diff --git a/tool/abi-generator/.gitignore b/tool/abi-generator/.gitignore
new file mode 100644
index 00000000..ea8c4bf7
--- /dev/null
+++ b/tool/abi-generator/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/tool/abi-generator/Cargo.lock b/tool/abi-generator/Cargo.lock
new file mode 100644
index 00000000..b0682bde
--- /dev/null
+++ b/tool/abi-generator/Cargo.lock
@@ -0,0 +1,110 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "abi-generator"
+version = "0.1.0"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+ "thiserror",
+]
+
+[[package]]
+name = "abi-lib"
+version = "0.1.0"
+dependencies = [
+ "compiler_builtins",
+ "rustc-std-workspace-core",
+]
+
+[[package]]
+name = "compiler_builtins"
+version = "0.1.108"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d68bc55329711cd719c2687bb147bc06211b0521f97ef398280108ccb23227e9"
+dependencies = [
+ "rustc-std-workspace-core",
+]
+
+[[package]]
+name = "example-abi"
+version = "0.1.0"
+dependencies = [
+ "abi-generator",
+ "abi-lib",
+ "prettyplease",
+]
+
+[[package]]
+name = "prettyplease"
+version = "0.2.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a41cf62165e97c7f814d2221421dbb9afcbcdb0a88068e5ea206e19951c2cbb5"
+dependencies = [
+ "proc-macro2",
+ "syn",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.78"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2422ad645d89c99f8f3e6b88a9fdeca7fabeac836b1002371c4367c8f984aae"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.35"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "291ec9ab5efd934aaf503a6466c5d5251535d108ee747472c3977cc5acc868ef"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "rustc-std-workspace-core"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1956f5517128a2b6f23ab2dadf1a976f4f5b27962e7724c2bf3d45e539ec098c"
+
+[[package]]
+name = "syn"
+version = "2.0.52"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b699d15b36d1f02c3e7c69f8ffef53de37aefae075d8488d4ba1a7788d574a07"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "thiserror"
+version = "1.0.57"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e45bcbe8ed29775f228095caf2cd67af7a4ccf756ebff23a306bf3e8b47b24b"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "1.0.57"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a953cb265bef375dae3de6663da4d3804eee9682ea80d8e2542529b73c531c81"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3354b9ac3fae1ff6755cb6db53683adb661634f67557942dea4facebec0fee4b"
diff --git a/tool/abi-generator/Cargo.toml b/tool/abi-generator/Cargo.toml
new file mode 100644
index 00000000..d4e50df6
--- /dev/null
+++ b/tool/abi-generator/Cargo.toml
@@ -0,0 +1,13 @@
+[package]
+name = "abi-generator"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+proc-macro2 = "^1.0.63"
+quote = "^1.0"
+syn = { version = "2.0.32", features = ["full"] }
+thiserror = "1.0.47"
+
+[workspace]
+members = ["abi-lib", "example-abi"]
diff --git a/tool/abi-generator/abi-lib/Cargo.toml b/tool/abi-generator/abi-lib/Cargo.toml
new file mode 100644
index 00000000..4845c848
--- /dev/null
+++ b/tool/abi-generator/abi-lib/Cargo.toml
@@ -0,0 +1,15 @@
+[package]
+name = "abi-lib"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+core = { version = "1.0.0", optional = true, package = "rustc-std-workspace-core" }
+compiler_builtins = { version = "0.1", optional = true }
+
+[features]
+default = []
+rustc-dep-of-std = [
+    "core",
+    "compiler_builtins/rustc-dep-of-std",
+]
diff --git a/tool/abi-generator/abi-lib/src/lib.rs b/tool/abi-generator/abi-lib/src/lib.rs
new file mode 100644
index 00000000..e38307c7
--- /dev/null
+++ b/tool/abi-generator/abi-lib/src/lib.rs
@@ -0,0 +1,19 @@
+#![feature(never_type)]
+#![no_std]
+
+mod primitive_impls;
+mod wrapper_impls;
+
+pub trait SyscallRegister {
+    fn into_syscall_register(self) -> usize;
+    fn from_syscall_register(value: usize) -> Self;
+}
+
+pub trait SyscallFatRegister {
+    fn as_syscall_meta(&self) -> usize;
+    fn as_syscall_data(&self) -> usize;
+
+    fn from_syscall_registers(meta: usize, data: usize) -> Self;
+}
+
+pub unsafe trait ThinWrapped: SyscallRegister {}
diff --git a/tool/abi-generator/abi-lib/src/primitive_impls.rs b/tool/abi-generator/abi-lib/src/primitive_impls.rs
new file mode 100644
index 00000000..a2918a49
--- /dev/null
+++ b/tool/abi-generator/abi-lib/src/primitive_impls.rs
@@ -0,0 +1,56 @@
+use core::num::NonZeroUsize;
+
+use crate::{SyscallRegister, ThinWrapped};
+
+macro_rules! numeric_impl {
+    ($($ty:ident),+ $(,)?) => {
+        $(
+            unsafe impl ThinWrapped for $ty {}
+
+            impl SyscallRegister for $ty {
+                fn into_syscall_register(self) -> usize {
+                    self as _
+                }
+
+                fn from_syscall_register(value: usize) -> Self {
+                    value as _
+                }
+            }
+        )+
+    };
+}
+
+numeric_impl!(u8, u16, u32, u64);
+numeric_impl!(i8, i16, i32, i64);
+
+unsafe impl ThinWrapped for () {}
+
+impl SyscallRegister for NonZeroUsize {
+    fn from_syscall_register(value: usize) -> Self {
+        unsafe { Self::new_unchecked(value) }
+    }
+
+    fn into_syscall_register(self) -> usize {
+        self.into()
+    }
+}
+
+impl SyscallRegister for () {
+    fn into_syscall_register(self) -> usize {
+        0
+    }
+
+    fn from_syscall_register(_value: usize) -> Self {
+        ()
+    }
+}
+
+impl SyscallRegister for ! {
+    fn from_syscall_register(_value: usize) -> Self {
+        unreachable!()
+    }
+
+    fn into_syscall_register(self) -> usize {
+        self
+    }
+}
diff --git a/tool/abi-generator/abi-lib/src/wrapper_impls.rs b/tool/abi-generator/abi-lib/src/wrapper_impls.rs
new file mode 100644
index 00000000..860a8b52
--- /dev/null
+++ b/tool/abi-generator/abi-lib/src/wrapper_impls.rs
@@ -0,0 +1,95 @@
+use core::num::NonZeroUsize;
+
+use crate::{SyscallRegister, ThinWrapped};
+
+pub fn make_error<E: SyscallRegister>(e: E) -> usize {
+    (-(e.into_syscall_register() as isize)) as usize
+}
+
+pub fn get_error<E: SyscallRegister>(value: usize) -> E {
+    E::from_syscall_register((-(value as isize)) as usize)
+}
+
+// Result<usize> is special: usize is not thinly-wrapped, but is represented in the ABI similar
+// to Unix ssize_t-returning system calls
+impl<E: SyscallRegister> SyscallRegister for Result<usize, E> {
+    fn into_syscall_register(self) -> usize {
+        match self {
+            Ok(value) => value,
+            Err(err) => make_error(err),
+        }
+    }
+
+    fn from_syscall_register(value: usize) -> Self {
+        if (value as isize) < 0 {
+            Err(get_error(value))
+        } else {
+            Ok(value as _)
+        }
+    }
+}
+
+impl<T: ThinWrapped> SyscallRegister for Option<T> {
+    fn into_syscall_register(self) -> usize {
+        match self {
+            None => usize::MAX,
+            Some(value) => value.into_syscall_register(),
+        }
+    }
+
+    fn from_syscall_register(value: usize) -> Self {
+        match value {
+            usize::MAX => None,
+            _ => Some(T::from_syscall_register(value)),
+        }
+    }
+}
+
+impl<T: ThinWrapped, E: SyscallRegister> SyscallRegister for Result<T, E> {
+    fn into_syscall_register(self) -> usize {
+        match self {
+            Ok(value) => value.into_syscall_register(),
+            Err(err) => make_error(err),
+        }
+    }
+
+    fn from_syscall_register(value: usize) -> Self {
+        if (value as isize) < 0 {
+            Err(get_error(value))
+        } else {
+            Ok(T::from_syscall_register(value))
+        }
+    }
+}
+
+impl SyscallRegister for Option<NonZeroUsize> {
+    fn into_syscall_register(self) -> usize {
+        match self {
+            Some(value) => value.into(),
+            None => 0,
+        }
+    }
+
+    fn from_syscall_register(value: usize) -> Self {
+        NonZeroUsize::new(value)
+    }
+}
+
+impl<E: SyscallRegister> SyscallRegister for Result<NonZeroUsize, E> {
+    fn into_syscall_register(self) -> usize {
+        match self {
+            Ok(value) => value.into(),
+            Err(err) => make_error(err),
+        }
+    }
+
+    fn from_syscall_register(value: usize) -> Self {
+        if (value as isize) < 0 {
+            Err(get_error(value))
+        } else if value != 0 {
+            Ok(unsafe { NonZeroUsize::new_unchecked(value) })
+        } else {
+            unreachable!()
+        }
+    }
+}
diff --git a/tool/abi-generator/example-abi/Cargo.toml b/tool/abi-generator/example-abi/Cargo.toml
new file mode 100644
index 00000000..fd163c29
--- /dev/null
+++ b/tool/abi-generator/example-abi/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "example-abi"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+abi-lib = { path = "../abi-lib" }
+
+[build-dependencies]
+abi-generator = { path = ".." }
+prettyplease = "0.2.15"
diff --git a/tool/abi-generator/example-abi/build.rs b/tool/abi-generator/example-abi/build.rs
new file mode 100644
index 00000000..1f11464d
--- /dev/null
+++ b/tool/abi-generator/example-abi/build.rs
@@ -0,0 +1,34 @@
+use std::{env, path::Path};
+
+use abi_generator::{
+    abi::{ty::TypeWidth, AbiBuilder},
+    syntax::UnwrapFancy,
+    TargetEnv,
+};
+
+fn main() {
+    println!("cargo:rerun-if-changed={}", "syscall.abi");
+    let output_dir = env::var("OUT_DIR").unwrap();
+    let output = Path::new(&output_dir);
+
+    let abi = AbiBuilder::from_file(
+        "syscall.abi",
+        TargetEnv {
+            thin_pointer_width: TypeWidth::U64,
+            fat_pointer_width: TypeWidth::U128,
+        },
+    )
+    .unwrap_fancy("syscall.abi");
+
+    let types_file = prettyplease::unparse(
+        &abi.emit_file(true, false)
+            .unwrap_fancy("Could not emit generated types"),
+    );
+    let syscalls_file = prettyplease::unparse(
+        &abi.emit_file(false, true)
