1 | /* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */ |
2 | #ifndef _LINUX_RSEQ_H |
3 | #define _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 | #include <linux/types.h> |
14 | #include <asm/byteorder.h> |
15 | |
16 | enum rseq_cpu_id_state { |
17 | RSEQ_CPU_ID_UNINITIALIZED = -1, |
18 | RSEQ_CPU_ID_REGISTRATION_FAILED = -2, |
19 | }; |
20 | |
21 | enum rseq_flags { |
22 | RSEQ_FLAG_UNREGISTER = (1 << 0), |
23 | }; |
24 | |
25 | enum rseq_cs_flags_bit { |
26 | RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT = 0, |
27 | RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT = 1, |
28 | RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT = 2, |
29 | }; |
30 | |
31 | enum rseq_cs_flags { |
32 | RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT = |
33 | (1U << RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT), |
34 | RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL = |
35 | (1U << RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT), |
36 | RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE = |
37 | (1U << RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT), |
38 | }; |
39 | |
40 | /* |
41 | * struct rseq_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_cs { |
46 | /* Version of this structure. */ |
47 | __u32 version; |
48 | /* enum rseq_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 is aligned on 4 * 8 bytes to ensure it is always |
58 | * contained within a single cache-line. |
59 | * |
60 | * A single struct rseq per thread is allowed. |
61 | */ |
62 | struct rseq { |
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 | * 32-bit architectures should update the low order bits of the |
110 | * rseq_cs field, leaving the high order bits initialized to 0. |
111 | */ |
112 | __u64 rseq_cs; |
113 | |
114 | /* |
115 | * Restartable sequences flags field. |
116 | * |
117 | * This field should only be updated by the thread which |
118 | * registered this data structure. Read by the kernel. |
119 | * Mainly used for single-stepping through rseq critical sections |
120 | * with debuggers. |
121 | * |
122 | * - RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT |
123 | * Inhibit instruction sequence block restart on preemption |
124 | * for this thread. |
125 | * - RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL |
126 | * Inhibit instruction sequence block restart on signal |
127 | * delivery for this thread. |
128 | * - RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE |
129 | * Inhibit instruction sequence block restart on migration for |
130 | * this thread. |
131 | */ |
132 | __u32 flags; |
133 | } __attribute__((aligned(4 * sizeof(__u64)))); |
134 | |
135 | #endif /* _LINUX_RSEQ_H */ |
136 | |