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+/*
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+ * File : start_gcc.S
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+ * This file is part of RT-Thread RTOS
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+ * COPYRIGHT (C) 2013-2014, RT-Thread Development Team
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+ *
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+ * This program is free software; you can redistribute it and/or modify
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+ * it under the terms of the GNU General Public License as published by
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+ * the Free Software Foundation; either version 2 of the License, or
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+ * (at your option) any later version.
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+ *
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+ * This program is distributed in the hope that it will be useful,
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+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ * GNU General Public License for more details.
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+ *
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+ * You should have received a copy of the GNU General Public License along
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+ * with this program; if not, write to the Free Software Foundation, Inc.,
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+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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+ *
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+ * Change Logs:
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+ * Date Author Notes
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+ * 2013-07-05 Bernard the first version
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+ */
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+
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+.equ Mode_USR, 0x10
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+.equ Mode_FIQ, 0x11
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+.equ Mode_IRQ, 0x12
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+.equ Mode_SVC, 0x13
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+.equ Mode_ABT, 0x17
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+.equ Mode_UND, 0x1B
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+.equ Mode_SYS, 0x1F
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+
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+.equ I_Bit, 0x80 @ when I bit is set, IRQ is disabled
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+.equ F_Bit, 0x40 @ when F bit is set, FIQ is disabled
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+
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+.equ UND_Stack_Size, 0x00000000
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+.equ SVC_Stack_Size, 0x00000100
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+.equ ABT_Stack_Size, 0x00000000
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+.equ RT_FIQ_STACK_PGSZ, 0x00000000
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+.equ RT_IRQ_STACK_PGSZ, 0x00000100
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+.equ USR_Stack_Size, 0x00000100
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+
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+#define ISR_Stack_Size (UND_Stack_Size + SVC_Stack_Size + ABT_Stack_Size + \
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+ RT_FIQ_STACK_PGSZ + RT_IRQ_STACK_PGSZ)
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+
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+.section .data.share.isr
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+/* stack */
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+.globl stack_start
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+.globl stack_top
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+
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+.align 3
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+stack_start:
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+.rept ISR_Stack_Size
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+.byte 0
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+.endr
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+stack_top:
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+
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+.text
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+/* reset entry */
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+.globl _reset
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+_reset:
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+ /* Disable IRQ & FIQ */
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+ cpsid if
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+
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+ /* Check for HYP mode */
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+ mrs r0, cpsr_all
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+ and r0, r0, #0x1F
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+ mov r8, #0x1A
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+ cmp r0, r8
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+ beq overHyped
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+ b continue
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+
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+overHyped: /* Get out of HYP mode */
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+ ldr r1, =continue
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+ msr ELR_hyp, r1
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+ mrs r1, cpsr_all
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+ and r1, r1, #0x1f ;@ CPSR_MODE_MASK
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+ orr r1, r1, #0x13 ;@ CPSR_MODE_SUPERVISOR
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+ msr SPSR_hyp, r1
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+ eret
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+
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+continue:
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+
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+ /* disable smp */
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+ bl arm_smp_disable
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+
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+ /* disable mmu */
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+ bl rt_cpu_mmu_disable
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+ /* set the cpu to SVC32 mode and disable interrupt */
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+ mrs r0, cpsr
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+ bic r0, r0, #0x1f
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+ orr r0, r0, #0x13
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+ msr cpsr_c, r0
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+
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+ /* setup stack */
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+ bl stack_setup
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+
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+ /* clear .bss */
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+ mov r0,#0 /* get a zero */
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+ ldr r1,=__bss_start /* bss start */
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+ ldr r2,=__bss_end /* bss end */
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+
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+bss_loop:
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+ cmp r1,r2 /* check if data to clear */
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+ strlo r0,[r1],#4 /* clear 4 bytes */
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+ blo bss_loop /* loop until done */
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+
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+ /* start RT-Thread Kernel */
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+ ldr pc, _rtthread_startup
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+_rtthread_startup:
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+ .word rtthread_startup
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+
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+stack_setup:
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+ ldr r0, =stack_top
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+
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+ @ Set the startup stack for svc
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+ mov sp, r0
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+ sub r0, r0, #SVC_Stack_Size
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+
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+ @ Enter Undefined Instruction Mode and set its Stack Pointer
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+ msr cpsr_c, #Mode_UND|I_Bit|F_Bit
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+ mov sp, r0
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+ sub r0, r0, #UND_Stack_Size
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+
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+ @ Enter Abort Mode and set its Stack Pointer
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+ msr cpsr_c, #Mode_ABT|I_Bit|F_Bit
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+ mov sp, r0
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+ sub r0, r0, #ABT_Stack_Size
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+
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+ @ Enter FIQ Mode and set its Stack Pointer
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+ msr cpsr_c, #Mode_FIQ|I_Bit|F_Bit
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+ mov sp, r0
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+ sub r0, r0, #RT_FIQ_STACK_PGSZ
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+
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+ @ Enter IRQ Mode and set its Stack Pointer
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+ msr cpsr_c, #Mode_IRQ|I_Bit|F_Bit
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+ mov sp, r0
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+ sub r0, r0, #RT_IRQ_STACK_PGSZ
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+
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+ /* come back to SVC mode */
