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Collapse asm into one file

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Working across 4 files was a pain to figure out _exactly_ what was used.

Collapsed all into one file for ease
This commit is contained in:
Ben V. Brown
2020-11-08 22:10:43 +11:00
parent fa06633539
commit fdec7bc0a3
4 changed files with 416 additions and 737 deletions
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538
workspace/TS100/Core/BSP/Pine64/N200/portasm.S
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@@ -2,11 +2,6 @@
#include "riscv_bits.h"
#include "n200_timer.h"
#include "n200_eclic.h"
#include "riscv_encoding.h"
#include "riscv_bits.h"
#include "n200_timer.h"
#include "n200_eclic.h"
#define USE_MSP 1 //启用中断栈
@@ -19,8 +14,295 @@
.global vPortEndScheduler
.global vPortAsmAssertSP
.section .init
.weak eclic_msip_handler //弱定义函数，这些在编译为bin后可以看到将全部为0
.weak eclic_mtip_handler
.weak eclic_bwei_handler
.weak eclic_pmovi_handler
.weak WWDGT_IRQHandler
.weak LVD_IRQHandler
.weak TAMPER_IRQHandler
.weak RTC_IRQHandler
.weak FMC_IRQHandler
.weak RCU_IRQHandler
.weak EXTI0_IRQHandler
.weak EXTI1_IRQHandler
.weak EXTI2_IRQHandler
.weak EXTI3_IRQHandler
.weak EXTI4_IRQHandler
.weak DMA0_Channel0_IRQHandler
.weak DMA0_Channel1_IRQHandler
.weak DMA0_Channel2_IRQHandler
.weak DMA0_Channel3_IRQHandler
.weak DMA0_Channel4_IRQHandler
.weak DMA0_Channel5_IRQHandler
.weak DMA0_Channel6_IRQHandler
.weak ADC0_1_IRQHandler
.weak CAN0_TX_IRQHandler
.weak CAN0_RX0_IRQHandler
.weak CAN0_RX1_IRQHandler
.weak CAN0_EWMC_IRQHandler
.weak EXTI5_9_IRQHandler
.weak TIMER0_BRK_IRQHandler
.weak TIMER0_UP_IRQHandler
.weak TIMER0_TRG_CMT_IRQHandler
.weak TIMER0_Channel_IRQHandler
.weak TIMER1_IRQHandler
.weak TIMER2_IRQHandler
.weak TIMER3_IRQHandler
.weak I2C0_EV_IRQHandler
.weak I2C0_ER_IRQHandler
.weak I2C1_EV_IRQHandler
.weak I2C1_ER_IRQHandler
.weak SPI0_IRQHandler
.weak SPI1_IRQHandler
.weak USART0_IRQHandler
.weak USART1_IRQHandler
.weak USART2_IRQHandler
.weak EXTI10_15_IRQHandler
.weak RTC_Alarm_IRQHandler
.weak USBFS_WKUP_IRQHandler
.weak EXMC_IRQHandler
.weak TIMER4_IRQHandler
.weak SPI2_IRQHandler
.weak UART3_IRQHandler
.weak UART4_IRQHandler
.weak TIMER5_IRQHandler
.weak TIMER6_IRQHandler
.weak DMA1_Channel0_IRQHandler
.weak DMA1_Channel1_IRQHandler
.weak DMA1_Channel2_IRQHandler
.weak DMA1_Channel3_IRQHandler
.weak DMA1_Channel4_IRQHandler
.weak CAN1_TX_IRQHandler
.weak CAN1_RX0_IRQHandler
.weak CAN1_RX1_IRQHandler
.weak CAN1_EWMC_IRQHandler
.weak USBFS_IRQHandler
vector_base: //中断向量表
j _start //第一条指令即跳转到_start处开始执行
.align 2
.word 0
.word 0
.word eclic_msip_handler
.word 0
.word 0
.word 0
.word eclic_mtip_handler
.word 0
.word 0
.word 0
.word 0
.word 0
.word 0
.word 0
.word 0
.word 0
.word eclic_bwei_handler
.word eclic_pmovi_handler
.word WWDGT_IRQHandler
.word LVD_IRQHandler
.word TAMPER_IRQHandler
.word RTC_IRQHandler
.word FMC_IRQHandler
.word RCU_IRQHandler
.word EXTI0_IRQHandler
.word EXTI1_IRQHandler
.word EXTI2_IRQHandler
.word EXTI3_IRQHandler
.word EXTI4_IRQHandler
.word DMA0_Channel0_IRQHandler
.word DMA0_Channel1_IRQHandler
.word DMA0_Channel2_IRQHandler
.word DMA0_Channel3_IRQHandler
.word DMA0_Channel4_IRQHandler
.word DMA0_Channel5_IRQHandler
.word DMA0_Channel6_IRQHandler
.word ADC0_1_IRQHandler
.word CAN0_TX_IRQHandler
.word CAN0_RX0_IRQHandler
.word CAN0_RX1_IRQHandler
.word CAN0_EWMC_IRQHandler
.word EXTI5_9_IRQHandler
.word TIMER0_BRK_IRQHandler
.word TIMER0_UP_IRQHandler
.word TIMER0_TRG_CMT_IRQHandler
.word TIMER0_Channel_IRQHandler
.word TIMER1_IRQHandler
.word TIMER2_IRQHandler
.word TIMER3_IRQHandler
.word I2C0_EV_IRQHandler
.word I2C0_ER_IRQHandler
.word I2C1_EV_IRQHandler
.word I2C1_ER_IRQHandler
.word SPI0_IRQHandler
.word SPI1_IRQHandler
.word USART0_IRQHandler
.word USART1_IRQHandler
.word USART2_IRQHandler
.word EXTI10_15_IRQHandler
.word RTC_Alarm_IRQHandler
.word USBFS_WKUP_IRQHandler
