88 lines
3.9 KiB
C
88 lines
3.9 KiB
C
/****************************************************************************
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* sched/ched_verifytcb.c
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*
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* Copyright (C) 2009, 2017 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <stdbool.h>
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#include <sched.h>
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#include "sched/sched.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: sched_verifytcb
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*
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* Description:
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* Return true if the tcb refers to an active task; false if it is a stale
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* TCB handle.
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*
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****************************************************************************/
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bool sched_verifytcb(FAR struct tcb_s *tcb)
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{
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/* Return true if the PID hashes to this TCB. This will catch the case
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* where the task associated with the TCB has terminated (note that
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* sched_releasedtcb() will nullify the TCB field in that case). The
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* following logic will also detect the case where the task associated
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* with the TCB has terminated and another task has been started with a
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* different TCB but with a PID hashing to the same entry.
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*
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* NOTE: In the event that the TCB has terminated, the 'tcb' parameter
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* will point at either a stale or a re-allocated memory allocation. The
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* PID fetched by the use of the bad pointer(tcb->pid) should not cause
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* any memory faults because we do at least know that the pointer refers
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* to valid memory in the kernel address space and that the hash macro,
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* PIDHASH(), will return a valid, in-range index into the g_pidhash[]
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* table.
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*
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* REVISIT: This logic will not, however, catch the case where the task
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* originally associated with the TCB has terminated, but a new task was
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* started reusing the same memory allocation for its TDB that was freed
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* by the terminated task. In this case, a false positive value will be
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* returned: The TCB is valid but does not refer to the same task as
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* before. This case is not detectable with the limited amount of
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* information available.
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*/
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return tcb == g_pidhash[PIDHASH(tcb->pid)].tcb;
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}
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