...

src/boot/main.c

@@ -1,67 +1,8 @@
 #include "console.h"
-#include "multiboot2.h"
+#include "pmm.h"
 
-#include <def.h>
-#include "console.h"
-#include "multiboot2.h"
-#include "panic.h"
-#include "util.h"
-
-static void *multiboot_find_tag(uptr multiboot_info, u32 type) {
-    uptr next = multiboot_info + 8;
-
-    while (true) {
-        multiboot_tag *tag = (multiboot_tag*)next;
-
-        if (tag->type == MULTIBOOT_TAG_TYPE_END) {
-            return NULL;
-        }
-
-        if (tag->type == type) {
-            return tag;
-        }
-
-        next = align(next + tag->size, MULTIBOOT_TAG_ALIGN);
-    }
-}
-
-#define MAX_REGIONS 64
-
-typedef struct {
-    u64 base_address;
-    u64 length;
-} region;
-
-extern uptr kernel_start;
-extern uptr kernel_end;
-
-static region regions[MAX_REGIONS] = {0};
-static size_t region_count = 0;
-
-static void find_memory_regions(uptr multiboot_info) {
-    multiboot_tag_mmap *tag = multiboot_find_tag(multiboot_info, MULTIBOOT_TAG_TYPE_MMAP);
-    if (tag == NULL) {
-        boot_panic("Multiboot did not provide mmap tag");
-    }
-
-    u32 entry_count = (tag->size - 16) / tag->entry_size;
-    u8 *entry_ptr = (u8*)tag->entries;
-
-    for (u32 i = 0; i < entry_count; ++i) {
-        multiboot_mmap_entry *entry = (multiboot_mmap_entry*)entry_ptr;
-
-        if (entry->type == MULTIBOOT_MEMORY_AVAILABLE) {
-            if (region_count >= MAX_REGIONS) {
-                boot_panic("Too many memory regions");
-            }
-
-            regions[region_count++] = (region){ entry->base_address, entry->length };
-        }
-
-        entry_ptr += tag->entry_size;
-    }
-}
-
-void kmain(uptr multiboot_info) {
-    find_memory_regions(multiboot_info);
+// We are now in long mode with kernel pages and vga buffer identity mapped
+void x86_64_main() {
+    console_clear();
+    pmm_init();
 }

src/boot/multiboot2.c

@@ -0,0 +1,31 @@
+#include "multiboot2.h"
+#include "symbols.h"
+#include "util.h"
+
+// [size:4][reserved:4][data:N]
+#define INFO_DATA_OFFSET    8
+
+#define TAG_TYPE_OFFSET     0
+#define TAG_SIZE_OFFSET     4
+
+void *multiboot_get_tag(u32 type) {
+    uptr current = get_multiboot_info() + INFO_DATA_OFFSET;
+
+    while (true) {
+        u32 tag_type = *(u32*)(current + TAG_TYPE_OFFSET);
+        u32 tag_size = *(u32*)(current + TAG_SIZE_OFFSET);
+
+        if (tag_type == MULTIBOOT_TAG_TYPE_END) {
+            break;
+        }
+
+        if (tag_type == type) {
+            return (void*)current;
+        }
+
+        // note(nub31): Each tag is aligned to 8 bytes
+        current = ALIGN_UP(current + tag_size, 8);
+    }
+
+    return NULL;
+}

src/boot/multiboot2.h

@@ -19,9 +19,7 @@
  */
 #pragma once
 
-#define MULTIBOOT_BOOTLOADER_MAGIC 0x36d76289
-
-#define MULTIBOOT_TAG_ALIGN 8
+#include <def.h>
 
