Merge branch 'rwonce/rework' of git://git.kernel.org/pub/scm/linux/kernel/git/will/linux

Pull READ/WRITE_ONCE rework from Will Deacon:
 "This the READ_ONCE rework I've been working on for a while, which
  bumps the minimum GCC version and improves code-gen on arm64 when
  stack protector is enabled"

[ Side note: I'm _really_ tempted to raise the minimum gcc version to
  4.9, so that we can just say that we require _Generic() support.

  That would allow us to more cleanly handle a lot of the cases where we
  depend on very complex macros with 'sizeof' or __builtin_choose_expr()
  with __builtin_types_compatible_p() etc.

  This branch has a workaround for sparse not handling _Generic(),
  either, but that was already fixed in the sparse development branch,
  so it's really just gcc-4.9 that we'd require.   - Linus ]

* 'rwonce/rework' of git://git.kernel.org/pub/scm/linux/kernel/git/will/linux:
  compiler_types.h: Use unoptimized __unqual_scalar_typeof for sparse
  compiler_types.h: Optimize __unqual_scalar_typeof compilation time
  compiler.h: Enforce that READ_ONCE_NOCHECK() access size is sizeof(long)
  compiler-types.h: Include naked type in __pick_integer_type() match
  READ_ONCE: Fix comment describing 2x32-bit atomicity
  gcov: Remove old GCC 3.4 support
  arm64: barrier: Use '__unqual_scalar_typeof' for acquire/release macros
  locking/barriers: Use '__unqual_scalar_typeof' for load-acquire macros
  READ_ONCE: Drop pointer qualifiers when reading from scalar types
  READ_ONCE: Enforce atomicity for {READ,WRITE}_ONCE() memory accesses
  READ_ONCE: Simplify implementations of {READ,WRITE}_ONCE()
  arm64: csum: Disable KASAN for do_csum()
  fault_inject: Don't rely on "return value" from WRITE_ONCE()
  net: tls: Avoid assigning 'const' pointer to non-const pointer
  netfilter: Avoid assigning 'const' pointer to non-const pointer
  compiler/gcc: Raise minimum GCC version for kernel builds to 4.8

Documentation/process/changes.rst

@@ -29,7 +29,7 @@ you probably needn't concern yourself with pcmciautils.
 ====================== ===============  ========================================
         Program        Minimal version       Command to check the version
 ====================== ===============  ========================================
-GNU C                  4.6              gcc --version
+GNU C                  4.8              gcc --version
 GNU make               3.81             make --version
 binutils               2.23             ld -v
 flex                   2.5.35           flex --version

arch/arm/crypto/Kconfig

@@ -30,7 +30,7 @@ config CRYPTO_SHA1_ARM_NEON
 
 config CRYPTO_SHA1_ARM_CE
 	tristate "SHA1 digest algorithm (ARM v8 Crypto Extensions)"
-	depends on KERNEL_MODE_NEON && (CC_IS_CLANG || GCC_VERSION >= 40800)
+	depends on KERNEL_MODE_NEON
 	select CRYPTO_SHA1_ARM
 	select CRYPTO_HASH
 	help
@@ -39,7 +39,7 @@ config CRYPTO_SHA1_ARM_CE
 
 config CRYPTO_SHA2_ARM_CE
 	tristate "SHA-224/256 digest algorithm (ARM v8 Crypto Extensions)"
-	depends on KERNEL_MODE_NEON && (CC_IS_CLANG || GCC_VERSION >= 40800)
+	depends on KERNEL_MODE_NEON
 	select CRYPTO_SHA256_ARM
 	select CRYPTO_HASH
 	help
@@ -96,7 +96,7 @@ config CRYPTO_AES_ARM_BS
 
