include/rseq/rseq.h

   1 /* SPDX-License-Identifier: LGPL-2.1 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 extern __thread volatile struct rseq __rseq_abi;
  48
  49 #define rseq_likely(x)          __builtin_expect(!!(x), 1)
  50 #define rseq_unlikely(x)        __builtin_expect(!!(x), 0)
  51 #define rseq_barrier()          __asm__ __volatile__("" : : : "memory")
  52
  53 #define RSEQ_ACCESS_ONCE(x)     (*(__volatile__  __typeof__(x) *)&(x))
  54 #define RSEQ_WRITE_ONCE(x, v)   __extension__ ({ RSEQ_ACCESS_ONCE(x) = (v); })
  55 #define RSEQ_READ_ONCE(x)       RSEQ_ACCESS_ONCE(x)
  56
  57 #define __rseq_str_1(x) #x
  58 #define __rseq_str(x)           __rseq_str_1(x)
  59
  60 #define rseq_log(fmt, args...)                                                 \
  61         fprintf(stderr, fmt "(in %s() at " __FILE__ ":" __rseq_str(__LINE__)"\n", \
  62                 ## args, __func__)
  63
  64 #define rseq_bug(fmt, args...)          \
  65         do {                            \
  66                 rseq_log(fmt, ##args);  \
  67                 abort();                \
  68         } while (0)
  69
  70 #if defined(__x86_64__) || defined(__i386__)
  71 #include <rseq/rseq-x86.h>
  72 #elif defined(__ARMEL__)
  73 #include <rseq/rseq-arm.h>
  74 #elif defined(__PPC__)
  75 #include <rseq/rseq-ppc.h>
  76 #elif defined(__mips__)
  77 #include <rseq/rseq-mips.h>
  78 #elif defined(__s390__)
  79 #include <rseq/rseq-s390.h>
  80 #else
  81 #error unsupported target
  82 #endif
  83
  84 /*
  85  * Register rseq for the current thread. This needs to be called once
  86  * by any thread which uses restartable sequences, before they start
  87  * using restartable sequences, to ensure restartable sequences
  88  * succeed. A restartable sequence executed from a non-registered
  89  * thread will always fail.
  90  */
  91 int rseq_register_current_thread(void);
  92
  93 /*
  94  * Unregister rseq for current thread.
  95  */
  96 int rseq_unregister_current_thread(void);
  97
  98 /*
  99  * Restartable sequence fallback for reading the current CPU number.
 100  */
 101 int32_t rseq_fallback_current_cpu(void);
 102
 103 /*
 104  * Values returned can be either the current CPU number, -1 (rseq is
 105  * uninitialized), or -2 (rseq initialization has failed).
 106  */
 107 static inline int32_t rseq_current_cpu_raw(void)
 108 {
 109         return RSEQ_ACCESS_ONCE(__rseq_abi.cpu_id);
 110 }
 111
 112 /*
 113  * Returns a possible CPU number, which is typically the current CPU.
 114  * The returned CPU number can be used to prepare for an rseq critical
 115  * section, which will confirm whether the cpu number is indeed the
 116  * current one, and whether rseq is initialized.
 117  *
 118  * The CPU number returned by rseq_cpu_start should always be validated
 119  * by passing it to a rseq asm sequence, or by comparing it to the
 120  * return value of rseq_current_cpu_raw() if the rseq asm sequence
 121  * does not need to be invoked.
 122  */
 123 static inline uint32_t rseq_cpu_start(void)
 124 {
 125         return RSEQ_ACCESS_ONCE(__rseq_abi.cpu_id_start);
 126 }
 127
 128 static inline uint32_t rseq_current_cpu(void)
 129 {
 130         int32_t cpu;
 131
 132         cpu = rseq_current_cpu_raw();
 133         if (rseq_unlikely(cpu < 0))
 134                 cpu = rseq_fallback_current_cpu();
 135         return cpu;
 136 }
 137
 138 static inline void rseq_clear_rseq_cs(void)
 139 {
 140 #ifdef __LP64__
 141         __rseq_abi.rseq_cs.ptr = 0;
 142 #else
 143         __rseq_abi.rseq_cs.ptr.ptr32 = 0;
 144 #endif
 145 }
 146
 147 /*
 148  * rseq_prepare_unload() should be invoked by each thread executing a rseq
 149  * critical section at least once between their last critical section and
 150  * library unload of the library defining the rseq critical section
 151  * (struct rseq_cs). This also applies to use of rseq in code generated by
 152  * JIT: rseq_prepare_unload() should be invoked at least once by each
 153  * thread executing a rseq critical section before reclaim of the memory
 154  * holding the struct rseq_cs.
 155  */
 156 static inline void rseq_prepare_unload(void)
 157 {
 158         rseq_clear_rseq_cs();
 159 }
 160
 161 #endif  /* RSEQ_H_ */