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static pages shared in all procs; last page diff; free dir updated
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@u7karsh
u7karsh committed Nov 24, 2018
1 parent 9c97bd9 commit 1252d0d
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Showing 3 changed files with 52 additions and 33 deletions.
3 changes: 3 additions & 0 deletions xinu/include/paging.h
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Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,8 @@ typedef struct {
unsigned int pdbr_base : 20; /* location of page directory? */
} pdbr_t;

extern bool8 paging_static_created;

/* Macros */

#define PAGE_SIZE 4096 /* number of bytes per page */
Expand All @@ -67,5 +69,6 @@ typedef struct {
#define MAX_SWAP_SIZE 4096 /* size of swap space (in frames) */
#define MAX_FSS_SIZE 2048 /* size of FSS space (in frames) */
#define MAX_PT_SIZE 256 /* size of space used for page tables (in frames) */
#define N_PAGE_ENTRIES 1024

#endif
1 change: 1 addition & 0 deletions xinu/include/prototypes.h
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Original file line number Diff line number Diff line change
Expand Up @@ -622,6 +622,7 @@ extern void init_paging(void);
/* in file paging.c */
extern pdbr_t create_directory(void);
extern void destroy_directory(pdbr_t);
extern uint32 create_pagetable(uint32, uint32);

extern unsigned long read_cr0(void);
extern unsigned long read_cr2(void);
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81 changes: 48 additions & 33 deletions xinu/system/paging.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@

void *minpdpt;
void *maxpdpt;
bool8 paging_static_created;

/*------------------------------------------------------------------------
* pdptinit - initialize directory/table free list
Expand Down Expand Up @@ -159,19 +160,15 @@ syscall freepdptframe(uint32 frame){
return _freemem(&pdptlist, blkaddr, PAGE_SIZE, minpdpt, maxpdpt);
}



pdbr_t create_directory(){
pdbr_t pdbr;
uint32 dirframeno;
uint32 i;
uint32 j;
uint32 *diruint;
uint32 npages;
uint32 nentries;
uint32 ptbase;
pd_t *pd;
pt_t *pt;
pd_t *nullprocdir;

dirframeno = getpdptframe();
diruint = (uint32*)(dirframeno << PAGE_OFFSET_BITS);
Expand All @@ -185,33 +182,15 @@ pdbr_t create_directory(){
pdbr.pdbr_base = dirframeno;

// Zero all 1k entries
for( i = 0; i < 1024; i++ ){
for( i = 0; i < N_PAGE_ENTRIES; i++ ){
diruint[i] = 0;
}

// Allocate bare minimum pages
// Allocate bare minimum pages a.k.a flat mapping
npages = ceil( ((uint32)maxpdpt), PAGE_SIZE );
nentries = ceil( npages, 1024 );
nentries = ceil( npages, N_PAGE_ENTRIES );
for( i = 0; i < nentries; i++ ){
ptbase = getpdptframe();
pt = (pt_t*)(ptbase << PAGE_OFFSET_BITS);
for( j = 0; j < 1024; j++ ){
pt[j].pt_pres = 1; /* page is present? */
pt[j].pt_write = 1; /* page is writable? */
pt[j].pt_user = 0; /* is use level protection? */
pt[j].pt_pwt = 0; /* write through for this page? */
pt[j].pt_pcd = 1; /* cache disable for this page? */
pt[j].pt_acc = 0; /* page was accessed? */
pt[j].pt_dirty = 0; /* page was written? */
pt[j].pt_mbz = 0; /* must be zero */
pt[j].pt_global = 0; /* should be zero in 586 */
pt[j].pt_avail = 0; /* for programmer's use */
// TODO: Akshay
pt[j].pt_base = (i*1024 + j); /* location of page? */
}

pd = (pd_t*)&diruint[i];

pd->pd_pres = 1; /* page table present? */
pd->pd_write = 1; /* page is writable? */
pd->pd_user = 0; /* is use level protection? */
Expand All @@ -222,16 +201,47 @@ pdbr_t create_directory(){
pd->pd_fmb = 0; /* four MB pages? */
pd->pd_global = 0; /* global (ignored) */
pd->pd_avail = 0; /* for programmer's use */
pd->pd_base = ptbase; /* location of page table? */