+            .unwrap_fancy("Could not emit generated syscalls"),
+    );
+
+    std::fs::write(output.join("generated_types.rs"), types_file).unwrap();
+    std::fs::write(output.join("generated_syscalls.rs"), syscalls_file).unwrap();
+}
diff --git a/tool/abi-generator/example-abi/src/main.rs b/tool/abi-generator/example-abi/src/main.rs
new file mode 100644
index 00000000..a25c508c
--- /dev/null
+++ b/tool/abi-generator/example-abi/src/main.rs
@@ -0,0 +1,152 @@
+#![feature(exposed_provenance)]
+
+use std::sync::Mutex;
+
+mod types {
+    use std::marker::PhantomData;
+
+    use abi_lib::{SyscallFatRegister, SyscallRegister};
+
+    pub enum MappingSource {}
+    pub struct MountOptions;
+    pub struct UnmountOptions;
+    pub struct DirectoryEntry;
+    pub struct FileAttr;
+    pub struct SpawnOptions<'a> {
+        _a: PhantomData<&'a ()>,
+    }
+    pub struct ThreadSpawnOptions;
+    pub enum MutexOperation {}
+    pub struct SignalEntryData;
+    pub struct DeviceRequest;
+    pub enum SentMessage {}
+    pub enum ReceivedMessageMetadata {}
+    pub struct TerminalOptions;
+    pub struct TerminalSize;
+    pub struct ExecveOptions;
+    pub struct FileMetadataUpdate;
+    pub enum ProcessInfoElement {}
+    pub enum SocketOption {}
+    pub enum SystemInfo {}
+
+    pub enum ExitCode {
+        Exited(u32),
+        Killed(u32),
+    }
+
+    pub enum SeekFrom {
+        Start(u64),
+        Current(i64),
+        End(i64),
+    }
+
+    impl SyscallRegister for ExitCode {
+        fn into_syscall_register(self) -> usize {
+            match self {
+                Self::Killed(value) => (value as usize) | (1 << u32::BITS),
+                Self::Exited(value) => value as usize,
+            }
+        }
+
+        fn from_syscall_register(value: usize) -> Self {
+            if value & (1 << u32::BITS) != 0 {
+                Self::Killed(value as _)
+            } else {
+                Self::Exited(value as _)
+            }
+        }
+    }
+
+    impl SyscallFatRegister for SeekFrom {
+        fn as_syscall_meta(&self) -> usize {
+            match self {
+                Self::Start(_) => 0,
+                Self::Current(_) => 1,
+                Self::End(_) => 2,
+            }
+        }
+
+        fn as_syscall_data(&self) -> usize {
+            match self {
+                &Self::Start(value) => value as _,
+                &Self::Current(value) | &Self::End(value) => value as _,
+            }
+        }
+
+        fn from_syscall_registers(_meta: usize, _data: usize) -> Self {
+            todo!()
+        }
+    }
+
+    include!(concat!(env!("OUT_DIR"), "/generated_types.rs"));
+}
+
+mod calls {
+    use super::types::*;
+
+    macro_rules! syscall {
+        ($f:expr $(,)?) => {
+            $crate::syscall0($f)
+        };
+        ($f:expr, $a0:expr $(,)?) => {
+            $crate::syscall1($f, $a0)
+        };
+        ($f:expr, $a0:expr, $a1:expr $(,)?) => {
+            $crate::syscall2($f, $a0, $a1)
+        };
+        ($f:expr, $a0:expr, $a1:expr, $a2:expr $(,)?) => {
+            $crate::syscall3($f, $a0, $a1, $a2)
+        };
+        ($f:expr, $a0:expr, $a1:expr, $a2:expr, $a3:expr $(,)?) => {
+            $crate::syscall4($f, $a0, $a1, $a2, $a3)
+        };
+        ($f:expr, $a0:expr, $a1:expr, $a2:expr, $a3:expr, $a4:expr $(,)?) => {
+            $crate::syscall5($f, $a0, $a1, $a2, $a3, $a4)
+        };
+    }
+
+    include!(concat!(env!("OUT_DIR"), "/generated_syscalls.rs"));
+}
+
+pub use calls::*;
+pub use types::*;
+
+static SYSCALL_TRACE: Mutex<Vec<(SyscallFunction, Vec<usize>)>> = Mutex::new(Vec::new());
+
+fn syscall0(f: SyscallFunction) -> usize {
+    SYSCALL_TRACE.lock().unwrap().push((f, vec![]));
+    0
+}
+
+fn syscall1(f: SyscallFunction, a0: usize) -> usize {
+    SYSCALL_TRACE.lock().unwrap().push((f, vec![a0]));
+    0
+}
+
+fn syscall2(f: SyscallFunction, a0: usize, a1: usize) -> usize {
+    SYSCALL_TRACE.lock().unwrap().push((f, vec![a0, a1]));
+    0
+}
+
+fn syscall3(f: SyscallFunction, a0: usize, a1: usize, a2: usize) -> usize {
+    SYSCALL_TRACE.lock().unwrap().push((f, vec![a0, a1, a2]));
+    0
+}
+
+fn syscall4(f: SyscallFunction, a0: usize, a1: usize, a2: usize, a3: usize) -> usize {
+    SYSCALL_TRACE
+        .lock()
+        .unwrap()
+        .push((f, vec![a0, a1, a2, a3]));
+    0
+}
+
+fn syscall5(f: SyscallFunction, a0: usize, a1: usize, a2: usize, a3: usize, a4: usize) -> usize {
+    SYSCALL_TRACE
+        .lock()
+        .unwrap()
+        .push((f, vec![a0, a1, a2, a3, a4]));
+    0
+}
+
+fn main() {}
diff --git a/tool/abi-generator/example-abi/syscall.abi b/tool/abi-generator/example-abi/syscall.abi
new file mode 100644
index 00000000..44fadaa5
--- /dev/null
+++ b/tool/abi-generator/example-abi/syscall.abi
@@ -0,0 +1,201 @@
+// vi:syntax=yggdrasil_abi:
+
+extern {
+    type Duration = core::time::Duration;
+    type Mutex = core::sync::atomic::AtomicU32;
+    type SocketAddr = core::net::SocketAddr;
+
+    type SystemInfo;
+    type MappingSource;
+    type SpawnOptions;
+    type ThreadSpawnOptions;
+    type MutexOperation;
+    type SignalEntryData;
+    type ProcessInfoElement;
+    type ExecveOptions;
+    type MountOptions;
+    type UnmountOptions;
+    type DirectoryEntry;
+    type FileAttr;
+    type DeviceRequest;
+    type SentMessage;
+    type ReceivedMessageMetadata;
+    type TerminalOptions;
+    type TerminalSize;
+    type FileMetadataUpdate;
+    type SocketOption;
+
+    #[thin]
+    type ExitCode;
+    #[fat]
+    type SeekFrom;
+}
+
+newtype Fd(u32);
+newtype ProcessId(u32);
+newtype ThreadId(u32);
+newtype ProcessGroupId(u32);
+
+// TODO define these as enums
+newtype MessageDestination(u32);
+
+bitfield OpenOptions(u32) {
+    /// Open the file with read capability
+    READ: 0,
+    /// Open the file with write capability
+    WRITE: 1,
+
+    /// Position at the end of the opened file
+    APPEND: 2,
+    /// Truncate the file to zero bytes when opening
+    TRUNCATE: 3,
+
+    /// Create a new file if it does not exist
+    CREATE: 4,
+}
+
+bitfield FileMode(u32) {
+    /// Other user execute access
+    OTHER_EXEC: 0,
+    /// Other user write access
+    OTHER_WRITE: 1,
+    /// Other user read access
+    OTHER_READ: 2,
+
+    /// Group execute access
+    GROUP_EXEC: 0,
+    /// Group write access
+    GROUP_WRITE: 1,
+    /// Group read access
+    GROUP_READ: 2,
+
+    /// Owner execute access
+    USER_EXEC: 0,
+    /// Owner write access
+    USER_WRITE: 1,
+    /// Owner read access
+    USER_READ: 2,
+}
+
+enum Signal(u32) {
+    MemoryAccessViolation = 1,
+    Aborted = 2,
+    Killed = 3,
+    Interrupted = 4
+}
+
+enum PollControl(u32) {
+    AddFd = 1
+}
+
+enum SocketType(u32) {
+    RawPacket = 1,
+    TcpStream = 2,
+    UdpPacket = 3
+}
+
+enum Error(u32) {
+    Dummy = 1,
+    UndefinedSyscall = 2,
+    InvalidArgument = 3,
+}
+
+syscall test_syscall(a: &(u32, u64));
+//
+// // Misc
+//
+// syscall debug_trace(msg: &str);
+// syscall get_random(buffer: &mut [u8]);
+// syscall get_system_info(info: &mut SystemInfo) -> Result<Fd>;
+//
+// // Memory management
+//
+// syscall map_memory(hint: Option<NonZeroUsize>, len: usize, source: &MappingSource) -> Result<usize>;
+// syscall unmap_memory(virt: usize, len: usize) -> Result<()>;
+//
+// // Process/thread management
+//
+// syscall spawn_process(options: &SpawnOptions<'_>) -> Result<ProcessId>;
+// syscall spawn_thread(options: &ThreadSpawnOptions) -> Result<ThreadId>;
+//
+// syscall exit_thread(code: ExitCode) -> !;
+// syscall exit_process(code: ExitCode) -> !;
+// syscall wait_process(pid: ProcessId, status: &mut ExitCode) -> Result<()>;
+// syscall send_signal(pid: ProcessId, signal: Signal) -> Result<()>;
+// syscall nanosleep(duration: &Duration);
+//
+// syscall mutex(mutex: &Mutex, op: &MutexOperation) -> Result<()>;
+//
+// syscall set_signal_entry(entry: usize, stack: usize);
+// syscall exit_signal(frame: &SignalEntryData) -> !;
+//
+// syscall get_pid() -> ProcessId;
+//
+// syscall start_session() -> Result<()>;
+// syscall set_process_group_id(pid: ProcessId, pgid: Option<ProcessGroupId>) -> Result<ProcessGroupId>;
+//
+// syscall get_process_info(what: &mut ProcessInfoElement) -> Result<()>;
+// syscall set_process_info(what: &ProcessInfoElement) -> Result<()>;
+//
+// // C compat
+//
+// syscall fork() -> Result<ProcessId>;
+// syscall execve(opts: &ExecveOptions) -> Result<()>;
+//
+// // I/O
+//
+// syscall write(fd: Fd, data: &[u8]) -> Result<usize>;
+// syscall read(fd: Fd, data: &mut [u8]) -> Result<usize>;
+// syscall open(at: Option<Fd>, path: &str, opts: OpenOptions, mode: FileMode) -> Result<Fd>;
+// syscall close(fd: Fd) -> Result<()>;
+// syscall mount(options: &MountOptions) -> Result<()>;
+// syscall unmount(options: &UnmountOptions) -> Result<()>;
+// syscall open_directory(at: Option<Fd>, path: &str) -> Result<Fd>;
+// syscall read_directory_entries(fd: Fd, buffer: &mut [MaybeUninit<DirectoryEntry>]) -> Result<usize>;
+// syscall create_directory(at: Option<Fd>, path: &str, mode: FileMode) -> Result<()>;
+// syscall remove(at: Option<Fd>, path: &str) -> Result<()>;
+// syscall remove_directory(at: Option<Fd>, path: &str) -> Result<()>;
+// syscall get_metadata(at: Option<Fd>, path: &str, metadata: &mut FileAttr, follow: bool) -> Result<()>;
+// // TODO this one is broken
+// syscall seek(fd: Fd, pos: SeekFrom) -> Result<usize>;
+//
+// syscall device_request(fd: Fd, req: &mut DeviceRequest) -> Result<()>;
+//
+// syscall create_pipe(ends: &mut [MaybeUninit<Fd>; 2]) -> Result<()>;
+//
+// syscall create_poll_channel() -> Result<Fd>;
+// syscall poll_channel_control(poll_fd: Fd, ctl: PollControl, fd: Fd) -> Result<()>;
+// syscall poll_channel_wait(poll_fd: Fd, timeout: &Option<Duration>, out: &mut Option<Fd>) -> Result<()>;
+//
