OpenWrt – Rev 1
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From 9b2c282b348dfe966bbba967dc7a45ce817cce50 Mon Sep 17 00:00:00 2001
From: Tom Rini <trini@konsulko.com>
Date: Mon, 29 Feb 2016 11:34:15 -0500
Subject: [PATCH] compiler*.h: sync include/linux/compiler*.h with Linux
4.5-rc6
Copy these from Linux v4.5-rc6 tag.
This is needed so that we can keep up with newer gcc versions. Note
that we don't have the uapi/ hierarchy from the kernel so continue to
use <linux/types.h>
Signed-off-by: Tom Rini <trini@konsulko.com>
---
include/linux/compiler-gcc.h | 266 ++++++++++++++++++++++++++++++++++------
include/linux/compiler-gcc3.h | 21 ----
include/linux/compiler-gcc4.h | 63 ----------
include/linux/compiler-intel.h | 45 +++++++
include/linux/compiler.h | 270 +++++++++++++++++++++++++++++++++++++++--
5 files changed, 534 insertions(+), 131 deletions(-)
delete mode 100644 include/linux/compiler-gcc3.h
delete mode 100644 include/linux/compiler-gcc4.h
create mode 100644 include/linux/compiler-intel.h
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 9896e54..22ab246 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -5,11 +5,28 @@
/*
* Common definitions for all gcc versions go here.
*/
-
+#define GCC_VERSION (__GNUC__ * 10000 \
+ + __GNUC_MINOR__ * 100 \
+ + __GNUC_PATCHLEVEL__)
/* Optimization barrier */
+
/* The "volatile" is due to gcc bugs */
#define barrier() __asm__ __volatile__("": : :"memory")
+/*
+ * This version is i.e. to prevent dead stores elimination on @ptr
+ * where gcc and llvm may behave differently when otherwise using
+ * normal barrier(): while gcc behavior gets along with a normal
+ * barrier(), llvm needs an explicit input variable to be assumed
+ * clobbered. The issue is as follows: while the inline asm might
+ * access any memory it wants, the compiler could have fit all of
+ * @ptr into memory registers instead, and since @ptr never escaped
+ * from that, it proofed that the inline asm wasn't touching any of
+ * it. This version works well with both compilers, i.e. we're telling
+ * the compiler that the inline asm absolutely may see the contents
+ * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495
+ */
+#define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
/*
* This macro obfuscates arithmetic on a variable address so that gcc
@@ -29,41 +46,63 @@
* the inline assembly constraint from =g to =r, in this particular
* case either is valid.
*/
-#define RELOC_HIDE(ptr, off) \
- ({ unsigned long __ptr; \
- __asm__ ("" : "=r"(__ptr) : "0"(ptr)); \
- (typeof(ptr)) (__ptr + (off)); })
+#define RELOC_HIDE(ptr, off) \
+({ \
+ unsigned long __ptr; \
+ __asm__ ("" : "=r"(__ptr) : "0"(ptr)); \
+ (typeof(ptr)) (__ptr + (off)); \
+})
+
+/* Make the optimizer believe the variable can be manipulated arbitrarily. */
+#define OPTIMIZER_HIDE_VAR(var) \
+ __asm__ ("" : "=r" (var) : "0" (var))
+#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(__builtin_types_compatible_p(typeof(a), typeof(&a[0])))
+#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
+#endif
/*
* Force always-inline if the user requests it so via the .config,
* or if gcc is too old:
*/
-#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
+#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
!defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
-# define inline inline __attribute__((always_inline))
-# define __inline__ __inline__ __attribute__((always_inline))
-# define __inline __inline __attribute__((always_inline))
+#define inline inline __attribute__((always_inline)) notrace
+#define __inline__ __inline__ __attribute__((always_inline)) notrace
+#define __inline __inline __attribute__((always_inline)) notrace
+#else
+/* A lot of inline functions can cause havoc with function tracing */
+#define inline inline notrace
+#define __inline__ __inline__ notrace
+#define __inline __inline notrace
#endif
-#define __deprecated __attribute__((deprecated))
-#ifndef __packed
-# define __packed __attribute__((packed))
-#endif
-#define __weak __attribute__((weak))
+#define __always_inline inline __attribute__((always_inline))
+#define noinline __attribute__((noinline))
+
+#define __deprecated __attribute__((deprecated))
+#define __packed __attribute__((packed))
+#define __weak __attribute__((weak))
+#define __alias(symbol) __attribute__((alias(#symbol)))
/*
- * 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.
