From a42b7d5dbb8b88aa1fb4dc508600a272c494e3f5 Mon Sep 17 00:00:00 2001
From: Frans Kaashoek <kaashoek@mit.edu>
Date: Tue, 2 Oct 2018 08:12:01 -0400
Subject: Simplify freeing page table
---
vm.c | 50 +++++++++++++++++++++++---------------------------
1 file changed, 23 insertions(+), 27 deletions(-)
(limited to 'vm.c')
diff --git a/vm.c b/vm.c
index 4a0c446..9279748 100644
--- a/vm.c
+++ b/vm.c
@@ -81,7 +81,7 @@ walkpgdir(pde_t *pml4, const void *va, int alloc)
*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
@@ -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
// process size. Returns the new process size.
int
-deallocuvm(pde_t *pgdir, uint64 oldsz, uint64 newsz)
+deallocuvm(pde_t *pml4, uint64 oldsz, uint64 newsz)
{
pte_t *pte;
uint64 a, pa;
@@ -303,7 +303,7 @@ deallocuvm(pde_t *pgdir, uint64 oldsz, uint64 newsz)
a = PGROUNDUP(newsz);
for(; a < oldsz; a += PGSIZE){
- pte = walkpgdir(pgdir, (char*)a, 0);
+ pte = walkpgdir(pml4, (char*)a, 0);
if(!pte)
a = PGADDR(PDX(a) + 1, 0, 0) - PGSIZE;
else if((*pte & PTE_P) != 0){
@@ -318,37 +318,33 @@ deallocuvm(pde_t *pgdir, uint64 oldsz, uint64 newsz)
return newsz;
}
-// Free a page table and all the physical memory pages
-// in the user part.
+// Recursively free a page table
+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
freevm(pde_t *pml4, uint64 sz)
{
- uint i, j, k;
- pde_t *pdp, *pd, *pt;
-
if(pml4 == 0)
panic("freevm: no pgdir");
deallocuvm(pml4, sz, 0);
- for(i = 0; i < NPDENTRIES; i++){
- 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);
+ freelevel(pml4, L_PML4);
}
// Clear PTE_U on a page. Used to create an inaccessible
--
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