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/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
#ifndef _LINUX_RSEQ_H
#define _LINUX_RSEQ_H
/*
* linux/rseq.h
*
* Restartable sequences system call API
*
* Copyright (c) 2015-2018 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
*/
#include <linux/types.h>
#include <asm/byteorder.h>
enum rseq_cpu_id_state {
RSEQ_CPU_ID_UNINITIALIZED = -1,
RSEQ_CPU_ID_REGISTRATION_FAILED = -2,
};
enum rseq_flags {
RSEQ_FLAG_UNREGISTER = (1 << 0),
};
enum rseq_cs_flags_bit {
RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT = 0,
RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT = 1,
RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT = 2,
};
enum rseq_cs_flags {
RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT =
(1U << RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT),
RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL =
(1U << RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT),
RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE =
(1U << RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT),
};
/*
* struct rseq_cs is aligned on 4 * 8 bytes to ensure it is always
* contained within a single cache-line. It is usually declared as
* link-time constant data.
*/
struct rseq_cs {
/* Version of this structure. */
__u32 version;
/* enum rseq_cs_flags */
__u32 flags;
__u64 start_ip;
/* Offset from start_ip. */
__u64 post_commit_offset;
__u64 abort_ip;
} __attribute__((aligned(4 * sizeof(__u64))));
/*
* struct rseq is aligned on 4 * 8 bytes to ensure it is always
* contained within a single cache-line.
*
* A single struct rseq per thread is allowed.
*/
struct rseq {
/*
* Restartable sequences cpu_id_start field. Updated by the
* kernel. Read by user-space with single-copy atomicity
* semantics. This field should only be read by the thread which
* registered this data structure. Aligned on 32-bit. Always
* contains a value in the range of possible CPUs, although the
* value may not be the actual current CPU (e.g. if rseq is not
* initialized). This CPU number value should always be compared
* against the value of the cpu_id field before performing a rseq
* commit or returning a value read from a data structure indexed
* using the cpu_id_start value.
*/
__u32 cpu_id_start;
/*
* Restartable sequences cpu_id field. Updated by the kernel.
* Read by user-space with single-copy atomicity semantics. This
* field should only be read by the thread which registered this
* data structure. Aligned on 32-bit. Values
* RSEQ_CPU_ID_UNINITIALIZED and RSEQ_CPU_ID_REGISTRATION_FAILED
* have a special semantic: the former means "rseq uninitialized",
* and latter means "rseq initialization failed". This value is
* meant to be read within rseq critical sections and compared
* with the cpu_id_start value previously read, before performing
* the commit instruction, or read and compared with the
* cpu_id_start value before returning a value loaded from a data
* structure indexed using the cpu_id_start value.
*/
__u32 cpu_id;
/*
* Restartable sequences rseq_cs field.
*
* Contains NULL when no critical section is active for the current
* thread, or holds a pointer to the currently active struct rseq_cs.
*
* Updated by user-space, which sets the address of the currently
* active rseq_cs at the beginning of assembly instruction sequence
* block, and set to NULL by the kernel when it restarts an assembly
* instruction sequence block, as well as when the kernel detects that
* it is preempting or delivering a signal outside of the range
* targeted by the rseq_cs. Also needs to be set to NULL by user-space
* before reclaiming memory that contains the targeted struct rseq_cs.
*
* Read and set by the kernel. Set by user-space with single-copy
* atomicity semantics. This field should only be updated by the
* thread which registered this data structure. Aligned on 64-bit.
*/
union {
__u64 ptr64;
#ifdef __LP64__
__u64 ptr;
#else
struct {
#if (defined(__BYTE_ORDER) && (__BYTE_ORDER == __BIG_ENDIAN)) || defined(__BIG_ENDIAN)
__u32 padding; /* Initialized to zero. */
__u32 ptr32;
#else /* LITTLE */
__u32 ptr32;
__u32 padding; /* Initialized to zero. */
#endif /* ENDIAN */
} ptr;
#endif
} rseq_cs;
/*
* Restartable sequences flags field.
*
* This field should only be updated by the thread which
* registered this data structure. Read by the kernel.
* Mainly used for single-stepping through rseq critical sections
* with debuggers.
*
* - RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT
* Inhibit instruction sequence block restart on preemption
* for this thread.
* - RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL
* Inhibit instruction sequence block restart on signal
* delivery for this thread.
* - RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE
* Inhibit instruction sequence block restart on migration for
* this thread.
*/
__u32 flags;
} __attribute__((aligned(4 * sizeof(__u64))));
#endif /* _LINUX_RSEQ_H */
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