Finish lab 5.

lib/file.c

@@ -141,7 +141,13 @@ devfile_write(struct Fd *fd, const void *buf, size_t n)
 	// remember that write is always allowed to write *fewer*
 	// bytes than requested.
 	// LAB 5: Your code here
-	panic("devfile_write not implemented");
+	size_t writesize = MIN(sizeof(fsipcbuf.write.req_buf), n);
+
+	fsipcbuf.write.req_fileid = fd->fd_file.id;
+	fsipcbuf.write.req_n = writesize;
+	memcpy(fsipcbuf.write.req_buf, buf, writesize);
+
+	return fsipc(FSREQ_WRITE, NULL);
 }
 
 static int

lib/fork.c

@@ -62,7 +62,7 @@ duppage(envid_t envid, unsigned pn)
 	void* addr = (void*) (pn * PGSIZE);
 
 	// If we're writable, remove write permission
-	if((new_pte & PTE_W) || (new_pte & PTE_COW)) {
+	if(((new_pte & PTE_W) && !(new_pte & PTE_SHARE)) || (new_pte & PTE_COW)) {
 		perms = (perms & ~PTE_W) | PTE_COW;
 		change_own = true;
 	}

lib/spawn.c

@@ -302,6 +302,21 @@ static int
 copy_shared_pages(envid_t child)
 {
 	// LAB 5: Your code here.
+	int r;
+	for(int pde_i = 0; pde_i < PDX(UTOP); pde_i++) {
+		pde_t pde = uvpd[pde_i];
+		if(!(pde & PTE_P)) continue;
+
+		for(int pte_i = 0; pte_i < NPTENTRIES; pte_i++) {
+			int pn = pde_i * NPTENTRIES + pte_i;
+			pte_t pte = uvpt[pn];
+
+			if((pte & (PTE_P | PTE_SHARE)) != (PTE_P | PTE_SHARE)) continue;
+			void* addr = (void*) (pn * PGSIZE);
+			if((r = sys_page_map(0, addr, child, addr, pte & PTE_SYSCALL)) < 0)
+				return r;
+		}
+	}
 	return 0;
 }