LXR linux/tools/testing/selftests/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 <linux/rseq.h>
  20
  21/*
  22 * Empty code injection macros, override when testing.
  23 * It is important to consider that the ASM injection macros need to be
  24 * fully reentrant (e.g. do not modify the stack).
  25 */
  26#ifndef RSEQ_INJECT_ASM
  27#define RSEQ_INJECT_ASM(n)
  28#endif
  29
  30#ifndef RSEQ_INJECT_C
  31#define RSEQ_INJECT_C(n)
  32#endif
  33
  34#ifndef RSEQ_INJECT_INPUT
  35#define RSEQ_INJECT_INPUT
  36#endif
  37
  38#ifndef RSEQ_INJECT_CLOBBER
  39#define RSEQ_INJECT_CLOBBER
  40#endif
  41
  42#ifndef RSEQ_INJECT_FAILED
  43#define RSEQ_INJECT_FAILED
  44#endif
  45
  46extern __thread volatile struct rseq __rseq_abi;
  47extern int __rseq_handled;
  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-x86.h>
  72#elif defined(__ARMEL__)
  73#include <rseq-arm.h>
  74#elif defined (__AARCH64EL__)
  75#include <rseq-arm64.h>
  76#elif defined(__PPC__)
  77#include <rseq-ppc.h>
  78#elif defined(__mips__)
  79#include <rseq-mips.h>
  80#elif defined(__s390__)
  81#include <rseq-s390.h>
  82#else
  83#error unsupported target
  84#endif
  85
  86/*
  87 * Register rseq for the current thread. This needs to be called once
  88 * by any thread which uses restartable sequences, before they start
  89 * using restartable sequences, to ensure restartable sequences
  90 * succeed. A restartable sequence executed from a non-registered
  91 * thread will always fail.
  92 */
  93int rseq_register_current_thread(void);
  94
  95/*
  96 * Unregister rseq for current thread.
  97 */
  98int rseq_unregister_current_thread(void);
  99
 100/*
 101 * Restartable sequence fallback for reading the current CPU number.
 102 */
 103int32_t rseq_fallback_current_cpu(void);
 104
 105/*
 106 * Values returned can be either the current CPU number, -1 (rseq is
 107 * uninitialized), or -2 (rseq initialization has failed).
 108 */
 109static inline int32_t rseq_current_cpu_raw(void)
 110{
 111        return RSEQ_ACCESS_ONCE(__rseq_abi.cpu_id);
 112}
 113
 114/*
 115 * Returns a possible CPU number, which is typically the current CPU.
 116 * The returned CPU number can be used to prepare for an rseq critical
 117 * section, which will confirm whether the cpu number is indeed the
 118 * current one, and whether rseq is initialized.
 119 *
 120 * The CPU number returned by rseq_cpu_start should always be validated
 121 * by passing it to a rseq asm sequence, or by comparing it to the
 122 * return value of rseq_current_cpu_raw() if the rseq asm sequence
 123 * does not need to be invoked.
 124 */
 125static inline uint32_t rseq_cpu_start(void)
 126{
 127        return RSEQ_ACCESS_ONCE(__rseq_abi.cpu_id_start);
 128}
 129
 130static inline uint32_t rseq_current_cpu(void)
 131{
 132        int32_t cpu;
 133
 134        cpu = rseq_current_cpu_raw();
 135        if (rseq_unlikely(cpu < 0))
 136                cpu = rseq_fallback_current_cpu();
 137        return cpu;
 138}
 139
 140static inline void rseq_clear_rseq_cs(void)
 141{
 142#ifdef __LP64__
 143        __rseq_abi.rseq_cs.ptr = 0;
 144#else
 145        __rseq_abi.rseq_cs.ptr.ptr32 = 0;
 146#endif
 147}
 148
 149/*
 150 * rseq_prepare_unload() should be invoked by each thread executing a rseq
 151 * critical section at least once between their last critical section and
 152 * library unload of the library defining the rseq critical section (struct
 153 * rseq_cs) or the code referred to by the struct rseq_cs start_ip and
 154 * post_commit_offset fields. This also applies to use of rseq in code
 155 * generated by JIT: rseq_prepare_unload() should be invoked at least once by
 156 * each thread executing a rseq critical section before reclaim of the memory
 157 * holding the struct rseq_cs or reclaim of the code pointed to by struct
 158 * rseq_cs start_ip and post_commit_offset fields.
 159 */
 160static inline void rseq_prepare_unload(void)
 161{
 162        rseq_clear_rseq_cs();
 163}
 164
 165#endif  /* RSEQ_H_ */
 166