include/rseq/rseq.h

   1 /* SPDX-License-Identifier: LGPL-2.1-only OR MIT */
   2 /*
   3  * rseq.h
   4  *
   5  * (C) Copyright 2016-2018 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   6  */
   7
   8 #ifndef RSEQ_H
   9 #define RSEQ_H
  10
  11 #include <stdint.h>
  12 #include <stdbool.h>
  13 #include <pthread.h>
  14 #include <signal.h>
  15 #include <sched.h>
  16 #include <errno.h>
  17 #include <stdio.h>
  18 #include <stdlib.h>
  19 #include <sched.h>
  20 #include <linux/rseq.h>
  21
  22 /*
  23  * Empty code injection macros, override when testing.
  24  * It is important to consider that the ASM injection macros need to be
  25  * fully reentrant (e.g. do not modify the stack).
  26  */
  27 #ifndef RSEQ_INJECT_ASM
  28 #define RSEQ_INJECT_ASM(n)
  29 #endif
  30
  31 #ifndef RSEQ_INJECT_C
  32 #define RSEQ_INJECT_C(n)
  33 #endif
  34
  35 #ifndef RSEQ_INJECT_INPUT
  36 #define RSEQ_INJECT_INPUT
  37 #endif
  38
  39 #ifndef RSEQ_INJECT_CLOBBER
  40 #define RSEQ_INJECT_CLOBBER
  41 #endif
  42
  43 #ifndef RSEQ_INJECT_FAILED
  44 #define RSEQ_INJECT_FAILED
  45 #endif
  46
  47 #ifdef __cplusplus
  48 extern "C" {
  49 #endif
  50
  51 /* Offset from the thread pointer to the rseq area.  */
  52 extern int rseq_offset;
  53 /* Size of the registered rseq area.  0 if the registration was
  54    unsuccessful.  */
  55 extern unsigned int rseq_size;
  56 /* Flags used during rseq registration.  */
  57 extern unsigned int rseq_flags;
  58
  59 #ifdef __cplusplus
  60 }
  61 #endif
  62
  63 #define rseq_likely(x)          __builtin_expect(!!(x), 1)
  64 #define rseq_unlikely(x)        __builtin_expect(!!(x), 0)
  65 #define rseq_barrier()          __asm__ __volatile__("" : : : "memory")
  66
  67 #define RSEQ_ACCESS_ONCE(x)     (*(__volatile__  __typeof__(x) *)&(x))
  68 #define RSEQ_WRITE_ONCE(x, v)   __extension__ ({ RSEQ_ACCESS_ONCE(x) = (v); })
  69 #define RSEQ_READ_ONCE(x)       RSEQ_ACCESS_ONCE(x)
  70
  71 #define __rseq_str_1(x) #x
  72 #define __rseq_str(x)           __rseq_str_1(x)
  73
  74 #define rseq_log(fmt, args...)                                                 \
  75         fprintf(stderr, fmt "(in %s() at " __FILE__ ":" __rseq_str(__LINE__)"\n", \
  76                 ## args, __func__)
  77
  78 #define rseq_bug(fmt, args...)          \
  79         do {                            \
  80                 rseq_log(fmt, ##args);  \
  81                 abort();                \
  82         } while (0)
  83
  84 #if defined(__x86_64__) || defined(__i386__)
  85 #include <rseq/rseq-x86-thread-pointer.h>
  86 #elif defined(__PPC__)
  87 #include <rseq/rseq-ppc-thread-pointer.h>
  88 #else
  89 /* Use gcc builtin thread pointer. */
  90 static inline void *rseq_thread_pointer(void)
  91 {
  92         return __builtin_thread_pointer();
  93 }
  94 #endif
  95
  96 static inline struct rseq *rseq_get_abi(void)
  97 {
  98         return (struct rseq *) (rseq_thread_pointer() + rseq_offset);
  99 }
 100
 101 #if defined(__x86_64__) || defined(__i386__)
 102 #include <rseq/rseq-x86.h>
 103 #elif defined(__ARMEL__) || defined(__ARMEB__)
 104 #include <rseq/rseq-arm.h>
 105 #elif defined (__AARCH64EL__)
 106 #include <rseq/rseq-arm64.h>
 107 #elif defined(__PPC__)
 108 #include <rseq/rseq-ppc.h>
 109 #elif defined(__mips__)
 110 #include <rseq/rseq-mips.h>
 111 #elif defined(__s390__)
 112 #include <rseq/rseq-s390.h>
 113 #else
 114 #error unsupported target
 115 #endif
 116
 117 #ifdef __cplusplus
 118 extern "C" {
 119 #endif
 120
 121 /*
 122  * Register rseq for the current thread. This needs to be called once
 123  * by any thread which uses restartable sequences, before they start
 124  * using restartable sequences, to ensure restartable sequences
 125  * succeed. A restartable sequence executed from a non-registered
 126  * thread will always fail.
