--- /dev/null
+From: Arnd Bergmann <arnd@arndb.de>
+Date: Tue, 19 Jun 2018 13:14:56 -0700
+Subject: [PATCH] kbuild: add macro for controlling warnings to
+ linux/compiler.h
+
+I have occasionally run into a situation where it would make sense to
+control a compiler warning from a source file rather than doing so from
+a Makefile using the $(cc-disable-warning, ...) or $(cc-option, ...)
+helpers.
+
+The approach here is similar to what glibc uses, using __diag() and
+related macros to encapsulate a _Pragma("GCC diagnostic ...") statement
+that gets turned into the respective "#pragma GCC diagnostic ..." by
+the preprocessor when the macro gets expanded.
+
+Like glibc, I also have an argument to pass the affected compiler
+version, but decided to actually evaluate that one. For now, this
+supports GCC_4_6, GCC_4_7, GCC_4_8, GCC_4_9, GCC_5, GCC_6, GCC_7,
+GCC_8 and GCC_9. Adding support for CLANG_5 and other interesting
+versions is straightforward here. GNU compilers starting with gcc-4.2
+could support it in principle, but "#pragma GCC diagnostic push"
+was only added in gcc-4.6, so it seems simpler to not deal with those
+at all. The same versions show a large number of warnings already,
+so it seems easier to just leave it at that and not do a more
+fine-grained control for them.
+
+The use cases I found so far include:
+
+- turning off the gcc-8 -Wattribute-alias warning inside of the
+ SYSCALL_DEFINEx() macro without having to do it globally.
+
+- Reducing the build time for a simple re-make after a change,
+ once we move the warnings from ./Makefile and
+ ./scripts/Makefile.extrawarn into linux/compiler.h
+
+- More control over the warnings based on other configurations,
+ using preprocessor syntax instead of Makefile syntax. This should make
+ it easier for the average developer to understand and change things.
+
+- Adding an easy way to turn the W=1 option on unconditionally
+ for a subdirectory or a specific file. This has been requested
+ by several developers in the past that want to have their subsystems
+ W=1 clean.
+
+- Integrating clang better into the build systems. Clang supports
+ more warnings than GCC, and we probably want to classify them
+ as default, W=1, W=2 etc, but there are cases in which the
+ warnings should be classified differently due to excessive false
+ positives from one or the other compiler.
+
+- Adding a way to turn the default warnings into errors (e.g. using
+ a new "make E=0" tag) while not also turning the W=1 warnings into
+ errors.
+
+This patch for now just adds the minimal infrastructure in order to
+do the first of the list above. As the #pragma GCC diagnostic
+takes precedence over command line options, the next step would be
+to convert a lot of the individual Makefiles that set nonstandard
+options to use __diag() instead.
+
+[paul.burton@mips.com:
+ - Rebase atop current master.
+ - Add __diag_GCC, or more generally __diag_<compiler>, abstraction to
+ avoid code outside of linux/compiler-gcc.h needing to duplicate
+ knowledge about different GCC versions.
+ - Add a comment argument to __diag_{ignore,warn,error} which isn't
+ used in the expansion of the macros but serves to push people to
+ document the reason for using them - per feedback from Kees Cook.
+ - Translate severity to GCC-specific pragmas in linux/compiler-gcc.h
+ rather than using GCC-specific in linux/compiler_types.h.
+ - Drop all but GCC 8 macros, since we only need to define macros for
+ versions that we need to introduce pragmas for, and as of this
+ series that's just GCC 8.
+ - Capitalize comments in linux/compiler-gcc.h to match the style of
+ the rest of the file.
+ - Line up macro definitions with tabs in linux/compiler-gcc.h.]
+
+Signed-off-by: Arnd Bergmann <arnd@arndb.de>
+Signed-off-by: Paul Burton <paul.burton@mips.com>
+Tested-by: Christophe Leroy <christophe.leroy@c-s.fr>
+Tested-by: Stafford Horne <shorne@gmail.com>
+Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
+---
+
+--- a/include/linux/compiler-gcc.h
++++ b/include/linux/compiler-gcc.h
+@@ -343,3 +343,28 @@
+ * code
+ */
+ #define uninitialized_var(x) x = x
++
++/*
++ * Turn individual warnings and errors on and off locally, depending
++ * on version.