 config CRYPTO_AES_ARM_CE
 	tristate "Accelerated AES using ARMv8 Crypto Extensions"
-	depends on KERNEL_MODE_NEON && (CC_IS_CLANG || GCC_VERSION >= 40800)
+	depends on KERNEL_MODE_NEON
 	select CRYPTO_SKCIPHER
 	select CRYPTO_LIB_AES
 	select CRYPTO_SIMD
@@ -106,7 +106,7 @@ config CRYPTO_AES_ARM_CE
 
 config CRYPTO_GHASH_ARM_CE
 	tristate "PMULL-accelerated GHASH using NEON/ARMv8 Crypto Extensions"
-	depends on KERNEL_MODE_NEON && (CC_IS_CLANG || GCC_VERSION >= 40800)
+	depends on KERNEL_MODE_NEON
 	select CRYPTO_HASH
 	select CRYPTO_CRYPTD
 	select CRYPTO_GF128MUL
@@ -118,13 +118,13 @@ config CRYPTO_GHASH_ARM_CE
 
 config CRYPTO_CRCT10DIF_ARM_CE
 	tristate "CRCT10DIF digest algorithm using PMULL instructions"
-	depends on KERNEL_MODE_NEON && (CC_IS_CLANG || GCC_VERSION >= 40800)
+	depends on KERNEL_MODE_NEON
 	depends on CRC_T10DIF
 	select CRYPTO_HASH
 
 config CRYPTO_CRC32_ARM_CE
 	tristate "CRC32(C) digest algorithm using CRC and/or PMULL instructions"
-	depends on KERNEL_MODE_NEON && (CC_IS_CLANG || GCC_VERSION >= 40800)
+	depends on KERNEL_MODE_NEON
 	depends on CRC32
 	select CRYPTO_HASH
 

arch/arm64/include/asm/barrier.h

@@ -76,8 +76,8 @@ static inline unsigned long array_index_mask_nospec(unsigned long idx,
 #define __smp_store_release(p, v)					\
 do {									\
 	typeof(p) __p = (p);						\
-	union { typeof(*p) __val; char __c[1]; } __u =			\
-		{ .__val = (__force typeof(*p)) (v) };			\
+	union { __unqual_scalar_typeof(*p) __val; char __c[1]; } __u =	\
+		{ .__val = (__force __unqual_scalar_typeof(*p)) (v) };	\
 	compiletime_assert_atomic_type(*p);				\
 	kasan_check_write(__p, sizeof(*p));				\
 	switch (sizeof(*p)) {						\
@@ -110,7 +110,7 @@ do {									\
 
 #define __smp_load_acquire(p)						\
 ({									\
-	union { typeof(*p) __val; char __c[1]; } __u;			\
+	union { __unqual_scalar_typeof(*p) __val; char __c[1]; } __u;	\
 	typeof(p) __p = (p);						\
 	compiletime_assert_atomic_type(*p);				\
 	kasan_check_read(__p, sizeof(*p));				\
@@ -136,33 +136,33 @@ do {									\
 			: "Q" (*__p) : "memory");			\
 		break;							\
 	}								\
-	__u.__val;							\
+	(typeof(*p))__u.__val;						\
 })
 
 #define smp_cond_load_relaxed(ptr, cond_expr)				\
 ({									\
 	typeof(ptr) __PTR = (ptr);					\
-	typeof(*ptr) VAL;						\
+	__unqual_scalar_typeof(*ptr) VAL;				\
 	for (;;) {							\
 		VAL = READ_ONCE(*__PTR);				\
 		if (cond_expr)						\
 			break;						\
 		__cmpwait_relaxed(__PTR, VAL);				\
 	}								\
-	VAL;								\
+	(typeof(*ptr))VAL;						\
 })
 
 #define smp_cond_load_acquire(ptr, cond_expr)				\
 ({									\
 	typeof(ptr) __PTR = (ptr);					\
-	typeof(*ptr) VAL;						\
+	__unqual_scalar_typeof(*ptr) VAL;				\
 	for (;;) {							\
 		VAL = smp_load_acquire(__PTR);				\
 		if (cond_expr)						\
 			break;						\
 		__cmpwait_relaxed(__PTR, VAL);				\
 	}								\
-	VAL;								\
+	(typeof(*ptr))VAL;						\
 })
 
