On Tue, Dec 13, 2016 at 2:59 PM, Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> wrote: > On 12/13/2016 12:38 PM, Dmitry Vyukov wrote: >> On Tue, Dec 13, 2016 at 10:20 AM, Andrey Ryabinin >> <aryabinin@xxxxxxxxxxxxx> wrote: >>> >>> >>> On 12/13/2016 11:58 AM, Dmitry Vyukov wrote: >>> >>>> --- a/Documentation/dev-tools/kasan.rst >>>> +++ b/Documentation/dev-tools/kasan.rst >>>> @@ -40,6 +40,14 @@ similar to the following to the respective kernel Makefile: >>>> >>>> KASAN_SANITIZE := n >>>> >>>> +Sometimes it may be useful to disable instrumentation of reads, or writes >>>> +or both for the entire kernel. For example, if binary size is a concern, >>>> +it may be useful to disable instrumentation of reads to reduce binary size but >>>> +still catch more harmful bugs on writes. Or, if one is interested only in >>>> +sanitization of a particular module and performance is a concern, she can >>>> +disable instrumentation of both reads and writes for kernel code. >>>> +Instrumentation can be disabled with CONFIG_KASAN_READS and >>>> CONFIG_KASAN_WRITES. >>>> + >>> >>> I don't understand this. How this can be related to modules? Configs are global. >>> You can't just disable/enable config per module. >> >> >> Build everything without instrumentation. Then enable instrumentation >> and do "make lib/test_kasan.ko". >> Or build everything, copy out bzImage, change config, build everything again. > > Yeah, this is soooooo convenient... > > Seriously speaking, per-file instrumentation is absolutely irrelevant to this patch and should have been > addressed from a different angle. E.g. see how UBSAN/GCOV/KCOV do that. KASAN already has that functionality (i.e. KASAN_SANITIZE_main.o := n). But that functionality is intended for cases when we want to persistently disable instrumentation of some files (e.g. if they cause crashes of false positives). CONFIG_KASAN_READS/WRITES is intended for situations when one wants to disable instrumentation wholesale. > As for this patch, I'd say only one option would be enough - KASAN_DONT_SANITIZE_READS. > Nobody wants to sanitize only reads without writes, right? Writes are fewer and more dangerous. I've asked this question in v1. See the case related to modules -- one can use completely uninstrumented kernel, but load an instrumented modules. -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
