On 01/30/2016 03:36 AM, Mike Krinkin wrote:
> option CONFIG_UBSAN_ALIGNMENT breaks x86-64 kernel with lockdep enabled,
> i. e kernel with CONFIG_UBSAN_ALIGNMENT fails to load without even any
> error message.
>
> The problem is that ubsan callbacks use spinlocks and might be called
> before lockdep is initialized.
There is also report from kernel test robot:
[ 0.000000] WARNING: lockdep init error: lock 'report_lock' was acquired
before lockdep_init().
[ 0.000000] Call stack leading to lockdep invocation was:
[ 0.000000] [<b9e30ec5>] save_stack_trace+0x26/0x16d
[ 0.000000] [<b9f98054>] __lock_acquire+0x237/0x15a4
[ 0.000000] [<b9f994db>] lock_acquire+0x11a/0x1a9
[ 0.000000] [<bae228f9>] _raw_spin_lock_irqsave+0x39/0x49
[ 0.000000] [<ba5df852>] ubsan_prologue+0x1e/0x51
[ 0.000000] [<ba5dfb02>] __ubsan_handle_type_mismatch+0xbd/0x14a
[ 0.000000] [<bbca63c3>] reserve_ebda_region+0x8b/0x1bb
[ 0.000000] [<bbca632c>] i386_start_kernel+0xf6/0x102
[ 0.000000] [<ffffffff>] 0xffffffff
Let's disable aligment checks for x86-specific code since those are not
useful.
Changes around CFLAGS_UBSAN in this patch needed to be sure that cflags
from 'subdir-ccflags-' appears only after CFLAGS_UBSAN.
Signed-off-by: Andrey Ryabinin <aryabi...@virtuozzo.com>
Reported-by: kernel test robot <ying.hu...@linux.intel.com>
Reported-by: Mike Krinkin <krinkin....@gmail.com>
---
Makefile | 2 +-
arch/x86/Kbuild | 2 ++
scripts/Makefile.lib | 4 ++--
scripts/Makefile.ubsan | 5 +++++
4 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/Makefile b/Makefile
index 6c1a3c2..1da29a0 100644
--- a/Makefile
+++ b/Makefile
@@ -411,7 +411,7 @@ export MAKE AWK GENKSYMS INSTALLKERNEL PERL PYTHON
UTS_MACHINE
export HOSTCXX HOSTCXXFLAGS LDFLAGS_MODULE CHECK CHECKFLAGS
export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS LDFLAGS
-export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE CFLAGS_GCOV CFLAGS_KASAN
CFLAGS_UBSAN
+export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE CFLAGS_GCOV CFLAGS_KASAN
export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE
export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE
export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL
diff --git a/arch/x86/Kbuild b/arch/x86/Kbuild
index 1538562..f1348ce 100644
--- a/arch/x86/Kbuild
+++ b/arch/x86/Kbuild
@@ -21,3 +21,5 @@ obj-y += platform/
obj-y += net/
obj-$(CONFIG_KEXEC_FILE) += purgatory/
+
+subdir-ccflags-$(CONFIG_UBSAN_ALIGNMENT) := $(call cc-option,
-fno-sanitize=alignment)
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 2edbcad..d7342cf 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -132,8 +132,8 @@ endif
ifeq ($(CONFIG_UBSAN),y)
_c_flags += $(if $(patsubst n%,, \
-
$(UBSAN_SANITIZE_$(basetarget).o)$(UBSAN_SANITIZE)$(CONFIG_UBSAN_SANITIZE_ALL)),
\
- $(CFLAGS_UBSAN))
+
$(UBSAN_SANITIZE_$(basetarget).o)$(UBSAN_SANITIZE)$(CONFIG_UBSAN_SANITIZE_ALL)),,
\
+ $(DISABLE_UBSAN))
endif
# If building the kernel in a separate objtree expand all occurrences
diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
index 77ce538..91c1dd3 100644
--- a/scripts/Makefile.ubsan
+++ b/scripts/Makefile.ubsan
@@ -18,4 +18,9 @@ endif
# -fsanitize=* options makes GCC less smart than usual and
# increase number of 'maybe-uninitialized false-positives
CFLAGS_UBSAN += $(call cc-option, -Wno-maybe-uninitialized)
+
+ KBUILD_CFLAGS += $(CFLAGS_UBSAN)
+ export DISABLE_UBSAN
+ DISABLE_UBSAN := $(call cc-option, -fno-sanitize=undefined)
+ DISABLE_UBSAN += $(call cc-option, -Wmaybe-uninitialized)
endif
--
2.4.10
