[PATCH v3 00/12] Compiler Attributes

[PATCH v3 00/12] Compiler Attributes

[Miguel Ojeda]

The Compiler Attributes series is an effort to disentangle
the include/linux/compiler*.h headers and bring them up to date.

The main idea behind the series is to use feature checking macros
(i.e. __has_attribute) instead of compiler version checks (e.g. GCC_VERSION),
which are compiler-agnostic (so they can be shared, reducing the size
of compiler-specific headers) and version-agnostic.

Other related improvements have been performed in the headers as well,
which on top of the use of __has_attribute it has amounted to a significant
simplification of these headers (e.g. GCC_VERSION is now only guarding 4
non-attribute macros).

This series should also help the efforts to support compiling the kernel
with clang and icc. A fair amount of documentation and comments have also
been added, clarified or removed; and the headers are now more readable,
which should help kernel developers in general.

The series was triggered due to the move to gcc >= 4.6. In turn, this series
has also triggered Sparse to gain the ability to recognize __has_attribute
on its own.

You can also fetch it from:

  https://github.com/ojeda/linux/tree/compiler-attributes-v3

Enjoy!

Cheers,
Miguel

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Eli Friedman <efriedma@codeaurora.org>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Joe Perches <joe@perches.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-sparse@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>

v2 -> v3:

  New:

  * Remove duplicated "used" attribute in KENTRY
  * Silence sparse warnings on __has_attribute & simplify the macro block
  * Add Documentation/process/programming-language.rst
  * Improve _attribute.h description
  * Improve some commit descriptions
  * Add Reviewed-by's/Acked-by's/Suggested-by's
    (hopefully I didn't miss anybody!)
  * Rebase on top of v4.19-rc2
  * Cc Rasmus, Luc

  From reviews:

  * Fix __attribute_const__ rename typo (Nick)
  * Add SPDX identifier to _attributes.h (Nick)
  * Add SPDX identifier to _types.h (Greg)
  * Remove __attribute__ uses from compiler.h (Nick)
  * Tweak clang doc comments (Nick)
  * Move __naked out of -gcc.h to be shared (Arnd)
  * Use __name__ syntax instead (Rasmus)
  * Update sparse description (Luc)
  * Remove __CHECKER__ test from __must_be_array (Luc)
  * Add note on __has_attribute regarding sparse (Luc)
  * Cc linux-sparse (Luc)

It is quite a lot of stuff changed this time around, I hope I haven't missed
anything said in the emails. Please take a look!

Compile-tested for a while on (x86_64, gcc-7.3, allmodconfig).

Miguel Ojeda (12):
  Compiler Attributes: remove unused attributes
  Compiler Attributes: always use the extra-underscores syntax
  Compiler Attributes: remove unneeded tests
  Compiler Attributes: homogenize __must_be_array
  Compiler Attributes: naked was fixed in gcc 4.6
  Compiler Attributes: naked can be shared
  Compiler Attributes: remove unneeded sparse (__CHECKER__) tests
  Compiler Attributes: add missing SPDX ID in compiler_types.h
  Compiler Attributes: use feature checks instead of version checks
  Compiler Attributes: KENTRY used twice the "used" attribute
  Compiler Attributes: remove uses of __attribute__ from compiler.h
  Compiler Attributes: add Doc/process/programming-language.rst

 Documentation/process/index.rst               |   1 +
 .../process/programming-language.rst          |  44 ++++
 include/linux/compiler-clang.h                |   5 -
 include/linux/compiler-gcc.h                  |  84 +-----
 include/linux/compiler-intel.h                |   9 -
 include/linux/compiler.h                      |  19 +-
 include/linux/compiler_attributes.h           | 239 ++++++++++++++++++
 include/linux/compiler_types.h                | 101 ++------
 8 files changed, 314 insertions(+), 188 deletions(-)
 create mode 100644 Documentation/process/programming-language.rst
 create mode 100644 include/linux/compiler_attributes.h

-- 
2.17.1

[PATCH 01/12] Compiler Attributes: remove unused attributes

[Miguel Ojeda]

__optimize and __deprecate_for_modules are unused in
the whole kernel tree. Simply drop them.

Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Eli Friedman <efriedma@codeaurora.org>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Joe Perches <joe@perches.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-sparse@vger.kernel.org
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
---
 include/linux/compiler-gcc.h   | 2 --
 include/linux/compiler.h       | 4 ----
 include/linux/compiler_types.h | 1 -
 3 files changed, 7 deletions(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 763bbad1e258..0a2d06677d83 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -95,8 +95,6 @@
 
 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
 
-#define __optimize(level)	__attribute__((__optimize__(level)))
-
 #define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
 
 #ifndef __CHECKER__
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 681d866efb1e..7c0157d50964 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -301,10 +301,6 @@ static inline void *offset_to_ptr(const int *off)
 
 #endif /* __ASSEMBLY__ */
 
-#ifndef __optimize
-# define __optimize(level)
-#endif
-
 /* Compile time object size, -1 for unknown */
 #ifndef __compiletime_object_size
 # define __compiletime_object_size(obj) -1
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 3525c179698c..b6534292ea33 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -108,7 +108,6 @@ struct ftrace_likely_data {
 
 /* Don't. Just don't. */
 #define __deprecated
-#define __deprecated_for_modules
 
 #endif /* __KERNEL__ */
 
-- 
2.17.1

[PATCH 02/12] Compiler Attributes: always use the extra-underscores syntax

[Miguel Ojeda]

The attribute syntax optionally allows to surround attribute names
with "__" in order to avoid collisions with macros of the same name
(see https://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html).

This homogenizes all attributes to use the syntax with underscores.
While there are currently only a handful of cases of some TUs defining
macros like "error" which may collide with the attributes,
this should prevent futures surprises.

This has been done only for "standard" attributes supported by
the major compilers. In other words, those of third-party tools
(e.g. sparse, plugins...) have not been changed for the moment.

Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Eli Friedman <efriedma@codeaurora.org>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Joe Perches <joe@perches.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-sparse@vger.kernel.org
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
---
 include/linux/compiler-clang.h |  2 +-
 include/linux/compiler-gcc.h   | 14 ++++++------
 include/linux/compiler-intel.h |  2 +-
 include/linux/compiler.h       |  8 +++----
 include/linux/compiler_types.h | 40 +++++++++++++++++-----------------
 5 files changed, 33 insertions(+), 33 deletions(-)

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index b1ce500fe8b3..d11cad61ba5c 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -21,7 +21,7 @@
 #define __SANITIZE_ADDRESS__
 #endif
 
-#define __no_sanitize_address __attribute__((no_sanitize("address")))
+#define __no_sanitize_address __attribute__((__no_sanitize__("address")))
 
 /*
  * Not all versions of clang implement the the type-generic versions
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 0a2d06677d83..371b6fa2d074 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -76,7 +76,7 @@
 #endif
 
 #ifdef RETPOLINE
-#define __noretpoline __attribute__((indirect_branch("keep")))
+#define __noretpoline __attribute__((__indirect_branch__("keep")))
 #endif
 
 /*
@@ -91,15 +91,15 @@
  * GCC 4.[56] currently fail to enforce this, so we must do so ourselves.
  * See GCC PR44290.
  */
-#define __naked		__attribute__((naked)) noinline __noclone notrace
+#define __naked		__attribute__((__naked__)) noinline __noclone notrace
 
 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
 
 #define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
 
 #ifndef __CHECKER__
-#define __compiletime_warning(message) __attribute__((warning(message)))
-#define __compiletime_error(message) __attribute__((error(message)))
+#define __compiletime_warning(message) __attribute__((__warning__(message)))
+#define __compiletime_error(message) __attribute__((__error__(message)))
 
 #ifdef LATENT_ENTROPY_PLUGIN
 #define __latent_entropy __attribute__((latent_entropy))
@@ -148,7 +148,7 @@
  * optimizer that something else uses this function or variable, thus preventing
  * this.
  */
-#define __visible	__attribute__((externally_visible))
+#define __visible	__attribute__((__externally_visible__))
 
 /* gcc version specific checks */
 
@@ -205,7 +205,7 @@
  * should not be applied to that function.
  * Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
  */
-#define __no_sanitize_address __attribute__((no_sanitize_address))
+#define __no_sanitize_address __attribute__((__no_sanitize_address__))
 #endif
 
 #if GCC_VERSION >= 50100
@@ -213,7 +213,7 @@
  * Mark structures as requiring designated initializers.
  * https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html
  */
-#define __designated_init __attribute__((designated_init))
+#define __designated_init __attribute__((__designated_init__))
 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
 #endif
 
diff --git a/include/linux/compiler-intel.h b/include/linux/compiler-intel.h
index 4c7f9befa9f6..fef8bb3e53ef 100644
--- a/include/linux/compiler-intel.h
+++ b/include/linux/compiler-intel.h
@@ -42,4 +42,4 @@
  * and may be redefined here because they should not be shared with other
  * compilers, like clang.
  */
-#define __visible	__attribute__((externally_visible))
+#define __visible	__attribute__((__externally_visible__))
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 7c0157d50964..ec4a28bad2c6 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -24,7 +24,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 			long ______r;					\
 			static struct ftrace_likely_data		\
 				__attribute__((__aligned__(4)))		\
-				__attribute__((section("_ftrace_annotated_branch"))) \
+				__attribute__((__section__("_ftrace_annotated_branch"))) \
 				______f = {				\
 				.data.func = __func__,			\
 				.data.file = __FILE__,			\
@@ -60,7 +60,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 		int ______r;						\
 		static struct ftrace_branch_data			\
 			__attribute__((__aligned__(4)))			\
-			__attribute__((section("_ftrace_branch")))	\
+			__attribute__((__section__("_ftrace_branch")))	\
 			______f = {					\
 				.func = __func__,			\
 				.file = __FILE__,			\
@@ -146,7 +146,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 	extern typeof(sym) sym;					\
 	static const unsigned long __kentry_##sym		\
 	__used							\
-	__attribute__((section("___kentry" "+" #sym ), used))	\
+	__attribute__((__section__("___kentry" "+" #sym ), used))	\
 	= (unsigned long)&sym;
 #endif
 
@@ -287,7 +287,7 @@ unsigned long read_word_at_a_time(const void *addr)
  * visible to the compiler.
  */
 #define __ADDRESSABLE(sym) \
-	static void * __attribute__((section(".discard.addressable"), used)) \
+	static void * __attribute__((__section__(".discard.addressable"), used)) \
 		__PASTE(__addressable_##sym, __LINE__) = (void *)&sym;
 
 /**
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index b6534292ea33..2bc0f94df38e 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -195,26 +195,26 @@ struct ftrace_likely_data {
  * would be.
  * [...]
  */
-#define __pure			__attribute__((pure))
-#define __aligned(x)		__attribute__((aligned(x)))
-#define __aligned_largest	__attribute__((aligned))
-#define __printf(a, b)		__attribute__((format(printf, a, b)))
-#define __scanf(a, b)		__attribute__((format(scanf, a, b)))
-#define __maybe_unused		__attribute__((unused))
-#define __always_unused		__attribute__((unused))
-#define __mode(x)		__attribute__((mode(x)))
+#define __pure			__attribute__((__pure__))
+#define __aligned(x)		__attribute__((__aligned__(x)))
+#define __aligned_largest	__attribute__((__aligned__))
+#define __printf(a, b)		__attribute__((__format__(printf, a, b)))
+#define __scanf(a, b)		__attribute__((__format__(scanf, a, b)))
+#define __maybe_unused		__attribute__((__unused__))
+#define __always_unused		__attribute__((__unused__))
+#define __mode(x)		__attribute__((__mode__(x)))
 #define __malloc		__attribute__((__malloc__))
 #define __used			__attribute__((__used__))
-#define __noreturn		__attribute__((noreturn))
-#define __packed		__attribute__((packed))
-#define __weak			__attribute__((weak))
-#define __alias(symbol)		__attribute__((alias(#symbol)))
-#define __cold			__attribute__((cold))
+#define __noreturn		__attribute__((__noreturn__))
+#define __packed		__attribute__((__packed__))
+#define __weak			__attribute__((__weak__))
+#define __alias(symbol)		__attribute__((__alias__(#symbol)))
+#define __cold			__attribute__((__cold__))
 #define __section(S)		__attribute__((__section__(#S)))
 
 
 #ifdef CONFIG_ENABLE_MUST_CHECK
-#define __must_check		__attribute__((warn_unused_result))
+#define __must_check		__attribute__((__warn_unused_result__))
 #else
 #define __must_check
 #endif
@@ -222,7 +222,7 @@ struct ftrace_likely_data {
 #if defined(CC_USING_HOTPATCH) && !defined(__CHECKER__)
 #define notrace			__attribute__((hotpatch(0, 0)))
 #else
-#define notrace			__attribute__((no_instrument_function))
+#define notrace			__attribute__((__no_instrument_function__))
 #endif
 
 #define __compiler_offsetof(a, b)	__builtin_offsetof(a, b)
@@ -234,7 +234,7 @@ struct ftrace_likely_data {
  * defined so the gnu89 semantics are the default.
  */
 #ifdef __GNUC_STDC_INLINE__
-# define __gnu_inline	__attribute__((gnu_inline))
+# define __gnu_inline	__attribute__((__gnu_inline__))
 #else
 # define __gnu_inline
 #endif
@@ -254,17 +254,17 @@ struct ftrace_likely_data {
 #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
 	!defined(CONFIG_OPTIMIZE_INLINING)
 #define inline \
-	inline __attribute__((always_inline, unused)) notrace __gnu_inline
+	inline __attribute__((__always_inline__, __unused__)) notrace __gnu_inline
 #else
-#define inline inline	__attribute__((unused)) notrace __gnu_inline
+#define inline inline	__attribute__((__unused__)) notrace __gnu_inline
 #endif
 
