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 #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 union { 110 __u64 ptr64; 111 #ifdef __LP64__ 112 __u64 ptr; 113 #else 114 struct { 115 #if (defined(__BYTE_ORDER) && (__BYTE_ORDER == __BIG_ENDIAN)) || defined(__BIG_ENDIAN) 116 __u32 padding; /* Initialized to zero. */ 117 __u32 ptr32; 118 #else /* LITTLE */ 119 __u32 ptr32; 120 __u32 padding; /* Initialized to zero. */ 121 #endif /* ENDIAN */ 122 } ptr; 123 #endif 124 } rseq_cs; 125 126 /* 127 * Restartable sequences flags field. 128 * 129 * This field should only be updated by the thread which 130 * registered this data structure. Read by the kernel. 131 * Mainly used for single-stepping through rseq critical sections 132 * with debuggers. 133 * 134 * - RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT 135 * Inhibit instruction sequence block restart on preemption 136 * for this thread. 137 * - RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL 138 * Inhibit instruction sequence block restart on signal 139 * delivery for this thread. 140 * - RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE 141 * Inhibit instruction sequence block restart on migration for 142 * this thread. 143 */ 144 __u32 flags; 145 } __attribute__((aligned(4 * sizeof(__u64)))); 146 147 #endif /* _UAPI_LINUX_RSEQ_H */ 148