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https://github.com/torvalds/linux
synced 2024-11-05 18:23:50 +00:00
09f90f6685
The low level interrupt entry code of m68k contains the following:
add_preempt_count(HARDIRQ_OFFSET);
do_IRQ();
irq_enter();
add_preempt_count(HARDIRQ_OFFSET);
handle_interrupt();
irq_exit();
sub_preempt_count(HARDIRQ_OFFSET);
if (in_interrupt())
return; <---- On m68k always taken!
if (local_softirq_pending())
do_softirq();
sub_preempt_count(HARDIRQ_OFFSET);
if (in_hardirq())
return;
if (status_on_stack_has_interrupt_priority_mask > 0)
return;
if (local_softirq_pending())
do_softirq();
ret_from_exception:
if (interrupted_context_is_kernel)
return:
....
I tried to find a proper explanation for this, but the changelog is
sparse and there are no mails explaining it further. But obviously
this relates to the interrupt priority levels of the m68k and tries to
be extra clever with nested interrupts. Though this cleverness just
adds code bloat to the interrupt hotpath.
For the common case of non nested interrupts the code runs through two
extra conditionals to the only important one, which checks whether the
return is to kernel or user space.
For the nested case the checks for in_hardirq() and the priority mask
value on stack catch only the case where the nested interrupt happens
inside the hard irq context of the first interrupt. If the nested
interrupt happens while the first interrupt handles soft interrupts,
then these extra checks buy nothing. The nested interrupt will fall
through to the final kernel/user space return check at
ret_from_exception.
Changing the code flow in the following way:
do_IRQ();
irq_enter();
add_preempt_count(HARDIRQ_OFFSET);
handle_interrupt();
irq_exit();
sub_preempt_count(HARDIRQ_OFFSET);
if (in_interrupt())
return;
if (local_softirq_pending())
do_softirq();
ret_from_exception:
if (interrupted_context_is_kernel)
return:
makes the region protected by the hardirq count slightly smaller and
the softirq handling is invoked with a minimal deeper stack. But
otherwise it's completely functional equivalent and saves 104 bytes of
text in arch/m68k/kernel/entry.o.
This modification allows us further to get rid of the limitations
which m68k puts on the preempt_count layout, so we can make the
preempt count bits completely generic.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Schmitz <schmitz@biophys.uni-duesseldorf.de>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Linux/m68k <linux-m68k@vger.kernel.org>
Cc: Andreas Schwab <schwab@linux-m68k.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1311112052360.30673@ionos.tec.linutronix.de
423 lines
9 KiB
ArmAsm
423 lines
9 KiB
ArmAsm
/* -*- mode: asm -*-
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*
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* linux/arch/m68k/kernel/entry.S
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file README.legal in the main directory of this archive
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* for more details.
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*
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* Linux/m68k support by Hamish Macdonald
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*
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* 68060 fixes by Jesper Skov
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*
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*/
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/*
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* entry.S contains the system-call and fault low-level handling routines.
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* This also contains the timer-interrupt handler, as well as all interrupts
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* and faults that can result in a task-switch.
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*
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* NOTE: This code handles signal-recognition, which happens every time
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* after a timer-interrupt and after each system call.
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*
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*/
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/*
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* 12/03/96 Jes: Currently we only support m68k single-cpu systems, so
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* all pointers that used to be 'current' are now entry
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* number 0 in the 'current_set' list.
