Load a very simple ELF and launch it in usermode

init/main.asm

@@ -0,0 +1,20 @@
+[bits 64]
+section     .text
+global      _start                              ;must be declared for linker (ld)
+
+_start:                                         ;tell linker entry point
+
+    xchg    bx, bx
+    mov     rdx,len                             ;message length
+    mov     rcx,msg                             ;message to write
+    mov     rbx,1                               ;file descriptor (stdout)
+    mov     rax,4                               ;system call number (sys_write)
+    int     0x80                                ;call kernel
+
+    mov     rax,1                               ;system call number (sys_exit)
+    int     0x80                                ;call kernel
+
+section     .data
+
+msg     db  'Hello, world!',0xa                 ;our dear string
+len     equ $ - msg                             ;length of our dear string