Merge branch 'kcsan.2020.01.07a' into locking/kcsan

Pull KCSAN updates from Paul E. McKenney:

 - UBSAN fixes
 - inlining updates
 - documentation updates

Signed-off-by: Ingo Molnar <mingo@kernel.org>

Documentation/dev-tools/kcsan.rst

@@ -101,18 +101,28 @@ instrumentation or e.g. DMA accesses.
 Selective analysis
 ~~~~~~~~~~~~~~~~~~
 
-To disable KCSAN data race detection for an entire subsystem, add to the
-respective ``Makefile``::
+It may be desirable to disable data race detection for specific accesses,
+functions, compilation units, or entire subsystems.  For static blacklisting,
+the below options are available:
 
-    KCSAN_SANITIZE := n
+* KCSAN understands the ``data_race(expr)`` annotation, which tells KCSAN that
+  any data races due to accesses in ``expr`` should be ignored and resulting
+  behaviour when encountering a data race is deemed safe.
 
-To disable KCSAN on a per-file basis, add to the ``Makefile``::
+* Disabling data race detection for entire functions can be accomplished by
+  using the function attribute ``__no_kcsan`` (or ``__no_kcsan_or_inline`` for
+  ``__always_inline`` functions). To dynamically control for which functions
+  data races are reported, see the `debugfs`_ blacklist/whitelist feature.
+
+* To disable data race detection for a particular compilation unit, add to the
+  ``Makefile``::
 
     KCSAN_SANITIZE_file.o := n
 
-KCSAN also understands the ``data_race(expr)`` annotation, which tells KCSAN
-that any data races due to accesses in ``expr`` should be ignored and resulting
-behaviour when encountering a data race is deemed safe.
+* To disable data race detection for all compilation units listed in a
+  ``Makefile``, add to the respective ``Makefile``::
+
+    KCSAN_SANITIZE := n
 
 debugfs
 ~~~~~~~

include/linux/compiler-gcc.h

@@ -146,8 +146,7 @@
 #endif
 
 #if defined(__SANITIZE_THREAD__) && __has_attribute(__no_sanitize_thread__)
-#define __no_sanitize_thread                                                   \
-	__attribute__((__noinline__)) __attribute__((no_sanitize_thread))
+#define __no_sanitize_thread __attribute__((no_sanitize_thread))
 #else
 #define __no_sanitize_thread
 #endif

include/linux/compiler.h

@@ -207,12 +207,15 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 # define __no_kasan_or_inline __always_inline
 #endif
 
+#define __no_kcsan __no_sanitize_thread
 #ifdef __SANITIZE_THREAD__
 /*
  * Rely on __SANITIZE_THREAD__ instead of CONFIG_KCSAN, to avoid not inlining in
- * compilation units where instrumentation is disabled.
+ * compilation units where instrumentation is disabled. The attribute 'noinline'
+ * is required for older compilers, where implicit inlining of very small
+ * functions renders __no_sanitize_thread ineffective.
  */
-# define __no_kcsan_or_inline __no_sanitize_thread notrace __maybe_unused
+# define __no_kcsan_or_inline __no_kcsan noinline notrace __maybe_unused
 # define __no_sanitize_or_inline __no_kcsan_or_inline
 #else
 # define __no_kcsan_or_inline __always_inline

kernel/kcsan/Makefile

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 KCSAN_SANITIZE := n
 KCOV_INSTRUMENT := n
+UBSAN_SANITIZE := n
 
 CFLAGS_REMOVE_core.o = $(CC_FLAGS_FTRACE)
 

lib/Makefile

@@ -282,6 +282,7 @@ obj-$(CONFIG_UBSAN) += ubsan.o
 
 UBSAN_SANITIZE_ubsan.o := n
 KASAN_SANITIZE_ubsan.o := n
+KCSAN_SANITIZE_ubsan.o := n
 CFLAGS_ubsan.o := $(call cc-option, -fno-stack-protector) $(DISABLE_STACKLEAK_PLUGIN)
 
 obj-$(CONFIG_SBITMAP) += sbitmap.o

scripts/atomic/fallbacks/acquire

@@ -1,5 +1,5 @@
 cat <<EOF
-static inline ${ret}
+static __always_inline ${ret}
 ${atomic}_${pfx}${name}${sfx}_acquire(${params})
 {
 	${ret} ret = ${atomic}_${pfx}${name}${sfx}_relaxed(${args});

