mirror of git://sourceware.org/git/glibc.git
138 lines
4.7 KiB
C
138 lines
4.7 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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#include <rseq-access.h>
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/* rseq area registered with the kernel. Use a custom definition here to
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isolate from the system provided header which could lack some fields of the
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Extended ABI.
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This is only used to get the field offsets and sizes, it should never be
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used for direct object allocations.
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Access to fields of the Extended ABI beyond the 20 bytes of the original ABI
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(after 'flags') must be gated by a check of the feature size. */
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struct rseq_area
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{
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/* Original ABI. */
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uint32_t cpu_id_start;
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uint32_t cpu_id;
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uint64_t rseq_cs;
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uint32_t flags;
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/* Extended ABI. */
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uint32_t node_id;
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uint32_t mm_cid;
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/* Flexible array member to discourage direct object allocations. */
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char end[];
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};
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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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Set to '0' on registration failure of the main thread.
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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, always set to allow
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checking the registration status by reading the 'cpu_id' field.
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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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/* The feature size can be smaller than the minimum rseq area size of 32
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bytes accepted by the syscall, if this is the case, bump the size of
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the registration to the minimum. The 'extra TLS' block is always at
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least 32 bytes. */
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if (size < RSEQ_AREA_SIZE_INITIAL)
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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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RSEQ_SETMEM (cpu_id, RSEQ_CPU_ID_UNINITIALIZED);
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RSEQ_SETMEM (cpu_id_start, 0);
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RSEQ_SETMEM (rseq_cs, 0);
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RSEQ_SETMEM (flags, 0);
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int ret = INTERNAL_SYSCALL_CALL (rseq, RSEQ_SELF (), 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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RSEQ_SETMEM (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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RSEQ_SETMEM (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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