tabs/kernel/shell.c

#ifndef SHELL_C
#define SHELL_C

#define SHELL_CMD_BUFFER_SIZE 128

#include <stddef.h>

#include "terminal.c"
#include "inline_asm.c"
#include "drivers/keyboard/keyboard.c"
#include "memory.c"

char buffer[SHELL_CMD_BUFFER_SIZE];
int buffer_idx = 0;

int echo(char *input) {
    terminal_writestring(input);
    terminal_putchar('\n');
    return 0;
}

int hello(char *unused) {
    terminal_writestring("Hello, world!\n");
    return 0;
}

int cls(char *unused) {
    terminal_initialize();
    return 0;
}

int get_gdt(char *unused) {
    gdt_desc desc = {2, 2};
    sgdt(&desc);
    terminal_writestring("limit = ");
    terminal_writeint(desc.limit, 10);
    terminal_writestring("\nbase = 0x");
    terminal_writeint(desc.base, 16);
    terminal_putchar('\n');

    gdt_entry *entries = (gdt_entry *) desc.base;
    int num_entries = (desc.limit + 1) / 8;
    for (int entry_num = 0; entry_num < num_entries; entry_num++) {
        gdt_entry entry = entries[entry_num];
        uint32_t base = entry.base_lower | entry.base_middle << 16 | entry.base_higher << 24;
        uint32_t limit = entry.limit_lower | (entry.flags_limit_higher & 0x0f) << 16;
        uint8_t flags = (entry.flags_limit_higher >> 4);
        bool is_data = ((entry.access_byte & 0b00001000) >> 3) == 0;

        //terminal_writestring("\nEntry ");
        //terminal_writeint(entry_num, 10);
        print("base = %x\n", base);
        print("limit = %x\n", limit);
        print("flags = %b\n", (entry.flags_limit_higher >> 4));

        if ((flags & 0b1000) == 0) {
            print(" (byte granularity");
        } else {
            print(" (page granularity");
        }

        if ((flags & 0b0100) == 0) {
            print(", 16 bit)");
        } else {
            print(", 32 bit)");
        }
        print("\n");

        print("access = %b (ring %d",
              entry.access_byte,
              (entry.access_byte & 0b01100000) >> 5
        );
        if ((entry.access_byte & 0b00010000) == 0) {
            print(", System");
        }
        if (is_data) {
            print(", Data");

            if ((entry.access_byte & 0b00000100) == 0) {
                print(" (growing up, ");
            } else {
                print(" (growing down, ");
            }

            if ((entry.access_byte & 0b00000010) == 0) {
                print("r--)");
            } else {
                print("rw-)");
            }
        } else {
            print(", Code");

            if ((entry.access_byte & 0b00000100) == 0) {
                print(" (non-conforming, ");
            } else {
                print(" (conforming, ");
            }

            if ((entry.access_byte & 0b00000010) == 0) {
                print("--x)");
            } else {
                print("r-x)");
            }
        }

        print(")\n");
    }
    return 0;
}

int ree(char *unused) {
    terminal_initialize();
    terminal_putchar('R');
    for (int i = 1; i < VGA_WIDTH * VGA_HEIGHT; i++) {
        terminal_putchar('e');
    }
    return 0;
}

int save_text(char *text) {
    char *mem_block = alloc(strlen(text) * sizeof(char));
    char *c;
    int i = 0;
    for (c = text; *c != '\0'; c++) {
        mem_block[i] = *c;
        i++;
    }
}

// TODO This is ugly, fix this 
const char *shell_commands_strings[] = {
        "echo",
        "hello",
        "cls",
        "ree",
        "getgdt",
        "memdump",
        "savetext",
        NULL
};

int (*shell_commands_functions[])(char *) = {
        echo,
        hello,
        cls,
        ree,
        get_gdt,
        command_mem_dump,
        save_text
};

int run_command(char *buffer) {

    if (buffer[0] == 0) {
        return 0;
    }
    char command[SHELL_CMD_BUFFER_SIZE] = {0};
    int i = 0;
    while (buffer[i] != 0 && buffer[i] != ' ') {
        command[i] = buffer[i];
        i++;
    }

    int command_idx = 0;

    while (shell_commands_strings[command_idx] != NULL) {
        int check_idx = 0;
        while (command[check_idx] != 0 && shell_commands_strings[command_idx][check_idx] == command[check_idx]) {
            check_idx++;
        }
        if (command[check_idx] == 0 && shell_commands_strings[command_idx][check_idx] == 0) {
            return (shell_commands_functions[command_idx])(buffer + i + 1);
        }
        command_idx++;
    }
    return -1;
}

void shell_step() {
    char curr_char = getchar();

    if (curr_char == '\n') {
        terminal_putchar(curr_char);
        buffer[buffer_idx] = 0;
        int result = run_command(buffer);
        for (int i = 0; i < SHELL_CMD_BUFFER_SIZE; i++) {
            buffer[i] = 0;
        }
        buffer_idx = 0;

        if (result == -1) {
            print("No such command\n");
        }
    } else if (curr_char == 0x08) {
        if (buffer_idx != 0) {
            buffer_idx--;
            buffer[buffer_idx] = 0;
            terminal_putchar(curr_char);
        }
    } else {
        buffer[buffer_idx] = curr_char;
        buffer_idx++;
        terminal_putchar(curr_char);
    }
}

#endif //SHELL_C