sys/arch/sun2/include/pte.h

   1 /*      $NetBSD: pte.h,v 1.7 2008/04/28 20:23:37 martin Exp $   */
   2
   3 /*-
   4  * Copyright (c) 1998 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  26  * POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #ifndef _MACHINE_PTE_H
  30 #define _MACHINE_PTE_H
  31
  32 #define NCONTEXT 8
  33 #define NPMEG   256
  34 #define SEGINV  (NPMEG-1)
  35 #define NPAGSEG 16
  36 #define NSEGMAP 512
  37
  38 /*
  39  * In our zeal to use the sun3 pmap with as few changes as possible,
  40  * we pretend that sun2 page table entries work more like their sun3
  41  * counterparts.  Namely, we pretend that they simply have PG_WRITE
  42  * and PG_SYSTEM bits, and we use get_pte and set_pte to translate
  43  * entries between the two styles.
  44  *
  45  * All known valid protections in a real sun2 PTE are given in
  46  * (disabled) defines below, and are displayed as bitmaps here:
  47  *
  48  * 3 2 2 2 2
  49  * 0 9 8 7 6   meaning
  50  * -------------------
  51  * 1 1 1 0 0   PG_KW => a read/write kernel-only page.
  52  * 1 0 1 0 0   PG_KR => a read-only kernel-only page.
  53  * 1 1 1 1 1   PG_UW => a read/write kernel/user page.
  54  * 1 0 1 1 0   PG_URKR => a read-only kernel/user page.
  55  *
  56  * The sun3 PTE protections we want to emulate are:
  57  *
  58  * PG_SYSTEM | PG_WRITE => a read/write kernel-only page.
  59  * PG_SYSTEM            => a read-only kernel-only page.
  60  *             PG_WRITE => a read/write kernel/user page.
  61  *                      => a read-only kernel/user page.
  62  *
  63  * We want to assign values to PG_SYSTEM and PG_WRITE, and
  64  * craft get_pte and set_pte to do a translation from and to the real
  65  * hardware protections.
  66  *
  67  * We begin by noting that bits 30 and 28 are set in all known valid
  68  * sun2 protections.  Since we assume that the kernel can always read
  69  * all pages in the system, we might as well call one of them the
  70  * "kernel readable" bit, and say that the other is just always on.
  71  * We deem bit 30 the "kernel readable" bit.  There is some evidence
  72  * that bit 28 may mean "not a device" (the PROM makes PTEs for its
  73  * device mappings with bit 28 clear), but I'm not sure enough about
  74  * this to do anything about it.  So, set_pte will always set these
  75  * bits when it loads a valid PTE, and get_pte will always clear them
  76  * when it unloads a valid PTE.
  77  *
  78  * Bit 25, which SunOS calles the "fill on demand" bit, also needs
  79  * to be set on all valid PTEs.  Dunno any more about this bit.
  80  *
  81  * Next, we see that bit 27 is set for all pages the user can access,
  82  * and clear otherwise.  This bit has the opposite meaning of the sun3
  83  * PG_SYSTEM bit, but that's OK - we will just define PG_SYSTEM to be
  84  * bit 27, and set_pte and get_pte will invert it when loading or
  85  * unloading a valid PTE.
  86  *
  87  * Bit 29 is set for all pages the kernel can write to.  We define
  88  * PG_WRITE to be bit 29.  No inverting is done.
  89  *
  90  * That leaves us to take care of bit 26.  This bit, and bit 27, need
  91  * to be set for all pages the user can write to.  On the sun3, all
  92  * user-accessible pages that the kernel can write to, the user can
  93  * also write to.  We can use this fact to make set_pte set bit 26 iff
  94  * the kernel can write to the page (PG_WRITE is set), and the user
  95  * can also access the page (bit 27 is set, i.e., PG_SYSTEM was clear
  96  * before set_pte inverted it).
  97  *
  98  * This is what makes set_pte tricky.  It begins by clearing bit 26
  99  * (this is paranoia, if all is working well, this bit should never be
 100  * set in our pseudo-sun3 PTEs).  It then flips PG_SYSTEM to become
 101  * the user-accessible bit.  Lastly, as the tricky part, it sets bits
 102  * 30 and 28, *and* sets bit 26 by shifting the expression (pte &
 103  * PG_WRITE) right by two to move the resulting "single bit" into the
 104  * bit 27 position, ANDing that with bit 27 in the PTE (the
 105  * user-accessible bit), shifting that right once more to line up with
 106  * the target bit 26 in the PTE, and ORing it in.  This will result in
 107  * bit 26 being set if the pseudo-sun3 protection was simply PG_WRITE.
