Triple Fault: Difference between revisions
| [unchecked revision] | [unchecked revision] |
Content deleted Content added
Linkfik, removed PFR tag |
m Reverted edits by Greyone (talk) to last revision by Johnburger |
||
| (4 intermediate revisions by 4 users not shown) | |||
Line 6:
==Causes==
When a fault occurs, the CPU invokes an exception handler. If a fault occurs while
Note that a fault that occurs while a fault handler is already running does not of itself cause a double or triple fault. For example, if a Segment Not Present Fault occurs after a handler has already started, then the Segment Not Present handler will run as normal. However, if the code segment of the original handler is itself not Present, then the double (or triple) fault would occur since the original handler hadn't started yet.
This is usually a sign that the exception handler called is faulty, or worse, that the whole exception handling in your system is screwed up. (LDT or GDT issues, bogus pointers or faulty memory mappings are frequent offenders.)▼
▲
Another frequent cause of triple faults is a kernel stack overflow. If the stack reaches an invalid page (one with its present bit clear), a page fault is generated. However, the CPU faults while trying to push the exception information on to the stack, so a double fault is generated. The same problem still exists so a triple fault is generated.
Line 14 ⟶ 16:
==Avoiding==
The cleanest way to handle this is to provide a separate [[Task State Segment|TSS]] for double faults and to use a task gate for that kind of
* display "double fault" panic message
Line 25 ⟶ 27:
On the [[X86-64|AMD64]]/Intel [[EM64T]] architecture, task gates are not valid in 64-bit long mode. The same effect can be achieved through the Interrupt Stack Table bits in the IDT entry. See the Intel manuals for more information.
[[Category:
| |||