 #define __inline__ inline
 #define __inline inline
-#define noinline	__attribute__((noinline))
+#define noinline	__attribute__((__noinline__))
 
 #ifndef __always_inline
-#define __always_inline inline __attribute__((always_inline))
+#define __always_inline inline __attribute__((__always_inline__))
 #endif
 
 /*
-- 
2.17.1

[PATCH 03/12] Compiler Attributes: remove unneeded tests

[Miguel Ojeda]

Attributes const and always_inline have tests around them
which are unneeded, since they are supported by gcc >= 4.6,
clang >= 3 and icc >= 13. https://godbolt.org/z/DFPq37

In the case of gnu_inline, we do not need to test for
__GNUC_STDC_INLINE__ because, regardless of the current
inlining behavior, we can simply always force the old
GCC inlining behavior by using the attribute in all cases.

Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Eli Friedman <efriedma@codeaurora.org>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Joe Perches <joe@perches.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-sparse@vger.kernel.org
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
---
 include/linux/compiler_types.h | 24 +++---------------------
 1 file changed, 3 insertions(+), 21 deletions(-)

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 2bc0f94df38e..759b3fea9216 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -158,10 +158,6 @@ struct ftrace_likely_data {
 	(sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || \
 	 sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
 
-#ifndef __attribute_const__
-#define __attribute_const__	__attribute__((__const__))
-#endif
-
 #ifndef __noclone
 #define __noclone
 #endif
@@ -196,6 +192,7 @@ struct ftrace_likely_data {
  * [...]
  */
 #define __pure			__attribute__((__pure__))
+#define __attribute_const__	__attribute__((__const__))
 #define __aligned(x)		__attribute__((__aligned__(x)))
 #define __aligned_largest	__attribute__((__aligned__))
 #define __printf(a, b)		__attribute__((__format__(printf, a, b)))
@@ -211,7 +208,8 @@ struct ftrace_likely_data {
 #define __alias(symbol)		__attribute__((__alias__(#symbol)))
 #define __cold			__attribute__((__cold__))
 #define __section(S)		__attribute__((__section__(#S)))
-
+#define __gnu_inline		__attribute__((__gnu_inline__))
+#define __always_inline		inline __attribute__((__always_inline__))
 
 #ifdef CONFIG_ENABLE_MUST_CHECK
 #define __must_check		__attribute__((__warn_unused_result__))
@@ -227,18 +225,6 @@ struct ftrace_likely_data {
 
 #define __compiler_offsetof(a, b)	__builtin_offsetof(a, b)
 
-/*
- * Feature detection for gnu_inline (gnu89 extern inline semantics). Either
- * __GNUC_STDC_INLINE__ is defined (not using gnu89 extern inline semantics,
- * and we opt in to the gnu89 semantics), or __GNUC_STDC_INLINE__ is not
- * defined so the gnu89 semantics are the default.
- */
-#ifdef __GNUC_STDC_INLINE__
-# define __gnu_inline	__attribute__((__gnu_inline__))
-#else
-# define __gnu_inline
-#endif
-
 /*
  * Force always-inline if the user requests it so via the .config.
  * GCC does not warn about unused static inline functions for
@@ -263,10 +249,6 @@ struct ftrace_likely_data {
 #define __inline inline
 #define noinline	__attribute__((__noinline__))
 
-#ifndef __always_inline
-#define __always_inline inline __attribute__((__always_inline__))
-#endif
-
 /*
  * Rather then using noinline to prevent stack consumption, use
  * noinline_for_stack instead.  For documentation reasons.
-- 
2.17.1

[PATCH 04/12] Compiler Attributes: homogenize __must_be_array

[Miguel Ojeda]

Different definitions of __must_be_array:

  * gcc: disabled for __CHECKER__

  * clang: same definition as gcc's, but without __CHECKER__

  * intel: the comment claims __builtin_types_compatible_p()
    is unsupported; but icc seems to support it since 13.0.1
    (released in 2012). See https://godbolt.org/z/S0l6QQ

Therefore, we can remove all of them and have a single definition
in compiler.h

Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Eli Friedman <efriedma@codeaurora.org>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Joe Perches <joe@perches.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-sparse@vger.kernel.org
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
---
 include/linux/compiler-clang.h | 1 -
 include/linux/compiler-gcc.h   | 7 -------
 include/linux/compiler-intel.h | 3 ---
 include/linux/compiler.h       | 7 +++++++
 4 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index d11cad61ba5c..fa9532f8d885 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -41,6 +41,5 @@
  * compilers, like ICC.
  */
 #define barrier() __asm__ __volatile__("" : : : "memory")
-#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
 #define __assume_aligned(a, ...)	\
 	__attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 371b6fa2d074..76f4907ef707 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -68,13 +68,6 @@
  */
 #define uninitialized_var(x) x = x
 
-#ifdef __CHECKER__
-#define __must_be_array(a)	0
-#else
-/* &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]))
-#endif
-
 #ifdef RETPOLINE
 #define __noretpoline __attribute__((__indirect_branch__("keep")))
 #endif
diff --git a/include/linux/compiler-intel.h b/include/linux/compiler-intel.h
index fef8bb3e53ef..6004b4588bd4 100644
--- a/include/linux/compiler-intel.h
+++ b/include/linux/compiler-intel.h
@@ -29,9 +29,6 @@
  */
 #define OPTIMIZER_HIDE_VAR(var) barrier()
 
-/* Intel ECC compiler doesn't support __builtin_types_compatible_p() */
-#define __must_be_array(a) 0
-
 #endif
 
 /* icc has this, but it's called _bswap16 */
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index ec4a28bad2c6..165b1d5683ed 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -357,4 +357,11 @@ static inline void *offset_to_ptr(const int *off)
 	compiletime_assert(__native_word(t),				\
 		"Need native word sized stores/loads for atomicity.")
 
+#ifdef __CHECKER__
+#define __must_be_array(a)	0
+#else
+/* &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]))
+#endif
+
 #endif /* __LINUX_COMPILER_H */
-- 
2.17.1

[PATCH 05/12] Compiler Attributes: naked was fixed in gcc 4.6

[Miguel Ojeda]

Commit 9c695203a7dd ("compiler-gcc.h: gcc-4.5 needs noclone
and noinline on __naked functions") added noinline and noclone
as a workaround for a gcc 4.5 bug, which was resolved in 4.6.0.

Since now the minimum gcc supported version is 4.6,
we can clean it up.