++ */
++#define __diag_GCC(version, severity, s) \
++ __diag_GCC_ ## version(__diag_GCC_ ## severity s)
++
++/* Severity used in pragma directives */
++#define __diag_GCC_ignore ignored
++#define __diag_GCC_warn warning
++#define __diag_GCC_error error
++
++/* Compilers before gcc-4.6 do not understand "#pragma GCC diagnostic push" */
++#if GCC_VERSION >= 40600
++#define __diag_str1(s) #s
++#define __diag_str(s) __diag_str1(s)
++#define __diag(s) _Pragma(__diag_str(GCC diagnostic s))
++#endif
++
++#if GCC_VERSION >= 80000
++#define __diag_GCC_8(s) __diag(s)
++#else
++#define __diag_GCC_8(s)
++#endif
+--- a/include/linux/compiler_types.h
++++ b/include/linux/compiler_types.h
+@@ -271,4 +271,22 @@ struct ftrace_likely_data {
+ # define __native_word(t) (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
+ #endif
+
++#ifndef __diag
++#define __diag(string)
++#endif
++
++#ifndef __diag_GCC
++#define __diag_GCC(version, severity, string)
++#endif
++
++#define __diag_push() __diag(push)
++#define __diag_pop() __diag(pop)
++
++#define __diag_ignore(compiler, version, option, comment) \
++ __diag_ ## compiler(version, ignore, option)
++#define __diag_warn(compiler, version, option, comment) \
++ __diag_ ## compiler(version, warn, option)
++#define __diag_error(compiler, version, option, comment) \
++ __diag_ ## compiler(version, error, option)
++
+ #endif /* __LINUX_COMPILER_TYPES_H */
--- /dev/null
+From: Arnd Bergmann <arnd@arndb.de>
+Date: Tue, 19 Jun 2018 13:14:57 -0700
+Subject: [PATCH] disable -Wattribute-alias warning for SYSCALL_DEFINEx()
+
+gcc-8 warns for every single definition of a system call entry
+point, e.g.:
+
+include/linux/compat.h:56:18: error: 'compat_sys_rt_sigprocmask' alias between functions of incompatible types 'long int(int, compat_sigset_t *, compat_sigset_t *, compat_size_t)' {aka 'long int(int, struct <anonymous> *, struct <anonymous> *, unsigned int)'} and 'long int(long int, long int, long int, long int)' [-Werror=attribute-alias]
+ asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))\
+ ^~~~~~~~~~
+include/linux/compat.h:45:2: note: in expansion of macro 'COMPAT_SYSCALL_DEFINEx'
+ COMPAT_SYSCALL_DEFINEx(4, _##name, __VA_ARGS__)
+ ^~~~~~~~~~~~~~~~~~~~~~
+kernel/signal.c:2601:1: note: in expansion of macro 'COMPAT_SYSCALL_DEFINE4'
+ COMPAT_SYSCALL_DEFINE4(rt_sigprocmask, int, how, compat_sigset_t __user *, nset,
+ ^~~~~~~~~~~~~~~~~~~~~~
+include/linux/compat.h:60:18: note: aliased declaration here
+ asmlinkage long compat_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__))\
+ ^~~~~~~~~~
+
+The new warning seems reasonable in principle, but it doesn't
+help us here, since we rely on the type mismatch to sanitize the
+system call arguments. After I reported this as GCC PR82435, a new
+-Wno-attribute-alias option was added that could be used to turn the
+warning off globally on the command line, but I'd prefer to do it a
+little more fine-grained.
+
+Interestingly, turning a warning off and on again inside of
+a single macro doesn't always work, in this case I had to add
+an extra statement inbetween and decided to copy the __SC_TEST
+one from the native syscall to the compat syscall macro. See
+https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83256 for more details
+about this.
+
+[paul.burton@mips.com:
+ - Rebase atop current master.