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+ msr cpsr_c, #Mode_SVC|I_Bit|F_Bit
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+ bx lr
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+
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+.text
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+;@ void arm_smp_enable(void);
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+.globl arm_smp_enable
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+arm_smp_enable:
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+ mrc p15, 0, r0, c1, c0, 1 ;@ set SMP bit in ACTLR
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+ orr r0, r0, #0x40
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+ mcr p15, 0, r0, c1, c0, 1
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+ bx lr
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+
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+.text
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+;@ void arm_smp_disable(void);
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+.globl arm_smp_disable
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+arm_smp_disable:
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+ mrc p15, 0, r0, c1, c0, 1 ;@ clear SMP bit in ACTLR
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+ bic r0, r0, #0x40
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+ mcr p15, 0, r0, c1, c0, 1
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+ bx lr
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+
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+/* exception handlers: undef, swi, padt, dabt, resv, irq, fiq */
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+.section .text.isr, "ax"
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+ .align 5
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+.globl vector_fiq
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+vector_fiq:
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+ stmfd sp!,{r0-r7,lr}
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+ bl rt_hw_trap_fiq
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+ ldmfd sp!,{r0-r7,lr}
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+ subs pc, lr, #4
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+
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+.globl rt_interrupt_enter
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+.globl rt_interrupt_leave
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+.globl rt_thread_switch_interrupt_flag
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+.globl rt_interrupt_from_thread
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+.globl rt_interrupt_to_thread
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+
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+.globl rt_current_thread
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+.globl vmm_thread
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+.globl vmm_virq_check
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+
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+ .align 5
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+.globl vector_irq
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+vector_irq:
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+ stmfd sp!, {r0-r12,lr}
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+
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+ bl rt_interrupt_enter
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+ bl rt_hw_trap_irq
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+ bl rt_interrupt_leave
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+
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+ @ if rt_thread_switch_interrupt_flag set, jump to
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+ @ rt_hw_context_switch_interrupt_do and don't return
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+ ldr r0, =rt_thread_switch_interrupt_flag
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+ ldr r1, [r0]
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+ cmp r1, #1
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+ beq rt_hw_context_switch_interrupt_do
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+
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+ ldmfd sp!, {r0-r12,lr}
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+ subs pc, lr, #4
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+
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+rt_hw_context_switch_interrupt_do:
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+ mov r1, #0 @ clear flag
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+ str r1, [r0]
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+
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+ mov r1, sp @ r1 point to {r0-r3} in stack
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+ add sp, sp, #4*4
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+ ldmfd sp!, {r4-r12,lr}@ reload saved registers
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+ mrs r0, spsr @ get cpsr of interrupt thread
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+ sub r2, lr, #4 @ save old task's pc to r2
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+
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+ @ Switch to SVC mode with no interrupt. If the usr mode guest is
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+ @ interrupted, this will just switch to the stack of kernel space.
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+ @ save the registers in kernel space won't trigger data abort.
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+ msr cpsr_c, #I_Bit|F_Bit|Mode_SVC
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+
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+ stmfd sp!, {r2} @ push old task's pc
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+ stmfd sp!, {r4-r12,lr}@ push old task's lr,r12-r4
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+ ldmfd r1, {r1-r4} @ restore r0-r3 of the interrupt thread
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+ stmfd sp!, {r1-r4} @ push old task's r0-r3
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+ stmfd sp!, {r0} @ push old task's cpsr
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+
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+ ldr r4, =rt_interrupt_from_thread
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+ ldr r5, [r4]
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+ str sp, [r5] @ store sp in preempted tasks's TCB
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+
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+ ldr r6, =rt_interrupt_to_thread
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+ ldr r6, [r6]
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+ ldr sp, [r6] @ get new task's stack pointer
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+
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+ ldmfd sp!, {r4} @ pop new task's cpsr to spsr
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+ msr spsr_cxsf, r4
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+
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+ ldmfd sp!, {r0-r12,lr,pc}^ @ pop new task's r0-r12,lr & pc, copy spsr to cpsr
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+
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+.macro push_svc_reg
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+ sub sp, sp, #17 * 4 @/* Sizeof(struct rt_hw_exp_stack) */
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+ stmia sp, {r0 - r12} @/* Calling r0-r12 */
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+ mov r0, sp
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+ mrs r6, spsr @/* Save CPSR */
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+ str lr, [r0, #15*4] @/* Push PC */
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+ str r6, [r0, #16*4] @/* Push CPSR */
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+ cps #Mode_SVC
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+ str sp, [r0, #13*4] @/* Save calling SP */
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+ str lr, [r0, #14*4] @/* Save calling PC */
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+.endm
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+
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+ .align 5
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+ .globl vector_swi
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+vector_swi:
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+ push_svc_reg
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+ bl rt_hw_trap_swi
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+ b .
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+
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+ .align 5
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+ .globl vector_undef
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+vector_undef:
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+ push_svc_reg
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+ bl rt_hw_trap_undef
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+ b .
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+
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+ .align 5
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+ .globl vector_pabt
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+vector_pabt:
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+ push_svc_reg
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+ bl rt_hw_trap_pabt
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+ b .
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+
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+ .align 5
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+ .globl vector_dabt
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+vector_dabt:
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+ push_svc_reg
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+ bl rt_hw_trap_dabt
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+ b .
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+
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+ .align 5
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+ .globl vector_resv
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+vector_resv:
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+ push_svc_reg
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+ bl rt_hw_trap_resv
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+ b .
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