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*
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* 6/05/00 RZ: addedd writeback completion after return from sighandler
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* for 68040
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*/
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#include <linux/linkage.h>
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#include <asm/errno.h>
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#include <asm/setup.h>
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#include <asm/segment.h>
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#include <asm/traps.h>
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#include <asm/unistd.h>
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#include <asm/asm-offsets.h>
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#include <asm/entry.h>
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.globl system_call, buserr, trap, resume
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.globl sys_call_table
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.globl __sys_fork, __sys_clone, __sys_vfork
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.globl bad_interrupt
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.globl auto_irqhandler_fixup
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.globl user_irqvec_fixup
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.text
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ENTRY(__sys_fork)
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SAVE_SWITCH_STACK
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jbsr sys_fork
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lea %sp@(24),%sp
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rts
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ENTRY(__sys_clone)
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SAVE_SWITCH_STACK
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pea %sp@(SWITCH_STACK_SIZE)
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jbsr m68k_clone
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lea %sp@(28),%sp
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rts
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ENTRY(__sys_vfork)
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SAVE_SWITCH_STACK
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jbsr sys_vfork
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lea %sp@(24),%sp
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rts
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ENTRY(sys_sigreturn)
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SAVE_SWITCH_STACK
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jbsr do_sigreturn
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RESTORE_SWITCH_STACK
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rts
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ENTRY(sys_rt_sigreturn)
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SAVE_SWITCH_STACK
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jbsr do_rt_sigreturn
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RESTORE_SWITCH_STACK
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rts
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ENTRY(buserr)
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SAVE_ALL_INT
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GET_CURRENT(%d0)
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movel %sp,%sp@- | stack frame pointer argument
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jbsr buserr_c
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addql #4,%sp
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jra ret_from_exception
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ENTRY(trap)
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SAVE_ALL_INT
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GET_CURRENT(%d0)
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movel %sp,%sp@- | stack frame pointer argument
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jbsr trap_c
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addql #4,%sp
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jra ret_from_exception
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| After a fork we jump here directly from resume,
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| so that %d1 contains the previous task
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| schedule_tail now used regardless of CONFIG_SMP
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ENTRY(ret_from_fork)
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movel %d1,%sp@-
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jsr schedule_tail
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addql #4,%sp
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jra ret_from_exception
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ENTRY(ret_from_kernel_thread)
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| a3 contains the kernel thread payload, d7 - its argument
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movel %d1,%sp@-
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jsr schedule_tail
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movel %d7,(%sp)
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jsr %a3@
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addql #4,%sp
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jra ret_from_exception
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#if defined(CONFIG_COLDFIRE) || !defined(CONFIG_MMU)
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#ifdef TRAP_DBG_INTERRUPT
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.globl dbginterrupt
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ENTRY(dbginterrupt)
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SAVE_ALL_INT
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GET_CURRENT(%d0)
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movel %sp,%sp@- /* stack frame pointer argument */
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jsr dbginterrupt_c
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addql #4,%sp
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jra ret_from_exception
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#endif
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ENTRY(reschedule)
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/* save top of frame */
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pea %sp@
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jbsr set_esp0
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addql #4,%sp
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pea ret_from_exception
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jmp schedule
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ENTRY(ret_from_user_signal)
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moveq #__NR_sigreturn,%d0
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trap #0
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ENTRY(ret_from_user_rt_signal)
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movel #__NR_rt_sigreturn,%d0
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trap #0
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#else
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do_trace_entry:
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movel #-ENOSYS,%sp@(PT_OFF_D0)| needed for strace
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subql #4,%sp
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SAVE_SWITCH_STACK
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jbsr syscall_trace
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RESTORE_SWITCH_STACK
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addql #4,%sp
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movel %sp@(PT_OFF_ORIG_D0),%d0
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cmpl #NR_syscalls,%d0
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jcs syscall
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badsys:
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movel #-ENOSYS,%sp@(PT_OFF_D0)
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jra ret_from_syscall
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do_trace_exit:
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subql #4,%sp
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SAVE_SWITCH_STACK
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jbsr syscall_trace
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RESTORE_SWITCH_STACK
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addql #4,%sp
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jra .Lret_from_exception
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ENTRY(ret_from_signal)
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movel %curptr@(TASK_STACK),%a1
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tstb %a1@(TINFO_FLAGS+2)
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jge 1f
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jbsr syscall_trace
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1: RESTORE_SWITCH_STACK
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addql #4,%sp
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/* on 68040 complete pending writebacks if any */
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#ifdef CONFIG_M68040
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bfextu %sp@(PT_OFF_FORMATVEC){#0,#4},%d0
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subql #7,%d0 | bus error frame ?
