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
16 enum rseq_abi_cpu_id_state {
17 RSEQ_ABI_CPU_ID_UNINITIALIZED = -1,
18 RSEQ_ABI_CPU_ID_REGISTRATION_FAILED = -2,
19 };
20
21 enum rseq_abi_flags {
22 RSEQ_ABI_FLAG_UNREGISTER = (1 << 0),
23 };
24
25 enum 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
31 enum 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 */
45 struct 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 * struct rseq_abi is aligned on 4 * 8 bytes to ensure it is always
58 * contained within a single cache-line.
59 *
60 * A single struct rseq_abi per thread is allowed.
61 */
62 struct rseq_abi {
63 /*
64 * Restartable sequences cpu_id_start field. Updated by the
65 * kernel. Read by user-space with single-copy atomicity
66 * semantics. This field should only be read by the thread which
67 * registered this data structure. Aligned on 32-bit. Always
68 * contains a value in the range of possible CPUs, although the
69 * value may not be the actual current CPU (e.g. if rseq is not
70 * initialized). This CPU number value should always be compared
71 * against the value of the cpu_id field before performing a rseq
72 * commit or returning a value read from a data structure indexed
73 * using the cpu_id_start value.
74 */
75 __u32 cpu_id_start;
76 /*
77 * Restartable sequences cpu_id field. Updated by the kernel.
78 * Read by user-space with single-copy atomicity semantics. This
79 * field should only be read by the thread which registered this
80 * data structure. Aligned on 32-bit. Values
81 * RSEQ_CPU_ID_UNINITIALIZED and RSEQ_CPU_ID_REGISTRATION_FAILED
82 * have a special semantic: the former means "rseq uninitialized",
83 * and latter means "rseq initialization failed". This value is
84 * meant to be read within rseq critical sections and compared
85 * with the cpu_id_start value previously read, before performing
86 * the commit instruction, or read and compared with the
87 * cpu_id_start value before returning a value loaded from a data
88 * structure indexed using the cpu_id_start value.
89 */
90 __u32 cpu_id;
91 /*
92 * Restartable sequences rseq_cs field.
93 *
94 * Contains NULL when no critical section is active for the current
95 * thread, or holds a pointer to the currently active struct rseq_cs.
96 *
97 * Updated by user-space, which sets the address of the currently
98 * active rseq_cs at the beginning of assembly instruction sequence
99 * block, and set to NULL by the kernel when it restarts an assembly
100 * instruction sequence block, as well as when the kernel detects that
101 * it is preempting or delivering a signal outside of the range
102 * targeted by the rseq_cs. Also needs to be set to NULL by user-space
103 * before reclaiming memory that contains the targeted struct rseq_cs.
104 *
105 * Read and set by the kernel. Set by user-space with single-copy
106 * atomicity semantics. This field should only be updated by the
107 * thread which registered this data structure. Aligned on 64-bit.
108 */
109 union {
110 __u64 ptr64;
111
112 /*
113 * The "arch" field provides architecture accessor for
114 * the ptr field based on architecture pointer size and
115 * endianness.
116 */
117 struct {
118 #ifdef __LP64__
119 __u64 ptr;
120 #elif defined(__BYTE_ORDER) ? (__BYTE_ORDER == __BIG_ENDIAN) : defined(__BIG_ENDIAN)
121 __u32 padding; /* Initialized to zero. */
122 __u32 ptr;
123 #else
124 __u32 ptr;
125 __u32 padding; /* Initialized to zero. */
126 #endif
127 } arch;
128 } rseq_cs;
129
130 /*
131 * Restartable sequences flags field.
132 *
133 * This field should only be updated by the thread which
134 * registered this data structure. Read by the kernel.
135 * Mainly used for single-stepping through rseq critical sections
136 * with debuggers.
137 *
138 * - RSEQ_ABI_CS_FLAG_NO_RESTART_ON_PREEMPT
139 * Inhibit instruction sequence block restart on preemption
140 * for this thread.
141 * - RSEQ_ABI_CS_FLAG_NO_RESTART_ON_SIGNAL
142 * Inhibit instruction sequence block restart on signal
143 * delivery for this thread.
144 * - RSEQ_ABI_CS_FLAG_NO_RESTART_ON_MIGRATE
145 * Inhibit instruction sequence block restart on migration for
146 * this thread.
147 */
148 __u32 flags;
149
150 /*
151 * Restartable sequences node_id field. Updated by the kernel. Read by
152 * user-space with single-copy atomicity semantics. This field should
153 * only be read by the thread which registered this data structure.
154 * Aligned on 32-bit. Contains the current NUMA node ID.
155 */
156 __u32 node_id;
157
158 /*
159 * Restartable sequences mm_cid field. Updated by the kernel. Read by
160 * user-space with single-copy atomicity semantics. This field should
161 * only be read by the thread which registered this data structure.
162 * Aligned on 32-bit. Contains the current thread's concurrency ID
163 * (allocated uniquely within a memory map).
164 */
165 __u32 mm_cid;
166
167 /*
168 * Flexible array member at end of structure, after last feature field.
169 */
170 char end[];
171 } __attribute__((aligned(4 * sizeof(__u64))));
172
173 #endif /* _RSEQ_ABI_H */
174
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