Add an example user space process

meson.build

@@ -31,6 +31,14 @@ custom_target(
   build_by_default: true,
 )
 
+custom_target(
+  'hello',
+  input: 'src/app/hello.asm',
+  output: 'hello.bin',
+  command: [nasm, '-f', 'bin', '-l', 'hello.lst', '@INPUT@', '-o', '@OUTPUT@'],
+  build_by_default: true,
+)
+
 kernel_entry_o = custom_target(
   'kernel_entry',
   input: 'src/kernel_entry.asm',
@@ -38,6 +46,12 @@ kernel_entry_o = custom_target(
   command: [nasm, '-f', 'elf64', '@INPUT@', '-o', '@OUTPUT@'],
 )
 
+syscall_o = custom_target('syscall',
+  input:  'src/syscall.asm',
+  output: 'syscall.o',
+  command: [nasm, '-f', 'elf64', '@INPUT@', '-o', '@OUTPUT@'],
+)
+
 cc = meson.get_compiler('c')
 
 kernel_sources = files(
@@ -47,6 +61,7 @@ kernel_sources = files(
   'src/ata.c',
   'src/fat16.c',
   'src/fs.c',
+  'src/gdt.c',
   'src/idt.c',
   'src/kernel.c',
   'src/keyboard.c',
@@ -54,19 +69,23 @@ kernel_sources = files(
   'src/panic.c',
   'src/path.c',
   'src/pic.c',
+  'src/process.c',
   'src/string.c',
+  'src/syscall.c',
+  'src/tss.c',
   'src/vga.c',
 )
 
 kernel_elf = executable(
   'kernel.elf',
-  sources: [kernel_entry_o, kernel_sources],
+  sources: [kernel_entry_o, syscall_o, kernel_sources],
   c_args: [
     '-ffreestanding',
     '-nostdlib',
     '-nostartfiles',
     '-mno-red-zone',
     '-mgeneral-regs-only',
+    '-mcmodel=kernel',
     '-Wno-unused-command-line-argument',
     '-Wconversion',
     '-DVERSION="' + meson.project_version() + '"',