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jbne 1f
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movel %sp,%sp@-
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jbsr berr_040cleanup
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addql #4,%sp
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1:
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#endif
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jra .Lret_from_exception
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ENTRY(system_call)
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SAVE_ALL_SYS
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GET_CURRENT(%d1)
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movel %d1,%a1
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| save top of frame
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movel %sp,%curptr@(TASK_THREAD+THREAD_ESP0)
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| syscall trace?
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tstb %a1@(TINFO_FLAGS+2)
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jmi do_trace_entry
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cmpl #NR_syscalls,%d0
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jcc badsys
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syscall:
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jbsr @(sys_call_table,%d0:l:4)@(0)
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movel %d0,%sp@(PT_OFF_D0) | save the return value
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ret_from_syscall:
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|oriw #0x0700,%sr
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movel %curptr@(TASK_STACK),%a1
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movew %a1@(TINFO_FLAGS+2),%d0
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jne syscall_exit_work
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1: RESTORE_ALL
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syscall_exit_work:
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btst #5,%sp@(PT_OFF_SR) | check if returning to kernel
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bnes 1b | if so, skip resched, signals
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lslw #1,%d0
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jcs do_trace_exit
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jmi do_delayed_trace
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lslw #8,%d0
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jne do_signal_return
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pea resume_userspace
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jra schedule
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ENTRY(ret_from_exception)
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.Lret_from_exception:
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btst #5,%sp@(PT_OFF_SR) | check if returning to kernel
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bnes 1f | if so, skip resched, signals
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| only allow interrupts when we are really the last one on the
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| kernel stack, otherwise stack overflow can occur during
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| heavy interrupt load
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andw #ALLOWINT,%sr
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resume_userspace:
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movel %curptr@(TASK_STACK),%a1
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moveb %a1@(TINFO_FLAGS+3),%d0
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jne exit_work
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1: RESTORE_ALL
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exit_work:
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| save top of frame
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movel %sp,%curptr@(TASK_THREAD+THREAD_ESP0)
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lslb #1,%d0
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jne do_signal_return
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pea resume_userspace
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jra schedule
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do_signal_return:
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|andw #ALLOWINT,%sr
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subql #4,%sp | dummy return address
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SAVE_SWITCH_STACK
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pea %sp@(SWITCH_STACK_SIZE)
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bsrl do_notify_resume
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addql #4,%sp
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RESTORE_SWITCH_STACK
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addql #4,%sp
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jbra resume_userspace
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do_delayed_trace:
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bclr #7,%sp@(PT_OFF_SR) | clear trace bit in SR
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pea 1 | send SIGTRAP
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movel %curptr,%sp@-
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pea LSIGTRAP
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jbsr send_sig
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addql #8,%sp
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addql #4,%sp
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jbra resume_userspace
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/* This is the main interrupt handler for autovector interrupts */
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ENTRY(auto_inthandler)
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SAVE_ALL_INT
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GET_CURRENT(%d0)
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| put exception # in d0
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bfextu %sp@(PT_OFF_FORMATVEC){#4,#10},%d0
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subw #VEC_SPUR,%d0
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movel %sp,%sp@-
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movel %d0,%sp@- | put vector # on stack
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auto_irqhandler_fixup = . + 2
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jsr do_IRQ | process the IRQ
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addql #8,%sp | pop parameters off stack
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jra ret_from_exception
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/* Handler for user defined interrupt vectors */
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ENTRY(user_inthandler)
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SAVE_ALL_INT
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GET_CURRENT(%d0)
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| put exception # in d0
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bfextu %sp@(PT_OFF_FORMATVEC){#4,#10},%d0
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user_irqvec_fixup = . + 2
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subw #VEC_USER,%d0
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movel %sp,%sp@-
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movel %d0,%sp@- | put vector # on stack
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jsr do_IRQ | process the IRQ
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addql #8,%sp | pop parameters off stack
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jra ret_from_exception
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/* Handler for uninitialized and spurious interrupts */
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ENTRY(bad_inthandler)
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SAVE_ALL_INT
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GET_CURRENT(%d0)
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movel %sp,%sp@-
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jsr handle_badint
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addql #4,%sp
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jra ret_from_exception
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resume:
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/*
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* Beware - when entering resume, prev (the current task) is
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* in a0, next (the new task) is in a1,so don't change these
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* registers until their contents are no longer needed.
