Squashed commit of the following:

commit c2e6081
Author: focused_xy <[email protected]>
Date:   Sun Oct 20 14:47:25 2024 +0800

    perf: 优化lec3

commit 2269fb3
Author: M4yGem1ni <[email protected]>
Date:   Fri Oct 18 11:03:12 2024 +0800

    	修改：     Lectures/Lecture3/Lecture3/index.html
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commit e3ea1e0
Author: focused_xy <[email protected]>
Date:   Thu Oct 17 15:32:32 2024 +0800

    init: lec3 init

commit fd136b3
Author: focused_xy <[email protected]>
Date:   Fri Oct 18 08:03:12 2024 +0800

    init: lec3 note init

commit b4cbce7
Author: focused_xy <[email protected]>
Date:   Fri Oct 18 08:00:17 2024 +0800

    init: lec3 init

.gitignore

@@ -1,2 +1,4 @@
 .DS_Store
 .vscode
+__pycache__
+*.pyc

Lectures/Lecture3/Codes/makefile

@@ -0,0 +1,13 @@
+CC := gcc
+CFLAGS := -Wall -Wextra -Werror -g -std=c11
+TARGET := stack
+
+all: $(TARGET)
+
+$(TARGET): %:%.c
+	$(CC) $(CFLAGS) -o $@ $<
+
+clean:
+	-rm -rf $(TARGET)
+
+.PHONY: all clean

Lectures/Lecture3/Codes/os-exec/makefile

@@ -0,0 +1,21 @@
+all: minimal static
+
+minimal.o: minimal.c
+	gcc -c -o $@ $<
+
+minimal: minimal.o
+	ld -o $@ $<
+
+minimal-asm: minimal
+	objdump -d $<
+
+static: minimal.o
+	gcc -static -o $@ $<
+
+static-asm: static
+	objdump -d $<
+
+clean:
+	-rm -f minimal.o minimal static
+
+.PHONY: all minimal-asm static-asm clean

Lectures/Lecture3/Codes/os-exec/minimal.c

@@ -0,0 +1,17 @@
+#include <sys/syscall.h>
+#include <unistd.h>
+
+const char str[] = "\033[01;31mHello, OS World\033[0m\n";
+const int str_size = sizeof str - 1;
+
+int main(void) {
+  asm volatile("movl %0, %%eax\n\t" // 系统调用号：SYS_write
+               "movl $1, %%edi\n\t" // 文件描述符：STDOUT_FILENO (标准输出)
+               "movq %2, %%rsi\n\t" // 字符串地址
+               "movl %3, %%edx\n\t" // 字符串长度
+               "syscall"            // 调用系统调用
+               :
+               : "r"(SYS_write), "r"(STDOUT_FILENO), "r"(str), "r"(str_size)
+               : "eax", "edi", "rsi", "edx");
+  return 0;
+}

Lectures/Lecture3/Codes/os-model/main.c

@@ -0,0 +1,57 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "os.h"
+
+/*
+In this model, we have a mini Operating System that can run multiple processes.
+Each process has a context that contains two variables: remainingStep and charToOutput.
+remainingStep is the number of steps that a process will run and then exit by doing a syscall EXIT.
+charToOutput is the character that a process will write to the console by doing a syscall WRITE.
+在这个模型中，我们模拟了一个简单的操作系统，可以运行多个进程.
+每个进程有一个上下文，包含两个变量：remainingStep 和 charToOutput.
+程序将运行，并不断发起系统调用，请求操作系统向终端中写入字符 charToOutput.
+在写入了 remainingStep 次后, 进程将会使用系统调用 SYS_EXIT 退出。
+ */
+
+
+void run() {
+    Process *current;
+    while (process_count()) {
+        // The Operating System will randomly choose a process to run
+        // 操作系统会随机选择一个进程来运行
+        current = process_schedule();
+
+        // Switch process context and run it until a syscall
+        // 切换进程上下文并运行，直到发起系统调用
+        Syscall call = process_step(current);
+
+        if (call.syscall == SYS_EXIT) {
+            // Process exits
+            // 进程退出
+            process_exit(current);
+        } else if (call.syscall == SYS_WRITE) {
+            // Write the character from syscall arg to the console
+            // 将系统调用参数中的字符写入终端
+            putchar(call.arg);
+        }
+    }
+    putchar('\n');
+}
+
+int main() {
+    // Initialize the Operating System
+    // 初始化操作系统
+    init();
+
+    // spawn processes
+    // 创建进程
+    spawn_process(5, 'A');
+    spawn_process(5, 'B');
+    spawn_process(5, 'C');
+
+    // start running
+    // 开始运行
+    run();
+
+    return 0;
+}

