diff --git a/compile_flags.txt b/compile_flags.txt
index 571b7e0..fcfc9aa 100644
--- a/compile_flags.txt
+++ b/compile_flags.txt
@@ -2,21 +2,24 @@
 -Wall
 -Wextra
 -Werror
--D__ck_loader_limine__
+-Isrc/libs
+-Isrc/kernel/klibs
+-Isrc/kernel/archs
 -D__ck_toolchain_value=clang
--D__ck_encoding_utf8__
--D__ck_sys_kernel__
--D__ck_freestanding__
 -D__ck_loader_value=limine
 -D__ck_encoding_value=utf8
--D__ck_arch_x86_64__
+-D__ck_bits_64__
 -D__ck_toolchain_clang__
--D__ck_bits_value=64
--D__ck_abi_sysv__
 -D__ck_abi_value=sysv
 -D__ck_sys_value=kernel
+-D__ck_loader_limine__
+-D__ck_sys_kernel__
+-D__ck_encoding_utf8__
+-D__ck_abi_sysv__
+-D__ck_freestanding__
 -D__ck_arch_value=x86_64
--D__ck_bits_64__
+-D__ck_bits_value=64
+-D__ck_arch_x86_64__
 -ffreestanding
 -fno-stack-protector
 -mno-80387
@@ -26,3 +29,4 @@
 -mno-sse2
 -mno-red-zone
 -Dauto=__auto_type
+-Isrc/kernel/klibs
diff --git a/src/kernel/archs/hal.h b/src/kernel/archs/hal.h
new file mode 100644
index 0000000..879d8f0
--- /dev/null
+++ b/src/kernel/archs/hal.h
@@ -0,0 +1,19 @@
+#pragma once
+
+#include <io/stream.h>
+
+void hal_setup(void);
+
+/* --- Assembly function --------------------------------------------------- */
+
+void hal_disable_interrupts(void);
+
+void hal_enable_interrupts(void);
+
+void hal_pause(void);
+
+void hal_panic(void);
+
+/* --- I/O ----------------------------------------------------------------  */
+
+Stream hal_dbg_stream(void);
\ No newline at end of file
diff --git a/src/kernel/archs/x86_64/asm.c b/src/kernel/archs/x86_64/asm.c
new file mode 100644
index 0000000..a8b4c4f
--- /dev/null
+++ b/src/kernel/archs/x86_64/asm.c
@@ -0,0 +1,19 @@
+void hal_disable_interrupts(void)
+{
+    asm volatile("cli");
+}
+
+void hal_enable_interrupts(void)
+{
+    asm volatile("sti");
+}
+
+void hal_pause(void)
+{
+    asm volatile("pause");
+}
+
+void hal_panic(void)
+{
+    asm volatile("int $1");
+}
diff --git a/src/kernel/archs/x86_64/e9.c b/src/kernel/archs/x86_64/e9.c
new file mode 100644
index 0000000..547fb70
--- /dev/null
+++ b/src/kernel/archs/x86_64/e9.c
@@ -0,0 +1,19 @@
+#include <res.h>
+
+#include "e9.h"
+
+Res e9_putc(char c)
+{
+    asm volatile("outb %0, $0xe9" : : "a"(c) : "memory");
+    return ok$();
+}
+
+Res e9_puts(size_t n, char const *s)
+{
+    for (size_t i = 0; i < n; i++)
+    {
+        e9_putc(s[i]);
+    }
+
+    return ok$();
+}
\ No newline at end of file
diff --git a/src/kernel/archs/x86_64/e9.h b/src/kernel/archs/x86_64/e9.h
new file mode 100644
index 0000000..9218d5f
--- /dev/null
+++ b/src/kernel/archs/x86_64/e9.h
@@ -0,0 +1,7 @@
+#pragma once
+
+#include <res.h>
+
+Res e9_putc(char c);
+
