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ArmAsm
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#include "os_config.h"
#if __riscv_xlen == 64
#define REG_BYTES 8
#define STORE sd
#define LOAD ld
#define FSTORE fsd
#define FLOAD fld
#elif __riscv_xlen == 32
#define REG_BYTES 4
#define STORE sw
#define LOAD lw
#define FSTORE fsw
#define FLOAD flw
#else
#error Assembler did not define __riscv_xlen
#endif
#define CONTEXT_SIZE (32 * REG_BYTES)
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//// CODE
#ifdef OS_CFG_CPU_CLZ_ASM_PRESENT
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.section .text.cpu_clz,"ax",%progbits
.align 8
.func
.global cpu_clz
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cpu_clz:
clz a0, a0
ret
.endfunc
#endif
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.section .text.os_port_context_switch_to,"ax",%progbits
.align 2
.func
.global os_port_context_switch_to
.extern os_port_on_switch_success
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os_port_context_switch_to:
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li t0, 0x1800
csrw mstatus, t0 // 1. 关中断
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/* 设置中断栈/系统栈空间 */
la t0, _eusrstack
addi t0, t0, -512
csrw mscratch, t0 // 备用栈指针存入 mscratch
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/* =====================================================================
* 第一步:切换到中断栈,安全调用通知 C 函数
* ===================================================================== */
jal os_port_on_switch_success // 调用 C 函数(此时随便它怎么污染寄存器)
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/* =====================================================================
* 第二步:获取新任务的栈指针 SP
* ===================================================================== */
LOAD sp, 0(a0) // a0 是传入的 &g_os_port_switch_to_sp,从中取出 sp
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/* =====================================================================
* 第三步:恢复 FPU 浮点寄存器(与保存栈帧严格镜像)
* 修复宏定义:将 MPU 改回 FPU
* ===================================================================== */
#if (OS_CFG_CPU_FPU_PRESENT)
FLOAD f0, (CONTEXT_SIZE + 0 * REG_BYTES)(sp)
FLOAD f1, (CONTEXT_SIZE + 1 * REG_BYTES)(sp)
FLOAD f2, (CONTEXT_SIZE + 2 * REG_BYTES)(sp)
FLOAD f3, (CONTEXT_SIZE + 3 * REG_BYTES)(sp)
FLOAD f4, (CONTEXT_SIZE + 4 * REG_BYTES)(sp)
FLOAD f5, (CONTEXT_SIZE + 5 * REG_BYTES)(sp)
FLOAD f6, (CONTEXT_SIZE + 6 * REG_BYTES)(sp)
FLOAD f7, (CONTEXT_SIZE + 7 * REG_BYTES)(sp)
FLOAD f8, (CONTEXT_SIZE + 8 * REG_BYTES)(sp)
FLOAD f9, (CONTEXT_SIZE + 9 * REG_BYTES)(sp)
FLOAD f10, (CONTEXT_SIZE + 10 * REG_BYTES)(sp)