+// syscall open_channel(name: &str, subscribe: bool) -> Result<Fd>;
+// syscall send_message(fd: Fd, message: &SentMessage, destination: MessageDestination) -> Result<()>;
+// syscall receive_message(
+//     fd: Fd,
+//     metadata: &mut MaybeUninit<ReceivedMessageMetadata>,
+//     buffer: &mut [u8],
+//     from: &mut MaybeUninit<u32>
+// ) -> Result<usize>;
+//
+// syscall create_shared_memory(size: usize) -> Result<Fd>;
+// syscall create_pty(options: &TerminalOptions, size: &TerminalSize, fds: &mut [MaybeUninit<Fd>; 2]) -> Result<()>;
+//
+// syscall clone_fd(source: Fd, target: Option<Fd>) -> Result<Fd>;
+//
+// syscall update_metadata(at: Option<Fd>, path: &str, update: &FileMetadataUpdate) -> Result<()>;
+//
+// syscall create_timer(repeat: bool) -> Result<Fd>;
+//
+// // Network
+//
+// syscall bind_socket(listen_address: &SocketAddr, ty: SocketType) -> Result<Fd>;
+// syscall connect_socket(
+//     socket_fd: Option<Fd>,
+//     remote_address: &SocketAddr,
+//     ty: SocketType,
+//     local_address: &mut MaybeUninit<SocketAddr>
+// ) -> Result<Fd>;
+// syscall send_to(socket_fd: Fd, data: &[u8], recepient: &Option<SocketAddr>) -> Result<usize>;
+// syscall receive_from(socket_fd: Fd, buffer: &mut [u8], sender: &mut MaybeUninit<SocketAddr>) -> Result<usize>;
+// syscall get_socket_option(socket_fd: Fd, option: &mut SocketOption) -> Result<()>;
+// syscall set_socket_option(socket_fd: Fd, option: &SocketOption) -> Result<()>;
+// syscall accept(listener: Fd, address: &mut MaybeUninit<SocketAddr>) -> Result<Fd>;
diff --git a/tool/abi-generator/src/abi/mod.rs b/tool/abi-generator/src/abi/mod.rs
new file mode 100644
index 00000000..480cb558
--- /dev/null
+++ b/tool/abi-generator/src/abi/mod.rs
@@ -0,0 +1,513 @@
+use std::{collections::HashMap, path::Path, rc::Rc};
+
+use proc_macro2::{Span, TokenStream};
+use quote::{quote, TokenStreamExt};
+use syn::{punctuated::Punctuated, spanned::Spanned, token, Token};
+
+pub mod ty;
+
+use crate::{
+    abi::ty::ComplexType,
+    syntax::{
+        parse_abi, Attributes, BitfieldRange, BitfieldType, BitfieldTypeField,
+        DocumentTypeDefinition, EnumType, EnumTypeVariant, NewType, ParseError, TypeRepr,
+    },
+    TargetEnv,
+};
+
+use self::ty::{complex::ExternKind, Type};
+
+mod syscall;
+
+pub use syscall::Syscall;
+
+pub trait GenerateTypeDefinition {
+    fn generate_type_definition(&self, abi_type: &ComplexType, env: &TargetEnv) -> TokenStream;
+}
+
+pub struct TypeEnv {
+    pub locals: HashMap<String, (Rc<ComplexType>, DocumentTypeDefinition)>,
+    pub externs: HashMap<String, (syn::Type, ExternKind)>,
+}
+
+impl TypeEnv {
+    pub fn new() -> Self {
+        Self {
+            locals: HashMap::new(),
+            externs: HashMap::new(),
+        }
+    }
+
+    pub fn lookup_local(&self, name: &str) -> Option<&(Rc<ComplexType>, DocumentTypeDefinition)> {
+        self.locals.get(name)
+    }
+
+    pub fn lookup_extern(&self, name: &str) -> Option<&(syn::Type, ExternKind)> {
+        self.externs.get(name)
+    }
+
+    pub fn insert_local(
+        &mut self,
+        name: String,
+        abi_type: Rc<ComplexType>,
+        def: DocumentTypeDefinition,
+    ) {
+        self.locals.insert(name, (abi_type, def));
+    }
+
+    pub fn insert_extern(&mut self, name: String, def: syn::Type, kind: ExternKind) {
+        self.externs.insert(name, (def, kind));
+    }
+}
+
+pub struct Abi {
+    pub types: TypeEnv,
+    // Contains syscalls and their corresponding SyscallFunction enum variants
+    pub syscalls: Vec<(syn::Ident, Syscall)>,
+}
+
+pub struct AbiBuilder {
+    abi: Abi,
+    target_env: TargetEnv,
+}
+
+pub fn syscall_enum_variant_identifier(name: &syn::Ident) -> syn::Ident {
+    let name = name.to_string();
+    let string = name.split('_').fold(String::new(), |mut acc, word| {
+        word.chars().enumerate().for_each(|(i, c)| {
+            if i == 0 {
+                acc.extend(c.to_uppercase());
+            } else {
+                acc.push(c);
+            }
+        });
+        acc
+    });
+    syn::Ident::new(string.as_str(), name.span())
+}
+
+impl AbiBuilder {
+    pub fn from_file<P: AsRef<Path>>(path: P, target_env: TargetEnv) -> Result<Self, ParseError> {
+        let abi = Abi::read_file(path)?;
+        Ok(Self { abi, target_env })
+    }
+
+    pub fn from_string<S: AsRef<str>>(data: S, target_env: TargetEnv) -> Result<Self, ParseError> {
+        let abi = Abi::read_string(data)?;
+        Ok(Self { abi, target_env })
+    }
+
+    pub fn emit_syscall_dispatcher(
+        &self,
+        dispatcher_fn: &str,
+        impl_mod: &str,
+    ) -> Result<syn::File, ParseError> {
+        let dispatcher_fn = syn::Ident::new(dispatcher_fn, Span::call_site());
+        let impl_mod = syn::Ident::new(impl_mod, Span::call_site());
+
+        let raw_fn = syn::Ident::new("__fn", Span::call_site());
+        let raw_args = syn::Ident::new("__args", Span::call_site());
+
+        let mut branches = Punctuated::<_, Token![,]>::new();
+
+        for (enum_variant, syscall) in self.abi.syscalls.iter() {
+            let named_args = (0..syscall.args.len())
+                .map(|i| syn::Ident::new(&format!("__a{}", i), Span::call_site()))
+                .collect::<Vec<_>>();
+            let call_args = named_args
+                .iter()
+                .cloned()
+                .collect::<Punctuated<_, Token![,]>>();
+            let syscall_name = &syscall.name;
+
+            let handler_fn = quote! { #impl_mod::#syscall_name };
+
+            let body = quote! {
+                Ok((#handler_fn(#call_args)).into_syscall_register())
+            };
+
+            let match_arm = syscall.emit_handler_branch(
+                &named_args,
+                &raw_args,
+                body,
+                enum_variant,
+                &self.target_env,
+            );
+
+            branches.push(match_arm);
+        }
+
+        let dispatcher_fn = quote! {
+            pub(crate) fn #dispatcher_fn(#raw_fn: SyscallFunction, #raw_args: &[usize]) -> Result<usize, Error> {
+                match #raw_fn {
+                    #branches
+                }
+            }
+        };
+
+        let file = syn::parse_file(&dispatcher_fn.to_string())?;
+        Ok(file)
+    }
+
+    pub fn emit_file(&self, emit_types: bool, emit_calls: bool) -> Result<syn::File, ParseError> {
+        let mut stream = TokenStream::new();
+
+        if emit_types {
+            stream.extend(self.emit_syscall_enum());
+            stream.extend(self.emit_type_definitions());
+        }
+
+        if emit_calls {
+            // Preamble
+            stream.extend(quote! {
+                #[allow(unused_imports)]
+                use abi_lib::{SyscallRegister, SyscallFatRegister};
+            });
+            stream.extend(self.emit_syscalls());
+        }
+
+        let file = syn::parse_file(&stream.to_string())?;
+        Ok(file)
+    }
+
+    fn emit_syscall_enum(&self) -> TokenStream {
+        let syscall_discriminants = self
+            .abi
+            .syscalls
+            .iter()
+            .enumerate()
+            .map(|(index, (variant, _))| {
+                let index = index + 1;
+                quote! { #variant = #index }
+            })
+            .collect::<Punctuated<_, token::Comma>>();
+
+        let syscall_try_from_branches = self
+            .abi
+            .syscalls
+            .iter()
+            .enumerate()
+            .map(|(index, (variant, _))| {
+                let index = index + 1;
+                quote! { #index => Ok(Self::#variant) }
+            })
+            .collect::<Punctuated<_, token::Comma>>();
+
+        quote! {
+            #[derive(Clone, Copy, PartialEq, Eq, Debug, PartialOrd, Ord)]
+            #[repr(usize)]
+            pub enum SyscallFunction {
+                #syscall_discriminants
+            }
+
+            impl From<SyscallFunction> for usize {
+                fn from(value: SyscallFunction) -> usize {
+                    value as usize
+                }
+            }
+
+            impl TryFrom<usize> for SyscallFunction {
+                type Error = Error;
+
+                fn try_from(value: usize) -> Result<Self, Error> {
+                    match value {
+                        #syscall_try_from_branches,
+                        _ => Err(Error::UndefinedSyscall)
+                    }
+                }
+            }
+        }
+    }
+
+    fn emit_type_definitions(&self) -> TokenStream {
+        let mut stream = TokenStream::new();
+
+        for (_, (ty, def)) in &self.abi.types.locals {
+            stream.extend(def.generate_type_definition(ty, &self.target_env));
+        }
+
+        stream
+    }
+
+    fn emit_syscalls(&self) -> TokenStream {
+        let mut stream = TokenStream::new();
+
+        for (variant, syscall) in &self.abi.syscalls {
+            stream.append_all(syscall.emit_stub(variant, &self.target_env));
+        }
+
+        stream
+    }
+}
+
+impl Abi {
+    pub fn read_file<P: AsRef<Path>>(path: P) -> Result<Self, ParseError> {
+        let data = std::fs::read_to_string(path)?;
+        parse_abi(&data)
+    }
+
+    pub fn read_string<S: AsRef<str>>(data: S) -> Result<Self, ParseError> {
+        parse_abi(data.as_ref())
+    }
+}
+
+impl GenerateTypeDefinition for EnumType {
+    fn generate_type_definition(&self, abi_type: &ComplexType, env: &TargetEnv) -> TokenStream {
+        let Self {
+            attributes,
+            name,
+            repr,
+            variants,
+        } = self;
+        let TypeRepr(repr) = &repr;
+
+        // TODO auto-assign numbers to enum variants
+        let try_from_branches = variants
+            .iter()
+            .map(|variant| {
+                let EnumTypeVariant {
+                    discriminant,
+                    value,
+                    ..
