/* * File : start_gcc.S * This file is part of RT-Thread RTOS * COPYRIGHT (C) 2013-2014, RT-Thread Development Team * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License along * with this program; if not, write to the Free Software Foundation, Inc., * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. * * Change Logs: * Date Author Notes * 2013-07-05 Bernard the first version */ .equ Mode_USR, 0x10 .equ Mode_FIQ, 0x11 .equ Mode_IRQ, 0x12 .equ Mode_SVC, 0x13 .equ Mode_ABT, 0x17 .equ Mode_UND, 0x1B .equ Mode_SYS, 0x1F .equ I_Bit, 0x80 @ when I bit is set, IRQ is disabled .equ F_Bit, 0x40 @ when F bit is set, FIQ is disabled .equ UND_Stack_Size, 0x00000000 .equ SVC_Stack_Size, 0x00000400 .equ ABT_Stack_Size, 0x00000000 .equ RT_FIQ_STACK_PGSZ, 0x00000000 .equ RT_IRQ_STACK_PGSZ, 0x00000800 .equ USR_Stack_Size, 0x00000400 #define ISR_Stack_Size (UND_Stack_Size + SVC_Stack_Size + ABT_Stack_Size + \ RT_FIQ_STACK_PGSZ + RT_IRQ_STACK_PGSZ) .section .data.share.isr /* stack */ .globl stack_start .globl stack_top stack_start: .rept ISR_Stack_Size .byte 0 .endr stack_top: .text /* reset entry */ .globl _reset _reset: /* set the cpu to SVC32 mode and disable interrupt */ mrs r0, cpsr bic r0, r0, #0x1f orr r0, r0, #0x13 msr cpsr_c, r0 /* setup stack */ bl stack_setup /* clear .bss */ mov r0,#0 /* get a zero */ ldr r1,=__bss_start /* bss start */ ldr r2,=__bss_end /* bss end */ bss_loop: cmp r1,r2 /* check if data to clear */ strlo r0,[r1],#4 /* clear 4 bytes */ blo bss_loop /* loop until done */ /* call C++ constructors of global objects */ ldr r0, =__ctors_start__ ldr r1, =__ctors_end__ ctor_loop: cmp r0, r1 beq ctor_end ldr r2, [r0], #4 stmfd sp!, {r0-r1} mov lr, pc bx r2 ldmfd sp!, {r0-r1} b ctor_loop ctor_end: /* start RT-Thread Kernel */ ldr pc, _rtthread_startup _rtthread_startup: .word rtthread_startup stack_setup: ldr r0, =stack_top @ Set the startup stack for svc mov sp, r0 @ Enter Undefined Instruction Mode and set its Stack Pointer msr cpsr_c, #Mode_UND|I_Bit|F_Bit mov sp, r0 sub r0, r0, #UND_Stack_Size @ Enter Abort Mode and set its Stack Pointer msr cpsr_c, #Mode_ABT|I_Bit|F_Bit mov sp, r0 sub r0, r0, #ABT_Stack_Size @ Enter FIQ Mode and set its Stack Pointer msr cpsr_c, #Mode_FIQ|I_Bit|F_Bit mov sp, r0 sub r0, r0, #RT_FIQ_STACK_PGSZ @ Enter IRQ Mode and set its Stack Pointer msr cpsr_c, #Mode_IRQ|I_Bit|F_Bit mov sp, r0 sub r0, r0, #RT_IRQ_STACK_PGSZ /* come back to SVC mode */ msr cpsr_c, #Mode_SVC|I_Bit|F_Bit bx lr /* exception handlers: undef, swi, padt, dabt, resv, irq, fiq */ .section .text.isr, "ax" .align 5 .globl vector_fiq vector_fiq: stmfd sp!,{r0-r7,lr} bl rt_hw_trap_fiq ldmfd sp!,{r0-r7,lr} subs pc, lr, #4 .globl rt_interrupt_enter .globl rt_interrupt_leave .globl rt_thread_switch_interrupt_flag .globl rt_interrupt_from_thread .globl rt_interrupt_to_thread .globl rt_current_thread .align 5 .globl vector_irq vector_irq: stmfd sp!, {r0-r12,lr} bl rt_interrupt_enter bl rt_hw_trap_irq bl rt_interrupt_leave @ if rt_thread_switch_interrupt_flag set, jump to @ rt_hw_context_switch_interrupt_do and don't return ldr r0, =rt_thread_switch_interrupt_flag ldr r1, [r0] cmp r1, #1 beq rt_hw_context_switch_interrupt_do ldmfd sp!, {r0-r12,lr} subs pc, lr, #4 rt_hw_context_switch_interrupt_do: mov r1, #0 @ clear flag str r1, [r0] mov r1, sp @ r1 point to {r0-r3} in stack add sp, sp, #4*4 ldmfd sp!, {r4-r12,lr}@ reload saved registers mrs r0, spsr @ get cpsr of interrupt thread sub r2, lr, #4 @ save old task's pc to r2 @ Switch to SVC mode with no interrupt. If the usr mode guest is @ interrupted, this will just switch to the stack of kernel space. @ save the registers in kernel space won't trigger data abort. msr cpsr_c, #I_Bit|F_Bit|Mode_SVC stmfd sp!, {r2} @ push old task's pc stmfd sp!, {r4-r12,lr}@ push old task's lr,r12-r4 ldmfd r1, {r1-r4} @ restore r0-r3 of the interrupt thread stmfd sp!, {r1-r4} @ push old task's r0-r3 stmfd sp!, {r0} @ push old task's cpsr ldr r4, =rt_interrupt_from_thread ldr r5, [r4] str sp, [r5] @ store sp in preempted tasks's TCB ldr r6, =rt_interrupt_to_thread ldr r6, [r6] ldr sp, [r6] @ get new task's stack pointer ldmfd sp!, {r4} @ pop new task's cpsr to spsr msr spsr_cxsf, r4 ldmfd sp!, {r0-r12,lr,pc}^ @ pop new task's r0-r12,lr & pc, copy spsr to cpsr .macro push_svc_reg sub sp, sp, #17 * 4 @/* Sizeof(struct rt_hw_exp_stack) */ stmia sp, {r0 - r12} @/* Calling r0-r12 */ mov r0, sp mrs r6, spsr @/* Save CPSR */ str lr, [r0, #15*4] @/* Push PC */ str r6, [r0, #16*4] @/* Push CPSR */ cps #Mode_SVC str sp, [r0, #13*4] @/* Save calling SP */ str lr, [r0, #14*4] @/* Save calling PC */ .endm .align 5 .globl vector_swi vector_swi: push_svc_reg bl rt_hw_trap_swi b . .align 5 .globl vector_undef vector_undef: push_svc_reg bl rt_hw_trap_undef b . .align 5 .globl vector_pabt vector_pabt: push_svc_reg bl rt_hw_trap_pabt b . .align 5 .globl vector_dabt vector_dabt: push_svc_reg bl rt_hw_trap_dabt b . .align 5 .globl vector_resv vector_resv: push_svc_reg bl rt_hw_trap_resv b .