feat(userspace): userspace support

build: updated CMakeLists to build and copy to initramfs

wip(syscalls): initial syscalls

chore(ksh/kfetch): minor changes

chore(gitignore): added initramfs/*

.gitignore

@@ -1,4 +1,5 @@
 .cache
 build*
 .venv
-initrd/image.cpio
+initrd/image.cpio
+initramfs/*

CMakeLists.txt

@@ -28,6 +28,7 @@ add_compile_definitions(TERMOS_VERSION=\"${KERNEL_VERSION}\")
 
 add_subdirectory(bootloader)
 add_subdirectory(kernel)
+add_subdirectory(userspace)
 
 if(MCOPY_EXE AND MKFS_EXE AND CPIO_EXE)
     set(IMG_FILE "${CMAKE_BINARY_DIR}/termOS.img")
@@ -41,7 +42,7 @@ if(MCOPY_EXE AND MKFS_EXE AND CPIO_EXE)
         COMMAND ${CMAKE_COMMAND} -E make_directory ${CMAKE_BINARY_DIR}
         COMMAND sh -c "find . -mindepth 1 ! -name '*.cpio' -print0 | ${CPIO_EXE} --null -ov -H newc > \"${INITRAMFS_CPIO_FILE}\""
         WORKING_DIRECTORY ${INITRAMFS_SRC_DIR}
-        DEPENDS ${INIT_FILES}
+        DEPENDS ${INIT_FILES} init
         VERBATIM
         COMMENT "Packing initramfs to cpio..."
     )

initramfs/test.txt

@@ -1 +0,0 @@
-Meow!!

initramfs/test1.txt

@@ -1 +0,0 @@
-Nyaaa

kernel/inc/arch/x86_64/cpuinfo.h

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 // Copyright (c) 2026 0xKarinyash
-
+#pragma once
 #include <types.h>
 
 #define CPU_FEAT_FPU      (1ULL << 0)
@@ -24,7 +24,11 @@
 #define CPU_FEAT_HYPERVISOR (1ULL << 30) 
 
 typedef struct {
-    i32 features;
+    u64 user_rsp;
+    u64 kernel_rsp;
+    u64 self;
+
+    u64 features;
     char vendor[13];
     u32 family;
     u32 model;
@@ -32,5 +36,5 @@ typedef struct {
 
 extern cpu_info g_cpu;
 
-void cpuinfo_init();
+void cpuinfo_init(u64 kernel_stack_top);
 bool cpu_has(u64 feature);

kernel/inc/arch/x86_64/syscall.h

@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Copyright (c) 2026 0xKarinyash
+
+#pragma once
+
+#define MSR_EFER         0xC0000080
+#define MSR_STAR         0xC0000081
+#define MSR_LSTAR        0xC0000082
+#define MSR_FMASK        0xC0000084
+#define MSR_KERNEL_GS_BASE 0xC0000102
+
+#define EFER_SCE         0x01 // System Call Enable
+
+typedef enum {
+    SYS_EXIT,
+    SYS_EXEC,
+    SYS_WRITE,
+} syscalls;
+
+void syscall_init();

kernel/inc/core/loader.h

@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Copyright (c) 2026 0xKarinyash
+
+#pragma once
+
+#include <types.h>
+
+bool exec_init(const char* path);
+void init_task_entry();

kernel/inc/core/userspace.h

@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Copyright (c) 2026 0xKarinyash
+
+#pragma once
+
+void jump_to_userspace(void* entry, void* user_stack_top);

kernel/inc/drivers/shitgui.h

@@ -26,16 +26,8 @@ typedef struct {
     const unsigned char* base;
 } SG_Font;
 
-typedef struct {
-    SG_Context *ctx;
-    SG_Point pos;
-    const char *title;
-} SG_Window;
-
 void sg_init(SG_Context *ctx);
 u32 sg_get_pixel(SG_Context *ctx, SG_Point *p);
 void sg_put_img(SG_Context *ctx, SG_Point *p, SG_Image *img);
 void sg_draw_rect(SG_Context *ctx, SG_Point *p, u32 w, u32 h, u32 color);
-void sg_draw_char_bitmap(SG_Context *ctx, SG_Point *p, char c, u32 color, SG_Font *font);
-SG_Window* create_window(const char *title, SG_Point* size, SG_Point* position);
-void composer_task();
+void sg_draw_char_bitmap(SG_Context *ctx, SG_Point *p, char c, u32 color, SG_Font *font);

