On Fri, Jan 8, 2016 at 12:49 PM, Tony Luck <tony.luck(a)intel.com> wrote:
Huge amounts of help from Andy Lutomirski and Borislav Petkov to
produce this. Andy provided the inspiration to add classes to the
exception table with a clever bit-squeezing trick, Boris pointed
out how much cleaner it would all be if we just had a new field.
Linus Torvalds blessed the expansion with:
I'd rather not be clever in order to save just a tiny amount of space
in the exception table, which isn't really criticial for anybody.
The third field is a simple integer indexing into an array of handler
functions (I thought it couldn't be a relative pointer like the other
fields because a module may have its ex_table loaded more than 2GB away
from the handler function - but that may not be actually true. But the
integer is pretty flexible, we are only really using low two bits now).
We start out with three handlers:
0: Legacy - just jumps the to fixup IP
1: Fault - provide the trap number in %ax to the fixup code
2: Cleaned up legacy for the uaccess error hack
I think I preferred the relative function pointer approach.
Also, I think it would be nicer if the machine check code would invoke
the handler regardless of which handler (or class) is selected. Then
the handlers that don't want to handle #MC can just reject them.
Also, can you make the handlers return bool instead of int?