+ - Split GCC & version arguments to __diag_ignore() in order to match
+ changes to the preceding patch.
+ - Add the comment argument to match the preceding patch.]
+
+Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82435
+Signed-off-by: Arnd Bergmann <arnd@arndb.de>
+Signed-off-by: Paul Burton <paul.burton@mips.com>
+Tested-by: Christophe Leroy <christophe.leroy@c-s.fr>
+Tested-by: Stafford Horne <shorne@gmail.com>
+Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
+---
+
+--- a/include/linux/compat.h
++++ b/include/linux/compat.h
+@@ -48,6 +48,9 @@
+ COMPAT_SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)
+
+ #define COMPAT_SYSCALL_DEFINEx(x, name, ...) \
++ __diag_push(); \
++ __diag_ignore(GCC, 8, "-Wattribute-alias", \
++ "Type aliasing is used to sanitize syscall arguments");\
+ asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))\
+ __attribute__((alias(__stringify(compat_SyS##name)))); \
+ static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
+@@ -56,6 +59,7 @@
+ { \
+ return C_SYSC##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__)); \
+ } \
++ __diag_pop(); \
+ static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+
+ #ifndef compat_user_stack_pointer
+--- a/include/linux/syscalls.h
++++ b/include/linux/syscalls.h
+@@ -208,6 +208,9 @@ static inline int is_syscall_trace_event
+
+ #define __PROTECT(...) asmlinkage_protect(__VA_ARGS__)
+ #define __SYSCALL_DEFINEx(x, name, ...) \
++ __diag_push(); \
++ __diag_ignore(GCC, 8, "-Wattribute-alias", \
++ "Type aliasing is used to sanitize syscall arguments");\
+ asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
+ __attribute__((alias(__stringify(SyS##name)))); \
+ static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__)); \
+@@ -219,6 +222,7 @@ static inline int is_syscall_trace_event
+ __PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \
+ return ret; \
+ } \
++ __diag_pop(); \
+ static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+
+ /*
--- /dev/null
+From: Arnd Bergmann <arnd@arndb.de>
+Date: Tue, 19 Jun 2018 13:14:56 -0700
+Subject: [PATCH] kbuild: add macro for controlling warnings to
+ linux/compiler.h
+
+I have occasionally run into a situation where it would make sense to
+control a compiler warning from a source file rather than doing so from
+a Makefile using the $(cc-disable-warning, ...) or $(cc-option, ...)
+helpers.
+
+The approach here is similar to what glibc uses, using __diag() and
+related macros to encapsulate a _Pragma("GCC diagnostic ...") statement
+that gets turned into the respective "#pragma GCC diagnostic ..." by
+the preprocessor when the macro gets expanded.
+
+Like glibc, I also have an argument to pass the affected compiler
+version, but decided to actually evaluate that one. For now, this
+supports GCC_4_6, GCC_4_7, GCC_4_8, GCC_4_9, GCC_5, GCC_6, GCC_7,
+GCC_8 and GCC_9. Adding support for CLANG_5 and other interesting
+versions is straightforward here. GNU compilers starting with gcc-4.2
+could support it in principle, but "#pragma GCC diagnostic push"
+was only added in gcc-4.6, so it seems simpler to not deal with those
+at all. The same versions show a large number of warnings already,
+so it seems easier to just leave it at that and not do a more
+fine-grained control for them.
+
+The use cases I found so far include:
+
+- turning off the gcc-8 -Wattribute-alias warning inside of the
+ SYSCALL_DEFINEx() macro without having to do it globally.
+
+- Reducing the build time for a simple re-make after a change,
+ once we move the warnings from ./Makefile and
+ ./scripts/Makefile.extrawarn into linux/compiler.h
+
+- More control over the warnings based on other configurations,
+ using preprocessor syntax instead of Makefile syntax. This should make
+ it easier for the average developer to understand and change things.
+
+- Adding an easy way to turn the W=1 option on unconditionally
+ for a subdirectory or a specific file. This has been requested
+ by several developers in the past that want to have their subsystems
+ W=1 clean.
