fixes to work on dept machine

1 files changed, 44 insertions, 37 deletions

diff --git a/kernel/vm/pagefault.c b/kernel/vm/pagefault.c
index b289537..39e5776 100644
--- a/kernel/vm/pagefault.c
+++ b/kernel/vm/pagefault.c
@@ -49,80 +49,87 @@ 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");
 
-    // 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)
+    // Check that the vaddr is valid
+    if (vaddr < USER_MEM_LOW) 
     {
         do_exit(EFAULT);
     }
-    // lookup the vmarea for this addr
-    vmarea_t *vma = vmmap_lookup(curproc->p_vmmap, ADDR_TO_PN(vaddr));
-    if (vma == NULL)
+    if (vaddr > USER_MEM_HIGH) 
     {
         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))
+    // Lookup the vmarea for this address
+    size_t pn = ADDR_TO_PN(vaddr);
+    vmarea_t* vma = vmmap_lookup(curproc->p_vmmap, pn);
+    if (!vma) 
     {
         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))
+
+    // Error out if we don't have any permission in the area
+    if (vma->vma_prot == PROT_NONE) 
     {
         do_exit(EFAULT);
     }
-    // error out if we don't have read permission in the area
-    if (!(vma->vma_prot & PROT_READ))
+
+    // Check the vmarea's protections (see the vmarea_t struct) against the 'cause' of the pagefault
+    if ((cause & FAULT_WRITE) && !(vma->vma_prot & PROT_WRITE)) 
     {
         do_exit(EFAULT);
-    }
-    // error our if we don't have any permission in the area
-    if (vma->vma_prot == PROT_NONE)
+    } 
+    else if ((cause & FAULT_EXEC) && !(vma->vma_prot & PROT_EXEC)) 
+    {
+        do_exit(EFAULT);
+    } 
+    else if (!(vma->vma_prot & PROT_READ)) 
     {
         do_exit(EFAULT);
     }
 
-    // 3) Obtain the corresponding pframe from the vmarea's mobj.
-    pframe_t *pf;
+    // Obtain the corresponding pframe from the vmarea's mobj
+    long forwrite = 0;
+    if (cause & FAULT_WRITE) 
+    {
+        forwrite = 1;
+    }
+    pframe_t* pfp;
     mobj_lock(vma->vma_obj);
-    int ret = mobj_get_pframe(
+    long status = mobj_get_pframe(
         vma->vma_obj, 
-        vma->vma_off + ADDR_TO_PN(vaddr) - vma->vma_start, 
-        cause & FAULT_WRITE ? 1 : 0,
-        &pf
+        pn - vma->vma_start + vma->vma_off,
+        forwrite, 
+        &pfp
     );
     mobj_unlock(vma->vma_obj);
-    if (ret < 0)
+    if (status < 0) 
     {
         do_exit(EFAULT);
     }
 
-    // 4) Finally, set up a call to pt_map to insert a new mapping into the appropriate pagetable
-    uintptr_t paddr = pt_virt_to_phys(pf->pf_addr);
-    pframe_release(&pf);
-    int pdflags = PT_PRESENT | PT_WRITE | PT_USER;
-    int ptflags = PT_PRESENT | PT_USER;
-    if (cause & FAULT_WRITE)
+    // Set up a call to pt_map to insert a new mapping into the appropriate pagetable
+    uintptr_t paddr = pt_virt_to_phys((uintptr_t) pfp->pf_addr);
+    pframe_release(&pfp);
+    uint32_t ptflags = PT_PRESENT | PT_USER;
+    if (cause & FAULT_WRITE) 
     {
         ptflags |= PT_WRITE;
     }
-
-    int err = pt_map(
+    status = pt_map(
         curproc->p_pml4, 
-        paddr,
-        (uintptr_t) PAGE_ALIGN_DOWN(vaddr),
-        pdflags, 
+        paddr, 
+        (uintptr_t) PAGE_ALIGN_DOWN(vaddr), 
+        PT_PRESENT | PT_USER | PT_WRITE,
         ptflags
     );
-    if (err < 0)
+    if (status < 0) 
     {
         do_exit(EFAULT);
     }
 
-    // 5) Flush the TLB
-    tlb_flush((uintptr_t) PAGE_ALIGN_DOWN(vaddr));
+    // Flush the TLB
+    tlb_flush(vaddr);
 }