Exceptions: Take the ExceptionStackFrame per reference #252
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We require/assume that these pointers are correct. Using references is cleaner than blindly dereferencing raw pointers. Important: The Rust book guarantees that: “At runtime, a raw pointer * and a reference pointing to the same piece of data have an identical representation.”
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We now take stack_frame as a immutable reference and we shouldn't write to a &. So the old test example (page faults as breakpoints) becomes even more hacky. Instead, we're now deliberately entering an endless page fault loop to check our iretq logic.
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phil-opp
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phil-opp
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Cherry picked to better_exception_messages and returning_from_exceptions |
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This PR changes the type of exception handler functions. Instead of a
*const ExceptionStackFrame, they now take a&ExceptionStackFrameas argument. The reason is that they require the pointer to be valid (they used to blindly derefence the raw pointer). So the old implementation was unsound, since the functions used to violate memory safety when an invalid pointer is passed.A consequence of this change is that we should no longer modify the exception stack frame (since we have an immutable reference to it). And transmuting a
&to a&mutis undefined behavior. So the last section of Returning from Exceptions (“Page Faults as Breakpoints”) becomes even more hacky. Therefore, this PR removes that section. Instead, we now test the iretq logic by entering an endless loop between the exception handler and the instruction accessing 0xdeadbeaf.