Read memory map tags from multiboot

src/kernel/boot/kmain.c

@@ -6,13 +6,6 @@
 #include <cpu.h>
 #include <interrupts.h>
 
-registers *divbyzero(registers *r)
-{
-  debug_error("Divide by zero error!\n");
-  debug_print_registers(r);
-  for(;;);
-}
-
 void kmain(uint64_t multiboot_magic, void *multiboot_data)
 {
   serial_init(PORT_COM1);
@@ -26,13 +19,10 @@ void kmain(uint64_t multiboot_magic, void *multiboot_data)
   cpu_init();
 
 
-  // Force and catch a divide by zero exception
-  // ISR 0
-  bind_interrupt(0, divbyzero);
-  int a = 5, b = 0;
-  int c = a/b;
-
-  debug("a: %d b:%d c:%d\n", a,b,c);
+  uintptr_t start, end;
+  uint32_t type, i=0;
+  while(!multiboot_get_memory_area(i++, &start, &end, &type))
+    debug_printf("Mem %d 0x%x-0x%x\n", type, start, end);
 
   debug_ok("Boot \"Complete\"\n");
 

src/kernel/boot/multiboot.c

@@ -15,14 +15,29 @@ struct tag {
   uint8_t data[];
 }__attribute__((packed));
 
+struct mmap_entry{
+  uint64_t base;
+  uint64_t len;
+  uint32_t type;
+  uint32_t reserved;
+}__attribute__((packed));
+
+struct mmap {
+  uint32_t entry_size;
+  uint32_t entry_version;
+  struct mmap_entry entries[];
+}__attribute__((packed));
+
 #define MBOOT2_COMMANDLINE 1
 #define MBOOT2_BOOTLOADER 2
+#define MBOOT2_MMAP 6
 
 struct kernel_boot_data_st kernel_boot_data;
 
 int parse_multiboot2(struct taglist *tags)
 {
   struct tag *tag = incptr(tags, sizeof(struct taglist));
+  struct mmap *mmap;
   while(tag->type)
   {
     switch(tag->type)
@@ -33,6 +48,10 @@ int parse_multiboot2(struct taglist *tags)
       case MBOOT2_COMMANDLINE:
         kernel_boot_data.commandline = (char *)tag->data;
         break;
+      case MBOOT2_MMAP:
+        mmap = kernel_boot_data.mmap = (void *)tag->data;
+        kernel_boot_data.mmap_size = (tag->size - 8)/mmap->entry_size;
+        break;
       default:
         debug_warning("Unknown multiboot tag type:%d \n", tag->type);
     }
@@ -54,3 +73,17 @@ int multiboot_init(uint64_t magic, void *mboot_info)
 
   return 0;
 }
+
+int multiboot_get_memory_area(size_t count, uintptr_t *start, uintptr_t *end, uint32_t *type)
+{
+  if(count >= kernel_boot_data.mmap_size) return 1;
+
+  struct mmap *mmap = kernel_boot_data.mmap;
+  struct mmap_entry *entry = mmap->entries;
+  entry = incptr(entry, count*mmap->entry_size);
+
+  *start = entry->base;
+  *end = entry->base + entry->len;
+  *type = entry->type;
+  return 0;
+}

src/kernel/boot/multiboot.tt

@@ -149,3 +149,75 @@ TEST(reads_multiple_tags_4)
   ASSERT_EQ_STR(kernel_boot_data.bootloader, name, strlen(name));
   free(tags);
 }
+
+TEST(reads_mmap_tag)
+{
+  uint32_t mmap[] = {24, 0,
+  0x90ABCDEF, 0x12345678, 0x00010000, 0x00000000, 0x1, 0x0
+  };
+  void *tags = generate_taglist(2,
+    generate_tag(6, mmap, 32),
+    generate_tag(0,0,0)
+  );
+  multiboot_init(MAGIC, tags);
+
+  ASSERT_EQ_INT(kernel_boot_data.mmap_size, 1);
+  free(tags);
+}
+void setup_memory_areas()
+{
+  uint32_t mmap[] = {24, 0,
+  0x90ABCDEF, 0x12345678, 0x00010000, 0x00000000, 0x1, 0x0,
+  0x0ABCDEF1, 0x23456789, 0x00010000, 0x00000000, 0x1, 0x0
+  };
+  void *tags = generate_taglist(2,
+    generate_tag(6, mmap, 56),
+    generate_tag(0,0,0)
+  );
+  multiboot_init(MAGIC, tags);
+}
+TEST(reads_multiple_mmap_tags)
+{
+  setup_memory_areas();
+  ASSERT_EQ_INT(kernel_boot_data.mmap_size, 2);
+}
+TEST(returns_memory_area_start)
+{
+  setup_memory_areas();
+  uintptr_t start, end;
+  uint32_t type;
+  multiboot_get_memory_area(0, &start, &end, &type);
+  ASSERT_EQ_PTR(start, 0x1234567890ABCDEF);
+}
+TEST(returns_memory_area_end)
+{
+  setup_memory_areas();
+  uintptr_t start, end;
+  uint32_t type;
+  multiboot_get_memory_area(0, &start, &end, &type);
+  ASSERT_EQ_PTR(end, 0x1234567890ACCDEF);
+}
+TEST(returns_memory_area_type)
+{
+  setup_memory_areas();
+  uintptr_t start, end;
+  uint32_t type;
+  multiboot_get_memory_area(0, &start, &end, &type);
+  ASSERT_EQ_INT(type, 1);
+}
+TEST(returns_second_memory_area_start)
+{
+  setup_memory_areas();
+  uintptr_t start, end;
+  uint32_t type;
+  multiboot_get_memory_area(1, &start, &end, &type);
+  ASSERT_EQ_PTR(start, 0x234567890ABCDEF1);
+}
+TEST(does_not_return_too_many_areas)
+{
+  setup_memory_areas();
+  uintptr_t start, end;
+  uint32_t type;
+  int retval = multiboot_get_memory_area(2, &start, &end, &type);
+  ASSERT_NEQ_INT(retval, 0);
+}

src/kernel/include/multiboot.h

@@ -1,12 +1,16 @@
 #pragma once
 #include <stdint.h>
+#include <stddef.h>
 struct kernel_boot_data_st
 {
   int multiboot_version;
   char *bootloader;
   char *commandline;
+  size_t mmap_size;
+  void *mmap;
 };
 
 extern struct kernel_boot_data_st kernel_boot_data;
 
 int multiboot_init(uint64_t magic, void *mboot_info);
+int multiboot_get_memory_area(size_t count, uintptr_t *start, uintptr_t *end, uint32_t *type);