kernel/src/arch/x86_64/cpuinfo.c

@@ -4,6 +4,9 @@
 #include "types.h"
 #include <cpuinfo.h>
 
+#define MSR_GS_BASE         0xC0000101
+#define MSR_KERNEL_GS_BASE  0xC0000102
+
 cpu_info g_cpu = {0};
 
 static inline void cpuid(u32 leaf, u32 subleaf, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx) {
@@ -13,7 +16,18 @@ static inline void cpuid(u32 leaf, u32 subleaf, u32 *eax, u32 *ebx, u32 *ecx, u3
     );
 }
 
-void cpuinfo_init() {
+static inline void wrmsr(u32 msr, u64 val) {
+    u32 low = (u32)val;
+    u32 high = (u32)(val >> 32);
+    __asm__ volatile("wrmsr" :: "a"(low), "d"(high), "c"(msr));
+}
+
+void cpuinfo_init(u64 kernel_stack_top) {
+    g_cpu.kernel_rsp = kernel_stack_top;
+    g_cpu.self = (u64)&g_cpu;
+    wrmsr(MSR_KERNEL_GS_BASE, (u64)&g_cpu);
+
+
     u32 eax, ebx, ecx, edx;
 
     cpuid(0, 0, &eax, &ebx, &ecx, &edx);

kernel/src/arch/x86_64/entry.asm

@@ -27,6 +27,7 @@ stack_guard:
 global stack_bottom
 stack_bottom:
     resb 16384
+global stack_top
 stack_top:
 
 section .text.entry

kernel/src/arch/x86_64/syscall.asm

@@ -0,0 +1,70 @@
+; SPDX-License-Identifier: GPL-3.0-or-later
+; Copyright (c) 2026 0xKarinyash
+
+bits 64
+
+extern syscall_dispatch
+global syscall_entry
+
+section .text
+
+syscall_entry:
+    swapgs
+    mov [gs:0], rsp ; saving users rsp in g_cpu.user_rsp
+    mov rsp, [gs:8] ; load kernel rsp from g_cpu.kernel_rsp
+
+    push qword [gs:0]
+    push r11 ; rflags
+    push rcx ; rip
+
+    push rbp
+    push rbx
+    push rdi
+    push rsi
+    push rdx
+    push r10
+    push r8
+    push r9
+    push r12
+    push r13
+    push r14
+    push r15
+
+    ; preparing c code
+    ; c waits rdi, rsi, rdx, rcx, r8, r9
+    ; user sent rax, rdi, rsi, rdx, r10, r8 (rax=id)
+
+    mov r9,  r8             ; 6th arg
+    mov r8,  r10            ; 5th arg
+    mov rcx, rdx            ; 4th arg
+    mov rdx, rsi            ; 3rd arg
+    mov rsi, rdi            ; 2nd arg
+    mov rdi, rax            ; 1st arg (id)
+
+    call syscall_dispatch
+
+    ; restoring context except RAX (result there)
+    pop r15
+    pop r14
+    pop r13
+    pop r12
+    pop r9
+    pop r8
+    pop r10
+    pop rdx
+    pop rsi
+    pop rdi
+    pop rbx
+    pop rbp
+    pop rcx ; rip
+    pop r11 ; rflags
+    add rsp, 8 ; skip rsp
+
+    mov [gs:8], rsp
+    mov rsp, [gs:0]
+    swapgs
+
+    o64 sysret
+
+
+    

