OS_Project/Part3/09_memory/kernel/kernel.c

    #include "kernel.h"

    // This only runs once and from there on forth only interrupts will cause something to happen
    // e.g. displaying to screen and taking input from keyboard
    void _start() {
    // Initialize Global Variables and set up interrrupt handlers
    // These variables are a vulnerability to OS security if someone can adjust
    // the lower value in the kernel code (exploiting, for  example, an Intel address hack)
    // than kernel memory and even kernel code can be overwritten
    // https://www.wired.com/story/intel-lab-istare-hack-chips/
    // See libc/globals.h for KMEM_START and KMEM_END values
    // See libc/globals.h for UMEM_START and UMEM_END values
       kmem_addr = KMEM_START;
       kernel_mem_limit = KMEM_END;

       umem_addr = UMEM_START;
       user_mem_limit = UMEM_END;

       global_head = NULL;
       global_id = 0;


        isr_install();
        irq_install();

        kprint("Type something, it will go through the kernel\n"
            "Type HELP to list commands\n> ");
    }

    // An interrupt calls this function to parse what was typed in, this is, essentially, your
    // Command Line Interpreter for now.
    void user_input(char *input) {
       static u32 delete_id = 0;           // static persistent variable for incrementing during test
       static node* umem_head = NULL;      // static persistent head variable for contiguous block allocations
        if (strcmp(input, "END") == 0) {
            kprint("Stopping the CPU. Bye!\n");
            asm volatile("hlt");
        } else if (strncmp(input, "ADD", 3) == 0) {
            u32 base = 0x10000;
            u32 limit = 0x100;
            bool valid = true;
            if (sstrlen(input, 15) > 4) {
                char *args1 = input + 4;
                base = digit_conver(args1);
                int nDigits = digit_len(base);
                if (sstrlen(args1, 15) > nDigits + 1) {
                    char *args2 = args1 + nDigits + 1;
                    limit = digit_conver(args2);
                    if (limit < 100) {
                        kprint("That memory address is to below the min of 0x100.\n");
                        valid = false;
                    }
                }
                if (base < 10000) {
                    kprint("That memory address is reserved by the Kernel, addresses must be 10000+\n");
                    valid = false;
                }
            }
            if (valid) {
                umem_head = add_node( umem_head, base, limit, true, global_id++);
            }
        } else if (strcmp(input, "LIST") == 0) {
          kprint("***** FORWARD ****\n");
          print_list( umem_head, true);
          kprint("***** REVERSE ****\n");
          print_list( umem_head, false);
        } else if (strcmp(input, "SHORTLIST") == 0) {
          shortprint_list( umem_head, true);
          kprint("\n******************\n");
          shortprint_list( umem_head, false);
        } else if (strcmp(input, "PAGE") == 0) {
            u32 phys_addr = 0;
            u32 page = umalloc(0x4200, 0, &phys_addr);
            kprint_hex( "Page: ", page, 10);
            kprint_hex(", physical address: ", phys_addr, 10);
            kprint("\n");
        } else if (strcmp(input, "DELETE") == 0) {
           umem_head = remove_node_by_id( umem_head, delete_id++);
        } else if (strcmp(input, "INSERT") == 0) {
          node *new_node = create_node( 0x15000, 0x1100, true, global_id++);
          node *insert_point = find_id( umem_head, 3);
          umem_head = insert_node( umem_head, insert_point, new_node, true);
          new_node = create_node( 0x18000, 0x2100, true, global_id++);
          insert_point = find_id( umem_head, 5);
          umem_head = insert_node( umem_head, insert_point, new_node, false);
        } else if (strcmp(input, "SORTA") == 0) {
          umem_head = hacksort_list( umem_head, true);
        } else if (strcmp(input, "SORTD") == 0) {
          umem_head = hacksort_list( umem_head, false);
        } else if (strcmp(input, "SWAP") == 0) {
          node *n1 = find_id( umem_head, 1);
          node *n2 = find_id( umem_head, 5);
          node *n3 = find_id( umem_head, 3);
          node *n4 = find_id( umem_head, 7);
          swap_node_data( n1, n2);
          swap_node_data( n2, n3);
          swap_node_data( n3, n4);
        } else if (strcmp(input, "TEST") == 0) {
           char s1[10] = "ABCDFFGH\0";
           char s2[10] = "ABCDEGH\0";
           int x = strncmp( s1, s2, 5);
           kprint_hex( "STRNCMP: ", x, 16);
           kprint("\n");

           x = sstrlen( s2, 10);
           kprint_hex( "SSTRLEN: ", x, 10);
           kprint("\n");

           x = strlen( s2);
           kprint_hex( "STRLEN: ", x, 10);
           kprint("\n");
        } else if (strcmp(input, "HELP") == 0) {
           kprint("Current Commands: ADD, LIST, SHORTLIST, PAGE, DELETE,\n");
           kprint("                : END, INSERT, SORTA, SORTD, SWAP, TEST, HELP\n");
		    kprint("   Review the kernel.c source code to see what each command does.\n");
		    kprint("   These are hard coded and are just examples, modify as you see fit.\n");
		    kprint(" for example - TEST was just added so that I could test the strlen commands.\n");
        } else if (strcmp(input, "HOLES") == 0) {
            print_holes(umem_head);
        } else {
           kprint("You said: ");
           kprint(input);
           kprint("\n");
        }
        kprint("> ");
    }

    int digit_len(unsigned digit) {
        if (digit >= 1000000000) return 10;
        if (digit >= 100000000)  return 9;
        if (digit >= 10000000)   return 8;
        if (digit >= 1000000)    return 7;
        if (digit >= 100000)     return 6;
        if (digit >= 10000)      return 5;
        if (digit >= 1000)       return 4;
        if (digit >= 100)        return 3;
        if (digit >= 10)         return 2;
        return 1;
    }

    int digit_conver(const char *hexString) {
        u32 result = 0;
        while (*hexString != '\0') {
            char hexChar = *hexString;
            if ((hexChar >= '0' && hexChar <= '9') || (hexChar >= 'A' && hexChar <= 'F')) {
                int digit = (hexChar >= '0' && hexChar <= '9') ? (hexChar - '0') : (10 + (hexChar - 'A'));
                result = result * 16 + digit;
            } else {
                break;
            }
            hexString++;
        }
        return result;
    }


void print_holes(node* umem_head) {
    if (umem_head == NULL) {
        kprint("Holes list is Empty");
    }

    node *hole = NULL;
    while(umem_head != NULL) {
        if (umem_head->previous == NULL) {
            if (umem_head->base_register != 0) {
                hole = add_node( hole, 0x10000, umem_head->base_register-0x10000, true, 1);
            }
        } else if (umem_head->next == NULL) {
            node *previous = umem_head->previous;
            hole = add_node( hole, previous->base_register+previous->limit_register, -1, true, 1);
        } else {
            node *previous = umem_head->previous;
            node *next = umem_head->next;
            hole = add_node( hole, previous->base_register+previous->limit_register, next->base_register, true, 1);
        }
        umem_head = umem_head->next;
    }
    print_list(hole, false);
}