.word 0
.word 0
.word 0
.word 0
.word 0
.word EXMC_IRQHandler
.word 0
.word TIMER4_IRQHandler
.word SPI2_IRQHandler
.word UART3_IRQHandler
.word UART4_IRQHandler
.word TIMER5_IRQHandler
.word TIMER6_IRQHandler
.word DMA1_Channel0_IRQHandler
.word DMA1_Channel1_IRQHandler
.word DMA1_Channel2_IRQHandler
.word DMA1_Channel3_IRQHandler
.word DMA1_Channel4_IRQHandler
.word 0
.word 0
.word CAN1_TX_IRQHandler
.word CAN1_RX0_IRQHandler
.word CAN1_RX1_IRQHandler
.word CAN1_EWMC_IRQHandler
.word USBFS_IRQHandler
.globl _start
.type _start,@function
_start:
csrc CSR_MSTATUS, MSTATUS_MIE //CSR_MSTATUS &= ~0x8 mstatus[3]:0屏蔽全部中断 1不屏蔽全部中断 （当然这里全部中断是除过不可屏蔽中断）
/* Jump to logical address first to ensure correct operation of RAM region */
la a0, _start //a0 = _start
li a1, 1 //a1 = 1
slli a1, a1, 29 //a1 = 0x20000000 raw起始地址
bleu a1, a0, _start0800 //if( a1 <= a0 ) JUMP _start0800
srli a1, a1, 2 //a1 = 0x08000000 flash起始地址
bleu a1, a0, _start0800 //if( a1 <= a0 ) JUMP _start0800
la a0, _start0800 //a0 = _start0800
add a0, a0, a1 //a0 = a0+a1
jr a0 //JUMP a0
_start0800:
/* Set the the NMI base to share with mtvec by setting CSR_MMISC_CTL */
li t0, 0x200 //t0 = 0x200
csrs CSR_MMISC_CTL, t0 //mmisc_ctl |= 0x200 CSR_MMISC_CTL[9]：设置NMI的地址与mtvec相同且，mcause.EXCCODE = 0xfff
//cs开头的指令是特有的用来操作内核寄存器的的指令，内核寄存器是一组特有的12位地址
/* Intial the mtvt*/
la t0, vector_base //t0 = vector_base 向量表地址
csrw CSR_MTVT, t0 //mtvt = vector_base 中断向量表基地址
/* Intial the mtvt2 and enable it*/
la t0, irq_entry //t0 = irq_entry irq_entry定义在entry.S,有freertos操作系统情况下定义在portasm.S
csrw CSR_MTVT2, t0 //mtvt2 = irq_entry mtvt2[31:2]: 中断入口函数地址
csrs CSR_MTVT2, 0x1 //mtvt2 |= 0x1 mtvt2[0]: 1配置mtvt2的配置有效，配0则为mtvec内地址
/* Intial the CSR MTVEC for the Trap ane NMI base addr*/
la t0, trap_entry //t0 = trap_entry trap_entry定义在entry.S,有freertos操作系统情况下定义在portasm.S
csrw CSR_MTVEC, t0 //mtvec = trap_entry mtvec[31:6]：异常入口地址
// mtvec[5:0]：0B00011 -- ECLIC中断模式 其他：默认模式
// 这里配置为默认模式
// trap_entry基本上可以理解为arm里的hard/mem/use/svc等fault了，
// 这里在移植freertos时就使用了 ecall 进入trap_entry里 相当于arm里的PendSVC
/* OS启动前配置中断栈为FHEAP的end地址 */
la t0, ucHeap
csrw CSR_MSCRATCH, t0
#ifdef __riscv_flen //浮点宏
/* Enable FPU */
li t0, MSTATUS_FS //t0 = 0x6000
csrs mstatus, t0 //mstatus |= 0x6000 mstatus[14:13]:非零值启用浮点单元，配置为1或2会在第一次使用浮点单元时变为3，这里直接配置为3
csrw fcsr, x0 //fcsr = x0 = 0 ??这里x0是否指的是zero通用寄存器值? 这个寄存器0-4位是浮点异常状态标志，5-7位是浮点舍入模式配置
#endif
.option push
.option norelax
la gp, __global_pointer$ //__global_pointer$定义在link连接脚本内，指向所有.data段后偏移0x800的地址,0x800为2K，其值源于下文解释
//gp 意为global pointer （全局指针）寄存器是一个解决方案，
//为了以进一步优化存储器访问单个4KB区域内。
//链接器使用__global_pointer$符号定义来比较内存地址，如果在范围内，
//则它将绝对/相对pc寻址替换为gp相对寻址，从而使代码更有效。这个过程通过-Wl,--no-relax选项使用。
//这里.option norelax起到-Wl,--no-relax作用，就不需要在编译选项添加了
//上文参考自：https://gnu-mcu-eclipse.github.io/arch/riscv/programmer/#the-gp-global-pointer-register
//要让 relaxing 优化起作用，编译时要加入 -msmall-data-limit=n 参数，有了这个参数，
//编译器会把内存空间小于 n 字节的静态变量放入 .sdata 或者 .sdata.* 节，
//然后链接器将这部分静态变量集中在 __global_pointer$ +/- 2K 的范围内。
//上文参考自：https://blog.csdn.net/zoomdy/article/details/100703451
.option pop
la sp, _sp //sp = 主栈栈顶地址 _sp定义在link连接脚本内
/* Load data section */
la a0, _data_lma //a0 = data的Load Memory Address _data_lma定义在link连接脚本内
la a1, _data //a1 = data的Run Memory Address _data定义在link连接脚本内
la a2, _edata //a2 = data的Run Memory Address结束地址 _edata定义在link连接脚本内
bgeu a1, a2, 2f //if( a1 >= a2 ) JUMP 2f 原则上不会出现_data地址大于_edata地址
//如果出现了则直接跳转到 2f 即下一个2标签
1:
lw t0, (a0) //t0 = _data_lma
sw t0, (a1) //*_data = t0 即 *_data_lma，按word写入
addi a0, a0, 4 //a0 = a0 + 4 下一个ward
addi a1, a1, 4 //a1 = a1 + 4
bltu a1, a2, 1b //if( a1 < a2 ) JUMP 1b 如果未到达_edata则跳转到 1b 即上一个1标签，这里会完成一个循环
2:
/* Clear bss section */
la a0, __bss_start //a0 = __bss_start 初值为0的全局变量段起始地址 __bss_start定义在link连接脚本内
la a1, _end //a1 = _end 初值为0的全局变量段结束地址 _end定义在link连接脚本内
bgeu a0, a1, 2f //if( a0 >= a1 ) JUMP 2f 原则上不会出现__bss_start地址大于_end地址
//如果出现了则直接跳转到 2f 即下一个2标签
1:
sw zero, (a0) //*__bss_start = zero = 0 bss段清除为0
