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1/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
2#ifndef _RSEQ_ABI_H
3#define _RSEQ_ABI_H
4
5/*
6 * rseq-abi.h
7 *
8 * Restartable sequences system call API
9 *
10 * Copyright (c) 2015-2022 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
11 */
12
13#include <linux/types.h>
14#include <asm/byteorder.h>
15
16enum rseq_abi_cpu_id_state {
17 RSEQ_ABI_CPU_ID_UNINITIALIZED = -1,
18 RSEQ_ABI_CPU_ID_REGISTRATION_FAILED = -2,
19};
20
21enum rseq_abi_flags {
22 RSEQ_ABI_FLAG_UNREGISTER = (1 << 0),
23};
24
25enum rseq_abi_cs_flags_bit {
26 RSEQ_ABI_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT = 0,
27 RSEQ_ABI_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT = 1,
28 RSEQ_ABI_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT = 2,
29};
30
31enum rseq_abi_cs_flags {
32 RSEQ_ABI_CS_FLAG_NO_RESTART_ON_PREEMPT =
33 (1U << RSEQ_ABI_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT),
34 RSEQ_ABI_CS_FLAG_NO_RESTART_ON_SIGNAL =
35 (1U << RSEQ_ABI_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT),
36 RSEQ_ABI_CS_FLAG_NO_RESTART_ON_MIGRATE =
37 (1U << RSEQ_ABI_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT),
38};
39
40/*
41 * struct rseq_abi_cs is aligned on 4 * 8 bytes to ensure it is always
42 * contained within a single cache-line. It is usually declared as
43 * link-time constant data.
44 */
45struct rseq_abi_cs {
46 /* Version of this structure. */
47 __u32 version;
48 /* enum rseq_abi_cs_flags */
49 __u32 flags;
50 __u64 start_ip;
51 /* Offset from start_ip. */
52 __u64 post_commit_offset;
53 __u64 abort_ip;
54} __attribute__((aligned(4 * sizeof(__u64))));
55
56/**
57 * rseq_abi_slice_ctrl - Time slice extension control structure
58 * @all: Compound value
59 * @request: Request for a time slice extension
60 * @granted: Granted time slice extension
61 *
62 * @request is set by user space and can be cleared by user space or kernel
63 * space. @granted is set and cleared by the kernel and must only be read
64 * by user space.
65 */
66struct rseq_abi_slice_ctrl {
67 union {
68 __u32 all;
69 struct {
70 __u8 request;
71 __u8 granted;
72 __u16 __reserved;
73 };
74 };
75};
76
77/*
78 * struct rseq_abi is aligned on 4 * 8 bytes to ensure it is always
79 * contained within a single cache-line.
80 *
81 * A single struct rseq_abi per thread is allowed.
82 */
83struct rseq_abi {
84 /*
85 * Restartable sequences cpu_id_start field. Updated by the
86 * kernel. Read by user-space with single-copy atomicity
87 * semantics. This field should only be read by the thread which
88 * registered this data structure. Aligned on 32-bit. Always
89 * contains a value in the range of possible CPUs, although the
90 * value may not be the actual current CPU (e.g. if rseq is not
91 * initialized). This CPU number value should always be compared
92 * against the value of the cpu_id field before performing a rseq
93 * commit or returning a value read from a data structure indexed
94 * using the cpu_id_start value.
95 */
96 __u32 cpu_id_start;
97 /*
98 * Restartable sequences cpu_id field. Updated by the kernel.
99 * Read by user-space with single-copy atomicity semantics. This
100 * field should only be read by the thread which registered this
101 * data structure. Aligned on 32-bit. Values
102 * RSEQ_CPU_ID_UNINITIALIZED and RSEQ_CPU_ID_REGISTRATION_FAILED
103 * have a special semantic: the former means "rseq uninitialized",
104 * and latter means "rseq initialization failed". This value is
105 * meant to be read within rseq critical sections and compared
106 * with the cpu_id_start value previously read, before performing
107 * the commit instruction, or read and compared with the
108 * cpu_id_start value before returning a value loaded from a data
109 * structure indexed using the cpu_id_start value.
110 */
111 __u32 cpu_id;
112 /*
113 * Restartable sequences rseq_cs field.
114 *
115 * Contains NULL when no critical section is active for the current
116 * thread, or holds a pointer to the currently active struct rseq_cs.
117 *
118 * Updated by user-space, which sets the address of the currently
119 * active rseq_cs at the beginning of assembly instruction sequence
120 * block, and set to NULL by the kernel when it restarts an assembly
121 * instruction sequence block, as well as when the kernel detects that
122 * it is preempting or delivering a signal outside of the range
123 * targeted by the rseq_cs. Also needs to be set to NULL by user-space
124 * before reclaiming memory that contains the targeted struct rseq_cs.
125 *
126 * Read and set by the kernel. Set by user-space with single-copy
127 * atomicity semantics. This field should only be updated by the
128 * thread which registered this data structure. Aligned on 64-bit.
129 */
130 union {
131 __u64 ptr64;
132
133 /*
134 * The "arch" field provides architecture accessor for
135 * the ptr field based on architecture pointer size and
136 * endianness.
137 */
138 struct {
139#ifdef __LP64__
140 __u64 ptr;
141#elif defined(__BYTE_ORDER) ? (__BYTE_ORDER == __BIG_ENDIAN) : defined(__BIG_ENDIAN)
142 __u32 padding; /* Initialized to zero. */
143 __u32 ptr;
144#else
145 __u32 ptr;
146 __u32 padding; /* Initialized to zero. */
147#endif
148 } arch;
149 } rseq_cs;
150
151 /*
152 * Restartable sequences flags field.
153 *
154 * This field should only be updated by the thread which
155 * registered this data structure. Read by the kernel.
156 * Mainly used for single-stepping through rseq critical sections
157 * with debuggers.
158 *
159 * - RSEQ_ABI_CS_FLAG_NO_RESTART_ON_PREEMPT
160 * Inhibit instruction sequence block restart on preemption
161 * for this thread.
162 * - RSEQ_ABI_CS_FLAG_NO_RESTART_ON_SIGNAL
163 * Inhibit instruction sequence block restart on signal
164 * delivery for this thread.
165 * - RSEQ_ABI_CS_FLAG_NO_RESTART_ON_MIGRATE
166 * Inhibit instruction sequence block restart on migration for
167 * this thread.
168 */
169 __u32 flags;
170
171 /*
172 * Restartable sequences node_id field. Updated by the kernel. Read by
173 * user-space with single-copy atomicity semantics. This field should
174 * only be read by the thread which registered this data structure.
175 * Aligned on 32-bit. Contains the current NUMA node ID.
176 */
177 __u32 node_id;
178
179 /*
180 * Restartable sequences mm_cid field. Updated by the kernel. Read by
181 * user-space with single-copy atomicity semantics. This field should
182 * only be read by the thread which registered this data structure.
183 * Aligned on 32-bit. Contains the current thread's concurrency ID
184 * (allocated uniquely within a memory map).
185 */
186 __u32 mm_cid;
187
188 /*
189 * Time slice extension control structure. CPU local updates from
190 * kernel and user space.
191 */
192 struct rseq_abi_slice_ctrl slice_ctrl;
193
194 /*
195 * Flexible array member at end of structure, after last feature field.
196 */
197 char end[];
198} __attribute__((aligned(4 * sizeof(__u64))));
199
200#endif /* _RSEQ_ABI_H */