FLOAD f11, (CONTEXT_SIZE + 11 * REG_BYTES)(sp)
FLOAD f12, (CONTEXT_SIZE + 12 * REG_BYTES)(sp)
FLOAD f13, (CONTEXT_SIZE + 13 * REG_BYTES)(sp)
FLOAD f14, (CONTEXT_SIZE + 14 * REG_BYTES)(sp)
FLOAD f15, (CONTEXT_SIZE + 15 * REG_BYTES)(sp)
FLOAD f16, (CONTEXT_SIZE + 16 * REG_BYTES)(sp)
FLOAD f17, (CONTEXT_SIZE + 17 * REG_BYTES)(sp)
FLOAD f18, (CONTEXT_SIZE + 18 * REG_BYTES)(sp)
FLOAD f19, (CONTEXT_SIZE + 19 * REG_BYTES)(sp)
FLOAD f20, (CONTEXT_SIZE + 20 * REG_BYTES)(sp)
FLOAD f21, (CONTEXT_SIZE + 21 * REG_BYTES)(sp)
FLOAD f22, (CONTEXT_SIZE + 22 * REG_BYTES)(sp)
FLOAD f23, (CONTEXT_SIZE + 23 * REG_BYTES)(sp)
FLOAD f24, (CONTEXT_SIZE + 24 * REG_BYTES)(sp)
FLOAD f25, (CONTEXT_SIZE + 25 * REG_BYTES)(sp)
FLOAD f26, (CONTEXT_SIZE + 26 * REG_BYTES)(sp)
FLOAD f27, (CONTEXT_SIZE + 27 * REG_BYTES)(sp)
FLOAD f28, (CONTEXT_SIZE + 28 * REG_BYTES)(sp)
FLOAD f29, (CONTEXT_SIZE + 29 * REG_BYTES)(sp)
FLOAD f30, (CONTEXT_SIZE + 30 * REG_BYTES)(sp)
FLOAD f31, (CONTEXT_SIZE + 31 * REG_BYTES)(sp)
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#endif
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/* =====================================================================
* 第四步:恢复通用寄存器(最后恢复 t0
* ===================================================================== */
LOAD x1, 1 * REG_BYTES(sp)
LOAD x4, 4 * REG_BYTES(sp)
LOAD x6, 6 * REG_BYTES(sp)
LOAD x7, 7 * REG_BYTES(sp)
LOAD x8, 8 * REG_BYTES(sp)
LOAD x9, 9 * REG_BYTES(sp)
LOAD x10, 10 * REG_BYTES(sp)
LOAD x11, 11 * REG_BYTES(sp)
LOAD x12, 12 * REG_BYTES(sp)
LOAD x13, 13 * REG_BYTES(sp)
LOAD x14, 14 * REG_BYTES(sp)
LOAD x15, 15 * REG_BYTES(sp)
LOAD x16, 16 * REG_BYTES(sp)
LOAD x17, 17 * REG_BYTES(sp)
LOAD x18, 18 * REG_BYTES(sp)
LOAD x19, 19 * REG_BYTES(sp)
LOAD x20, 20 * REG_BYTES(sp)
LOAD x21, 21 * REG_BYTES(sp)
LOAD x22, 22 * REG_BYTES(sp)
LOAD x23, 23 * REG_BYTES(sp)
LOAD x24, 24 * REG_BYTES(sp)
LOAD x25, 25 * REG_BYTES(sp)
LOAD x26, 26 * REG_BYTES(sp)
LOAD x27, 27 * REG_BYTES(sp)
LOAD x28, 28 * REG_BYTES(sp)
LOAD x29, 29 * REG_BYTES(sp)
LOAD x30, 30 * REG_BYTES(sp)
LOAD x31, 31 * REG_BYTES(sp)
/* =====================================================================
* 第五步:恢复特权级控制 CSR 寄存器
* ===================================================================== */
LOAD t0, 2 * REG_BYTES(sp) // 恢复初始 PC mepc
csrw mepc, t0
LOAD t0, 0 * REG_BYTES(sp) // 从栈中读取准备好的初始 mstatus
csrw mstatus, t0 // 修复:改用 csrw 强行覆盖
LOAD x5, 5 * REG_BYTES(sp) // 此时最后安全恢复 t0(x5)
/* =====================================================================
* 第六步:统一释放栈空间并退出
* ===================================================================== */
#if (OS_CFG_CPU_FPU_PRESENT)