See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44290
and https://godbolt.org/z/h6NMIL

Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Eli Friedman <efriedma@codeaurora.org>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Joe Perches <joe@perches.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-sparse@vger.kernel.org
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
---
 include/linux/compiler-gcc.h | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 76f4907ef707..4cd5e9264bce 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -77,14 +77,8 @@
  * to trace naked functions because then mcount is called without
  * stack and frame pointer being set up and there is no chance to
  * restore the lr register to the value before mcount was called.
- *
- * The asm() bodies of naked functions often depend on standard calling
- * conventions, therefore they must be noinline and noclone.
- *
- * GCC 4.[56] currently fail to enforce this, so we must do so ourselves.
- * See GCC PR44290.
  */
-#define __naked		__attribute__((__naked__)) noinline __noclone notrace
+#define __naked		__attribute__((__naked__)) notrace
 
 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
 
-- 
2.17.1

[PATCH 06/12] Compiler Attributes: naked can be shared

[Miguel Ojeda]

The naked attribute is supported by at least gcc >= 4.6 (for ARM,
which is the only current user), gcc >= 8 (for x86), clang >= 3.1
and icc >= 13. See https://godbolt.org/z/350Dyc

Therefore, move it out of compiler-gcc.h so that the definition
is shared by all compilers.

Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Eli Friedman <efriedma@codeaurora.org>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Joe Perches <joe@perches.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-sparse@vger.kernel.org
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
---
 include/linux/compiler-gcc.h   | 8 --------
 include/linux/compiler_types.h | 8 ++++++++
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 4cd5e9264bce..3b32bbfa5a49 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -72,14 +72,6 @@
 #define __noretpoline __attribute__((__indirect_branch__("keep")))
 #endif
 
-/*
- * it doesn't make sense on ARM (currently the only user of __naked)
- * to trace naked functions because then mcount is called without
- * stack and frame pointer being set up and there is no chance to
- * restore the lr register to the value before mcount was called.
- */
-#define __naked		__attribute__((__naked__)) notrace
-
 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
 
 #define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 759b3fea9216..f182f2ef3227 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -223,6 +223,14 @@ struct ftrace_likely_data {
 #define notrace			__attribute__((__no_instrument_function__))
 #endif
 
+/*
+ * it doesn't make sense on ARM (currently the only user of __naked)
+ * to trace naked functions because then mcount is called without
+ * stack and frame pointer being set up and there is no chance to
+ * restore the lr register to the value before mcount was called.
+ */
+#define __naked			__attribute__((__naked__)) notrace
+
 #define __compiler_offsetof(a, b)	__builtin_offsetof(a, b)
 
 /*
-- 
2.17.1

[PATCH 07/12] Compiler Attributes: remove unneeded sparse (__CHECKER__) tests

[Miguel Ojeda]

Sparse knows about a few more attributes now, so we can remove
the __CHECKER__ conditions from them (which, in turn, allow us
to move some of them later on to compiler_attributes.h).

  * assume_aligned: since sparse's commit ffc860b ("sparse:
    ignore __assume_aligned__ attribute"), included in 0.5.1

  * error: since sparse's commit 0a04210 ("sparse: Add 'error'
    to ignored attributes"), included in 0.5.0

  * hotpatch: since sparse's commit 6043210 ("sparse/parse.c:
    ignore hotpatch attribute"), included in 0.5.1

  * warning: since sparse's commit 977365d ("Avoid "attribute
    'warning': unknown attribute" warning"), included in 0.4.2

On top of that, __must_be_array does not need it either because:

  * Even ancient versions of sparse do not have a problem

  * BUILD_BUG_ON_ZERO() is currently disabled for __CHECKER__

Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Eli Friedman <efriedma@codeaurora.org>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Joe Perches <joe@perches.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-sparse@vger.kernel.org
Acked-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
---
 include/linux/compiler-gcc.h   | 6 ++----
 include/linux/compiler.h       | 4 ----
 include/linux/compiler_types.h | 2 +-
 3 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 3b32bbfa5a49..1ca6a51cfaa9 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -76,14 +76,12 @@
 
 #define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
 
-#ifndef __CHECKER__
 #define __compiletime_warning(message) __attribute__((__warning__(message)))
 #define __compiletime_error(message) __attribute__((__error__(message)))
 
-#ifdef LATENT_ENTROPY_PLUGIN
+#if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__)
 #define __latent_entropy __attribute__((latent_entropy))
 #endif
-#endif /* __CHECKER__ */
 
 /*
  * calling noreturn functions, __builtin_unreachable() and __builtin_trap()
@@ -131,7 +129,7 @@
 
 /* gcc version specific checks */
 
-#if GCC_VERSION >= 40900 && !defined(__CHECKER__)
+#if GCC_VERSION >= 40900
 /*
  * __assume_aligned(n, k): Tell the optimizer that the returned
  * pointer can be assumed to be k modulo n. The second argument is
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 165b1d5683ed..4030a2940d6b 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -357,11 +357,7 @@ static inline void *offset_to_ptr(const int *off)
 	compiletime_assert(__native_word(t),				\
 		"Need native word sized stores/loads for atomicity.")
 
-#ifdef __CHECKER__
-#define __must_be_array(a)	0
-#else
 /* &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]))
-#endif
 
 #endif /* __LINUX_COMPILER_H */
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index f182f2ef3227..65b10b1e2a59 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -217,7 +217,7 @@ struct ftrace_likely_data {
 #define __must_check
 #endif
 
-#if defined(CC_USING_HOTPATCH) && !defined(__CHECKER__)
+#if defined(CC_USING_HOTPATCH)
 #define notrace			__attribute__((hotpatch(0, 0)))
 #else
 #define notrace			__attribute__((__no_instrument_function__))
-- 
2.17.1

[PATCH 08/12] Compiler Attributes: add missing SPDX ID in compiler_types.h

[Miguel Ojeda]

Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Eli Friedman <efriedma@codeaurora.org>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Joe Perches <joe@perches.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-sparse@vger.kernel.org
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
---
 include/linux/compiler_types.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 65b10b1e2a59..0cb40df59418 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: GPL-2.0 */
 #ifndef __LINUX_COMPILER_TYPES_H
 #define __LINUX_COMPILER_TYPES_H
 
-- 
2.17.1

[PATCH 09/12] Compiler Attributes: use feature checks instead of version checks

[Miguel Ojeda]

Instead of using version checks per-compiler to define (or not)
each attribute, use __has_attribute to test for them, following
the cleanup started with commit 815f0ddb346c
("include/linux/compiler*.h: make compiler-*.h mutually exclusive"),
which is supported on gcc >= 5, clang >= 2.9 and icc >= 17.
In the meantime, to support 4.6 <= gcc < 5, we implement
__has_attribute by hand.

All the attributes that can be unconditionally defined and directly
map to compiler attribute(s) (even if optional) have been moved
to a new file include/linux/compiler_attributes.h

In an effort to make the file as regular as possible, comments
stating the purpose of attributes have been removed. Instead,
links to the compiler docs have been added (i.e. to gcc and,
if available, to clang as well). In addition, they have been sorted.