+                } = variant;
+                quote! { #value => Ok(Self::#discriminant) }
+            })
+            .collect::<Punctuated<_, token::Comma>>();
+
+        let direct = quote! {
+            #attributes
+            #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+            #[repr(#repr)]
+            pub enum #name {
+                #variants
+            }
+
+            impl #name {
+                pub const fn into_raw(self) -> #repr {
+                    self as #repr
+                }
+
+                pub const unsafe fn from_raw(value: #repr) -> Self {
+                    core::mem::transmute(value)
+                }
+            }
+
+            impl From<#name> for #repr {
+                #[inline]
+                fn from(value: #name) -> #repr {
+                    value as #repr
+                }
+            }
+
+            impl TryFrom<#repr> for #name {
+                type Error = Error;
+
+                fn try_from(value: #repr) -> Result<#name, Error> {
+                    match value {
+                        #try_from_branches,
+                        _ => Err(Error::InvalidArgument)
+                    }
+                }
+            }
+
+            impl abi_lib::SyscallRegister for #name {
+                fn into_syscall_register(self) -> usize {
+                    self as #repr as usize
+                }
+
+                fn from_syscall_register(value: usize) -> Self {
+                    unsafe { core::mem::transmute(value as #repr) }
+                }
+            }
+        };
+
+        let wrapped = if abi_type.width(env) < env.fat_pointer_width {
+            quote! {
+                #direct
+
+                unsafe impl abi_lib::ThinWrapped for #name {}
+            }
+        } else {
+            direct
+        };
+
+        wrapped
+    }
+}
+
+fn generate_transparent_struct(
+    attributes: &Attributes,
+    name: &syn::Ident,
+    repr: &TypeRepr,
+    is_thin: bool,
+) -> TokenStream {
+    let TypeRepr(repr) = &repr;
+
+    let direct = quote! {
+        #attributes
+        #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+        pub struct #name(pub(crate) #repr);
+
+        impl #name {
+            pub const fn into_raw(self) -> #repr {
+                self.0
+            }
+
+            pub const fn bits(self) -> #repr {
+                self.0
+            }
+
+            pub const unsafe fn from_raw(value: #repr) -> Self {
+                Self(value)
+            }
+        }
+
+        impl From<#name> for #repr {
+            #[inline]
+            fn from(value: #name) -> #repr {
+                value.0
+            }
+        }
+
+        impl abi_lib::SyscallRegister for #name {
+            fn into_syscall_register(self) -> usize {
+                self.0 as _
+            }
+
+            fn from_syscall_register(value: usize) -> Self {
+                Self(value as _)
+            }
+        }
+    };
+
+    let wrapped = if is_thin {
+        quote! {
+            #direct
+
+            unsafe impl abi_lib::ThinWrapped for #name {}
+        }
+    } else {
+        direct
+    };
+
+    wrapped
+}
+
+impl GenerateTypeDefinition for NewType {
+    fn generate_type_definition(&self, abi_type: &ComplexType, env: &TargetEnv) -> TokenStream {
+        let Self {
+            attributes,
+            name,
+            repr,
+        } = self;
+
+        generate_transparent_struct(
+            attributes,
+            name,
+            repr,
+            abi_type.width(env) < env.fat_pointer_width,
+        )
+    }
+}
+
+impl GenerateTypeDefinition for BitfieldType {
+    fn generate_type_definition(&self, abi_type: &ComplexType, env: &TargetEnv) -> TokenStream {
+        let Self {
+            attributes,
+            name,
+            repr,
+            fields,
+        } = self;
+
+        let base = generate_transparent_struct(
+            attributes,
+            name,
+            repr,
+            abi_type.width(env) < env.fat_pointer_width,
+        );
+
+        let mut field_impls = TokenStream::new();
+        for BitfieldTypeField {
+            attributes,
+            name,
+            range,
+        } in fields
+        {
+            match range {
+                BitfieldRange::Single(offset) => {
+                    field_impls.extend(quote! {
+                        #attributes
+                        pub const #name: Self = Self(1 << #offset);
+                    });
+                }
+                BitfieldRange::Range(_start, _end) => todo!(),
+            }
+        }
+
+        let base = quote! {
+            #base
+
+            impl #name {
+                #field_impls
+
+                pub const fn empty() -> Self {
+                    Self(0)
+                }
+
+                pub const fn contains(&self, value: Self) -> bool {
+                    self.0 & value.0 == value.0
+                }
+            }
+
+            impl core::ops::BitOrAssign for #name {
+                fn bitor_assign(&mut self, other: Self) {
+                    self.0 |= other.0;
+                }
+            }
+
+            impl core::ops::BitAndAssign for #name {
+                fn bitand_assign(&mut self, other: Self) {
+                    self.0 &= other.0;
+                }
+            }
+
+            impl core::ops::BitAnd for #name {
+                type Output = #name;
+
+                fn bitand(self, other: Self) -> Self {
+                    Self(self.0 & other.0)
+                }
+            }
+
+            impl core::ops::BitOr for #name {
+                type Output = #name;
+
+                fn bitor(self, other: Self) -> Self {
+                    Self(self.0 | other.0)
+                }
+            }
+
+            impl core::ops::Not for #name {
+                type Output = #name;
+
+                fn not(self) -> Self {
+                    Self(!self.0)
+                }
+            }
+        };
+
+        base
+    }
+}
+
+impl GenerateTypeDefinition for DocumentTypeDefinition {
+    fn generate_type_definition(&self, abi_type: &ComplexType, env: &TargetEnv) -> TokenStream {
+        match self {
+            Self::Enum(inner) => inner.generate_type_definition(abi_type, env),
+            Self::Bitfield(inner) => inner.generate_type_definition(abi_type, env),
+            Self::NewType(inner) => inner.generate_type_definition(abi_type, env),
+            // Extern types require no definition
+            Self::ExternType(_) => TokenStream::new(),
+        }
+    }
+}
diff --git a/tool/abi-generator/src/abi/syscall.rs b/tool/abi-generator/src/abi/syscall.rs
new file mode 100644
index 00000000..2306426c
--- /dev/null
+++ b/tool/abi-generator/src/abi/syscall.rs
@@ -0,0 +1,124 @@
+use core::fmt;
+use std::rc::Rc;
+
+use proc_macro2::TokenStream;
+use quote::quote;
+
+use crate::{
+    abi::ty::{SimpleType, Type},
+    TargetEnv,
+};
+
+use super::ty::ComplexType;
+
+pub struct Syscall {
+    pub name: syn::Ident,
+    pub args: Vec<(syn::Ident, Rc<ComplexType>)>,
+    pub return_type: Option<Rc<ComplexType>>,
+}
+
+impl fmt::Debug for Syscall {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Syscall")
+            .field("name", &self.name)
+            .field("args", &self.args)
+            .field("return_type", &self.return_type)
+            .finish_non_exhaustive()
+    }
+}
+
+impl Syscall {
+    // Syntax:
+    //
+    //  syscall_handler!("abi-document.abi", pub syscall_handler {
+    //      read(fd, buffer) => ...,
+    //      write(fd, buffer) => ...,
+    //  })
+    pub fn emit_handler_branch(
+        &self,
+        named_args: &[syn::Ident],
+        raw_args: &syn::Ident,
+        body: TokenStream,
+        enum_variant: &syn::Ident,
+        env: &TargetEnv,
+    ) -> TokenStream {
+        if self.args.len() != named_args.len() {
+            todo!(
+                "Argument length mismatch: got {} expectd {}",
+                named_args.len(),
+                self.args.len()
+            )
+        }
+
+        let mut extracted_arguments = TokenStream::new();
+        let mut index = 0;
+
+        for ((_, arg), name) in std::iter::zip(self.args.iter(), named_args) {
+            let (arg_expr, arg_width) = arg.emit_from_syscall_arguments(env, raw_args, index);
+            let arg_assignment = quote! {
+                let #name = #arg_expr;
+            };
+            index += arg_width;
+
+            extracted_arguments.extend(arg_assignment);
+        }
+
+        quote! {
+            SyscallFunction::#enum_variant => {
+                #extracted_arguments
+
+                #body
+            }
+        }
+    }
+
+    pub fn emit_stub(&self, enum_variant: &syn::Ident, env: &TargetEnv) -> TokenStream {
+        let Self {
+            name,
+            args,
+            return_type,
+        } = self;
+
+        let syscall_args = args
+            .iter()
+            .map(|(name, ty)| {
+                let arg = ty.emit_to_syscall_arguments(env, name);
+                quote!(#arg,)
+            })
+            .collect::<TokenStream>();
+        let args = args
+            .iter()
+            .map(|(name, ty)| {
+                let ty = ty.as_rust_type();
+                quote!(#name: #ty,)
+            })
+            .collect::<TokenStream>();
+        let return_type_arrow = return_type.as_ref().map(|ty| {
+            let ty = ty.as_rust_type();
+            quote!(-> #ty)
+        });
+
+        let sys_call = quote!(syscall!(SyscallFunction::#enum_variant, #syscall_args));
+
+        let wrapped = match return_type.as_deref() {
+            Some(ComplexType::Simple(SimpleType::Never)) => {
+                quote! {
+                    #sys_call;
+                    unreachable!()
+                }
+            }
+            Some(ty) => {
+                let ty = ty.as_rust_type();
+                quote!(<#ty>::from_syscall_register(#sys_call))
+            }
+            None => quote!(#sys_call;),
+        };
+
+        let v = quote! {
+            pub unsafe fn #name(#args) #return_type_arrow {
+                #wrapped
+            }
+        };
+        v
+    }
+}
diff --git a/tool/abi-generator/src/abi/ty/complex.rs b/tool/abi-generator/src/abi/ty/complex.rs
new file mode 100644
index 00000000..a019fa19
--- /dev/null
+++ b/tool/abi-generator/src/abi/ty/complex.rs
@@ -0,0 +1,181 @@
+use std::{fmt, rc::Rc};
+
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::{punctuated::Punctuated, Ident, Token};
+
+use crate::TargetEnv;
+
+use super::{AbiPrimitive, SimpleType, Type, TypeKind, TypeWidth};
+
+#[derive(Clone, Copy)]
+pub enum ExternKind {
+    None,
+    Thin,
+    Fat,
+}
+
+#[derive(Clone)]
+pub enum ComplexType {
+    Simple(SimpleType),
+    MaybeUninit(Rc<ComplexType>),
+    Result(Rc<ComplexType>),
+    Option(Rc<ComplexType>),
+    Tuple(Vec<Rc<ComplexType>>),
+    Extern {
+        kind: ExternKind,
+        alias: syn::Type,
+        arguments: syn::PathArguments,
+    },
+}
+
+impl ComplexType {
+    pub fn primitive(val: AbiPrimitive) -> Self {
+        Self::Simple(SimpleType::Primitive(val))
+    }
+
+    pub fn transparent(name: Ident, val: AbiPrimitive) -> Self {
+        Self::Simple(SimpleType::Transparent { name, inner: val })
+    }
+
+    pub fn as_primitive(&self) -> Option<AbiPrimitive> {
+        if let Self::Simple(SimpleType::Primitive(ty)) = self {
+            Some(*ty)
+        } else {
+            None
+        }
+    }
+}
+
+impl Type for ComplexType {
+    fn width(&self, env: &TargetEnv) -> TypeWidth {
+        match self {
+            Self::Simple(ty) => ty.width(env),
+            Self::Option(ty) | Self::Result(ty) => match ty.kind() {
+                TypeKind::Other => ty.width(env).double(),
+                // Some(&[1, 2, 3]) -> (ptr, len), where ptr and len are non-zero
+                // None -> (null, 0)
+                TypeKind::FatPointer => env.fat_pointer_width,
+                // Some(&x) -> ptr, where ptr is non-zero
+                // None -> null
+                TypeKind::ThinPointer => env.thin_pointer_width,
+            },
+            Self::Tuple(_) => TypeWidth::Unknown,
+            Self::Extern { .. } => TypeWidth::Unknown,
+            // MaybeUninit has the same layout as its underlying data
+            Self::MaybeUninit(ty) => ty.width(env),
+        }
+    }
+
+    fn kind(&self) -> TypeKind {
+        match self {
+            Self::Simple(ty) => ty.kind(),
+            Self::MaybeUninit(ty) => ty.kind(),
+            _ => TypeKind::Other,
+        }
+    }
+
+    fn as_rust_type(&self) -> TokenStream {
+        match self {
+            Self::Simple(ty) => ty.as_rust_type(),
+            Self::Option(ty) => {
+                let ty = ty.as_rust_type();
+                quote!(Option<#ty>)
+            }
+            Self::Tuple(elems) => {
+                let elems = elems
+                    .iter()
+                    .map(|e| e.as_rust_type())
+                    .collect::<Punctuated<_, Token![,]>>();
+                quote!((#elems))
+            }
+            Self::Result(ty) => {
+                let ty = ty.as_rust_type();
+                // TODO take from TargetEnv
+                quote!(Result<#ty, Error>)
+            }
+            Self::Extern {
+                alias, arguments, ..
+            } => {
+                quote!(#alias #arguments)
+            }
+            Self::MaybeUninit(ty) => {
+                let ty = ty.as_rust_type();
+                quote!(core::mem::MaybeUninit<#ty>)
+            }
+        }
+    }
+
+    fn emit_to_syscall_arguments(&self, env: &TargetEnv, value: &Ident) -> TokenStream {
+        // TODO: Option/Result<ExternType>
+        match self {
+            Self::Simple(ty) => ty.emit_to_syscall_arguments(env, value),
+            Self::Option(ty)
+                if ty.width(env) < env.thin_pointer_width || ty.kind() == TypeKind::ThinPointer =>
+            {
+                quote!(#value.into_syscall_register())
+            }
+            Self::Extern {
+                kind: ExternKind::Thin,
+                ..
+            } => {
+                quote!(#value.into_syscall_register())
+            }
+            Self::Extern {
+                kind: ExternKind::Fat,
+                ..
+            } => {
+                quote!(#value.as_syscall_meta(), #value.as_syscall_data())
+            }
+            _ => todo!("???"),
+        }
+    }
+
+    fn emit_from_syscall_arguments(
+        &self,
+        env: &TargetEnv,
+        args: &Ident,
+        index: usize,
+    ) -> (TokenStream, usize) {
+        match self {
+            Self::Simple(ty) => ty.emit_from_syscall_arguments(env, args, index),
+            Self::Option(ty)
+                if ty.width(env) < env.thin_pointer_width || ty.kind() == TypeKind::ThinPointer =>
+            {
+                let ty = ty.as_rust_type();
+                (
+                    quote!(<Option<#ty>>::from_syscall_register(#args[#index])),
+                    1,
+                )
+            }
+            Self::Result(_) => todo!("Result"),
+            Self::Extern {
+                kind: ExternKind::Thin,
+                alias,
+                ..
