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1 change: 0 additions & 1 deletion .benos.cmd
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1 change: 0 additions & 1 deletion .benos.strip.cmd
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18 changes: 0 additions & 18 deletions .config
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9 changes: 5 additions & 4 deletions Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -34,18 +34,16 @@ $(BUILD_DIR)/asm-offsets.s : src/asm-offsets.c
mkdir -p $(@D)
gcc -Iinclude -S $< -o $@

$(offsets-file) : $(BUILD_DIR)/asm-offsets.s
@$(cmd_offsets)

all : rpios.bin

clean :
rm -rf $(BUILD_DIR) *.img
run :
qemu-system-aarch64 -machine raspi3 -nographic -kernel rpios.img
qemu-system-aarch64 -machine raspi3 -nographic -kernel rpios.img -serial mon:stdio

debug :
qemu-system-aarch64 -machine raspi3 -nographic -kernel rpios.img -S -s
qemu-system-aarch64 -machine raspi3 -nographic -kernel rpios.img -S -s

$(BUILD_DIR)/%_c.o: $(SRC_DIR)/%.c
mkdir -p $(@D)
Expand All @@ -54,6 +52,9 @@ $(BUILD_DIR)/%_c.o: $(SRC_DIR)/%.c
$(BUILD_DIR)/%_s.o: $(SRC_DIR)/%.S
$(ARMGNU)-gcc $(ASMOPS) -MMD -c $< -o $@

$(offsets-file) : $(BUILD_DIR)/asm-offsets.s
@$(cmd_offsets)

C_FILES = $(filter-out $(SRC_DIR)/asm-offsets.c, $(wildcard $(SRC_DIR)/*.c))

ASM_FILES = $(wildcard $(SRC_DIR)/*.S)
Expand Down
24 changes: 24 additions & 0 deletions README.md
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@@ -0,0 +1,24 @@
### 从零开始学操作系统
基于`qemu` 来模拟`rpi3b+` 硬件平台, 从零开始开发内核. 通过实践来学习`操作系统` 和 `ARMv8`架构.




#### [1. 系统启动, 串口打印.](https://github.com/cuijier/learn_kernel/blob/v1/doc/rpi3b%20qemu%20%E4%B9%8B%E5%90%AF%E5%8A%A8_01.md)

#### [2. 系统异常,中断实现.](https://github.com/cuijier/learn_kernel/blob/v1/doc/rpi3b%20qemu%20%E4%B9%8B%E5%BC%82%E5%B8%B8_02.md)

#### [3. 进程管理,进程调度.](https://github.com/cuijier/learn_kernel/blob/v1/doc/rpi3b%20qemu%20%E4%B9%8B%E8%BF%9B%E7%A8%8B%E8%B0%83%E5%BA%A6_03.md)

#### [4. 用户进程,系统调用.](https://github.com/cuijier/learn_kernel/blob/v1/doc/rpi3b%20qemu%20%E4%B9%8B%E7%94%A8%E6%88%B7%E8%BF%9B%E7%A8%8B%E5%92%8C%E7%B3%BB%E7%BB%9F%E8%B0%83%E7%94%A8_04.md)

#### [5. 虚拟内存管理](https://github.com/cuijier/learn_kernel/blob/v1/doc/rpi3b%20qemu%20%E4%B9%8B%E8%99%9A%E6%8B%9F%E5%86%85%E5%AD%98%E7%AE%A1%E7%90%86_05.md)



#### 相关文档
[ARM® Architecture Reference Manual
](https://github.com/cuijier/learn_kernel/blob/v1/doc/DDI0487C_a_armv8_arm.pdf)

[BCM2837-ARM-Peripherals](https://github.com/cuijier/learn_kernel/blob/v1/doc/BCM2837-ARM-Peripherals.-.Revised.-.V2-1.pdf)

34 changes: 19 additions & 15 deletions doc/1.1.md → doc/rpi3b qemu 之启动_01.md
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### 前置知识点
##### 1. 常见汇编指令
- mrs : `Move System Register allows the PE to read an AArch64 System register into a general-purpose register` (读取系统寄存器值到通用寄存器).
- **`mrs`** : `Move System Register allows the PE to read an AArch64 System register into a general-purpose register` (读取系统寄存器值到通用寄存器).

- msr : `Move general-purpose register to System Register allows the PE to write an AArch64 System register from a
- **`msr`** : `Move general-purpose register to System Register allows the PE to write an AArch64 System register from a
general-purpose register` (读取通用寄存器的值到系统寄存器).

- adr : `Load a label's relative address into the target register`.
- **`adr`** : `Load a label's relative address into the target register`.

- ldr : `calculates an address from a base register value and an offset register value, loads a word
- **`ldr`** : `calculates an address from a base register value and an offset register value, loads a word
from memory, and writes it to a register` (从基地址 + offset 处读取内存值到寄存器).

- mov : `copies a value from a register to the destination register` (从寄存器拷贝赋值给目标寄存器).
- **`mov`** : `copies a value from a register to the destination register` (从寄存器拷贝赋值给目标寄存器).

