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improved documentation

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This commit is contained in:
Steffen Vogel 2014-11-28 02:26:40 +01:00
parent 95791bb12c
commit 883756d0b4
1 changed files with 16 additions and 11 deletions
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27
arch/x86/mm/page.c
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@ -24,6 +24,11 @@
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/**
* This is a 32/64 bit portable paging implementation for the x86 architecture
* using self-referenced page tables.
* See http://www.noteblok.net/2014/06/14/bachelor/ for a detailed description.
*/
#include <eduos/stdio.h>
#include <eduos/memory.h>
@ -59,12 +64,10 @@ static size_t * other[PAGE_LEVELS] = {
(size_t *) 0xFFFFE000
};
/** Addresses of child/parent tables */
/* Addresses of child/parent tables */
#define CHILD(map, lvl, vpn) &map[lvl-1][vpn<<PAGE_MAP_BITS]
#define PARENT(map, lvl, vpn) &map[lvl+1][vpn>>PAGE_MAP_BITS]
/** @todo Does't handle huge pages for now
* @todo This will cause a pagefaut if addr isn't mapped! */
size_t page_virt_to_phys(size_t addr)
{
size_t vpn = addr >> PAGE_BITS; // virtual page number
@ -81,7 +84,7 @@ int page_map(size_t viraddr, size_t phyaddr, size_t npages, size_t bits)
long vpn = viraddr >> PAGE_BITS;
long first[PAGE_LEVELS], last[PAGE_LEVELS];
// calculate index boundaries for page map traversal
/* Calculate index boundaries for page map traversal */
for (lvl=0; lvl<PAGE_LEVELS; lvl++) {
first[lvl] = (vpn ) >> (lvl * PAGE_MAP_BITS);
last[lvl] = (vpn+npages-1) >> (lvl * PAGE_MAP_BITS);
@ -89,8 +92,8 @@ int page_map(size_t viraddr, size_t phyaddr, size_t npages, size_t bits)
spinlock_lock(&kslock);
/* We start now iterating through the entries
* beginning at the root table (PGD) */
/* Start iterating through the entries
* beginning at the root table (PGD or PML4) */
for (lvl=PAGE_LEVELS-1; lvl>=0; lvl--) {
for (vpn=first[lvl]; vpn<=last[lvl]; vpn++) {
if (lvl) { /* PML4, PDPT, PGD */
@ -135,6 +138,8 @@ int page_unmap(size_t viraddr, size_t npages)
spinlock_lock(&kslock);
/* Start iterating through the entries.
* Only the PGT entries are removed. Tables remain allocated. */
for (vpn=start; vpn<end; vpn++)
self[0][vpn] = 0;
@ -163,21 +168,21 @@ int page_init()
size_t addr, npages;
int i;
// replace default pagefault handler
/* Replace default pagefault handler */
irq_uninstall_handler(14);
irq_install_handler(14, page_fault_handler);
// map kernel
/* Map kernel */
addr = (size_t) &kernel_start;
npages = PAGE_FLOOR((size_t) &kernel_end - (size_t) &kernel_start) >> PAGE_BITS;
page_map(addr, addr, npages, PG_PRESENT | PG_RW | PG_GLOBAL);
#ifdef CONFIG_VGA
// map video memory
/* Map video memory */
page_map(VIDEO_MEM_ADDR, VIDEO_MEM_ADDR, 1, PG_PRESENT | PG_RW | PG_PCD);
#endif
// map multiboot information and modules
/* Map multiboot information and modules */
if (mb_info) {
addr = (size_t) mb_info & PAGE_MASK;
npages = PAGE_FLOOR(sizeof(*mb_info)) >> PAGE_BITS;
@ -197,7 +202,7 @@ int page_init()
}
}
// unmap all (identity mapped) pages with PG_BOOT flag in first PGT (boot_pgt)
/* Unmap bootstrap identity paging (see entry.asm, PG_BOOT) */
for (i=0; i<PAGE_MAP_ENTRIES; i++) {
if (self[0][i] & PG_BOOT) {
self[0][i] = 0;