1 files changed, 74 insertions, 1 deletions
diff --git a/kernel/vm/pagefault.c b/kernel/vm/pagefault.c
index 764ce85..2e0c92d 100644
--- a/kernel/vm/pagefault.c
+++ b/kernel/vm/pagefault.c
@@ -49,5 +49,78 @@ void handle_pagefault(uintptr_t vaddr, uintptr_t cause)
 {
     dbg(DBG_VM, "vaddr = 0x%p (0x%p), cause = %lu\n", (void *)vaddr,
         PAGE_ALIGN_DOWN(vaddr), cause);
-    NOT_YET_IMPLEMENTED("VM: handle_pagefault");
+    // NOT_YET_IMPLEMENTED("VM: handle_pagefault");
+
+    // 1) Find the vmarea that contains vaddr, if it exists.
+    // check that the vaddr is valid
+    if (vaddr < USER_MEM_LOW || vaddr > USER_MEM_HIGH)
+    {
+        do_exit(EFAULT);
+    }
+    // lookup the vmarea for this addr
+    vmarea_t *vma = vmmap_lookup(curproc->p_vmmap, ADDR_TO_PN(vaddr));
+    if (vma == NULL)
+    {
+        do_exit(EFAULT);
+    }
+
+    // 2) Check the vmarea's protections (see the vmarea_t struct) against the 'cause'
+    // error out if the fault has cause write and we don't have write permission in the area
+    if ((cause & FAULT_WRITE) && !(vma->vma_prot & PROT_WRITE))
+    {
+        do_exit(EFAULT);
+    }
+    // error out if the fault has cause exec and we don't have exec permission in the area
+    if ((cause & FAULT_EXEC) && !(vma->vma_prot & PROT_EXEC))
+    {
+        do_exit(EFAULT);
+    }
+    // error out if we don't have read permission in the area
+    if (!(vma->vma_prot & PROT_READ))
+    {
+        do_exit(EFAULT);
+    }
+    // error our if we don't have any permission in the area
+    if (vma->vma_prot == PROT_NONE)
+    {
+        do_exit(EFAULT);
+    }
+
+    // 3) Obtain the corresponding pframe from the vmarea's mobj.
+    pframe_t *pf;
+    mobj_lock(vma->vma_obj);
+    int ret = mobj_get_pframe(
+        vma->vma_obj, 
+        vma->vma_off + (ADDR_TO_PN(vaddr) - vma->vma_start), 
+        cause & FAULT_WRITE ? 1 : 0,
+        &pf
+    );
+    mobj_unlock(vma->vma_obj);
+    if (ret < 0)
+    {
+        do_exit(EFAULT);
+    }
+
+    // 4) Finally, set up a call to pt_map to insert a new mapping into the appropriate pagetable
+    int pdflags = PT_PRESENT | PT_WRITE | PT_USER;
+    int ptflags = PT_PRESENT | PT_USER;
+    if (cause & FAULT_WRITE)
+    {
+        ptflags |= PT_WRITE;
+    }
+
+    int err = pt_map(
+        curproc->p_pml4, 
+        pt_virt_to_phys((uintptr_t) pf->pf_addr), 
+        (uintptr_t) PAGE_ALIGN_DOWN(vaddr),
+        pdflags, 
+        ptflags
+    );
+    if (err < 0)
+    {
+        do_exit(EFAULT);
+    }
+
+    // 5) Flush the TLB
+    tlb_flush((uintptr_t) PAGE_ALIGN_DOWN(vaddr));
 }