include/linux/percpu-defs.h

   1 #ifndef _LINUX_PERCPU_DEFS_H
   2 #define _LINUX_PERCPU_DEFS_H
   3
   4 #ifdef CONFIG_PAGE_TABLE_ISOLATION
   5 #define USER_MAPPED_SECTION "..user_mapped"
   6 #else
   7 #define USER_MAPPED_SECTION ""
   8 #endif
   9
  10 /*
  11  * Base implementations of per-CPU variable declarations and definitions, where
  12  * the section in which the variable is to be placed is provided by the
  13  * 'sec' argument.  This may be used to affect the parameters governing the
  14  * variable's storage.
  15  *
  16  * NOTE!  The sections for the DECLARE and for the DEFINE must match, lest
  17  * linkage errors occur due the compiler generating the wrong code to access
  18  * that section.
  19  */
  20 #define __PCPU_ATTRS(sec)                                               \
  21         __percpu __attribute__((section(PER_CPU_BASE_SECTION sec)))     \
  22         PER_CPU_ATTRIBUTES
  23
  24 #define __PCPU_DUMMY_ATTRS                                              \
  25         __attribute__((section(".discard"), unused))
  26
  27 /*
  28  * Macro which verifies @ptr is a percpu pointer without evaluating
  29  * @ptr.  This is to be used in percpu accessors to verify that the
  30  * input parameter is a percpu pointer.
  31  *
  32  * + 0 is required in order to convert the pointer type from a
  33  * potential array type to a pointer to a single item of the array.
  34  */
  35 #define __verify_pcpu_ptr(ptr)  do {                                    \
  36         const void __percpu *__vpp_verify = (typeof((ptr) + 0))NULL;    \
  37         (void)__vpp_verify;                                             \
  38 } while (0)
  39
  40 /*
  41  * s390 and alpha modules require percpu variables to be defined as
  42  * weak to force the compiler to generate GOT based external
  43  * references for them.  This is necessary because percpu sections
  44  * will be located outside of the usually addressable area.
  45  *
  46  * This definition puts the following two extra restrictions when
  47  * defining percpu variables.
  48  *
  49  * 1. The symbol must be globally unique, even the static ones.
  50  * 2. Static percpu variables cannot be defined inside a function.
  51  *
  52  * Archs which need weak percpu definitions should define
  53  * ARCH_NEEDS_WEAK_PER_CPU in asm/percpu.h when necessary.
  54  *
  55  * To ensure that the generic code observes the above two
  56  * restrictions, if CONFIG_DEBUG_FORCE_WEAK_PER_CPU is set weak
  57  * definition is used for all cases.
  58  */
  59 #if defined(ARCH_NEEDS_WEAK_PER_CPU) || defined(CONFIG_DEBUG_FORCE_WEAK_PER_CPU)
  60 /*
  61  * __pcpu_scope_* dummy variable is used to enforce scope.  It
  62  * receives the static modifier when it's used in front of
  63  * DEFINE_PER_CPU() and will trigger build failure if
  64  * DECLARE_PER_CPU() is used for the same variable.
  65  *
  66  * __pcpu_unique_* dummy variable is used to enforce symbol uniqueness
  67  * such that hidden weak symbol collision, which will cause unrelated
  68  * variables to share the same address, can be detected during build.
  69  */
  70 #define DECLARE_PER_CPU_SECTION(type, name, sec)                        \
  71         extern __PCPU_DUMMY_ATTRS char __pcpu_scope_##name;             \
  72         extern __PCPU_ATTRS(sec) __typeof__(type) name
  73
  74 #define DEFINE_PER_CPU_SECTION(type, name, sec)                         \
  75         __PCPU_DUMMY_ATTRS char __pcpu_scope_##name;                    \
  76         extern __PCPU_DUMMY_ATTRS char __pcpu_unique_##name;            \
  77         __PCPU_DUMMY_ATTRS char __pcpu_unique_##name;                   \
  78         extern __PCPU_ATTRS(sec) __typeof__(type) name;                 \
  79         __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak                 \
  80         __typeof__(type) name
  81 #else
  82 /*
  83  * Normal declaration and definition macros.
  84  */
  85 #define DECLARE_PER_CPU_SECTION(type, name, sec)                        \
  86         extern __PCPU_ATTRS(sec) __typeof__(type) name
  87
  88 #define DEFINE_PER_CPU_SECTION(type, name, sec)                         \
  89         __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES                        \
  90         __typeof__(type) name
  91 #endif
  92
  93 /*
  94  * Variant on the per-CPU variable declaration/definition theme used for
  95  * ordinary per-CPU variables.
