direct_map: use 1gib pages to construct the direct map
Signed-off-by: Andy-Python-Programmer <andypythonappdeveloper@gmail.com>
diff --git a/stage23/protos/stivale.c b/stage23/protos/stivale.c
index e8a1585a..a0440b27 100644
--- a/stage23/protos/stivale.c
+++ b/stage23/protos/stivale.c
@@ -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));
