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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
│ │
│ This program is free software; you can redistribute it and/or modify │
│ it under the terms of the GNU General Public License as published by │
│ the Free Software Foundation; version 2 of the License. │
│ │
│ This program is distributed in the hope that it will be useful, but │
│ WITHOUT ANY WARRANTY; without even the implied warranty of │
│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
│ General Public License for more details. │
│ │
│ You should have received a copy of the GNU General Public License │
│ along with this program; if not, write to the Free Software │
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
│ 02110-1301 USA │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "ape/lib/pc.h"
#include "libc/assert.h"
textreal static uint64_t pushpagetable(uint64_t *ptsp) {
return (*ptsp -= PAGESIZE) | PAGE_V | PAGE_RW;
}
textreal uint64_t *getpagetableentry(int64_t vaddr, unsigned depth,
struct PageTable *pml4t, uint64_t *ptsp) {
uint64_t *entry;
unsigned char shift;
assert(depth <= 3);
assert(!(*ptsp & 0xfff));
assert(!((uintptr_t)pml4t & 0xfff));
shift = 39;
for (;;) {
entry = &pml4t->p[(vaddr >> shift) & 511];
if (!depth--) return entry;
shift -= 9;
if (!*entry) *entry = pushpagetable(ptsp);
pml4t = (void *)(*entry & PAGE_TA);
}
}