include/linux/percpu-defs.h

   1 #ifndef _LINUX_PERCPU_DEFS_H
   2 #define _LINUX_PERCPU_DEFS_H
   3
   4 /*
   5  * Base implementations of per-CPU variable declarations and definitions, where
   6  * the section in which the variable is to be placed is provided by the
   7  * 'sec' argument.  This may be used to affect the parameters governing the
   8  * variable's storage.
   9  *
  10  * NOTE!  The sections for the DECLARE and for the DEFINE must match, lest
  11  * linkage errors occur due the compiler generating the wrong code to access
  12  * that section.
  13  */
  14 #define __PCPU_ATTRS(sec)                                               \
  15         __percpu __attribute__((section(PER_CPU_BASE_SECTION sec)))     \
  16         PER_CPU_ATTRIBUTES
  17
  18 #define __PCPU_DUMMY_ATTRS                                              \
  19         __attribute__((section(".discard"), unused))
  20
  21 /*
  22  * Macro which verifies @ptr is a percpu pointer without evaluating
  23  * @ptr.  This is to be used in percpu accessors to verify that the
  24  * input parameter is a percpu pointer.
  25  */
  26 #define __verify_pcpu_ptr(ptr)  do {                                    \
  27         const void __percpu *__vpp_verify = (typeof(ptr))NULL;          \
  28         (void)__vpp_verify;                                             \
  29 } while (0)
  30
  31 #ifdef CONFIG_PAGE_TABLE_ISOLATION
  32 #define USER_MAPPED_SECTION "..user_mapped"
  33 #else
  34 #define USER_MAPPED_SECTION ""
  35 #endif
  36
  37 /*
  38  * s390 and alpha modules require percpu variables to be defined as
  39  * weak to force the compiler to generate GOT based external
  40  * references for them.  This is necessary because percpu sections
  41  * will be located outside of the usually addressable area.
  42  *
  43  * This definition puts the following two extra restrictions when
  44  * defining percpu variables.
  45  *
  46  * 1. The symbol must be globally unique, even the static ones.
  47  * 2. Static percpu variables cannot be defined inside a function.
  48  *
  49  * Archs which need weak percpu definitions should define
  50  * ARCH_NEEDS_WEAK_PER_CPU in asm/percpu.h when necessary.
  51  *
  52  * To ensure that the generic code observes the above two
  53  * restrictions, if CONFIG_DEBUG_FORCE_WEAK_PER_CPU is set weak
  54  * definition is used for all cases.
  55  */
  56 #if defined(ARCH_NEEDS_WEAK_PER_CPU) || defined(CONFIG_DEBUG_FORCE_WEAK_PER_CPU)
  57 /*
  58  * __pcpu_scope_* dummy variable is used to enforce scope.  It
  59  * receives the static modifier when it's used in front of
  60  * DEFINE_PER_CPU() and will trigger build failure if
  61  * DECLARE_PER_CPU() is used for the same variable.
  62  *
  63  * __pcpu_unique_* dummy variable is used to enforce symbol uniqueness
  64  * such that hidden weak symbol collision, which will cause unrelated
  65  * variables to share the same address, can be detected during build.
  66  */
  67 #define DECLARE_PER_CPU_SECTION(type, name, sec)                        \
  68         extern __PCPU_DUMMY_ATTRS char __pcpu_scope_##name;             \
  69         extern __PCPU_ATTRS(sec) __typeof__(type) name
  70
  71 #define DEFINE_PER_CPU_SECTION(type, name, sec)                         \
  72         __PCPU_DUMMY_ATTRS char __pcpu_scope_##name;                    \
  73         extern __PCPU_DUMMY_ATTRS char __pcpu_unique_##name;            \
  74         __PCPU_DUMMY_ATTRS char __pcpu_unique_##name;                   \
  75         __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak                 \
  76         __typeof__(type) name
  77 #else
  78 /*
  79  * Normal declaration and definition macros.
  80  */
  81 #define DECLARE_PER_CPU_SECTION(type, name, sec)                        \
  82         extern __PCPU_ATTRS(sec) __typeof__(type) name
  83
  84 #define DEFINE_PER_CPU_SECTION(type, name, sec)                         \
  85         __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES                        \
  86         __typeof__(type) name
  87 #endif
  88
  89 /*
  90  * Variant on the per-CPU variable declaration/definition theme used for
  91  * ordinary per-CPU variables.