 #define MULTIBOOT_TAG_TYPE_END 0
 #define MULTIBOOT_TAG_TYPE_CMDLINE 1
@@ -44,30 +42,19 @@
 #define MULTIBOOT_TAG_TYPE_EFI_BS 18
 #define MULTIBOOT_TAG_TYPE_EFI32_IH 19
 #define MULTIBOOT_TAG_TYPE_EFI64_IH 20
-#define MULTIBOOT_TAG_TYPE_LOAD_BASE_ADDRESS 21
-
-typedef struct {
-    u8 red;
-    u8 green;
-    u8 blue;
-} multiboot_color;
-
-#define MULTIBOOT_MEMORY_AVAILABLE 1
-#define MULTIBOOT_MEMORY_RESERVED 2
-#define MULTIBOOT_MEMORY_ACPI_RECLAIMABLE 3
-#define MULTIBOOT_MEMORY_NVS 4
-#define MULTIBOOT_MEMORY_BADRAM 5
+#define MULTIBOOT_TAG_TYPE_LOAD_BASE_ADDR 21
 
 typedef struct {
     u32 type;
     u32 size;
-} multiboot_tag;
+    char cmdline[0];
+} multiboot_tag_cmdline;
 
 typedef struct {
     u32 type;
     u32 size;
-    char string[0];
-} multiboot_tag_string;
+    char bootloader_name[0];
+} multiboot_tag_bootloader_name;
 
 typedef struct {
     u32 type;
@@ -92,8 +79,14 @@ typedef struct {
     u32 sub_partition;
 } multiboot_tag_bootdev;
 
+#define MULTIBOOT_MEMORY_AVAILABLE 1
+#define MULTIBOOT_MEMORY_RESERVED 2
+#define MULTIBOOT_MEMORY_ACPI_RECLAIMABLE 3
+#define MULTIBOOT_MEMORY_NVS 4
+#define MULTIBOOT_MEMORY_BADRAM 5
+
 typedef struct {
-    u64 base_address;
+    u64 base_addr;
     u64 length;
     u32 type;
     u32 reserved;
@@ -124,10 +117,16 @@ typedef struct {
 #define MULTIBOOT_FRAMEBUFFER_TYPE_RGB 1
 #define MULTIBOOT_FRAMEBUFFER_TYPE_EGA_TEXT 2
 
+typedef struct {
+    u8 red;
+    u8 green;
+    u8 blue;
+} multiboot_color;
+
 typedef struct {
     u32 type;
     u32 size;
-    u64 framebuffer_address;
+    u64 framebuffer_addr;
     u32 framebuffer_pitch;
     u32 framebuffer_width;
     u32 framebuffer_height;
@@ -199,13 +198,13 @@ typedef struct {
     u32 type;
     u32 size;
     u8 rsdp[0];
-} multiboot_tag_old_acpi;
+} multiboot_tag_acpi_old;
 
 typedef struct {
     u32 type;
     u32 size;
     u8 rsdp[0];
-} multiboot_tag_new_acpi;
+} multiboot_tag_acpi_new;
 
 typedef struct {
     u32 type;
@@ -236,5 +235,95 @@ typedef struct {
 typedef struct {
     u32 type;
     u32 size;
-    u32 load_base_address;
-} multiboot_tag_load_base_address;
+    u32 load_base_addr;
+} multiboot_tag_load_base_addr;
+
+void *multiboot_get_tag(u32 type);
+
+static inline multiboot_tag_cmdline *multiboot_get_cmdline() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_CMDLINE);
+}
+
+static inline multiboot_tag_bootloader_name *multiboot_get_bootloader_name() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_BOOT_LOADER_NAME);
+}
+
+static inline multiboot_tag_module *multiboot_get_module() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_MODULE);
+}
+
+static inline multiboot_tag_basic_meminfo *multiboot_get_basic_meminfo() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_BASIC_MEMINFO);
+}
+
+static inline multiboot_tag_bootdev *multiboot_get_bootdev() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_BOOTDEV);
+}
+
+static inline multiboot_tag_mmap *multiboot_get_mmap() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_MMAP);
+}
+
+static inline size_t get_mmap_entry_count(multiboot_tag_mmap *mmap) {
+    return (mmap->size - 16) / mmap->entry_size;
+}
+
+static inline multiboot_tag_vbe *multiboot_get_vbe() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_VBE);
+}
+
+static inline multiboot_tag_framebuffer *multiboot_get_framebuffer() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_FRAMEBUFFER);
+}
+
+static inline multiboot_tag_elf_sections *multiboot_get_elf_sections() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_ELF_SECTIONS);
+}
+
+static inline multiboot_tag_apm *multiboot_get_apm() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_APM);
+}
+
+static inline multiboot_tag_efi32 *multiboot_get_efi32() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_EFI32);
+}
+
+static inline multiboot_tag_efi64 *multiboot_get_efi64() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_EFI64);
+}
+
+static inline multiboot_tag_smbios *multiboot_get_smbios() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_SMBIOS);
+}
+
+static inline multiboot_tag_acpi_old *multiboot_get_acpi_old() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_ACPI_OLD);
+}
+
+static inline multiboot_tag_acpi_new *multiboot_get_acpi_new() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_ACPI_NEW);
+}
+
+static inline multiboot_tag_network *multiboot_get_network() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_NETWORK);
+}
+
+static inline multiboot_tag_efi_mmap *multiboot_get_efi_mmap() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_EFI_MMAP);
+}
+
+static inline bool multiboot_get_efi_bs() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_EFI_BS) != NULL;
+}
+
+static inline multiboot_tag_efi32_ih *multiboot_get_efi32_ih() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_EFI32_IH);
+}
+
+static inline multiboot_tag_efi64_ih *multiboot_get_efi64_ih() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_EFI64_IH);
+}
+
+static inline multiboot_tag_load_base_addr *multiboot_get_load_base_addr() {
+    return multiboot_get_tag(MULTIBOOT_TAG_TYPE_LOAD_BASE_ADDR);
+}

