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Chen Wang
312f9dbc08
libcpu/risc-v/common64/mmu.c uses the external symbol "__bss_end" (this symbol generally is defined in the link script file) and depends on the extern declaration of this symbol in the bsp's "board.h". This is not a problem in implementation, but it is not a good habit. If this extern symbol is used locally, just declare it locally should be better. In this way, there will be no dependency of the kernel core on the bsp header file. And there will be no special requirements for the bsp board code, such as the need to make extern declarations for these "__bss_end" symbols in "board.h". This patch currently only explicitly externly declares "__bss_end" inside libcpu itself. The code of "#include <board.h>" is kept, because the modification involved is too large, it is necessary to clean up the bsp involved before cleaning this include code line uniformly. Signed-off-by: Chen Wang <unicorn_wang@outlook.com>
RT-Thread RV64支持
1.概述
该目录提供RT-Thread标准版及SMART版本对rv64体系结构支持，其中包括：
| 文件名 | 文件内容 | 参考标准 |
|---|---|---|
| atomic_rv64.c | 原子操作实现接口 | "A" Extension for Atomic Instructions, Version 2.1 |
| context_gcc.S | 线程上下文切换 | The RISC-V Instruction Set Manual Volume II: privileged supervisor-level ISA version 1.12 |
| cpuport_gcc.S | 线程统一入口 | |
| cpuport.c | 线程栈初始化 | |
| cpuport.h | 通用寄存器、浮点、向量寄存器个数定义，内存屏障接口 | The RISC-V Instruction Set Manual Volume II: privileged supervisor-level ISA version 1.12 |
| interrupt_gcc.S | 异常/中断处理、全局中断使能/关闭 | The RISC-V Instruction Set Manual Volume II: privileged supervisor-level ISA version 1.12 |
| io.h | 以字节、字、双字读、写IO地址接口 | |
| encoding.h | CSR寄存器定义 | The RISC-V Instruction Set Manual Volume II: privileged supervisor-level ISA version 1.12 |
| vector_encoding.h | vector相关指令定义 | RISC-V "V" Standard Extension for Vector Operations, Version 1.0 |
| ext_context.h | 浮点/向量上下文保存与恢复 | RISC-V "V" Standard Extension for Vector Operations, Version 1.0 "F" Extension for Single-Precision Floating-Point Version 2.2 |
| mmu.c | rv64 sv39 mmu管理接口 | The RISC-V Instruction Set Manual Volume II: privileged supervisor-level ISA version 1.12 |
| mmu.h | rv64 sv39 mmu页表相关定义 | The RISC-V Instruction Set Manual Volume II: privileged supervisor-level ISA version 1.12 |
| asid.c | rv64 mmu asid支持 | The RISC-V Instruction Set Manual Volume II: privileged supervisor-level ISA version 1.12 |
| riscv_mmu.c | 使能/关闭S态访问用户态页表 | The RISC-V Instruction Set Manual Volume II: privileged supervisor-level ISA version 1.12 |
| sbi.c | 通过ecall调用SBI相关信息接口 | RISC-V Supervisor Binary Interface Specification Version 1.0 |
| sbi.h | SBI spec相关接口定义 | RISC-V Supervisor Binary Interface Specification Version 1.0 |
| stack.h | 线程栈数据定义 | The RISC-V Instruction Set Manual Volume II: privileged supervisor-level ISA version 1.12 |
| stackframe.h | 线程上下文保存/恢复 | The RISC-V Instruction Set Manual Volume II: privileged supervisor-level ISA version 1.12 |
| syscall_c.c | 系统调用处理 | |
| tick.c | S态时钟初始化及中断处理 | |
| tlb.h | tlb刷新/无效接口 | The RISC-V Instruction Set Manual Volume II: privileged supervisor-level ISA version 1.12 |
| trap.c | 异常/中断处理，包括中断分发及用户态异常处理 | The RISC-V Instruction Set Manual Volume II: privileged supervisor-level ISA version 1.12 |
2.运行模式配置
| 选项 | 默认值 | 说明 |
|---|---|---|
| RISCV_VIRT64_S_MODE | 打开 | 系统启动后是否运行在S态，关闭时系统将运行在M态；目前系统存在bug尚不可直接运行在M态，故此开关必须打开 |
| RT_USING_SMART | 关闭 | 是否开启RTThread SMART版本，开启后系统运行在S+U态，且会开启MMU页表(satp);关闭时系统仅运行在S态，MMU关闭(satp为bare translation) |
| ARCH_USING_ASID | 关闭 | MMU是否支持asid |
3.移植指南
（1）增加新的CPU支持
创建libcpu/risc-v/<VENDOR_NAME>/<CPU_NAME>新目录，同时在libcpu/risc-v/SConscript中增加该CPU。
（2）PLIC中断控制器支持
libcpu/risc-v/virt64/plic.[c|h]提供了符合《RISC-V Platform-Level Interrupt Controller Specification version 1.0.0 》标准的PLIC中断控制器驱动代码，可作为移植参考。
（3）串口uart支持
目前串口驱动在各bsp目录下，可参考bsp/qemu-virt64-riscv/driver/drv_uart.[c|h]