On Mon, Jan 27, 2014 at 02:43:14PM -0800, Linus Torvalds wrote: > On Mon, Jan 27, 2014 at 2:32 PM, Al Viro <v...@zeniv.linux.org.uk> wrote: > > > > do_signal() is also a place where arbitrary changes to regs might've > > been done by tracer, so regs->cs might need to be checked in the same > > place where we validate regs->rip ;-/ > > Fair enough. But it would still be really easy, and make the common > case signal delivery a bit faster. > > Now, sadly, most signal delivery is then followed by sigreturn (the > exceptions being dying or doing a longjmp), so we'd still get the > iretq then. But it would cut the iretq's related to signals in half. > > We *could* try to do sigreturn with sysret and a small trampoline too, > of course. But I'm not sure how far I'd want to take it.
The problem with validation is that we'll suddenly become sensitive to hard-to-estimate pile of hardware bugs ;-/ E.g. which AMD-specific errata is that comment in entry_64.S about? The one I kinda-sorta remember is Intel-specific, and that was about uncanonical RIP; looking for AMD one has turned #353 (with suggested workaround being "have bit 16 set in whatever you put into R11"), but I've no idea whether that's the only potential issue there... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/