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| | 22C:116, Midterm, Spring 1999 |
 | | The Problem: What test should be done by the code for a system call such as read(f,buffer,len) to verify that it is reading into a buffer the user is allowed to manipulate, and not, for example, reading from the keyboard into the memory currently occupied by a system data structure such as the page table. |
 | | If one of those parameters is pointer passed by the user to the system, for example the buffer address passed to a a function such as read, the user must pass a virtual address. |
 | | The Problem: How could kernel code on the Hawk machine call a user function (this is modestly easy), and how would the kernel regain control when the user function attempted to return (this is a little harder!). |
| www.cs.uiowa.edu /~jones/opsys/spring99/hw/midterm.html (1323 words) |
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