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direct_map: use 1gib pages to construct the direct map

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Signed-off-by: Andy-Python-Programmer <andypythonappdeveloper@gmail.com>
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Andy-Python-Programmer 2022-01-27 12:03:20 +11:00
parent 45ecb0fb4d
commit 51f5e5b092
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1 changed files with 17 additions and 1 deletions
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18
stage23/protos/stivale.c
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@ -421,11 +421,27 @@ pagemap_t stivale_build_pagemap(bool level5pg, bool unmap_null, struct elf_range
}
// Map 2MiB to 4GiB at higher half base and 0
for (uint64_t i = 0x200000; i < 0x100000000; i += 0x200000) {
//
// NOTE: We cannot just directly map from 2MiB to 4GiB with 1GiB
// pages because if you do the math.
//
// start = 0x200000
// end = 0x40000000
//
// pages_required = (end - start) / (4096 * 512 * 512)
//
// So we map 2MiB to 1GiB with 2MiB pages and then map the rest
// with 1GiB pages :^)
for (uint64_t i = 0x200000; i < 0x40000000; i += 0x200000) {
map_page(pagemap, i, i, 0x03, Size2MiB);
map_page(pagemap, direct_map_offset + i, i, 0x03, Size2MiB);
}
for (uint64_t i = 0x40000000; i < 0x100000000; i += 0x40000000) {
map_page(pagemap, i, i, 0x03, Size1GiB);
map_page(pagemap, direct_map_offset + i, i, 0x03, Size1GiB);
}
size_t _memmap_entries = memmap_entries;
struct e820_entry_t *_memmap =
ext_mem_alloc(_memmap_entries * sizeof(struct e820_entry_t));