 #include <asm-generic/barrier.h>

arch/arm64/lib/csum.c

@@ -14,7 +14,11 @@ static u64 accumulate(u64 sum, u64 data)
 	return tmp + (tmp >> 64);
 }
 
-unsigned int do_csum(const unsigned char *buff, int len)
+/*
+ * We over-read the buffer and this makes KASAN unhappy. Instead, disable
+ * instrumentation and call kasan explicitly.
+ */
+unsigned int __no_sanitize_address do_csum(const unsigned char *buff, int len)
 {
 	unsigned int offset, shift, sum;
 	const u64 *ptr;
@@ -42,7 +46,7 @@ unsigned int do_csum(const unsigned char *buff, int len)
 	 * odd/even alignment, and means we can ignore it until the very end.
 	 */
 	shift = offset * 8;
-	data = READ_ONCE_NOCHECK(*ptr++);
+	data = *ptr++;
 #ifdef __LITTLE_ENDIAN
 	data = (data >> shift) << shift;
 #else
@@ -58,10 +62,10 @@ unsigned int do_csum(const unsigned char *buff, int len)
 	while (unlikely(len > 64)) {
 		__uint128_t tmp1, tmp2, tmp3, tmp4;
 
-		tmp1 = READ_ONCE_NOCHECK(*(__uint128_t *)ptr);
-		tmp2 = READ_ONCE_NOCHECK(*(__uint128_t *)(ptr + 2));
-		tmp3 = READ_ONCE_NOCHECK(*(__uint128_t *)(ptr + 4));
-		tmp4 = READ_ONCE_NOCHECK(*(__uint128_t *)(ptr + 6));
+		tmp1 = *(__uint128_t *)ptr;
+		tmp2 = *(__uint128_t *)(ptr + 2);
+		tmp3 = *(__uint128_t *)(ptr + 4);
+		tmp4 = *(__uint128_t *)(ptr + 6);
 
 		len -= 64;
 		ptr += 8;
@@ -85,7 +89,7 @@ unsigned int do_csum(const unsigned char *buff, int len)
 		__uint128_t tmp;
 
 		sum64 = accumulate(sum64, data);
-		tmp = READ_ONCE_NOCHECK(*(__uint128_t *)ptr);
+		tmp = *(__uint128_t *)ptr;
 
 		len -= 16;
 		ptr += 2;
@@ -100,7 +104,7 @@ unsigned int do_csum(const unsigned char *buff, int len)
 	}
 	if (len > 0) {
 		sum64 = accumulate(sum64, data);
-		data = READ_ONCE_NOCHECK(*ptr);
+		data = *ptr;
 		len -= 8;
 	}
 	/*

crypto/Kconfig

@@ -316,7 +316,6 @@ config CRYPTO_AEGIS128
 config CRYPTO_AEGIS128_SIMD
 	bool "Support SIMD acceleration for AEGIS-128"
 	depends on CRYPTO_AEGIS128 && ((ARM || ARM64) && KERNEL_MODE_NEON)
-	depends on !ARM || CC_IS_CLANG || GCC_VERSION >= 40800
 	default y
 
 config CRYPTO_AEGIS128_AESNI_SSE2

drivers/xen/time.c

@@ -64,7 +64,7 @@ static void xen_get_runstate_snapshot_cpu_delta(
 	do {
 		state_time = get64(&state->state_entry_time);
 		rmb();	/* Hypervisor might update data. */
-		*res = READ_ONCE(*state);
+		*res = __READ_ONCE(*state);
 		rmb();	/* Hypervisor might update data. */
 	} while (get64(&state->state_entry_time) != state_time ||
 		 (state_time & XEN_RUNSTATE_UPDATE));

include/asm-generic/barrier.h

@@ -128,10 +128,10 @@ do {									\
 #ifndef __smp_load_acquire
 #define __smp_load_acquire(p)						\
 ({									\
-	typeof(*p) ___p1 = READ_ONCE(*p);				\
+	__unqual_scalar_typeof(*p) ___p1 = READ_ONCE(*p);		\
 	compiletime_assert_atomic_type(*p);				\
 	__smp_mb();							\
-	___p1;								\
+	(typeof(*p))___p1;						\
 })
 #endif
 
