Messages in this thread | | | From | Andy Lutomirski <> | Date | Fri, 8 Jan 2016 17:52:54 -0800 | Subject | Re: [PATCH v8 1/3] x86: Expand exception table to allow new handling options |
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On Fri, Jan 8, 2016 at 12:49 PM, Tony Luck <tony.luck@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?
--Andy
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