181 lines
7.6 KiB
C
181 lines
7.6 KiB
C
/* $NetBSD: pte.h,v 1.1 2001/03/29 04:58:52 fredette Exp $ */
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/*-
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* Copyright (c) 1998 The NetBSD Foundation, Inc.
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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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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN 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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#ifndef _MACHINE_PTE_H
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#define _MACHINE_PTE_H
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#define NCONTEXT 8
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#define NPMEG 256
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#define SEGINV (NPMEG-1)
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#define NPAGSEG 16
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#define NSEGMAP 512
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/*
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* In our zeal to use the sun3 pmap with as few changes as possible,
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* we pretend that sun2 page table entries work more like their sun3
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* counterparts. Namely, we pretend that they simply have PG_WRITE
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* and PG_SYSTEM bits, and we use get_pte and set_pte to translate
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* entries between the two styles.
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*
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* All known valid protections in a real sun2 PTE are given in
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* (disabled) defines below, and are displayed as bitmaps here:
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*
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* 3 2 2 2 2
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* 0 9 8 7 6 meaning
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* -------------------
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* 1 1 1 0 0 PG_KW => a read/write kernel-only page.
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* 1 0 1 0 0 PG_KR => a read-only kernel-only page.
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* 1 1 1 1 1 PG_UW => a read/write kernel/user page.
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* 1 0 1 1 0 PG_URKR => a read-only kernel/user page.
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*
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* The sun3 PTE protections we want to emulate are:
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*
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* PG_SYSTEM | PG_WRITE => a read/write kernel-only page.
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* PG_SYSTEM => a read-only kernel-only page.
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* PG_WRITE => a read/write kernel/user page.
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* => a read-only kernel/user page.
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*
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* We want to assign values to PG_SYSTEM and PG_WRITE, and
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* craft get_pte and set_pte to do a translation from and to the real
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* hardware protections.
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*
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* We begin by noting that bits 30 and 28 are set in all known valid
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* sun2 protections. Since we assume that the kernel can always read
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* all pages in the system, we might as well call one of them the
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* "kernel readable" bit, and say that the other is just always on.
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* We deem bit 30 the "kernel readable" bit. There is some evidence
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* that bit 28 may mean "not a device" (the PROM makes PTEs for its
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* device mappings with bit 28 clear), but I'm not sure enough about
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* this to do anything about it. So, set_pte will always set these
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* bits when it loads a valid PTE, and get_pte will always clear them
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* when it unloads a valid PTE.
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*
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* Bit 25, which SunOS calles the "fill on demand" bit, also needs
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* to be set on all valid PTEs. Dunno any more about this bit.
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*
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* Next, we see that bit 27 is set for all pages the user can access,
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* and clear otherwise. This bit has the opposite meaning of the sun3
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* PG_SYSTEM bit, but that's OK - we will just define PG_SYSTEM to be
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* bit 27, and set_pte and get_pte will invert it when loading or
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* unloading a valid PTE.
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*
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* Bit 29 is set for all pages the kernel can write to. We define
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* PG_WRITE to be bit 29. No inverting is done.
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*
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* That leaves us to take care of bit 26. This bit, and bit 27, need
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* to be set for all pages the user can write to. On the sun3, all
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* user-accessible pages that the kernel can write to, the user can
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* also write to. We can use this fact to make set_pte set bit 26 iff
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* the kernel can write to the page (PG_WRITE is set), and the user
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* can also access the page (bit 27 is set, i.e., PG_SYSTEM was clear
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* before set_pte inverted it).
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*
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* This is what makes set_pte tricky. It begins by clearing bit 26
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* (this is paranoia, if all is working well, this bit should never be
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* set in our pseudo-sun3 PTEs). It then flips PG_SYSTEM to become
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* the user-accessible bit. Lastly, as the tricky part, it sets bits
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* 30 and 28, *and* sets bit 26 by shifting the expression (pte &
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* PG_WRITE) right by two to move the resulting "single bit" into the
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* bit 27 position, ANDing that with bit 27 in the PTE (the
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* user-accessible bit), shifting that right once more to line up with
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* the target bit 26 in the PTE, and ORing it in. This will result in
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* bit 26 being set if the pseudo-sun3 protection was simply PG_WRITE.
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*
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* This could be expressed with if .. else.. logic, but the bit
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* shifts should compile into something that needs no branching.
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*
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* get_pte's job is easier. All it has to do is clear the always-set
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* bits 30, 28, and 25, *and* clear bit 26, and flip PG_SYSTEM. It can
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* clear bit 26 because the value that was there can always be derived
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* from the resulting pseudo-sun3 PG_SYSTEM and PG_WRITE combination.
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*
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* And that's how we reuse the sun3 pmap.
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*/
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#define PG_VALID 0x80000000
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#define PG_WRITE 0x20000000
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#define PG_NC 0x00000000
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#define PG_SYSTEM 0x08000000
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#if 0
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#define PG_KW 0x70000000
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#define PG_KR 0x50000000
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#define PG_UW 0x7C000000
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#define PG_URKR 0x58000000
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#endif
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#define PG_TYPE 0x00C00000
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#define PG_REF 0x00200000
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#define PG_MOD 0x00100000
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#define PG_SPECIAL (PG_VALID|PG_WRITE|PG_SYSTEM|PG_NC|PG_REF|PG_MOD)
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#define PG_PERM (PG_VALID|PG_WRITE|PG_SYSTEM|PG_NC)
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#define PG_MODREF (PG_REF|PG_MOD)
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#define PG_FRAME 0x00000FFF
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#define PG_MOD_SHIFT 20
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#define OBMEM 0
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#define OBIO 1
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#define MBMEM 2 /* on the 2/120, VME_D16 on the 2/50 */
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#define VME_D16 2
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#define MBIO 3 /* on the 2/120, ??? on the 2/50 */
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#define PG_TYPE_SHIFT 22
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#define PG_INVAL 0x0
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#define MAKE_PGTYPE(x) ((x) << PG_TYPE_SHIFT)
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#define PG_PFNUM(pte) (pte & PG_FRAME)
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#define PG_PA(pte) (PG_PFNUM(pte) << PGSHIFT)
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#define PGT_MASK MAKE_PGTYPE(3)
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#define PGT_OBMEM MAKE_PGTYPE(OBMEM) /* onboard memory */
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#define PGT_OBIO MAKE_PGTYPE(OBIO) /* onboard I/O */
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#define PGT_MBMEM MAKE_PGTYPE(MBMEM) /* Multibus memory on the 2/120, VME_D16 on the 2/50 */
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#define PGT_VME_D16 MAKE_PGTYPE(VME_D16) /* VMEbus 16-bit data */
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#define PGT_MBIO MAKE_PGTYPE(MBIO) /* Multibus I/O on the 2/120, ??? on the 2/50 */
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#define VA_SEGNUM(x) ((u_int)(x) >> SEGSHIFT)
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#define VA_PTE_NUM_SHIFT PGSHIFT
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#define VA_PTE_NUM_MASK (((1 << SEGSHIFT) - 1) ^ ((1 << PGSHIFT) - 1))
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#define VA_PTE_NUM(va) ((va & VA_PTE_NUM_MASK) >> VA_PTE_NUM_SHIFT)
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#define PA_PGNUM(pa) ((unsigned)pa >> PGSHIFT)
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#if defined(_KERNEL) || defined(_STANDALONE)
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u_int get_pte __P((vm_offset_t va));
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void set_pte __P((vm_offset_t va, u_int pte));
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#endif /* _KERNEL */
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#endif /* _MACHINE_PTE_H */
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