1 /* $NetBSD: pte.h,v 1.4 2001/11/30 17:52:34 fredette 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 * 3. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the NetBSD 18 * Foundation, Inc. and its contributors. 19 * 4. Neither the name of The NetBSD Foundation nor the names of its 20 * contributors may be used to endorse or promote products derived 21 * from this software without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 24 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 25 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 26 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 27 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 28 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 29 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 30 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 31 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 32 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 33 * POSSIBILITY OF SUCH DAMAGE. 34 */ 35 36 #ifndef _MACHINE_PTE_H 37 #define _MACHINE_PTE_H 38 39 #define NCONTEXT 8 40 #define NPMEG 256 41 #define SEGINV (NPMEG-1) 42 #define NPAGSEG 16 43 #define NSEGMAP 512 44 45 /* 46 * In our zeal to use the sun3 pmap with as few changes as possible, 47 * we pretend that sun2 page table entries work more like their sun3 48 * counterparts. Namely, we pretend that they simply have PG_WRITE 49 * and PG_SYSTEM bits, and we use get_pte and set_pte to translate 50 * entries between the two styles. 51 * 52 * All known valid protections in a real sun2 PTE are given in 53 * (disabled) defines below, and are displayed as bitmaps here: 54 * 55 * 3 2 2 2 2 56 * 0 9 8 7 6 meaning 57 * ------------------- 58 * 1 1 1 0 0 PG_KW => a read/write kernel-only page. 59 * 1 0 1 0 0 PG_KR => a read-only kernel-only page. 60 * 1 1 1 1 1 PG_UW => a read/write kernel/user page. 61 * 1 0 1 1 0 PG_URKR => a read-only kernel/user page. 62 * 63 * The sun3 PTE protections we want to emulate are: 64 * 65 * PG_SYSTEM | PG_WRITE => a read/write kernel-only page. 66 * PG_SYSTEM => a read-only kernel-only page. 67 * PG_WRITE => a read/write kernel/user page. 68 * => a read-only kernel/user page. 69 * 70 * We want to assign values to PG_SYSTEM and PG_WRITE, and 71 * craft get_pte and set_pte to do a translation from and to the real 72 * hardware protections. 73 * 74 * We begin by noting that bits 30 and 28 are set in all known valid 75 * sun2 protections. Since we assume that the kernel can always read 76 * all pages in the system, we might as well call one of them the 77 * "kernel readable" bit, and say that the other is just always on. 78 * We deem bit 30 the "kernel readable" bit. There is some evidence 79 * that bit 28 may mean "not a device" (the PROM makes PTEs for its 80 * device mappings with bit 28 clear), but I'm not sure enough about 81 * this to do anything about it. So, set_pte will always set these 82 * bits when it loads a valid PTE, and get_pte will always clear them 83 * when it unloads a valid PTE. 84 * 85 * Bit 25, which SunOS calles the "fill on demand" bit, also needs 86 * to be set on all valid PTEs. Dunno any more about this bit. 87 * 88 * Next, we see that bit 27 is set for all pages the user can access, 89 * and clear otherwise. This bit has the opposite meaning of the sun3 90 * PG_SYSTEM bit, but that's OK - we will just define PG_SYSTEM to be 91 * bit 27, and set_pte and get_pte will invert it when loading or 92 * unloading a valid PTE. 93 * 94 * Bit 29 is set for all pages the kernel can write to. We define 95 * PG_WRITE to be bit 29. No inverting is done. 96 * 97 * That leaves us to take care of bit 26. This bit, and bit 27, need 98 * to be set for all pages the user can write to. On the sun3, all 99 * user-accessible pages that the kernel can write to, the user can 100 * also write to. We can use this fact to make set_pte set bit 26 iff 101 * the kernel can write to the page (PG_WRITE is set), and the user 102 * can also access the page (bit 27 is set, i.e., PG_SYSTEM was clear 103 * before set_pte inverted it). 