feat(userspace): add ring-3 runtime startup and syscall wrappers

user/user.ld

@@ -0,0 +1,24 @@
+ENTRY(_start)
+
+PHDRS
+{
+    load PT_LOAD FILEHDR PHDRS FLAGS(7);
+}
+
+SECTIONS
+{
+    . = USER_BASE + SIZEOF_HEADERS;
+
+    .text   : { *(.text .text.*) }         :load
+    .rodata : { *(.rodata .rodata.*) }      :load
+    .data   : { *(.data .data.*) }          :load
+    .bss    : { *(.bss .bss.*) *(COMMON) }  :load
+
+    /DISCARD/ :
+    {
+        *(.comment)
+        *(.note .note.*)
+        *(.eh_frame)
+        *(.eh_frame_hdr)
+    }
+}