Finally, if an attribute is optional (i.e. if it is guarded
by __has_attribute), the reason has been stated for future reference.

Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Eli Friedman <efriedma@codeaurora.org>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Joe Perches <joe@perches.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-sparse@vger.kernel.org
Reviewed-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
---
 include/linux/compiler-clang.h      |   4 -
 include/linux/compiler-gcc.h        |  51 ------
 include/linux/compiler-intel.h      |   6 -
 include/linux/compiler_attributes.h | 239 ++++++++++++++++++++++++++++
 include/linux/compiler_types.h      |  69 +-------
 5 files changed, 245 insertions(+), 124 deletions(-)
 create mode 100644 include/linux/compiler_attributes.h

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index fa9532f8d885..3e7dafb3ea80 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -21,8 +21,6 @@
 #define __SANITIZE_ADDRESS__
 #endif
 
-#define __no_sanitize_address __attribute__((__no_sanitize__("address")))
-
 /*
  * Not all versions of clang implement the the type-generic versions
  * of the builtin overflow checkers. Fortunately, clang implements
@@ -41,5 +39,3 @@
  * compilers, like ICC.
  */
 #define barrier() __asm__ __volatile__("" : : : "memory")
-#define __assume_aligned(a, ...)	\
-	__attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 1ca6a51cfaa9..cfac027e1625 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -108,9 +108,6 @@
 		__builtin_unreachable();	\
 	} while (0)
 
-/* Mark a function definition as prohibited from being cloned. */
-#define __noclone	__attribute__((__noclone__, __optimize__("no-tracer")))
-
 #if defined(RANDSTRUCT_PLUGIN) && !defined(__CHECKER__)
 #define __randomize_layout __attribute__((randomize_layout))
 #define __no_randomize_layout __attribute__((no_randomize_layout))
@@ -119,32 +116,6 @@
 #define randomized_struct_fields_end	} __randomize_layout;
 #endif
 
-/*
- * When used with Link Time Optimization, gcc can optimize away C functions or
- * variables which are referenced only from assembly code.  __visible tells the
- * optimizer that something else uses this function or variable, thus preventing
- * this.
- */
-#define __visible	__attribute__((__externally_visible__))
-
-/* gcc version specific checks */
-
-#if GCC_VERSION >= 40900
-/*
- * __assume_aligned(n, k): Tell the optimizer that the returned
- * pointer can be assumed to be k modulo n. The second argument is
- * optional (default 0), so we use a variadic macro to make the
- * shorthand.
- *
- * Beware: Do not apply this to functions which may return
- * ERR_PTRs. Also, it is probably unwise to apply it to functions
- * returning extra information in the low bits (but in that case the
- * compiler should see some alignment anyway, when the return value is
- * massaged by 'flags = ptr & 3; ptr &= ~3;').
- */
-#define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
-#endif
-
 /*
  * GCC 'asm goto' miscompiles certain code sequences:
  *
@@ -176,32 +147,10 @@
 #define KASAN_ABI_VERSION 3
 #endif
 
-#if GCC_VERSION >= 40902
-/*
- * Tell the compiler that address safety instrumentation (KASAN)
- * should not be applied to that function.
- * Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
- */
-#define __no_sanitize_address __attribute__((__no_sanitize_address__))
-#endif
-
 #if GCC_VERSION >= 50100
-/*
- * Mark structures as requiring designated initializers.
- * https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html
- */
-#define __designated_init __attribute__((__designated_init__))
 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
 #endif
 