kernel/src/arch/x86_64/syscall.c

@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Copyright (c) 2026 0xKarinyash
+
+#include <cpuinfo.h>
+#include <syscall.h>
+#include <types.h>
+#include <drivers/console.h>
+#include <mm/pmm.h>
+#include <mm/vmm.h>
+
+static inline void wrmsr(u32 msr, u64 val) {
+    u32 low = (u32)val;
+    u32 high = (u32)(val >> 32);
+    __asm__ volatile("wrmsr" :: "a"(low), "d"(high), "c"(msr));
+}
+
+static inline u64 rdmsr(u32 msr) {
+    u32 low, high;
+    __asm__ volatile("rdmsr" : "=a"(low), "=d"(high) : "c"(msr));
+    return ((u64)high << 32) | low;
+}
+
+extern void syscall_entry();
+
+void syscall_init() {
+    u64 efer = rdmsr(MSR_EFER);
+    wrmsr(MSR_EFER, efer | 1); // Enabling SCE in EFER. Just enabling 0 bit
+
+    // setting up STAR
+    // 32:47 kernel selector (0x08)
+    // 48:64 user selector (0x01 cuz sysret adds +16 for CS and +8 for SS)
+    u64 star = (0x13ULL << 48) | (0x08ULL << 32); 
+    wrmsr(MSR_STAR, star);
+
+    wrmsr(MSR_LSTAR, (u64)syscall_entry); // setting handler adress
+
+    // masking flags (IA32_FMASK)
+    // 9 bit for finterrupts in syscall (IF) and few more necessary flags
+    wrmsr(MSR_FMASK, 0x200); // masking only IF
+
+    if (g_cpu.kernel_rsp == 0) {
+        void* stack_phys = pmm_alloc_page();
+        g_cpu.kernel_rsp = (u64)stack_phys + HHDM_OFFSET + 4096;
+    }
+
+    wrmsr(MSR_KERNEL_GS_BASE, (u64)&g_cpu);
+}
+
+u64 syscall_dispatch(u64 id, u64 arg1, u64 arg2, u64 arg3, u64 arg4, u64 arg5) {
+    switch (id) {
+        case SYS_EXIT: {
+            kprintf("\n[Dewar] process exited with code %d", arg1);
+            while(1) __asm__ ("hlt"); // stub
+            return 0;
+        }
+        case SYS_EXEC: {
+            kprintf("\n[Dewar] process called exec syscall");
+            return 0; // stub as well
+        }
+        case SYS_WRITE: {
+            kprintf("%s", (char*)arg1);
+            return 0;
+        }
+        default: kprintf("[Dewar] Unknown syscall %d\n", id); return -1;
+    }
+}

kernel/src/core/loader.c

@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Copyright (c) 2026 0xKarinyash
+
+#include <core/loader.h>
+#include <core/userspace.h>
+#include <core/scheduler.h>
+
+#include <shell/ksh.h>
+
+#include <mm/pmm.h>
+#include <mm/vmm.h>
+#include <mm/memory.h>
+
+#include <fs/vfs.h>
+
+#include <drivers/console.h>
+#include <types.h>
+
+extern u64* pml4_kernel;
+
+bool exec_init(const char* path) {
+    kprintf("[Loader] loading %s...\n", path);
+    fs_node* file = vfs_open(path);
+    if (!file) {
+        kprintf("[Loader] Error: %s not found in initramfs!\n", path);
+        return false;
+    }
+
+    u64 virt_code = 0x400000;
+    u64 virt_stack = 0x800000;
+    u64 stack_size = 8192;     
+
+    u64 bytes_left = file->len;
+    u64 offset = 0;
+    u64 page_idx = 0;
+
+    while (bytes_left > 0) {
+        void* phys = pmm_alloc_page();
+        if (!phys) {
+            kprintf("Loader: OOM!\n");
+            return false;
+        }
+
+        vmm_map_page(pml4_kernel, (u64)phys, virt_code + (page_idx * 4096), PTE_PRESENT | PTE_RW | PTE_USER);
+
+        void* k_ptr = (void*)(HHDM_OFFSET + (u64)phys);
+        memset(k_ptr, 0, 4096);
+        
+        u64 chunk = (bytes_left > 4096) ? 4096 : bytes_left;
+        vfs_read(file, offset, chunk, (u8*)k_ptr);
+
+        bytes_left -= chunk;
+        offset += chunk;
+        page_idx++;
+    }
+
+    for (u64 i = 0; i < (stack_size / 4096); i++) {
+        void* phys = pmm_alloc_page();
+        vmm_map_page(pml4_kernel, (u64)phys, virt_stack + (i * 4096), PTE_PRESENT | PTE_RW | PTE_USER);
+        memset((void*)(HHDM_OFFSET + (u64)phys), 0, 4096);
+    }
+
+    __asm__ volatile(
+        "mov %%cr3, %%rax\n\t"
+        "mov %%rax, %%cr3\n\t"
+        ::: "rax", "memory"
+    );
+
+    kprintf("[Loader] Transferring control to userspace...\n");
+    jump_to_userspace((void*)virt_code, (void*)(virt_stack + stack_size));
+    
+    return true; // unreachable
+}
+
+void init_task_entry() {
+    if (!exec_init("/init")) {
+        kprintf("FATAL: Could not load /init\n");
+        sched_spawn(ksh); 
+        
+        while(1) __asm__("hlt"); 
+    }
+}

