soft page faults, seems like fork is buggy though

550d1798 · Nickolai Zeldovich · 0d19e203 · 550d1798 · 550d1798 · 550d1798
--- a/defs.h
+++ b/defs.h
@@ -169,11 +169,11 @@ struct vmap *   vmap_copy(struct vmap *);
 int             allocuvm(pde_t*, uint, uint);
 int             deallocuvm(pde_t*, uint, uint);
 void            freevm(pde_t*);
-pde_t*          copyuvm(pde_t*, uint);
 void            switchuvm(struct proc*);
 void            switchkvm(void);
 int             copyout(struct vmap *, uint, void*, uint);
 int             copyin(struct vmap *, uint, void*, uint);
+int             pagefault(pde_t*, struct vmap *, uint);
 // number of elements in fixed-size array
 #define NELEM(x) (sizeof(x)/sizeof((x)[0]))
--- a/proc.c
+++ b/proc.c
@@ -86,7 +86,7 @@ userinit(void)
    panic("userinit: out of memory?");
  if((p->vmap = vmap_alloc()) == 0)
    panic("userinit: out of vmaps?");
-  struct vmnode *vmn = vmn_allocpg(PGROUNDUP((int)_binary_initcode_size));
+  struct vmnode *vmn = vmn_allocpg(PGROUNDUP((int)_binary_initcode_size) / PGSIZE);
  if(vmn == 0)
    panic("userinit: vmn_allocpg");
  if(vmap_insert(p->vmap, vmn, 0) < 0)

--- a/syscall.c
+++ b/syscall.c
@@ -16,7 +16,7 @@
 int
 fetchint(struct proc *p, uint addr, int *ip)
 {
-#if 0 /* XXX */
+#if 0 /* XXX use pagefault() */
  if(addr >= p->sz || addr+4 > p->sz)
    return -1;
 #endif
@@ -32,12 +32,12 @@ fetchstr(struct proc *p, uint addr, char **pp)
 {
  char *s, *ep;
-#if 0 /* XXX */
+#if 0 /* XXX use pagefault() */
  if(addr >= p->sz)
    return -1;
 #endif
  *pp = (char*)addr;
-#if 0 /* XXX */
+#if 0 /* XXX use pagefault() */
  ep = (char*)p->sz;
 #else
  ep = (char *) 0xffffffff;
@@ -65,7 +65,7 @@ argptr(int n, char **pp, int size)
  if(argint(n, &i) < 0)
    return -1;
-#if 0 /* XXX */
+#if 0 /* XXX use pagefault() */
  if((uint)i >= proc->sz || (uint)i+size > proc->sz)
    return -1;
 #endif

--- a/trap.c
+++ b/trap.c
@@ -45,6 +45,16 @@ trap(struct trapframe *tf)
    return;
  }
+  if(tf->trapno == T_PGFLT){
+    cprintf("[%d] page fault for %x\n", cpunum(), rcr2());
+    if(pagefault(proc->pgdir, proc->vmap, rcr2()) >= 0){
+      cprintf("[%d] xxx1\n", cpunum());
+      switchuvm(proc);
+      return;
+    }
+    cprintf("[%d] xxx2\n", cpunum());
+  }
  switch(tf->trapno){
  case T_IRQ0 + IRQ_TIMER:
    if(cpu->id == 0){

--- a/vm.c
+++ b/vm.c
@@ -210,8 +210,10 @@ struct vmnode *
 vmn_allocpg(uint npg)
 {
  struct vmnode *n = vmn_alloc();
-  if(npg > sizeof(n->page) / sizeof(n->page[0]))
+  if(npg > sizeof(n->page) / sizeof(n->page[0])) {
-    panic("vmnode too big");
+    cprintf("vmnode too big: %d\n", npg);
+    return 0;
+  }
  for(uint i = 0; i < npg; i++) {
    if((n->page[i] = kalloc()) == 0) {
      vmn_free(n);
@@ -429,37 +431,6 @@ freevm(pde_t *pgdir)
  kfree((char*)pgdir);
 }
-// Given a parent process's page table, create a copy
-// of it for a child.
-pde_t*
-copyuvm(pde_t *pgdir, uint sz)
-{
-  pde_t *d;
-  pte_t *pte;
-  uint pa, i;
-  char *mem;
-  if((d = setupkvm()) == 0)
-    return 0;
-  for(i = 0; i < sz; i += PGSIZE){
-    if((pte = walkpgdir(pgdir, (void*)i, 0)) == 0)
-      panic("copyuvm: pte should exist");
-    if(!(*pte & PTE_P))
-      panic("copyuvm: page not present");
-    pa = PTE_ADDR(*pte);
-    if((mem = kalloc()) == 0)
-      goto bad;
-    memmove(mem, (char*)pa, PGSIZE);
-    if(mappages(d, (void*)i, PGSIZE, PADDR(mem), PTE_W|PTE_U) < 0)
-      goto bad;
-  }
-  return d;
-bad:
-  freevm(d);
-  return 0;
-}
 //PAGEBREAK!
 // Map user virtual address to kernel physical address.
 char*
@@ -528,3 +499,28 @@ copyin(struct vmap *vmap, uint va, void *p, uint len)
  }
  return 0;
 }
+int
+pagefault(pde_t *pgdir, struct vmap *vmap, uint va)
+{
+  cprintf("pagefault\n");
+  pte_t *pte = walkpgdir(pgdir, (const void *)va, 1);
+  cprintf("pagefault: 0\n");
+  if((*pte & (PTE_P|PTE_U|PTE_W)) == (PTE_P|PTE_U|PTE_W)) {
+    cprintf("pagefault: 1\n");
+    return 0;
+  }
+  cprintf("pagefault: 1.1\n");
+  struct vma *m = vmap_lookup(vmap, va);
+  if(m == 0) {
+    cprintf("pagefault: 2\n");
+    return -1;
+  }
+  cprintf("pagefault: 3\n");
+  uint npg = (PGROUNDDOWN(va) - m->va_start) / PGSIZE;
+  *pte = PADDR(m->n->page[npg]) | PTE_P | PTE_U | PTE_W;
+  release(&m->lock);
+  return 1;
+}