+            } => (quote!(<#alias>::from_syscall_register(#args[#index])), 1),
+            Self::MaybeUninit(_) => todo!("MaybeUninit"),
+            Self::Tuple(_) => unimplemented!(),
+            _ => todo!("{:?}", self),
+        }
+    }
+}
+
+impl fmt::Debug for ComplexType {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Simple(ty) => f.debug_tuple("Simple").field(&ty).finish(),
+            Self::Result(ty) => f.debug_tuple("Result").field(&ty).finish(),
+            Self::Option(ty) => f.debug_tuple("Option").field(&ty).finish(),
+            Self::Tuple(elems) => {
+                let mut r = f.debug_tuple("Tuple");
+                for elem in elems {
+                    r.field(elem);
+                }
+                r.finish()
+            }
+            Self::Extern { alias, .. } => f.debug_tuple("Extern").field(&quote!(#alias)).finish(),
+            Self::MaybeUninit(ty) => f.debug_tuple("MaybeUninit").field(&ty).finish(),
+        }
+    }
+}
diff --git a/tool/abi-generator/src/abi/ty/mod.rs b/tool/abi-generator/src/abi/ty/mod.rs
new file mode 100644
index 00000000..5225aa6b
--- /dev/null
+++ b/tool/abi-generator/src/abi/ty/mod.rs
@@ -0,0 +1,167 @@
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::Ident;
+
+use crate::TargetEnv;
+
+pub mod complex;
+pub mod primitive;
+pub mod simple;
+
+pub use complex::ComplexType;
+pub use primitive::AbiPrimitive;
+pub use simple::SimpleType;
+
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub enum TypeKind {
+    ThinPointer,
+    FatPointer,
+    Other,
+}
+
+pub trait Type {
+    fn width(&self, env: &TargetEnv) -> TypeWidth;
+    fn kind(&self) -> TypeKind;
+    fn as_rust_type(&self) -> TokenStream;
+
+    fn emit_to_syscall_arguments(&self, env: &TargetEnv, value: &Ident) -> TokenStream;
+    fn emit_from_syscall_arguments(
+        &self,
+        env: &TargetEnv,
+        args: &Ident,
+        index: usize,
+    ) -> (TokenStream, usize);
+
+    fn as_rust_ref_type(&self, mutable: bool) -> TokenStream {
+        let inner = self.as_rust_type();
+        match mutable {
+            true => quote!(&mut #inner),
+            false => quote!(& #inner),
+        }
+    }
+
+    fn as_rust_slice_type(&self, mutable: bool) -> TokenStream {
+        let inner = self.as_rust_type();
+        match mutable {
+            true => quote!(&mut [#inner]),
+            false => quote!(&[#inner]),
+        }
+    }
+
+    fn as_rust_array_type(&self, mutable: bool, length: usize) -> TokenStream {
+        let inner = self.as_rust_type();
+        match mutable {
+            true => quote!(&mut [#inner; #length]),
+            false => quote!(&[#inner; #length]),
+        }
+    }
+}
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy, PartialOrd, Ord)]
+pub enum TypeWidth {
+    Zero,
+    U8,
+    U16,
+    U32,
+    U64,
+    U128,
+    Unknown,
+}
+
+impl TypeWidth {
+    pub fn double(&self) -> Self {
+        match self {
+            Self::Zero => todo!(),
+            Self::U8 => Self::U16,
+            Self::U16 => Self::U32,
+            Self::U32 => Self::U64,
+            Self::U64 => Self::U128,
+            Self::U128 => todo!(),
+            Self::Unknown => Self::Unknown,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::rc::Rc;
+
+    use proc_macro2::Span;
+    use quote::quote;
+    use syn::Ident;
+
+    use crate::abi::ty::Type;
+
+    use super::{AbiPrimitive, ComplexType, SimpleType, TargetEnv, TypeWidth};
+
+    const TARGET_64: TargetEnv = TargetEnv {
+        thin_pointer_width: TypeWidth::U64,
+        fat_pointer_width: TypeWidth::U128,
+    };
+
+    #[test]
+    fn type_width() {
+        let ty = SimpleType::Reference {
+            mutable: false,
+            pointee: Rc::new(ComplexType::Simple(SimpleType::Primitive(
+                AbiPrimitive::U32,
+            ))),
+        };
+        assert_eq!(ty.width(&TARGET_64), TypeWidth::U64);
+
+        let ty = SimpleType::Primitive(AbiPrimitive::U64);
+        assert_eq!(ty.width(&TARGET_64), TypeWidth::U64);
+    }
+
+    #[test]
+    fn option_width() {
+        let ty = ComplexType::Option(Rc::new(ComplexType::primitive(AbiPrimitive::U64)));
+        assert_eq!(ty.width(&TARGET_64), TypeWidth::U128);
+
+        let ty = ComplexType::Option(Rc::new(ComplexType::Simple(SimpleType::Reference {
+            mutable: true,
+            pointee: Rc::new(ComplexType::Simple(SimpleType::Primitive(
+                AbiPrimitive::U64,
+            ))),
+        })));
+        assert_eq!(ty.width(&TARGET_64), TypeWidth::U64);
+    }
+
+    #[test]
+    fn simple_rust_types() {
+        let ty = ComplexType::Option(Rc::new(ComplexType::primitive(AbiPrimitive::U32)));
+        assert_eq!(
+            quote!(Option<u32>).to_string(),
+            ty.as_rust_type().to_string()
+        );
+
+        let ty = SimpleType::Reference {
+            mutable: true,
+            pointee: Rc::new(ComplexType::Simple(SimpleType::Primitive(
+                AbiPrimitive::U64,
+            ))),
+        };
+        assert_eq!(quote!(&mut u64).to_string(), ty.as_rust_type().to_string());
+
+        let ty = SimpleType::Slice {
+            mutable: false,
+            element: Rc::new(ComplexType::Simple(SimpleType::Primitive(AbiPrimitive::U8))),
+        };
+        assert_eq!(quote!(&[u8]).to_string(), ty.as_rust_type().to_string());
+    }
+
+    #[test]
+    fn emit_to_syscall_arguments() {
+        let ty = SimpleType::Reference {
+            mutable: false,
+            pointee: Rc::new(ComplexType::Simple(SimpleType::Primitive(
+                AbiPrimitive::U64,
+            ))),
+        };
+        let val = Ident::new("val0", Span::call_site());
+        assert_eq!(
+            ty.emit_to_syscall_arguments(&TARGET_64, &val).to_string(),
+            quote!((val0 as *const _).expose_addr()).to_string()
+        );
+    }
+}
diff --git a/tool/abi-generator/src/abi/ty/primitive.rs b/tool/abi-generator/src/abi/ty/primitive.rs
new file mode 100644
index 00000000..7a2805bc
--- /dev/null
+++ b/tool/abi-generator/src/abi/ty/primitive.rs
@@ -0,0 +1,98 @@
+use std::str::FromStr;
+
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::Ident;
+
+use crate::TargetEnv;
+
+use super::{Type, TypeKind, TypeWidth};
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+pub enum AbiPrimitive {
+    Unit,
+    Bool,
+    U8,
+    I8,
+    U16,
+    I16,
+    U32,
+    I32,
+    U64,
+    I64,
+    USize,
+}
+
+impl Type for AbiPrimitive {
+    fn width(&self, env: &TargetEnv) -> TypeWidth {
+        match self {
+            Self::Unit => TypeWidth::Zero,
+            Self::U8 | Self::I8 => TypeWidth::U8,
+            Self::U16 | Self::I16 => TypeWidth::U16,
+            Self::U32 | Self::I32 => TypeWidth::U32,
+            Self::U64 | Self::I64 => TypeWidth::U64,
+            Self::USize => env.thin_pointer_width,
+            // ???
+            Self::Bool => TypeWidth::U32,
+        }
+    }
+
+    fn kind(&self) -> TypeKind {
+        TypeKind::Other
+    }
+
+    fn as_rust_type(&self) -> TokenStream {
+        match self {
+            Self::Unit => quote!(()),
+            Self::U8 => quote!(u8),
+            Self::I8 => quote!(i8),
+            Self::U16 => quote!(u16),
+            Self::I16 => quote!(i16),
+            Self::U32 => quote!(u32),
+            Self::I32 => quote!(i32),
+            Self::U64 => quote!(u64),
+            Self::I64 => quote!(i64),
+            Self::USize => quote!(usize),
+            Self::Bool => quote!(bool),
+        }
+    }
+
+    fn emit_to_syscall_arguments(&self, _env: &TargetEnv, value: &Ident) -> TokenStream {
+        quote!(#value as usize)
+    }
+
+    fn emit_from_syscall_arguments(
+        &self,
+        _env: &TargetEnv,
+        args: &Ident,
+        index: usize,
+    ) -> (TokenStream, usize) {
+        match self {
+            Self::Bool => (quote!(#args[#index] != 0), 1),
+            _ => {
+                let ty = self.as_rust_type();
+                (quote!(#args[#index] as #ty), 1)
+            }
+        }
+    }
+}
+
+impl FromStr for AbiPrimitive {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "i8" => Ok(Self::I8),
+            "u8" => Ok(Self::U8),
+            "i16" => Ok(Self::I16),
+            "u16" => Ok(Self::U16),
+            "i32" => Ok(Self::I32),
+            "u32" => Ok(Self::U32),
+            "i64" => Ok(Self::I64),
+            "u64" => Ok(Self::U64),
+            "bool" => Ok(Self::Bool),
+            "usize" => Ok(Self::USize),
+            _ => Err(()),
+        }
+    }
+}
diff --git a/tool/abi-generator/src/abi/ty/simple.rs b/tool/abi-generator/src/abi/ty/simple.rs
new file mode 100644
index 00000000..bba2df7c
--- /dev/null
+++ b/tool/abi-generator/src/abi/ty/simple.rs
@@ -0,0 +1,158 @@
+use std::rc::Rc;
+
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::Ident;
+
+use crate::TargetEnv;
+
+use super::{AbiPrimitive, ComplexType, Type, TypeKind, TypeWidth};
+
+#[derive(Debug, Clone)]
+pub enum SimpleType {
+    Primitive(AbiPrimitive),
+    Str,
+    NonZeroUsize,
+    Never,
+    Transparent {
+        name: Ident,
+        inner: AbiPrimitive,
+    },
+    Reference {
+        mutable: bool,
+        pointee: Rc<ComplexType>,
+    },
+    Slice {
+        mutable: bool,
+        element: Rc<ComplexType>,
+    },
+    Array {
+        mutable: bool,
+        element: Rc<ComplexType>,
+        length: usize,
+    },
+}
+
+impl Type for SimpleType {
+    fn width(&self, env: &TargetEnv) -> TypeWidth {
+        match self {
+            Self::Str => env.fat_pointer_width,
+            Self::NonZeroUsize => env.thin_pointer_width,
+            Self::Reference { .. } => env.thin_pointer_width,
+            Self::Array { .. } => env.thin_pointer_width,
+            Self::Slice { .. } => env.fat_pointer_width,
+            Self::Primitive(ty) => ty.width(env),
+            Self::Transparent { inner, .. } => inner.width(env),
+            Self::Never => TypeWidth::Zero,
+        }
+    }
+
+    fn kind(&self) -> TypeKind {
+        match self {
+            Self::Str => TypeKind::FatPointer,
+            Self::NonZeroUsize => TypeKind::ThinPointer,
+            Self::Primitive(ty) => ty.kind(),
+            Self::Transparent { inner, .. } => inner.kind(),
+            Self::Reference { .. } => TypeKind::ThinPointer,
+            Self::Array { .. } => TypeKind::ThinPointer,
+            Self::Slice { .. } => TypeKind::FatPointer,
+            Self::Never => TypeKind::Other,
+        }
+    }
+
+    fn as_rust_type(&self) -> TokenStream {
+        match self {
+            Self::Str => quote!(&str),
+            Self::NonZeroUsize => quote!(core::num::NonZeroUsize),
