On Thu, Feb 9, 2017 at 3:33 PM, Arnd Bergmann <a...@arndb.de> wrote: >>> >>> Thanks for the list, that looks very helpful. The ones I found myself >>> seem to be a strict (and small) subset of those, using gcc-7.0.1 on x86-64 >>> with allmodconfig and a few hundred randconfig builds. Which compiler >>> version did you use for your testing? If new versions are better than old >>> ones, we could start by fixing the ones that are still present in gcc-6 and >>> gcc-7, and making the warning conditionally on the compiler version. >>> >>> Another idea might be to separate out asan_stack=1 into a separate >>> Kconfig option and warn if that is enabled with compilers that are known >>> to be relatively bad it keeping the stack small. >> >> >> Mine is gcc version 7.0.0 20161208. Make sure you enable KASAN_INLINE >> and I also enabled CONFIG_KCOV. Other than that I just did >> allyesconfig + make -k. > > Ok, I see my mistake now: On the allmodconfig build, I had KASAN_INLINE > disabled, which made the problem go away for almost all files (almost all > frame sizes are below 2048 bytes, except for the two issues I posted patches > for (hisilicon ethernet driver, and nla_put_* users). > > On the randconfig build test, I have a long series of patches applied that > address all known warnings, including my earlier "kasan: turn off > -fsanitize-address-use-after-scope for now" (see > https://patchwork.kernel.org/patch/9442323/). Without > -fsanitize-address-use-after-scope, the problem is also mostly gone > (a few cases show up in drivers/media/, and also in block/sed-opal.c > and drivers/tty/vt/keyboard.c). I now have initial patches for all of > them to bring the stack size below 2048 bytes. > > As far as I can see, the remaining problems with scary stack frame sizes > you found only show up with the combination of all three: KASAN_INLINE, > asan_stack=1 and -fsanitize-address-use-after-scope. If all three were > separately configurable and we merge the patches I made, I think we could > enable the normal 2048 byte warning in all configurations that have at least > one of the turned off, but I don't know which of those combinations would > actually be sensible for production kernels.
FWIW I use all of them (+KCOV which is additional instrumentation). If you ask which is the least important one, it is -fsanitize-address-use-after-scope. I have not see any single report due to it (probably due to kernel coding style).