src/boot/pmm.c

@@ -0,0 +1,116 @@
+#include "pmm.h"
+#include "util.h"
+#include "panic.h"
+#include "multiboot2.h"
+#include "symbols.h"
+#include <def.h>
+
+#define PAGE_SIZE 4096
+#define MAX_PHYS_MEM  GiB(128)
+#define MAX_PAGES (MAX_PHYS_MEM / PAGE_SIZE)
+#define BITMAP_SIZE ((MAX_PAGES + 63) / 64)
+
+static u64 pmm_bitmap[BITMAP_SIZE];
+
+static inline void bitmap_set(size_t bit) {
+    pmm_bitmap[bit / 64] |=  (1ULL << (bit % 64));
+}
+
+static inline void bitmap_clear(size_t bit) {
+    pmm_bitmap[bit / 64] &= ~(1ULL << (bit % 64));
+}
+
+static inline int bitmap_test(size_t bit) {
+    return pmm_bitmap[bit / 64] & (1ULL << (bit % 64));
+}
+
+static inline size_t to_page(uptr addr) {
+    if (addr % PAGE_SIZE != 0) {
+        boot_panic("Address is not page aligned");
+    }
+
+    return addr / PAGE_SIZE;
+}
+
+static inline uptr to_addr(size_t page) {
+    return page * PAGE_SIZE;
+}
+
+static void clear_range(size_t start_page, size_t end_page) {
+    if (start_page >= MAX_PAGES) {
+        return;
+    }
+
+    if (end_page > MAX_PAGES) {
+        end_page = MAX_PAGES;
+    }
+
+    for (size_t j = start_page; j < end_page; ++j) {
+        bitmap_clear(j);
+    }
+}
+
+static void set_range(size_t start_page, size_t end_page) {
+    if (start_page >= MAX_PAGES) {
+        return;
+    }
+
+    if (end_page > MAX_PAGES) {
+        end_page = MAX_PAGES;
+    }
+
+    for (size_t j = start_page; j < end_page; ++j) {
+        bitmap_set(j);
+    }
+}
+
+void pmm_init() {
+    for (size_t i = 0; i < BITMAP_SIZE; i++) {
+        pmm_bitmap[i] = U64_MAX;
+    }
+
+    multiboot_tag_mmap *mmap = multiboot_get_mmap();
+    if (mmap == NULL) {
+        boot_panic("No memory map found");
+    }
+
+    for (size_t i = 0; i < get_mmap_entry_count(mmap); ++i) {
+        multiboot_mmap_entry entry = mmap->entries[i];
+        if (entry.type == MULTIBOOT_MEMORY_AVAILABLE) {
+            size_t start_page = to_page(ALIGN_DOWN(entry.base_addr, PAGE_SIZE));
+            size_t end_page = to_page(ALIGN_UP(entry.base_addr + entry.length, PAGE_SIZE));
+
+            clear_range(start_page, end_page);
+        }
+    }
+
+    size_t start_page = to_page(ALIGN_DOWN(get_kernel_start(), PAGE_SIZE));
+    size_t end_page = to_page(ALIGN_UP(get_kernel_end(), PAGE_SIZE));
+
+    set_range(start_page, end_page);
+}
+
+void *pmm_alloc_page() {
+    for (size_t i = 0; i < MAX_PAGES; ++i) {
+        if (!bitmap_test(i)) {
+            bitmap_set(i);
+            return (void*)to_addr(i);
+        }
+    }
+
+    boot_panic("Out of physical memory");
+}
+
+void pmm_free_page(void *addr) {
+    size_t page = to_page((uptr)addr);
+
+    if (page >= MAX_PAGES) {
+        boot_panic("Trying to free page beyond physical memory limit");
+    }
+
+    if (!bitmap_test(page)) {
+        boot_panic("Page is already free");
+    }
+
+    bitmap_clear(page);
+}