addi sp, sp, (CONTEXT_SIZE + 32 * REG_BYTES)
#else
addi sp, sp, CONTEXT_SIZE
#endif
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mret
.endfunc
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.section .text.SW_Handler,"ax",%progbits
.align 2
.func
.global SW_Handler
.extern g_os_port_switch_from_sp
.extern g_os_port_switch_to_sp
.extern os_port_on_switch_success
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SW_Handler:
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csrci mstatus, 0x08 // 立刻关闭全局中断 MIE = 0
/* =====================================================================
* 第一步:一揽子分配所有栈空间(防止碎片和二次偏移错误)
* ===================================================================== */
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#if (OS_CFG_CPU_FPU_PRESENT)
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addi sp, sp, -(CONTEXT_SIZE + 32 * REG_BYTES)
#else
addi sp, sp, -CONTEXT_SIZE
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#endif
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/* =====================================================================
* 第二步:保存通用寄存器
* ===================================================================== */
STORE x5, 5 * REG_BYTES(sp) // 优先保存 t0,腾出临时寄存器
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li t0, 0x1800
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csrw mstatus, t0 // M 模式
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li t0, 0x1880
STORE t0, 0 * REG_BYTES(sp) // 设置 MPIE
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csrr t0, mepc
STORE t0, 2*REG_BYTES(sp) // 保存正在运行任务的 pc 指针
STORE x1, 1 * REG_BYTES(sp) // ra
STORE x4, 4 * REG_BYTES(sp) // tp
STORE x6, 6 * REG_BYTES(sp) // t1
STORE x7, 7 * REG_BYTES(sp) // t2
STORE x8, 8 * REG_BYTES(sp) // s0/fp
STORE x9, 9 * REG_BYTES(sp) // s1
STORE x10, 10 * REG_BYTES(sp) // a0
STORE x11, 11 * REG_BYTES(sp) // a1
STORE x12, 12 * REG_BYTES(sp) // a2
STORE x13, 13 * REG_BYTES(sp) // a3
STORE x14, 14 * REG_BYTES(sp) // a4
STORE x15, 15 * REG_BYTES(sp) // a5
STORE x16, 16 * REG_BYTES(sp) // a6
STORE x17, 17 * REG_BYTES(sp) // a7
STORE x18, 18 * REG_BYTES(sp) // s2
STORE x19, 19 * REG_BYTES(sp) // s3
STORE x20, 20 * REG_BYTES(sp) // s4
STORE x21, 21 * REG_BYTES(sp) // s5
STORE x22, 22 * REG_BYTES(sp) // s6
STORE x23, 23 * REG_BYTES(sp) // s7
STORE x24, 24 * REG_BYTES(sp) // s8
STORE x25, 25 * REG_BYTES(sp) // s9
STORE x26, 26 * REG_BYTES(sp) // s10
STORE x27, 27 * REG_BYTES(sp) // s11
STORE x28, 28 * REG_BYTES(sp) // t3
STORE x29, 29 * REG_BYTES(sp) // t4
STORE x30, 30 * REG_BYTES(sp) // t5
STORE x31, 31 * REG_BYTES(sp) // t6
