On Wed, Jun 27, 2018 at 4:08 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, 26 Jun 2018 15:15:10 +0200 Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > > This patchset adds a new mode to KASAN [1], which is called KHWASAN > > (Kernel HardWare assisted Address SANitizer). > > > > The plan is to implement HWASan [2] for the kernel with the incentive, > > that it's going to have comparable to KASAN performance, but in the same > > time consume much less memory, trading that off for somewhat imprecise > > bug detection and being supported only for arm64. > > Why do we consider this to be a worthwhile change? > > Is KASAN's memory consumption actually a significant problem? Some > data regarding that would be very useful. On mobile, ASAN's and KASAN's memory usage is a significant problem. Not sure if I can find scientific evidence of that. CC-ing Vishwath Mohan who deals with KASAN on Android to provide anecdotal evidence. There are several other benefits too: * HWASAN more reliably detects non-linear-buffer-overflows compared to ASAN (same for kernel-HWASAN vs kernel-ASAN) * Same for detecting use-after-free (since HWASAN doesn't rely on quarantine). * Much easier to implement stack-use-after-return detection (which IIRC KASAN doesn't have yet, because in KASAN it's too hard) > If it is a large problem then we still have that problem on x86, so the > problem remains largely unsolved? The problem is more significant on mobile devices than on desktop/server. I'd love to have [K]HWASAN on x86_64 as well, but it's less trivial since x86_64 doesn't have an analog of aarch64's top-byte-ignore hardware feature. > > > ====== Benchmarks > > > > The following numbers were collected on Odroid C2 board. Both KASAN and > > KHWASAN were used in inline instrumentation mode. > > > > Boot time [1]: > > * ~1.7 sec for clean kernel > > * ~5.0 sec for KASAN > > * ~5.0 sec for KHWASAN > > > > Slab memory usage after boot [2]: > > * ~40 kb for clean kernel > > * ~105 kb + 1/8th shadow ~= 118 kb for KASAN > > * ~47 kb + 1/16th shadow ~= 50 kb for KHWASAN > > > > Network performance [3]: > > * 8.33 Gbits/sec for clean kernel > > * 3.17 Gbits/sec for KASAN > > * 2.85 Gbits/sec for KHWASAN > > > > Note, that KHWASAN (compared to KASAN) doesn't require quarantine. > > > > [1] Time before the ext4 driver is initialized. > > [2] Measured as `cat /proc/meminfo | grep Slab`. > > [3] Measured as `iperf -s & iperf -c 127.0.0.1 -t 30`. > > The above doesn't actually demonstrate the whole point of the > patchset: to reduce KASAN's very high memory consumption? > > -- > You received this message because you are subscribed to the Google Groups "kasan-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@xxxxxxxxxxxxxxxx. > To post to this group, send email to kasan-dev@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20180627160800.3dc7f9ee41c0badbf7342520%40linux-foundation.org. > For more options, visit https://groups.google.com/d/optout.
