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Justine Tunney 2020-06-15 07:18:57 -07:00
commit c91b3c5006
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ape/lib/flattenhighmemory.c Normal file
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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/config.h"
#include "ape/lib/pc.h"
#include "libc/bits/bits.h"
#include "libc/bits/safemacros.h"
/**
* Virtualizes physical memory.
*
* This function removes memory holes (discovered by e820() earlier) and
* creates the illusion of flat contiguous memory for as much RAM as the
* BIOS reports usable. Memory is safe to use and remap afterwards.
*
* @see ape/ape.S
*/
textreal void flattenhighmemory(struct SmapEntry *e820, struct PageTable *pml4t,
uint64_t *ptsp) {
struct SmapEntry *smap = e820;
struct SmapEntry *hole = e820;
uint64_t paddr = IMAGE_BASE_PHYSICAL;
uint64_t vaddr = IMAGE_BASE_VIRTUAL;
while (smap->size) {
while (smap->size && smap->type != kMemoryUsable) smap++;
paddr = roundup(max(paddr, smap->addr), PAGESIZE);
while (paddr < rounddown(smap->addr + smap->size, PAGESIZE)) {
while (hole->size &&
(hole->type == kMemoryUsable || hole->addr + hole->size < paddr)) {
hole++;
}
if (paddr >= hole->addr && paddr < hole->addr + hole->size) {
paddr = roundup(hole->addr + hole->size, PAGESIZE);
} else {
uint64_t *entry = getpagetableentry(vaddr, 3, pml4t, ptsp);
*entry = paddr | PAGE_V | PAGE_RW;
vaddr += 0x1000;
paddr += 0x1000;
}
}
smap++;
}
}