/* =====================================================================
* 第三步:保存 FPU 浮点寄存器(使用确定的、不受干扰的高位偏移)
* ===================================================================== */
#if (OS_CFG_CPU_FPU_PRESENT)
FSTORE f0, (CONTEXT_SIZE + 0 * REG_BYTES)(sp)
FSTORE f1, (CONTEXT_SIZE + 1 * REG_BYTES)(sp)
FSTORE f2, (CONTEXT_SIZE + 2 * REG_BYTES)(sp)
FSTORE f3, (CONTEXT_SIZE + 3 * REG_BYTES)(sp)
FSTORE f4, (CONTEXT_SIZE + 4 * REG_BYTES)(sp)
FSTORE f5, (CONTEXT_SIZE + 5 * REG_BYTES)(sp)
FSTORE f6, (CONTEXT_SIZE + 6 * REG_BYTES)(sp)
FSTORE f7, (CONTEXT_SIZE + 7 * REG_BYTES)(sp)
FSTORE f8, (CONTEXT_SIZE + 8 * REG_BYTES)(sp)
FSTORE f9, (CONTEXT_SIZE + 9 * REG_BYTES)(sp)
FSTORE f10, (CONTEXT_SIZE + 10 * REG_BYTES)(sp)
FSTORE f11, (CONTEXT_SIZE + 11 * REG_BYTES)(sp)
FSTORE f12, (CONTEXT_SIZE + 12 * REG_BYTES)(sp)
FSTORE f13, (CONTEXT_SIZE + 13 * REG_BYTES)(sp)
FSTORE f14, (CONTEXT_SIZE + 14 * REG_BYTES)(sp)
FSTORE f15, (CONTEXT_SIZE + 15 * REG_BYTES)(sp)
FSTORE f16, (CONTEXT_SIZE + 16 * REG_BYTES)(sp)
FSTORE f17, (CONTEXT_SIZE + 17 * REG_BYTES)(sp)
FSTORE f18, (CONTEXT_SIZE + 18 * REG_BYTES)(sp)
FSTORE f19, (CONTEXT_SIZE + 19 * REG_BYTES)(sp)
FSTORE f20, (CONTEXT_SIZE + 20 * REG_BYTES)(sp)
FSTORE f21, (CONTEXT_SIZE + 21 * REG_BYTES)(sp)
FSTORE f22, (CONTEXT_SIZE + 22 * REG_BYTES)(sp)
FSTORE f23, (CONTEXT_SIZE + 23 * REG_BYTES)(sp)
FSTORE f24, (CONTEXT_SIZE + 24 * REG_BYTES)(sp)
FSTORE f25, (CONTEXT_SIZE + 25 * REG_BYTES)(sp)
FSTORE f26, (CONTEXT_SIZE + 26 * REG_BYTES)(sp)
FSTORE f27, (CONTEXT_SIZE + 27 * REG_BYTES)(sp)
FSTORE f28, (CONTEXT_SIZE + 28 * REG_BYTES)(sp)
FSTORE f29, (CONTEXT_SIZE + 29 * REG_BYTES)(sp)
FSTORE f30, (CONTEXT_SIZE + 30 * REG_BYTES)(sp)
FSTORE f31, (CONTEXT_SIZE + 31 * REG_BYTES)(sp)
#endif
/* =====================================================================
* 第四步:保存旧任务 sp,并安全调用通知函数
* ===================================================================== */
la t0, g_os_port_switch_from_sp
LOAD t0, 0(t0)
STORE sp, 0(t0) // sp 存入 g_os_port_switch_from_sp
// 此时调用 C 函数是完全安全的,因为所有寄存器都已在任务栈里备考
jal os_port_on_switch_success
/* =====================================================================
* 第五步:载入新任务的栈指针(SP
* ===================================================================== */
la t0, g_os_port_switch_to_sp
LOAD t0, 0(t0)
LOAD sp, 0(t0) // sp 指向 g_os_port_switch_to_sp
/* =====================================================================
* 第六步:恢复新任务的 FPU 浮点寄存器
* ===================================================================== */
#if (OS_CFG_CPU_FPU_PRESENT)
FLOAD f0, (CONTEXT_SIZE + 0 * REG_BYTES)(sp)
FLOAD f1, (CONTEXT_SIZE + 1 * REG_BYTES)(sp)
