93 lines
1.7 KiB
ArmAsm
Executable File
93 lines
1.7 KiB
ArmAsm
Executable File
.syntax unified
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@ .cpu cortex-m3
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.thumb
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.global mpu_switch_to
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.global sched_reset
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.global PendSV_Handler
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.type PendSV_Handler, %function
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PendSV_Handler:
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CPSID I
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// psp和msp作为任务切换的参数
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MRS R0,PSP
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MRS R1,MSP
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// 如果不是第一次调度了，则保存r4-r11到栈内
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TST LR,#4
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ITE EQ
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MRSEQ r3, MSP
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MRSNE r3, PSP
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mov r2, lr
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push {r4}
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ldr r4, =sched_reset
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ldr r4, [r4]
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//! psp为零时，立刻调度一次
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CBZ r4, thread_sche
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pop {r4}
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SUB R3, R3, #0x20 //R3 -= 32
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STM R3, {R4-R11}
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//将更改的值放回要传的参数中去
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TST LR,#4
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ITTEE EQ
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MSREQ MSP, r3
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MOVEQ r1,r3
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MSRNE PSP, r3
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MOVNE r0,r3
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b thread_sche_next
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thread_sche:
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pop {r4}
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thread_sche_next:
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// r0:psp r1:msp r2:(0为msp 1 psp)
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LDR.w r3,=schde_to
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BLX r3
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//取得下一个任务的参数 r1 psp r2 msp
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lDRD r1,r2,[r0]
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//用户使用的栈类型r3 0为msp 1为ps
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LDR r3,[R0,#8]
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TST r3,#4 //检测使用的寄存器
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ITE EQ
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MOVEQ R0,R2
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MOVNE R0,R1 //不等于零则使用psp
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LDM r0, {R4-R11} //恢复新的r4-r11的值
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ADDS r0, r0, #0x20 //R0 += 0x20
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//保存栈的值回去
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MSR MSP,R2
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MSR PSP,R1
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//等于一跳转到用户模式
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@ CMP r3,#1
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TST r3,#4 //检测使用的寄存器
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IT EQ
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BEQ super_mode//psp模式则跳转
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B user_mode
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user_mode:
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//psp模式则保存
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MSR PSP, r0
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//切换到用户线程模式
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MOV R1,#1
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MSR CONTROL, R1
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//lr 的第2位为1时自动切换到PSP
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MOV LR,r3
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B to_ret
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super_mode: //更新下msp的值
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MSR MSP,R0
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MOV LR,r3
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//内核线程，设置为特权模式
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MOV R0,#0
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MSR CONTROL, R0
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to_ret:
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push {r0-r3, lr}
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bl mpu_switch_to
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pop {r0-r3, lr}
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CPSIE I
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DSB
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ISB
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BX LR
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