addi a0, a0, 4 //a0 = a0 + 4 下一个ward
bltu a0, a1, 1b //if( a0 < a1 ) JUMP 1b 如果未到达_end则跳转到 1b 即上一个1标签，这里会完成一个循环
//程序执行到这里全局变量就以及处理完毕了
2:
/*enable mcycle_minstret*/
csrci CSR_MCOUNTINHIBIT, 0x5 //CSR_MCOUNTINHIBIT &= ~0x5 这里清零了第0bit和第1bit，使能了mcycle计数和minstret计数
//csrci这条指令处理立即数5bit，列如0x5只是0B00101，高位不处理
/*
* Call vendor defined SystemInit to
* initialize the micro-controller system
*/
call SystemInit
/* Call global constructors */
la a0, __libc_fini_array //a0 = __libc_fini_array newlib中atexit函数的参数
call atexit //调用newlib中的 void atexit(void (*func)(void)) 函数
//功能为注册main函数结束后调用的函数，这里是__libc_fini_array
call __libc_init_array //调用newlib中的 void __libc_init_array (void) 函数
//这里要注意__libc_init_array函数会调用_init的钩子函数，用来做c环境初始化前的一些硬件初始化
//列如时钟的配置等，这里_init定义在init.c
//程序执行到这里C/C++环境就初始化完成了，可以进入main函数入口了
/* argc = argv = 0 */
li a0, 0 //a0 = 0 main函数参数argc = 0
li a1, 0 //a1 = 0 main函数参数argv = 0
call main //调用 int main(int argc,char **argv) 函数
tail exit //main返回后调用newlib的exit函数, tail指令应该是不会返回的调用函数了
1:
j 1b //1b 即上一次1标签，即跳转到自己，程序到这里就死循环了，原则不会运行到这里
.global disable_mcycle_minstret
disable_mcycle_minstret:
csrsi CSR_MCOUNTINHIBIT, 0x5 //关闭了mcycle计数和minstret计数
ret
.global enable_mcycle_minstret
enable_mcycle_minstret:
csrci CSR_MCOUNTINHIBIT, 0x5 //使能了mcycle计数和minstret计数
ret
/**
* @brife 压栈通用寄存器
* @brief 压栈通用寄存器
* @param x 目标sp寄存器
*/
.macro pushREGFILE x
@@ -31,8 +313,8 @@
#endif
STORE x1, 1 * REGBYTES(\x)
STORE x2, 2 * REGBYTES(\x)
//STORE x3, 3 * REGBYTES(\x)
//STORE x4, 4 * REGBYTES(\x)
#STORE x3, 3 * REGBYTES(\x)
#STORE x4, 4 * REGBYTES(\x)
STORE x5, 5 * REGBYTES(\x)
STORE x6, 6 * REGBYTES(\x)
STORE x7, 7 * REGBYTES(\x)
@@ -66,7 +348,7 @@
/**
* @brife 压栈csr寄存器(CSR_MSTATUS CSR_MEPC CSR_MSUBM CSR_MCAUSE)
* @brief 压栈csr寄存器（CSR_MSTATUS、CSR_MEPC、CSR_MSUBM、CSR_MCAUSE）
* @param x 目标sp寄存器
*/
.macro portSAVE_CONTEXT_EXCP x
@@ -82,7 +364,109 @@
/**
* @brife 压栈浮点寄存器
* @brief 压栈浮点寄存器
* @param x 目标sp寄存器
*/
.macro popVFPREGFILE x
flw f0, 36 * REGBYTES(\x)
flw f1, 37 * REGBYTES(\x)
flw f2, 38 * REGBYTES(\x)
flw f3, 39 * REGBYTES(\x)
flw f4, 40 * REGBYTES(\x)
flw f5, 41 * REGBYTES(\x)
flw f6, 42 * REGBYTES(\x)
flw f7, 43 * REGBYTES(\x)
flw f8, 44 * REGBYTES(\x)
flw f9, 45 * REGBYTES(\x)
flw f10,46 * REGBYTES(\x)
flw f11, 47 * REGBYTES(\x)
flw f12, 48 * REGBYTES(\x)
flw f13, 49 * REGBYTES(\x)
flw f14, 50 * REGBYTES(\x)
flw f15, 51 * REGBYTES(\x)
flw f16, 52 * REGBYTES(\x)
flw f17, 53 * REGBYTES(\x)
flw f18, 54 * REGBYTES(\x)
flw f19, 55 * REGBYTES(\x)
flw f20, 56 * REGBYTES(\x)
flw f21, 57 * REGBYTES(\x)
flw f22, 58 * REGBYTES(\x)
flw f23, 59 * REGBYTES(\x)
flw f24, 60 * REGBYTES(\x)
flw f25, 61 * REGBYTES(\x)
flw f26, 62 * REGBYTES(\x)
flw f27, 63 * REGBYTES(\x)
flw f28, 64 * REGBYTES(\x)
flw f29, 65 * REGBYTES(\x)
flw f30, 66 * REGBYTES(\x)
flw f31, 67 * REGBYTES(\x)
.endm
/**
* @brief 出栈通用寄存器
* @param x 目标sp寄存器
*/
.macro popREGFILE x
LOAD x1, 1 * REGBYTES(\x)
#LOAD x2, 2 * REGBYTES(\x)
#LOAD x3, 3 * REGBYTES(\x)
#LOAD x4, 4 * REGBYTES(\x)
LOAD x5, 5 * REGBYTES(\x)
LOAD x6, 6 * REGBYTES(\x)
LOAD x7, 7 * REGBYTES(\x)
LOAD x8, 8 * REGBYTES(\x)
LOAD x9, 9 * REGBYTES(\x)
LOAD x10, 10 * REGBYTES(\x)
LOAD x11, 11 * REGBYTES(\x)
LOAD x12, 12 * REGBYTES(\x)
LOAD x13, 13 * REGBYTES(\x)
LOAD x14, 14 * REGBYTES(\x)
LOAD x15, 15 * REGBYTES(\x)
#ifndef __riscv_32e
LOAD x16, 16 * REGBYTES(\x)
LOAD x17, 17 * REGBYTES(\x)
LOAD x18, 18 * REGBYTES(\x)
LOAD x19, 19 * REGBYTES(\x)
LOAD x20, 20 * REGBYTES(\x)
LOAD x21, 21 * REGBYTES(\x)
LOAD x22, 22 * REGBYTES(\x)
LOAD x23, 23 * REGBYTES(\x)
LOAD x24, 24 * REGBYTES(\x)
LOAD x25, 25 * REGBYTES(\x)
LOAD x26, 26 * REGBYTES(\x)
LOAD x27, 27 * REGBYTES(\x)
LOAD x28, 28 * REGBYTES(\x)
LOAD x29, 29 * REGBYTES(\x)
LOAD x30, 30 * REGBYTES(\x)
LOAD x31, 31 * REGBYTES(\x)
#endif
#ifdef __riscv_flen
addi \x, \x, REGBYTES * 68 //36+32
#else
addi \x, \x, REGBYTES * 36
#endif
.endm
/**
* @brief 出栈csr寄存器（CSR_MSTATUS、CSR_MEPC、CSR_MSUBM、CSR_MCAUSE）
