On Sun, Dec 27, 2015 at 5:33 AM, Borislav Petkov <bp@xxxxxxxxx> wrote: > On Sun, Dec 27, 2015 at 05:25:45AM -0800, Andy Lutomirski wrote: >> That could significantly bloat the kernel image. > > Yeah, we probably should build an allyesconfig and see how big > __ex_table is and compute how much actually that bloat would be, > because... > >> Anyway, the bit 31 game isn't so bad IMO because it's localized to the >> extable macros and the extable reader, whereas the bit 63 thing is all >> tangled up with the __mcsafe_copy thing, and that's just the first >> user of a more general mechanism. >> >> Did you see this: >> >> https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=strict_uaccess_fixups/patch_v1&id=16644d9460fc6531456cf510d5efc57f89e5cd34 > > ... the problem this has is that you have 4 classes, AFAICT. And since > we're talking about a generic mechanism, the moment the 4 classes are > not enough, this new scheme fails. > > I'm just saying... > > 4 classes are probably more than enough but we don't know. On whatever kernel I just built (defconfig-ish), __ex_table is about 12kB, so the bloat would be 6 kB. In any case, I can think of a total of three useful classes: 0: normal 1: extended (indirect block with fanciness, as I proposed) 2: uaccess (some day, not yet) For rare future things, we could shoehorn them into the extended version's indirect block. Or someone could think of a clever encoding that makes this work better. --Andy -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>