  92  */
  93 #define DECLARE_PER_CPU(type, name)                                     \
  94         DECLARE_PER_CPU_SECTION(type, name, "")
  95
  96 #define DEFINE_PER_CPU(type, name)                                      \
  97         DEFINE_PER_CPU_SECTION(type, name, "")
  98
  99 #define DECLARE_PER_CPU_USER_MAPPED(type, name)                         \
 100         DECLARE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION)
 101
 102 #define DEFINE_PER_CPU_USER_MAPPED(type, name)                          \
 103         DEFINE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION)
 104
 105 /*
 106  * Declaration/definition used for per-CPU variables that must come first in
 107  * the set of variables.
 108  */
 109 #define DECLARE_PER_CPU_FIRST(type, name)                               \
 110         DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
 111
 112 #define DEFINE_PER_CPU_FIRST(type, name)                                \
 113         DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
 114
 115 /*
 116  * Declaration/definition used for per-CPU variables that must be cacheline
 117  * aligned under SMP conditions so that, whilst a particular instance of the
 118  * data corresponds to a particular CPU, inefficiencies due to direct access by
 119  * other CPUs are reduced by preventing the data from unnecessarily spanning
 120  * cachelines.
 121  *
 122  * An example of this would be statistical data, where each CPU's set of data
 123  * is updated by that CPU alone, but the data from across all CPUs is collated
 124  * by a CPU processing a read from a proc file.
 125  */
 126 #define DECLARE_PER_CPU_SHARED_ALIGNED(type, name)                      \
 127         DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
 128         ____cacheline_aligned_in_smp
 129
 130 #define DEFINE_PER_CPU_SHARED_ALIGNED(type, name)                       \
 131         DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
 132         ____cacheline_aligned_in_smp
 133
 134 #define DECLARE_PER_CPU_SHARED_ALIGNED_USER_MAPPED(type, name)          \
 135         DECLARE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION PER_CPU_SHARED_ALIGNED_SECTION) \
 136         ____cacheline_aligned_in_smp
 137
 138 #define DEFINE_PER_CPU_SHARED_ALIGNED_USER_MAPPED(type, name)           \
 139         DEFINE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION PER_CPU_SHARED_ALIGNED_SECTION) \
 140         ____cacheline_aligned_in_smp
 141
 142 #define DECLARE_PER_CPU_ALIGNED(type, name)                             \
 143         DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION)    \
 144         ____cacheline_aligned
 145
 146 #define DEFINE_PER_CPU_ALIGNED(type, name)                              \
 147         DEFINE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION)     \
 148         ____cacheline_aligned
 149
 150 /*
 151  * Declaration/definition used for per-CPU variables that must be page aligned.
 152  */
 153 #define DECLARE_PER_CPU_PAGE_ALIGNED(type, name)                        \
 154         DECLARE_PER_CPU_SECTION(type, name, "..page_aligned")           \
 155         __aligned(PAGE_SIZE)
 156
 157 #define DEFINE_PER_CPU_PAGE_ALIGNED(type, name)                         \
 158         DEFINE_PER_CPU_SECTION(type, name, "..page_aligned")            \
 159         __aligned(PAGE_SIZE)
 160 /*
 161  * Declaration/definition used for per-CPU variables that must be page aligned and need to be mapped in user mode.
 162  */
 163 #define DECLARE_PER_CPU_PAGE_ALIGNED_USER_MAPPED(type, name)            \
 164         DECLARE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION"..page_aligned") \
 165         __aligned(PAGE_SIZE)
 166
 167 #define DEFINE_PER_CPU_PAGE_ALIGNED_USER_MAPPED(type, name)             \
 168         DEFINE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION"..page_aligned") \
 169         __aligned(PAGE_SIZE)
 170
 171 /*
 172  * Declaration/definition used for per-CPU variables that must be read mostly.
 173  */
 174 #define DECLARE_PER_CPU_READ_MOSTLY(type, name)                         \
 175         DECLARE_PER_CPU_SECTION(type, name, "..readmostly")
 176
 177 #define DEFINE_PER_CPU_READ_MOSTLY(type, name)                          \
 178         DEFINE_PER_CPU_SECTION(type, name, "..readmostly")
 179
 180 /*
 181  * Intermodule exports for per-CPU variables.  sparse forgets about
 182  * address space across EXPORT_SYMBOL(), change EXPORT_SYMBOL() to
 183  * noop if __CHECKER__.
 184  */
 185 #ifndef __CHECKER__
 186 #define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(var)
 187 #define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(var)
 188 #else
 189 #define EXPORT_PER_CPU_SYMBOL(var)
 190 #define EXPORT_PER_CPU_SYMBOL_GPL(var)
 191 #endif
 192
 193 #endif /* _LINUX_PERCPU_DEFS_H */