Backporting KAsan patches to 4.9 branch

[Yury Gribov]

On 09/18/2014 01:57 PM, Jakub Jelinek wrote:
 > On Thu, Sep 18, 2014 at 01:46:21PM +0400, Yury Gribov wrote:
 >> Kernel Asan patches are currently being discussed in LKML. One of 
the points>> raised during review was that KAsan requires GCC 5.0 which 
is presumably
 >> unstable (e.g. compilation of kernel modules has been broken for two 
months
 >> due to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61848).
 >>
 >> Would it make sense to backport Kasan-related patches to 4.9 branch 
to make
 >> this feature more accessible to kernel developers? Quick analysis showed
 >> that at the very least this would require
 >> ...
 >> Is it ok to backport these to 4.9? Note that I would discard patches for
 >> other sanitizers (UBsan, Tsan).
 >
 > I'd say so, if it doesn't need any library changes
 > (especially not any ABI
 > visible ones, guess bugfixes could be acceptable).

Finally got time to look into this. I've successfully backported 22 
patches to 4.9:
* bugfixes (12 patches)
* install Asan headers (1 patch)
* libsanitizer merge (1 patch) - this is questionable, see below for 
discussion
* BUILT_IN_ASAN_REPORT_{LOAD,STORE}_N (2 patches)
* instrumentation with calls (1 patch)
* optimize strlen instrumentation (1 patch)
* move inlining to sanopt pass (2 patches)
* Kasan (2 patches)

One problem is that for BUILT_IN_ASAN_REPORT_{LOAD,STORE}_N patch I need 
libsanitizer APIs (__asan_loadN, __asan_storeN) which were introduced in 
a giant libsanitizer merge in 5.0. In current patchset I backport the 
whole merge patch (and a bunch of cherry-picks which followed it) but it 
changes libsanitizer ABI (new version of __asan_init_vXXX, etc.) which 
is probably undesirable. Another option would be to backport just the 
necessary minimum (__asan_loadN, __asan_storeN). How should I proceed?

Another question: Should I update patch CL dates for backported patches? 
If not - should I insert them to CLs in chronological order or just 
stack on top of previous contents?

-Y