kernel/src/core/scheduler.c

@@ -4,6 +4,7 @@
 #include <core/panic.h>
 #include <core/scheduler.h>
 #include <mm/heap.h>
+#include <cpuinfo.h>
 #include <gdt.h>
 
 task* curr_task = nullptr;
@@ -68,6 +69,7 @@ u64 sched_next(u64 curr_rsp) {
 
     curr_task = next;
     tss.rsp0 = curr_task->kernel_stack_top;
+    g_cpu.kernel_rsp = curr_task->kernel_stack_top;
     return curr_task->rsp;
 }
 

kernel/src/core/userspace.c

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Copyright (c) 2026 0xKarinyash
+
+#include <core/userspace.h>
+#include <types.h>
+
+#define USER_DS (0x18 | 3)
+#define USER_CS (0x20 | 3)
+#define RFLAGS_IF 0x202
+
+void jump_to_userspace(void* entry, void* user_stack_top) {
+    __asm__ volatile (
+        "mov %0, %%ds\n"
+        "mov %0, %%es\n"
+        "mov %0, %%fs\n"
+        :: "r" ((u64)USER_DS) : "memory"
+    );
+
+    __asm__ volatile (
+        "pushq %0\n" // SS (User Data Selector)
+        "pushq %1\n" // RSP (User Stack Pointer)
+        "pushq %2\n" // RFLAGS
+        "pushq %3\n" // CS (User Code Selector)
+        "pushq %4\n" // RIP (Entry Point)
+        "iretq\n"
+        : 
+        : "r" ((u64)USER_DS),
+          "r" ((u64)user_stack_top),
+          "r" ((u64)RFLAGS_IF),
+          "r" ((u64)USER_CS),
+          "r" ((u64)entry)
+        : "memory"
+    );
+}

kernel/src/drivers/shitgui.c

@@ -8,11 +8,8 @@
 #include <mm/memory.h>
 
 #define SHITGUI_TRANSPARENCY_KEY 0xFF00FF
-#define SHITGUI_MAX_WINDOWS_AMOUNT 64
 
 SG_Context* main_context;
-SG_Window* windows[SHITGUI_MAX_WINDOWS_AMOUNT]; // нет блять линукс
-u64 windows_amount = 0;
 
 void sg_init(SG_Context *ctx) {
     main_context = ctx;
@@ -85,64 +82,4 @@ void sg_draw_char_bitmap(SG_Context *ctx, SG_Point *p, char c, u32 color, SG_Fon
             }
         }
     }
-}
-
-SG_Window* create_window(const char *title, SG_Point* size, SG_Point* position) {
-    if (windows_amount >= SHITGUI_MAX_WINDOWS_AMOUNT) return nullptr; 
-    SG_Context* ctx = nullptr;
-    u32* fb = nullptr;
-    SG_Window* window = nullptr;
-
-    ctx = (SG_Context*)malloc(sizeof(SG_Context));
-    if (!ctx) goto fail; // goto is GOOD for cleaning up in C stfu. 
-                         // Mainline linux kernel contains 100k gotos
-
-    fb = malloc(size->x * size->y * sizeof(u32));
-    if (!fb) goto fail;
-    memset(fb, 0, size->x * size->y * sizeof(u32));
-
-    window = (SG_Window*)malloc(sizeof(SG_Window));
-    if (!window) goto fail;
-
-    ctx->fb = fb;
-    ctx->height = size->y;
-    ctx->width = size->x;
-    ctx->pitch = size->x;
-    
-    
-    window->ctx = ctx;
-    window->title = title;
-    window->pos.x = position->x;
-    window->pos.y = position->y;
-
-    windows[windows_amount] = window;
-    windows_amount++;    
-
-    return window;
-
-fail:
-    if (ctx) free(ctx);
-    if (fb) free(fb);
-    if (window) free(window);
-
-    return nullptr;
-}
-
-void render_window(SG_Context *ctx, SG_Window *window) {
-    SG_Image img = {0};
-    img.buffer = window->ctx->fb;
-    if (!img.buffer) panic("No img buffer found");
-    img.height = window->ctx->height;
-    img.width  = window->ctx->width;
-
-    sg_put_img(ctx, &window->pos, &img);
-}
-
-void composer_task() {
-    while (true) {
-        for (u64 i = 0; i < windows_amount; i++) {
-            render_window(main_context, windows[i]);
-        }
-        yield(1);
-    }
 }

