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