path: root/lib/Kconfig.kasan
diff options
authorArnd Bergmann <>2019-02-28 16:21:58 -0800
committerLinus Torvalds <>2019-03-01 09:02:33 -0800
commit6baec880d7a53cbc2841123e56ee31e830df9b49 (patch)
tree0d3b8aa38b8c1193677358b0e8ab4232cc24209c /lib/Kconfig.kasan
parent7d762d69145a54d169f58e56d6dac57a5508debc (diff)
kasan: turn off asan-stack for clang-8 and earlier
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 issue 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. It is still possible to turn on the CONFIG_ASAN_STACK option on all versions of clang, and it's always enabled for gcc, but when CONFIG_COMPILE_TEST is set, the option remains invisible, so allmodconfig and randconfig builds (which are normally done with a forced CONFIG_COMPILE_TEST) will still result in a mostly clean build. Link: Link: Signed-off-by: Arnd Bergmann <> Reviewed-by: Qian Cai <> Reviewed-by: Mark Brown <> Acked-by: Andrey Ryabinin <> Cc: Dmitry Vyukov <> Cc: Nick Desaulniers <> Cc: Kostya Serebryany <> Cc: Andrey Konovalov <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'lib/Kconfig.kasan')
1 files changed, 22 insertions, 0 deletions
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index d8c474b6691e..9737059ec58b 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -113,6 +113,28 @@ config KASAN_INLINE
+ bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
+ default !(CLANG_VERSION < 90000)
+ depends on KASAN
+ help
+ The LLVM stack address sanitizer has a know problem that
+ causes excessive stack usage in a lot of functions, see
+ Disabling asan-stack makes it safe to run kernels build
+ with clang-8 with KASAN enabled, though it loses some of
+ the functionality.
+ This feature is always disabled when compile-testing with clang-8
+ or earlier to avoid cluttering the output in stack overflow
+ warnings, but clang-8 users can still enable it for builds without
+ CONFIG_COMPILE_TEST. On gcc and later clang versions it is
+ assumed to always be safe to use and enabled by default.
+ int
+ default 1 if KASAN_STACK_ENABLE || CC_IS_GCC
+ default 0
bool "KASan: use 4-level paging"
depends on KASAN && S390