+ * 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.
+ *
+ * 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)) notrace
+#define __naked __attribute__((naked)) noinline __noclone notrace
-#define __noreturn __attribute__((noreturn))
+#define __noreturn __attribute__((noreturn))
/*
* From the GCC manual:
@@ -75,19 +114,170 @@
* would be.
* [...]
*/
-#ifndef __pure
-# define __pure __attribute__((pure))
-#endif
-#ifndef __aligned
-# define __aligned(x) __attribute__((aligned(x)))
-#endif
-#define __printf(a,b) __attribute__((format(printf,a,b)))
-#define noinline __attribute__((noinline))
-#define __attribute_const__ __attribute__((__const__))
-#define __maybe_unused __attribute__((unused))
-#define __always_unused __attribute__((unused))
-
-#define __gcc_header(x) #x
-#define _gcc_header(x) __gcc_header(linux/compiler-gcc##x.h)
-#define gcc_header(x) _gcc_header(x)
-#include gcc_header(__GNUC__)
+#define __pure __attribute__((pure))
+#define __aligned(x) __attribute__((aligned(x)))
+#define __printf(a, b) __attribute__((format(printf, a, b)))
+#define __scanf(a, b) __attribute__((format(scanf, a, b)))
+#define __attribute_const__ __attribute__((__const__))
+#define __maybe_unused __attribute__((unused))
+#define __always_unused __attribute__((unused))
+
+/* gcc version specific checks */
+
+#if GCC_VERSION < 30200
+# error Sorry, your compiler is too old - please upgrade it.
+#endif
+
+#if GCC_VERSION < 30300
+# define __used __attribute__((__unused__))
+#else
+# define __used __attribute__((__used__))
+#endif
+
+#ifdef CONFIG_GCOV_KERNEL
+# if GCC_VERSION < 30400
+# error "GCOV profiling support for gcc versions below 3.4 not included"
+# endif /* __GNUC_MINOR__ */
+#endif /* CONFIG_GCOV_KERNEL */
+
+#if GCC_VERSION >= 30400
+#define __must_check __attribute__((warn_unused_result))
+#endif
+
+#if GCC_VERSION >= 40000
+
+/* GCC 4.1.[01] miscompiles __weak */
+#ifdef __KERNEL__
+# if GCC_VERSION >= 40100 && GCC_VERSION <= 40101
+# error Your version of gcc miscompiles the __weak directive
+# endif
+#endif
+
+#define __used __attribute__((__used__))
+#define __compiler_offsetof(a, b) \
+ __builtin_offsetof(a, b)
+
+#if GCC_VERSION >= 40100 && GCC_VERSION < 40600
+# define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
+#endif
+
+#if GCC_VERSION >= 40300
+/* Mark functions as cold. gcc will assume any path leading to a call
+ * to them will be unlikely. This means a lot of manual unlikely()s
+ * are unnecessary now for any paths leading to the usual suspects
+ * like BUG(), printk(), panic() etc. [but let's keep them for now for
+ * older compilers]
+ *
+ * Early snapshots of gcc 4.3 don't support this and we can't detect this
+ * in the preprocessor, but we can live with this because they're unreleased.
+ * Maketime probing would be overkill here.
+ *
+ * gcc also has a __attribute__((__hot__)) to move hot functions into
+ * a special section, but I don't see any sense in this right now in
+ * the kernel context
+ */
+#define __cold __attribute__((__cold__))
+
+#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
+
+#ifndef __CHECKER__
+# define __compiletime_warning(message) __attribute__((warning(message)))
+# define __compiletime_error(message) __attribute__((error(message)))
+#endif /* __CHECKER__ */
+#endif /* GCC_VERSION >= 40300 */
+
+#if GCC_VERSION >= 40500
+/*
+ * Mark a position in code as unreachable. This can be used to
+ * suppress control flow warnings after asm blocks that transfer
+ * control elsewhere.
+ *
+ * Early snapshots of gcc 4.5 don't support this and we can't detect
+ * this in the preprocessor, but we can live with this because they're
+ * unreleased. Really, we need to have autoconf for the kernel.
+ */
+#define unreachable() __builtin_unreachable()
+
+/* Mark a function definition as prohibited from being cloned. */
+#define __noclone __attribute__((__noclone__))
+
+#endif /* GCC_VERSION >= 40500 */
+
+#if GCC_VERSION >= 40600
+/*
+ * 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))
+#endif
+
+
+#if GCC_VERSION >= 40900 && !defined(__CHECKER__)
+/*
+ * __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:
+ *
+ * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
+ *
+ * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
+ *
+ * (asm goto is automatically volatile - the naming reflects this.)
