Stage 2

clks/kernel/pmm.c

@@ -0,0 +1,105 @@
+#include <clks/pmm.h>
+#include <clks/string.h>
+#include <clks/types.h>
+
+#define CLKS_PMM_MAX_TRACKED_PAGES 262144ULL
+#define CLKS_PMM_MIN_USABLE_ADDR   0x100000ULL
+
+static u64 clks_pmm_free_stack[CLKS_PMM_MAX_TRACKED_PAGES];
+static u64 clks_pmm_free_top = 0;
+static u64 clks_pmm_managed_pages = 0;
+static u64 clks_pmm_dropped_pages = 0;
+
+static u64 clks_align_up_u64(u64 value, u64 alignment) {
+    return (value + alignment - 1ULL) & ~(alignment - 1ULL);
+}
+
+static u64 clks_align_down_u64(u64 value, u64 alignment) {
+    return value & ~(alignment - 1ULL);
+}
+
+void clks_pmm_init(const struct limine_memmap_response *memmap) {
+    u64 i;
+
+    clks_pmm_free_top = 0;
+    clks_pmm_managed_pages = 0;
+    clks_pmm_dropped_pages = 0;
+    clks_memset(clks_pmm_free_stack, 0, sizeof(clks_pmm_free_stack));
+
+    if (memmap == CLKS_NULL) {
+        return;
+    }
+
+    for (i = 0; i < memmap->entry_count; i++) {
+        const struct limine_memmap_entry *entry = memmap->entries[i];
+        u64 start;
+        u64 end;
+        u64 addr;
+
+        if (entry == CLKS_NULL) {
+            continue;
+        }
+
+        if (entry->type != LIMINE_MEMMAP_USABLE) {
+            continue;
+        }
+
+        start = clks_align_up_u64(entry->base, CLKS_PAGE_SIZE);
+        end = clks_align_down_u64(entry->base + entry->length, CLKS_PAGE_SIZE);
+
+        if (end <= start) {
+            continue;
+        }
+
+        for (addr = start; addr < end; addr += CLKS_PAGE_SIZE) {
+            if (addr < CLKS_PMM_MIN_USABLE_ADDR) {
+                continue;
+            }
+
+            if (clks_pmm_free_top < CLKS_PMM_MAX_TRACKED_PAGES) {
+                clks_pmm_free_stack[clks_pmm_free_top] = addr;
+                clks_pmm_free_top++;
+                clks_pmm_managed_pages++;
+            } else {
+                clks_pmm_dropped_pages++;
+            }
+        }
+    }
+}
+
+u64 clks_pmm_alloc_page(void) {
+    if (clks_pmm_free_top == 0) {
+        return 0ULL;
+    }
+
+    clks_pmm_free_top--;
+    return clks_pmm_free_stack[clks_pmm_free_top];
+}
+
+void clks_pmm_free_page(u64 phys_addr) {
+    if (phys_addr == 0ULL) {
+        return;
+    }
+
+    if ((phys_addr & (CLKS_PAGE_SIZE - 1ULL)) != 0ULL) {
+        return;
+    }
+
+    if (clks_pmm_free_top >= CLKS_PMM_MAX_TRACKED_PAGES) {
+        return;
+    }
+
+    clks_pmm_free_stack[clks_pmm_free_top] = phys_addr;
+    clks_pmm_free_top++;
+}
+
+struct clks_pmm_stats clks_pmm_get_stats(void) {
+    struct clks_pmm_stats stats;
+
+    stats.managed_pages = clks_pmm_managed_pages;
+    stats.free_pages = clks_pmm_free_top;
+    stats.used_pages = clks_pmm_managed_pages - clks_pmm_free_top;
+    stats.dropped_pages = clks_pmm_dropped_pages;
+
+    return stats;
+}