+            Self::Reference { mutable, pointee } => pointee.as_rust_ref_type(*mutable),
+            Self::Array {
+                mutable,
+                element,
+                length,
+            } => element.as_rust_array_type(*mutable, *length),
+            Self::Slice { mutable, element } => element.as_rust_slice_type(*mutable),
+            Self::Primitive(ty) => ty.as_rust_type(),
+            Self::Transparent { name, .. } => quote!(#name),
+            Self::Never => quote!(!),
+        }
+    }
+
+    fn emit_to_syscall_arguments(&self, env: &TargetEnv, value: &Ident) -> TokenStream {
+        match self {
+            Self::NonZeroUsize => quote!(#value.into()),
+            Self::Primitive(ty) => ty.emit_to_syscall_arguments(env, value),
+            Self::Transparent { .. } => quote!(#value.into_syscall_register()),
+            Self::Str => quote!(#value.as_ptr().expose_addr(), #value.len()),
+            Self::Never => todo!("Prevent Never type from being a syscall argument"),
+            Self::Reference { mutable, pointee } => {
+                let pointee = pointee.as_rust_type();
+                match mutable {
+                    true => quote!((#value as *mut #pointee).expose_addr()),
+                    false => quote!((#value as *const #pointee).expose_addr()),
+                }
+            }
+            Self::Array { mutable, .. } => match mutable {
+                true => quote!(#value.as_mut_ptr().expose_addr()),
+                false => quote!(#value.as_ptr().expose_addr()),
+            },
+            Self::Slice { mutable, .. } => match mutable {
+                true => quote!(#value.as_mut_ptr().expose_addr(), #value.len()),
+                false => quote!(#value.as_ptr().expose_addr(), #value.len()),
+            },
+        }
+    }
+
+    fn emit_from_syscall_arguments(
+        &self,
+        env: &TargetEnv,
+        args: &Ident,
+        index: usize,
+    ) -> (TokenStream, usize) {
+        match self {
+            Self::Str => (quote!(arg::str_ref(#args[#index], #args[#index + 1])?), 2),
+            Self::Never => todo!("!"),
+            Self::Slice { mutable, element } => {
+                let element = element.as_rust_type();
+                match mutable {
+                    true => (
+                        quote!(arg::slice_mut::<#element>(#args[#index], #args[#index + 1])?),
+                        2,
+                    ),
+                    false => (
+                        quote!(arg::slice_ref::<#element>(#args[#index], #args[#index + 1])?),
+                        2,
+                    ),
+                }
+            }
+            Self::Reference { mutable, pointee } => {
+                let pointee = pointee.as_rust_type();
+                match mutable {
+                    true => (quote!(arg::ref_mut::<#pointee>(#args[#index])?), 1),
+                    false => (quote!(arg::ref_const::<#pointee>(#args[#index])?), 1),
+                }
+            }
+            Self::Array {
+                mutable,
+                element,
+                length,
+            } => {
+                let element = element.as_rust_type();
+                match mutable {
+                    true => (
+                        quote!(arg::ref_mut::<[#element; #length]>(#args[#index])?),
+                        1,
+                    ),
+                    false => (
+                        quote!(arg::ref_const::<[#element; #length]>(#args[#index])?),
+                        1,
+                    ),
+                }
+            }
+            Self::NonZeroUsize => todo!("NonZeroUsize"),
+            Self::Primitive(ty) => ty.emit_from_syscall_arguments(env, args, index),
+            Self::Transparent { name, .. } => {
+                (quote!(<#name>::from_syscall_register(#args[#index])), 1)
+            }
+        }
+    }
+}
diff --git a/tool/abi-generator/src/error.rs b/tool/abi-generator/src/error.rs
new file mode 100644
index 00000000..cf615516
--- /dev/null
+++ b/tool/abi-generator/src/error.rs
@@ -0,0 +1,22 @@
+use std::io;
+
+use proc_macro2::Span;
+use syn::Ident;
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    #[error("{0}")]
+    IoError(#[from] io::Error),
+
+    #[error("{1:?}: Incorrectly constructed type: {0}")]
+    TypeError(String, Span),
+    #[error("{0:?}: Unhandled type name")]
+    UnhandledTypeNameError(Ident),
+    #[error("{0:?}: Only primitive types are allowed inside newtype X(Y) constructs")]
+    UnhandledNonPrimitive(Span),
+
+    #[error("{0}")]
+    LexError(#[from] proc_macro2::LexError),
+    #[error("{0}")]
+    ParseError(#[from] syn::parse::Error),
+}
diff --git a/tool/abi-generator/src/lib.rs b/tool/abi-generator/src/lib.rs
new file mode 100644
index 00000000..bc49ae63
--- /dev/null
+++ b/tool/abi-generator/src/lib.rs
@@ -0,0 +1,13 @@
+#![feature(if_let_guard, extend_one, proc_macro_span)]
+
+use crate::abi::ty::TypeWidth;
+
+pub mod abi;
+pub mod error;
+pub mod syntax;
+
+#[derive(Debug, PartialEq, Eq, Clone)]
+pub struct TargetEnv {
+    pub thin_pointer_width: TypeWidth,
+    pub fat_pointer_width: TypeWidth,
+}
diff --git a/tool/abi-generator/src/syntax/bitfield_type.rs b/tool/abi-generator/src/syntax/bitfield_type.rs
new file mode 100644
index 00000000..da3288ef
--- /dev/null
+++ b/tool/abi-generator/src/syntax/bitfield_type.rs
@@ -0,0 +1,120 @@
+use proc_macro2::TokenStream;
+use quote::{quote, ToTokens};
+use syn::{braced, punctuated::Punctuated, Token};
+
+use super::{
+    common::{Attributes, TypeRepr},
+    document::DocumentItemAttributes,
+};
+
+#[derive(Clone)]
+pub enum BitfieldRange {
+    Single(syn::LitInt),
+    Range(syn::LitInt, syn::LitInt),
+}
+
+#[derive(Clone)]
+pub struct BitfieldTypeField {
+    pub attributes: Attributes,
+    pub name: syn::Ident,
+    pub range: BitfieldRange,
+}
+
+#[derive(Clone)]
+pub struct BitfieldType {
+    pub attributes: Attributes,
+    pub name: syn::Ident,
+    pub repr: TypeRepr,
+    pub fields: Punctuated<BitfieldTypeField, Token![,]>,
+}
+
+impl DocumentItemAttributes for BitfieldType {
+    fn extend_attributes<I: IntoIterator<Item = syn::Attribute>>(&mut self, attrs: I) {
+        self.attributes.extend(attrs);
+    }
+}
+
+impl syn::parse::Parse for BitfieldRange {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
+        let start = input.parse()?;
+        if input.peek(Token![..]) {
+            input.parse::<Token![..]>()?;
+            let end = input.parse()?;
+            Ok(Self::Range(start, end))
+        } else {
+            Ok(Self::Single(start))
+        }
+    }
+}
+
+impl syn::parse::Parse for BitfieldTypeField {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
+        let attributes = input.parse()?;
+        let name = input.parse()?;
+        input.parse::<Token![:]>()?;
+        let range = input.parse()?;
+        Ok(Self {
+            attributes,
+            name,
+            range,
+        })
+    }
+}
+
+impl syn::parse::Parse for BitfieldType {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
+        let fields;
+        let attributes = input.parse()?;
+        let name = input.parse()?;
+        let repr = input.parse()?;
+        braced!(fields in input);
+        let fields = fields.parse_terminated(BitfieldTypeField::parse, Token![,])?;
+
+        Ok(Self {
+            attributes,
+            name,
+            repr,
+            fields,
+        })
+    }
+}
+
+impl ToTokens for BitfieldRange {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        match self {
+            Self::Range(start, end) => tokens.extend(quote!(#start..#end)),
+            Self::Single(offset) => tokens.extend(quote!(#offset)),
+        }
+    }
+}
+
+impl ToTokens for BitfieldType {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self {
+            attributes,
+            name,
+            repr,
+            fields,
+        } = self;
+        tokens.extend(quote! {
+            #attributes
+            bitfield #name #repr {
+                #fields
+            }
+        })
+    }
+}
+
+impl ToTokens for BitfieldTypeField {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self {
+            attributes,
+            name,
+            range,
+        } = self;
+        tokens.extend(quote! {
+            #attributes
+            #name: #range
+        })
+    }
+}
diff --git a/tool/abi-generator/src/syntax/common.rs b/tool/abi-generator/src/syntax/common.rs
new file mode 100644
index 00000000..06d7ff39
--- /dev/null
+++ b/tool/abi-generator/src/syntax/common.rs
@@ -0,0 +1,66 @@
+use std::ops::{Deref, DerefMut};
+
+use proc_macro2::TokenStream;
+use quote::{quote, ToTokens};
+use syn::{parenthesized, Token};
+
+#[derive(Clone)]
+pub struct TypeRepr(pub syn::Ident);
+#[derive(Clone)]
+pub struct Attributes(pub Vec<syn::Attribute>);
+
+impl Attributes {
+    pub fn new() -> Self {
+        Self(vec![])
+    }
+}
+
+impl Deref for Attributes {
+    type Target = Vec<syn::Attribute>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl DerefMut for Attributes {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+impl syn::parse::Parse for Attributes {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
+        syn::Attribute::parse_outer(input).map(Self)
+    }
+}
+
+impl syn::parse::Parse for TypeRepr {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
+        let content;
+        parenthesized!(content in input);
+        let content = content.parse_terminated(syn::Ident::parse, Token![,])?;
+        let mut content = content.into_iter();
+        let ty = content.next().expect("TODO insert error here");
+        if content.len() != 0 {
+            todo!("TODO insert error here");
+        }
+        Ok(Self(ty))
+    }
+}
+
+impl ToTokens for TypeRepr {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self(repr) = self;
+        tokens.extend(quote!((#repr)))
+    }
+}
+
+impl ToTokens for Attributes {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self(attrs) = self;
+        for attr in attrs {
+            attr.to_tokens(tokens);
+        }
+    }
+}
diff --git a/tool/abi-generator/src/syntax/document.rs b/tool/abi-generator/src/syntax/document.rs
new file mode 100644
index 00000000..71cee8ea
--- /dev/null
+++ b/tool/abi-generator/src/syntax/document.rs
@@ -0,0 +1,135 @@
+use quote::ToTokens;
+use syn::{parse::ParseStream, Token};
+
+use super::{
+    bitfield_type::BitfieldType,
+    enum_type::EnumType,
+    extern_block::{ExternType, ExternTypeBlock},
+    newtype::NewType,
+    syscall::SyscallDefinition,
+};
+
+#[derive(Clone)]
+pub enum DocumentTypeDefinition {
+    NewType(NewType),
+    Bitfield(BitfieldType),