@@ -183,10 +183,10 @@ do {									\
 #ifndef smp_load_acquire
 #define smp_load_acquire(p)						\
 ({									\
-	typeof(*p) ___p1 = READ_ONCE(*p);				\
+	__unqual_scalar_typeof(*p) ___p1 = READ_ONCE(*p);		\
 	compiletime_assert_atomic_type(*p);				\
 	barrier();							\
-	___p1;								\
+	(typeof(*p))___p1;						\
 })
 #endif
 
@@ -229,14 +229,14 @@ do {									\
 #ifndef smp_cond_load_relaxed
 #define smp_cond_load_relaxed(ptr, cond_expr) ({		\
 	typeof(ptr) __PTR = (ptr);				\
-	typeof(*ptr) VAL;					\
+	__unqual_scalar_typeof(*ptr) VAL;			\
 	for (;;) {						\
 		VAL = READ_ONCE(*__PTR);			\
 		if (cond_expr)					\
 			break;					\
 		cpu_relax();					\
 	}							\
-	VAL;							\
+	(typeof(*ptr))VAL;					\
 })
 #endif
 
@@ -250,10 +250,10 @@ do {									\
  */
 #ifndef smp_cond_load_acquire
 #define smp_cond_load_acquire(ptr, cond_expr) ({		\
-	typeof(*ptr) _val;					\
+	__unqual_scalar_typeof(*ptr) _val;			\
 	_val = smp_cond_load_relaxed(ptr, cond_expr);		\
 	smp_acquire__after_ctrl_dep();				\
-	_val;							\
+	(typeof(*ptr))_val;					\
 })
 #endif
 

include/linux/compiler-gcc.h

@@ -10,7 +10,8 @@
 		     + __GNUC_MINOR__ * 100	\
 		     + __GNUC_PATCHLEVEL__)
 
-#if GCC_VERSION < 40600
+/* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 */
+#if GCC_VERSION < 40800
 # error Sorry, your compiler is too old - please upgrade it.
 #endif
 
@@ -126,9 +127,7 @@
 #if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__)
 #define __HAVE_BUILTIN_BSWAP32__
 #define __HAVE_BUILTIN_BSWAP64__
-#if GCC_VERSION >= 40800
 #define __HAVE_BUILTIN_BSWAP16__
-#endif
 #endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP && !__CHECKER__ */
 
