boot/entry.c

/*
      +----------------------------------------------------------+
      | +------------------------------------------------------+ |
      | |  Quafios Kernel 1.0.1.                   | |
      | |  -> Kernel code entry (i386).                        | |
      | +------------------------------------------------------+ |
      +----------------------------------------------------------+
*/

// This file is part of Quafios 1.0.1 source code.
// Copyright (C) 2012  Mostafa Abd El-Aziz Mohamed.

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Quafios.  If not, see <http://www.gnu.org/licenses/>.

// Visit http://www.quafios.com/ for contact information.

extern /* "C" */ void entry() __attribute__ ((section(".entry")));
extern /* "C" */ void entry_error() __attribute__ ((section(".entry")));

void entry_error(const char *vmsg) {
    unsigned int  i = 0;
    unsigned char col = *((unsigned char *) 0x450);
    unsigned char row = *((unsigned char *) 0x451);
    unsigned int  off = ((row*80)+col)*2;
    unsigned char *vga = (unsigned char *) 0xb8000;
    char *msg = (char *) kvirt_to_phy(vmsg);
    while (msg[i]) {
        vga[off++] = msg[i++];
        vga[off++] = 0x0C;
    }
    idle();
}

void entry()  {

    // (I) Read Multiboot information:
    // ========================================
    // Multi-boot standard specs says that after kernel load,
    // EAX and EBX registers should contain "Boot magic
    // signature" and a pointer to "Boot info structures"
    // respectively.
    unsigned int boot_magic;
    multiboot_info_t *mbi;

    __asm__ ("":"=a"(boot_magic),"=b"(mbi));

    // Check if the boot magic signature is invalid:
    if (boot_magic != MULTIBOOT_BOOTLOADER_MAGIC)
        entry_error("Boot Error: Boot loader is not a multi-boot compliant loader.");

    // Get info about BIOS memory map from the boot info struct:
    if (!(mbi->flags & MULTIBOOT_INFO_MEM_MAP))
        entry_error("Boot Error: No memory map found.");

    unsigned int *map = (unsigned int *) kvirt_to_phy(&pmmap);
    linkedlist *flist = (linkedlist *) kvirt_to_phy(&pfreelist);

    // Read BIOS Memory Map, and set RAM Regions as free:
    unsigned int i = 0, j;
    linknode *prev = (linknode *) flist;

    while (i < (mbi->mmap_length)) {
        multiboot_memory_map_t *mbmm; // Entry.

        mbmm = (multiboot_memory_map_t *) (mbi->mmap_addr + i);

        unsigned int addr = mbmm->addr;
        unsigned int size = mbmm->len;

        if (mbmm->type == MULTIBOOT_MEMORY_AVAILABLE) {

            *kvirt_to_phy(&ram_size) = addr + size;

            // Align to 4KB Boundary:
            if (addr & 0xFFF) {
                size -= 0x1000-(addr&0xFFF);
                addr = (addr&0xFFFFF000) + 0x1000;
            }

            j = 0;
            while(j < size/PAGE_SIZE) {

                unsigned int frame = (addr>>12) + j++;
                unsigned int page = frame * PAGE_SIZE;

                // Don't mark these pages as free:
                // Lower Memory:
                if (page >= LOWER_MEMORY_BASE &&
                    page <  LOWER_MEMORY_SIZE) continue;

                // Kernel Space:
                if (page >= KERNEL_PHYSICAL_START &&
                    page <  KERNEL_PHYSICAL_END) continue;

                // add the page to free list :)
                linknode *entry = (linknode *) &map[frame];
                prev->next = (linknode *) kphy_to_virt(entry);
                prev = entry;
                flist->count++;
            }

            *kvirt_to_phy(&pmem_usable_pages) += j;
        }
        i += (mbmm->size) + sizeof(mbmm->size);
    }
    prev->next = NULLNODE;

    // (II) Initialize general page directory & page tables:
    // ======================================================
    unsigned int membase;
    // Kernel Memory Area Entries in general page table
    // (at 0xC0000000):
    for (i = 768; i < 1024; i++)
        kvirt_to_phy(general_pagedir)[i] = ((unsigned int)
            &kvirt_to_phy(kmem_pagetab)[(i-768)*1024]) | PAGE_ENTRY_KERNEL_MODE;

    // 1- Initialize kernel image page tables...
    membase = KERNEL_PHYSICAL_START;
    for (i = 0; membase < KERNEL_PHYSICAL_END; i++) {
        kvirt_to_phy(kmem_pagetab)[i] = membase | PAGE_ENTRY_KERNEL_MODE;
        membase += PAGE_SIZE;
    }

    // 2- Initialize lower memory image in kernel memory:
    membase = LOWER_MEMORY_BASE;
    for (; membase < LOWER_MEMORY_END; i++) {
        kvirt_to_phy(kmem_pagetab)[i] = membase | PAGE_ENTRY_KERNEL_MODE;
        membase += PAGE_SIZE;
    }

    // Temporarily map ".entry" section:
    kvirt_to_phy(general_pagedir)[0] = ((unsigned int)
                        kvirt_to_phy(temp_pagetab)) |
                        PAGE_ENTRY_KERNEL_MODE;

    kvirt_to_phy(temp_pagetab)[ENTRY_SECTION_START/PAGE_SIZE] =
                ENTRY_SECTION_START | PAGE_ENTRY_KERNEL_MODE;

    // (III) Enable Paging:
    // ======================
    // Setup CR3:
    set_cr3(kvirt_to_phy(general_pagedir));

    // Write-back and invalidate the cache:
    __asm__ ("wbinvd");

    // Enable Paging and Disable Caching:
    set_cr0(CR0_GENERIC);

    // (IV) Change Stack:
    // ====================
    __asm__ ("mov %%eax, %%esp"::"a"(&kernel_stack[KERNEL_STACK_SIZE]));

    // (V) Initialize kernel:
    // ==========================
    __asm__ ("call main");
}