paging.c

一个微型操作系统源码

/** paging.c                                  
 **
 ** Description:
 **    Virtual Memory, hardware paging
 **
 **/

#include <mm.h>

pagedir *PD = NULL;

int setupPaging(ulong available)
{
   uint pages, pdes, total_memory;

   total_memory = available;
   pages = (total_memory >> PAGE_SHIFT);
   /* number of page directory entries */
   pdes =  (pages>>10) + (((pages%1024) > 0) ? 1 : 0);

   PD = (pagedir *)PAGING_CR3;
   
   vmMapInit(PD,pages);
   vmKernelMap(PD);

   enablePaging();
   return pdes;
}


void __inline__ make_pde(pagedir *dir, uint nr, ulong addr,uchar attrib)
{
   dir->entry[nr].present   = 1;
   dir->entry[nr].readWrite = 1;
   dir->entry[nr].user      = 0;
   dir->entry[nr].accessed  = 0;
   dir->entry[nr].dirty     = 0;
   dir->entry[nr].os_use    = attrib;
   dir->entry[nr].reserved1	= 0;
   dir->entry[nr].reserved2	= 0;
   dir->entry[nr].address   = (ulong)addr;
#ifdef DEBUG
/*   if (addr>0)
      kprintf("PAGE: pde %d at 0x%08lx\n", nr,(ulong)addr); */
#endif
}


void __inline__ make_pte(pagetable *tab, uint nr, ulong addr, uchar attrib)
{
   tab->entry[nr].present   = 1;
   tab->entry[nr].readWrite = 1;
   tab->entry[nr].user      = 1;
   tab->entry[nr].accessed  = 0;
   tab->entry[nr].dirty     = 0;
   tab->entry[nr].os_use    = attrib;
   tab->entry[nr].reserved1	= 0;
   tab->entry[nr].reserved2	= 0;
   tab->entry[nr].address   = (ulong)addr;
#ifdef DEBUG
/*   kprintf("PAGE: pte %d at 0x%08lx\n", nr, (ulong)addr); */
#endif
}


void enablePaging(void)
{
   ulong CR0 = get_CR0();
   set_CR3(PAGING_CR3);
   /* set most significant bit of CR0 */
   set_CR0(CR0 | 0x80000000); 
}