FLOAD f2, (CONTEXT_SIZE + 2 * REG_BYTES)(sp)
FLOAD f3, (CONTEXT_SIZE + 3 * REG_BYTES)(sp)
FLOAD f4, (CONTEXT_SIZE + 4 * REG_BYTES)(sp)
FLOAD f5, (CONTEXT_SIZE + 5 * REG_BYTES)(sp)
FLOAD f6, (CONTEXT_SIZE + 6 * REG_BYTES)(sp)
FLOAD f7, (CONTEXT_SIZE + 7 * REG_BYTES)(sp)
FLOAD f8, (CONTEXT_SIZE + 8 * REG_BYTES)(sp)
FLOAD f9, (CONTEXT_SIZE + 9 * REG_BYTES)(sp)
FLOAD f10, (CONTEXT_SIZE + 10 * REG_BYTES)(sp)
FLOAD f11, (CONTEXT_SIZE + 11 * REG_BYTES)(sp)
FLOAD f12, (CONTEXT_SIZE + 12 * REG_BYTES)(sp)
FLOAD f13, (CONTEXT_SIZE + 13 * REG_BYTES)(sp)
FLOAD f14, (CONTEXT_SIZE + 14 * REG_BYTES)(sp)
FLOAD f15, (CONTEXT_SIZE + 15 * REG_BYTES)(sp)
FLOAD f16, (CONTEXT_SIZE + 16 * REG_BYTES)(sp)
FLOAD f17, (CONTEXT_SIZE + 17 * REG_BYTES)(sp)
FLOAD f18, (CONTEXT_SIZE + 18 * REG_BYTES)(sp)
FLOAD f19, (CONTEXT_SIZE + 19 * REG_BYTES)(sp)
FLOAD f20, (CONTEXT_SIZE + 20 * REG_BYTES)(sp)
FLOAD f21, (CONTEXT_SIZE + 21 * REG_BYTES)(sp)
FLOAD f22, (CONTEXT_SIZE + 22 * REG_BYTES)(sp)
FLOAD f23, (CONTEXT_SIZE + 23 * REG_BYTES)(sp)
FLOAD f24, (CONTEXT_SIZE + 24 * REG_BYTES)(sp)
FLOAD f25, (CONTEXT_SIZE + 25 * REG_BYTES)(sp)
FLOAD f26, (CONTEXT_SIZE + 26 * REG_BYTES)(sp)
FLOAD f27, (CONTEXT_SIZE + 27 * REG_BYTES)(sp)
FLOAD f28, (CONTEXT_SIZE + 28 * REG_BYTES)(sp)
FLOAD f29, (CONTEXT_SIZE + 29 * REG_BYTES)(sp)
FLOAD f30, (CONTEXT_SIZE + 30 * REG_BYTES)(sp)
FLOAD f31, (CONTEXT_SIZE + 31 * REG_BYTES)(sp)
#endif
/* =====================================================================
* 第七步:全面恢复通用寄存器(最后恢复 t0
* ===================================================================== */
LOAD x1, 1 * REG_BYTES(sp)
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LOAD x4, 4 * REG_BYTES(sp)
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// LOAD x5, 5 * REG_BYTES(sp) // 恢复 t0
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LOAD x6, 6 * REG_BYTES(sp)
LOAD x7, 7 * REG_BYTES(sp)
LOAD x8, 8 * REG_BYTES(sp)
LOAD x9, 9 * REG_BYTES(sp)
LOAD x10, 10 * REG_BYTES(sp)
LOAD x11, 11 * REG_BYTES(sp)
LOAD x12, 12 * REG_BYTES(sp)
LOAD x13, 13 * REG_BYTES(sp)
LOAD x14, 14 * REG_BYTES(sp)
LOAD x15, 15 * REG_BYTES(sp)
LOAD x16, 16 * REG_BYTES(sp)
LOAD x17, 17 * REG_BYTES(sp)
LOAD x18, 18 * REG_BYTES(sp)
LOAD x19, 19 * REG_BYTES(sp)
LOAD x20, 20 * REG_BYTES(sp)
LOAD x21, 21 * REG_BYTES(sp)
LOAD x22, 22 * REG_BYTES(sp)
LOAD x23, 23 * REG_BYTES(sp)
LOAD x24, 24 * REG_BYTES(sp)
LOAD x25, 25 * REG_BYTES(sp)
LOAD x26, 26 * REG_BYTES(sp)
LOAD x27, 27 * REG_BYTES(sp)
LOAD x28, 28 * REG_BYTES(sp)
LOAD x29, 29 * REG_BYTES(sp)
LOAD x30, 30 * REG_BYTES(sp)
LOAD x31, 31 * REG_BYTES(sp)
