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/* Restartable Sequences exported symbols. Linux header.
Copyright (C) 2021-2024 Free Software Foundation, Inc.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#ifndef _SYS_RSEQ_H
#define _SYS_RSEQ_H 1
/* Architecture-specific rseq signature. */
#include <bits/rseq.h>
#include <stddef.h>
#include <stdint.h>
#include <sys/cdefs.h>
#ifdef __has_include
# if __has_include ("linux/rseq.h")
# define __GLIBC_HAVE_KERNEL_RSEQ
# endif
#else
# include <linux/version.h>
# if LINUX_VERSION_CODE >= KERNEL_VERSION (4, 18, 0)
# define __GLIBC_HAVE_KERNEL_RSEQ
# endif
#endif
#ifdef __GLIBC_HAVE_KERNEL_RSEQ
/* We use the structures declarations from the kernel headers. */
# include <linux/rseq.h>
#else /* __GLIBC_HAVE_KERNEL_RSEQ */
/* We use a copy of the include/uapi/linux/rseq.h kernel header. */
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 32 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. */
uint32_t version;
/* enum rseq_cs_flags. */
uint32_t flags;
uint64_t start_ip;
/* Offset from start_ip. */
uint64_t post_commit_offset;
uint64_t abort_ip;
} __attribute__ ((__aligned__ (32)));
/* struct rseq is aligned on 32 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. */
uint32_t 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. */
uint32_t 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.
32-bit architectures should update the low order bits of the
rseq_cs field, leaving the high order bits initialized to 0. */
uint64_t 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. */
uint32_t flags;
} __attribute__ ((__aligned__ (32)));
#endif /* __GLIBC_HAVE_KERNEL_RSEQ */
/* Offset from the thread pointer to the rseq area. */
extern const ptrdiff_t __rseq_offset;
/* Size of the registered rseq area. 0 if the registration was
unsuccessful. */
extern const unsigned int __rseq_size;
/* Flags used during rseq registration. */
extern const unsigned int __rseq_flags;
#endif /* sys/rseq.h */
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