41 lines
2.5 KiB
C
41 lines
2.5 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "ape/lib/pc.h"
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#include "libc/assert.h"
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textreal static uint64_t pushpagetable(uint64_t *ptsp) {
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return (*ptsp -= PAGESIZE) | PAGE_V | PAGE_RW;
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}
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textreal uint64_t *getpagetableentry(uint64_t vaddr, unsigned depth,
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struct PageTable *pml4t, uint64_t *ptsp) {
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assert(depth <= 3);
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assert(*ptsp % PAGESIZE == 0);
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assert((intptr_t)pml4t % PAGESIZE == 0);
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unsigned char shift = 39;
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for (;;) {
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uint64_t *entry = &pml4t->p[(vaddr >> shift) & 511];
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if (!depth--) return entry;
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shift -= 9;
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if (!*entry) *entry = pushpagetable(ptsp);
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pml4t = (void *)(*entry & PAGE_TA);
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}
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}
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