On Tue, Feb 19, 2019 at 10:49 PM Arnd Bergmann <arnd@xxxxxxxx> wrote: > > Building an arm64 allmodconfig kernel with clang results in over 140 warnings > about overly large stack frames, the worst ones being: > > drivers/gpu/drm/panel/panel-sitronix-st7789v.c:196:12: error: stack frame size of 20224 bytes in function 'st7789v_prepare' > drivers/video/fbdev/omap2/omapfb/displays/panel-tpo-td028ttec1.c:196:12: error: stack frame size of 13120 bytes in function 'td028ttec1_panel_enable' > drivers/usb/host/max3421-hcd.c:1395:1: error: stack frame size of 10048 bytes in function 'max3421_spi_thread' > drivers/net/wan/slic_ds26522.c:209:12: error: stack frame size of 9664 bytes in function 'slic_ds26522_probe' > drivers/crypto/ccp/ccp-ops.c:2434:5: error: stack frame size of 8832 bytes in function 'ccp_run_cmd' > drivers/media/dvb-frontends/stv0367.c:1005:12: error: stack frame size of 7840 bytes in function 'stv0367ter_algo' > > None of these happen with gcc today, and almost all of these are the result > of a single known bug in llvm. Hopefully it will eventually get fixed with the > clang-9 release. > > In the meantime, the best idea I have is to turn off asan-stack for clang-8 > and earlier, so we can produce a kernel that is safe to run. Hi Arnd, I don't think it's good to disable KASAN stack instrumentation for the whole kernel by default with clang. It makes more sense to disable stack instrumentation only for these few drivers. Thanks! > > I have posted three patches that address the frame overflow warnings that are > not addressed by turning off asan-stack, so in combination with this change, > we get much closer to a clean allmodconfig build, which in turn is necessary > to do meaningful build regression testing. > > Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> > Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > Cc: Mark Brown <broonie@xxxxxxxxxx> > Cc: Qian Cai <cai@xxxxxx> > Link: https://bugs.llvm.org/show_bug.cgi?id=38809 > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> > --- > lib/Kconfig.kasan | 13 +++++++++++++ > scripts/Makefile.kasan | 2 +- > 2 files changed, 14 insertions(+), 1 deletion(-) > > diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan > index 67d7d1309c52..219cddc913ac 100644 > --- a/lib/Kconfig.kasan > +++ b/lib/Kconfig.kasan > @@ -103,6 +103,19 @@ config KASAN_INLINE > > endchoice > > +config KASAN_STACK > + int > + default 0 if CC_IS_CLANG && (CLANG_VERSION < 90000) > + default 1 > + help > + The LLVM stack address sanitizer has a know bug that > + causes excessive stack usage in a lot of functions, see > + https://bugs.llvm.org/show_bug.cgi?id=38809 > + Disabling asan-stack makes it safe to run kernels build > + with clang-8 with KASAN enabled, though it loses some of > + the functionality. We assume that clang-9 will have a fix, > + so the feature can be used. > + > config KASAN_S390_4_LEVEL_PAGING > bool "KASan: use 4-level paging" > depends on KASAN && S390 > diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan > index f1fb8e502657..6410bd22fe38 100644 > --- a/scripts/Makefile.kasan > +++ b/scripts/Makefile.kasan > @@ -26,7 +26,7 @@ else > CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \ > $(call cc-param,asan-globals=1) \ > $(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \ > - $(call cc-param,asan-stack=1) \ > + $(call cc-param,asan-stack=$(CONFIG_KASAN_STACK)) \ > $(call cc-param,asan-instrument-allocas=1) > endif > > -- > 2.20.0 >
