401 lines
8.5 KiB
ArmAsm
401 lines
8.5 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0
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*
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* Copyright (C) 1999, 2000, 2002 Niibe Yutaka
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* Copyright (C) 2003 - 2008 Paul Mundt
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*/
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! NOTE:
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! GNU as (as of 2.9.1) changes bf/s into bt/s and bra, when the address
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! to be jumped is too far, but it causes illegal slot exception.
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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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* NOTE: This code uses a convention that instructions in the delay slot
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* of a transfer-control instruction are indented by an extra space, thus:
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*
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* jmp @k0 ! control-transfer instruction
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* ldc k1, ssr ! delay slot
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*
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* Stack layout in 'ret_from_syscall':
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* ptrace needs to have all regs on the stack.
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* if the order here is changed, it needs to be
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* updated in ptrace.c and ptrace.h
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*
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* r0
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* ...
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* r15 = stack pointer
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* spc
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* pr
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* ssr
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* gbr
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* mach
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* macl
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* syscall #
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*
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*/
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#include <asm/dwarf.h>
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#if defined(CONFIG_PREEMPTION)
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# define preempt_stop() cli ; TRACE_IRQS_OFF
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#else
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# define preempt_stop()
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# define resume_kernel __restore_all
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#endif
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.align 2
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ENTRY(exception_error)
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!
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TRACE_IRQS_ON
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sti
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mov.l 1f, r0
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jmp @r0
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nop
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.align 2
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1: .long do_exception_error
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.align 2
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ret_from_exception:
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CFI_STARTPROC simple
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CFI_DEF_CFA r14, 0
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CFI_REL_OFFSET 17, 64
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CFI_REL_OFFSET 15, 60
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CFI_REL_OFFSET 14, 56
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CFI_REL_OFFSET 13, 52
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CFI_REL_OFFSET 12, 48
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CFI_REL_OFFSET 11, 44
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CFI_REL_OFFSET 10, 40
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CFI_REL_OFFSET 9, 36
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CFI_REL_OFFSET 8, 32
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preempt_stop()
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ENTRY(ret_from_irq)
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!
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mov #OFF_SR, r0
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mov.l @(r0,r15), r0 ! get status register
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shll r0
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shll r0 ! kernel space?
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get_current_thread_info r8, r0
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bt resume_kernel ! Yes, it's from kernel, go back soon
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#ifdef CONFIG_PREEMPTION
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bra resume_userspace
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nop
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ENTRY(resume_kernel)
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cli
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TRACE_IRQS_OFF
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mov.l @(TI_PRE_COUNT,r8), r0 ! current_thread_info->preempt_count
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tst r0, r0
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bf noresched
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need_resched:
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mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
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tst #_TIF_NEED_RESCHED, r0 ! need_resched set?
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bt noresched
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mov #OFF_SR, r0
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mov.l @(r0,r15), r0 ! get status register
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shlr r0
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and #(0xf0>>1), r0 ! interrupts off (exception path)?
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cmp/eq #(0xf0>>1), r0
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bt noresched
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mov.l 1f, r0
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jsr @r0 ! call preempt_schedule_irq
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nop
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bra need_resched
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nop
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noresched:
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bra __restore_all
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nop
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.align 2
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1: .long preempt_schedule_irq
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#endif
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ENTRY(resume_userspace)
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! r8: current_thread_info
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cli
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TRACE_IRQS_OFF
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mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
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tst #(_TIF_WORK_MASK & 0xff), r0
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bt/s __restore_all
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tst #_TIF_NEED_RESCHED, r0
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.align 2
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work_pending:
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! r0: current_thread_info->flags
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! r8: current_thread_info
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! t: result of "tst #_TIF_NEED_RESCHED, r0"
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bf/s work_resched
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tst #(_TIF_SIGPENDING | _TIF_NOTIFY_RESUME), r0
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work_notifysig:
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bt/s __restore_all
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mov r15, r4
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mov r12, r5 ! set arg1(save_r0)
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mov r0, r6
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sti
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mov.l 2f, r1
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mov.l 3f, r0
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jmp @r1
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lds r0, pr
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work_resched:
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mov.l 1f, r1
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jsr @r1 ! schedule
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nop
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cli
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TRACE_IRQS_OFF
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!