+    Enum(EnumType),
+    ExternType(ExternType),
+}
+
+pub struct Document {
+    pub types: Vec<DocumentTypeDefinition>,
+    pub syscalls: Vec<SyscallDefinition>,
+}
+
+pub trait DocumentItemAttributes {
+    fn extend_attributes<I: IntoIterator<Item = syn::Attribute>>(&mut self, attrs: I);
+}
+
+enum DocumentItem {
+    ExternTypeBlock(ExternTypeBlock),
+
+    // Type definitions
+    NewType(NewType),
+    Bitfield(BitfieldType),
+    Enum(EnumType),
+
+    // Syscall definitions
+    SyscallDefinition(SyscallDefinition),
+}
+
+impl syn::parse::Parse for DocumentItem {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let lookahead = input.lookahead1();
+
+        if lookahead.peek(Token![extern]) {
+            input.parse::<Token![extern]>()?;
+            return input.parse().map(Self::ExternTypeBlock);
+        }
+
+        let item_attributes = syn::Attribute::parse_outer(input)?;
+
+        let lookahead = input.lookahead1();
+
+        let mut item = if lookahead.peek(syn::Ident) {
+            // TODO parse attributes
+            let keyword: syn::Ident = input.parse()?;
+
+            match keyword.to_string().as_str() {
+                "newtype" => NewType::parse(input).map(Self::NewType),
+                "bitfield" => BitfieldType::parse(input).map(Self::Bitfield),
+                "syscall" => SyscallDefinition::parse(input).map(Self::SyscallDefinition),
+                _ => todo!(),
+            }
+        } else if lookahead.peek(Token![enum]) {
+            input.parse::<Token![enum]>()?;
+            EnumType::parse(input).map(Self::Enum)
+        } else {
+            todo!()
+        }?;
+
+        item.extend_attributes(item_attributes);
+
+        Ok(item)
+    }
+}
+
+impl DocumentItemAttributes for DocumentItem {
+    fn extend_attributes<I: IntoIterator<Item = syn::Attribute>>(&mut self, attrs: I) {
+        match self {
+            Self::NewType(inner) => inner.extend_attributes(attrs),
+            Self::Enum(inner) => inner.extend_attributes(attrs),
+            Self::Bitfield(inner) => inner.extend_attributes(attrs),
+            Self::SyscallDefinition(inner) => inner.extend_attributes(attrs),
+            Self::ExternTypeBlock(_) => unreachable!(),
+        }
+    }
+}
+
+impl syn::parse::Parse for Document {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let mut types = vec![];
+        let mut syscalls = vec![];
+
+        loop {
+            if input.is_empty() {
+                break;
+            }
+
+            let toplevel = DocumentItem::parse(input)?;
+
+            match toplevel {
+                DocumentItem::Enum(inner) => types.push(DocumentTypeDefinition::Enum(inner)),
+                DocumentItem::NewType(inner) => types.push(DocumentTypeDefinition::NewType(inner)),
+                DocumentItem::Bitfield(inner) => {
+                    types.push(DocumentTypeDefinition::Bitfield(inner))
+                }
+                DocumentItem::ExternTypeBlock(inner) => {
+                    types.extend(
+                        inner
+                            .types
+                            .into_iter()
+                            .map(DocumentTypeDefinition::ExternType),
+                    );
+                }
+                DocumentItem::SyscallDefinition(inner) => {
+                    syscalls.push(inner);
+                }
+            }
+        }
+
+        Ok(Self { types, syscalls })
+    }
+}
+
+impl ToTokens for DocumentItem {
+    fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
+        match self {
+            Self::Enum(inner) => inner.to_tokens(tokens),
+            Self::Bitfield(inner) => inner.to_tokens(tokens),
+            Self::NewType(inner) => inner.to_tokens(tokens),
+            Self::SyscallDefinition(inner) => inner.to_tokens(tokens),
+            Self::ExternTypeBlock(inner) => inner.to_tokens(tokens),
+        }
+    }
+}
diff --git a/tool/abi-generator/src/syntax/enum_type.rs b/tool/abi-generator/src/syntax/enum_type.rs
new file mode 100644
index 00000000..21657c5b
--- /dev/null
+++ b/tool/abi-generator/src/syntax/enum_type.rs
@@ -0,0 +1,99 @@
+use proc_macro2::TokenStream;
+use quote::{quote, ToTokens};
+use syn::{braced, punctuated::Punctuated, Token};
+
+use super::{
+    common::{Attributes, TypeRepr},
+    document::DocumentItemAttributes,
+};
+
+#[derive(Clone)]
+pub struct EnumTypeVariant {
+    pub attributes: Attributes,
+    pub discriminant: syn::Ident,
+    pub value: syn::LitInt,
+}
+
+#[derive(Clone)]
+pub struct EnumType {
+    pub attributes: Attributes,
+    pub name: syn::Ident,
+    pub repr: TypeRepr,
+    pub variants: Punctuated<EnumTypeVariant, Token![,]>,
+}
+
+impl syn::parse::Parse for EnumTypeVariant {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
+        let attributes = input.parse()?;
+        let discriminant = input.parse()?;
+        input.parse::<Token![=]>()?;
+        let value = input.parse()?;
+        // let value = if input.peek(Token![=]) {
+        //     input.parse::<Token![=]>()?;
+        //     let value = input.parse()?;
+        //     Some(value)
+        // } else {
+        //     None
+        // };
+        Ok(Self {
+            attributes,
+            discriminant,
+            value,
+        })
+    }
+}
+
+impl syn::parse::Parse for EnumType {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
+        let variants;
+        let attributes = input.parse()?;
+        let name = input.parse()?;
+        let repr = input.parse()?;
+        braced!(variants in input);
+        let variants = variants.parse_terminated(EnumTypeVariant::parse, Token![,])?;
+        Ok(Self {
+            attributes,
+            name,
+            repr,
+            variants,
+        })
+    }
+}
+
+impl DocumentItemAttributes for EnumType {
+    fn extend_attributes<I: IntoIterator<Item = syn::Attribute>>(&mut self, attrs: I) {
+        self.attributes.extend(attrs);
+    }
+}
+
+impl ToTokens for EnumTypeVariant {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self {
+            attributes,
+            discriminant,
+            value,
+        } = self;
+        // let value = value.as_ref().map(|val| quote!(= #val));
+        tokens.extend(quote! {
+            #attributes
+            #discriminant = #value
+        })
+    }
+}
+
+impl ToTokens for EnumType {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self {
+            attributes,
+            name,
+            repr,
+            variants,
+        } = self;
+        tokens.extend(quote! {
+            #attributes
+            enum #name #repr {
+                #variants
+            }
+        })
+    }
+}
diff --git a/tool/abi-generator/src/syntax/error.rs b/tool/abi-generator/src/syntax/error.rs
new file mode 100644
index 00000000..bb75d505
--- /dev/null
+++ b/tool/abi-generator/src/syntax/error.rs
@@ -0,0 +1,103 @@
+use std::path::Path;
+
+use proc_macro2::Span;
+use syn::spanned::Spanned;
+
+pub enum SyntaxError {
+    UnhandledType(syn::Type),
+    UndefinedIdentifier(syn::Ident),
+}
+
+pub enum ParseError {
+    HardError(syn::parse::Error),
+    IoError(std::io::Error),
+    SyntaxError(Vec<SyntaxError>),
+}
+
+pub trait UnwrapFancy<T> {
+    fn unwrap_fancy<P: AsRef<Path>>(self, context: P) -> T;
+}
+
+impl From<std::io::Error> for ParseError {
+    fn from(value: std::io::Error) -> Self {
+        Self::IoError(value)
+    }
+}
+
+impl From<syn::parse::Error> for ParseError {
+    fn from(value: syn::parse::Error) -> Self {
+        Self::HardError(value)
+    }
+}
+
+impl From<SyntaxError> for ParseError {
+    fn from(value: SyntaxError) -> Self {
+        Self::SyntaxError(vec![value])
+    }
+}
+
+impl SyntaxError {
+    pub fn span(&self) -> Span {
+        match self {
+            Self::UndefinedIdentifier(id) => id.span(),
+            Self::UnhandledType(ty) => ty.span(),
+        }
+    }
+
+    pub fn describe(&self) -> String {
+        match self {
+            Self::UnhandledType(_ty) => "Unhandled type".into(),
+            Self::UndefinedIdentifier(id) => format!("Undefined identifier '{}'", id),
+        }
+    }
+}
+
+impl<T> UnwrapFancy<T> for Result<T, ParseError> {
+    fn unwrap_fancy<P: AsRef<Path>>(self, path: P) -> T {
+        match self {
+            Self::Ok(value) => value,
+            Self::Err(err) => {
+                match err {
+                    ParseError::IoError(err) => {
+                        eprintln!("{}: {}", path.as_ref().display(), err);
+                    }
+                    ParseError::HardError(err) => {
+                        eprintln!("{}: {}", path.as_ref().display(), err);
+                    }
+                    ParseError::SyntaxError(errs) => {
+                        eprintln!("{}:", path.as_ref().display());
+                        for err in errs {
+                            eprintln!("* ...: {}", err.describe());
+                        }
+                    }
+                }
+                panic!("Compilation aborted");
+            }
+        }
+    }
+}
+
+impl ParseError {
+    pub fn syntax1(e: SyntaxError) -> Self {
+        Self::SyntaxError(vec![e])
+    }
+
+    pub fn fold<T, I: IntoIterator<Item = Result<T, Self>>, Q: Extend<T>>(
+        mut acc: Q,
+        it: I,
+    ) -> Result<Q, Self> {
+        let mut errors = vec![];
+        for item in it {
+            match item {
+                Ok(val) => acc.extend_one(val),
+                Err(ParseError::SyntaxError(err)) => errors.extend(err),
+                Err(err) => return Err(err),
+            }
+        }
+        if errors.is_empty() {
+            Ok(acc)
+        } else {
+            Err(ParseError::SyntaxError(errors))
+        }
+    }
+}
diff --git a/tool/abi-generator/src/syntax/extern_block.rs b/tool/abi-generator/src/syntax/extern_block.rs
new file mode 100644
index 00000000..6c204572
--- /dev/null
+++ b/tool/abi-generator/src/syntax/extern_block.rs
@@ -0,0 +1,70 @@
+use proc_macro2::TokenStream;
+use quote::{quote, ToTokens};
+use syn::{braced, punctuated::Punctuated, Token};
+
+use super::Attributes;
+
+#[derive(Clone)]
+pub struct ExternType {
+    pub attributes: Attributes,
+    pub name: syn::Ident,
+    pub alias: Option<syn::Type>,
+}
+
+pub struct ExternTypeBlock {
+    pub types: Punctuated<ExternType, Token![;]>,
+}
+
+impl syn::parse::Parse for ExternType {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
+        let attributes = input.parse()?;
+        input.parse::<Token![type]>()?;
+        let name = input.parse()?;
+        let alias = if input.peek(Token![=]) {
+            input.parse::<Token![=]>()?;
+            Some(input.parse()?)
