include/rseq/rseq.h

   1 /* SPDX-License-Identifier: LGPL-2.1-only OR MIT */
   2 /*
   3  * rseq.h
   4  *
   5  * (C) Copyright 2016-2022 - 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 <stddef.h>
  21 #include <rseq/rseq-abi.h>
  22 #include <rseq/compiler.h>
  23
  24 /*
  25  * Empty code injection macros, override when testing.
  26  * It is important to consider that the ASM injection macros need to be
  27  * fully reentrant (e.g. do not modify the stack).
  28  */
  29 #ifndef RSEQ_INJECT_ASM
  30 #define RSEQ_INJECT_ASM(n)
  31 #endif
  32
  33 #ifndef RSEQ_INJECT_C
  34 #define RSEQ_INJECT_C(n)
  35 #endif
  36
  37 #ifndef RSEQ_INJECT_INPUT
  38 #define RSEQ_INJECT_INPUT
  39 #endif
  40
  41 #ifndef RSEQ_INJECT_CLOBBER
  42 #define RSEQ_INJECT_CLOBBER
  43 #endif
  44
  45 #ifndef RSEQ_INJECT_FAILED
  46 #define RSEQ_INJECT_FAILED
  47 #endif
  48
  49
  50 /*
  51  * User code can define RSEQ_GET_ABI_OVERRIDE to override the
  52  * rseq_get_abi() implementation, for instance to use glibc's symbols
  53  * directly.
  54  */
  55 #ifndef RSEQ_GET_ABI_OVERRIDE
  56
  57 # include <rseq/rseq-thread-pointer.h>
  58
  59 # ifdef __cplusplus
  60 extern "C" {
  61 # endif
  62
  63 /* Offset from the thread pointer to the rseq area.  */
  64 extern ptrdiff_t rseq_offset;
  65 /* Size of the registered rseq area.  0 if the registration was
  66    unsuccessful.  */
  67 extern unsigned int rseq_size;
  68 /* Flags used during rseq registration.  */
  69 extern unsigned int rseq_flags;
  70
  71 static inline struct rseq_abi *rseq_get_abi(void)
  72 {
  73         return (struct rseq_abi *) ((uintptr_t) rseq_thread_pointer() + rseq_offset);
  74 }
  75
  76 # ifdef __cplusplus
  77 }
  78 # endif
  79
  80 #endif /* RSEQ_GET_ABI_OVERRIDE */
  81
  82 #define rseq_likely(x)          __builtin_expect(!!(x), 1)
  83 #define rseq_unlikely(x)        __builtin_expect(!!(x), 0)
  84 #define rseq_barrier()          __asm__ __volatile__("" : : : "memory")
  85
  86 #define RSEQ_ACCESS_ONCE(x)     (*(__volatile__  __typeof__(x) *)&(x))
  87 #define RSEQ_WRITE_ONCE(x, v)   __extension__ ({ RSEQ_ACCESS_ONCE(x) = (v); })
  88 #define RSEQ_READ_ONCE(x)       RSEQ_ACCESS_ONCE(x)
  89
  90 #define __rseq_str_1(x) #x
  91 #define __rseq_str(x)           __rseq_str_1(x)
  92
  93 #define rseq_log(fmt, args...)                                                 \
  94         fprintf(stderr, fmt "(in %s() at " __FILE__ ":" __rseq_str(__LINE__)"\n", \
  95                 ## args, __func__)
  96
  97 #define rseq_bug(fmt, args...)          \
  98         do {                            \
  99                 rseq_log(fmt, ##args);  \
 100                 abort();                \
 101         } while (0)
 102
 103 #if defined(__x86_64__) || defined(__i386__)
 104 #include <rseq/rseq-x86.h>
 105 #elif defined(__ARMEL__) || defined(__ARMEB__)
 106 #include <rseq/rseq-arm.h>
 107 #elif defined (__AARCH64EL__)
 108 #include <rseq/rseq-arm64.h>
 109 #elif defined(__PPC__)
 110 #include <rseq/rseq-ppc.h>
 111 #elif defined(__mips__)
 112 #include <rseq/rseq-mips.h>
 113 #elif defined(__s390__)
 114 #include <rseq/rseq-s390.h>
 115 #else
 116 #error unsupported target
 117 #endif
 118
 119 #ifdef __cplusplus
 120 extern "C" {
 121 #endif
 122
 123 /*
 124  * Register rseq for the current thread. This needs to be called once
 125  * by any thread which uses restartable sequences, before they start
 126  * using restartable sequences, to ensure restartable sequences
 127  * succeed. A restartable sequence executed from a non-registered
 128  * thread will always fail.
 129  */
 130 int rseq_register_current_thread(void);
 131
 132 /*
 133  * Unregister rseq for current thread.
 134  */
 135 int rseq_unregister_current_thread(void);
 136
 137 /*
 138  * Restartable sequence fallback for reading the current CPU number.
 139  */
 140 int32_t rseq_fallback_current_cpu(void);
 141
 142 int rseq_available(void);
 143
 144 /*
 145  * Values returned can be either the current CPU number, -1 (rseq is
 146  * uninitialized), or -2 (rseq initialization has failed).
 147  */
 148 static inline int32_t rseq_current_cpu_raw(void)
 149 {
 150         return RSEQ_READ_ONCE(rseq_get_abi()->cpu_id);
 151 }
 152
 153 /*
 154  * Returns a possible CPU number, which is typically the current CPU.
 155  * The returned CPU number can be used to prepare for an rseq critical
 156  * section, which will confirm whether the cpu number is indeed the
 157  * current one, and whether rseq is initialized.
 158  *
 159  * The CPU number returned by rseq_cpu_start should always be validated
 160  * by passing it to a rseq asm sequence, or by comparing it to the
 161  * return value of rseq_current_cpu_raw() if the rseq asm sequence
 162  * does not need to be invoked.
 163  */
 164 static inline uint32_t rseq_cpu_start(void)
 165 {
 166         return RSEQ_READ_ONCE(rseq_get_abi()->cpu_id_start);
 167 }
 168
 169 static inline uint32_t rseq_current_cpu(void)
 170 {
 171         int32_t cpu;
 172
 173         cpu = rseq_current_cpu_raw();
 174         if (rseq_unlikely(cpu < 0))
 175                 cpu = rseq_fallback_current_cpu();
 176         return cpu;
 177 }
 178
 179 static inline void rseq_clear_rseq_cs(void)
 180 {
 181         RSEQ_WRITE_ONCE(rseq_get_abi()->rseq_cs.arch.ptr, 0);
 182 }
 183
 184 /*
 185  * rseq_prepare_unload() should be invoked by each thread executing a rseq
 186  * critical section at least once between their last critical section and
 187  * library unload of the library defining the rseq critical section
 188  * (struct rseq_ab_cs). This also applies to use of rseq in code generated by
 189  * JIT: rseq_prepare_unload() should be invoked at least once by each
 190  * thread executing a rseq critical section before reclaim of the memory
 191  * holding the struct rseq_abi_cs.
 192  */
 193 static inline void rseq_prepare_unload(void)
 194 {
 195         rseq_clear_rseq_cs();
 196 }
 197
 198 #ifdef __cplusplus
 199 }
 200 #endif
 201
 202 #endif  /* RSEQ_H_ */