+ */
+#define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
+
+#ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP
+#if GCC_VERSION >= 40400
+#define __HAVE_BUILTIN_BSWAP32__
+#define __HAVE_BUILTIN_BSWAP64__
+#endif
+#if GCC_VERSION >= 40800 || (defined(__powerpc__) && GCC_VERSION >= 40600)
+#define __HAVE_BUILTIN_BSWAP16__
+#endif
+#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */
+
+#if GCC_VERSION >= 50000
+#define KASAN_ABI_VERSION 4
+#elif GCC_VERSION >= 40902
+#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
+
+#endif /* gcc version >= 40000 specific checks */
+
+#if !defined(__noclone)
+#define __noclone /* not needed */
+#endif
+
+#if !defined(__no_sanitize_address)
+#define __no_sanitize_address
+#endif
+
+/*
+ * A trick to suppress uninitialized variable warning without generating any
+ * code
+ */
+#define uninitialized_var(x) x = x
diff --git a/include/linux/compiler-gcc3.h b/include/linux/compiler-gcc3.h
deleted file mode 100644
index 2befe65..0000000
--- a/include/linux/compiler-gcc3.h
+++ /dev/null
@@ -1,21 +0,0 @@
-#ifndef __LINUX_COMPILER_H
-#error "Please don't include <linux/compiler-gcc3.h> directly, include <linux/compiler.h> instead."
-#endif
-
-#if __GNUC_MINOR__ >= 3
-# define __used __attribute__((__used__))
-#else
-# define __used __attribute__((__unused__))
-#endif
-
-#if __GNUC_MINOR__ >= 4
-#define __must_check __attribute__((warn_unused_result))
-#endif
-
-/*
- * A trick to suppress uninitialized variable warning without generating any
- * code
- */
-#define uninitialized_var(x) x = x
-
-#define __always_inline inline __attribute__((always_inline))
diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h
deleted file mode 100644
index 27d11ca..0000000
--- a/include/linux/compiler-gcc4.h
+++ /dev/null
@@ -1,63 +0,0 @@
-#ifndef __LINUX_COMPILER_H
-#error "Please don't include <linux/compiler-gcc4.h> directly, include <linux/compiler.h> instead."
-#endif
-
-/* GCC 4.1.[01] miscompiles __weak */
-#ifdef __KERNEL__
-# if __GNUC_MINOR__ == 1 && __GNUC_PATCHLEVEL__ <= 1
-# error Your version of gcc miscompiles the __weak directive
-# endif
-#endif
-
-#define __used __attribute__((__used__))
-#define __must_check __attribute__((warn_unused_result))
-#define __compiler_offsetof(a,b) __builtin_offsetof(a,b)
-#ifndef __always_inline
-# define __always_inline inline __attribute__((always_inline))
-#endif
-
-/*
- * A trick to suppress uninitialized variable warning without generating any
- * code
- */
-#define uninitialized_var(x) x = x
-
-#if __GNUC_MINOR__ >= 3
-/* Mark functions as cold. gcc will assume any path leading to a call
- to them will be unlikely. This means a lot of manual unlikely()s
- are unnecessary now for any paths leading to the usual suspects
- like BUG(), printk(), panic() etc. [but let's keep them for now for
- older compilers]
-
- Early snapshots of gcc 4.3 don't support this and we can't detect this
- in the preprocessor, but we can live with this because they're unreleased.
- Maketime probing would be overkill here.
-
- gcc also has a __attribute__((__hot__)) to move hot functions into
- a special section, but I don't see any sense in this right now in
- the kernel context */
-#define __cold __attribute__((__cold__))
-
-
-#if __GNUC_MINOR__ >= 5
-/*
- * Mark a position in code as unreachable. This can be used to
- * suppress control flow warnings after asm blocks that transfer
- * control elsewhere.
- *
- * Early snapshots of gcc 4.5 don't support this and we can't detect
- * this in the preprocessor, but we can live with this because they're
- * unreleased. Really, we need to have autoconf for the kernel.
