On 4/26/19 1:05 PM, Sebastian Andrzej Siewior wrote: > > copy_fpstate_to_sigframe() > | > copy_fpregs_to_sigframe() fails. > | > using_compacted_format()
Aw, crud. I was looking at Linus's tree. Sorry about that. In Linus's tree, if copy_fpregs_to_sigframe() fails, we just return from copy_fpstate_to_sigframe() immediately. In other words, either XSAVE works, and we don't have this issue, or XSAVE fails and we don't do the fixup code in question. I'll say it again, though: I think we should be using the XSAVE instruction to save this state. If we need to map some pages in order to make XSAVE work, then I think we should bring some pages in and we can do *that* in the slow path. We can even do that without taking page faults by just calling get_user_pages() for instance. Or, the slow path could be to fpregs_unlock(), zero the user area (taking and handling page faults), then fpregs_lock() and retry the copy_fpregs_to_sigframe().
