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Per the rseq syscall documentation, 3 fields are required to be initialized by userspace prior to registration, they are 'cpu_id', 'rseq_cs' and 'flags'. Since we have no guarantee that 'struct pthread' is cleared on all architectures, explicitly set those 3 fields prior to registration. Signed-off-by: Michael Jeanson <mjeanson@efficios.com> Reviewed-by: Florian Weimer <fweimer@redhat.com>
81 lines
2.8 KiB
C
81 lines
2.8 KiB
C
/* Restartable Sequences internal API. Linux implementation.
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Copyright (C) 2021-2024 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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/* 32 is the initially required value for the area size. The
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actually used rseq size may be less (20 bytes initially). */
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#define RSEQ_AREA_SIZE_INITIAL 32
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#define RSEQ_AREA_SIZE_INITIAL_USED 20
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/* The variables are in .data.relro but are not yet write-protected. */
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extern unsigned int _rseq_size attribute_hidden;
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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.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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