- */
-#define unreachable() __builtin_unreachable()
-#endif
-
-#endif
-
-#if __GNUC_MINOR__ > 0
-#define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
-#endif
-#if __GNUC_MINOR__ >= 4
-#define __compiletime_warning(message) __attribute__((warning(message)))
-#define __compiletime_error(message) __attribute__((error(message)))
-#endif
diff --git a/include/linux/compiler-intel.h b/include/linux/compiler-intel.h
new file mode 100644
index 0000000..d4c7113
--- /dev/null
+++ b/include/linux/compiler-intel.h
@@ -0,0 +1,45 @@
+#ifndef __LINUX_COMPILER_H
+#error "Please don't include <linux/compiler-intel.h> directly, include <linux/compiler.h> instead."
+#endif
+
+#ifdef __ECC
+
+/* Some compiler specific definitions are overwritten here
+ * for Intel ECC compiler
+ */
+
+#include <asm/intrinsics.h>
+
+/* Intel ECC compiler doesn't support gcc specific asm stmts.
+ * It uses intrinsics to do the equivalent things.
+ */
+#undef barrier
+#undef barrier_data
+#undef RELOC_HIDE
+#undef OPTIMIZER_HIDE_VAR
+
+#define barrier() __memory_barrier()
+#define barrier_data(ptr) barrier()
+
+#define RELOC_HIDE(ptr, off) \
+ ({ unsigned long __ptr; \
+ __ptr = (unsigned long) (ptr); \
+ (typeof(ptr)) (__ptr + (off)); })
+
+/* This should act as an optimization barrier on var.
+ * Given that this compiler does not have inline assembly, a compiler barrier
+ * is the best we can do.
+ */
+#define OPTIMIZER_HIDE_VAR(var) barrier()
+
+/* Intel ECC compiler doesn't support __builtin_types_compatible_p() */
+#define __must_be_array(a) 0
+
+#endif
+
+#ifndef __HAVE_BUILTIN_BSWAP16__
+/* icc has this, but it's called _bswap16 */
+#define __HAVE_BUILTIN_BSWAP16__
+#define __builtin_bswap16 _bswap16
+#endif
+
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 5be3dab..020ad16 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -5,16 +5,24 @@
#ifdef __CHECKER__
# define __user __attribute__((noderef, address_space(1)))
-# define __kernel /* default address space */
+# 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 __pmem __attribute__((noderef, address_space(5)))
+#ifdef CONFIG_SPARSE_RCU_POINTER
+# define __rcu __attribute__((noderef, address_space(4)))
+#else
+# define __rcu
+#endif
extern void __chk_user_ptr(const volatile void __user *);
extern void __chk_io_ptr(const volatile void __iomem *);
#else
@@ -27,20 +35,32 @@ extern void __chk_io_ptr(const volatile void __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 __pmem
#endif
+/* Indirect macros required for expanded argument pasting, eg. __LINE__. */
+#define ___PASTE(a,b) a##b
+#define __PASTE(a,b) ___PASTE(a,b)
+
#ifdef __KERNEL__
#ifdef __GNUC__
#include <linux/compiler-gcc.h>
#endif
+#if defined(CC_USING_HOTPATCH) && !defined(__CHECKER__)
+#define notrace __attribute__((hotpatch(0,0)))
+#else
#define notrace __attribute__((no_instrument_function))
+#endif
/* Intel compiler defines __GNUC__. So we will overwrite implementations
* coming from above header files here
@@ -49,6 +69,13 @@ extern void __chk_io_ptr(const volatile void __iomem *);
# include <linux/compiler-intel.h>
#endif
+/* Clang compiler defines __GNUC__. So we will overwrite implementations
+ * coming from above header files here
+ */
+#ifdef __clang__
+#include <linux/compiler-clang.h>
+#endif
+
/*
* Generic compiler-dependent macros required for kernel
* build go below this comment. Actual compiler/compiler version
@@ -117,7 +144,7 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
*/
#define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
#define __trace_if(cond) \
- if (__builtin_constant_p((cond)) ? !!(cond) : \
+ if (__builtin_constant_p(!!(cond)) ? !!(cond) : \
({ \
int ______r; \
static struct ftrace_branch_data \
@@ -144,6 +171,10 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
# define barrier() __memory_barrier()
#endif
+#ifndef barrier_data
+# define barrier_data(ptr) barrier()
+#endif
+
/* Unreachable code */
#ifndef unreachable
# define unreachable() do { } while (1)
@@ -156,6 +187,135 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
(typeof(ptr)) (__ptr + (off)); })
#endif
+#ifndef OPTIMIZER_HIDE_VAR
+#define OPTIMIZER_HIDE_VAR(var) barrier()
+#endif
+
+/* Not-quite-unique ID. */
+#ifndef __UNIQUE_ID
+# define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
+#endif
+
+#include <linux/types.h>
+
+#define __READ_ONCE_SIZE \
+({ \
+ switch (size) { \
+ case 1: *(__u8 *)res = *(volatile __u8 *)p; break; \
+ case 2: *(__u16 *)res = *(volatile __u16 *)p; break; \
+ case 4: *(__u32 *)res = *(volatile __u32 *)p; break; \
+ case 8: *(__u64 *)res = *(volatile __u64 *)p; break; \
+ default: \
+ barrier(); \
+ __builtin_memcpy((void *)res, (const void *)p, size); \
+ barrier(); \
+ } \
+})
+
+static __always_inline
+void __read_once_size(const volatile void *p, void *res, int size)
+{
+ __READ_ONCE_SIZE;
+}
+
+#ifdef CONFIG_KASAN
+/*
+ * This function is not 'inline' because __no_sanitize_address confilcts
+ * with inlining. Attempt to inline it may cause a build failure.
+ * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
+ * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
+ */
+static __no_sanitize_address __maybe_unused
+void __read_once_size_nocheck(const volatile void *p, void *res, int size)
+{
+ __READ_ONCE_SIZE;
+}
+#else
+static __always_inline
+void __read_once_size_nocheck(const volatile void *p, void *res, int size)
+{
+ __READ_ONCE_SIZE;
+}
+#endif
+
+static __always_inline void __write_once_size(volatile void *p, void *res, int size)
+{
+ switch (size) {
+ case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
+ case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
+ case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
+ case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
+ default:
+ barrier();
+ __builtin_memcpy((void *)p, (const void *)res, size);
+ barrier();
+ }
+}
+
+/*
+ * Prevent the compiler from merging or refetching reads or writes. The
+ * compiler is also forbidden from reordering successive instances of
+ * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the
+ * compiler is aware of some particular ordering. One way to make the
+ * compiler aware of ordering is to put the two invocations of READ_ONCE,
+ * WRITE_ONCE or ACCESS_ONCE() in different C statements.
+ *
+ * In contrast to ACCESS_ONCE these two macros will also work on aggregate
+ * data types like structs or unions. If the size of the accessed data
+ * type exceeds the word size of the machine (e.g., 32 bits or 64 bits)
+ * READ_ONCE() and WRITE_ONCE() will fall back to memcpy and print a
+ * compile-time warning.
+ *
+ * Their two major use cases are: (1) Mediating communication between
+ * process-level code and irq/NMI handlers, all running on the same CPU,
+ * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
+ * mutilate accesses that either do not require ordering or that interact
+ * with an explicit memory barrier or atomic instruction that provides the
+ * required ordering.
+ */
+
+#define __READ_ONCE(x, check) \
+({ \
+ union { typeof(x) __val; char __c[1]; } __u; \
+ if (check) \
+ __read_once_size(&(x), __u.__c, sizeof(x)); \
+ else \
+ __read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \
+ __u.__val; \
+})
+#define READ_ONCE(x) __READ_ONCE(x, 1)
+
+/*
+ * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
+ * to hide memory access from KASAN.
+ */
+#define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
+
+#define WRITE_ONCE(x, val) \
+({ \
+ union { typeof(x) __val; char __c[1]; } __u = \
+ { .__val = (__force typeof(x)) (val) }; \
+ __write_once_size(&(x), __u.__c, sizeof(x)); \
+ __u.__val; \
+})
+
+/**
+ * smp_cond_acquire() - Spin wait for cond with ACQUIRE ordering
+ * @cond: boolean expression to wait for
+ *
+ * Equivalent to using smp_load_acquire() on the condition variable but employs
+ * the control dependency of the wait to reduce the barrier on many platforms.
+ *
+ * The control dependency provides a LOAD->STORE order, the additional RMB
+ * provides LOAD->LOAD order, together they provide LOAD->{LOAD,STORE} order,
+ * aka. ACQUIRE.
+ */
+#define smp_cond_acquire(cond) do { \
+ while (!(cond)) \
+ cpu_relax(); \
+ smp_rmb(); /* ctrl + rmb := acquire */ \
+} while (0)
+
#endif /* __KERNEL__ */
#endif /* __ASSEMBLY__ */
@@ -228,7 +388,7 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
/*
* Rather then using noinline to prevent stack consumption, use
- * noinline_for_stack instead. For documentaiton reasons.