- isb : 它会清洗流水线,以保证所有它前面的指令都执行完毕之后,才执行它后面的指令.
- cbz : `and Branch on Zero compares the value in a register with zero, and conditionally branches to a label at a PC-relative offset if the comparison is equal` (将寄存器的值和0 比较,如果相等则跳转到label).
- lsr : `Logical Shift Right (register) shifts a register value right by a variable number of bits, shifting in zeros, and writes the result to the destination register.`
- **`isb`** : 它会清洗流水线,以保证所有它前面的指令都执行完毕之后,才执行它后面的指令.
- **`cbz`** : `and Branch on Zero compares the value in a register with zero, and conditionally branches to a label at a PC-relative offset if the comparison is equal` (将寄存器的值和0 比较,如果相等则跳转到label).
- **`lsr`** : `Logical Shift Right (register) shifts a register value right by a variable number of bits, shifting in zeros, and writes the result to the destination register.`

![基本指令.png](https://s2.loli.net/2022/05/30/gjPkeQyOG4fL1ZJ.png)


##### 2. ARM寄存器
Expand Down Expand Up @@ -44,7 +46,8 @@ bit 31:[0] : EL0/1 all is AARCH32

而操作系统是运行在EL1 运行等级,该等级能够访问系统寄存器和配置管理进程资源. EL2 用于虚拟机场景,EL3 用于实现Trustzone 技术隔离REE 和TEE.

![image](http://www.justfun.icu/wp-content/uploads/2022/03/tz_06.jpg)

![tz_06.jpg](https://s2.loli.net/2022/05/25/vPhnGpVylETaUZq.jpg)


---
Expand Down Expand Up @@ -94,7 +97,6 @@ el2_entry:

adr x0, el1_entry
msr elr_el2, x0

eret

el1_entry:
Expand All @@ -116,7 +118,9 @@ el1_entry:
### 主函数
##### 1. 串口初始化
UART 相关的GPIO 描述如下.
![image](https://github.com/cuijier/learn_kernel/blob/v1/doc/doc_pic/1.3.PNG)

![1.3.PNG](https://s2.loli.net/2022/05/25/u1HNkzU7CcxmtEe.png)



我们使用GPIO14/15作为串口的发送和接收引脚,对应表格可以看到我们需要使用这两个引脚的alt0 function.
Expand All @@ -127,14 +131,14 @@ GPFSEL1: GPIO10 ~ GPIO19 alt function setting
bit [14:12] : gpio14 alt setting, 100 is alt function 0.
bit [17:15] : gpio15 alt setting, 100 is alt function 0.
```
![image](https://github.com/cuijier/learn_kernel/blob/v1/doc/doc_pic/1.2.PNG)

![1.2.PNG](https://s2.loli.net/2022/05/25/OlMuKIZT7hzNLkU.png)


并将其配置为`no pull up/down`,完成基本的gpio 属性配置后就是波特率的设置了


```math
BAUDDIV = \frac {FUARTCLK}{16\times Baudrate} = IBRD + 64\times FBRD
```
![111.PNG](https://s2.loli.net/2022/05/27/1Y5TtFioQyPHcZV.png)


```
Expand Down
19 changes: 15 additions & 4 deletions doc/2.1.md → doc/rpi3b qemu 之异常_02.md
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Expand Up @@ -55,6 +55,9 @@ vectors:
.endm
```
现在只关注中断这一部分的实现,在处理中断前需要先保存当前CPU 程序运行状态,这个通过 `kernel_entry` 函数完成,处理完中断后需要恢复到中断之前的状态,通过`kernel_exit` 来实现.

![image](https://documentation-service.arm.com/static/5f872814405d955c5176de29?token=)

```
el1_irq:
kernel_entry
Expand Down Expand Up @@ -140,7 +143,8 @@ disable_irq:
ARMv8架构集成了`generic timer`的硬件设计,为系统提供了计时、计数以及触发timer event的功能.

ARM generic timer相关的硬件block如下图所示
![image](https://github.com/cuijier/learn_kernel/blob/v1/doc/doc_pic/2.2.PNG)

![2.2.PNG](https://s2.loli.net/2022/05/25/9HLGNmqI31JWUiR.png)


从图可知每个generic timer分两部分构成
Expand All @@ -157,7 +161,7 @@ System counter是一个永远在线的设备,它提供固定频率的系统计
#### `Generic Timer`
所有`generic timer`的`physical counter`都来自`system counter`,可通过`CNTPCT_EL0` 寄存器来获取, 有 physical 就有virtual, processor可以通过`CNTVCT`寄存器访问`virtual counter`, 不过对于不支持security extension和virtualization extension的系统, `virtual counter`和`physical counter`是一样的值.
每个timer都会有三个寄存器,如下表
![image](https://github.com/cuijier/learn_kernel/blob/v1/doc/doc_pic/2.1.PNG)
![2.1.PNG](https://s2.loli.net/2022/05/25/VGHJs9BvNEzL864.png)

```
CV: 64-bit CompareValue register.
Expand All @@ -184,7 +188,8 @@ Control: Counter-timer Physical Timer Control register
#### `Timer interrrupt`
timer 通过`CTL`寄存器配置是否生成中断,每个core timer 生成的中断只能分发到该core,不能分发到别的core.属于PPI,各Timer 与中断号的对于关系如下.

![image](https://github.com/cuijier/learn_kernel/blob/v1/doc/doc_pic/2.3.PNG)
![2.3.PNG](https://s2.loli.net/2022/05/25/cAVBX2ab4WYZlqj.png)


```
//Control 设置为1,打开了Timer并会生成interrupt 信号.
Expand All @@ -209,5 +214,11 @@ asm volatile(
: "memory");
```

![1HZ Timer interrupt](https://github.com/cuijier/learn_kernel/blob/v1/doc/doc_pic/2.4.gif)

![2.4.gif](https://s2.loli.net/2022/05/25/fRQ5Um72Fp9hLH8.gif)






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