-#if !defined(__noclone)
-#define __noclone	/* not needed */
-#endif
-
-#if !defined(__no_sanitize_address)
-#define __no_sanitize_address
-#endif
-
 /*
  * Turn individual warnings and errors on and off locally, depending
  * on version.
diff --git a/include/linux/compiler-intel.h b/include/linux/compiler-intel.h
index 6004b4588bd4..517bd14e1222 100644
--- a/include/linux/compiler-intel.h
+++ b/include/linux/compiler-intel.h
@@ -34,9 +34,3 @@
 /* icc has this, but it's called _bswap16 */
 #define __HAVE_BUILTIN_BSWAP16__
 #define __builtin_bswap16 _bswap16
-
-/* The following are for compatibility with GCC, from compiler-gcc.h,
- * and may be redefined here because they should not be shared with other
- * compilers, like clang.
- */
-#define __visible	__attribute__((__externally_visible__))
diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
new file mode 100644
index 000000000000..ac7bf47ee9cd
--- /dev/null
+++ b/include/linux/compiler_attributes.h
@@ -0,0 +1,239 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_COMPILER_ATTRIBUTES_H
+#define __LINUX_COMPILER_ATTRIBUTES_H
+
+/*
+ * The attributes in this file are unconditionally defined and they directly
+ * map to compiler attribute(s) -- except those that are optional.
+ *
+ * Any other "attributes" (i.e. those that depend on a configuration option,
+ * on a compiler, on an architecture, on plugins, on other attributes...)
+ * should be defined elsewhere (e.g. compiler_types.h or compiler-*.h).
+ *
+ * This file is meant to be sorted (by actual attribute name,
+ * not by #define identifier). Use the __attribute__((__name__)) syntax
+ * (i.e. with underscores) to avoid future collisions with other macros.
+ * If an attribute is optional, state the reason in the comment.
+ */
+
+/*
+ * To check for optional attributes, we use __has_attribute, which is supported
+ * on gcc >= 5, clang >= 2.9 and icc >= 17. In the meantime, to support
+ * 4.6 <= gcc < 5, we implement __has_attribute by hand.
+ *
+ * sparse does not support __has_attribute (yet) and defines __GNUC_MINOR__
+ * depending on the compiler used to build it; however, these attributes have
+ * no semantic effects for sparse, so it does not matter. Also note that,
+ * in order to avoid sparse's warnings, even the unsupported ones must be
+ * defined to 0.
+ */
+#ifndef __has_attribute
+# define __has_attribute(x) __GCC4_has_attribute_##x
+# define __GCC4_has_attribute___assume_aligned__      (__GNUC_MINOR__ >= 9)
+# define __GCC4_has_attribute___designated_init__     0
+# define __GCC4_has_attribute___externally_visible__  1
+# define __GCC4_has_attribute___noclone__             1
+# define __GCC4_has_attribute___optimize__            1
+# define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
+#endif
+
+/*
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
+ */
+#define __alias(symbol)                 __attribute__((__alias__(#symbol)))
+
+/*
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
+ */
+#define __aligned(x)                    __attribute__((__aligned__(x)))
+#define __aligned_largest               __attribute__((__aligned__))
+
+/*
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
+ * clang: mentioned
+ */
+#define __always_inline                 inline __attribute__((__always_inline__))
+
+/*
+ * The second argument is optional (default 0), so we use a variadic macro
+ * to make the shorthand.
+ *
+ * Beware: Do not apply this to functions which may return
+ * ERR_PTRs. Also, it is probably unwise to apply it to functions
+ * returning extra information in the low bits (but in that case the
+ * compiler should see some alignment anyway, when the return value is
+ * massaged by 'flags = ptr & 3; ptr &= ~3;').
+ *
+ * Optional: only supported since gcc >= 4.9
+ * Optional: not supported by icc
+ *
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
+ */
+#if __has_attribute(__assume_aligned__)
+# define __assume_aligned(a, ...)       __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
+#else
+# define __assume_aligned(a, ...)
+#endif
+
+/*
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
+ */
+#define __cold                          __attribute__((__cold__))
+
+/*
+ * Note the long name.
+ *
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
+ */
+#define __attribute_const__             __attribute__((__const__))
+
+/*
+ * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
+ * attribute warnings entirely and for good") for more information.
+ *
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
+ */
+#define __deprecated
+
+/*
+ * Optional: only supported since gcc >= 5.1
+ * Optional: not supported by clang
+ * Optional: not supported by icc
+ *
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
+ */
+#if __has_attribute(__designated_init__)
+# define __designated_init              __attribute__((__designated_init__))
+#else
+# define __designated_init
+#endif
+
+/*
+ * Optional: not supported by clang
+ *
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
+ */
+#if __has_attribute(__externally_visible__)
+# define __visible                      __attribute__((__externally_visible__))
+#else
+# define __visible
+#endif
+
+/*
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#format
+ */
+#define __printf(a, b)                  __attribute__((__format__(printf, a, b)))
+#define __scanf(a, b)                   __attribute__((__format__(scanf, a, b)))
+
+/*
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
+ */
+#define __gnu_inline                    __attribute__((__gnu_inline__))
+
+/*
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
+ */
+#define __malloc                        __attribute__((__malloc__))
+
+/*
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
+ */
+#define __mode(x)                       __attribute__((__mode__(x)))
+
+/*
+ * Optional: not supported by clang
+ * Note: icc does not recognize gcc's no-tracer
+ *
+ *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
+ *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-optimize-function-attribute
+ */
+#if __has_attribute(__noclone__)
+# if __has_attribute(__optimize__)
+#  define __noclone                     __attribute__((__noclone__, __optimize__("no-tracer")))
+# else
+#  define __noclone                     __attribute__((__noclone__))
+# endif
+#else
+# define __noclone
+#endif
+
+/*
+ * Note the missing underscores.
+ *
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
+ * clang: mentioned
+ */
+#define   noinline                      __attribute__((__noinline__))
+
+/*
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
+ */
+#define __noreturn                      __attribute__((__noreturn__))
+
+/*
+ * Optional: only supported since gcc >= 4.8
+ * Optional: not supported by icc
+ *
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fsanitize_005faddress-function-attribute
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#no-sanitize-address-no-address-safety-analysis
+ */
+#if __has_attribute(__no_sanitize_address__)
+# define __no_sanitize_address          __attribute__((__no_sanitize_address__))
+#else
+# define __no_sanitize_address
+#endif
+
+/*
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
+ * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
+ */
+#define __packed                        __attribute__((__packed__))
+
+/*
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
+ */
+#define __pure                          __attribute__((__pure__))
+
+/*
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
+ */
+#define __section(S)                    __attribute__((__section__(#S)))
+
+/*
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
+ */
+#define __always_unused                 __attribute__((__unused__))
+#define __maybe_unused                  __attribute__((__unused__))
+
+/*
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
+ */
+#define __used                          __attribute__((__used__))
+
+/*
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
+ */
+#define __weak                          __attribute__((__weak__))
+
+#endif /* __LINUX_COMPILER_ATTRIBUTES_H */
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 0cb40df59418..0919865473d1 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -55,6 +55,9 @@ extern void __chk_io_ptr(const volatile void __iomem *);
 
 #ifdef __KERNEL__
 
+/* Attributes */
+#include <linux/compiler_attributes.h>
+
 /* Compiler specific macros. */
 #ifdef __clang__
 #include <linux/compiler-clang.h>
@@ -79,12 +82,6 @@ extern void __chk_io_ptr(const volatile void __iomem *);
 #include <asm/compiler.h>
 #endif
 
-/*
- * Generic compiler-independent macros required for kernel
- * build go below this comment. Actual compiler/compiler version
- * specific implementations come from the above header files
- */
-
 struct ftrace_branch_data {
 	const char *func;
 	const char *file;
@@ -107,9 +104,6 @@ struct ftrace_likely_data {
 	unsigned long			constant;
 };
 
-/* Don't. Just don't. */
-#define __deprecated
-
 #endif /* __KERNEL__ */
 
 #endif /* __ASSEMBLY__ */
@@ -119,10 +113,6 @@ struct ftrace_likely_data {
  * compilers. We don't consider that to be an error, so set them to nothing.
  * For example, some of them are for compiler specific plugins.
  */
-#ifndef __designated_init
-# define __designated_init
-#endif
-
 #ifndef __latent_entropy
 # define __latent_entropy
 #endif
@@ -140,17 +130,6 @@ struct ftrace_likely_data {
 # define randomized_struct_fields_end
 #endif
 
-#ifndef __visible
-#define __visible
-#endif
-
-/*
- * Assume alignment of return value.
- */
-#ifndef __assume_aligned
-#define __assume_aligned(a, ...)
-#endif
-
 /* Are two types/vars the same type (ignoring qualifiers)? */
 #define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
 
@@ -159,10 +138,6 @@ struct ftrace_likely_data {
 	(sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || \
 	 sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
 
-#ifndef __noclone
-#define __noclone
-#endif
-
 /* Helpers for emitting diagnostics in pragmas. */
 #ifndef __diag
 #define __diag(string)
@@ -182,36 +157,6 @@ struct ftrace_likely_data {
 #define __diag_error(compiler, version, option, comment) \
 	__diag_ ## compiler(version, error, option)
 