 #if GCC_VERSION >= 70000

include/linux/compiler.h

@@ -230,60 +230,6 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
 #endif
 
-#include <uapi/linux/types.h>
-
-#define __READ_ONCE_SIZE						\
-({									\
-	switch (size) {							\
-	case 1: *(__u8 *)res = *(volatile __u8 *)p; break;		\
-	case 2: *(__u16 *)res = *(volatile __u16 *)p; break;		\
-	case 4: *(__u32 *)res = *(volatile __u32 *)p; break;		\
-	case 8: *(__u64 *)res = *(volatile __u64 *)p; break;		\
-	default:							\
-		barrier();						\
-		__builtin_memcpy((void *)res, (const void *)p, size);	\
-		barrier();						\
-	}								\
-})
-
-static __always_inline
-void __read_once_size(const volatile void *p, void *res, int size)
-{
-	__READ_ONCE_SIZE;
-}
-
-#ifdef CONFIG_KASAN
-/*
- * We can't declare function 'inline' because __no_sanitize_address confilcts
- * with inlining. Attempt to inline it may cause a build failure.
- * 	https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
- * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
- */
-# define __no_kasan_or_inline __no_sanitize_address notrace __maybe_unused
-#else
-# define __no_kasan_or_inline __always_inline
-#endif
-
-static __no_kasan_or_inline
-void __read_once_size_nocheck(const volatile void *p, void *res, int size)
-{
-	__READ_ONCE_SIZE;
-}
-
-static __always_inline void __write_once_size(volatile void *p, void *res, int size)
-{
-	switch (size) {
-	case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
-	case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
-	case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
-	case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
-	default:
-		barrier();
-		__builtin_memcpy((void *)p, (const void *)res, size);
-		barrier();
-	}
-}
-
 /*
  * Prevent the compiler from merging or refetching reads or writes. The
  * compiler is also forbidden from reordering successive instances of
@@ -293,11 +239,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
  * statements.
  *
  * These two macros will also work on aggregate data types like structs or
- * unions. If the size of the accessed data type exceeds the word size of
- * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
- * fall back to memcpy(). There's at least two memcpy()s: one for the
- * __builtin_memcpy() and then one for the macro doing the copy of variable
- * - '__u' allocated on the stack.
+ * unions.
  *
  * Their two major use cases are: (1) Mediating communication between
  * process-level code and irq/NMI handlers, all running on the same CPU,
@@ -309,39 +251,77 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
 #include <asm/barrier.h>
 #include <linux/kasan-checks.h>
 
-#define __READ_ONCE(x, check)						\
+/*
+ * Use __READ_ONCE() instead of READ_ONCE() if you do not require any
+ * atomicity or dependency ordering guarantees. Note that this may result
+ * in tears!
+ */
+#define __READ_ONCE(x)	(*(const volatile __unqual_scalar_typeof(x) *)&(x))
+
+#define __READ_ONCE_SCALAR(x)						\
+({									\
+	__unqual_scalar_typeof(x) __x = __READ_ONCE(x);			\
+	smp_read_barrier_depends();					\
+	(typeof(x))__x;							\
+})
+
+#define READ_ONCE(x)							\
 ({									\
-	union { typeof(x) __val; char __c[1]; } __u;			\
-	if (check)							\
-		__read_once_size(&(x), __u.__c, sizeof(x));		\
-	else								\
-		__read_once_size_nocheck(&(x), __u.__c, sizeof(x));	\
-	smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
-	__u.__val;							\
+	compiletime_assert_rwonce_type(x);				\
+	__READ_ONCE_SCALAR(x);						\
 })
-#define READ_ONCE(x) __READ_ONCE(x, 1)
 
+#define __WRITE_ONCE(x, val)				\
+do {							\
+	*(volatile typeof(x) *)&(x) = (val);		\
+} while (0)
+
+#define WRITE_ONCE(x, val)				\
+do {							\
+	compiletime_assert_rwonce_type(x);		\
+	__WRITE_ONCE(x, val);				\
+} while (0)
+
+#ifdef CONFIG_KASAN
 /*
- * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
- * to hide memory access from KASAN.
+ * We can't declare function 'inline' because __no_sanitize_address conflicts
+ * with inlining. Attempt to inline it may cause a build failure.
+ *     https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
+ * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
  */
-#define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
+# define __no_kasan_or_inline __no_sanitize_address notrace __maybe_unused
+#else
+# define __no_kasan_or_inline __always_inline
+#endif
 
 static __no_kasan_or_inline
-unsigned long read_word_at_a_time(const void *addr)
+unsigned long __read_once_word_nocheck(const void *addr)
 {
-	kasan_check_read(addr, 1);
-	return *(unsigned long *)addr;
+	return __READ_ONCE(*(unsigned long *)addr);
 }
 