+
+- Integrating clang better into the build systems. Clang supports
+ more warnings than GCC, and we probably want to classify them
+ as default, W=1, W=2 etc, but there are cases in which the
+ warnings should be classified differently due to excessive false
+ positives from one or the other compiler.
+
+- Adding a way to turn the default warnings into errors (e.g. using
+ a new "make E=0" tag) while not also turning the W=1 warnings into
+ errors.
+
+This patch for now just adds the minimal infrastructure in order to
+do the first of the list above. As the #pragma GCC diagnostic
+takes precedence over command line options, the next step would be
+to convert a lot of the individual Makefiles that set nonstandard
+options to use __diag() instead.
+
+[paul.burton@mips.com:
+ - Rebase atop current master.
+ - Add __diag_GCC, or more generally __diag_<compiler>, abstraction to
+ avoid code outside of linux/compiler-gcc.h needing to duplicate
+ knowledge about different GCC versions.
+ - Add a comment argument to __diag_{ignore,warn,error} which isn't
+ used in the expansion of the macros but serves to push people to
+ document the reason for using them - per feedback from Kees Cook.
+ - Translate severity to GCC-specific pragmas in linux/compiler-gcc.h
+ rather than using GCC-specific in linux/compiler_types.h.
+ - Drop all but GCC 8 macros, since we only need to define macros for
+ versions that we need to introduce pragmas for, and as of this
+ series that's just GCC 8.
+ - Capitalize comments in linux/compiler-gcc.h to match the style of
+ the rest of the file.
+ - Line up macro definitions with tabs in linux/compiler-gcc.h.]
+
+Signed-off-by: Arnd Bergmann <arnd@arndb.de>
+Signed-off-by: Paul Burton <paul.burton@mips.com>
+Tested-by: Christophe Leroy <christophe.leroy@c-s.fr>
+Tested-by: Stafford Horne <shorne@gmail.com>
+Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
+---
+
+--- a/include/linux/compiler-gcc.h
++++ b/include/linux/compiler-gcc.h
+@@ -315,3 +315,28 @@
+ * code
+ */
+ #define uninitialized_var(x) x = x
++
++/*
++ * Turn individual warnings and errors on and off locally, depending
++ * on version.
++ */
++#define __diag_GCC(version, severity, s) \
++ __diag_GCC_ ## version(__diag_GCC_ ## severity s)
++
++/* Severity used in pragma directives */
++#define __diag_GCC_ignore ignored
++#define __diag_GCC_warn warning
++#define __diag_GCC_error error
++
++/* Compilers before gcc-4.6 do not understand "#pragma GCC diagnostic push" */
++#if GCC_VERSION >= 40600
++#define __diag_str1(s) #s
++#define __diag_str(s) __diag_str1(s)
++#define __diag(s) _Pragma(__diag_str(GCC diagnostic s))
++#endif
++
++#if GCC_VERSION >= 80000
++#define __diag_GCC_8(s) __diag(s)
++#else
++#define __diag_GCC_8(s)
++#endif
+--- a/include/linux/compiler.h
++++ b/include/linux/compiler.h
+@@ -578,4 +578,23 @@ static __always_inline void __write_once
+ # define __kprobes
+ # define nokprobe_inline inline
+ #endif
++
++#ifndef __diag
++#define __diag(string)
++#endif
++
++#ifndef __diag_GCC
++#define __diag_GCC(version, severity, string)
++#endif
++
++#define __diag_push() __diag(push)
++#define __diag_pop() __diag(pop)
++
++#define __diag_ignore(compiler, version, option, comment) \
++ __diag_ ## compiler(version, ignore, option)
++#define __diag_warn(compiler, version, option, comment) \
++ __diag_ ## compiler(version, warn, option)
++#define __diag_error(compiler, version, option, comment) \
++ __diag_ ## compiler(version, error, option)
++
+ #endif /* __LINUX_COMPILER_H */
--- /dev/null
+From: Arnd Bergmann <arnd@arndb.de>
+Date: Tue, 19 Jun 2018 13:14:57 -0700
+Subject: [PATCH] disable -Wattribute-alias warning for SYSCALL_DEFINEx()
+
+gcc-8 warns for every single definition of a system call entry
+point, e.g.:
+