kernel/src/kmain.c

@@ -2,7 +2,7 @@
 // Copyright (c) 2025 0xKarinyash
 
 #include "bootinfo.h"
-#include "core/rand.h"
+
 #include <shell/ksh.h>
 
 #include <types.h>
@@ -15,11 +15,14 @@
 #include <core/panic.h>
 #include <core/scheduler.h>
 #include <core/splash.h>
+#include <core/rand.h>
+#include <core/loader.h>
 
 #include <gdt.h>
 #include <idt.h>
 #include <pic.h>
 #include <cpuinfo.h>
+#include <syscall.h>
 
 #include <mm/pmm.h>
 #include <mm/vmm.h>
@@ -32,6 +35,7 @@
 #define BG_COLOR 0x111111
 
 extern u64 _kernel_end;
+extern void* stack_top;
 static SG_Context sg_ctx;
 
 void kmain(Bootinfo* info) {
@@ -42,7 +46,7 @@ void kmain(Bootinfo* info) {
 
     if (info->magic != BOOTINFO_MAGIC) panic("Corrupt bootinfo!");
 
-    cpuinfo_init();
+    cpuinfo_init((u64)&stack_top);
     kprintf("Got CPUINFO\n");
     rng_init();
     kprintf("RNG initialized\n");
@@ -64,6 +68,7 @@ void kmain(Bootinfo* info) {
     kprintf("Scheduler initialized\n");
     sg_init(&sg_ctx);
     kprintf("Shitgui initialized\n");
+    syscall_init();
 
     info = (Bootinfo*)PHYS_TO_HHDM((u64)info);
 
@@ -85,9 +90,20 @@ void kmain(Bootinfo* info) {
 
     show_splash(&sg_ctx);
 
-    sched_spawn(composer_task);
-    sched_spawn(ksh);
-    if (!info->initramfs.addr) kprintf("^rWARNING^!: Failed to load ^yinitramfs^!, VFS is empty.\n\n");
+    bool staying_in_ksh = false;
+    if (!info->initramfs.addr) { 
+        kprintf("^rWARNING^!: Failed to load ^yinitramfs^!! Staying in kernel rescue shell!\n\n"); 
+        staying_in_ksh = true; 
+    }
+
+    kprintf("Press any key to stay in ^gksh^!. \nPress ^yenter^! to continue booting in ring 3\n");
+    char c = '\n';
+    c = console_getc();
+    if (c != '\n') staying_in_ksh = true;
+    
+    if (staying_in_ksh) sched_spawn(ksh);
+    else sched_spawn(init_task_entry);
+    
     __asm__ volatile("sti");
     
     while (true) __asm__ volatile("hlt");

kernel/src/shell/builtins.c

@@ -35,7 +35,7 @@ void cmd_kfetch() {
     kprintf("^p %s ^!\t\t^gUptime^!: %d seconds\n^!", ascii_logo[4], uptime_s);   
     kprintf("^p %s ^!\t\t^gShell^!: ksh\n^!", ascii_logo[5]);   
     kprintf("^p %s ^!\t\t^gDE^!: shitgui\n^!", ascii_logo[6]);   
-    kprintf("^p %s ^!\t\t^gCPU^!: %s\n^!", ascii_logo[7], g_cpu.vendor);
+    kprintf("^p %s ^!\t\t^gCPU^!: %s (^yFamily^!: %d; ^yModel^!: %d)\n^!", ascii_logo[7], g_cpu.vendor, g_cpu.family, g_cpu.model);
     kprintf("\n\n");
 }
 

kernel/src/shell/dbgcmd.c

@@ -1,57 +1,9 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
-// Copyright (c) 2025 0xKarinyash
-// contents of this file will be changed CONSTANTLY
-// im just testing new stuff here
+// Copyright (c) 2026 0xKarinyash
 
