Hello Andrew, On 06/18/2019 07:37 AM, Andrew Morton wrote: > On Sat, 15 Jun 2019 10:55:07 +0800 kbuild test robot <lkp@xxxxxxxxx> wrote: > >> tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master >> head: f4788d37bc84e27ac9370be252afb451bf6ef718 >> commit: 4dd635bce90e8b6ed31c08cd654deca29f4d9d66 [6470/6646] mm, kprobes: generalize and rename notify_page_fault() as kprobe_page_fault() >> config: mips-allmodconfig (attached as .config) >> compiler: mips-linux-gcc (GCC) 7.4.0 >> reproduce: >> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross >> chmod +x ~/bin/make.cross >> git checkout 4dd635bce90e8b6ed31c08cd654deca29f4d9d66 >> # save the attached .config to linux build tree >> GCC_VERSION=7.4.0 make.cross ARCH=mips >> >> If you fix the issue, kindly add following tag >> Reported-by: kbuild test robot <lkp@xxxxxxxxx> >> >> All errors (new ones prefixed by >>): >> >> In file included from net//sctp/offload.c:11:0: >> include/linux/kprobes.h: In function 'kprobe_page_fault': >>>> include/linux/kprobes.h:477:9: error: implicit declaration of function 'kprobe_fault_handler'; did you mean 'kprobe_page_fault'? [-Werror=implicit-function-declaration] >> return kprobe_fault_handler(regs, trap); > > Urgh, OK, thanks. > > kprobe_fault_handler() is only ever defined and referenced in arch code > and generic code has no right to be assuming that the architecture > actually provides it. And so it is with mips (at least). Hmm, so the problem really is that on mips arch even though CONFIG_KPROBES is enabled, it does not export (though it defines) a kprobe_fault_handler() implementation unlike all other architectures. Now that generic code calls kprobe_fault_handler(), should not all arch be providing one when they subscribe to CONFIG_KPROBES ? In which case mips should just export it's existing definition to fix this build problem. > > The !CONFIG_KPROBES stub version of kprobe_fault_handler() should not > have been placed in include/linux/kprobes.h! Each arch should have > defined its own, if that proved necessary. I guess its there in include/linux/kprobes.h! because !CONFIG_KPROBES stub version for all archs will exactly look the same. > > Oh well, ho hum. Hopefully Anshuman will be able to come up with a fix > for mips and any similarly-affected architectures. Will export it's existing definition via arch/mips/include/asm/kprobes.h unless that is problematic for other reasons. Another solution would be to define an weak symbol in include/linux/kprobes.h for CONFIG_KPROBES. But that will not be correct because kprobe_fault_handler() by all means is always platform specific. > > Also, please very carefully check that this patchset is correct for all > architectures! kprobe_fault_handler() could conceivably do different > things on different architectures. Agreed.