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mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
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tst #(_TIF_WORK_MASK & 0xff), r0
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bt __restore_all
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bra work_pending
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tst #_TIF_NEED_RESCHED, r0
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.align 2
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1: .long schedule
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2: .long do_notify_resume
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3: .long resume_userspace
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.align 2
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syscall_exit_work:
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! r0: current_thread_info->flags
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! r8: current_thread_info
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tst #(_TIF_WORK_SYSCALL_MASK & 0xff), r0
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bt/s work_pending
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tst #_TIF_NEED_RESCHED, r0
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TRACE_IRQS_ON
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sti
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mov r15, r4
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mov.l 8f, r0 ! do_syscall_trace_leave
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jsr @r0
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nop
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bra resume_userspace
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nop
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__restore_all:
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mov #OFF_SR, r0
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mov.l @(r0,r15), r0 ! get status register
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shlr2 r0
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and #0x3c, r0
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cmp/eq #0x3c, r0
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bt 1f
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TRACE_IRQS_ON
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bra 2f
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nop
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1:
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TRACE_IRQS_OFF
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2:
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mov.l 3f, r0
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jmp @r0
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nop
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.align 2
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3: .long restore_all
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.align 2
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syscall_badsys: ! Bad syscall number
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get_current_thread_info r8, r0
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mov #-ENOSYS, r0
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bra resume_userspace
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mov.l r0, @(OFF_R0,r15) ! Return value
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/*
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* The main debug trap handler.
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*
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* r8=TRA (not the trap number!)
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*
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* Note: This assumes that the trapa value is left in its original
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* form (without the shlr2 shift) so the calculation for the jump
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* call table offset remains a simple in place mask.
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*/
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debug_trap:
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mov r8, r0
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and #(0xf << 2), r0
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mov.l 1f, r8
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add r0, r8
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mov.l @r8, r8
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jsr @r8
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nop
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bra ret_from_exception
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nop
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CFI_ENDPROC
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.align 2
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1: .long debug_trap_table
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/*
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* Syscall interface:
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*
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* Syscall #: R3
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* Arguments #0 to #3: R4--R7
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* Arguments #4 to #6: R0, R1, R2
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* TRA: See following table.
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*
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* (TRA>>2) Purpose
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* -------- -------
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* 0x00-0x0f original SH-3/4 syscall ABI (not in general use).
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* 0x10-0x1f general SH-3/4 syscall ABI.
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* 0x1f unified SH-2/3/4 syscall ABI (preferred).
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* 0x20-0x2f original SH-2 syscall ABI.
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* 0x30-0x3f debug traps used by the kernel.
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* 0x40-0xff Not supported by all parts, so left unhandled.
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*
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* For making system calls, any trap number in the range for the
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* given cpu model may be used, but the unified trap number 0x1f is
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* preferred for compatibility with all models.
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*
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* The low bits of the trap number were once documented as matching
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* the number of arguments, but they were never actually used as such
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* by the kernel. SH-2 originally used its own separate trap range
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* because several hardware exceptions fell in the range used for the
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* SH-3/4 syscall ABI.
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*
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* This code also handles delegating other traps to the BIOS/gdb stub.
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*
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* Note: When we're first called, the TRA value must be shifted
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* right 2 bits in order to get the value that was used as the "trapa"
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* argument.