-#define WRITE_ONCE(x, val) \
+/*
+ * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need to load a
+ * word from memory atomically but without telling KASAN. This is usually
+ * used by unwinding code when walking the stack of a running process.
+ */
+#define READ_ONCE_NOCHECK(x)						\
 ({									\
-	union { typeof(x) __val; char __c[1]; } __u =	\
-		{ .__val = (__force typeof(x)) (val) }; \
-	__write_once_size(&(x), __u.__c, sizeof(x));	\
-	__u.__val;					\
+	unsigned long __x;						\
+	compiletime_assert(sizeof(x) == sizeof(__x),			\
+		"Unsupported access size for READ_ONCE_NOCHECK().");	\
+	__x = __read_once_word_nocheck(&(x));				\
+	smp_read_barrier_depends();					\
+	(typeof(x))__x;							\
 })
 
+static __no_kasan_or_inline
+unsigned long read_word_at_a_time(const void *addr)
+{
+	kasan_check_read(addr, 1);
+	return *(unsigned long *)addr;
+}
+
 #endif /* __KERNEL__ */
 
 /*
@@ -406,6 +386,16 @@ static inline void *offset_to_ptr(const int *off)
 	compiletime_assert(__native_word(t),				\
 		"Need native word sized stores/loads for atomicity.")
 
+/*
+ * Yes, this permits 64-bit accesses on 32-bit architectures. These will
+ * actually be atomic in some cases (namely Armv7 + LPAE), but for others we
+ * rely on the access being split into 2x32-bit accesses for a 32-bit quantity
+ * (e.g. a virtual address) and a strong prevailing wind.
+ */
+#define compiletime_assert_rwonce_type(t)					\
+	compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long),	\
+		"Unsupported access size for {READ,WRITE}_ONCE().")
+
 /* &a[0] degrades to a pointer: a different type from an array */
 #define __must_be_array(a)	BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
 

include/linux/compiler_types.h

@@ -218,6 +218,53 @@ struct ftrace_likely_data {
 /* Are two types/vars the same type (ignoring qualifiers)? */
 #define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
 
+/*
+ * __unqual_scalar_typeof(x) - Declare an unqualified scalar type, leaving
+ *			       non-scalar types unchanged.
+ */
+#if (defined(CONFIG_CC_IS_GCC) && CONFIG_GCC_VERSION < 40900) || defined(__CHECKER__)
+/*
+ * We build this out of a couple of helper macros in a vain attempt to
+ * help you keep your lunch down while reading it.
+ */
+#define __pick_scalar_type(x, type, otherwise)					\
+	__builtin_choose_expr(__same_type(x, type), (type)0, otherwise)
+
+/*
+ * 'char' is not type-compatible with either 'signed char' or 'unsigned char',
+ * so we include the naked type here as well as the signed/unsigned variants.
+ */
+#define __pick_integer_type(x, type, otherwise)					\
+	__pick_scalar_type(x, type,						\
+		__pick_scalar_type(x, unsigned type,				\
+			__pick_scalar_type(x, signed type, otherwise)))
+
+#define __unqual_scalar_typeof(x) typeof(					\
+	__pick_integer_type(x, char,						\
+		__pick_integer_type(x, short,					\
+			__pick_integer_type(x, int,				\
+				__pick_integer_type(x, long,			\
+					__pick_integer_type(x, long long, x))))))
+#else
+/*
+ * If supported, prefer C11 _Generic for better compile-times. As above, 'char'
+ * is not type-compatible with 'signed char', and we define a separate case.
+ */
+#define __scalar_type_to_expr_cases(type)				\
+		unsigned type:	(unsigned type)0,			\
+		signed type:	(signed type)0
+
+#define __unqual_scalar_typeof(x) typeof(				\
+		_Generic((x),						\
+			 char:	(char)0,				\
+			 __scalar_type_to_expr_cases(char),		\
+			 __scalar_type_to_expr_cases(short),		\
+			 __scalar_type_to_expr_cases(int),		\
+			 __scalar_type_to_expr_cases(long),		\
+			 __scalar_type_to_expr_cases(long long),	\
+			 default: (x)))
+#endif
+
 /* Is this type a native word size -- useful for atomic operations */
 #define __native_word(t) \
 	(sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || \

init/Kconfig

@@ -1293,7 +1293,6 @@ config LD_DEAD_CODE_DATA_ELIMINATION
 	bool "Dead code and data elimination (EXPERIMENTAL)"
 	depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
 	depends on EXPERT
-	depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
 	depends on $(cc-option,-ffunction-sections -fdata-sections)
 	depends on $(ld-option,--gc-sections)
 	help

kernel/gcov/Kconfig

@@ -51,28 +51,4 @@ config GCOV_PROFILE_ALL
 	larger and run slower. Also be sure to exclude files from profiling
 	which are not linked to the kernel image to prevent linker errors.
 