* @param x 目标sp寄存器
*/
.macro portRESTORE_CONTEXT_EXCP x
LOAD t0, 35*REGBYTES(\x)
csrw CSR_MCAUSE, t0
LOAD t0, 34*REGBYTES(\x)
csrw CSR_MSUBM, t0
LOAD t0, 33*REGBYTES(\x)
csrw CSR_MEPC, t0
LOAD t0, 32*REGBYTES(\x)
csrw CSR_MSTATUS, t0
.endm
/**
* @brief 出栈浮点寄存器
* @param x 目标sp寄存器
*/
.macro pushVFPREGFILE x
@@ -122,139 +506,40 @@
/**
* @brife 出栈通用寄存器
* @param x 目标sp寄存器
*/
.macro popREGFILE x
LOAD x1, 1 * REGBYTES(\x)
//LOAD x2, 2 * REGBYTES(\x)
//LOAD x3, 3 * REGBYTES(\x)
//LOAD x4, 4 * REGBYTES(\x)
LOAD x5, 5 * REGBYTES(\x)
LOAD x6, 6 * REGBYTES(\x)
LOAD x7, 7 * REGBYTES(\x)
LOAD x8, 8 * REGBYTES(\x)
LOAD x9, 9 * REGBYTES(\x)
LOAD x10, 10 * REGBYTES(\x)
LOAD x11, 11 * REGBYTES(\x)
LOAD x12, 12 * REGBYTES(\x)
LOAD x13, 13 * REGBYTES(\x)
LOAD x14, 14 * REGBYTES(\x)
LOAD x15, 15 * REGBYTES(\x)
#ifndef __riscv_32e
LOAD x16, 16 * REGBYTES(\x)
LOAD x17, 17 * REGBYTES(\x)
LOAD x18, 18 * REGBYTES(\x)
LOAD x19, 19 * REGBYTES(\x)
LOAD x20, 20 * REGBYTES(\x)
LOAD x21, 21 * REGBYTES(\x)
LOAD x22, 22 * REGBYTES(\x)
LOAD x23, 23 * REGBYTES(\x)
LOAD x24, 24 * REGBYTES(\x)
LOAD x25, 25 * REGBYTES(\x)
LOAD x26, 26 * REGBYTES(\x)
LOAD x27, 27 * REGBYTES(\x)
LOAD x28, 28 * REGBYTES(\x)
LOAD x29, 29 * REGBYTES(\x)
LOAD x30, 30 * REGBYTES(\x)
LOAD x31, 31 * REGBYTES(\x)
#endif
#ifdef __riscv_flen
addi \x, \x, REGBYTES * 68 //36+32
#else
addi \x, \x, REGBYTES * 36
#endif
.endm
/**
* @brife 出栈csr寄存器(CSR_MSTATUS CSR_MEPC CSR_MSUBM CSR_MCAUSE)
* @param x 目标sp寄存器
*/
.macro portRESTORE_CONTEXT_EXCP x
LOAD t0, 35 * REGBYTES(\x)
csrw CSR_MCAUSE, t0
LOAD t0, 34 * REGBYTES(\x)
csrw CSR_MSUBM, t0
LOAD t0, 33 * REGBYTES(\x)
csrw CSR_MEPC, t0
LOAD t0, 32 * REGBYTES(\x)
csrw CSR_MSTATUS, t0
.endm
/**
* @brife 出栈浮点寄存器
* @param x 目标sp寄存器
*/
.macro popVFPREGFILE x
flw f0, 36 * REGBYTES(\x)
flw f1, 37 * REGBYTES(\x)
flw f2, 38 * REGBYTES(\x)
flw f3, 39 * REGBYTES(\x)
flw f4, 40 * REGBYTES(\x)
flw f5, 41 * REGBYTES(\x)
flw f6, 42 * REGBYTES(\x)
flw f7, 43 * REGBYTES(\x)
flw f8, 44 * REGBYTES(\x)
flw f9, 45 * REGBYTES(\x)
flw f10, 46 * REGBYTES(\x)
flw f11, 47 * REGBYTES(\x)
flw f12, 48 * REGBYTES(\x)
flw f13, 49 * REGBYTES(\x)
flw f14, 50 * REGBYTES(\x)
flw f15, 51 * REGBYTES(\x)
flw f16, 52 * REGBYTES(\x)
flw f17, 53 * REGBYTES(\x)
flw f18, 54 * REGBYTES(\x)
flw f19, 55 * REGBYTES(\x)
flw f20, 56 * REGBYTES(\x)
flw f21, 57 * REGBYTES(\x)
flw f22, 58 * REGBYTES(\x)
flw f23, 59 * REGBYTES(\x)
flw f24, 60 * REGBYTES(\x)
flw f25, 61 * REGBYTES(\x)
flw f26, 62 * REGBYTES(\x)
flw f27, 63 * REGBYTES(\x)
flw f28, 64 * REGBYTES(\x)
flw f29, 65 * REGBYTES(\x)
flw f30, 66 * REGBYTES(\x)
flw f31, 67 * REGBYTES(\x)
.endm
/**
* @brife 清理fpu状态寄存器
* @brief 清理fpu状态寄存器
*/
.macro CONFIG_FS_CLEAN
li t0, (0x1 << 13)
csrc mstatus,t0
li t0, (0x1 << 13) //配置FS为clean状态
csrc mstatus, t0
li t0, (0x1 << 14)
csrs mstatus,t0
csrs mstatus, t0
.endm
/* -------------------------------------------------------------------------------------------------------- */
/**
* @brife trap入口函数
* @brief trap入口函数
*/
.global trap_entry
.align 6
.section .text.trap
.align 6// In CLIC mode, the trap entry must be 64bytes aligned
.global trap_entry
.weak trap_entry
trap_entry:
pushREGFILE sp
pushREGFILE sp //trap这里就直接使用当前栈，方便对当前位置进行异常分析，
//同时不担心(任务栈/中断栈/主栈)溢出，因为程序进入这里便不会返回了
portSAVE_CONTEXT_EXCP sp
csrr a0, mcause
mv a1, sp
jal ulSynchTrap
mv sp,a0
mv sp, a0
portRESTORE_CONTEXT_EXCP sp
popREGFILE sp
mret
/* -------------------------------------------------------------------------------------------------------- */
/**
* @brife trq入口函数
@@ -434,3 +719,12 @@ xPortStartScheduler:
*/
vPortEndScheduler:
j vPortEndScheduler
/* Default Handler for Exceptions / Interrupts */
.global default_intexc_handler
.weak default_intexc_handler
Undef_Handler:
default_intexc_handler:
1:
j 1b

35
workspace/TS100/Core/BSP/Pine64/Vendor/Lib/intexc_gd32vf103.S vendored
View File

@@ -1,35 +0,0 @@
/*
* Copyright (c) 2019 Nuclei Limited. All rights reserved.
