build: include our own copy of if.h and dependencies

Import our a copy of Linux if.h and its dependencies
(compiler_types.h and libc-compat.h) from the above links. In "if.h",
"#include <linux/compiler.h>" has been replaced by
"#include <linux/compiler_types.h>". libc-compat.h is needed to avoid
conflicts with glibc.

Include "linux/if.h" in "zebra.h" when compiling on Linux. De-reference
"net/if.h" in C files.

Note that "net/if.h" is still needed. It is even included in many Linux
kernel files. "linux/if.h" provides additional definitions.

Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/include/uapi/linux/if.h?h=v5.5
Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/include/uapi/linux/libc-compat.h?h=v5.5
Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/include/linux/compiler_types.h?h=v5.5
Link: https://patchwork.ozlabs.org/project/glibc/patch/1461512707-23058-1-git-send-email-mikko.rapeli@iki.fi/
Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>

include/linux/compiler_types.h

@@ -0,0 +1,246 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_COMPILER_TYPES_H
+#define __LINUX_COMPILER_TYPES_H
+
+#ifndef __ASSEMBLY__
+
+#ifdef __CHECKER__
+# define __user		__attribute__((noderef, address_space(1)))
+# define __kernel	__attribute__((address_space(0)))
+# define __safe		__attribute__((safe))
+# define __force	__attribute__((force))
+# define __nocast	__attribute__((nocast))
+# define __iomem	__attribute__((noderef, address_space(2)))
+# define __must_hold(x)	__attribute__((context(x,1,1)))
+# define __acquires(x)	__attribute__((context(x,0,1)))
+# define __releases(x)	__attribute__((context(x,1,0)))
+# define __acquire(x)	__context__(x,1)
+# define __release(x)	__context__(x,-1)
+# define __cond_lock(x,c)	((c) ? ({ __acquire(x); 1; }) : 0)
+# define __percpu	__attribute__((noderef, address_space(3)))
+# define __rcu		__attribute__((noderef, address_space(4)))
+# define __private	__attribute__((noderef))
+extern void __chk_user_ptr(const volatile void __user *);
+extern void __chk_io_ptr(const volatile void __iomem *);
+# define ACCESS_PRIVATE(p, member) (*((typeof((p)->member) __force *) &(p)->member))
+#else /* __CHECKER__ */
+# ifdef STRUCTLEAK_PLUGIN
+#  define __user __attribute__((user))
+# else
+#  define __user
+# endif
+# define __kernel
+# define __safe
+# define __force
+# define __nocast
+# define __iomem
+# define __chk_user_ptr(x) (void)0
+# define __chk_io_ptr(x) (void)0
+# define __builtin_warning(x, y...) (1)
+# define __must_hold(x)
+# define __acquires(x)
+# define __releases(x)
+# define __acquire(x) (void)0
+# define __release(x) (void)0
+# define __cond_lock(x,c) (c)
+# define __percpu
+# define __rcu
+# define __private
+# define ACCESS_PRIVATE(p, member) ((p)->member)
+#endif /* __CHECKER__ */
+
+/* Indirect macros required for expanded argument pasting, eg. __LINE__. */
+#define ___PASTE(a,b) a##b
+#define __PASTE(a,b) ___PASTE(a,b)
+
+#ifdef __KERNEL__
+
+/* Attributes */
+#include <linux/compiler_attributes.h>
+
+/* Compiler specific macros. */
+#ifdef __clang__
+#include <linux/compiler-clang.h>
+#elif defined(__INTEL_COMPILER)
+#include <linux/compiler-intel.h>
+#elif defined(__GNUC__)
+/* The above compilers also define __GNUC__, so order is important here. */
+#include <linux/compiler-gcc.h>
+#else
+#error "Unknown compiler"
+#endif
+
+/*
+ * Some architectures need to provide custom definitions of macros provided
+ * by linux/compiler-*.h, and can do so using asm/compiler.h. We include that
+ * conditionally rather than using an asm-generic wrapper in order to avoid
+ * build failures if any C compilation, which will include this file via an
+ * -include argument in c_flags, occurs prior to the asm-generic wrappers being
+ * generated.
+ */
+#ifdef CONFIG_HAVE_ARCH_COMPILER_H
+#include <asm/compiler.h>
+#endif
+
+struct ftrace_branch_data {
+	const char *func;