-#include "mm/vmm.h"
-#include <mm/pmm.h>
 #include <shell/dbgcmd.h>
 #include <drivers/console.h>
 
-extern u64* pml4_kernel;
-
-#define USER_DS (0x18 | 3)
-#define USER_CS (0x20 | 3)
-#define RFLAGS_IF 0x202
-
-void jump_to_userspace(void* entry, void* user_stack_top) {
-    __asm__ volatile (
-        "mov %0, %%ds\n"
-        "mov %0, %%es\n"
-        "mov %0, %%fs\n"
-        "mov %0, %%gs\n"
-        :: "r" ((u64)USER_DS) : "memory"
-    );
-
-    __asm__ volatile (
-        "pushq %0\n" // SS (User Data Selector)
-        "pushq %1\n" // RSP (User Stack Pointer)
-        "pushq %2\n" // RFLAGS
-        "pushq %3\n" // CS (User Code Selector)
-        "pushq %4\n" // RIP (Entry Point)
-        "iretq\n"    // jump
-        : 
-        : "r" ((u64)USER_DS),
-          "r" ((u64)user_stack_top),
-          "r" ((u64)RFLAGS_IF),
-          "r" ((u64)USER_CS),
-          "r" ((u64)entry)
-        : "memory"
-    );
-}
-
 u64 debug() {
-    void* phys_code = pmm_alloc_page();
-    void* phys_stack = pmm_alloc_page();
-    u64 virt_code = 0x400000;
-    u64 virt_stack = 0x800000;
-
-    vmm_map_page(pml4_kernel, (u64)phys_code, virt_code, PTE_PRESENT | PTE_RW | PTE_USER);
-    vmm_map_page(pml4_kernel, (u64)phys_stack, virt_stack, PTE_PRESENT | PTE_RW | PTE_USER);
-    u8* kernel_view = (u8*)(HHDM_OFFSET + phys_code);
-    kernel_view[0] = 0xEB; // jmp
-    kernel_view[1] = 0xFE; // to self
-    kprintf("Jumping to userspace. Goodbye.");
-    jump_to_userspace((void*)virt_code, (void*)(virt_stack + 4096));
     return 0;
 }

userspace/CMakeLists.txt

@@ -0,0 +1,10 @@
+cmake_minimum_required(VERSION 3.20)
+project(termOSuserspace LANGUAGES C ASM_NASM)
+
+set(CMAKE_C_STANDARD 23)
+set(CMAKE_C_STANDARD_REQUIRED ON)
+set(CMAKE_C_EXTENSIONS OFF)
+
+message(STATUS "Building termOS's userspace")
+
+add_subdirectory(init)

userspace/init/CMakeLists.txt

@@ -0,0 +1,32 @@
+cmake_minimum_required(VERSION 3.20)
+project(termOSinit LANGUAGES C ASM_NASM)
+
+set(CMAKE_C_STANDARD 23)
+set(CMAKE_C_STANDARD_REQUIRED ON)
+set(CMAKE_C_EXTENSIONS OFF)
+
+message(STATUS "Building termOS's init")
+
+file(GLOB_RECURSE INIT_SOURCES CMAKE_CONFIGURE_DEPENDS
+    "src/*.asm"
+    "src/*.c"
+)
+
+add_executable(init ${INIT_SOURCES})
+set_target_properties(init PROPERTIES
+    SUFFIX ""
+    LINKER_LANGUAGE C 
+)
+
+target_link_options(init PRIVATE
+    -nostdlib
+    -static
+    -Wl,--oformat=binary
+    -Wl,-Ttext=0x400000
+    -Wl,-e,start
+)
+
+add_custom_command(TARGET init POST_BUILD
+    COMMAND ${CMAKE_COMMAND} -E copy $<TARGET_FILE:init> ${CMAKE_SOURCE_DIR}/initramfs/init
+    COMMENT "Installing init binary to initramfs"
+)

userspace/init/src/entry.asm

@@ -0,0 +1,17 @@
+[BITS 64]
+
+start:
+    mov rax, 2          ; SYS_WRITE
+    mov rdi, msg_hello  ; Адрес строки
+    syscall
+
+    mov rax, 1          ; SYS_EXEC
+    syscall
+
+    mov rax, 0          ; SYS_EXIT
+    mov rdi, 1337
+    syscall
+
+    jmp $
+
+msg_hello: db "Hello from init!", 0xA, 0