Add e820 driver

src/lib/e820.c

@@ -0,0 +1,55 @@
+#include <lib/e820.h>
+#include <lib/real.h>
+#include <lib/blib.h>
+
+struct e820_entry_t e820_map[E820_MAX_ENTRIES];
+
+static const char *e820_type(uint32_t type) {
+    switch (type) {
+        case 1:
+            return "Usable RAM";
+        case 2:
+            return "Reserved";
+        case 3:
+            return "ACPI reclaimable";
+        case 4:
+            return "ACPI NVS";
+        case 5:
+            return "Bad memory";
+        default:
+            return "???";
+    }
+}
+
+void init_e820(void) {
+    struct rm_regs r = {0};
+
+    for (size_t i = 0; i < E820_MAX_ENTRIES; i++) {
+        r.eax = 0xe820;
+        r.ecx = 24;
+        r.edx = 0x534d4150;
+        r.edi = (uint32_t)&e820_map[i];
+        rm_int(0x15, &r, &r);
+
+        if (r.eflags & EFLAGS_CF) {
+            e820_map[i].type = 0;
+            goto done;
+        }
+
+        if (!r.ebx) {
+            e820_map[i+1].type = 0;
+            goto done;
+        }
+    }
+
+    print("e820: Too many entries!\n");
+
+done:
+    for (size_t i = 0; e820_map[i].type; i++) {
+        print("e820: [%X -> %X] : %X  <%s>\n",
+              e820_map[i].base,
+              e820_map[i].base + e820_map[i].length,
+              e820_map[i].length,
+              e820_type(e820_map[i].type));
+    }
+}

src/lib/e820.h

@@ -0,0 +1,19 @@
+#ifndef __LIB__E820_H__
+#define __LIB__E820_H__
+
+#include <stdint.h>
+
+#define E820_MAX_ENTRIES 256
+
+struct e820_entry_t {
+    uint64_t base;
+    uint64_t length;
+    uint32_t type;
+    uint32_t unused;
+} __attribute__((packed));
+
+extern struct e820_entry_t e820_map[E820_MAX_ENTRIES];
+
+void init_e820(void);
+
+#endif

src/lib/real.h

@@ -9,6 +9,7 @@
 #define rm_desegment(seg, off) (((uint32_t)(seg) << 4) + (uint32_t)(off))
 
 #define EFLAGS_CF (1 << 0)
+#define EFLAGS_ZF (1 << 6)
 
 struct rm_regs {
     uint32_t eflags;