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 <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
  47extern __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-x86.h>
  72#elif defined(__ARMEL__)
  73#include <rseq-arm.h>
  74#elif defined(__PPC__)
  75#include <rseq-ppc.h>
  76#elif defined(__mips__)
  77#include <rseq-mips.h>
  78#else
  79#error unsupported target
  80#endif
  81
  82/*
  83 * Register rseq for the current thread. This needs to be called once
  84 * by any thread which uses restartable sequences, before they start
  85 * using restartable sequences, to ensure restartable sequences
  86 * succeed. A restartable sequence executed from a non-registered
  87 * thread will always fail.
  88 */
  89int rseq_register_current_thread(void);
  90
  91/*
  92 * Unregister rseq for current thread.
  93 */
  94int rseq_unregister_current_thread(void);
  95
  96/*
  97 * Restartable sequence fallback for reading the current CPU number.
  98 */
  99int32_t rseq_fallback_current_cpu(void);
 100
 101/*
 102 * Values returned can be either the current CPU number, -1 (rseq is
 103 * uninitialized), or -2 (rseq initialization has failed).
 104 */
 105static inline int32_t rseq_current_cpu_raw(void)
 106{
 107        return RSEQ_ACCESS_ONCE(__rseq_abi.cpu_id);
 108}
 109
 110/*
 111 * Returns a possible CPU number, which is typically the current CPU.
 112 * The returned CPU number can be used to prepare for an rseq critical
 113 * section, which will confirm whether the cpu number is indeed the
 114 * current one, and whether rseq is initialized.
 115 *
 116 * The CPU number returned by rseq_cpu_start should always be validated
 117 * by passing it to a rseq asm sequence, or by comparing it to the
 118 * return value of rseq_current_cpu_raw() if the rseq asm sequence
 119 * does not need to be invoked.
 120 */
 121static inline uint32_t rseq_cpu_start(void)
 122{
 123        return RSEQ_ACCESS_ONCE(__rseq_abi.cpu_id_start);
 124}
 125
 126static inline uint32_t rseq_current_cpu(void)
 127{
 128        int32_t cpu;
 129
 130        cpu = rseq_current_cpu_raw();
 131        if (rseq_unlikely(cpu < 0))
 132                cpu = rseq_fallback_current_cpu();
 133        return cpu;
 134}
 135
 136static inline void rseq_clear_rseq_cs(void)
 137{
 138#ifdef __LP64__
 139        __rseq_abi.rseq_cs.ptr = 0;
 140#else
 141        __rseq_abi.rseq_cs.ptr.ptr32 = 0;
 142#endif
 143}
 144
 145/*
 146 * rseq_prepare_unload() should be invoked by each thread executing a rseq
 147 * critical section at least once between their last critical section and
 148 * library unload of the library defining the rseq critical section
 149 * (struct rseq_cs). This also applies to use of rseq in code generated by
 150 * JIT: rseq_prepare_unload() should be invoked at least once by each
 151 * thread executing a rseq critical section before reclaim of the memory
 152 * holding the struct rseq_cs.
 153 */
 154static inline void rseq_prepare_unload(void)
 155{
 156        rseq_clear_rseq_cs();
 157}
 158
 159#endif  /* RSEQ_H_ */
 160