uapi/linux/rseq.h

0001 /* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
0002 #ifndef _UAPI_LINUX_RSEQ_H
0003 #define _UAPI_LINUX_RSEQ_H
0004
0005 /*
0006  * linux/rseq.h
0007  *
0008  * Restartable sequences system call API
0009  *
0010  * Copyright (c) 2015-2018 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
0011  */
0012
0013 #include <linux/types.h>
0014 #include <asm/byteorder.h>
0015
0016 enum rseq_cpu_id_state {
0017     RSEQ_CPU_ID_UNINITIALIZED       = -1,
0018     RSEQ_CPU_ID_REGISTRATION_FAILED     = -2,
0019 };
0020
0021 enum rseq_flags {
0022     RSEQ_FLAG_UNREGISTER = (1 << 0),
0023 };
0024
0025 enum rseq_cs_flags_bit {
0026     RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT  = 0,
0027     RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT   = 1,
0028     RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT  = 2,
0029 };
0030
0031 enum rseq_cs_flags {
0032     RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT  =
0033         (1U << RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT),
0034     RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL   =
0035         (1U << RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT),
0036     RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE  =
0037         (1U << RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT),
0038 };
0039
0040 /*
0041  * struct rseq_cs is aligned on 4 * 8 bytes to ensure it is always
0042  * contained within a single cache-line. It is usually declared as
0043  * link-time constant data.
0044  */
0045 struct rseq_cs {
0046     /* Version of this structure. */
0047     __u32 version;
0048     /* enum rseq_cs_flags */
0049     __u32 flags;
0050     __u64 start_ip;
0051     /* Offset from start_ip. */
0052     __u64 post_commit_offset;
0053     __u64 abort_ip;
0054 } __attribute__((aligned(4 * sizeof(__u64))));
0055
0056 /*
0057  * struct rseq is aligned on 4 * 8 bytes to ensure it is always
0058  * contained within a single cache-line.
0059  *
0060  * A single struct rseq per thread is allowed.
0061  */
0062 struct rseq {
0063     /*
0064      * Restartable sequences cpu_id_start field. Updated by the
0065      * kernel. Read by user-space with single-copy atomicity
0066      * semantics. This field should only be read by the thread which
0067      * registered this data structure. Aligned on 32-bit. Always
0068      * contains a value in the range of possible CPUs, although the
0069      * value may not be the actual current CPU (e.g. if rseq is not
0070      * initialized). This CPU number value should always be compared
0071      * against the value of the cpu_id field before performing a rseq
0072      * commit or returning a value read from a data structure indexed
0073      * using the cpu_id_start value.
0074      */
0075     __u32 cpu_id_start;
0076     /*
0077      * Restartable sequences cpu_id field. Updated by the kernel.
0078      * Read by user-space with single-copy atomicity semantics. This
0079      * field should only be read by the thread which registered this
0080      * data structure. Aligned on 32-bit. Values
0081      * RSEQ_CPU_ID_UNINITIALIZED and RSEQ_CPU_ID_REGISTRATION_FAILED
0082      * have a special semantic: the former means "rseq uninitialized",
0083      * and latter means "rseq initialization failed". This value is
0084      * meant to be read within rseq critical sections and compared
0085      * with the cpu_id_start value previously read, before performing
0086      * the commit instruction, or read and compared with the
0087      * cpu_id_start value before returning a value loaded from a data
0088      * structure indexed using the cpu_id_start value.
0089      */
0090     __u32 cpu_id;
0091     /*
0092      * Restartable sequences rseq_cs field.
0093      *
0094      * Contains NULL when no critical section is active for the current
0095      * thread, or holds a pointer to the currently active struct rseq_cs.
0096      *
0097      * Updated by user-space, which sets the address of the currently
0098      * active rseq_cs at the beginning of assembly instruction sequence
0099      * block, and set to NULL by the kernel when it restarts an assembly
0100      * instruction sequence block, as well as when the kernel detects that
0101      * it is preempting or delivering a signal outside of the range
0102      * targeted by the rseq_cs. Also needs to be set to NULL by user-space
0103      * before reclaiming memory that contains the targeted struct rseq_cs.
0104      *
0105      * Read and set by the kernel. Set by user-space with single-copy
0106      * atomicity semantics. This field should only be updated by the
0107      * thread which registered this data structure. Aligned on 64-bit.
0108      *
0109      * 32-bit architectures should update the low order bits of the
0110      * rseq_cs field, leaving the high order bits initialized to 0.
0111      */
0112     __u64 rseq_cs;
0113
0114     /*
0115      * Restartable sequences flags field.
0116      *
0117      * This field should only be updated by the thread which
0118      * registered this data structure. Read by the kernel.
0119      * Mainly used for single-stepping through rseq critical sections
0120      * with debuggers.
0121      *
0122      * - RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT
0123      *     Inhibit instruction sequence block restart on preemption
0124      *     for this thread.
0125      * - RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL
0126      *     Inhibit instruction sequence block restart on signal
0127      *     delivery for this thread.
0128      * - RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE
0129      *     Inhibit instruction sequence block restart on migration for
0130      *     this thread.
0131      */
0132     __u32 flags;
0133 } __attribute__((aligned(4 * sizeof(__u64))));
0134
0135 #endif /* _UAPI_LINUX_RSEQ_H */