+Res e9_puts(size_t n, char const *s);
\ No newline at end of file
diff --git a/src/kernel/archs/x86_64/manifest.json b/src/kernel/archs/x86_64/manifest.json
new file mode 100644
index 0000000..027cde4
--- /dev/null
+++ b/src/kernel/archs/x86_64/manifest.json
@@ -0,0 +1,16 @@
+{
+    "$schema": "https://schemas.cute.engineering/stable/cutekit.manifest.component.v1",
+    "type": "lib",
+    "id": "arch (x86_64)",
+    "enableIf": {
+        "arch": [
+            "x86_64"
+        ]
+    },
+    "provides": [
+        "arch"
+    ],
+    "requires": [
+        "dbg"
+    ]
+}
\ No newline at end of file
diff --git a/src/kernel/archs/x86_64/mod.c b/src/kernel/archs/x86_64/mod.c
new file mode 100644
index 0000000..9951b8f
--- /dev/null
+++ b/src/kernel/archs/x86_64/mod.c
@@ -0,0 +1,14 @@
+#include <io/stream.h>
+
+#include "e9.h"
+
+Stream hal_dbg_stream(void)
+{
+    return (Stream){
+        .write = e9_puts,
+    };
+}
+
+void hal_setup(void)
+{
+}
\ No newline at end of file
diff --git a/src/kernel/core/main.c b/src/kernel/core/main.c
index 84392b7..10f157b 100644
--- a/src/kernel/core/main.c
+++ b/src/kernel/core/main.c
@@ -1,5 +1,8 @@
+#include <dbg/log.h>
+
 _Noreturn int _start()
 {
+    log$("Hello, world!");
     for (;;)
         ;
 }
\ No newline at end of file
diff --git a/src/kernel/core/manifest.json b/src/kernel/core/manifest.json
index 804a88b..28739c4 100644
--- a/src/kernel/core/manifest.json
+++ b/src/kernel/core/manifest.json
@@ -1,5 +1,17 @@
 {
     "$schema": "https://schemas.cute.engineering/stable/cutekit.manifest.component.v1",
     "type": "exe",
-    "id": "core"
+    "id": "core",
+    "requires": [
+        "arch",
+        "dbg",
+        "stdc-shim"
+    ],
+    "tools": {
+        "cc": {
+            "args": [
+                "-Isrc/kernel/klibs"
+            ]
+        }
+    }
 }
\ No newline at end of file
diff --git a/src/kernel/klibs/dbg/log.c b/src/kernel/klibs/dbg/log.c
new file mode 100644
index 0000000..cb7f7ad
--- /dev/null
+++ b/src/kernel/klibs/dbg/log.c
@@ -0,0 +1,46 @@
+#include <fmt/fmt.h>
+#include <hal.h>
+#include <stdarg.h>
+#include <sync/spinlock.h>
+
+#include "log.h"
+
+static Spinlock _lock = SPINLOCK_INIT;
+
+static char const *level_names[LOG_EVENT_LENGTH] = {
+    [LOG_NONE] = "",
+    [LOG_INFO] = "INFO",
+    [LOG_WARN] = "WARN",
+    [LOG_ERROR] = "ERROR",
+    [LOG_CRIT] = "CRITIC",
+};
+
+static char const *level_colors[LOG_EVENT_LENGTH] = {
+    [LOG_NONE] = "",
+    [LOG_INFO] = "\e[1;34m",
+    [LOG_WARN] = "\e[1;33m",
+    [LOG_ERROR] = "\e[1;31m",
+    [LOG_CRIT] = "\e[1;35m",
+};
+
+void _log(LogEvent event, Loc loc, char const *format, ...)