+	const char *file;
+	unsigned line;
+	union {
+		struct {
+			unsigned long correct;
+			unsigned long incorrect;
+		};
+		struct {
+			unsigned long miss;
+			unsigned long hit;
+		};
+		unsigned long miss_hit[2];
+	};
+};
+
+struct ftrace_likely_data {
+	struct ftrace_branch_data	data;
+	unsigned long			constant;
+};
+
+#ifdef CONFIG_ENABLE_MUST_CHECK
+#define __must_check		__attribute__((__warn_unused_result__))
+#else
+#define __must_check
+#endif
+
+#if defined(CC_USING_HOTPATCH)
+#define notrace			__attribute__((hotpatch(0, 0)))
+#elif defined(CC_USING_PATCHABLE_FUNCTION_ENTRY)
+#define notrace			__attribute__((patchable_function_entry(0, 0)))
+#else
+#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)
+
+/*
+ * Force always-inline if the user requests it so via the .config.
+ * Prefer gnu_inline, so that extern inline functions do not emit an
+ * externally visible function. This makes extern inline behave as per gnu89
+ * semantics rather than c99. This prevents multiple symbol definition errors
+ * of extern inline functions at link time.
+ * A lot of inline functions can cause havoc with function tracing.
+ * Do not use __always_inline here, since currently it expands to inline again
+ * (which would break users of __always_inline).
+ */
+#if !defined(CONFIG_OPTIMIZE_INLINING)
+#define inline inline __attribute__((__always_inline__)) __gnu_inline \
+	__inline_maybe_unused notrace
+#else
+#define inline inline                                    __gnu_inline \
+	__inline_maybe_unused notrace
+#endif
+
+/*
+ * gcc provides both __inline__ and __inline as alternate spellings of
+ * the inline keyword, though the latter is undocumented. New kernel
+ * code should only use the inline spelling, but some existing code
+ * uses __inline__. Since we #define inline above, to ensure
+ * __inline__ has the same semantics, we need this #define.
+ *
+ * However, the spelling __inline is strictly reserved for referring
+ * to the bare keyword.
+ */
+#define __inline__ inline
+
+/*
+ * GCC does not warn about unused static inline functions for -Wunused-function.
+ * Suppress the warning in clang as well by using __maybe_unused, but enable it
+ * for W=1 build. This will allow clang to find unused functions. Remove the
+ * __inline_maybe_unused entirely after fixing most of -Wunused-function warnings.
+ */
+#ifdef KBUILD_EXTRA_WARN1
+#define __inline_maybe_unused
+#else
+#define __inline_maybe_unused __maybe_unused
+#endif
+
+/*
+ * Rather then using noinline to prevent stack consumption, use
+ * noinline_for_stack instead.  For documentation reasons.
+ */
+#define noinline_for_stack noinline
+
+#endif /* __KERNEL__ */
+
+#endif /* __ASSEMBLY__ */
+
+/*
+ * The below symbols may be defined for one or more, but not ALL, of the above
+ * 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 __latent_entropy
+# define __latent_entropy
+#endif
+
+#ifndef __randomize_layout
+# define __randomize_layout __designated_init
+#endif
+
+#ifndef __no_randomize_layout
+# define __no_randomize_layout
+#endif
+
+#ifndef randomized_struct_fields_start
+# define randomized_struct_fields_start
+# define randomized_struct_fields_end
+#endif
+
+#ifndef asm_volatile_goto
+#define asm_volatile_goto(x...) asm goto(x)
+#endif
+
+#ifdef CONFIG_CC_HAS_ASM_INLINE
+#define asm_inline asm __inline
+#else
+#define asm_inline asm
+#endif
+
+#ifndef __no_fgcse
+# define __no_fgcse
+#endif
+
+/* Are two types/vars the same type (ignoring qualifiers)? */
+#define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
+
+/* Is this type a native word size -- useful for atomic operations */
+#define __native_word(t) \
+	(sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || \
+	 sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
+
+/* Helpers for emitting diagnostics in pragmas. */
+#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 */