Lectures/Lecture3/Codes/os-model/makefile

@@ -0,0 +1,14 @@
+CC=gcc
+CFLAGS=-Wall -Wextra -Werror -std=c11
+TARGET=main
+
+$(TARGET): main.c os.c os.h
+	$(CC) -o $(TARGET) main.c os.c $(CFLAGS)
+
+all: $(TARGET)
+
+run: $(TARGET)
+	./$(TARGET)
+
+clean:
+	rm -f $(TARGET)

Lectures/Lecture3/Codes/os-model/os.c

@@ -0,0 +1,61 @@
+#include "os.h"
+#include <stdlib.h>
+#include <time.h>
+
+void init() {
+    srand(time(NULL));
+}
+
+Process procArray[MAX_PROC];
+Process *runningProcess[MAX_PROC];
+
+unsigned int procCount = 0;
+
+int process_count() {
+    return procCount;
+}
+
+int spawn_process(int var1, char var2) {
+    if (procCount >= MAX_PROC) {
+        return -1;
+    } else {
+        // Initialize process 
+        Process *proc = &procArray[procCount];
+        proc->remainingStep = var1;   // A process will run var1 step(s)
+        proc->charToOutput = var2;   // A process will write this character to console
+        runningProcess[procCount] = proc;
+        procCount ++;
+        return 0;
+    }
+}
+
+Process *process_schedule() {
+    int i = rand() % procCount;
+    return runningProcess[i];
+}
+
+Syscall process_step(Process *proc) {
+    Syscall call;
+    if (proc->remainingStep > 0) {
+        proc->remainingStep --;
+        call.syscall = SYS_WRITE;
+        call.arg = proc->charToOutput;
+    } else {
+        call.syscall = SYS_EXIT;
+        call.arg = 0;
+    }
+    return call;
+}
+
+void process_exit(Process *proc) {
+    for (unsigned int i = 0; i < procCount; i++) {
+        if (runningProcess[i] == proc) {
+            for (unsigned int j = i; j < procCount - 1; j++) {
+                runningProcess[j] = runningProcess[j + 1];
+            }
+            runningProcess[procCount - 1] = NULL;
+            procCount --;
+            break;
+        }
+    }
+}

Lectures/Lecture3/Codes/os-model/os.h

@@ -0,0 +1,32 @@
+#ifndef __OS_H__
+#define __OS_H__
+
+#define MAX_PROC 4
+
+typedef struct {
+    int  remainingStep; // A process will run remainingStep steps
+    char charToOutput;  // A process will write this character to console by doing a syscall
+} Process; // Process's Context
+
+enum {
+    SYS_EXIT,  // Process exits
+    SYS_WRITE, // Write to console with a character
+    SYS_EXEC,  // Execute a new process with a character
+};
+// If you know what we are doing, you can implement the exec syscall by yourself
+// You can also implement other syscalls if you want
+// You can do this as a lab exercise
+
+typedef struct {
+    unsigned int syscall;
+    char arg;
+} Syscall;
+
+void init();
+int process_count();
+int spawn_process(int var1, char var2);
+Process *process_schedule();
+Syscall process_step(Process *proc);
+void process_exit(Process *proc);
+
+#endif

Lectures/Lecture3/Codes/stack.c

@@ -0,0 +1,11 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(void) {
+    int x = 1;
+    void *y = malloc(sizeof(int));
+    printf("stack: %p\n", (void *)&x);
+    printf("heap : %p\n", y);
+    free(y);
+    return 0;
+}