+{
+    spinlock_acquire(&_lock);
+    va_list args;
+    va_start(args, format);
+
+    if (event != LOG_NONE)
+    {
+        fmt(hal_dbg_stream(), "%s%s\e[0m %s:%d ", level_colors[event], level_names[event], loc.file, loc.line);
+    }
+
+    vfmt(hal_dbg_stream(), format, args);
+
+    if (event != LOG_NONE)
+    {
+        hal_dbg_stream().write(1, "\n");
+    }
+
+    va_end(args);
+    spinlock_release(&_lock);
+}
\ No newline at end of file
diff --git a/src/kernel/klibs/dbg/log.h b/src/kernel/klibs/dbg/log.h
new file mode 100644
index 0000000..3c4ea29
--- /dev/null
+++ b/src/kernel/klibs/dbg/log.h
@@ -0,0 +1,24 @@
+#pragma once
+
+#include <io/stream.h>
+
+#include "loc.h"
+
+typedef enum
+{
+    LOG_NONE,
+    LOG_INFO,
+    LOG_WARN,
+    LOG_ERROR,
+    LOG_CRIT,
+
+    LOG_EVENT_LENGTH
+} LogEvent;
+
+#define log$(...)      _log(LOG_INFO, loc$(), __VA_ARGS__)
+#define warn$(...)     _log(LOG_WARN, loc$(), __VA_ARGS__)
+#define error$(...)    _log(LOG_ERROR, loc$(), __VA_ARGS__)
+#define critical$(...) _log(LOG_CRIT, loc$(), __VA_ARGS__)
+#define print$(...)    _log(LOG_NONE, (Loc){}, __VA_ARGS__)
+
+void _log(LogEvent event, Loc loc, char const *format, ...);
\ No newline at end of file
diff --git a/src/kernel/klibs/dbg/manifest.json b/src/kernel/klibs/dbg/manifest.json
new file mode 100644
index 0000000..2bca110
--- /dev/null
+++ b/src/kernel/klibs/dbg/manifest.json
@@ -0,0 +1,14 @@
+{
+    "$schema": "https://schemas.cute.engineering/stable/cutekit.manifest.component.v1",
+    "type": "lib",
+    "id": "dbg",
+    "enableIf": {
+        "freestanding": [
+            true
+        ]
+    },
+    "requires": [
+        "sync",
+        "fmt"
+    ]
+}
\ No newline at end of file
diff --git a/src/kernel/klibs/stdc-shim/manifest.json b/src/kernel/klibs/stdc-shim/manifest.json
new file mode 100644
index 0000000..2c80d77
--- /dev/null
+++ b/src/kernel/klibs/stdc-shim/manifest.json
@@ -0,0 +1,13 @@
+{
+    "$schema": "https://schemas.cute.engineering/stable/cutekit.manifest.component.v1",
+    "type": "lib",
+    "id": "stdc-shim",
+    "props": {
+        "cpp-root-include": true
+    },
+    "enableIf": {
+        "freestanding": [
+            true
+        ]
+    }
+}
\ No newline at end of file
diff --git a/src/kernel/klibs/stdc-shim/string.c b/src/kernel/klibs/stdc-shim/string.c
new file mode 100644
index 0000000..87605db
--- /dev/null
+++ b/src/kernel/klibs/stdc-shim/string.c
@@ -0,0 +1,51 @@
+#include "string.h"
+
+size_t strlen(char const str[static 1])
+{
+    size_t len = 0;
+
+    while (*str++)
+    {
+        len++;
+    }
+
+    return len;
+}
+
+void *memcpy(void *restrict dst, void const *restrict src, size_t n)
+{
+    char *restrict d = dst;
+    char const *restrict s = src;
+
+    while (n--)
+    {
+        *d++ = *s++;
+    }
+
+    return dst;
+}
+
+void *memset(void *dest, int c, size_t n)
+{
+    char *d = dest;
+
+    while (n--)
+    {
+        *d++ = c;
+    }
+
+    return dest;
+}
+
+int memcmp(const void *s1, const void *s2, size_t n)
+{
+    for (size_t i = 0; i < n; i++)
+    {
+        if (((const char *)s1)[i] != ((const char *)s2)[i])
+        {
+            return ((const char *)s1)[i] - ((const char *)s2)[i];
+        }
+    }
+
+    return 0;
+}
\ No newline at end of file
diff --git a/src/kernel/klibs/stdc-shim/string.h b/src/kernel/klibs/stdc-shim/string.h
new file mode 100644
index 0000000..2776ce9
--- /dev/null
+++ b/src/kernel/klibs/stdc-shim/string.h
@@ -0,0 +1,11 @@
+#pragma once
+
+#include <stddef.h>
+