-choice
-	prompt "Specify GCOV format"
-	depends on GCOV_KERNEL
-	depends on CC_IS_GCC
-	---help---
-	The gcov format is usually determined by the GCC version, and the
-	default is chosen according to your GCC version. However, there are
-	exceptions where format changes are integrated in lower-version GCCs.
-	In such a case, change this option to adjust the format used in the
-	kernel accordingly.
-
-config GCOV_FORMAT_3_4
-	bool "GCC 3.4 format"
-	depends on GCC_VERSION < 40700
-	---help---
-	Select this option to use the format defined by GCC 3.4.
-
-config GCOV_FORMAT_4_7
-	bool "GCC 4.7 format"
-	---help---
-	Select this option to use the format defined by GCC 4.7.
-
-endchoice
-
 endmenu

kernel/gcov/Makefile

@@ -2,6 +2,5 @@
 ccflags-y := -DSRCTREE='"$(srctree)"' -DOBJTREE='"$(objtree)"'
 
 obj-y := base.o fs.o
-obj-$(CONFIG_GCOV_FORMAT_3_4) += gcc_base.o gcc_3_4.o
-obj-$(CONFIG_GCOV_FORMAT_4_7) += gcc_base.o gcc_4_7.o
+obj-$(CONFIG_CC_IS_GCC) += gcc_base.o gcc_4_7.o
 obj-$(CONFIG_CC_IS_CLANG) += clang.o

lib/fault-inject.c

@@ -106,7 +106,9 @@ bool should_fail(struct fault_attr *attr, ssize_t size)
 		unsigned int fail_nth = READ_ONCE(current->fail_nth);
 
 		if (fail_nth) {
-			if (!WRITE_ONCE(current->fail_nth, fail_nth - 1))
+			fail_nth--;
+			WRITE_ONCE(current->fail_nth, fail_nth);
+			if (!fail_nth)
 				goto fail;
 
 			return false;

net/netfilter/core.c

@@ -376,7 +376,7 @@ static bool nf_remove_net_hook(struct nf_hook_entries *old,
 		if (orig_ops[i] != unreg)
 			continue;
 		WRITE_ONCE(old->hooks[i].hook, accept_all);
-		WRITE_ONCE(orig_ops[i], &dummy_ops);
+		WRITE_ONCE(orig_ops[i], (void *)&dummy_ops);
 		return true;
 	}
 

net/tls/tls_main.c

@@ -629,7 +629,7 @@ struct tls_context *tls_ctx_create(struct sock *sk)
 static void tls_build_proto(struct sock *sk)
 {
 	int ip_ver = sk->sk_family == AF_INET6 ? TLSV6 : TLSV4;
-	const struct proto *prot = READ_ONCE(sk->sk_prot);
+	struct proto *prot = READ_ONCE(sk->sk_prot);
 
 	/* Build IPv6 TLS whenever the address of tcpv6 _prot changes */
 	if (ip_ver == TLSV6 &&

scripts/gcc-plugins/Kconfig

@@ -8,7 +8,7 @@ config HAVE_GCC_PLUGINS
 menuconfig GCC_PLUGINS
 	bool "GCC plugins"
 	depends on HAVE_GCC_PLUGINS
-	depends on CC_IS_GCC && GCC_VERSION >= 40800
+	depends on CC_IS_GCC
 	depends on $(success,$(srctree)/scripts/gcc-plugin.sh $(CC))
 	default y
 	help