src/boot/pmm.h

@@ -0,0 +1,5 @@
+#pragma once
+
+void pmm_init();
+void *pmm_alloc_page();
+void pmm_free_page(void *addr);

src/boot/start.asm

@@ -1,7 +1,8 @@
 global _start
+global multiboot_info
 extern kernel_start
 extern kernel_end
-extern kmain
+extern x86_64_main
 
 %define MAGIC   0xe85250d6
 %define ARCH    0x0
@@ -21,10 +22,6 @@ header:
         dd 8
     .end:
 
-section .data
-align 8
-multiboot_info: dq 0
-
 %define PRESENT     1 << 7
 %define NOT_SYS     1 << 4
 %define EXEC        1 << 3
@@ -58,6 +55,11 @@ gdt:
         dq gdt
 
 section .bss
+%define MULTIBOOT_INFO_MAX_SIZE 1024 * 64
+
+align 8
+multiboot_info: resb MULTIBOOT_INFO_MAX_SIZE
+
 align 16
 stack:
     .bottom:
@@ -79,29 +81,38 @@ _start:
     cmp eax, BOOTLOADER_MAGIC
     jne .halt
 
-    ; Save pointer to info gathered by multiboot
-    mov [multiboot_info], ebx
+    ; Copy multiboot structure to kernel owned memory
+    mov esi, ebx
+    mov eax, [esi]
+
+    cmp eax, MULTIBOOT_INFO_MAX_SIZE
+    ja .halt
+
+    mov edi, multiboot_info
+    mov ecx, eax
+    cld
+    rep movsb
 
     ; Tell the cpu where the pages area
     mov edi, pml4t
     mov cr3, edi
 
-    %define PT_PRESENT      1
-    %define PT_READABLE     2
+    %define PT_PRESENT  1
+    %define PT_RW       2
 
     ; pml4t[0] -> pdpt
     mov edi, pdpt
-    or edi, PT_PRESENT | PT_READABLE
+    or edi, PT_PRESENT | PT_RW
     mov [pml4t], edi
 
     ; pdpt[0] -> pdt
     mov edi, pdt
-    or edi, PT_PRESENT | PT_READABLE
+    or edi, PT_PRESENT | PT_RW
     mov [pdpt], edi
 
     ; pdt[0] -> pt
     mov edi, pt
-    or edi, PT_PRESENT | PT_READABLE
+    or edi, PT_PRESENT | PT_RW
     mov [pdt], edi
 
     %define ENTRIES_PER_PT  512
@@ -113,7 +124,7 @@ _start:
     mov edi, pt
     mov ebx, kernel_start
     and ebx, 0xfffff000
-    or ebx, PT_PRESENT | PT_READABLE
+    or ebx, PT_PRESENT | PT_RW
 
     mov eax, kernel_end
     sub eax, kernel_start
@@ -127,6 +138,17 @@ _start:
     add edi, SIZEOF_PT_ENTRY
     loop .set_pt_entry
 
+    ; note(nub31): Vga buffer is already page aligned
+    %define VGA_BUFFER 0xb8000
+
+    ; Identity map vga buffer
+    mov ebx, VGA_BUFFER
+    or ebx, PT_PRESENT | PT_RW
+
+    mov edi, pt
+    add edi, VGA_BUFFER / PAGE_SIZE * SIZEOF_PT_ENTRY
+    mov [edi], ebx
+
     %define CR4_PAE_ENABLE  1 << 5
 