+size_t strlen(char const s[static 1]);
+
+void *memcpy(void *restrict dest, void const *restrict src, size_t n);
+
+void *memset(void *dest, int c, size_t n);
+
+int memcmp(void const *s1, void const *s2, size_t n);
\ No newline at end of file
diff --git a/src/kernel/klibs/sync/manifest.json b/src/kernel/klibs/sync/manifest.json
new file mode 100644
index 0000000..1372208
--- /dev/null
+++ b/src/kernel/klibs/sync/manifest.json
@@ -0,0 +1,10 @@
+{
+    "$schema": "https://schemas.cute.engineering/stable/cutekit.manifest.component.v1",
+    "type": "lib",
+    "id": "sync",
+    "enableIf": {
+        "freestanding": [
+            true
+        ]
+    }
+}
\ No newline at end of file
diff --git a/src/kernel/klibs/sync/spinlock.c b/src/kernel/klibs/sync/spinlock.c
new file mode 100644
index 0000000..5fdb312
--- /dev/null
+++ b/src/kernel/klibs/sync/spinlock.c
@@ -0,0 +1,30 @@
+#include <hal.h>
+
+#include "spinlock.h"
+
+static _Atomic int retain_count = 0;
+
+static void retain_interrupts(void)
+{
+    retain_count++;
+}
+
+static void release_interrupt(void)
+{
+    retain_count--;
+}
+
+void spinlock_acquire(Spinlock spinlock[static 1])
+{
+    retain_interrupts();
+    while (atomic_flag_test_and_set(&spinlock->lock))
+    {
+        hal_pause();
+    }
+}
+
+void spinlock_release(Spinlock spinlock[static 1])
+{
+    atomic_flag_clear(&spinlock->lock);
+    release_interrupt();
+}
\ No newline at end of file
diff --git a/src/kernel/klibs/sync/spinlock.h b/src/kernel/klibs/sync/spinlock.h
new file mode 100644
index 0000000..e03dd71
--- /dev/null
+++ b/src/kernel/klibs/sync/spinlock.h
@@ -0,0 +1,17 @@
+#pragma once
+
+#include <stdatomic.h>
+
+typedef struct
+{
+    volatile atomic_flag lock;
+} Spinlock;
+
+#define SPINLOCK_INIT \
+    (Spinlock) { .lock = ATOMIC_FLAG_INIT }
+
+Spinlock spinlock_new(void);
+
+void spinlock_acquire(Spinlock spinlock[static 1]);
+
+void spinlock_release(Spinlock spinlock[static 1]);
\ No newline at end of file
diff --git a/src/libs/fmt/fmt.c b/src/libs/fmt/fmt.c
new file mode 100644
index 0000000..9151c1d
--- /dev/null
+++ b/src/libs/fmt/fmt.c
@@ -0,0 +1,191 @@
+#include <stdint.h>
+#include <string.h>
+
+#include "fmt.h"
+
+static char *strrev(char *str)
+{
+    int start;
+    int end;
+    char tmp;
+
+    end = strlen(str) - 1;
+    start = 0;
+
+    while (start < end)
+    {
+        tmp = str[start];
+        str[start] = str[end];
+        str[end] = tmp;
+        start++;
+        end--;
+    }
+    return str;
+}
+
+static char *itoa(int64_t value, char *str, int base)
+{
+    int i = 0;
+    bool isNegative = false;
+
+    if (value == 0)
+    {
+        str[i++] = '0';
+        str[i] = '\0';
+        return str;
+    }
+
+    if (value < 0 && base == 10)
+    {
+        isNegative = true;
+        value = -value;
+    }
+
+    while (value != 0)
+    {
+        int rem = value % base;
+        str[i++] = (rem > 9) ? (rem - 10) + 'a' : rem + '0';
+        value = value / base;
+    }
+
+    if (isNegative)
+    {
+        str[i++] = '-';
+    }
+
+    str[i] = '\0';
+
+    return strrev(str);
+}
+
+char *utoa(uint64_t value, char *str, int base)
+{
+    int i = 0;
+
+    if (value == 0)
+    {
+        str[i++] = '0';
+        str[i] = '\0';
+        return str;
+    }
+
+    while (value != 0)
+    {
+        int rem = value % base;
+        str[i++] = (rem > 9) ? (rem - 10) + 'a' : rem + '0';
+        value = value / base;
+    }
+
+    str[i] = '\0';
+
+    return strrev(str);
+}
+
+Res fmt(Stream stream, char const fmt[static 1], ...)
