forked from Qortal/Brooklyn
2a709f28fa
* 0day explit mitigation * Memory corruption prevention * Privilege escalation prevention * Buffer over flow prevention * File System corruption defense * Thread escape prevention This may very well be the most intensive inclusion to BrooklynR. This will not be part of an x86 suite nor it will be released as tool kit. The security core toolkit will remain part of kernel base.
71 lines
2.5 KiB
C
71 lines
2.5 KiB
C
/*
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* Copyright (C) 2010, 2015 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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*
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* membarrier system call
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program 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
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* GNU General Public License for more details.
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*/
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#include <linux/syscalls.h>
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#include <linux/membarrier.h>
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#include <linux/tick.h>
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/*
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* Bitmask made from a "or" of all commands within enum membarrier_cmd,
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* except MEMBARRIER_CMD_QUERY.
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*/
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#define MEMBARRIER_CMD_BITMASK (MEMBARRIER_CMD_SHARED)
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/**
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* sys_membarrier - issue memory barriers on a set of threads
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* @cmd: Takes command values defined in enum membarrier_cmd.
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* @flags: Currently needs to be 0. For future extensions.
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*
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* If this system call is not implemented, -ENOSYS is returned. If the
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* command specified does not exist, or if the command argument is invalid,
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* this system call returns -EINVAL. For a given command, with flags argument
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* set to 0, this system call is guaranteed to always return the same value
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* until reboot.
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*
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* All memory accesses performed in program order from each targeted thread
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* is guaranteed to be ordered with respect to sys_membarrier(). If we use
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* the semantic "barrier()" to represent a compiler barrier forcing memory
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* accesses to be performed in program order across the barrier, and
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* smp_mb() to represent explicit memory barriers forcing full memory
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* ordering across the barrier, we have the following ordering table for
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* each pair of barrier(), sys_membarrier() and smp_mb():
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*
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* The pair ordering is detailed as (O: ordered, X: not ordered):
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*
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* barrier() smp_mb() sys_membarrier()
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* barrier() X X O
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* smp_mb() X O O
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* sys_membarrier() O O O
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*/
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SYSCALL_DEFINE2(membarrier, int, cmd, int, flags)
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{
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/* MEMBARRIER_CMD_SHARED is not compatible with nohz_full. */
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if (tick_nohz_full_enabled())
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return -ENOSYS;
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if (unlikely(flags))
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return -EINVAL;
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switch (cmd) {
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case MEMBARRIER_CMD_QUERY:
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return MEMBARRIER_CMD_BITMASK;
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case MEMBARRIER_CMD_SHARED:
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if (num_online_cpus() > 1)
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synchronize_sched();
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return 0;
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default:
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return -EINVAL;
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}
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}
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