 127  */
 128 int rseq_register_current_thread(void);
 129
 130 /*
 131  * Unregister rseq for current thread.
 132  */
 133 int rseq_unregister_current_thread(void);
 134
 135 /*
 136  * Restartable sequence fallback for reading the current CPU number.
 137  */
 138 int32_t rseq_fallback_current_cpu(void);
 139
 140 int rseq_available(void);
 141
 142 /*
 143  * Values returned can be either the current CPU number, -1 (rseq is
 144  * uninitialized), or -2 (rseq initialization has failed).
 145  */
 146 static inline int32_t rseq_current_cpu_raw(void)
 147 {
 148         return RSEQ_READ_ONCE(rseq_get_abi()->cpu_id);
 149 }
 150
 151 /*
 152  * Returns a possible CPU number, which is typically the current CPU.
 153  * The returned CPU number can be used to prepare for an rseq critical
 154  * section, which will confirm whether the cpu number is indeed the
 155  * current one, and whether rseq is initialized.
 156  *
 157  * The CPU number returned by rseq_cpu_start should always be validated
 158  * by passing it to a rseq asm sequence, or by comparing it to the
 159  * return value of rseq_current_cpu_raw() if the rseq asm sequence
 160  * does not need to be invoked.
 161  */
 162 static inline uint32_t rseq_cpu_start(void)
 163 {
 164         return RSEQ_READ_ONCE(rseq_get_abi()->cpu_id_start);
 165 }
 166
 167 static inline uint32_t rseq_current_cpu(void)
 168 {
 169         int32_t cpu;
 170
 171         cpu = rseq_current_cpu_raw();
 172         if (rseq_unlikely(cpu < 0))
 173                 cpu = rseq_fallback_current_cpu();
 174         return cpu;
 175 }
 176
 177 static inline void rseq_clear_rseq_cs(void)
 178 {
 179 #ifdef __LP64__
 180         RSEQ_WRITE_ONCE(rseq_get_abi()->rseq_cs.ptr, 0);
 181 #else
 182         RSEQ_WRITE_ONCE(rseq_get_abi()->rseq_cs.ptr.ptr32, 0);
 183 #endif
 184 }
 185
 186 /*
 187  * rseq_prepare_unload() should be invoked by each thread executing a rseq
 188  * critical section at least once between their last critical section and
 189  * library unload of the library defining the rseq critical section
 190  * (struct rseq_cs). This also applies to use of rseq in code generated by
 191  * JIT: rseq_prepare_unload() should be invoked at least once by each
 192  * thread executing a rseq critical section before reclaim of the memory
 193  * holding the struct rseq_cs.
 194  */
 195 static inline void rseq_prepare_unload(void)
 196 {
 197         rseq_clear_rseq_cs();
 198 }
 199
 200 #ifdef __cplusplus
 201 }
 202 #endif
 203
 204 #endif  /* RSEQ_H_ */