ubsan: allow to disable the null sanitizer

Some architectures use a hardware defined structure at address zero.
Checking for a null pointer will result in many ubsan reports.
Allow users to disable the null sanitizer.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

2 files changed, 15 insertions, 1 deletions

diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
index 39494af9a84a..bc6e651df68c 100644
--- a/lib/Kconfig.ubsan
+++ b/lib/Kconfig.ubsan
@@ -1,6 +1,9 @@
 config ARCH_HAS_UBSAN_SANITIZE_ALL
         bool
 
+config ARCH_WANTS_UBSAN_NO_NULL
+        def_bool n
+
 config UBSAN
         bool "Undefined behaviour sanity checker"
         help
@@ -34,3 +37,11 @@ config UBSAN_ALIGNMENT
           This option enables detection of unaligned memory accesses.
           Enabling this option on architectures that support unaligned
           accesses may produce a lot of false positives.
+
+config UBSAN_NULL
+        bool "Enable checking of null pointers"
+        depends on UBSAN
+        default y if !ARCH_WANTS_UBSAN_NO_NULL
+        help
+          This option enables detection of memory accesses via a
+          null pointer.
diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
index 8ab68679cfb5..dd779c40c8e6 100644
--- a/scripts/Makefile.ubsan
+++ b/scripts/Makefile.ubsan
@@ -3,7 +3,6 @@ ifdef CONFIG_UBSAN
       CFLAGS_UBSAN += $(call cc-option, -fsanitize=integer-divide-by-zero)
       CFLAGS_UBSAN += $(call cc-option, -fsanitize=unreachable)
       CFLAGS_UBSAN += $(call cc-option, -fsanitize=vla-bound)
-      CFLAGS_UBSAN += $(call cc-option, -fsanitize=null)
       CFLAGS_UBSAN += $(call cc-option, -fsanitize=signed-integer-overflow)
       CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds)
       CFLAGS_UBSAN += $(call cc-option, -fsanitize=object-size)
@@ -14,4 +13,8 @@ ifdef CONFIG_UBSAN
 ifdef CONFIG_UBSAN_ALIGNMENT
       CFLAGS_UBSAN += $(call cc-option, -fsanitize=alignment)
 endif
+
+ifdef CONFIG_UBSAN_NULL
+      CFLAGS_UBSAN += $(call cc-option, -fsanitize=null)
+endif
 endif