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-rw-r--r--vm.c58
1 files changed, 27 insertions, 31 deletions
diff --git a/vm.c b/vm.c
index 0104c3e..5c6f943 100644
--- a/vm.c
+++ b/vm.c
@@ -228,54 +228,50 @@ loaduvm(pde_t *pgdir, char *addr, struct inode *ip, uint offset, uint sz)
return 1;
}
-// Allocate sz bytes more memory for a process starting at the
-// given user address; allocates physical memory and page
-// table entries. addr and sz need not be page-aligned.
-// It is a no-op for any parts of the requested memory
-// that are already allocated.
+// Allocate memory to the process to bring its size from oldsz to
+// newsz. Allocates physical memory and page table entries. oldsz and
+// newsz need not be page-aligned, nor does newsz have to be larger
+// than oldsz. Returns the new process size or 0 on error.
int
-allocuvm(pde_t *pgdir, char *addr, uint sz)
+allocuvm(pde_t *pgdir, uint oldsz, uint newsz)
{
- if(addr + sz > (char*)USERTOP)
+ if(newsz > USERTOP)
return 0;
- char *a = PGROUNDDOWN(addr);
- char *last = PGROUNDDOWN(addr + sz - 1);
- for(; a <= last; a += PGSIZE){
- pte_t *pte = walkpgdir(pgdir, a, 0);
- if(pte == 0 || (*pte & PTE_P) == 0){
- char *mem = kalloc();
- if(mem == 0){
- cprintf("allocuvm out of memory\n");
- deallocuvm(pgdir, addr, sz);
- return 0;
- }
- memset(mem, 0, PGSIZE);
- mappages(pgdir, a, PGSIZE, PADDR(mem), PTE_W|PTE_U);
+ char *a = (char *)PGROUNDUP(oldsz);
+ char *last = PGROUNDDOWN(newsz - 1);
+ for (; a <= last; a += PGSIZE){
+ char *mem = kalloc();
+ if(mem == 0){
+ cprintf("allocuvm out of memory\n");
+ deallocuvm(pgdir, newsz, oldsz);
+ return 0;
}
+ memset(mem, 0, PGSIZE);
+ mappages(pgdir, a, PGSIZE, PADDR(mem), PTE_W|PTE_U);
}
- return 1;
+ return newsz > oldsz ? newsz : oldsz;
}
-// Deallocate some of the user pages. If addr is not page-aligned,
-// then only deallocates starting at the next page boundary.
+// Deallocate user pages to bring the process size from oldsz to
+// newsz. oldsz and newsz need not be page-aligned, nor does 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, char *addr, uint sz)
+deallocuvm(pde_t *pgdir, uint oldsz, uint newsz)
{
- if(addr + sz > (char*)USERTOP)
- return 0;
- char *a = (char *)PGROUNDUP((uint)addr);
- char *last = PGROUNDDOWN(addr + sz - 1);
+ char *a = (char *)PGROUNDUP(newsz);
+ char *last = PGROUNDDOWN(oldsz - 1);
for(; a <= last; a += PGSIZE){
pte_t *pte = walkpgdir(pgdir, a, 0);
if(pte && (*pte & PTE_P) != 0){
uint pa = PTE_ADDR(*pte);
if(pa == 0)
- panic("deallocuvm");
+ panic("kfree");
kfree((void *) pa);
*pte = 0;
}
}
- return 1;
+ return newsz < oldsz ? newsz : oldsz;
}
// Free a page table and all the physical memory pages
@@ -287,7 +283,7 @@ freevm(pde_t *pgdir)
if(!pgdir)
panic("freevm: no pgdir");
- deallocuvm(pgdir, 0, USERTOP);
+ deallocuvm(pgdir, USERTOP, 0);
for(i = 0; i < NPDENTRIES; i++){
if(pgdir[i] & PTE_P)
kfree((void *) PTE_ADDR(pgdir[i]));