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 <[email protected]> 11 */ 12 13 #ifdef __KERNEL__ 14 # include <linux/types.h> 15 #else 16 # include <stdint.h> 17 #endif 18 19 #include <linux/types_32_64.h> 20 21 enum rseq_cpu_id_state { 22 RSEQ_CPU_ID_UNINITIALIZED = -1, 23 RSEQ_CPU_ID_REGISTRATION_FAILED = -2, 24 }; 25 26 enum rseq_flags { 27 RSEQ_FLAG_UNREGISTER = (1 << 0), 28 }; 29 30 enum rseq_cs_flags_bit { 31 RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT = 0, 32 RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT = 1, 33 RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT = 2, 34 }; 35 36 enum rseq_cs_flags { 37 RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT = 38 (1U << RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT), 39 RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL = 40 (1U << RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT), 41 RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE = 42 (1U << RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT), 43 }; 44 45 /* 46 * struct rseq_cs is aligned on 4 * 8 bytes to ensure it is always 47 * contained within a single cache-line. It is usually declared as 48 * link-time constant data. 49 */ 50 struct rseq_cs { 51 /* Version of this structure. */ 52 __u32 version; 53 /* enum rseq_cs_flags */ 54 __u32 flags; 55 __u64 start_ip; 56 /* Offset from start_ip. */ 57 __u64 post_commit_offset; 58 __u64 abort_ip; 59 } __attribute__((aligned(4 * sizeof(__u64)))); 60 61 /* 62 * struct rseq is aligned on 4 * 8 bytes to ensure it is always 63 * contained within a single cache-line. 64 * 65 * A single struct rseq per thread is allowed. 66 */ 67 struct rseq { 68 /* 69 * Restartable sequences cpu_id_start field. Updated by the 70 * kernel. Read by user-space with single-copy atomicity 71 * semantics. This field should only be read by the thread which 72 * registered this data structure. Aligned on 32-bit. Always 73 * contains a value in the range of possible CPUs, although the 74 * value may not be the actual current CPU (e.g. if rseq is not 75 * initialized). This CPU number value should always be compared 76 * against the value of the cpu_id field before performing a rseq 77 * commit or returning a value read from a data structure indexed 78 * using the cpu_id_start value. 79 */ 80 __u32 cpu_id_start; 81 /* 82 * Restartable sequences cpu_id field. Updated by the kernel. 83 * Read by user-space with single-copy atomicity semantics. This 84 * field should only be read by the thread which registered this 85 * data structure. Aligned on 32-bit. Values 86 * RSEQ_CPU_ID_UNINITIALIZED and RSEQ_CPU_ID_REGISTRATION_FAILED 87 * have a special semantic: the former means "rseq uninitialized", 88 * and latter means "rseq initialization failed". This value is 89 * meant to be read within rseq critical sections and compared 90 * with the cpu_id_start value previously read, before performing 91 * the commit instruction, or read and compared with the 92 * cpu_id_start value before returning a value loaded from a data 93 * structure indexed using the cpu_id_start value. 94 */ 95 __u32 cpu_id; 96 /* 97 * Restartable sequences rseq_cs field. 98 * 99 * Contains NULL when no critical section is active for the current 100 * thread, or holds a pointer to the currently active struct rseq_cs. 101 * 102 * Updated by user-space, which sets the address of the currently 103 * active rseq_cs at the beginning of assembly instruction sequence 104 * block, and set to NULL by the kernel when it restarts an assembly 105 * instruction sequence block, as well as when the kernel detects that 106 * it is preempting or delivering a signal outside of the range 107 * targeted by the rseq_cs. Also needs to be set to NULL by user-space 108 * before reclaiming memory that contains the targeted struct rseq_cs. 109 * 110 * Read and set by the kernel. Set by user-space with single-copy 111 * atomicity semantics. This field should only be updated by the 112 * thread which registered this data structure. Aligned on 64-bit. 113 */ 114 LINUX_FIELD_u32_u64(rseq_cs); 115 /* 116 * Restartable sequences flags field. 117 * 118 * This field should only be updated by the thread which 119 * registered this data structure. Read by the kernel. 120 * Mainly used for single-stepping through rseq critical sections 121 * with debuggers. 122 * 123 * - RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT 124 * Inhibit instruction sequence block restart on preemption 125 * for this thread. 126 * - RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL 127 * Inhibit instruction sequence block restart on signal 128 * delivery for this thread. 129 * - RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE 130 * Inhibit instruction sequence block restart on migration for 131 * this thread. 132 */ 133 __u32 flags; 134 } __attribute__((aligned(4 * sizeof(__u64)))); 135 136 #endif /* _UAPI_LINUX_RSEQ_H */ 137