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c813c1490d
Get the rseq feature size and alignment requirement from the auxiliary vector for use inside the dynamic loader. Use '__rseq_size' directly to store the feature size. If the main thread registration fails or is disabled by tunable, reset the value to 0. This will be used in the TLS block allocator to compute the size and alignment of the rseq area block for the extended ABI support. Signed-off-by: Michael Jeanson <mjeanson@efficios.com> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Reviewed-by: Florian Weimer <fweimer@redhat.com>
100 lines
3.5 KiB
C
100 lines
3.5 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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/* 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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#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;
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#if IS_IN (rtld)
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/* Use the hidden symbol in ld.so. */
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size = _rseq_size;
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#else
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size = __rseq_size;
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#endif
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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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