// Logic to share static page table amongst all processes
if( paging_static_created == TRUE && (i != nentries - 1) ){
// Steal the entries from nullproc
nullprocdir = (pd_t*)((uint32)(proctab[0].pdbr.pdbr_base) << PAGE_OFFSET_BITS);
pd->pd_base = nullprocdir[i].pd_base;
} else{
pd->pd_base = create_pagetable(i, (i == nentries - 1) ? npages % N_PAGE_ENTRIES : N_PAGE_ENTRIES); /* location of page table? */
}
}

paging_static_created = TRUE;
return pdbr;
}

// TODO: Extend from flat mapping
uint32 create_pagetable(uint32 index, uint32 nentries){
uint32 ptbase = getpdptframe();
pt_t *pt = (pt_t*)(ptbase << PAGE_OFFSET_BITS);
int i;

for( i = 0; i < N_PAGE_ENTRIES; i++ ){
pt[i].pt_pres = (i < nentries) ? 1 : 0; /* page is present? */
pt[i].pt_write = 1; /* page is writable? */
pt[i].pt_user = 0; /* is use level protection? */
pt[i].pt_pwt = 0; /* write through for this page? */
pt[i].pt_pcd = 1; /* cache disable for this page? */
pt[i].pt_acc = 0; /* page was accessed? */
pt[i].pt_dirty = 0; /* page was written? */
pt[i].pt_mbz = 0; /* must be zero */
pt[i].pt_global = 0; /* should be zero in 586 */
pt[i].pt_avail = 0; /* for programmer's use */
pt[i].pt_base = (index*N_PAGE_ENTRIES + i); /* location of page? */
}
return ptbase;
}

void print_page(pd_t pd){
int i;
uint32* page = (uint32*)(pd.pd_base << PAGE_OFFSET_BITS);
for( i = 0; i < 1024; i++ ){
for( i = 0; i < N_PAGE_ENTRIES; i++ ){
if( page[i] & 0x1 ){
kprintf(" %08d: 0x%08X\n", i, page[i]);
}
Expand All @@ -242,20 +252,24 @@ void print_directory(pdbr_t pdbr){
int i;
uint32* dir = (uint32*)(pdbr.pdbr_base << PAGE_OFFSET_BITS);
kprintf("PDBR: %08X\n", *((pdbr_t*)&pdbr));
for( i = 0; i < 1024; i++ ){
for( i = 0; i < N_PAGE_ENTRIES; i++ ){
if( dir[i] & 0x1 ){
kprintf("%08d: 0x%08X\n", i, dir[i]);
}
}
}

void destroy_directory(pdbr_t pdbr){
uint32 dirno = pdbr.pdbr_base;
pd_t *frame = (pd_t*)(dirno << PAGE_OFFSET_BITS);
uint32 dirno = pdbr.pdbr_base;
pd_t *frame = (pd_t*)(dirno << PAGE_OFFSET_BITS);
uint32 npages = ceil( ((uint32)maxpdpt), PAGE_SIZE );
uint32 nentries = ceil( npages, N_PAGE_ENTRIES );
int i;

// Free all pages
for( i = 0; i < 1024; i++ ){
// No need to free static pages as they are shared and nullproc
// allocated them
// As nullproc will never be freed, no need to free it
for( i = nentries - 1; i < N_PAGE_ENTRIES; i++ ){
if( frame[i].pd_pres == TRUE ){
freepdptframe(frame[i].pd_base);
}
Expand All @@ -268,6 +282,7 @@ void destroy_directory(pdbr_t pdbr){
void init_paging(){
// Init PD/PT
__init( &pdptlist, (char*)((uint32)maxheap + 1), PAGE_SIZE * MAX_PT_SIZE, &minpdpt, &maxpdpt );
paging_static_created = FALSE;
/* Set interrupt vector for the pagefault to invoke pagefault_handler_disp */
set_evec(IRQPAGE, (uint32)pagefault_handler_disp);
//enable_paging();
Expand Down

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