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