From bffd652c16e62c80711be1a8a322092cd8bd1a81 Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop@gmail.com>
Date: Fri, 23 Oct 2020 00:47:19 -0400
Subject: [PATCH] walk multiboot2 memory map

---
 src/mbinfo.c     | 26 ++++++++++++++++++++++++++
 src/multiboot2.h | 19 +++++++++++++------
 2 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/src/mbinfo.c b/src/mbinfo.c
index 48712f6..b3739f2 100644
--- a/src/mbinfo.c
+++ b/src/mbinfo.c
@@ -26,6 +26,32 @@ static void mbinfo_process_tag(const multiboot2_info_tag_t * tag)
         }
         break;
 
+    case MULTIBOOT2_INFO_MEMORY_MAP:
+        {
+            multiboot2_info_memory_map_t * mmap_info =
+                (multiboot2_info_memory_map_t *)tag;
+            size_t sz = sizeof(mmap_info->header) +
+                sizeof(mmap_info->entry_size) +
+                sizeof(mmap_info->entry_version);
+            multiboot2_info_memory_map_entry_t * entry = &mmap_info->entries[0];
+            for (;;)
+            {
+                sz += mmap_info->entry_size;
+                if (sz > mmap_info->header.size)
+                {
+                    break;
+                }
+                if (entry->type == MULTIBOOT2_MEMORY_MAP_TYPE_RAM)
+                {
+                    klog_printf("Memory region %16lx : %16lx\n",
+                            entry->base_addr,
+                            entry->length);
+                }
+                entry = (multiboot2_info_memory_map_entry_t *)((uintptr_t)entry + mmap_info->entry_size);
+            }
+        }
+        break;
+
     case MULTIBOOT2_INFO_FRAMEBUFFER_INFO:
         {
             multiboot2_info_framebuffer_info_t * fbinfo =
diff --git a/src/multiboot2.h b/src/multiboot2.h
index 3881bb9..f39f8a5 100644
--- a/src/multiboot2.h
+++ b/src/multiboot2.h
@@ -84,16 +84,23 @@ typedef struct {
     uint32_t mem_upper;
 } multiboot2_info_basic_memory_info_t;
 
+#define MULTIBOOT2_MEMORY_MAP_TYPE_RAM 1u
+#define MULTIBOOT2_MEMORY_MAP_TYPE_ACPI 3u
+#define MULTIBOOT2_MEMORY_MAP_TYPE_PRESERVE 4u
+#define MULTIBOOT2_MEMORY_MAP_TYPE_DEFECTIVE 5u
+
+typedef struct {
+    uint64_t base_addr;
+    uint64_t length;
+    uint32_t type;
+    uint32_t _reserved;
+} multiboot2_info_memory_map_entry_t;
+
 typedef struct {
     multiboot2_info_tag_t header;
     uint32_t entry_size;
     uint32_t entry_version;
-    struct {
-        uint64_t base_addr;
-        uint64_t length;
-        uint32_t type;
-        uint32_t _reserved;
-    } entries[];
+    multiboot2_info_memory_map_entry_t entries[];
 } multiboot2_info_memory_map_t;
 
 typedef struct {