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the License); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/******************************************************************************
* \file intexc_gd32vf103.S
* \brief NMSIS Interrupt and Exception Handling Template File
* for Device gd32vf103
* \version V1.00
* \date 7 Jan 2020
*
******************************************************************************/
#include "riscv_encoding.h"
/* Default Handler for Exceptions / Interrupts */
.global default_intexc_handler
.weak default_intexc_handler
Undef_Handler:
default_intexc_handler:
1:
j 1b

291
workspace/TS100/Core/BSP/Pine64/Vendor/RISCV/entry.S vendored
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@@ -1,291 +0,0 @@
#include "riscv_encoding.h"
#include "riscv_bits.h"
#include "n200_eclic.h"
#include "n200_timer.h"
#define USE_MSP 1 //启用中断栈
/**
* @brief 压栈通用寄存器
* @param x 目标sp寄存器
*/
.macro pushREGFILE x
#ifdef __riscv_flen
addi \x, \x, -REGBYTES * 68 //36+32
#else
addi \x, \x, -REGBYTES * 36
#endif
STORE x1, 1 * REGBYTES(\x)
STORE x2, 2 * REGBYTES(\x)
#STORE x3, 3 * REGBYTES(\x)
#STORE x4, 4 * REGBYTES(\x)
STORE x5, 5 * REGBYTES(\x)
STORE x6, 6 * REGBYTES(\x)
STORE x7, 7 * REGBYTES(\x)
STORE x8, 8 * REGBYTES(\x)
STORE x9, 9 * REGBYTES(\x)
STORE x10, 10 * REGBYTES(\x)
STORE x11, 11 * REGBYTES(\x)
STORE x12, 12 * REGBYTES(\x)
STORE x13, 13 * REGBYTES(\x)
STORE x14, 14 * REGBYTES(\x)
STORE x15, 15 * REGBYTES(\x)
#ifndef __riscv_32e
STORE x16, 16 * REGBYTES(\x)
STORE x17, 17 * REGBYTES(\x)
STORE x18, 18 * REGBYTES(\x)
STORE x19, 19 * REGBYTES(\x)
STORE x20, 20 * REGBYTES(\x)
STORE x21, 21 * REGBYTES(\x)
STORE x22, 22 * REGBYTES(\x)
STORE x23, 23 * REGBYTES(\x)
STORE x24, 24 * REGBYTES(\x)
STORE x25, 25 * REGBYTES(\x)
STORE x26, 26 * REGBYTES(\x)
STORE x27, 27 * REGBYTES(\x)
STORE x28, 28 * REGBYTES(\x)
STORE x29, 29 * REGBYTES(\x)
STORE x30, 30 * REGBYTES(\x)
STORE x31, 31 * REGBYTES(\x)
#endif
.endm
/**
* @brief 压栈csr寄存器（CSR_MSTATUS、CSR_MEPC、CSR_MSUBM、CSR_MCAUSE）
* @param x 目标sp寄存器
*/
.macro portSAVE_CONTEXT_EXCP x
csrr t0, CSR_MSTATUS
STORE t0, 32 * REGBYTES(\x)
csrr t0, CSR_MEPC
STORE t0, 33 * REGBYTES(\x)
csrr t0, CSR_MSUBM
STORE t0, 34 * REGBYTES(\x)
csrr t0, CSR_MCAUSE
STORE t0, 35 * REGBYTES(\x)
.endm
/**
* @brief 压栈浮点寄存器
* @param x 目标sp寄存器
*/
.macro popVFPREGFILE x
flw f0, 36 * REGBYTES(\x)
flw f1, 37 * REGBYTES(\x)
flw f2, 38 * REGBYTES(\x)
flw f3, 39 * REGBYTES(\x)
flw f4, 40 * REGBYTES(\x)
flw f5, 41 * REGBYTES(\x)
flw f6, 42 * REGBYTES(\x)
flw f7, 43 * REGBYTES(\x)
flw f8, 44 * REGBYTES(\x)
flw f9, 45 * REGBYTES(\x)
flw f10,46 * REGBYTES(\x)
flw f11, 47 * REGBYTES(\x)
flw f12, 48 * REGBYTES(\x)
flw f13, 49 * REGBYTES(\x)
flw f14, 50 * REGBYTES(\x)
flw f15, 51 * REGBYTES(\x)
flw f16, 52 * REGBYTES(\x)
flw f17, 53 * REGBYTES(\x)
flw f18, 54 * REGBYTES(\x)
flw f19, 55 * REGBYTES(\x)
flw f20, 56 * REGBYTES(\x)
flw f21, 57 * REGBYTES(\x)
flw f22, 58 * REGBYTES(\x)
flw f23, 59 * REGBYTES(\x)
flw f24, 60 * REGBYTES(\x)
flw f25, 61 * REGBYTES(\x)
flw f26, 62 * REGBYTES(\x)
flw f27, 63 * REGBYTES(\x)
flw f28, 64 * REGBYTES(\x)
flw f29, 65 * REGBYTES(\x)
flw f30, 66 * REGBYTES(\x)
flw f31, 67 * REGBYTES(\x)
.endm
/**
* @brief 出栈通用寄存器
* @param x 目标sp寄存器
*/
.macro popREGFILE x
LOAD x1, 1 * REGBYTES(\x)
#LOAD x2, 2 * REGBYTES(\x)
#LOAD x3, 3 * REGBYTES(\x)
#LOAD x4, 4 * REGBYTES(\x)
LOAD x5, 5 * REGBYTES(\x)
LOAD x6, 6 * REGBYTES(\x)
LOAD x7, 7 * REGBYTES(\x)
LOAD x8, 8 * REGBYTES(\x)
LOAD x9, 9 * REGBYTES(\x)
LOAD x10, 10 * REGBYTES(\x)
LOAD x11, 11 * REGBYTES(\x)
LOAD x12, 12 * REGBYTES(\x)
LOAD x13, 13 * REGBYTES(\x)
