铜川网站建设电话,加强网站建设和信息公开,赣州人才网最新招聘,网站的seo1、sbi_ecall函数功能 #xff08;1#xff09;sbi_ecall函数是内核调用SBI的接口#xff0c;在RISC-V架构中定义了SBI规范#xff0c;内核通过ecall指令来调用SBI接口进而操作硬件#xff1b; #xff08;2#xff09;SBI规范参考官网文档《riscv-sbi.pdf》#xff1b…1、sbi_ecall函数功能 1sbi_ecall函数是内核调用SBI的接口在RISC-V架构中定义了SBI规范内核通过ecall指令来调用SBI接口进而操作硬件 2SBI规范参考官网文档《riscv-sbi.pdf》 2、sbi_ecall函数源码
struct sbiret
{long error;long value;
};//ext对应SBI规范的拓展EIDfid对应SBI规范的功能FIDarg0-arg5是传参
struct sbiret sbi_ecall(int ext, int fid, unsigned long arg0,unsigned long arg1, unsigned long arg2,unsigned long arg3, unsigned long arg4,unsigned long arg5)
{struct sbiret ret;register uintptr_t a0 asm (a0) (uintptr_t)(arg0);register uintptr_t a1 asm (a1) (uintptr_t)(arg1);register uintptr_t a2 asm (a2) (uintptr_t)(arg2);register uintptr_t a3 asm (a3) (uintptr_t)(arg3);register uintptr_t a4 asm (a4) (uintptr_t)(arg4);register uintptr_t a5 asm (a5) (uintptr_t)(arg5);register uintptr_t a6 asm (a6) (uintptr_t)(fid);register uintptr_t a7 asm (a7) (uintptr_t)(ext);asm volatile (ecall: r (a0), r (a1): r (a2), r (a3), r (a4), r (a5), r (a6), r (a7): memory);ret.error a0;ret.value a1;return ret;
}函数代码摘抄自内核源码arch/riscv/kernel/sbi.c 3、ecall指令传参分析 1ecall通过寄存器a0-a7传递参数其中a6传递功能IDa7传递拓展ID 2其中a0和a1不仅做传入参数还需要做传出参数a0传递错误码a1传递返回值 补充要看懂需要了解内嵌汇编参考博客《RISC-V架构学习——C语言内嵌汇编总结》 4、调用ecall指令后跳转执行什么代码 1在S模式或者U模式调用ecall指令会陷入到M模式执行M模式的异常处理函数异常处理函数的地址在启动阶段需要设置到mtvec寄存器中硬件会自动跳转 2要明白上述的代码需要了解RISC-V的不同模式下的寄存器、中断机制、SBI规范
