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//! Physical Memory Manager Setup
const bitmap_ops = @import("../bitmap/bitmap.zig");
const state = @import("../state.zig");
const types = @import("../types/types.zig");
const common = @import("../../../common/common.zig");
const memory_layout = common.constants.memory.layout;
pub fn initialize_from_memory_map(
memory_map_entries: [*]const types.MemoryRegion,
entry_count: u64,
bitmap_location: u64,
) void {
const pmm_state = state.get_state();
var highest_address: u64 = 0;
var entry_index: u64 = 0;
while (entry_index < entry_count) : (entry_index += 1) {
const region = memory_map_entries[entry_index];
const region_end = region.end_address();
if (region_end > highest_address) {
highest_address = region_end;
}
}
pmm_state.total_pages = highest_address >> 12;
pmm_state.bitmap = @ptrFromInt(bitmap_location + memory_layout.physmap_base);
pmm_state.bitmap_size = (pmm_state.total_pages + 7) / 8;
bitmap_ops.set_range(pmm_state.bitmap, 0, pmm_state.total_pages);
pmm_state.free_pages = 0;
pmm_state.used_pages = pmm_state.total_pages;
entry_index = 0;
while (entry_index < entry_count) : (entry_index += 1) {
const region = memory_map_entries[entry_index];
if (region.is_usable()) {
mark_region_free(region.base_address, region.length);
}
}
reserve_kernel_memory();
reserve_bitmap_memory(bitmap_location);
pmm_state.search_start = 0;
pmm_state.initialized = true;
}
fn mark_region_free(base_address: u64, length: u64) void {
const pmm_state = state.get_state();
const start_page = (base_address + 4095) >> 12;
const end_page = (base_address + length) >> 12;
if (end_page <= start_page) {
return;
}
const page_count = end_page - start_page;
bitmap_ops.clear_range(pmm_state.bitmap, start_page, page_count);
pmm_state.free_pages += page_count;
pmm_state.used_pages -= page_count;
}
fn reserve_kernel_memory() void {
const pmm_state = state.get_state();
const kernel_start_page: u64 = 0;
const kernel_end_page: u64 = 0x200;
var page_index = kernel_start_page;
while (page_index < kernel_end_page) : (page_index += 1) {
if (!bitmap_ops.test_bit(pmm_state.bitmap, page_index)) {
bitmap_ops.set_bit(pmm_state.bitmap, page_index);
pmm_state.free_pages -= 1;
pmm_state.used_pages += 1;
}
}
}
fn reserve_bitmap_memory(bitmap_location: u64) void {
const pmm_state = state.get_state();
const bitmap_start_page = bitmap_location >> 12;
const bitmap_page_count = (pmm_state.bitmap_size + 4095) >> 12;
var page_index: u64 = 0;
while (page_index < bitmap_page_count) : (page_index += 1) {
const current_page = bitmap_start_page + page_index;
if (!bitmap_ops.test_bit(pmm_state.bitmap, current_page)) {
bitmap_ops.set_bit(pmm_state.bitmap, current_page);
pmm_state.free_pages -= 1;
pmm_state.used_pages += 1;
}
}
}
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