2 files changed, 23 insertions, 37 deletions

diff --git a/kernel/api/access.c b/kernel/api/access.c
index 82f03ed..944277c 100644
--- a/kernel/api/access.c
+++ b/kernel/api/access.c
@@ -114,40 +114,21 @@ long user_vecdup(argvec_t *uvec, char ***kvecp)
  * 
  * Check against the vmarea's protections on the mapping. 
  */
-// long addr_perm(proc_t *p, const void *vaddr, int perm)
-// {
-//     // NOT_YET_IMPLEMENTED("vm:: addr_perm");
-
-//     // loop through the vmareas in the process's vmmap
-//     vmarea_t *vma = vmmap_lookup(p->p_vmmap, ADDR_TO_PN(vaddr));
-//     return vma && !!(perm & vma->vma_prot);
-// }
 long addr_perm(proc_t *p, const void *vaddr, int perm)
 {
-    // NOT_YET_IMPLEMENTED("VM: addr_perm");
-    // return 0;
-    vmarea_t *vma = vmmap_lookup(p->p_vmmap, ADDR_TO_PN(vaddr));
-    if (vma == NULL)
-    {
-        return 0;
-    }
-
-    if ((perm & PROT_READ) && !(vma->vma_prot & PROT_READ))
-    {
-        return 0;
-    }
+    // NOT_YET_IMPLEMENTED("vm:: addr_perm");
 
-    if ((perm & PROT_WRITE) && !(vma->vma_prot & PROT_WRITE))
-    {
-        return 0;
-    }
+    // loop through the vmareas in the process's vmmap
+    // vmarea_t *vma = vmmap_lookup(p->p_vmmap, ADDR_TO_PN(vaddr));
+    // return vma && !!(perm & vma->vma_prot);
 
-    if ((perm & PROT_EXEC) && !(vma->vma_prot & PROT_EXEC))
+    vmarea_t *vma = vmmap_lookup(p->p_vmmap, ADDR_TO_PN(vaddr));
+    if (vma == NULL)
     {
         return 0;
     }
 
-    return 1;
+    return (vma->vma_prot & perm) == perm;
 }
 
 
@@ -162,17 +143,16 @@ long addr_perm(proc_t *p, const void *vaddr, int perm)
  */
 long range_perm(proc_t *p, const void *vaddr, size_t len, int perm)
 {
-
-    for (
-        size_t vfn = ADDR_TO_PN(vaddr);
-        vfn < ADDR_TO_PN(PAGE_ALIGN_UP((uintptr_t)vaddr + len));
-        vfn++
-        )
+    // NOT_YET_IMPLEMENTED("vm:: range_perm");
+    size_t start = ADDR_TO_PN(vaddr);
+    size_t end = ADDR_TO_PN(PAGE_ALIGN_UP(vaddr + len));
+    while (start < end)
     {
-        if (!addr_perm(p, PN_TO_ADDR(vfn), perm)) 
+        if (addr_perm(p, PN_TO_ADDR(start), perm) == 0)
         {
             return 0;
         }
+        start++;
     }
     return 1;
 }
diff --git a/kernel/api/syscall.c b/kernel/api/syscall.c
index 7c76e51..c5fea6d 100644
--- a/kernel/api/syscall.c
+++ b/kernel/api/syscall.c
@@ -77,10 +77,11 @@ static long sys_read(read_args_t *args)
     ERROR_OUT_RET(ret);
 
     // Allocate a temporary buffer (a page-aligned block of n pages that are enough space to store the number of bytes to read)
-    size_t size_in_pages = 0;
-    while(++size_in_pages * PAGE_SIZE < kargs.nbytes)
-        ;
-    void *addr = page_alloc_n(size_in_pages);
+    // size_t size_in_pages = 0;
+    // while(++size_in_pages * PAGE_SIZE < kargs.nbytes)
+    //     ;
+    size_t size_in_pages = ADDR_TO_PN(PAGE_ALIGN_UP(kargs.nbytes));
+    char *addr = (char *)page_alloc_n(size_in_pages);
     if (!addr)
     {
         ret = -ENOMEM;
@@ -134,6 +135,11 @@ static long sys_write(write_args_t *args)
     long ret = copy_from_user(&kargs, args, sizeof(kargs));
     ERROR_OUT_RET(ret);
 
+    if (kargs.nbytes == 0)
+    {
+        return 0;
+    }
+    
     // Allocate a temporary buffer (a page-aligned block of n pages that are enough space to store the number of bytes to write)
     size_t size_in_pages = 0;
     while(++size_in_pages * PAGE_SIZE < kargs.nbytes)