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/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */

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#ifndef _LINUX_RSEQ_H

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#define _LINUX_RSEQ_H

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* linux/rseq.h

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* Restartable sequences system call API

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#include <linux/types.h>

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#include <asm/byteorder.h>

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enum rseq_cpu_id_state {

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RSEQ_CPU_ID_UNINITIALIZED = -1,

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RSEQ_CPU_ID_REGISTRATION_FAILED = -2,

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};

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enum rseq_flags {

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RSEQ_FLAG_UNREGISTER = (1 << 0),

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};

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enum rseq_cs_flags_bit {

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RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT = 0,

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RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT = 1,

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RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT = 2,

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};

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enum rseq_cs_flags {

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RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT =

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(1U << RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT),

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RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL =

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(1U << RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT),

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RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE =

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(1U << RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT),

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};

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* struct rseq_cs is aligned on 4 * 8 bytes to ensure it is always

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* contained within a single cache-line. It is usually declared as

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* link-time constant data.

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struct rseq_cs {

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/* Version of this structure. */

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__u32 version;

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/* enum rseq_cs_flags */

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__u32 flags;

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__u64 start_ip;

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/* Offset from start_ip. */

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__u64 post_commit_offset;

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__u64 abort_ip;

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} __attribute__((aligned(4 * sizeof(__u64))));

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* struct rseq is aligned on 4 * 8 bytes to ensure it is always

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* contained within a single cache-line.

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* A single struct rseq per thread is allowed.

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struct rseq {

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* Restartable sequences cpu_id_start field. Updated by the

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* kernel. Read by user-space with single-copy atomicity

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* semantics. This field should only be read by the thread which

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* registered this data structure. Aligned on 32-bit. Always

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* contains a value in the range of possible CPUs, although the

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* value may not be the actual current CPU (e.g. if rseq is not

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* initialized). This CPU number value should always be compared

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* against the value of the cpu_id field before performing a rseq

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* commit or returning a value read from a data structure indexed

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* using the cpu_id_start value.

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__u32 cpu_id_start;

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* Restartable sequences cpu_id field. Updated by the kernel.

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* Read by user-space with single-copy atomicity semantics. This

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* field should only be read by the thread which registered this

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* data structure. Aligned on 32-bit. Values

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* RSEQ_CPU_ID_UNINITIALIZED and RSEQ_CPU_ID_REGISTRATION_FAILED

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* have a special semantic: the former means "rseq uninitialized",

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* and latter means "rseq initialization failed". This value is

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* meant to be read within rseq critical sections and compared

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* with the cpu_id_start value previously read, before performing

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* the commit instruction, or read and compared with the

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* cpu_id_start value before returning a value loaded from a data

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* structure indexed using the cpu_id_start value.

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__u32 cpu_id;

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* Restartable sequences rseq_cs field.

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* Contains NULL when no critical section is active for the current

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* thread, or holds a pointer to the currently active struct rseq_cs.

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* Updated by user-space, which sets the address of the currently

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* active rseq_cs at the beginning of assembly instruction sequence

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* block, and set to NULL by the kernel when it restarts an assembly

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* instruction sequence block, as well as when the kernel detects that

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* it is preempting or delivering a signal outside of the range

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* targeted by the rseq_cs. Also needs to be set to NULL by user-space

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* before reclaiming memory that contains the targeted struct rseq_cs.

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* Read and set by the kernel. Set by user-space with single-copy

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* atomicity semantics. This field should only be updated by the

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* thread which registered this data structure. Aligned on 64-bit.

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union {

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__u64 ptr64;

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#ifdef __LP64__

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__u64 ptr;

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#else

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struct {

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#if (defined(__BYTE_ORDER) && (__BYTE_ORDER == __BIG_ENDIAN)) || defined(__BIG_ENDIAN)

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__u32 padding; /* Initialized to zero. */

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__u32 ptr32;

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#else /* LITTLE */

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__u32 ptr32;

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__u32 padding; /* Initialized to zero. */

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#endif /* ENDIAN */

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} ptr;

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#endif

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} rseq_cs;

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* Restartable sequences flags field.

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* This field should only be updated by the thread which

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* registered this data structure. Read by the kernel.

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* Mainly used for single-stepping through rseq critical sections

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* with debuggers.

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* - RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT

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* Inhibit instruction sequence block restart on preemption

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* for this thread.

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* - RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL

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* Inhibit instruction sequence block restart on signal

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* delivery for this thread.

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* - RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE

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* Inhibit instruction sequence block restart on migration for

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* this thread.

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__u32 flags;

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} __attribute__((aligned(4 * sizeof(__u64))));

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#endif /* _LINUX_RSEQ_H */

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