LOAD x14, 14 * REGBYTES(\x)
LOAD x15, 15 * REGBYTES(\x)
#ifndef __riscv_32e
LOAD x16, 16 * REGBYTES(\x)
LOAD x17, 17 * REGBYTES(\x)
LOAD x18, 18 * REGBYTES(\x)
LOAD x19, 19 * REGBYTES(\x)
LOAD x20, 20 * REGBYTES(\x)
LOAD x21, 21 * REGBYTES(\x)
LOAD x22, 22 * REGBYTES(\x)
LOAD x23, 23 * REGBYTES(\x)
LOAD x24, 24 * REGBYTES(\x)
LOAD x25, 25 * REGBYTES(\x)
LOAD x26, 26 * REGBYTES(\x)
LOAD x27, 27 * REGBYTES(\x)
LOAD x28, 28 * REGBYTES(\x)
LOAD x29, 29 * REGBYTES(\x)
LOAD x30, 30 * REGBYTES(\x)
LOAD x31, 31 * REGBYTES(\x)
#endif
#ifdef __riscv_flen
addi \x, \x, REGBYTES * 68 //36+32
#else
addi \x, \x, REGBYTES * 36
#endif
.endm
/**
* @brief 出栈csr寄存器（CSR_MSTATUS、CSR_MEPC、CSR_MSUBM、CSR_MCAUSE）
* @param x 目标sp寄存器
*/
.macro portRESTORE_CONTEXT_EXCP x
LOAD t0, 35*REGBYTES(\x)
csrw CSR_MCAUSE, t0
LOAD t0, 34*REGBYTES(\x)
csrw CSR_MSUBM, t0
LOAD t0, 33*REGBYTES(\x)
csrw CSR_MEPC, t0
LOAD t0, 32*REGBYTES(\x)
csrw CSR_MSTATUS, t0
.endm
/**
* @brief 出栈浮点寄存器
* @param x 目标sp寄存器
*/
.macro pushVFPREGFILE x
fsw f0, 36 * REGBYTES(\x)
fsw f1, 37 * REGBYTES(\x)
fsw f2, 38 * REGBYTES(\x)
fsw f3, 39 * REGBYTES(\x)
fsw f4, 40 * REGBYTES(\x)
fsw f5, 41 * REGBYTES(\x)
fsw f6, 42 * REGBYTES(\x)
fsw f7, 43 * REGBYTES(\x)
fsw f8, 44 * REGBYTES(\x)
fsw f9, 45 * REGBYTES(\x)
fsw f10, 46 * REGBYTES(\x)
fsw f11, 47 * REGBYTES(\x)
fsw f12, 48 * REGBYTES(\x)
fsw f13, 49 * REGBYTES(\x)
fsw f14, 50 * REGBYTES(\x)
fsw f15, 51 * REGBYTES(\x)
fsw f16, 52 * REGBYTES(\x)
fsw f17, 53 * REGBYTES(\x)
fsw f18, 54 * REGBYTES(\x)
fsw f19, 55 * REGBYTES(\x)
fsw f20, 56 * REGBYTES(\x)
fsw f21, 57 * REGBYTES(\x)
fsw f22, 58 * REGBYTES(\x)
fsw f23, 59 * REGBYTES(\x)
fsw f24, 60 * REGBYTES(\x)
fsw f25, 61 * REGBYTES(\x)
fsw f26, 62 * REGBYTES(\x)
fsw f27, 63 * REGBYTES(\x)
fsw f28, 64 * REGBYTES(\x)
fsw f29, 65 * REGBYTES(\x)
fsw f30, 66 * REGBYTES(\x)
fsw f31, 67 * REGBYTES(\x)
.endm
/**
* @brief 清理fpu状态寄存器
*/
.macro CONFIG_FS_CLEAN
li t0, (0x1 << 13) //配置FS为clean状态
csrc mstatus, t0
li t0, (0x1 << 14)
csrs mstatus, t0
.endm
/* -------------------------------------------------------------------------------------------------------- */
/**
* @brief trap入口函数
*/
.section .text.trap
.align 6// In CLIC mode, the trap entry must be 64bytes aligned
.global trap_entry
.weak trap_entry
trap_entry:
pushREGFILE sp //trap这里就直接使用当前栈，方便对当前位置进行异常分析，
//同时不担心(任务栈/中断栈/主栈)溢出，因为程序进入这里便不会返回了
portSAVE_CONTEXT_EXCP sp
csrr a0, mcause
mv a1, sp
jal ulSynchTrap
mv sp, a0
portRESTORE_CONTEXT_EXCP sp
popREGFILE sp
mret
/* -------------------------------------------------------------------------------------------------------- */
/**
* @brief irq入口函数
*/
.section .text.irq
.align 2
.global irq_entry
.weak irq_entry
irq_entry:
#if USE_MSP
csrrw sp, CSR_MSCRATCHCSWL, sp
#endif
pushREGFILE sp //保存通用寄存器
portSAVE_CONTEXT_EXCP sp
#ifdef __riscv_flen
csrr t2, mstatus
li t0, (0x3 << 13)
and t1, t2, t0
bne t1, t0, 1f //浮点寄存器状态为Dirty状态，则保存浮点寄存器, 否则不用保存
pushVFPREGFILE sp
1:
CONFIG_FS_CLEAN
#endif
csrrw ra, CSR_JALMNXTI, ra //跳转到中断向量表入口地址，中断处理返回时继续回到此处
csrc CSR_MSTATUS, MSTATUS_MIE //此时中断处理完毕，中断关闭，注意mret退出中断时将恢复从mpie恢复mie，
//因此在中断内部修改mie仅会保持中断mret前，退出中断将恢复为进中断前状态
#ifdef __riscv_flen
csrr t2, mstatus
li t0, (0x3 << 13)
and t1, t2, t0
bne t1, t0, 2f //浮点寄存器状态为Dirty状态，则恢复浮点寄存器, 否则不用恢复
popVFPREGFILE sp
2:
#endif
portRESTORE_CONTEXT_EXCP sp
#ifdef __riscv_flen
CONFIG_FS_CLEAN
#endif
popREGFILE sp
#if USE_MSP
csrrw sp, CSR_MSCRATCHCSWL, sp
#endif
mret

289
workspace/TS100/Core/BSP/Pine64/Vendor/RISCV/start.S vendored
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@@ -1,289 +0,0 @@
// See LICENSE for license details.
