Messages in this thread | | | Date | Mon, 30 Aug 2021 21:30:59 +0000 | From | Al Viro <> | Subject | Re: [patch 01/10] x86/fpu/signal: Clarify exception handling in restore_fpregs_from_user() |
| |
On Mon, Aug 30, 2021 at 02:26:12PM -0700, Linus Torvalds wrote: > On Mon, Aug 30, 2021 at 2:07 PM Al Viro <viro@zeniv.linux.org.uk> wrote: > > > > Incidentally, why do we bother with negation in those? Why not have > > user_insn(), XSTATE_OP() and kernel_insn_err() return 0 or trap number... > > I really wish we didn't have that odd _ASM_EXTABLE_FAULT/ > ex_handler_fault() special case at all. > > It's *very* confusing, and it actually seems to be mis-used. It looks > like the "copy_mc_fragile" code uses it by mistake, and doesn't > actually want that "modify %%rax" behavior of that exception handler > AT ALL. > > If I read that code correctly, it almost by mistake doesn't actually > care, and will overwrite %%rax with the right result, but it doesn't > look like the "fault code in %eax" was ever *intentional*. There's no > mention of it. > > Maybe I'm misreading that code, but I look at it and just go "Whaa?" > > The code in user_insn() clearly *does* use that fault number (and, as > you say, inverts it for some reason), but I wonder how much it really > cares? Could we get rid of it, and just set a fixed error code? > > I only checked one user, but that one didn't actually care which fault > it was, it only cared about fault-vs-no-fault.
There's a place where we care about #PF vs. #MC (see upthread)...
| |