-/*
- * From the GCC manual:
- *
- * Many functions have no effects except the return value and their
- * return value depends only on the parameters and/or global
- * variables.  Such a function can be subject to common subexpression
- * elimination and loop optimization just as an arithmetic operator
- * would be.
- * [...]
- */
-#define __pure			__attribute__((__pure__))
-#define __attribute_const__	__attribute__((__const__))
-#define __aligned(x)		__attribute__((__aligned__(x)))
-#define __aligned_largest	__attribute__((__aligned__))
-#define __printf(a, b)		__attribute__((__format__(printf, a, b)))
-#define __scanf(a, b)		__attribute__((__format__(scanf, a, b)))
-#define __maybe_unused		__attribute__((__unused__))
-#define __always_unused		__attribute__((__unused__))
-#define __mode(x)		__attribute__((__mode__(x)))
-#define __malloc		__attribute__((__malloc__))
-#define __used			__attribute__((__used__))
-#define __noreturn		__attribute__((__noreturn__))
-#define __packed		__attribute__((__packed__))
-#define __weak			__attribute__((__weak__))
-#define __alias(symbol)		__attribute__((__alias__(#symbol)))
-#define __cold			__attribute__((__cold__))
-#define __section(S)		__attribute__((__section__(#S)))
-#define __gnu_inline		__attribute__((__gnu_inline__))
-#define __always_inline		inline __attribute__((__always_inline__))
-
 #ifdef CONFIG_ENABLE_MUST_CHECK
 #define __must_check		__attribute__((__warn_unused_result__))
 #else
@@ -248,15 +193,13 @@ struct ftrace_likely_data {
  */
 #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
 	!defined(CONFIG_OPTIMIZE_INLINING)
-#define inline \
-	inline __attribute__((__always_inline__, __unused__)) notrace __gnu_inline
+#define inline __always_inline __gnu_inline __maybe_unused notrace
 #else
-#define inline inline	__attribute__((__unused__)) notrace __gnu_inline
+#define inline          inline __gnu_inline __maybe_unused notrace
 #endif
 
 #define __inline__ inline
-#define __inline inline
-#define noinline	__attribute__((__noinline__))
+#define __inline   inline
 
 /*
  * Rather then using noinline to prevent stack consumption, use
-- 
2.17.1

[PATCH 10/12] Compiler Attributes: KENTRY used twice the "used" attribute

[Miguel Ojeda]

Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Eli Friedman <efriedma@codeaurora.org>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Joe Perches <joe@perches.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-sparse@vger.kernel.org
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
---
 include/linux/compiler.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 4030a2940d6b..17ee9165ca51 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -146,7 +146,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 	extern typeof(sym) sym;					\
 	static const unsigned long __kentry_##sym		\
 	__used							\
-	__attribute__((__section__("___kentry" "+" #sym ), used))	\
+	__attribute__((__section__("___kentry" "+" #sym )))	\
 	= (unsigned long)&sym;
 #endif
 
-- 
2.17.1

[PATCH 11/12] Compiler Attributes: remove uses of __attribute__ from compiler.h

[Miguel Ojeda]

Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Eli Friedman <efriedma@codeaurora.org>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Joe Perches <joe@perches.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-sparse@vger.kernel.org
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
---
 include/linux/compiler.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 17ee9165ca51..b5fb034fa6fa 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -23,8 +23,8 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 #define __branch_check__(x, expect, is_constant) ({			\
 			long ______r;					\
 			static struct ftrace_likely_data		\
-				__attribute__((__aligned__(4)))		\
-				__attribute__((__section__("_ftrace_annotated_branch"))) \
+				__aligned(4)				\
+				__section("_ftrace_annotated_branch")	\
 				______f = {				\
 				.data.func = __func__,			\
 				.data.file = __FILE__,			\
@@ -59,8 +59,8 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 	({								\
 		int ______r;						\
 		static struct ftrace_branch_data			\
-			__attribute__((__aligned__(4)))			\
-			__attribute__((__section__("_ftrace_branch")))	\
+			__aligned(4)					\
+			__section("_ftrace_branch")			\
 			______f = {					\
 				.func = __func__,			\
 				.file = __FILE__,			\
@@ -146,7 +146,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 	extern typeof(sym) sym;					\
 	static const unsigned long __kentry_##sym		\
 	__used							\
-	__attribute__((__section__("___kentry" "+" #sym )))	\
+	__section("___kentry" "+" #sym )			\
 	= (unsigned long)&sym;
 #endif
 
@@ -287,7 +287,7 @@ unsigned long read_word_at_a_time(const void *addr)
  * visible to the compiler.
  */
 #define __ADDRESSABLE(sym) \
-	static void * __attribute__((__section__(".discard.addressable"), used)) \
+	static void * __section(".discard.addressable") __used \
 		__PASTE(__addressable_##sym, __LINE__) = (void *)&sym;
 
 /**
-- 
2.17.1

[PATCH 12/12] Compiler Attributes: add Doc/process/programming-language.rst

[Miguel Ojeda]

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Eli Friedman <efriedma@codeaurora.org>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Joe Perches <joe@perches.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-sparse@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
---
 Documentation/process/index.rst               |  1 +
 .../process/programming-language.rst          | 44 +++++++++++++++++++
 2 files changed, 45 insertions(+)
 create mode 100644 Documentation/process/programming-language.rst

diff --git a/Documentation/process/index.rst b/Documentation/process/index.rst
index 37bd0628b6ee..c56f24a22d2a 100644
--- a/Documentation/process/index.rst
+++ b/Documentation/process/index.rst
@@ -23,6 +23,7 @@ Below are the essential guides that every developer should read.
    code-of-conflict
    development-process
    submitting-patches
+   programming-language
    coding-style
    maintainer-pgp-guide
    email-clients
diff --git a/Documentation/process/programming-language.rst b/Documentation/process/programming-language.rst
new file mode 100644
index 000000000000..674f28ae7f73
--- /dev/null
+++ b/Documentation/process/programming-language.rst
@@ -0,0 +1,44 @@
+.. _programming_language:
+
+Programming Language
+====================
+
+The kernel is written in the C programming language [c-language]_.
+More precisely, the kernel is typically compiled with ``gcc`` [gcc]_
+under ``-std=gnu89`` [gcc-c-dialect-options]_: the GNU dialect of ISO C90
+(including some C99 features).
+
+This dialect contains many extensions to the language [gnu-extensions]_,
+and many of them are used within the kernel as a matter of course.
+
+There is some support for compiling the kernel with ``clang`` [clang]_
+and ``icc`` [icc]_ for several of the architectures, although at the time
+of writing it is not completed, requiring third-party patches.
+
+Attributes
+----------
+
+One of the common extensions used throughout the kernel are attributes
+[gcc-attribute-syntax]_. Attributes allow to introduce
+implementation-defined semantics to language entities (like variables,
+functions or types) without having to make significant syntactic changes
+to the language (e.g. adding a new keyword) [n2049]_.
+
+In some cases, attributes are optional (i.e. a compiler not supporting them
+should still produce proper code, even if it is slower or does not perform
+as many compile-time checks/diagnostics).
+
+The kernel defines pseudo-keywords (e.g. ``__pure``) instead of using
+directly the GNU attribute syntax (e.g. ``__attribute__((pure))``).
+
+Please refer to ``include/linux/compiler_attributes.h`` for more information.
+
+.. [c-language] http://www.open-std.org/jtc1/sc22/wg14/www/standards
+.. [gcc] https://gcc.gnu.org
+.. [clang] https://clang.llvm.org
+.. [icc] https://software.intel.com/en-us/c-compilers
+.. [gcc-c-dialect-options] https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html
+.. [gnu-extensions] https://gcc.gnu.org/onlinedocs/gcc/C-Extensions.html
+.. [gcc-attribute-syntax] https://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html
+.. [n2049] http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2049.pdf
+
-- 
2.17.1