  96  */
  97 #define DECLARE_PER_CPU(type, name)                                     \
  98         DECLARE_PER_CPU_SECTION(type, name, "")
  99
 100 #define DEFINE_PER_CPU(type, name)                                      \
 101         DEFINE_PER_CPU_SECTION(type, name, "")
 102
 103 #define DECLARE_PER_CPU_USER_MAPPED(type, name)                         \
 104         DECLARE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION)
 105
 106 #define DEFINE_PER_CPU_USER_MAPPED(type, name)                          \
 107         DEFINE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION)
 108
 109 /*
 110  * Declaration/definition used for per-CPU variables that must come first in
 111  * the set of variables.
 112  */
 113 #define DECLARE_PER_CPU_FIRST(type, name)                               \
 114         DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
 115
 116 #define DEFINE_PER_CPU_FIRST(type, name)                                \
 117         DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
 118
 119 /*
 120  * Declaration/definition used for per-CPU variables that must be cacheline
 121  * aligned under SMP conditions so that, whilst a particular instance of the
 122  * data corresponds to a particular CPU, inefficiencies due to direct access by
 123  * other CPUs are reduced by preventing the data from unnecessarily spanning
 124  * cachelines.
 125  *
 126  * An example of this would be statistical data, where each CPU's set of data
 127  * is updated by that CPU alone, but the data from across all CPUs is collated
 128  * by a CPU processing a read from a proc file.
 129  */
 130 #define DECLARE_PER_CPU_SHARED_ALIGNED(type, name)                      \
 131         DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
 132         ____cacheline_aligned_in_smp
 133
 134 #define DEFINE_PER_CPU_SHARED_ALIGNED(type, name)                       \
 135         DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
 136         ____cacheline_aligned_in_smp
 137
 138 #define DECLARE_PER_CPU_SHARED_ALIGNED_USER_MAPPED(type, name)          \
 139         DECLARE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION PER_CPU_SHARED_ALIGNED_SECTION) \
 140         ____cacheline_aligned_in_smp
 141
 142 #define DEFINE_PER_CPU_SHARED_ALIGNED_USER_MAPPED(type, name)           \
 143         DEFINE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION PER_CPU_SHARED_ALIGNED_SECTION) \
 144         ____cacheline_aligned_in_smp
 145
 146 #define DECLARE_PER_CPU_ALIGNED(type, name)                             \
 147         DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION)    \
 148         ____cacheline_aligned
 149
 150 #define DEFINE_PER_CPU_ALIGNED(type, name)                              \
 151         DEFINE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION)     \
 152         ____cacheline_aligned
 153
 154 /*
 155  * Declaration/definition used for per-CPU variables that must be page aligned.
 156  */
 157 #define DECLARE_PER_CPU_PAGE_ALIGNED(type, name)                        \
 158         DECLARE_PER_CPU_SECTION(type, name, "..page_aligned")           \
 159         __aligned(PAGE_SIZE)
 160
 161 #define DEFINE_PER_CPU_PAGE_ALIGNED(type, name)                         \
 162         DEFINE_PER_CPU_SECTION(type, name, "..page_aligned")            \
 163         __aligned(PAGE_SIZE)
 164 /*
 165  * Declaration/definition used for per-CPU variables that must be page aligned and need to be mapped in user mode.
 166  */
 167 #define DECLARE_PER_CPU_PAGE_ALIGNED_USER_MAPPED(type, name)            \
 168         DECLARE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION"..page_aligned") \
 169         __aligned(PAGE_SIZE)
 170
 171 #define DEFINE_PER_CPU_PAGE_ALIGNED_USER_MAPPED(type, name)             \
 172         DEFINE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION"..page_aligned") \
 173         __aligned(PAGE_SIZE)
 174
 175 /*
 176  * Declaration/definition used for per-CPU variables that must be read mostly.
 177  */
 178 #define DECLARE_PER_CPU_READ_MOSTLY(type, name)                         \
 179         DECLARE_PER_CPU_SECTION(type, name, "..read_mostly")
 180
 181 #define DEFINE_PER_CPU_READ_MOSTLY(type, name)                          \
 182         DEFINE_PER_CPU_SECTION(type, name, "..read_mostly")
 183
 184 /*
 185  * Intermodule exports for per-CPU variables.  sparse forgets about
 186  * address space across EXPORT_SYMBOL(), change EXPORT_SYMBOL() to
 187  * noop if __CHECKER__.
 188  */
 189 #ifndef __CHECKER__
 190 #define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(var)
 191 #define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(var)
 192 #else
 193 #define EXPORT_PER_CPU_SYMBOL(var)
 194 #define EXPORT_PER_CPU_SYMBOL_GPL(var)
 195 #endif
 196
 197 #endif /* _LINUX_PERCPU_DEFS_H */