[netwatch.git] / netwatch / packet.c

/* packet.c
 * OS-to-NetWatch communication packet interface
 * NetWatch system management mode administration console
 *
 * Copyright (c) 2008 Jacob Potter and Joshua Wise.  All rights reserved.
 * This program is free software; you can redistribute and/or modify it under
 * the terms found in the file LICENSE in the root of this source tree.
 *
 */

#include <stdint.h>
#include "packet.h"

#define PTE_FOR(x)      (((unsigned int)(x) >> 12) & 0x3FF)
#define PDE_FOR(x)      ((unsigned int)(x) >> 22)
#define ADDR_12_MASK(x) ((unsigned int)(x) & ~((1 << 12) - 1))
#define ADDR_22_MASK(x) ((unsigned int)(x) & ~((1 << 22) - 1))
#define LOWER_12(x)     ((unsigned int)(x) & ((1 << 12) - 1))
#define LOWER_22(x)     ((unsigned int)(x) & ((1 << 22) - 1))

#define PDE_4M_ADDR_SHIFT       22
#define PTE_4K_ADDR_SHIFT       12
#define PDE_TABLE_ADDR_SHIFT    12
#define PTE_FRAME_ADDR_MASK     (~((1 << PTE_4K_ADDR_SHIFT) - 1))
#define PDE_TABLE_ADDR_MASK     (~((1 << PDE_TABLE_ADDR_SHIFT) - 1))

#define PDE_ATTRIB_INDEX        (1 << 12)
#define PDE_GLOBAL              (1 << 8)
#define PDE_PAGE_SIZE           (1 << 7)
#define PDE_DIRTY               (1 << 6)
#define PDE_ACCESSED            (1 << 5)
#define PDE_NO_CACHE            (1 << 4)
#define PDE_WRITE_THROUGH       (1 << 3)
#define PDE_USER                (1 << 2)
#define PDE_READ_WRITE          (1 << 1)
#define PDE_PRESENT             (1 << 0)

#define PTE_GLOBAL              (1 << 8)
#define PTE_ATTRIB_INDEX        (1 << 7)
#define PTE_DIRTY               (1 << 6)
#define PTE_ACCESSED            (1 << 5)
#define PTE_NO_CACHE            (1 << 4)
#define PTE_WRITE_THROUGH       (1 << 3)
#define PTE_USER                (1 << 2)
#define PTE_READ_WRITE          (1 << 1)
#define PTE_PRESENT             (1 << 0)

asm ("get_cr3: mov %cr3, %eax \n ret");
uint32_t * get_cr3();

void * l2p (void * addr) {

        uint32_t * cr3 = get_cr3();
        uint32_t * page_table;
        uint32_t pde, pte;

        pde = cr3[PDE_FOR(addr)];

        if (!(pde & PDE_PRESENT)) {
                return 0;
        }

        if (pde & PDE_PAGE_SIZE) {
                return (void *)(ADDR_22_MASK(pde) | LOWER_22(addr));
        } else {
                page_table = (uint32_t *)(ADDR_12_MASK(pde));
                pte = page_table[PTE_FOR(addr)];

                if (!pte & PTE_PRESENT) {
                        return 0;
                }
                return (void *)(ADDR_12_MASK(pte) | LOWER_12(addr));
        }
}

packet_t * check_packet (uint32_t logical_base) {
        packet_t * physical_base;

        if (LOWER_12(logical_base) != 0) return 0;

        physical_base = l2p((void *)logical_base);

        if (!physical_base) return 0;
        if (physical_base->signature != 0x1BADD00D) return 0;
        
        return physical_base;
}