+{
+    va_list args;
+    va_start(args, fmt);
+    Res res = vfmt(stream, fmt, args);
+    va_end(args);
+    return res;
+}
+
+Res vfmt(Stream stream, char const fmt[static 1], va_list args)
+{
+    const char *s = fmt;
+
+    while (*s)
+    {
+        if (*s == '%')
+        {
+            switch (*++s)
+            {
+                case 'd':
+                {
+                    s++;
+                    char buf[100];
+                    int64_t value = va_arg(args, int64_t);
+
+                    itoa(value, buf, 10);
+                    stream.write(strlen(buf), buf);
+                    break;
+                }
+
+                case 'u':
+                {
+                    s++;
+                    char buf[100];
+                    uint64_t value = va_arg(args, int64_t);
+
+                    utoa(value, buf, 10);
+                    stream.write(strlen(buf), buf);
+                    break;
+                }
+
+                case 'p':
+                {
+                    s++;
+                    char buf[100];
+                    uint64_t value = va_arg(args, uint64_t);
+
+                    utoa(value, buf, 16);
+                    stream.write(2, "0x");
+
+                    for (size_t i = 0; i < 16 - strlen(buf); i++)
+                    {
+                        stream.write(1, "0");
+                    }
+
+                    stream.write(strlen(buf), buf);
+                    break;
+                }
+
+                case 'x':
+                {
+                    s++;
+                    char buf[100];
+                    uint64_t value = va_arg(args, uint64_t);
+
+                    utoa(value, buf, 16);
+                    stream.write(strlen(buf), buf);
+                    break;
+                }
+
+                case 's':
+                {
+                    s++;
+                    char *value = va_arg(args, char *);
+                    stream.write(strlen(value), value);
+                    break;
+                }
+
+                case 'c':
+                {
+                    s++;
+                    char value = va_arg(args, int);
+                    stream.write(1, &value);
+                    break;
+                }
+
+                case '%':
+                {
+                    s++;
+                    stream.write(1, "%");
+                    break;
+                }
+
+                default:
+                {
+                    return err$(RES_INVAL);
+                }
+            }
+        }
+        else
+        {
+            char sub[2] = {*s++, '\0'};
+            stream.write(1, sub);
+        }
+    }
+
+    return uok$(0);
+}
\ No newline at end of file
diff --git a/src/libs/fmt/fmt.h b/src/libs/fmt/fmt.h
new file mode 100644
index 0000000..280c0f1
--- /dev/null
+++ b/src/libs/fmt/fmt.h
@@ -0,0 +1,8 @@
+#pragma once
+
+#include <io/stream.h>
+#include <res.h>
+#include <stdarg.h>
+
+Res fmt(Stream stream, char const fmt[static 1], ...);
+Res vfmt(Stream stream, char const fmt[static 1], va_list args);
\ No newline at end of file