     ; Enable pae
@@ -169,8 +191,8 @@ start64:
     mov ss, ax
 
     mov rsp, stack.top
-    mov rdi, [multiboot_info]
-    call kmain
+    mov rdi, multiboot_info
+    call x86_64_main
 .halt:
     cli
     hlt

src/boot/symbols.c

@@ -0,0 +1,19 @@
+#include "symbols.h"
+
+extern u8 kernel_start[];
+
+uptr get_kernel_start() {
+    return (uptr)&kernel_start;
+}
+
+extern u8 kernel_end[];
+
+uptr get_kernel_end() {
+    return (uptr)&kernel_end;
+}
+
+extern u8 multiboot_info[];
+
+uptr get_multiboot_info() {
+    return (uptr)&multiboot_info;
+}

src/boot/symbols.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#include <def.h>
+
+uptr get_kernel_start();
+uptr get_kernel_end();
+uptr get_multiboot_info();

src/boot/util.h

@@ -1,8 +1,9 @@
 #pragma once
 
-static inline u32 align(u32 num, u32 alignment) {
-    return (num + alignment - 1) & ~(alignment - 1);
-}
+#include <def.h>
+
+#define ALIGN_UP(value, alignment) ((value + alignment - 1) / alignment * alignment)
+#define ALIGN_DOWN(value, alignment) (value - (value % alignment))
 
 static inline void hlt() {
     asm("hlt");

src/shared/def.h

@@ -53,19 +53,7 @@ typedef signed long long i64;
 #define U64_MIN 0x0
 #define U64_MAX 0xffffffffffffffffULL
 
-#define I8_C(x) x
-#define U8_C(x) x##U
-
-#define I16_C(x) x
-#define U16_C(x) x##U
-
-#define I32_C(x) x
-#define U32_C(x) x##U
-
-#define I64_C(x) x##LL
-#define U64_C(x) x##ULL
-
-#define KiB(count) (U64_C(count) * U64_C(1024))
-#define MiB(count) (U64_C(count) * U64_C(1024) * U64_C(1024))
-#define GiB(count) (U64_C(count) * U64_C(1024) * U64_C(1024) * U64_C(1024))
-#define TiB(count) (U64_C(count) * U64_C(1024) * U64_C(1024) * U64_C(1024) * U64_C(1024))
+#define KiB(count) (count##ULL * 1024##ULL)
+#define MiB(count) (count##ULL * KiB(1024))
+#define GiB(count) (count##ULL * MiB(1024))
+#define TiB(count) (count##ULL * GiB(1024))

src/shared/string.c

@@ -83,55 +83,25 @@ void itoa64(i64 value, char *buffer) {
 }
 
 void uitoa64(u64 value, char *buffer) {
-    char *p = buffer;
+    char tmp[20];
+    int i = 0;
 
     if (value == 0) {
-        *p++ = '0';
-        *p = '\0';
+        buffer[0] = '0';
+        buffer[1] = '\0';
         return;
     }
 
-    static const u64 powers[] = {
-        10000000000000000000ULL,
-        1000000000000000000ULL,
-        100000000000000000ULL,
-        10000000000000000ULL,
-        1000000000000000ULL,
-        100000000000000ULL,
-        10000000000000ULL,
-        1000000000000ULL,
-        100000000000ULL,
-        10000000000ULL,
-        1000000000ULL,
-        100000000ULL,
-        10000000ULL,
-        1000000ULL,
-        100000ULL,
-        10000ULL,
-        1000ULL,
-        100ULL,
-        10ULL,
-        1ULL
-    };
-
-    bool started = false;
-
-    for (int i = 0; i < 20; i++) {
-        u64 power = powers[i];
-        u32 digit = 0;
-
-        while (value >= power) {
-            value -= power;
-            digit++;
-        }
-
-        if (digit || started) {
-            *p++ = '0' + digit;
-            started = true;
-        }
+    while (value > 0) {
+        tmp[i++] = '0' + (value % 10);
+        value /= 10;
     }
 
-    *p = '\0';
+    for (int j = 0; j < i; j++) {
+        buffer[j] = tmp[i - j - 1];
+    }
+
+    buffer[i] = '\0';
 }
 
 void uitoa64_hex(u64 value, char *buffer) {