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kernel. When access restrictions are added to a page table entry, we flush the corresponding virtual address mapping from the TLB. In contrast, when access restrictions are removed from a page table entry, we do not flush the virtual address mapping from the TLB. This is exactly as recommended in AMD's documentation. In effect, when access restrictions are removed from a page table entry, AMD's MMUs will transparently refresh a stale TLB entry. In short, this saves us from having to perform potentially costly TLB flushes. In contrast, Intel's MMUs are allowed to generate a spurious page fault based upon the stale TLB entry. Usually, such spurious page faults are handled by vm_fault() without incident. However, when we are executing no-fault sections of the kernel, we are not allowed to execute vm_fault(). This change introduces special-case handling for spurious page faults that occur in no-fault sections of the kernel. In collaboration with: kib Tested by: gibbs (an earlier version) I would also like to acknowledge Hiroki Sato's assistance in diagnosing this problem. MFC after: 1 week
90 lines
2.9 KiB
C
90 lines
2.9 KiB
C
/*-
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* Copyright (c) 1991 Regents of the University of California.
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* All rights reserved.
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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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* 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 the
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* documentation and/or other materials provided with the distribution.
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* 4. Neither the name of the University nor the names of its contributors
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* may be 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 REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from: @(#)proc.h 7.1 (Berkeley) 5/15/91
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* $FreeBSD$
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*/
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#ifndef _MACHINE_PROC_H_
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#define _MACHINE_PROC_H_
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#include <machine/segments.h>
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struct proc_ldt {
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caddr_t ldt_base;
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int ldt_len;
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int ldt_refcnt;
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u_long ldt_active;
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struct segment_descriptor ldt_sd;
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};
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/*
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* Machine-dependent part of the proc structure for i386.
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* Table of MD locks:
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* t - Descriptor tables lock
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*/
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struct mdthread {
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int md_spinlock_count; /* (k) */
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register_t md_saved_flags; /* (k) */
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register_t md_spurflt_addr; /* (k) Spurious page fault address. */
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};
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struct mdproc {
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struct proc_ldt *md_ldt; /* (t) per-process ldt */
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};
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#define KINFO_PROC_SIZE 768
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#ifdef _KERNEL
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/* Get the current kernel thread stack usage. */
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#define GET_STACK_USAGE(total, used) do { \
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struct thread *td = curthread; \
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(total) = td->td_kstack_pages * PAGE_SIZE; \
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(used) = (char *)td->td_kstack + \
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td->td_kstack_pages * PAGE_SIZE - \
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(char *)&td; \
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} while (0)
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void set_user_ldt(struct mdproc *);
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struct proc_ldt *user_ldt_alloc(struct mdproc *, int);
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void user_ldt_free(struct thread *);
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void user_ldt_deref(struct proc_ldt *pldt);
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extern struct mtx dt_lock;
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struct syscall_args {
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u_int code;
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struct sysent *callp;
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register_t args[8];
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int narg;
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};
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#endif /* _KERNEL */
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#endif /* !_MACHINE_PROC_H_ */
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