+include/linux/compat.h:56:18: error: 'compat_sys_rt_sigprocmask' alias between functions of incompatible types 'long int(int, compat_sigset_t *, compat_sigset_t *, compat_size_t)' {aka 'long int(int, struct <anonymous> *, struct <anonymous> *, unsigned int)'} and 'long int(long int, long int, long int, long int)' [-Werror=attribute-alias]
+ asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))\
+ ^~~~~~~~~~
+include/linux/compat.h:45:2: note: in expansion of macro 'COMPAT_SYSCALL_DEFINEx'
+ COMPAT_SYSCALL_DEFINEx(4, _##name, __VA_ARGS__)
+ ^~~~~~~~~~~~~~~~~~~~~~
+kernel/signal.c:2601:1: note: in expansion of macro 'COMPAT_SYSCALL_DEFINE4'
+ COMPAT_SYSCALL_DEFINE4(rt_sigprocmask, int, how, compat_sigset_t __user *, nset,
+ ^~~~~~~~~~~~~~~~~~~~~~
+include/linux/compat.h:60:18: note: aliased declaration here
+ asmlinkage long compat_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__))\
+ ^~~~~~~~~~
+
+The new warning seems reasonable in principle, but it doesn't
+help us here, since we rely on the type mismatch to sanitize the
+system call arguments. After I reported this as GCC PR82435, a new
+-Wno-attribute-alias option was added that could be used to turn the
+warning off globally on the command line, but I'd prefer to do it a
+little more fine-grained.
+
+Interestingly, turning a warning off and on again inside of
+a single macro doesn't always work, in this case I had to add
+an extra statement inbetween and decided to copy the __SC_TEST
+one from the native syscall to the compat syscall macro. See
+https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83256 for more details
+about this.
+
+[paul.burton@mips.com:
+ - Rebase atop current master.
+ - Split GCC & version arguments to __diag_ignore() in order to match
+ changes to the preceding patch.
+ - Add the comment argument to match the preceding patch.]
+
+Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82435
+Signed-off-by: Arnd Bergmann <arnd@arndb.de>
+Signed-off-by: Paul Burton <paul.burton@mips.com>
+Tested-by: Christophe Leroy <christophe.leroy@c-s.fr>
+Tested-by: Stafford Horne <shorne@gmail.com>
+Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
+---
+
+--- a/include/linux/compat.h
++++ b/include/linux/compat.h
+@@ -47,6 +47,9 @@
+ COMPAT_SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)
+
+ #define COMPAT_SYSCALL_DEFINEx(x, name, ...) \
++ __diag_push(); \
++ __diag_ignore(GCC, 8, "-Wattribute-alias", \
++ "Type aliasing is used to sanitize syscall arguments");\
+ asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))\
+ __attribute__((alias(__stringify(compat_SyS##name)))); \
+ static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
+@@ -55,6 +58,7 @@
+ { \
+ return C_SYSC##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__)); \
+ } \
++ __diag_pop(); \
+ static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+
+ #ifndef compat_user_stack_pointer
+--- a/include/linux/syscalls.h
++++ b/include/linux/syscalls.h
+@@ -192,6 +192,9 @@ extern struct trace_event_functions exit
+
+ #define __PROTECT(...) asmlinkage_protect(__VA_ARGS__)
+ #define __SYSCALL_DEFINEx(x, name, ...) \
++ __diag_push(); \
++ __diag_ignore(GCC, 8, "-Wattribute-alias", \
++ "Type aliasing is used to sanitize syscall arguments");\
+ asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
+ __attribute__((alias(__stringify(SyS##name)))); \
+ static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__)); \
+@@ -203,6 +206,7 @@ extern struct trace_event_functions exit
+ __PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \
+ return ret; \
+ } \
++ __diag_pop(); \
+ static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+
+ asmlinkage long sys32_quotactl(unsigned int cmd, const char __user *special,
projects / openwrt / openwrt.git / commitdiff