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/* =====================================================================
* 第八步:恢复新任务的 CSR 寄存器
* ===================================================================== */
LOAD t0, 2 * REG_BYTES(sp) // 恢复 mepc
csrw mepc, t0
LOAD t0, 0 * REG_BYTES(sp) // 恢复 mstatus
csrw mstatus, t0
LOAD x5, 5 * REG_BYTES(sp) // 恢复 t0
/* =====================================================================
* 第九步:彻底释放栈空间并退出
* ===================================================================== */
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#if (OS_CFG_CPU_FPU_PRESENT)
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addi sp, sp, (CONTEXT_SIZE + 32 * REG_BYTES)
#else
addi sp, sp, CONTEXT_SIZE
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#endif
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/* 执行 mret。此时:
* 1. 硬件会自动把当前 mstatus.MPIE (1) 复制到 mstatus.MIE,从而开启全局中断。
* 2. 程序跳转到 mepc 寄存器指向的地址(即新任务继续运行的代码处)。 */
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mret // M 模式退出
.endfunc
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.section .text.SysTick_Handler,"ax",%progbits
.align 2
.global SysTick_Handler
.extern SysTick_Handler_C
.func
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SysTick_Handler:
// csrci mstatus, 8 // 关闭中断
/* 1. 因为是硬件中断,先在当前栈上保存必要的临时寄存器(Caller-saved) */
addi sp, sp, -16 * REG_BYTES
STORE x1, 0 * REG_BYTES(sp) # ra
STORE x5, 1 * REG_BYTES(sp) # t0
STORE x6, 2 * REG_BYTES(sp) # t1
STORE x7, 3 * REG_BYTES(sp) # t2
STORE x10, 4 * REG_BYTES(sp) # a0
STORE x11, 5 * REG_BYTES(sp) # a1
STORE x12, 6 * REG_BYTES(sp) # a2
STORE x13, 7 * REG_BYTES(sp) # a3
STORE x14, 8 * REG_BYTES(sp) # a4
STORE x15, 9 * REG_BYTES(sp) # a5
STORE x16, 10 * REG_BYTES(sp) # a6
STORE x17, 11 * REG_BYTES(sp) # a7
STORE x28, 12 * REG_BYTES(sp) # t3
STORE x29, 13 * REG_BYTES(sp) # t4
STORE x30, 14 * REG_BYTES(sp) # t5
STORE x31, 15 * REG_BYTES(sp) # t6
/* 2. 清除定时器硬件中断标志位(防止重复触发),并调用 C 语言的时钟处理函数 */
jal SysTick_Handler_C
/* 3. 恢复临时寄存器 */
LOAD x1, 0 * REG_BYTES(sp) # ra
LOAD x5, 1 * REG_BYTES(sp) # t0
LOAD x6, 2 * REG_BYTES(sp) # t1
LOAD x7, 3 * REG_BYTES(sp) # t2
LOAD x10, 4 * REG_BYTES(sp) # a0
LOAD x11, 5 * REG_BYTES(sp) # a1
LOAD x12, 6 * REG_BYTES(sp) # a2
LOAD x13, 7 * REG_BYTES(sp) # a3
LOAD x14, 8 * REG_BYTES(sp) # a4
LOAD x15, 9 * REG_BYTES(sp) # a5
LOAD x16, 10 * REG_BYTES(sp) # a6
LOAD x17, 11 * REG_BYTES(sp) # a7
LOAD x28, 12 * REG_BYTES(sp) # t3
LOAD x29, 13 * REG_BYTES(sp) # t4
LOAD x30, 14 * REG_BYTES(sp) # t5
LOAD x31, 15 * REG_BYTES(sp) # t6
addi sp, sp, 16 * REG_BYTES
/* 4. 退出硬件中断 */
mret
.endfunc
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.align 4
.end