+ * noinline_for_stack instead. For documentation reasons.
*/
#define noinline_for_stack noinline
@@ -270,11 +430,28 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
# define __section(S) __attribute__ ((__section__(#S)))
#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)? */
#ifndef __same_type
# define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
#endif
+/* Is this type a native word size -- useful for atomic operations */
+#ifndef __native_word
+# define __native_word(t) (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
+#endif
+
/* Compile time object size, -1 for unknown */
#ifndef __compiletime_object_size
# define __compiletime_object_size(obj) -1
@@ -284,7 +461,48 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
#endif
#ifndef __compiletime_error
# define __compiletime_error(message)
+/*
+ * Sparse complains of variable sized arrays due to the temporary variable in
+ * __compiletime_assert. Unfortunately we can't just expand it out to make
+ * sparse see a constant array size without breaking compiletime_assert on old
+ * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
+ */
+# ifndef __CHECKER__
+# define __compiletime_error_fallback(condition) \
+ do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
+# endif
#endif
+#ifndef __compiletime_error_fallback
+# define __compiletime_error_fallback(condition) do { } while (0)
+#endif
+
+#define __compiletime_assert(condition, msg, prefix, suffix) \
+ do { \
+ bool __cond = !(condition); \
+ extern void prefix ## suffix(void) __compiletime_error(msg); \
+ if (__cond) \
+ prefix ## suffix(); \
+ __compiletime_error_fallback(__cond); \
+ } while (0)
+
+#define _compiletime_assert(condition, msg, prefix, suffix) \
+ __compiletime_assert(condition, msg, prefix, suffix)
+
+/**
+ * compiletime_assert - break build and emit msg if condition is false
+ * @condition: a compile-time constant condition to check
+ * @msg: a message to emit if condition is false
+ *
+ * In tradition of POSIX assert, this macro will break the build if the
+ * supplied condition is *false*, emitting the supplied error message if the
+ * compiler has support to do so.
+ */
+#define compiletime_assert(condition, msg) \
+ _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
+
+#define compiletime_assert_atomic_type(t) \
+ compiletime_assert(__native_word(t), \
+ "Need native word sized stores/loads for atomicity.")
/*
* Prevent the compiler from merging or refetching accesses. The compiler
@@ -293,11 +511,45 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
* to make the compiler aware of ordering is to put the two invocations of
* ACCESS_ONCE() in different C statements.
*
- * This macro does absolutely -nothing- to prevent the CPU from reordering,
- * merging, or refetching absolutely anything at any time. Its main intended
- * use is to mediate communication between process-level code and irq/NMI
- * handlers, all running on the same CPU.
+ * ACCESS_ONCE will only work on scalar types. For union types, ACCESS_ONCE
+ * on a union member will work as long as the size of the member matches the
+ * size of the union and the size is smaller than word size.
+ *
+ * The major use cases of ACCESS_ONCE used to be (1) Mediating communication
+ * between process-level code and irq/NMI handlers, all running on the same CPU,
+ * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
+ * mutilate accesses that either do not require ordering or that interact
+ * with an explicit memory barrier or atomic instruction that provides the
+ * required ordering.
+ *
+ * If possible use READ_ONCE()/WRITE_ONCE() instead.
*/
-#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
-
+#define __ACCESS_ONCE(x) ({ \
+ __maybe_unused typeof(x) __var = (__force typeof(x)) 0; \
+ (volatile typeof(x) *)&(x); })
+#define ACCESS_ONCE(x) (*__ACCESS_ONCE(x))
+
+/**
+ * lockless_dereference() - safely load a pointer for later dereference
+ * @p: The pointer to load
+ *
+ * Similar to rcu_dereference(), but for situations where the pointed-to
+ * object's lifetime is managed by something other than RCU. That
+ * "something other" might be reference counting or simple immortality.
+ */
+#define lockless_dereference(p) \
+({ \
+ typeof(p) _________p1 = READ_ONCE(p); \
+ smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
+ (_________p1); \
+})
+
+/* Ignore/forbid kprobes attach on very low level functions marked by this attribute: */
+#ifdef CONFIG_KPROBES
+# define __kprobes __attribute__((__section__(".kprobes.text")))
+# define nokprobe_inline __always_inline
+#else
+# define __kprobes
+# define nokprobe_inline inline
+#endif
#endif /* __LINUX_COMPILER_H */
--
2.7.4
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