scripts/atomic/fallbacks/add_negative

@@ -8,7 +8,7 @@ cat <<EOF
  * if the result is negative, or false when
  * result is greater than or equal to zero.
  */
-static inline bool
+static __always_inline bool
 ${atomic}_add_negative(${int} i, ${atomic}_t *v)
 {
 	return ${atomic}_add_return(i, v) < 0;

scripts/atomic/fallbacks/add_unless

@@ -8,7 +8,7 @@ cat << EOF
  * Atomically adds @a to @v, if @v was not already @u.
  * Returns true if the addition was done.
  */
-static inline bool
+static __always_inline bool
 ${atomic}_add_unless(${atomic}_t *v, ${int} a, ${int} u)
 {
 	return ${atomic}_fetch_add_unless(v, a, u) != u;

scripts/atomic/fallbacks/andnot

@@ -1,5 +1,5 @@
 cat <<EOF
-static inline ${ret}
+static __always_inline ${ret}
 ${atomic}_${pfx}andnot${sfx}${order}(${int} i, ${atomic}_t *v)
 {
 	${retstmt}${atomic}_${pfx}and${sfx}${order}(~i, v);

scripts/atomic/fallbacks/dec

@@ -1,5 +1,5 @@
 cat <<EOF
-static inline ${ret}
+static __always_inline ${ret}
 ${atomic}_${pfx}dec${sfx}${order}(${atomic}_t *v)
 {
 	${retstmt}${atomic}_${pfx}sub${sfx}${order}(1, v);

scripts/atomic/fallbacks/dec_and_test

@@ -7,7 +7,7 @@ cat <<EOF
  * returns true if the result is 0, or false for all other
  * cases.
  */
-static inline bool
+static __always_inline bool
 ${atomic}_dec_and_test(${atomic}_t *v)
 {
 	return ${atomic}_dec_return(v) == 0;

scripts/atomic/fallbacks/dec_if_positive

@@ -1,5 +1,5 @@
 cat <<EOF
-static inline ${ret}
+static __always_inline ${ret}
 ${atomic}_dec_if_positive(${atomic}_t *v)
 {
 	${int} dec, c = ${atomic}_read(v);

scripts/atomic/fallbacks/dec_unless_positive

@@ -1,5 +1,5 @@
 cat <<EOF
-static inline bool
+static __always_inline bool
 ${atomic}_dec_unless_positive(${atomic}_t *v)
 {
 	${int} c = ${atomic}_read(v);

scripts/atomic/fallbacks/fence

@@ -1,5 +1,5 @@
 cat <<EOF
-static inline ${ret}
+static __always_inline ${ret}
 ${atomic}_${pfx}${name}${sfx}(${params})
 {
 	${ret} ret;

scripts/atomic/fallbacks/fetch_add_unless

@@ -8,7 +8,7 @@ cat << EOF
  * Atomically adds @a to @v, so long as @v was not already @u.
  * Returns original value of @v
  */
-static inline ${int}
+static __always_inline ${int}
 ${atomic}_fetch_add_unless(${atomic}_t *v, ${int} a, ${int} u)
 {
 	${int} c = ${atomic}_read(v);

scripts/atomic/fallbacks/inc

@@ -1,5 +1,5 @@
 cat <<EOF
-static inline ${ret}
+static __always_inline ${ret}
 ${atomic}_${pfx}inc${sfx}${order}(${atomic}_t *v)
 {
 	${retstmt}${atomic}_${pfx}add${sfx}${order}(1, v);

scripts/atomic/fallbacks/inc_and_test

@@ -7,7 +7,7 @@ cat <<EOF
  * and returns true if the result is zero, or false for all
  * other cases.
  */
-static inline bool
+static __always_inline bool
 ${atomic}_inc_and_test(${atomic}_t *v)
 {
 	return ${atomic}_inc_return(v) == 0;

scripts/atomic/fallbacks/inc_not_zero

@@ -6,7 +6,7 @@ cat <<EOF
  * Atomically increments @v by 1, if @v is non-zero.
  * Returns true if the increment was done.
  */
-static inline bool
+static __always_inline bool
 ${atomic}_inc_not_zero(${atomic}_t *v)
 {
 	return ${atomic}_add_unless(v, 1, 0);

