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1/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
2#ifndef _UAPI_LINUX_RSEQ_H
3#define _UAPI_LINUX_RSEQ_H
4
5/*
6 * linux/rseq.h
7 *
8 * Restartable sequences system call API
9 *
10 * Copyright (c) 2015-2018 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
11 */
12
13#ifdef __KERNEL__
14# include <linux/types.h>
15#else
16# include <stdint.h>
17#endif
18
19#include <linux/types_32_64.h>
20
21enum rseq_cpu_id_state {
22 RSEQ_CPU_ID_UNINITIALIZED = -1,
23 RSEQ_CPU_ID_REGISTRATION_FAILED = -2,
24};
25
26enum rseq_flags {
27 RSEQ_FLAG_UNREGISTER = (1 << 0),
28};
29
30enum rseq_cs_flags_bit {
31 RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT = 0,
32 RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT = 1,
33 RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT = 2,
34};
35
36enum rseq_cs_flags {
37 RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT =
38 (1U << RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT),
39 RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL =
40 (1U << RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT),
41 RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE =
42 (1U << RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT),
43};
44
45/*
46 * struct rseq_cs is aligned on 4 * 8 bytes to ensure it is always
47 * contained within a single cache-line. It is usually declared as
48 * link-time constant data.
49 */
50struct rseq_cs {
51 /* Version of this structure. */
52 __u32 version;
53 /* enum rseq_cs_flags */
54 __u32 flags;
55 LINUX_FIELD_u32_u64(start_ip);
56 /* Offset from start_ip. */
57 LINUX_FIELD_u32_u64(post_commit_offset);
58 LINUX_FIELD_u32_u64(abort_ip);
59} __attribute__((aligned(4 * sizeof(__u64))));
60
61/*
62 * struct rseq is aligned on 4 * 8 bytes to ensure it is always
63 * contained within a single cache-line.
64 *
65 * A single struct rseq per thread is allowed.
66 */
67struct rseq {
68 /*
69 * Restartable sequences cpu_id_start field. Updated by the
70 * kernel, and read by user-space with single-copy atomicity
71 * semantics. Aligned on 32-bit. Always contains a value in the
72 * range of possible CPUs, although the value may not be the
73 * actual current CPU (e.g. if rseq is not initialized). This
74 * CPU number value should always be compared against the value
75 * of the cpu_id field before performing a rseq commit or
76 * returning a value read from a data structure indexed using
77 * the cpu_id_start value.
78 */
79 __u32 cpu_id_start;
80 /*
81 * Restartable sequences cpu_id field. Updated by the kernel,
82 * and read by user-space with single-copy atomicity semantics.
83 * Aligned on 32-bit. Values RSEQ_CPU_ID_UNINITIALIZED and
84 * RSEQ_CPU_ID_REGISTRATION_FAILED have a special semantic: the
85 * former means "rseq uninitialized", and latter means "rseq
86 * initialization failed". This value is meant to be read within
87 * rseq critical sections and compared with the cpu_id_start
88 * value previously read, before performing the commit instruction,
89 * or read and compared with the cpu_id_start value before returning
90 * a value loaded from a data structure indexed using the
91 * cpu_id_start value.
92 */
93 __u32 cpu_id;
94 /*
95 * Restartable sequences rseq_cs field.
96 *
97 * Contains NULL when no critical section is active for the current
98 * thread, or holds a pointer to the currently active struct rseq_cs.
99 *
100 * Updated by user-space, which sets the address of the currently
101 * active rseq_cs at the beginning of assembly instruction sequence
102 * block, and set to NULL by the kernel when it restarts an assembly
103 * instruction sequence block, as well as when the kernel detects that
104 * it is preempting or delivering a signal outside of the range
105 * targeted by the rseq_cs. Also needs to be set to NULL by user-space
106 * before reclaiming memory that contains the targeted struct rseq_cs.
107 *
108 * Read and set by the kernel with single-copy atomicity semantics.
109 * Set by user-space with single-copy atomicity semantics. Aligned
110 * on 64-bit.
111 */
112 LINUX_FIELD_u32_u64(rseq_cs);
113 /*
114 * - RSEQ_DISABLE flag:
115 *
116 * Fallback fast-track flag for single-stepping.
117 * Set by user-space if lack of progress is detected.
118 * Cleared by user-space after rseq finish.
119 * Read by the kernel.
120 * - RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT
121 * Inhibit instruction sequence block restart and event
122 * counter increment on preemption for this thread.
123 * - RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL
124 * Inhibit instruction sequence block restart and event
125 * counter increment on signal delivery for this thread.
126 * - RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE
127 * Inhibit instruction sequence block restart and event
128 * counter increment on migration for this thread.
129 */
130 __u32 flags;
131} __attribute__((aligned(4 * sizeof(__u64))));
132
133#endif /* _UAPI_LINUX_RSEQ_H */