#include "riscv_encoding.h"
.section .init
.weak eclic_msip_handler //弱定义函数，这些在编译为bin后可以看到将全部为0
.weak eclic_mtip_handler
.weak eclic_bwei_handler
.weak eclic_pmovi_handler
.weak WWDGT_IRQHandler
.weak LVD_IRQHandler
.weak TAMPER_IRQHandler
.weak RTC_IRQHandler
.weak FMC_IRQHandler
.weak RCU_IRQHandler
.weak EXTI0_IRQHandler
.weak EXTI1_IRQHandler
.weak EXTI2_IRQHandler
.weak EXTI3_IRQHandler
.weak EXTI4_IRQHandler
.weak DMA0_Channel0_IRQHandler
.weak DMA0_Channel1_IRQHandler
.weak DMA0_Channel2_IRQHandler
.weak DMA0_Channel3_IRQHandler
.weak DMA0_Channel4_IRQHandler
.weak DMA0_Channel5_IRQHandler
.weak DMA0_Channel6_IRQHandler
.weak ADC0_1_IRQHandler
.weak CAN0_TX_IRQHandler
.weak CAN0_RX0_IRQHandler
.weak CAN0_RX1_IRQHandler
.weak CAN0_EWMC_IRQHandler
.weak EXTI5_9_IRQHandler
.weak TIMER0_BRK_IRQHandler
.weak TIMER0_UP_IRQHandler
.weak TIMER0_TRG_CMT_IRQHandler
.weak TIMER0_Channel_IRQHandler
.weak TIMER1_IRQHandler
.weak TIMER2_IRQHandler
.weak TIMER3_IRQHandler
.weak I2C0_EV_IRQHandler
.weak I2C0_ER_IRQHandler
.weak I2C1_EV_IRQHandler
.weak I2C1_ER_IRQHandler
.weak SPI0_IRQHandler
.weak SPI1_IRQHandler
.weak USART0_IRQHandler
.weak USART1_IRQHandler
.weak USART2_IRQHandler
.weak EXTI10_15_IRQHandler
.weak RTC_Alarm_IRQHandler
.weak USBFS_WKUP_IRQHandler
.weak EXMC_IRQHandler
.weak TIMER4_IRQHandler
.weak SPI2_IRQHandler
.weak UART3_IRQHandler
.weak UART4_IRQHandler
.weak TIMER5_IRQHandler
.weak TIMER6_IRQHandler
.weak DMA1_Channel0_IRQHandler
.weak DMA1_Channel1_IRQHandler
.weak DMA1_Channel2_IRQHandler
.weak DMA1_Channel3_IRQHandler
.weak DMA1_Channel4_IRQHandler
.weak CAN1_TX_IRQHandler
.weak CAN1_RX0_IRQHandler
.weak CAN1_RX1_IRQHandler
.weak CAN1_EWMC_IRQHandler
.weak USBFS_IRQHandler
vector_base: //中断向量表
j _start //第一条指令即跳转到_start处开始执行
.align 2
.word 0
.word 0
.word eclic_msip_handler
.word 0
.word 0
.word 0
.word eclic_mtip_handler
.word 0
.word 0
.word 0
.word 0
.word 0
.word 0
.word 0
.word 0
.word 0
.word eclic_bwei_handler
.word eclic_pmovi_handler
.word WWDGT_IRQHandler
.word LVD_IRQHandler
.word TAMPER_IRQHandler
.word RTC_IRQHandler
.word FMC_IRQHandler
.word RCU_IRQHandler
.word EXTI0_IRQHandler
.word EXTI1_IRQHandler
.word EXTI2_IRQHandler
.word EXTI3_IRQHandler
.word EXTI4_IRQHandler
.word DMA0_Channel0_IRQHandler
.word DMA0_Channel1_IRQHandler
.word DMA0_Channel2_IRQHandler
.word DMA0_Channel3_IRQHandler
.word DMA0_Channel4_IRQHandler
.word DMA0_Channel5_IRQHandler
.word DMA0_Channel6_IRQHandler
.word ADC0_1_IRQHandler
.word CAN0_TX_IRQHandler
.word CAN0_RX0_IRQHandler
.word CAN0_RX1_IRQHandler
.word CAN0_EWMC_IRQHandler
.word EXTI5_9_IRQHandler
.word TIMER0_BRK_IRQHandler
.word TIMER0_UP_IRQHandler
.word TIMER0_TRG_CMT_IRQHandler
.word TIMER0_Channel_IRQHandler
.word TIMER1_IRQHandler
.word TIMER2_IRQHandler
.word TIMER3_IRQHandler
.word I2C0_EV_IRQHandler
.word I2C0_ER_IRQHandler
.word I2C1_EV_IRQHandler
.word I2C1_ER_IRQHandler
.word SPI0_IRQHandler
.word SPI1_IRQHandler
.word USART0_IRQHandler
.word USART1_IRQHandler
.word USART2_IRQHandler
.word EXTI10_15_IRQHandler
.word RTC_Alarm_IRQHandler
.word USBFS_WKUP_IRQHandler
.word 0
.word 0
.word 0
.word 0
.word 0
.word EXMC_IRQHandler
.word 0
.word TIMER4_IRQHandler
.word SPI2_IRQHandler
.word UART3_IRQHandler
.word UART4_IRQHandler
.word TIMER5_IRQHandler
.word TIMER6_IRQHandler
.word DMA1_Channel0_IRQHandler
.word DMA1_Channel1_IRQHandler
.word DMA1_Channel2_IRQHandler
.word DMA1_Channel3_IRQHandler
.word DMA1_Channel4_IRQHandler
.word 0
.word 0
.word CAN1_TX_IRQHandler
.word CAN1_RX0_IRQHandler
.word CAN1_RX1_IRQHandler
.word CAN1_EWMC_IRQHandler
.word USBFS_IRQHandler
.globl _start
.type _start,@function
_start:
csrc CSR_MSTATUS, MSTATUS_MIE //CSR_MSTATUS &= ~0x8 mstatus[3]:0屏蔽全部中断 1不屏蔽全部中断 （当然这里全部中断是除过不可屏蔽中断）
/* Jump to logical address first to ensure correct operation of RAM region */
la a0, _start //a0 = _start
li a1, 1 //a1 = 1
slli a1, a1, 29 //a1 = 0x20000000 raw起始地址
bleu a1, a0, _start0800 //if( a1 <= a0 ) JUMP _start0800
srli a1, a1, 2 //a1 = 0x08000000 flash起始地址
bleu a1, a0, _start0800 //if( a1 <= a0 ) JUMP _start0800
la a0, _start0800 //a0 = _start0800
add a0, a0, a1 //a0 = a0+a1
jr a0 //JUMP a0
