path: root/vmem.c

/* vmem.c - MemTest-86 
 *
 * Virtual memory handling (PAE)
 *
 * Released under version 2 of the Gnu Public License.
 * By Chris Brady
 */
#include "stdint.h"
#include "test.h"
#include "cpuid.h"

extern struct cpu_ident cpu_id;

static unsigned long mapped_win = 1;
void paging_off(void)
{
    if (!cpu_id.fid.bits.pae)
        return;
    __asm__ __volatile__
        (
         /* Disable paging */
         "movl %%cr0, %%eax\n\t"
         "andl $0x7FFFFFFF, %%eax\n\t"
         "movl %%eax, %%cr0\n\t"
         : :
         : "ax"
         );
}

static void paging_on(void *pdp)
{
    if (!cpu_id.fid.bits.pae)
        return;
    __asm__ __volatile__
        (
         /* Load the page table address */
         "movl %0, %%cr3\n\t"
         /* Enable paging */
         "movl %%cr0, %%eax\n\t"
         "orl $0x80000000, %%eax\n\t"
         "movl %%eax, %%cr0\n\t"
         :
         : "r" (pdp)
         : "ax"
         );
}

static void paging_on_lm(void *pml)
{
    if (!cpu_id.fid.bits.pae)
        return;
    __asm__ __volatile__
        (
         /* Load the page table address */
         "movl %0, %%cr3\n\t"
         /* Enable paging */
         "movl %%cr0, %%eax\n\t"
         "orl $0x80000000, %%eax\n\t"
         "movl %%eax, %%cr0\n\t"
         :
         : "r" (pml)
         : "ax"
         );
}

int map_page(unsigned long page)
{
    unsigned long i;
    struct pde {
        unsigned long addr_lo;
        unsigned long addr_hi;
    };
    extern unsigned char pdp[];
    extern unsigned char pml4[];
    extern struct pde pd2[];
    unsigned long win = page >> 19;

    /* Less than 2 GB so no mapping is required */
    if (win == 0) {
        return 0;
    }
    if (cpu_id.fid.bits.pae == 0) {
        /* Fail, we don't have PAE */
        return -1;
    }
    if (cpu_id.fid.bits.lm == 0 && (page > 0x1000000)) {
        /* Fail, we want an address that is out of bounds (> 64GB)
         *  for PAE and no long mode (ie. 32 bit CPU).
         */
        return -1;
    }
    /* Compute the page table entries... */
    for(i = 0; i < 1024; i++) {
        /*-----------------10/30/2004 12:37PM---------------
         * 0xE3 --
         * Bit 0 = Present bit.      1 = PDE is present
         * Bit 1 = Read/Write.       1 = memory is writable
         * Bit 2 = Supervisor/User.  0 = Supervisor only (CPL 0-2)
         * Bit 3 = Writethrough.     0 = writeback cache policy
         * Bit 4 = Cache Disable.    0 = page level cache enabled
         * Bit 5 = Accessed.         1 = memory has been accessed.
         * Bit 6 = Dirty.            1 = memory has been written to.
         * Bit 7 = Page Size.        1 = page size is 2 MBytes
         * --------------------------------------------------*/
        pd2[i].addr_lo = ((win & 1) << 31) + ((i & 0x3ff) << 21) + 0xE3;
        pd2[i].addr_hi = (win >> 1);
    }
    paging_off();
    if (cpu_id.fid.bits.lm == 1) {
        paging_on_lm(pml4);
    } else {
        paging_on(pdp);
    }
    mapped_win = win;
    return 0;
}

void *mapping(unsigned long phys_page)
{
    void *result;
    if (phys_page < WIN_SZ_PAGES) {
        /* If the page is below 2GB, address it directly */
        result = (void *)(phys_page << 12);
    }
    else {
        // Higher physical pages map to a virtual address
        // in the 2G-4G range.
        unsigned long alias;
        alias = phys_page & 0x7FFFF;
        alias += 0x80000;
        result = (void *)(alias << 12);
    }
    return result;
}

void *emapping(unsigned long phys_page)
{
    void *result;
    result = mapping(phys_page - 1);
    /* Fill in the low address bits */
    result = ((unsigned char *)result) + 0xffc;
    return result;
}

unsigned long page_of(void *addr)
{
    unsigned long page;
    page = ((unsigned long)addr) >> 12;
    if (page >= 0x80000) {
        page &= 0x7FFFF;
        page += mapped_win << 19;
    }
#if 0
    cprint(LINE_SCROLL -2, 0, "page_of(        )->            ");
    hprint(LINE_SCROLL -2, 8, ((unsigned long)addr));
    hprint(LINE_SCROLL -2, 20, page);
#endif	
    return page;
}