Currently the default instrumentation mode is outline. Switch to inline as the default mode, but make sure that older compilers (the ones that don't support inline instrumentation, both GCC and Clang) automatically switch to the outline mode (via $(cc-option, ...) in Kconfig.kasan?).
AFAICT, the versions of GCC and clang which are supported by the kernel all support inline instrumentation by now. So, there would be no need to make a distinction. Or am I missing something? Would you still welcome a patch making inline instrumentation the default?
Outline instrumentation leads to smaller code size, and IIRC some arches support only outline. But making inline the default sounds good.
On PowerPC, inline instrumentation will be disabled if PPC_RADIX_MMU is set. But Kconfig will already take care of disabling inline instrumentation in that case. That's the only arch I could find where this is relevant. I'll be submitting a patch then. Thanks!