 108  *
 109  * This could be expressed with if .. else.. logic, but the bit
 110  * shifts should compile into something that needs no branching.
 111  *
 112  * get_pte's job is easier.  All it has to do is clear the always-set
 113  * bits 30, 28, and 25, *and* clear bit 26, and flip PG_SYSTEM.  It can
 114  * clear bit 26 because the value that was there can always be derived
 115  * from the resulting pseudo-sun3 PG_SYSTEM and PG_WRITE combination.
 116  *
 117  * And that's how we reuse the sun3 pmap.
 118  */
 119 #define PG_VALID   0x80000000
 120 #define PG_WRITE   0x20000000
 121 #define PG_NC      0x00000000
 122 #define PG_SYSTEM  0x08000000
 123 #if 0
 124 #define PG_KW      0x70000000
 125 #define PG_KR      0x50000000
 126 #define PG_UW      0x7C000000
 127 #define PG_URKR    0x58000000
 128 #endif
 129 #define PG_TYPE    0x00C00000
 130 #define PG_REF     0x00200000
 131 #define PG_MOD     0x00100000
 132
 133 #define PG_SPECIAL (PG_VALID|PG_WRITE|PG_SYSTEM|PG_NC|PG_REF|PG_MOD)
 134 #define PG_PERM    (PG_VALID|PG_WRITE|PG_SYSTEM|PG_NC)
 135 #define PG_MODREF  (PG_REF|PG_MOD)
 136 #define PG_FRAME   0x00000FFF
 137
 138 #define PG_MOD_SHIFT 20
 139
 140 /*
 141  * At first glance, the need for two page types for the VME
 142  * bus on the sun2 isn't obvious - it's a single 16 bit wide
 143  * bus with 24 address lines, with the A16 devices simply
 144  * found starting at addresses 0xff0000.  No problem - use
 145  * only one page type.  But the sun2 VM page frame is only 12
 146  * bits wide, with 11 bit wide page offsets, meaning only 23
 147  * address bits, not enough to cover the entire VME bus.  So
 148  * we have two page types, with the low bit of the page type
 149  * representing the 24th VME bus address bit.
 150  */
 151 #define OBMEM   0
 152 #define OBIO    1
 153 #define MBMEM   2       /* on the 2/120 */
 154 #define VME0    2       /* on the 2/50 (VME addresses [0..0x7fffff]) */
 155 #define MBIO    3       /* on the 2/120 */
 156 #define VME8    3       /* on the 2/50 (VME addresses [0x800000..0xffffff]) */
 157 #define PG_TYPE_SHIFT 22
 158
 159 #define PG_INVAL   0x0
 160
 161 #define MAKE_PGTYPE(x) ((x) << PG_TYPE_SHIFT)
 162 #define PG_PFNUM(pte) (pte & PG_FRAME)
 163 #define PG_PA(pte) (PG_PFNUM(pte) << PGSHIFT)
 164
 165 #define PGT_MASK        MAKE_PGTYPE(3)
 166 #define PGT_OBMEM       MAKE_PGTYPE(OBMEM)              /* onboard memory */
 167 #define PGT_OBIO        MAKE_PGTYPE(OBIO)               /* onboard I/O */
 168 #define PGT_MBMEM       MAKE_PGTYPE(MBMEM)      /* on the 2/120 */
 169 #define PGT_VME0        MAKE_PGTYPE(VME0)       /* on the 2/50 */
 170 #define PGT_MBIO        MAKE_PGTYPE(MBIO)       /* on the 2/120 */
 171 #define PGT_VME8        MAKE_PGTYPE(VME8)       /* on the 2/50 */
 172
 173 #define VA_SEGNUM(x)    ((u_int)(x) >> SEGSHIFT)
 174
 175 #define VA_PTE_NUM_SHIFT  PGSHIFT
 176 #define VA_PTE_NUM_MASK   (((1 << SEGSHIFT) - 1) ^ ((1 << PGSHIFT) - 1))
 177 #define VA_PTE_NUM(va) (((va) & VA_PTE_NUM_MASK) >> VA_PTE_NUM_SHIFT)
 178
 179 #define PA_PGNUM(pa) ((unsigned)(pa) >> PGSHIFT)
 180
 181 #if defined(_KERNEL) || defined(_STANDALONE)
 182 #define kernel_context() get_context(); set_context(0)
 183 #define restore_context set_context
 184 u_int get_pte(vaddr_t);
 185 void  set_pte(vaddr_t, u_int);
 186 #endif  /* _KERNEL */
 187
 188 #endif  /* _MACHINE_PTE_H */