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Simplify freeing page table

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This commit is contained in:
Frans Kaashoek 2018-10-02 08:12:01 -04:00
parent 155c13b7f8
commit a42b7d5dbb
2 changed files with 23 additions and 29 deletions
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2
mmu.h
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@ -93,7 +93,6 @@ struct segdesc {
// Page directory and page table constants. // Page directory and page table constants.
#define NPDENTRIES 512 // # directory entries per page directory #define NPDENTRIES 512 // # directory entries per page directory
#define NPTENTRIES 512 // # PTEs per page table
#define PGSIZE 4096 // bytes mapped by a page #define PGSIZE 4096 // bytes mapped by a page
#define PGSHIFT 12 // offset of PTX in a linear address #define PGSHIFT 12 // offset of PTX in a linear address
#define PDXSHIFT 21 // offset of PDX in a linear address #define PDXSHIFT 21 // offset of PDX in a linear address
@ -101,7 +100,6 @@ struct segdesc {
#define PXMASK 0x1FF #define PXMASK 0x1FF
#define PXSHIFT(n) (PGSHIFT+(9*(n))) #define PXSHIFT(n) (PGSHIFT+(9*(n)))
#define PDX(va) (((uint64)(va) >> PDXSHIFT) & PXMASK) #define PDX(va) (((uint64)(va) >> PDXSHIFT) & PXMASK)
#define PTX(va) (((uint64)(va) >> PGSHIFT) & PXMASK)
#define PX(n, va) ((((uint64) (va)) >> PXSHIFT(n)) & PXMASK) #define PX(n, va) ((((uint64) (va)) >> PXSHIFT(n)) & PXMASK)
#define L_PML4 3 #define L_PML4 3

50
vm.c
View file

@ -81,7 +81,7 @@ walkpgdir(pde_t *pml4, const void *va, int alloc)
*pde = V2P(pgtab) | PTE_P | PTE_W | PTE_U; *pde = V2P(pgtab) | PTE_P | PTE_W | PTE_U;
} }
} }
return &pgtab[PTX(va)]; return &pgtab[PX(level, va)];
} }
// Create PTEs for virtual addresses starting at va that refer to // Create PTEs for virtual addresses starting at va that refer to
@ -293,7 +293,7 @@ allocuvm(pde_t *pgdir, uint oldsz, uint newsz)
// need to be less than oldsz. oldsz can be larger than the actual // need to be less than oldsz. oldsz can be larger than the actual
// process size. Returns the new process size. // process size. Returns the new process size.
int int
deallocuvm(pde_t *pgdir, uint64 oldsz, uint64 newsz) deallocuvm(pde_t *pml4, uint64 oldsz, uint64 newsz)
{ {
pte_t *pte; pte_t *pte;
uint64 a, pa; uint64 a, pa;
@ -303,7 +303,7 @@ deallocuvm(pde_t *pgdir, uint64 oldsz, uint64 newsz)
a = PGROUNDUP(newsz); a = PGROUNDUP(newsz);
for(; a < oldsz; a += PGSIZE){ for(; a < oldsz; a += PGSIZE){
pte = walkpgdir(pgdir, (char*)a, 0); pte = walkpgdir(pml4, (char*)a, 0);
if(!pte) if(!pte)
a = PGADDR(PDX(a) + 1, 0, 0) - PGSIZE; a = PGADDR(PDX(a) + 1, 0, 0) - PGSIZE;
else if((*pte & PTE_P) != 0){ else if((*pte & PTE_P) != 0){
@ -318,37 +318,33 @@ deallocuvm(pde_t *pgdir, uint64 oldsz, uint64 newsz)
return newsz; return newsz;
} }
// Free a page table and all the physical memory pages // Recursively free a page table
// in the user part. void
freelevel(pde_t *pgtab, int level) {
int i;
pde_t *pd;
if (level > 0) {
for(i = 0; i < NPDENTRIES; i++) {
if(pgtab[i] & PTE_P){
pd = (pdpe_t*)P2V(PTE_ADDR(pgtab[i]));
freelevel(pd, level-1);
}
}
}
kfree((char*)pgtab);
}
// Free all the physical memory pages
// in the user part and page table
void void
freevm(pde_t *pml4, uint64 sz) freevm(pde_t *pml4, uint64 sz)
{ {
uint i, j, k;
pde_t *pdp, *pd, *pt;
if(pml4 == 0) if(pml4 == 0)
panic("freevm: no pgdir"); panic("freevm: no pgdir");
deallocuvm(pml4, sz, 0); deallocuvm(pml4, sz, 0);
for(i = 0; i < NPDENTRIES; i++){ freelevel(pml4, L_PML4);
if(pml4[i] & PTE_P){
pdp = (pdpe_t*)P2V(PTE_ADDR(pml4[i]));
for(j = 0; j < NPDENTRIES; j++){
if(pdp[j] & PTE_P){
pd = (pde_t*)P2V(PTE_ADDR(pdp[j]));
for(k = 0; k < NPDENTRIES; k++){
if(pd[k] & PTE_P) {
pt = (pde_t*)P2V(PTE_ADDR(pd[k]));
kfree((char*)pt);
}
}
kfree((char*)pd);
}
}
kfree((char*)pdp);
}
}
kfree((char*)pml4);
} }
// Clear PTE_U on a page. Used to create an inaccessible // Clear PTE_U on a page. Used to create an inaccessible