* Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote: > A couple of Kconfig changes which make it much easier to switch to the > new CONFIG_ORC_UNWINDER: > > 1) Remove x86 dependencies on CONFIG_FRAME_POINTER for lockdep, > latencytop, and fault injection. x86 has a 'guess' unwinder which > just scans the stack for kernel text addresses. It's not 100% > accurate but in many cases it's good enough. This allows those users > who don't want the text overhead of the frame pointer or ORC > unwinders to still use these features. More importantly, this also > makes it much more straightforward to disable frame pointers. > > 2) Make CONFIG_ORC_UNWINDER depend on !CONFIG_FRAME_POINTER. While it > would be possible to have both enabled, it doesn't really make sense > to do so. So enforce a sane configuration to prevent the user from > making a dumb mistake. > > With these changes, when you disable CONFIG_FRAME_POINTER, "make > oldconfig" will ask if you want to enable CONFIG_ORC_UNWINDER. Yeah, so I think this is still suboptimal: the frame pointer and the Orc unwinders are configured in different places, and the user won't know about the various unwinder options unless stumbling across them by accidentally disabling frame pointers ... Also, the Kconfig help text for frame pointers is now actively misleading: CONFIG_FRAME_POINTER: If you say Y here the resulting kernel image will be slightly larger and slower, but it gives very useful debugging information in case of kernel bugs. (precise oopses/stacktraces/warnings) Please, as I suggested it before, make it a multiple choice option: frame, Orc, or the guess unwinder. I'd only offer the 'guess' unwinder if EXPERT is selected, because it's a really sub-optimal selection all things considered. Once things are tested and it's all rosy we can change the default x86 unwinder to Orc and organize the naming of the config variables to: CONFIG_UNWINDER_ORC CONFIG_UNWINDER_FRAME_POINTER CONFIG_UNWINDER_GUESS Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
