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/* Restartable Sequences internal API. Linux implementation.
Copyright (C) 2021-2025 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 RSEQ_INTERNAL_H
#define RSEQ_INTERNAL_H
#include <sysdep.h>
#include <errno.h>
#include <kernel-features.h>
#include <stdbool.h>
#include <stdio.h>
#include <sys/rseq.h>
#include <ldsodefs.h>
/* Minimum size of the rseq area allocation required by the syscall. The
actually used rseq feature size may be less (20 bytes initially). */
#define RSEQ_AREA_SIZE_INITIAL 32
/* Minimum used feature size of the rseq area. */
#define RSEQ_AREA_SIZE_INITIAL_USED 20
/* Maximum currently used feature size of the rseq area. */
#define RSEQ_AREA_SIZE_MAX_USED 28
/* Minimum alignment of the rseq area. */
#define RSEQ_MIN_ALIGN 32
/* Alignment requirement of the rseq area.
Populated from the auxiliary vector with a minimum of '32'.
In .data.relro but not yet write-protected. */
extern size_t _rseq_align attribute_hidden;
/* Size of the active features in the rseq area.
Populated from the auxiliary vector with a minimum of '20'.
In .data.relro but not yet write-protected. */
extern unsigned int _rseq_size attribute_hidden;
/* Offset from the thread pointer to the rseq area.
In .data.relro but not yet write-protected. */
extern ptrdiff_t _rseq_offset attribute_hidden;
/* We want to use rtld_hidden_proto in order to call the internal aliases
of __rseq_size and __rseq_offset from ld.so. This avoids dynamic symbol
binding at run time for both variables. */
rtld_hidden_proto (__rseq_size)
rtld_hidden_proto (__rseq_offset)
#ifdef RSEQ_SIG
static inline bool
rseq_register_current_thread (struct pthread *self, bool do_rseq)
{
if (do_rseq)
{
unsigned int size = __rseq_size;
if (size < RSEQ_AREA_SIZE_INITIAL)
/* The initial implementation used only 20 bytes out of 32,
but still expected size 32. */
size = RSEQ_AREA_SIZE_INITIAL;
/* Initialize the rseq fields that are read by the kernel on
registration, there is no guarantee that struct pthread is
cleared on all architectures. */
THREAD_SETMEM (self, rseq_area.cpu_id, RSEQ_CPU_ID_UNINITIALIZED);
THREAD_SETMEM (self, rseq_area.cpu_id_start, 0);
THREAD_SETMEM (self, rseq_area.rseq_cs, 0);
THREAD_SETMEM (self, rseq_area.flags, 0);
int ret = INTERNAL_SYSCALL_CALL (rseq, &self->rseq_area,
size, 0, RSEQ_SIG);
if (!INTERNAL_SYSCALL_ERROR_P (ret))
return true;
}
/* When rseq is disabled by tunables or the registration fails, inform
userspace by setting 'cpu_id' to RSEQ_CPU_ID_REGISTRATION_FAILED. */
THREAD_SETMEM (self, rseq_area.cpu_id, RSEQ_CPU_ID_REGISTRATION_FAILED);
return false;
}
#else /* RSEQ_SIG */
static inline bool
rseq_register_current_thread (struct pthread *self, bool do_rseq)
{
THREAD_SETMEM (self, rseq_area.cpu_id, RSEQ_CPU_ID_REGISTRATION_FAILED);
return false;
}
#endif /* RSEQ_SIG */
#endif /* rseq-internal.h */
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