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*/
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/* save sr */
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movew %sr,%a0@(TASK_THREAD+THREAD_SR)
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/* save fs (sfc,%dfc) (may be pointing to kernel memory) */
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movec %sfc,%d0
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movew %d0,%a0@(TASK_THREAD+THREAD_FS)
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/* save usp */
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/* it is better to use a movel here instead of a movew 8*) */
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movec %usp,%d0
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movel %d0,%a0@(TASK_THREAD+THREAD_USP)
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/* save non-scratch registers on stack */
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SAVE_SWITCH_STACK
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/* save current kernel stack pointer */
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movel %sp,%a0@(TASK_THREAD+THREAD_KSP)
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/* save floating point context */
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#ifndef CONFIG_M68KFPU_EMU_ONLY
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#ifdef CONFIG_M68KFPU_EMU
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tstl m68k_fputype
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jeq 3f
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#endif
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fsave %a0@(TASK_THREAD+THREAD_FPSTATE)
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#if defined(CONFIG_M68060)
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#if !defined(CPU_M68060_ONLY)
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btst #3,m68k_cputype+3
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beqs 1f
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#endif
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/* The 060 FPU keeps status in bits 15-8 of the first longword */
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tstb %a0@(TASK_THREAD+THREAD_FPSTATE+2)
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jeq 3f
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#if !defined(CPU_M68060_ONLY)
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jra 2f
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#endif
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#endif /* CONFIG_M68060 */
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#if !defined(CPU_M68060_ONLY)
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1: tstb %a0@(TASK_THREAD+THREAD_FPSTATE)
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jeq 3f
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#endif
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2: fmovemx %fp0-%fp7,%a0@(TASK_THREAD+THREAD_FPREG)
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fmoveml %fpcr/%fpsr/%fpiar,%a0@(TASK_THREAD+THREAD_FPCNTL)
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3:
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#endif /* CONFIG_M68KFPU_EMU_ONLY */
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/* Return previous task in %d1 */
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movel %curptr,%d1
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/* switch to new task (a1 contains new task) */
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movel %a1,%curptr
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/* restore floating point context */
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#ifndef CONFIG_M68KFPU_EMU_ONLY
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#ifdef CONFIG_M68KFPU_EMU
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tstl m68k_fputype
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jeq 4f
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#endif
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#if defined(CONFIG_M68060)
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#if !defined(CPU_M68060_ONLY)
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btst #3,m68k_cputype+3
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beqs 1f
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#endif
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/* The 060 FPU keeps status in bits 15-8 of the first longword */
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tstb %a1@(TASK_THREAD+THREAD_FPSTATE+2)
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jeq 3f
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#if !defined(CPU_M68060_ONLY)
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jra 2f
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#endif
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#endif /* CONFIG_M68060 */
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#if !defined(CPU_M68060_ONLY)
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1: tstb %a1@(TASK_THREAD+THREAD_FPSTATE)
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jeq 3f
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#endif
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2: fmovemx %a1@(TASK_THREAD+THREAD_FPREG),%fp0-%fp7
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fmoveml %a1@(TASK_THREAD+THREAD_FPCNTL),%fpcr/%fpsr/%fpiar
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3: frestore %a1@(TASK_THREAD+THREAD_FPSTATE)
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4:
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#endif /* CONFIG_M68KFPU_EMU_ONLY */
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/* restore the kernel stack pointer */
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movel %a1@(TASK_THREAD+THREAD_KSP),%sp
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/* restore non-scratch registers */
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RESTORE_SWITCH_STACK
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/* restore user stack pointer */
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movel %a1@(TASK_THREAD+THREAD_USP),%a0
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movel %a0,%usp
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/* restore fs (sfc,%dfc) */
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movew %a1@(TASK_THREAD+THREAD_FS),%a0
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movec %a0,%sfc
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movec %a0,%dfc
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/* restore status register */
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movew %a1@(TASK_THREAD+THREAD_SR),%sr
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rts
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#endif /* CONFIG_MMU && !CONFIG_COLDFIRE */
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