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494d65129e
In preparation to move the rseq area to the 'extra TLS' block, we need accessors based on the thread pointer and the rseq offset. The ONCE variant of the accessors ensures single-copy atomicity for loads and stores which is required for all fields once the registration is active. A separate header is required to allow including <atomic.h> which results in an include loop when added to <tcb-access.h>. Signed-off-by: Michael Jeanson <mjeanson@efficios.com> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Reviewed-by: Florian Weimer <fweimer@redhat.com>
110 lines
3.9 KiB
C
110 lines
3.9 KiB
C
/* Restartable Sequences internal API. Linux implementation.
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Copyright (C) 2021-2025 Free Software Foundation, Inc.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef RSEQ_INTERNAL_H
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#define RSEQ_INTERNAL_H
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#include <sysdep.h>
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#include <errno.h>
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#include <kernel-features.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <sys/rseq.h>
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#include <ldsodefs.h>
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#include <thread_pointer.h>
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/* Minimum size of the rseq area allocation required by the syscall. The
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actually used rseq feature size may be less (20 bytes initially). */
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#define RSEQ_AREA_SIZE_INITIAL 32
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/* Minimum used feature size of the rseq area. */
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#define RSEQ_AREA_SIZE_INITIAL_USED 20
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/* Maximum currently used feature size of the rseq area. */
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#define RSEQ_AREA_SIZE_MAX_USED 28
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/* Minimum alignment of the rseq area. */
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#define RSEQ_MIN_ALIGN 32
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/* Alignment requirement of the rseq area.
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Populated from the auxiliary vector with a minimum of '32'.
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In .data.relro but not yet write-protected. */
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extern size_t _rseq_align attribute_hidden;
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/* Size of the active features in the rseq area.
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Populated from the auxiliary vector with a minimum of '20'.
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In .data.relro but not yet write-protected. */
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extern unsigned int _rseq_size attribute_hidden;
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/* Offset from the thread pointer to the rseq area.
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In .data.relro but not yet write-protected. */
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extern ptrdiff_t _rseq_offset attribute_hidden;
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/* We want to use rtld_hidden_proto in order to call the internal aliases
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of __rseq_size and __rseq_offset from ld.so. This avoids dynamic symbol
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binding at run time for both variables. */
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rtld_hidden_proto (__rseq_size)
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rtld_hidden_proto (__rseq_offset)
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/* Returns a pointer to the current thread rseq area. */
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static inline struct rseq_area *
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RSEQ_SELF (void)
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{
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return (struct rseq_area *) ((char *) __thread_pointer () + __rseq_offset);
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}
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#ifdef RSEQ_SIG
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static inline bool
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rseq_register_current_thread (struct pthread *self, bool do_rseq)
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{
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if (do_rseq)
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{
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unsigned int size = __rseq_size;
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if (size < RSEQ_AREA_SIZE_INITIAL)
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/* The initial implementation used only 20 bytes out of 32,
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but still expected size 32. */
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size = RSEQ_AREA_SIZE_INITIAL;
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/* Initialize the rseq fields that are read by the kernel on
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registration, there is no guarantee that struct pthread is
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cleared on all architectures. */
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THREAD_SETMEM (self, rseq_area.cpu_id, RSEQ_CPU_ID_UNINITIALIZED);
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THREAD_SETMEM (self, rseq_area.cpu_id_start, 0);
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THREAD_SETMEM (self, rseq_area.rseq_cs, 0);
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THREAD_SETMEM (self, rseq_area.flags, 0);
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int ret = INTERNAL_SYSCALL_CALL (rseq, &self->rseq_area,
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size, 0, RSEQ_SIG);
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if (!INTERNAL_SYSCALL_ERROR_P (ret))
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return true;
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}
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/* When rseq is disabled by tunables or the registration fails, inform
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userspace by setting 'cpu_id' to RSEQ_CPU_ID_REGISTRATION_FAILED. */
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THREAD_SETMEM (self, rseq_area.cpu_id, RSEQ_CPU_ID_REGISTRATION_FAILED);
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return false;
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}
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#else /* RSEQ_SIG */
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static inline bool
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rseq_register_current_thread (struct pthread *self, bool do_rseq)
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{
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THREAD_SETMEM (self, rseq_area.cpu_id, RSEQ_CPU_ID_REGISTRATION_FAILED);
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return false;
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}
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#endif /* RSEQ_SIG */
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#endif /* rseq-internal.h */
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