_start0800:
/* Set the the NMI base to share with mtvec by setting CSR_MMISC_CTL */
li t0, 0x200 //t0 = 0x200
csrs CSR_MMISC_CTL, t0 //mmisc_ctl |= 0x200 CSR_MMISC_CTL[9]：设置NMI的地址与mtvec相同且，mcause.EXCCODE = 0xfff
//cs开头的指令是特有的用来操作内核寄存器的的指令，内核寄存器是一组特有的12位地址
/* Intial the mtvt*/
la t0, vector_base //t0 = vector_base 向量表地址
csrw CSR_MTVT, t0 //mtvt = vector_base 中断向量表基地址
/* Intial the mtvt2 and enable it*/
la t0, irq_entry //t0 = irq_entry irq_entry定义在entry.S,有freertos操作系统情况下定义在portasm.S
csrw CSR_MTVT2, t0 //mtvt2 = irq_entry mtvt2[31:2]: 中断入口函数地址
csrs CSR_MTVT2, 0x1 //mtvt2 |= 0x1 mtvt2[0]: 1配置mtvt2的配置有效，配0则为mtvec内地址
/* Intial the CSR MTVEC for the Trap ane NMI base addr*/
la t0, trap_entry //t0 = trap_entry trap_entry定义在entry.S,有freertos操作系统情况下定义在portasm.S
csrw CSR_MTVEC, t0 //mtvec = trap_entry mtvec[31:6]：异常入口地址
// mtvec[5:0]：0B00011 -- ECLIC中断模式 其他：默认模式
// 这里配置为默认模式
// trap_entry基本上可以理解为arm里的hard/mem/use/svc等fault了，
// 这里在移植freertos时就使用了 ecall 进入trap_entry里 相当于arm里的PendSVC
/* OS启动前配置中断栈为FHEAP的end地址 */
la t0, ucHeap
csrw CSR_MSCRATCH, t0
#ifdef __riscv_flen //浮点宏
/* Enable FPU */
li t0, MSTATUS_FS //t0 = 0x6000
csrs mstatus, t0 //mstatus |= 0x6000 mstatus[14:13]:非零值启用浮点单元，配置为1或2会在第一次使用浮点单元时变为3，这里直接配置为3
csrw fcsr, x0 //fcsr = x0 = 0 ??这里x0是否指的是zero通用寄存器值? 这个寄存器0-4位是浮点异常状态标志，5-7位是浮点舍入模式配置
#endif
.option push
.option norelax
la gp, __global_pointer$ //__global_pointer$定义在link连接脚本内，指向所有.data段后偏移0x800的地址,0x800为2K，其值源于下文解释
//gp 意为global pointer （全局指针）寄存器是一个解决方案，
//为了以进一步优化存储器访问单个4KB区域内。
//链接器使用__global_pointer$符号定义来比较内存地址，如果在范围内，
//则它将绝对/相对pc寻址替换为gp相对寻址，从而使代码更有效。这个过程通过-Wl,--no-relax选项使用。
//这里.option norelax起到-Wl,--no-relax作用，就不需要在编译选项添加了
//上文参考自：https://gnu-mcu-eclipse.github.io/arch/riscv/programmer/#the-gp-global-pointer-register
//要让 relaxing 优化起作用，编译时要加入 -msmall-data-limit=n 参数，有了这个参数，
//编译器会把内存空间小于 n 字节的静态变量放入 .sdata 或者 .sdata.* 节，
//然后链接器将这部分静态变量集中在 __global_pointer$ +/- 2K 的范围内。
//上文参考自：https://blog.csdn.net/zoomdy/article/details/100703451
.option pop
la sp, _sp //sp = 主栈栈顶地址 _sp定义在link连接脚本内
/* Load data section */
la a0, _data_lma //a0 = data的Load Memory Address _data_lma定义在link连接脚本内
la a1, _data //a1 = data的Run Memory Address _data定义在link连接脚本内
la a2, _edata //a2 = data的Run Memory Address结束地址 _edata定义在link连接脚本内
bgeu a1, a2, 2f //if( a1 >= a2 ) JUMP 2f 原则上不会出现_data地址大于_edata地址
//如果出现了则直接跳转到 2f 即下一个2标签
1:
lw t0, (a0) //t0 = _data_lma
sw t0, (a1) //*_data = t0 即 *_data_lma，按word写入
addi a0, a0, 4 //a0 = a0 + 4 下一个ward
addi a1, a1, 4 //a1 = a1 + 4
bltu a1, a2, 1b //if( a1 < a2 ) JUMP 1b 如果未到达_edata则跳转到 1b 即上一个1标签，这里会完成一个循环
2:
/* Clear bss section */
la a0, __bss_start //a0 = __bss_start 初值为0的全局变量段起始地址 __bss_start定义在link连接脚本内
la a1, _end //a1 = _end 初值为0的全局变量段结束地址 _end定义在link连接脚本内
bgeu a0, a1, 2f //if( a0 >= a1 ) JUMP 2f 原则上不会出现__bss_start地址大于_end地址
//如果出现了则直接跳转到 2f 即下一个2标签
1:
sw zero, (a0) //*__bss_start = zero = 0 bss段清除为0
addi a0, a0, 4 //a0 = a0 + 4 下一个ward
bltu a0, a1, 1b //if( a0 < a1 ) JUMP 1b 如果未到达_end则跳转到 1b 即上一个1标签，这里会完成一个循环
//程序执行到这里全局变量就以及处理完毕了
2:
/*enable mcycle_minstret*/
csrci CSR_MCOUNTINHIBIT, 0x5 //CSR_MCOUNTINHIBIT &= ~0x5 这里清零了第0bit和第1bit，使能了mcycle计数和minstret计数
//csrci这条指令处理立即数5bit，列如0x5只是0B00101，高位不处理
/*
* Call vendor defined SystemInit to
* initialize the micro-controller system
*/
call SystemInit
/* Call global constructors */
la a0, __libc_fini_array //a0 = __libc_fini_array newlib中atexit函数的参数
call atexit //调用newlib中的 void atexit(void (*func)(void)) 函数
//功能为注册main函数结束后调用的函数，这里是__libc_fini_array
call __libc_init_array //调用newlib中的 void __libc_init_array (void) 函数
//这里要注意__libc_init_array函数会调用_init的钩子函数，用来做c环境初始化前的一些硬件初始化
//列如时钟的配置等，这里_init定义在init.c
//程序执行到这里C/C++环境就初始化完成了，可以进入main函数入口了
/* argc = argv = 0 */
li a0, 0 //a0 = 0 main函数参数argc = 0
li a1, 0 //a1 = 0 main函数参数argv = 0
call main //调用 int main(int argc,char **argv) 函数
tail exit //main返回后调用newlib的exit函数, tail指令应该是不会返回的调用函数了
1:
j 1b //1b 即上一次1标签，即跳转到自己，程序到这里就死循环了，原则不会运行到这里
.global disable_mcycle_minstret
disable_mcycle_minstret:
csrsi CSR_MCOUNTINHIBIT, 0x5 //关闭了mcycle计数和minstret计数
ret
.global enable_mcycle_minstret
enable_mcycle_minstret:
csrci CSR_MCOUNTINHIBIT, 0x5 //使能了mcycle计数和minstret计数
ret