On Thu, Oct 27, 2022 at 7:33 AM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote: > > On Tue, Oct 25, 2022 at 6:22 AM Alexander Potapenko <glider@xxxxxxxxxx> wrote: > > > > KMSAN adds a lot of instrumentation to the code, which results in > > increased stack usage (up to 2048 bytes and more in some cases). > > It's hard to predict how big the stack frames can be, so we disable > > the warnings for KMSAN instead. > > > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > Cc: Kees Cook <keescook@xxxxxxxxxxxx> > > Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx> > > Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > > Cc: linux-kbuild@xxxxxxxxxxxxxxx > > Link: https://github.com/google/kmsan/issues/89 > > Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> > > --- > > lib/Kconfig.debug | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > > index 3fc7abffc7aa2..29280072dc0e4 100644 > > --- a/lib/Kconfig.debug > > +++ b/lib/Kconfig.debug > > @@ -400,8 +400,9 @@ config FRAME_WARN > > default 1536 if (!64BIT && XTENSA) > > default 1024 if !64BIT > > default 2048 if 64BIT > > + default 0 if KMSAN > > > > This is wrong. > > Kconfig picks up the first default entry which has > true 'if' condition. > > > Since (!64BIT || 64BIT) covers all the possible cases, > this patch is just adding dead code. > Thanks for clarifying! What we actually need is to forcefully disable CONFIG_FRAME_WARN under KMSAN, but adding constructs like "select FRAME_WARN 0" or "select FRAME_WARN=0" doesn't work, right? I'll move "default 0 if KMSAN" to the beginning of FRAME_WARN declaration then. > > > > > > > help > > - Tell gcc to warn at build time for stack frames larger than this. > > + Tell the compiler to warn at build time for stack frames larger than this. > > Setting this too low will cause a lot of warnings. > > Setting it to 0 disables the warning. > > > > -- > > 2.38.0.135.g90850a2211-goog > > > > > -- > Best Regards > Masahiro Yamada -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Paul Manicle, Liana Sebastian Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
