Imbus/xv6-riscv-kernel
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Simplify allocuvm/deallocuvm to operate in a contiguous memory model. This makes their interface match up better with proc->sz and also simplifies the callers (it even gets the main body of exec on one page).

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This commit is contained in:
Austin Clements 2010-09-02 18:28:36 -04:00
parent d49d31381d
commit 79cd8b3eed
4 changed files with 44 additions and 51 deletions
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58
vm.c
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@ -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]));