1 files changed, 125 insertions, 0 deletions
diff --git a/src/loader/mem.c b/src/loader/mem.c
new file mode 100644
index 0000000..698c85d
--- /dev/null
+++ b/src/loader/mem.c
@@ -0,0 +1,125 @@
+// MIT License, Copyright (c) 2021 Marvin Borner
+// Memory map generator
+
+#include <log.h>
+#include <mem.h>
+#include <pnc.h>
+#include <rem.h>
+
+/**
+ * Memory map using e820 BIOS call
+ */
+
+#define E820_MAX_ENTRIES 256 // Spec
+
+enum e820_entry_type {
+	E820_MEM_NONE,
+	E820_MEM_USABLE,
+	E820_MEM_RESERVED,
+	E820_MEM_RECLAIMABLE,
+	E820_MEM_ACPI_NVS,
+	E820_MEM_UNUSABLE,
+};
+
+struct e820_entry {
+	u32 base_low;
+	u32 base_high;
+	u32 length_low;
+	u32 length_high;
+	enum e820_entry_type type;
+	u32 unused;
+} PACKED;
+
+u16 e820_count = 0;
+struct e820_entry e820_map[E820_MAX_ENTRIES] = { 0 };
+
+static u8 mem_e820(void)
+{
+	struct rem_regs r = { 0 };
+
+	for (u32 i = 0; i < E820_MAX_ENTRIES; i++) {
+		struct e820_entry entry = { 0 };
+
+		r.eax = 0xe820;
+		r.ecx = 24;
+		r.edx = 0x534d4150;
+		r.edi = (u32)&entry;
+		rem_int(0x15, &r, &r);
+
+		if (r.eflags & EFLAGS_CF) {
+			e820_count = i;
+			return 1;
+		}
+
+		e820_map[i] = entry;
+
+		if (!r.ebx) {
+			e820_count = i++;
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * Configure memory map
+ */
+
+#define MAP_MAX_ENTRIES 256
+
+static struct mem_entry mem[MAP_MAX_ENTRIES] = { 0 };
+static struct mem_map map = { .entry = mem, .count = 0 };
+
+static void mem_map_e820(void)
+{
+	u32 i;
+	for (i = 0; i < COUNT(e820_map); i++) {
+		struct e820_entry *e820_entry = &e820_map[i];
+		struct mem_entry *map_entry = &mem[i];
+
+		map_entry->base = e820_entry->base_low;
+		map_entry->length = e820_entry->length_low;
+
+		// Set type accordingly
+		switch (e820_entry->type) {
+		case E820_MEM_NONE:
+			map_entry->type = MEM_USABLE;
+			continue;
+		case E820_MEM_USABLE:
+			map_entry->type = MEM_USABLE;
+			break;
+		case E820_MEM_RESERVED:
+			map_entry->type = MEM_RESERVED;
+			break;
+		case E820_MEM_RECLAIMABLE:
+			map_entry->type = MEM_RECLAIMABLE;
+			break;
+		case E820_MEM_ACPI_NVS:
+			map_entry->type = MEM_ACPI_NVS;
+			break;
+		case E820_MEM_UNUSABLE:
+			map_entry->type = MEM_UNUSABLE;
+			break;
+		default:
+			panic("Unknown e820 type\n");
+		}
+	}
+
+	map.count = i;
+}
+
+struct mem_map *mem_map_get(void)
+{
+	return &map;
+}
+
+void mem_map(void)
+{
+	if (mem_e820()) {
+		mem_map_e820();
+		return;
+	}
+
+	panic("Couldn't find memory map\n");
+}