scripts/atomic/fallbacks/inc_unless_negative

@@ -1,5 +1,5 @@
 cat <<EOF
-static inline bool
+static __always_inline bool
 ${atomic}_inc_unless_negative(${atomic}_t *v)
 {
 	${int} c = ${atomic}_read(v);

scripts/atomic/fallbacks/read_acquire

@@ -1,5 +1,5 @@
 cat <<EOF
-static inline ${ret}
+static __always_inline ${ret}
 ${atomic}_read_acquire(const ${atomic}_t *v)
 {
 	return smp_load_acquire(&(v)->counter);

scripts/atomic/fallbacks/release

@@ -1,5 +1,5 @@
 cat <<EOF
-static inline ${ret}
+static __always_inline ${ret}
 ${atomic}_${pfx}${name}${sfx}_release(${params})
 {
 	__atomic_release_fence();

scripts/atomic/fallbacks/set_release

@@ -1,5 +1,5 @@
 cat <<EOF
-static inline void
+static __always_inline void
 ${atomic}_set_release(${atomic}_t *v, ${int} i)
 {
 	smp_store_release(&(v)->counter, i);

scripts/atomic/fallbacks/sub_and_test

@@ -8,7 +8,7 @@ cat <<EOF
  * true if the result is zero, or false for all
  * other cases.
  */
-static inline bool
+static __always_inline bool
 ${atomic}_sub_and_test(${int} i, ${atomic}_t *v)
 {
 	return ${atomic}_sub_return(i, v) == 0;

scripts/atomic/fallbacks/try_cmpxchg

@@ -1,5 +1,5 @@
 cat <<EOF
-static inline bool
+static __always_inline bool
 ${atomic}_try_cmpxchg${order}(${atomic}_t *v, ${int} *old, ${int} new)
 {
 	${int} r, o = *old;

scripts/atomic/gen-atomic-fallback.sh

@@ -149,6 +149,8 @@ cat << EOF
 #ifndef _LINUX_ATOMIC_FALLBACK_H
 #define _LINUX_ATOMIC_FALLBACK_H
 
+#include <linux/compiler.h>
+
 EOF
 
 for xchg in "xchg" "cmpxchg" "cmpxchg64"; do

scripts/atomic/gen-atomic-instrumented.sh

@@ -84,7 +84,7 @@ gen_proto_order_variant()
 	[ ! -z "${guard}" ] && printf "#if ${guard}\n"
 
 cat <<EOF
-static inline ${ret}
+static __always_inline ${ret}
 ${atomicname}(${params})
 {
 ${checks}
@@ -147,16 +147,17 @@ cat << EOF
 #define _ASM_GENERIC_ATOMIC_INSTRUMENTED_H
 
 #include <linux/build_bug.h>
+#include <linux/compiler.h>
 #include <linux/kasan-checks.h>
 #include <linux/kcsan-checks.h>
 
-static inline void __atomic_check_read(const volatile void *v, size_t size)
+static __always_inline void __atomic_check_read(const volatile void *v, size_t size)
 {
 	kasan_check_read(v, size);
 	kcsan_check_atomic_read(v, size);
 }
 
-static inline void __atomic_check_write(const volatile void *v, size_t size)
+static __always_inline void __atomic_check_write(const volatile void *v, size_t size)
 {
 	kasan_check_write(v, size);
 	kcsan_check_atomic_write(v, size);

scripts/atomic/gen-atomic-long.sh

@@ -46,7 +46,7 @@ gen_proto_order_variant()
 	local retstmt="$(gen_ret_stmt "${meta}")"
 
 cat <<EOF
-static inline ${ret}
+static __always_inline ${ret}
 atomic_long_${name}(${params})
 {
 	${retstmt}${atomic}_${name}(${argscast});
@@ -64,6 +64,7 @@ cat << EOF
 #ifndef _ASM_GENERIC_ATOMIC_LONG_H
 #define _ASM_GENERIC_ATOMIC_LONG_H
 
+#include <linux/compiler.h>
 #include <asm/types.h>
 
 #ifdef CONFIG_64BIT