Simplify inituvm and userinit by assuming initcode fits on a page

f53e6110 · Austin Clements · b3cfd7fc · f53e6110 · f53e6110 · f53e6110
--- a/defs.h
+++ b/defs.h
@@ -160,7 +160,7 @@ char*           uva2ka(pde_t*, char*);
 int             allocuvm(pde_t*, char*, uint);
 int             deallocuvm(pde_t *pgdir, char *addr, uint sz);
 void            freevm(pde_t*);
-void            inituvm(pde_t*, char*, char*, uint);
+void            inituvm(pde_t*, char*, uint);
 int             loaduvm(pde_t*, char*, struct inode *ip, uint, uint);
 pde_t*          copyuvm(pde_t*,uint);
 void            switchuvm(struct proc*);

--- a/proc.c
+++ b/proc.c
@@ -120,11 +120,8 @@ userinit(void)
  initproc = p;
  if(!(p->pgdir = setupkvm()))
    panic("userinit: out of memory?");
-  if(!allocuvm(p->pgdir, 0x0, (int)_binary_initcode_size))
-    panic("userinit: out of memory?");
-  inituvm(p->pgdir, 0x0, _binary_initcode_start,
-          (int)_binary_initcode_size);
-  p->sz = PGROUNDUP((int)_binary_initcode_size);
+  inituvm(p->pgdir, _binary_initcode_start, (int)_binary_initcode_size);
+  p->sz = PGSIZE;
  memset(p->tf, 0, sizeof(*p->tf));
  p->tf->cs = (SEG_UCODE << 3) | DPL_USER;
  p->tf->ds = (SEG_UDATA << 3) | DPL_USER;

--- a/vm.c
+++ b/vm.c
@@ -267,20 +267,14 @@ loaduvm(pde_t *pgdir, char *addr, struct inode *ip, uint offset, uint sz)
 }

 void
-inituvm(pde_t *pgdir, char *addr, char *init, uint sz)
+inituvm(pde_t *pgdir, char *init, uint sz)
 {
-  uint i, pa, n, off;
-  pte_t *pte;
-
-  for(i = 0; i < sz; i += PGSIZE){
-    if(!(pte = walkpgdir(pgdir, (void *)(i+addr), 0)))
-      panic("inituvm: pte should exist\n");
-    off = (i+(uint)addr) % PGSIZE;
-    pa = PTE_ADDR(*pte);
-    if(sz - i < PGSIZE) n = sz - i;
-    else n = PGSIZE;
-    memmove((char *)pa+off, init+i, n);
-  }
+  char *mem = kalloc();
+  if (sz >= PGSIZE)
+    panic("inituvm: more than a page");
+  memset(mem, 0, PGSIZE);
+  mappages(pgdir, 0, PGSIZE, PADDR(mem), PTE_W|PTE_U);
+  memmove(mem, init, sz);
 }

 // given a parent process's page table, create a copy