        SAVE_SWITCH_STACK
        pea     %sp@(SWITCH_STACK_SIZE)
        bsrl    do_notify_resume
        addql   #4,%sp
        RESTORE_SWITCH_STACK
        addql   #4,%sp
        jbra    resume_userspace

do_delayed_trace:
        bclr    #7,%sp@(PT_OFF_SR)      | clear trace bit in SR
        pea     1                       | send SIGTRAP
        movel   %curptr,%sp@-
        pea     LSIGTRAP
        jbsr    send_sig
        addql   #8,%sp
        addql   #4,%sp
        jbra    resume_userspace


/* This is the main interrupt handler for autovector interrupts */

ENTRY(auto_inthandler)
        SAVE_ALL_INT
        GET_CURRENT(%d0)
                                        |  put exception # in d0
        bfextu  %sp@(PT_OFF_FORMATVEC){#4,#10},%d0
        subw    #VEC_SPUR,%d0

        movel   %sp,%sp@-
        movel   %d0,%sp@-               |  put vector # on stack
auto_irqhandler_fixup = . + 2
        jsr     do_IRQ                  |  process the IRQ
        addql   #8,%sp                  |  pop parameters off stack
        jra     ret_from_exception

/* Handler for user defined interrupt vectors */

ENTRY(user_inthandler)
        SAVE_ALL_INT
        GET_CURRENT(%d0)
                                        |  put exception # in d0
        bfextu  %sp@(PT_OFF_FORMATVEC){#4,#10},%d0
user_irqvec_fixup = . + 2
        subw    #VEC_USER,%d0

        movel   %sp,%sp@-
        movel   %d0,%sp@-               |  put vector # on stack
        jsr     do_IRQ                  |  process the IRQ
        addql   #8,%sp                  |  pop parameters off stack
        jra     ret_from_exception

/* Handler for uninitialized and spurious interrupts */

ENTRY(bad_inthandler)
        SAVE_ALL_INT
        GET_CURRENT(%d0)

        movel   %sp,%sp@-
        jsr     handle_badint
        addql   #4,%sp
        jra     ret_from_exception

resume:
        /*
         * Beware - when entering resume, prev (the current task) is
         * in a0, next (the new task) is in a1,so don't change these
         * registers until their contents are no longer needed.
         */

        /* save sr */
        movew   %sr,%a0@(TASK_THREAD+THREAD_SR)

        /* save fs (sfc,%dfc) (may be pointing to kernel memory) */
        movec   %sfc,%d0
        movew   %d0,%a0@(TASK_THREAD+THREAD_FC)

        /* save usp */
        /* it is better to use a movel here instead of a movew 8*) */
        movec   %usp,%d0
        movel   %d0,%a0@(TASK_THREAD+THREAD_USP)

        /* save non-scratch registers on stack */
        SAVE_SWITCH_STACK

        /* save current kernel stack pointer */
        movel   %sp,%a0@(TASK_THREAD+THREAD_KSP)

        /* save floating point context */
#ifndef CONFIG_M68KFPU_EMU_ONLY
#ifdef CONFIG_M68KFPU_EMU
        tstl    m68k_fputype
        jeq     3f
#endif
        fsave   %a0@(TASK_THREAD+THREAD_FPSTATE)

#if defined(CONFIG_M68060)
#if !defined(CPU_M68060_ONLY)
        btst    #3,m68k_cputype+3
        beqs    1f
#endif
        /* The 060 FPU keeps status in bits 15-8 of the first longword */
        tstb    %a0@(TASK_THREAD+THREAD_FPSTATE+2)
        jeq     3f
#if !defined(CPU_M68060_ONLY)
        jra     2f
#endif
#endif /* CONFIG_M68060 */
#if !defined(CPU_M68060_ONLY)
1:      tstb    %a0@(TASK_THREAD+THREAD_FPSTATE)
        jeq     3f
#endif
2:      fmovemx %fp0-%fp7,%a0@(TASK_THREAD+THREAD_FPREG)
        fmoveml %fpcr/%fpsr/%fpiar,%a0@(TASK_THREAD+THREAD_FPCNTL)
3:
#endif  /* CONFIG_M68KFPU_EMU_ONLY */
        /* Return previous task in %d1 */
        movel   %curptr,%d1

        /* switch to new task (a1 contains new task) */
        movel   %a1,%curptr

        /* restore floating point context */
#ifndef CONFIG_M68KFPU_EMU_ONLY
#ifdef CONFIG_M68KFPU_EMU
        tstl    m68k_fputype
        jeq     4f
#endif
#if defined(CONFIG_M68060)
#if !defined(CPU_M68060_ONLY)
        btst    #3,m68k_cputype+3
        beqs    1f
#endif
        /* The 060 FPU keeps status in bits 15-8 of the first longword */
        tstb    %a1@(TASK_THREAD+THREAD_FPSTATE+2)
        jeq     3f
#if !defined(CPU_M68060_ONLY)
        jra     2f
#endif
#endif /* CONFIG_M68060 */
#if !defined(CPU_M68060_ONLY)
1:      tstb    %a1@(TASK_THREAD+THREAD_FPSTATE)
        jeq     3f
#endif
2:      fmovemx %a1@(TASK_THREAD+THREAD_FPREG),%fp0-%fp7
        fmoveml %a1@(TASK_THREAD+THREAD_FPCNTL),%fpcr/%fpsr/%fpiar
3:      frestore %a1@(TASK_THREAD+THREAD_FPSTATE)
4:
#endif  /* CONFIG_M68KFPU_EMU_ONLY */

        /* restore the kernel stack pointer */
        movel   %a1@(TASK_THREAD+THREAD_KSP),%sp

        /* restore non-scratch registers */
        RESTORE_SWITCH_STACK

        /* restore user stack pointer */
        movel   %a1@(TASK_THREAD+THREAD_USP),%a0
        movel   %a0,%usp

        /* restore fs (sfc,%dfc) */
        movew   %a1@(TASK_THREAD+THREAD_FC),%a0
        movec   %a0,%sfc
        movec   %a0,%dfc

        /* restore status register */
        movew   %a1@(TASK_THREAD+THREAD_SR),%d0
        oriw    #0x0700,%d0
        movew   %d0,%sr

        rts

#endif /* CONFIG_MMU && !CONFIG_COLDFIRE */