lkml.org 
[lkml]   [2019]   [Feb]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] kasan: turn off asan-stack for clang-8 and earlier
Date
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.

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@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Qian Cai <cai@lca.pw>
Link: https://bugs.llvm.org/show_bug.cgi?id=38809
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
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
\
 
 \ /
  Last update: 2019-02-19 22:50    [W:0.095 / U:11.896 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site