diff --git a/src/libs/fmt/manifest.json b/src/libs/fmt/manifest.json
new file mode 100644
index 0000000..1be8a38
--- /dev/null
+++ b/src/libs/fmt/manifest.json
@@ -0,0 +1,5 @@
+{
+    "$schema": "https://schemas.cute.engineering/stable/cutekit.manifest.component.v1",
+    "type": "lib",
+    "id": "fmt"
+}
\ No newline at end of file
diff --git a/src/libs/io/manifest.json b/src/libs/io/manifest.json
new file mode 100644
index 0000000..c05276c
--- /dev/null
+++ b/src/libs/io/manifest.json
@@ -0,0 +1,5 @@
+{
+    "$schema": "https://schemas.cute.engineering/stable/cutekit.manifest.component.v1",
+    "type": "lib",
+    "id": "io"
+}
\ No newline at end of file
diff --git a/src/libs/io/stream.h b/src/libs/io/stream.h
new file mode 100644
index 0000000..b152c3d
--- /dev/null
+++ b/src/libs/io/stream.h
@@ -0,0 +1,9 @@
+#pragma once
+
+#include "res.h"
+
+typedef struct
+{
+    Res (*write)(size_t n, char const buf[static n]);
+    Res (*read)(size_t n, char buf[static n]);
+} Stream;
\ No newline at end of file
diff --git a/src/libs/loc.h b/src/libs/loc.h
new file mode 100644
index 0000000..fdf16d6
--- /dev/null
+++ b/src/libs/loc.h
@@ -0,0 +1,18 @@
+#pragma once
+
+#include <stddef.h>
+
+typedef struct
+{
+    char const *file;
+    const char *full;
+    const char *func;
+    size_t line;
+} Loc;
+
+#define loc$() ((Loc){     \
+    .file = __FILE_NAME__, \
+    .full = __FILE__,      \
+    .func = __func__,      \
+    .line = __LINE__,      \
+})
\ No newline at end of file
diff --git a/src/libs/res.h b/src/libs/res.h
new file mode 100644
index 0000000..b3e8efd
--- /dev/null
+++ b/src/libs/res.h
@@ -0,0 +1,56 @@
+#pragma once
+
+#include <stddef.h>
+
+#include "loc.h"
+#include "utils.h"
+
+#define RES_TYPE(F) \
+    F(RES_OK)       \
+    F(RES_INVAL)    \
+    F(RES_NOMEM)    \
+    F(RES_BADALIGN) \
+    F(RES_NOENT)
+
+enum res_type
+{
+    RES_TYPE(make_enum$)
+};
+
+static char const *res_type_str[] = {RES_TYPE(make_str$)};
+
+typedef struct
+{
+    enum res_type type;
+    Loc loc;
+    union
+    {
+        size_t uvalue;
+        ptrdiff_t ivalue;
+    };
+} Res;
+
+#define ok$() \
+    (Res) { .type = RES_OK, .uvalue = 0, .loc = loc$() }
+
+#define uok$(u) \
+    (Res) { .type = RES_OK, .uvalue = (u), .loc = loc$() }
+
+#define iok$(i) \
+    (Res) { .type = RES_OK, .ivalue = (i), .loc = loc$() }
+
+#define err$(t) \
+    (Res) { .type = (t), .uvalue = 0, .loc = loc$() }
+
+#define try$(EXPR)                   \
+    ({                               \
+        Res __result = (Res)(EXPR);  \
+        if (__result.type != RES_OK) \
+            return __result;         \
+        __result.ivalue;             \
+    })
+
+static inline char const *res_to_str(Res res)
+{
+    return res_type_str[res.type];
+}
\ No newline at end of file
diff --git a/src/libs/utils.h b/src/libs/utils.h
new file mode 100644
index 0000000..88dccd8
--- /dev/null
+++ b/src/libs/utils.h
@@ -0,0 +1,9 @@
+#pragma once
+
+#define max$(a, b) (((a) > (b)) ? (a) : (b))
+
+#define min$(a, b) (((a) < (b)) ? (a) : (b))
+
+#define make_enum$(enum) enum,
+
+#define make_str$(str) #str,
\ No newline at end of file