104 * 105 * This is what makes set_pte tricky. It begins by clearing bit 26 106 * (this is paranoia, if all is working well, this bit should never be 107 * set in our pseudo-sun3 PTEs). It then flips PG_SYSTEM to become 108 * the user-accessible bit. Lastly, as the tricky part, it sets bits 109 * 30 and 28, *and* sets bit 26 by shifting the expression (pte & 110 * PG_WRITE) right by two to move the resulting "single bit" into the 111 * bit 27 position, ANDing that with bit 27 in the PTE (the 112 * user-accessible bit), shifting that right once more to line up with 113 * the target bit 26 in the PTE, and ORing it in. This will result in 114 * bit 26 being set if the pseudo-sun3 protection was simply PG_WRITE. 115 * 116 * This could be expressed with if .. else.. logic, but the bit 117 * shifts should compile into something that needs no branching. 118 * 119 * get_pte's job is easier. All it has to do is clear the always-set 120 * bits 30, 28, and 25, *and* clear bit 26, and flip PG_SYSTEM. It can 121 * clear bit 26 because the value that was there can always be derived 122 * from the resulting pseudo-sun3 PG_SYSTEM and PG_WRITE combination. 123 * 124 * And that's how we reuse the sun3 pmap. 125 */ 126 #define PG_VALID 0x80000000 127 #define PG_WRITE 0x20000000 128 #define PG_NC 0x00000000 129 #define PG_SYSTEM 0x08000000 130 #if 0 131 #define PG_KW 0x70000000 132 #define PG_KR 0x50000000 133 #define PG_UW 0x7C000000 134 #define PG_URKR 0x58000000 135 #endif 136 #define PG_TYPE 0x00C00000 137 #define PG_REF 0x00200000 138 #define PG_MOD 0x00100000 139 140 #define PG_SPECIAL (PG_VALID|PG_WRITE|PG_SYSTEM|PG_NC|PG_REF|PG_MOD) 141 #define PG_PERM (PG_VALID|PG_WRITE|PG_SYSTEM|PG_NC) 142 #define PG_MODREF (PG_REF|PG_MOD) 143 #define PG_FRAME 0x00000FFF 144 145 #define PG_MOD_SHIFT 20 146 147 /* 148 * At first glance, the need for two page types for the VME 149 * bus on the sun2 isn't obvious - it's a single 16 bit wide 150 * bus with 24 address lines, with the A16 devices simply 151 * found starting at addresses 0xff0000. No problem - use 152 * only one page type. But the sun2 VM page frame is only 12 153 * bits wide, with 11 bit wide page offsets, meaning only 23 154 * address bits, not enough to cover the entire VME bus. So 155 * we have two page types, with the low bit of the page type 156 * representing the 24th VME bus address bit. 157 */ 158 #define OBMEM 0 159 #define OBIO 1 160 #define MBMEM 2 /* on the 2/120 */ 161 #define VME0 2 /* on the 2/50 (VME addresses [0..0x7fffff]) */ 162 #define MBIO 3 /* on the 2/120 */ 163 #define VME8 3 /* on the 2/50 (VME addresses [0x800000..0xffffff]) */ 164 #define PG_TYPE_SHIFT 22 165 166 #define PG_INVAL 0x0 167 168 #define MAKE_PGTYPE(x) ((x) << PG_TYPE_SHIFT) 169 #define PG_PFNUM(pte) (pte & PG_FRAME) 170 #define PG_PA(pte) (PG_PFNUM(pte) << PGSHIFT) 171 172 #define PGT_MASK MAKE_PGTYPE(3) 173 #define PGT_OBMEM MAKE_PGTYPE(OBMEM) /* onboard memory */ 174 #define PGT_OBIO MAKE_PGTYPE(OBIO) /* onboard I/O */ 175 #define PGT_MBMEM MAKE_PGTYPE(MBMEM) /* on the 2/120 */ 176 #define PGT_VME0 MAKE_PGTYPE(VME0) /* on the 2/50 */ 177 #define PGT_MBIO MAKE_PGTYPE(MBIO) /* on the 2/120 */ 178 #define PGT_VME8 MAKE_PGTYPE(VME8) /* on the 2/50 */ 179 180 #define VA_SEGNUM(x) ((u_int)(x) >> SEGSHIFT) 181 182 #define VA_PTE_NUM_SHIFT PGSHIFT 183 #define VA_PTE_NUM_MASK (((1 << SEGSHIFT) - 1) ^ ((1 << PGSHIFT) - 1)) 184 #define VA_PTE_NUM(va) ((va & VA_PTE_NUM_MASK) >> VA_PTE_NUM_SHIFT) 185 186 #define PA_PGNUM(pa) ((unsigned)pa >> PGSHIFT) 187 188 #if defined(_KERNEL) || defined(_STANDALONE) 189 #define kernel_context() get_context(); set_context(0) 190 #define restore_context set_context 191 u_int get_pte __P((vaddr_t va)); 192 void set_pte __P((vaddr_t va, u_int pte)); 193 #endif /* _KERNEL */ 194 195 #endif /* _MACHINE_PTE_H */ 196