On 05/31/2017 08:50 AM, Joonsoo Kim wrote: >>> But the main win as I see it is that that's basically complete support >>> for 32-bit arches. People do ask about arm32 support: >>> https://groups.google.com/d/msg/kasan-dev/Sk6BsSPMRRc/Gqh4oD_wAAAJ >>> https://groups.google.com/d/msg/kasan-dev/B22vOFp-QWg/EVJPbrsgAgAJ >>> and probably mips32 is relevant as well. >> >> I don't see how above is relevant for 32-bit arches. Current design >> is perfectly fine for 32-bit arches. I did some POC arm32 port couple years >> ago - https://github.com/aryabinin/linux/commits/kasan/arm_v0_1 >> It has some ugly hacks and non-critical bugs. AFAIR it also super-slow because I (mistakenly) >> made shadow memory uncached. But otherwise it works. > > Could you explain that where is the code to map shadow memory uncached? > I don't find anything related to it. > I didn't set set any cache policy (L_PTE_MT_*) on shadow mapping (see set_pte_at() calls ) which means it's L_PTE_MT_UNCACHED >>> Such mode does not require a huge continuous address space range, has >>> minimal memory consumption and requires minimal arch-dependent code. >>> Works only with outline instrumentation, but I think that's a >>> reasonable compromise. >>> >>> What do you think? >> >> I don't understand why we trying to invent some hacky/complex schemes when we already have >> a simple one - scaling shadow to 1/32. It's easy to implement and should be more performant comparing >> to suggested schemes. > > My approach can co-exist with changing scaling approach. It has it's > own benefit. > > And, as Dmitry mentioned before, scaling shadow to 1/32 also has downsides, > expecially for inline instrumentation. And, it requires compiler > modification and user needs to update their compiler to newer version > which is not so simple in terms of the user's usability > > Thanks. > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
