[PATCHv4] Enable -fsanitize-recover for KASan

[Yury Gribov]

On 10/23/2014 03:10 PM, Andrey Ryabinin wrote:
> On 10/23/2014 02:38 PM, Jakub Jelinek wrote:
>> On Thu, Oct 23, 2014 at 02:33:42PM +0400, Yury Gribov wrote:
>>> Actually this is a historical artifact.  If inlining proves to be
>>> significantly faster, they may want to switch.
>>
>> Ok.
>>
>>>> So, at that point you can include your ugly hacks in __asan_load* logic in
>>>> the kernel, the difference between __asan_load4 and __asan_load4_noabort
>>>> will be just that the latter will always return, while the former will not
>>>> if some error has been reported.
>>>> All the __asan_load* and __asan_store* entrypoints, regardless of
>>>> -f{,no-}sanitize-recover=kernel-address are by definition not noreturn, they
>>>> in the common case (if the code is not buggy) return.
>>>
>>> Perhaps we should just keep __asan_load* as is and leave the decision
>>> whether to abort or continue for the runtime?  This would make semantics of
>>> -fsanitize-recover cumbersome though (because it wouldn't work if user
>>> selects outline instrumentation).
>>
>> Well, the "don't ever report anything while some per-CPU flag is set" thing
>> can be considered as part of the "is this memory access ok" test, it is
>> pretending everything is accessible.
>>
>> But, otherwise, if it is supposed to be developer's decision at compile
>> time, __asan_load*_noabort should better always continue, even if it
>> reported issues, and __asan_load* should better not return after reporting
>> errors.
>>
>
> True, but why we need new functions for that.
> __asan_load could also abort or not depending on what user/developer wants.
> Why we have to rebuild the entire kernel if someone wants to switch from abort to noabort?
>
> I'm not against __asan_load_noabort, I'm just saying that this is no point to have separate
> __asan_load/__asan_load_noabort functions in kernel.

I'd still suggest to emit __asan_load_noabort so that we match userspace 
(where __asan_load strictly matches __asan_report in terminating the 
program).  Behavior of __asan_load_noabort can further be restricted by 
user via various environment settings (kernel parameters, /proc, etc.).

@Dmitry: what's your opinion on this?

-Y