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 extern __thread volatile struct rseq __rseq_abi;
  48 extern __thread volatile uint32_t __rseq_refcount;
  49
  50 #define rseq_likely(x)          __builtin_expect(!!(x), 1)
  51 #define rseq_unlikely(x)        __builtin_expect(!!(x), 0)
  52 #define rseq_barrier()          __asm__ __volatile__("" : : : "memory")
  53
  54 #define RSEQ_ACCESS_ONCE(x)     (*(__volatile__  __typeof__(x) *)&(x))
  55 #define RSEQ_WRITE_ONCE(x, v)   __extension__ ({ RSEQ_ACCESS_ONCE(x) = (v); })
  56 #define RSEQ_READ_ONCE(x)       RSEQ_ACCESS_ONCE(x)
  57
  58 #define __rseq_str_1(x) #x
  59 #define __rseq_str(x)           __rseq_str_1(x)
  60
  61 #define rseq_log(fmt, args...)                                                 \
  62         fprintf(stderr, fmt "(in %s() at " __FILE__ ":" __rseq_str(__LINE__)"\n", \
  63                 ## args, __func__)
  64
  65 #define rseq_bug(fmt, args...)          \
  66         do {                            \
  67                 rseq_log(fmt, ##args);  \
  68                 abort();                \
  69         } while (0)
  70
  71 #if defined(__x86_64__) || defined(__i386__)
  72 #include <rseq/rseq-x86.h>
  73 #elif defined(__ARMEL__)
  74 #include <rseq/rseq-arm.h>
  75 #elif defined(__PPC__)
  76 #include <rseq/rseq-ppc.h>
  77 #elif defined(__mips__)
  78 #include <rseq/rseq-mips.h>
  79 #elif defined(__s390__)
  80 #include <rseq/rseq-s390.h>
  81 #else
  82 #error unsupported target
  83 #endif
  84
  85 /*
  86  * Register rseq for the current thread. This needs to be called once
  87  * by any thread which uses restartable sequences, before they start
  88  * using restartable sequences, to ensure restartable sequences
  89  * succeed. A restartable sequence executed from a non-registered
  90  * thread will always fail.
  91  */
  92 int rseq_register_current_thread(void);
  93
  94 /*
  95  * Unregister rseq for current thread.
  96  */
  97 int rseq_unregister_current_thread(void);
  98
  99 /*
 100  * Restartable sequence fallback for reading the current CPU number.
 101  */
 102 int32_t rseq_fallback_current_cpu(void);
 103
 104 int rseq_available(void);
 105
 106 /*
 107  * Values returned can be either the current CPU number, -1 (rseq is
 108  * uninitialized), or -2 (rseq initialization has failed).
 109  */
 110 static inline int32_t rseq_current_cpu_raw(void)
 111 {
 112         return RSEQ_ACCESS_ONCE(__rseq_abi.cpu_id);
 113 }
 114
 115 /*
 116  * Returns a possible CPU number, which is typically the current CPU.
 117  * The returned CPU number can be used to prepare for an rseq critical
 118  * section, which will confirm whether the cpu number is indeed the
 119  * current one, and whether rseq is initialized.
 120  *
 121  * The CPU number returned by rseq_cpu_start should always be validated
 122  * by passing it to a rseq asm sequence, or by comparing it to the
 123  * return value of rseq_current_cpu_raw() if the rseq asm sequence
 124  * does not need to be invoked.
 125  */
 126 static inline uint32_t rseq_cpu_start(void)
 127 {
 128         return RSEQ_ACCESS_ONCE(__rseq_abi.cpu_id_start);
 129 }
 130
 131 static inline uint32_t rseq_current_cpu(void)
 132 {
 133         int32_t cpu;
 134
 135         cpu = rseq_current_cpu_raw();
 136         if (rseq_unlikely(cpu < 0))
 137                 cpu = rseq_fallback_current_cpu();
 138         return cpu;
 139 }
 140
 141 static inline void rseq_clear_rseq_cs(void)
 142 {
 143 #ifdef __LP64__
 144         __rseq_abi.rseq_cs.ptr = 0;
 145 #else
 146         __rseq_abi.rseq_cs.ptr.ptr32 = 0;
 147 #endif
 148 }
 149
 150 /*
 151  * rseq_prepare_unload() should be invoked by each thread executing a rseq
 152  * critical section at least once between their last critical section and
 153  * library unload of the library defining the rseq critical section
 154  * (struct rseq_cs). This also applies to use of rseq in code generated by
 155  * JIT: rseq_prepare_unload() should be invoked at least once by each
 156  * thread executing a rseq critical section before reclaim of the memory
 157  * holding the struct rseq_cs.
 158  */
 159 static inline void rseq_prepare_unload(void)
 160 {
 161         rseq_clear_rseq_cs();
 162 }
 163
 164 #endif  /* RSEQ_H_ */