Re: [PATCH 10/12] Compiler Attributes: KENTRY used twice the "used" attribute

[Nick Desaulniers]

On Mon, Sep 3, 2018 at 1:34 PM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
>
> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
> Cc: Eli Friedman <efriedma@codeaurora.org>
> Cc: Christopher Li <sparse@chrisli.org>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Geert Uytterhoeven <geert@linux-m68k.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> Cc: Joe Perches <joe@perches.com>
> Cc: Dominique Martinet <asmadeus@codewreck.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: linux-sparse@vger.kernel.org
> Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
> ---
>  include/linux/compiler.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> index 4030a2940d6b..17ee9165ca51 100644
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -146,7 +146,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
>         extern typeof(sym) sym;                                 \
>         static const unsigned long __kentry_##sym               \
>         __used                                                  \
> -       __attribute__((__section__("___kentry" "+" #sym ), used))       \
> +       __attribute__((__section__("___kentry" "+" #sym )))     \
>         = (unsigned long)&sym;
>  #endif
>
> --
> 2.17.1
>

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

-- 
Thanks,
~Nick Desaulniers

Re: [PATCH 07/12] Compiler Attributes: remove unneeded sparse (__CHECKER__) tests

[Luc Van Oostenryck]

On Mon, Sep 03, 2018 at 10:33:11PM +0200, Miguel Ojeda wrote:
> Sparse knows about a few more attributes now, so we can remove
> the __CHECKER__ conditions from them (which, in turn, allow us
> to move some of them later on to compiler_attributes.h).
> 
>   * assume_aligned: since sparse's commit ffc860b ("sparse:
>     ignore __assume_aligned__ attribute"), included in 0.5.1
> 
>   * error: since sparse's commit 0a04210 ("sparse: Add 'error'
>     to ignored attributes"), included in 0.5.0
> 
>   * hotpatch: since sparse's commit 6043210 ("sparse/parse.c:
>     ignore hotpatch attribute"), included in 0.5.1
> 
>   * warning: since sparse's commit 977365d ("Avoid "attribute
>     'warning': unknown attribute" warning"), included in 0.4.2

Hi,

I hadn't noticed in the previous version but I see now that hotpatch
& assume_aligned is only available since sparse 0.5.1 which is only
13 months old. It would be great if everyone use a recent version
but I fear that a lot of people still use something less recent.
v0.5.0 should be OK, though, it's more than 5 years old.

Sorry for not having noticed this earlier.

-- Luc 

Re: [PATCH 07/12] Compiler Attributes: remove unneeded sparse (__CHECKER__) tests

[Josh Triplett]

On Wed, Sep 05, 2018 at 08:20:39PM +0200, Luc Van Oostenryck wrote:
> On Mon, Sep 03, 2018 at 10:33:11PM +0200, Miguel Ojeda wrote:
> > Sparse knows about a few more attributes now, so we can remove
> > the __CHECKER__ conditions from them (which, in turn, allow us
> > to move some of them later on to compiler_attributes.h).
> > 
> >   * assume_aligned: since sparse's commit ffc860b ("sparse:
> >     ignore __assume_aligned__ attribute"), included in 0.5.1
> > 
> >   * error: since sparse's commit 0a04210 ("sparse: Add 'error'
> >     to ignored attributes"), included in 0.5.0
> > 
> >   * hotpatch: since sparse's commit 6043210 ("sparse/parse.c:
> >     ignore hotpatch attribute"), included in 0.5.1
> > 
> >   * warning: since sparse's commit 977365d ("Avoid "attribute
> >     'warning': unknown attribute" warning"), included in 0.4.2
> 
> Hi,
> 
> I hadn't noticed in the previous version but I see now that hotpatch
> & assume_aligned is only available since sparse 0.5.1 which is only
> 13 months old. It would be great if everyone use a recent version
> but I fear that a lot of people still use something less recent.
> v0.5.0 should be OK, though, it's more than 5 years old.
> 
> Sorry for not having noticed this earlier.

Unlike GCC, I don't think it's at all unreasonable to assume a
*relatively* recent version of Sparse.

(Once we start assuming a version with __has_attribute support, this
will get even easier to handle.)

Re: [PATCH 07/12] Compiler Attributes: remove unneeded sparse (__CHECKER__) tests

[Linus Torvalds]

On Wed, Sep 5, 2018 at 12:30 PM Josh Triplett <josh@joshtriplett.org> wrote:
>
> Unlike GCC, I don't think it's at all unreasonable to assume a
> *relatively* recent version of Sparse.

Yeah, sparse is small and easy to build and installs in your own
~/bin/ directory by default.

Anybody who can build the kernel can trivially fetch and build sparse
in seconds.  It literally builds from scratch in 2.5s for me.

I don't think you even need any development packages that you don't
already need for the kernel. Just a C compiler and libc, basically.

Sure, some parts of sparse can use things like libxml and llvm and
even gtk, but that's for functionality that the "check kernel with
sparse" doesn't even need, and the makefile will automatically disable
them if you don't have it installed.

So if people are having trouble, just point them to the sparse repo,
and tell them that

    git clone ...
    cd sparse
    make -j8
    make install

fixes the issue in 30 seconds.

Although maybe I'm misstating just how easy sparse is to build and
install, and people have had problems?

                 Linus

Re: [PATCH 07/12] Compiler Attributes: remove unneeded sparse (__CHECKER__) tests

[Luc Van Oostenryck]

On Wed, Sep 05, 2018 at 12:40:26PM -0700, Linus Torvalds wrote:
> On Wed, Sep 5, 2018 at 12:30 PM Josh Triplett <josh@joshtriplett.org> wrote:
> >
> > Unlike GCC, I don't think it's at all unreasonable to assume a
> > *relatively* recent version of Sparse.
> 
> Yeah, sparse is small and easy to build and installs in your own
> ~/bin/ directory by default.
> 
> Anybody who can build the kernel can trivially fetch and build sparse
> in seconds.  It literally builds from scratch in 2.5s for me.
> 
> I don't think you even need any development packages that you don't
> already need for the kernel. Just a C compiler and libc, basically.
> 
> Sure, some parts of sparse can use things like libxml and llvm and
> even gtk, but that's for functionality that the "check kernel with
> sparse" doesn't even need, and the makefile will automatically disable
> them if you don't have it installed.
> 
> So if people are having trouble, just point them to the sparse repo,
> and tell them that
> 
>     git clone ...
>     cd sparse
>     make -j8
>     make install
> 
> fixes the issue in 30 seconds.
> 
> Although maybe I'm misstating just how easy sparse is to build and
> install, and people have had problems?
> 

I never heard of anyone having a problem to build sparse but I
guess that a lot of people just use their distro's version.

That said, I'm of course, all for encouraging people to upgrad
to a recent version.


-- Luc