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*/
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.align 2
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.globl ret_from_fork
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ret_from_fork:
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mov.l 1f, r8
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jsr @r8
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mov r0, r4
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bra syscall_exit
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nop
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.align 2
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.globl ret_from_kernel_thread
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ret_from_kernel_thread:
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mov.l 1f, r8
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jsr @r8
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mov r0, r4
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mov.l @(OFF_R5,r15), r5 ! fn
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jsr @r5
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mov.l @(OFF_R4,r15), r4 ! arg
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bra syscall_exit
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nop
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.align 2
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1: .long schedule_tail
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/*
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* The poorly named main trapa decode and dispatch routine, for
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* system calls and debug traps through their respective jump tables.
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*/
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ENTRY(system_call)
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setup_frame_reg
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#if !defined(CONFIG_CPU_SH2)
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mov.l 1f, r9
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mov.l @r9, r8 ! Read from TRA (Trap Address) Register
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#endif
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mov #OFF_TRA, r10
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add r15, r10
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mov.l r8, @r10 ! set TRA value to tra
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/*
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* Check the trap type
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*/
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mov #((0x20 << 2) - 1), r9
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cmp/hi r9, r8
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bt/s debug_trap ! it's a debug trap..
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nop
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TRACE_IRQS_ON
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sti
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!
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get_current_thread_info r8, r10
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mov.l @(TI_FLAGS,r8), r8
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mov #(_TIF_WORK_SYSCALL_MASK & 0xff), r10
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mov #(_TIF_WORK_SYSCALL_MASK >> 8), r9
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tst r10, r8
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shll8 r9
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bf syscall_trace_entry
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tst r9, r8
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bf syscall_trace_entry
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!
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mov.l 6f, r8 ! Number of syscalls
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cmp/hs r8, r3
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bt syscall_badsys
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!
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syscall_call:
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shll2 r3 ! x4
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mov.l 3f, r8 ! Load the address of sys_call_table
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add r8, r3
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mov.l @r3, r8
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mov.l @(OFF_R2,r15), r2
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mov.l @(OFF_R1,r15), r1
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mov.l @(OFF_R0,r15), r0
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mov.l r2, @-r15
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mov.l r1, @-r15
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mov.l r0, @-r15
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jsr @r8 ! jump to specific syscall handler
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nop
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add #12, r15
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mov.l @(OFF_R0,r15), r12 ! save r0
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mov.l r0, @(OFF_R0,r15) ! save the return value
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!
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syscall_exit:
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cli
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TRACE_IRQS_OFF
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!
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get_current_thread_info r8, r0
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mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
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tst #(_TIF_ALLWORK_MASK & 0xff), r0
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mov #(_TIF_ALLWORK_MASK >> 8), r1
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bf syscall_exit_work
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shlr8 r0
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tst r0, r1
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bf syscall_exit_work
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bra __restore_all
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nop
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.align 2
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syscall_trace_entry:
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! Yes it is traced.
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mov r15, r4
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mov.l 7f, r11 ! Call do_syscall_trace_enter which notifies
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jsr @r11 ! superior (will chomp R[0-7])
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nop
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cmp/eq #-1, r0
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bt syscall_exit
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! Reload R0-R4 from kernel stack, where the
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! parent may have modified them using
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! ptrace(POKEUSR). (Note that R0-R2 are
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! reloaded from the kernel stack by syscall_call
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! below, so don't need to be reloaded here.)
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! This allows the parent to rewrite system calls
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! and args on the fly.
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mov.l @(OFF_R4,r15), r4 ! arg0
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mov.l @(OFF_R5,r15), r5
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mov.l @(OFF_R6,r15), r6
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mov.l @(OFF_R7,r15), r7 ! arg3
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mov.l @(OFF_R3,r15), r3 ! syscall_nr
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!
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mov.l 6f, r10 ! Number of syscalls
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cmp/hs r10, r3
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bf syscall_call
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mov #-ENOSYS, r0
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bra syscall_exit
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mov.l r0, @(OFF_R0,r15) ! Return value
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.align 2
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#if !defined(CONFIG_CPU_SH2)
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1: .long TRA
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#endif
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6: .long NR_syscalls
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3: .long sys_call_table
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7: .long do_syscall_trace_enter
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8: .long do_syscall_trace_leave
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