[PATCH -tip v2 1/2] kasan: Bump required compiler version

[PATCH -tip v2 1/2] kasan: Bump required compiler version

[Marco Elver]

Adds config variable CC_HAS_WORKING_NOSANITIZE_ADDRESS, which will be
true if we have a compiler that does not fail builds due to
no_sanitize_address functions. This does not yet mean they work as
intended, but for automated build-tests, this is the minimum
requirement.

For example, we require that __always_inline functions used from
no_sanitize_address functions do not generate instrumentation. On GCC <=
7 this fails to build entirely, therefore we make the minimum version
GCC 8.

Link: https://lkml.kernel.org/r/20200602175859.GC2604@hirez.programming.kicks-ass.net
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Marco Elver <elver@google.com>
---
Apply after:
https://lkml.kernel.org/r/20200602173103.931412766@infradead.org

v2:
* No longer restrict UBSAN (and KCSAN), since the attributes behave
  differently for different sanitizers. For UBSAN the above case with GCC
  <= 7 actually works fine (no compiler error). So it seems that only
  KASAN is affected by this -- let's limit our restriction to KASAN.
---
 lib/Kconfig.kasan | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index 81f5464ea9e1..af0dd09f91e9 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -15,11 +15,15 @@ config CC_HAS_KASAN_GENERIC
 config CC_HAS_KASAN_SW_TAGS
 	def_bool $(cc-option, -fsanitize=kernel-hwaddress)
 
+config CC_HAS_WORKING_NOSANITIZE_ADDRESS
+	def_bool !CC_IS_GCC || GCC_VERSION >= 80000
+
 config KASAN
 	bool "KASAN: runtime memory debugger"
 	depends on (HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \
 		   (HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS)
 	depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
+	depends on CC_HAS_WORKING_NOSANITIZE_ADDRESS
 	help
 	  Enables KASAN (KernelAddressSANitizer) - runtime memory debugger,
 	  designed to find out-of-bounds accesses and use-after-free bugs.
-- 
2.27.0.rc2.251.g90737beb825-goog

[PATCH -tip v2 2/2] compiler_types.h: Add __no_sanitize_{address,undefined} to noinstr

[Marco Elver]

Adds the portable definitions for __no_sanitize_address, and
__no_sanitize_undefined, and subsequently changes noinstr to use the
attributes to disable instrumentation via KASAN or UBSAN.

Link: https://lore.kernel.org/lkml/000000000000d2474c05a6c938fe@google.com/
Reported-by: syzbot+dc1fa714cb070b184db5@syzkaller.appspotmail.com
Acked-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Signed-off-by: Marco Elver <elver@google.com>
---

Note: __no_sanitize_coverage (for KCOV) isn't possible right now,
because neither GCC nor Clang support such an attribute. This means
going and changing the compilers again (for Clang it's fine, for GCC,
it'll take a while).

However, it looks like that KCOV_INSTRUMENT := n is currently in all the
right places. Short-term, this should be reasonable.

v2:
* No change.
---
 include/linux/compiler-clang.h | 8 ++++++++
 include/linux/compiler-gcc.h   | 6 ++++++
 include/linux/compiler_types.h | 3 ++-
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index 2cb42d8bdedc..c0e4b193b311 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -33,6 +33,14 @@
 #define __no_sanitize_thread
 #endif
 
+#if __has_feature(undefined_behavior_sanitizer)
+/* GCC does not have __SANITIZE_UNDEFINED__ */
+#define __no_sanitize_undefined \
+		__attribute__((no_sanitize("undefined")))
+#else
+#define __no_sanitize_undefined
+#endif
+
 /*
  * Not all versions of clang implement the the type-generic versions
  * of the builtin overflow checkers. Fortunately, clang implements
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 7dd4e0349ef3..1c74464c80c6 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -150,6 +150,12 @@
 #define __no_sanitize_thread
 #endif
 
+#if __has_attribute(__no_sanitize_undefined__)
+#define __no_sanitize_undefined __attribute__((no_sanitize_undefined))
+#else
+#define __no_sanitize_undefined
+#endif
+
 #if GCC_VERSION >= 50100
 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
 #endif
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 02becd21d456..89b8c1ae18a1 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -198,7 +198,8 @@ struct ftrace_likely_data {
 
 /* Section for code which can't be instrumented at all */
 #define noinstr								\
-	noinline notrace __attribute((__section__(".noinstr.text"))) __no_kcsan
+	noinline notrace __attribute((__section__(".noinstr.text")))	\
+	__no_kcsan __no_sanitize_address __no_sanitize_undefined
 
 #endif /* __KERNEL__ */
 
-- 
2.27.0.rc2.251.g90737beb825-goog