On Fri, Mar 09, 2018 at 07:06:59PM +0100, Andrey Konovalov wrote: > On Mon, Mar 5, 2018 at 3:54 PM, Mark Rutland <mark.rutland@xxxxxxx> wrote: > > On Fri, Mar 02, 2018 at 08:44:33PM +0100, Andrey Konovalov wrote: > >> There are two reasons to use outline instrumentation: > >> 1. Outline instrumentation reduces the size of the kernel text, and should > >> be used where this size matters. > >> 2. Outline instrumentation is less invasive and can be used for debugging > >> for KASAN developers, when it's not clear whether some issue is caused > >> by KASAN or by something else. > >> > >> For the rest cases inline instrumentation is preferrable, since it's > >> faster. > >> > >> This patch changes the default instrumentation mode to inline. > >> --- > >> lib/Kconfig.kasan | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan > >> index ab34e7d7d3a7..8ea6ae26b4a3 100644 > >> --- a/lib/Kconfig.kasan > >> +++ b/lib/Kconfig.kasan > >> @@ -70,7 +70,7 @@ config KASAN_EXTRA > >> choice > >> prompt "Instrumentation type" > >> depends on KASAN > >> - default KASAN_OUTLINE > >> + default KASAN_INLINE > > > > Some compilers don't support KASAN_INLINE, but do support KASAN_OUTLINE. > > IIRC that includes the latest clang release, but I could be wrong. > > > > If that's the case, changing the default here does not seem ideal. > > > > Hi Mark! > > GCC before 5.0 doesn't support KASAN_INLINE, but AFAIU will fallback > to outline instrumentation in this case. > > Latest Clang Release doesn't support KASAN_INLINE (although current > trunk does) and falls back to outline instrumentation. > > So nothing should break, but people with newer compilers should get > the benefits of using the inline instrumentation by default. Ah, ok. I had assumed that they were separate compiler options, and this would result in a build failure. I have no strong feelings either way as to the default. I typically use inline today unless I'm trying to debug particularly weird cases and want to hack the shadow accesses. Thanks, Mark.