+        } else {
+            None
+        };
+        Ok(Self {
+            attributes,
+            name,
+            alias,
+        })
+    }
+}
+
+impl syn::parse::Parse for ExternTypeBlock {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
+        let types;
+        braced!(types in input);
+        let types = types.parse_terminated(ExternType::parse, Token![;])?;
+        Ok(Self { types })
+    }
+}
+
+impl ToTokens for ExternType {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self {
+            attributes,
+            name,
+            alias,
+        } = self;
+        let alias = alias.as_ref().map(|ty| quote!(= #ty));
+        tokens.extend(quote! {
+            #attributes
+            type #name #alias
+        });
+    }
+}
+
+impl ToTokens for ExternTypeBlock {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self { types } = self;
+        tokens.extend(quote! {
+            extern {
+                #types
+            }
+        })
+    }
+}
diff --git a/tool/abi-generator/src/syntax/mod.rs b/tool/abi-generator/src/syntax/mod.rs
new file mode 100644
index 00000000..f9df25e4
--- /dev/null
+++ b/tool/abi-generator/src/syntax/mod.rs
@@ -0,0 +1,329 @@
+use std::{rc::Rc, str::FromStr};
+
+use syn::{punctuated::Punctuated, Expr, ExprLit, Lit, PathSegment};
+
+use crate::abi::{
+    syscall_enum_variant_identifier,
+    ty::{complex::ExternKind, AbiPrimitive, ComplexType, SimpleType},
+    Abi, Syscall, TypeEnv,
+};
+
+mod common;
+
+// Types
+mod bitfield_type;
+mod enum_type;
+mod extern_block;
+mod newtype;
+
+mod document;
+
+mod error;
+mod syscall;
+
+pub use bitfield_type::{BitfieldRange, BitfieldType, BitfieldTypeField};
+pub use common::{Attributes, TypeRepr};
+pub use document::{Document, DocumentTypeDefinition};
+pub use enum_type::{EnumType, EnumTypeVariant};
+pub use error::{ParseError, SyntaxError, UnwrapFancy};
+pub use extern_block::{ExternType, ExternTypeBlock};
+pub use newtype::NewType;
+
+pub fn parse_abi_document(input: &str) -> Result<Document, ParseError> {
+    let document: Document = syn::parse_str(input)?;
+    Ok(document)
+}
+
+fn as_single_segment_path(path: &syn::TypePath) -> Option<&PathSegment> {
+    if path.qself.is_some() || path.path.leading_colon.is_some() || path.path.segments.len() != 1 {
+        return None;
+    }
+
+    Some(&path.path.segments[0])
+}
+
+fn as_single_type_argument(args: &syn::PathArguments) -> Option<&syn::Type> {
+    let syn::PathArguments::AngleBracketed(args) = args else {
+        return None;
+    };
+    if args.args.len() != 1 {
+        return None;
+    }
+    let syn::GenericArgument::Type(ty) = &args.args[0] else {
+        return None;
+    };
+
+    Some(ty)
+}
+
+fn as_const_array_len(len: &Expr) -> Option<usize> {
+    let Expr::Lit(ExprLit {
+        attrs,
+        lit: Lit::Int(lit),
+    }) = len
+    else {
+        return None;
+    };
+
+    if !attrs.is_empty() {
+        todo!()
+    }
+
+    lit.base10_parse().ok()
+}
+
+fn process_type(t: &syn::Type, known_types: &TypeEnv) -> Result<Rc<ComplexType>, ParseError> {
+    match t {
+        syn::Type::Path(path) => {
+            let segment = as_single_segment_path(path).expect("TODO: more complex paths");
+
+            match segment.ident.to_string().as_str() {
+                seg if let Ok(ty) = AbiPrimitive::from_str(seg) => {
+                    Ok(Rc::new(ComplexType::primitive(ty)))
+                }
+                "NonZeroUsize" => Ok(Rc::new(ComplexType::Simple(SimpleType::NonZeroUsize))),
+                "Result" if let Some(ty) = as_single_type_argument(&segment.arguments) => {
+                    let ty = process_type(ty, known_types)?;
+                    Ok(Rc::new(ComplexType::Result(ty)))
+                }
+                "Option" if let Some(ty) = as_single_type_argument(&segment.arguments) => {
+                    let ty = process_type(ty, known_types)?;
+                    Ok(Rc::new(ComplexType::Option(ty)))
+                }
+                "MaybeUninit" if let Some(ty) = as_single_type_argument(&segment.arguments) => {
+                    let ty = process_type(ty, known_types)?;
+                    Ok(Rc::new(ComplexType::MaybeUninit(ty)))
+                }
+                name if let Some((ty, _)) = known_types.lookup_local(name) => Ok(ty.clone()),
+                name if let Some((ty, kind)) = known_types.lookup_extern(name) => {
+                    Ok(Rc::new(ComplexType::Extern {
+                        kind: *kind,
+                        alias: ty.clone(),
+                        arguments: segment.arguments.clone(),
+                    }))
+                }
+                _ => Err(ParseError::syntax1(SyntaxError::UndefinedIdentifier(
+                    segment.ident.clone(),
+                ))),
+            }
+        }
+        syn::Type::Never(_) => Ok(Rc::new(ComplexType::Simple(SimpleType::Never))),
+        syn::Type::Reference(r) => {
+            // TODO lifetimes
+            if r.lifetime.is_some() {
+                todo!()
+            }
+
+            let mutable = r.mutability.is_some();
+
+            match r.elem.as_ref() {
+                syn::Type::Slice(ty) => {
+                    let element = process_type(&ty.elem, known_types)?;
+                    Ok(Rc::new(ComplexType::Simple(SimpleType::Slice {
+                        mutable,
+                        element,
+                    })))
+                }
+                syn::Type::Path(path)
+                    if !mutable
+                        && as_single_segment_path(path)
+                            .map(|seg| seg.ident.to_string() == "str" && seg.arguments.is_empty())
+                            .unwrap_or(false) =>
+                {
+                    Ok(Rc::new(ComplexType::Simple(SimpleType::Str)))
+                }
+                syn::Type::Array(array) if let Some(length) = as_const_array_len(&array.len) => {
+                    let element = process_type(&array.elem, known_types)?;
+                    Ok(Rc::new(ComplexType::Simple(SimpleType::Array {
+                        mutable,
+                        element,
+                        length,
+                    })))
+                }
+                _ => {
+                    let pointee = process_type(&r.elem, known_types)?;
+                    Ok(Rc::new(ComplexType::Simple(SimpleType::Reference {
+                        mutable,
+                        pointee,
+                    })))
+                }
+            }
+        }
+        syn::Type::Tuple(t) => {
+            if t.elems.is_empty() {
+                Ok(Rc::new(ComplexType::primitive(AbiPrimitive::Unit)))
+            } else {
+                let elems = t
+                    .elems
+                    .iter()
+                    .map(|e| process_type(e, known_types))
+                    .collect::<Result<_, _>>()?;
+                Ok(Rc::new(ComplexType::Tuple(elems)))
+            }
+        }
+        _ => todo!(),
+    }
+}
+
+fn require_primitive_repr(repr: &TypeRepr) -> Result<AbiPrimitive, ParseError> {
+    let TypeRepr(repr) = repr;
+    Ok(AbiPrimitive::from_str(repr.to_string().as_str()).expect("TODO proper error message"))
+}
+
+fn make_single_ident_type(ident: syn::Ident) -> syn::Type {
+    syn::Type::Path(syn::TypePath {
+        qself: None,
+        path: syn::Path {
+            leading_colon: None,
+            segments: Punctuated::from_iter([syn::PathSegment {
+                arguments: syn::PathArguments::None,
+                ident,
+            }]),
+        },
+    })
+}
+
+pub enum ProcessedType {
+    Extern(syn::Type, ExternKind),
+    Local(Rc<ComplexType>, DocumentTypeDefinition),
+}
+
+fn process_extern_type(
+    def: &ExternType,
+    _known_types: &TypeEnv,
+) -> Result<(syn::Ident, syn::Type, ExternKind), ParseError> {
+    // TODO allow mixing arguments from
+    // extern { type X = ::A<B, C> };
+    // and use sites like
+    // syscall my_call(arg: X<D, E>);
+
+    // Process extern attributes
+    let mut kind = ExternKind::None;
+    for attr in def.attributes.iter() {
+        if attr.path().is_ident("thin") {
+            kind = ExternKind::Thin;
+        } else if attr.path().is_ident("fat") {
+            kind = ExternKind::Fat;
+        }
+    }
+
+    let alias = def
+        .alias
+        .clone()
+        .unwrap_or_else(|| make_single_ident_type(def.name.clone()));
+    Ok((def.name.clone(), alias, kind))
+}
+
+fn process_bitfield_type(
+    def: &BitfieldType,
+    _known_types: &TypeEnv,
+) -> Result<(syn::Ident, Rc<ComplexType>), ParseError> {
+    let repr = require_primitive_repr(&def.repr)?;
+    Ok((
+        def.name.clone(),
+        Rc::new(ComplexType::Simple(SimpleType::Transparent {
+            name: def.name.clone(),
+            inner: repr,
+        })),
+    ))
+}
+
+fn process_enum_type(
+    def: &EnumType,
+    _known_types: &TypeEnv,
+) -> Result<(syn::Ident, Rc<ComplexType>), ParseError> {
+    let repr = require_primitive_repr(&def.repr)?;
+    Ok((
+        def.name.clone(),
+        Rc::new(ComplexType::Simple(SimpleType::Transparent {
+            name: def.name.clone(),
+            inner: repr,
+        })),
+    ))
+}
+
+fn process_newtype(
+    def: &NewType,
+    _known_types: &TypeEnv,
+) -> Result<(syn::Ident, Rc<ComplexType>), ParseError> {
+    let repr = require_primitive_repr(&def.repr)?;
+    Ok((
+        def.name.clone(),
+        Rc::new(ComplexType::Simple(SimpleType::Transparent {
+            name: def.name.clone(),
+            inner: repr,
+        })),
+    ))
+}
+
+fn process_type_definition(
+    def: &DocumentTypeDefinition,
+    known_types: &TypeEnv,
+) -> Result<(syn::Ident, ProcessedType), ParseError> {
+    match def {
+        DocumentTypeDefinition::ExternType(inner) => process_extern_type(inner, known_types)
+            .map(|(ident, def_ty, kind)| (ident, ProcessedType::Extern(def_ty, kind))),
+        DocumentTypeDefinition::Enum(inner) => process_enum_type(inner, known_types)
+            .map(|(ident, def_ty)| (ident, ProcessedType::Local(def_ty, def.clone()))),
+        DocumentTypeDefinition::Bitfield(inner) => process_bitfield_type(inner, known_types)
+            .map(|(ident, def_ty)| (ident, ProcessedType::Local(def_ty, def.clone()))),
+        DocumentTypeDefinition::NewType(inner) => process_newtype(inner, known_types)
+            .map(|(ident, def_ty)| (ident, ProcessedType::Local(def_ty, def.clone()))),
+    }
+}
+
+pub fn parse_abi(input: &str) -> Result<Abi, ParseError> {
+    let doc = parse_abi_document(input)?;
+    let mut abi = Abi {
+        types: TypeEnv::new(),
+        syscalls: Vec::new(),
+    };
+
+    ParseError::fold(
+        (),
+        doc.types.iter().map(|nt| {
+            let (name, value) = process_type_definition(nt, &abi.types)?;
+            match value {
+                ProcessedType::Local(abi_ty, def_ty) => {
+                    abi.types.insert_local(name.to_string(), abi_ty, def_ty)
+                }
+                ProcessedType::Extern(def_ty, kind) => {
+                    abi.types.insert_extern(name.to_string(), def_ty, kind)
+                }
+            }
+            Ok(())
+        }),
+    )?;
+
+    ParseError::fold(
+        (),
+        doc.syscalls.iter().map(|syscall| {
+            let args = syscall
+                .arguments
+                .iter()
+                .map(|arg| {
+                    let ty = process_type(&arg.ty, &abi.types)?;
+                    Ok((arg.name.clone(), ty))
+                })
+                .collect::<Result<Vec<_>, ParseError>>()?;
+            let return_type = syscall
+                .return_type
+                .as_ref()
+                .map(|ty| process_type(ty, &abi.types))
+                .transpose()?;
+
+            let variant = syscall_enum_variant_identifier(&syscall.name);
+            let def = Syscall {
+                name: syscall.name.clone(),
+                args,
+                return_type,
+            };
+
+            abi.syscalls.push((variant, def));
+
+            Ok(())
+        }),
+    )?;
+
+    Ok(abi)
+}
diff --git a/tool/abi-generator/src/syntax/newtype.rs b/tool/abi-generator/src/syntax/newtype.rs
new file mode 100644
index 00000000..40242182
--- /dev/null
+++ b/tool/abi-generator/src/syntax/newtype.rs
@@ -0,0 +1,50 @@
+use proc_macro2::TokenStream;
+use quote::{quote, ToTokens};
+use syn::Token;
+
+use super::{
+    common::{Attributes, TypeRepr},
+    document::DocumentItemAttributes,
+};
+
+#[derive(Clone)]
+pub struct NewType {
+    pub attributes: Attributes,
+    pub name: syn::Ident,
+    // No need for a full type, since only certain primitives are allowed
+    pub repr: TypeRepr,
+}
+
+impl DocumentItemAttributes for NewType {
+    fn extend_attributes<I: IntoIterator<Item = syn::Attribute>>(&mut self, attrs: I) {
+        self.attributes.extend(attrs);
+    }
+}
+
+impl syn::parse::Parse for NewType {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
+        let attributes = input.parse()?;
+        let name = input.parse()?;
+        let repr = input.parse()?;
+        input.parse::<Token![;]>()?;
+        Ok(Self {
+            attributes,
+            name,
+            repr,
+        })
+    }
+}
+
+impl ToTokens for NewType {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self {
+            attributes,
+            name,
+            repr,
+        } = self;
+        tokens.extend(quote! {
+            #attributes
+            newtype #name #repr;
+        })
+    }
+}
diff --git a/tool/abi-generator/src/syntax/syscall.rs b/tool/abi-generator/src/syntax/syscall.rs
new file mode 100644
index 00000000..5c6caf56
--- /dev/null
+++ b/tool/abi-generator/src/syntax/syscall.rs
@@ -0,0 +1,82 @@
+use quote::{quote, ToTokens};
+use syn::{parenthesized, parse::ParseStream, punctuated::Punctuated, Ident, Token};
+
+use super::{common::Attributes, document::DocumentItemAttributes};
+
+pub struct SyscallDefinition {
+    pub attributes: Attributes,
+    pub name: Ident,
+    pub arguments: Punctuated<SyscallArgument, Token![,]>,
+    pub return_type: Option<syn::Type>,
+}
+
+pub struct SyscallArgument {
+    pub name: syn::Ident,
+    pub ty: syn::Type,
+}
+
+impl DocumentItemAttributes for SyscallDefinition {
+    fn extend_attributes<I: IntoIterator<Item = syn::Attribute>>(&mut self, attrs: I) {
+        self.attributes.extend(attrs);
+    }
+}
+
+impl syn::parse::Parse for SyscallDefinition {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let arguments;
+
+        let name = input.parse()?;
+        parenthesized!(arguments in input);
+        let arguments = arguments.parse_terminated(SyscallArgument::parse, Token![,])?;
+
+        let return_type = if input.peek(Token![->]) {
+            input.parse::<Token![->]>()?;
+            let ty = input.parse()?;
+            Some(ty)
+        } else {
+            None
+        };
+
+        input.parse::<Token![;]>()?;
+
+        Ok(Self {
+            attributes: Attributes::new(),
+            name,
+            arguments,
+            return_type,
+        })
+    }
+}
+
+impl syn::parse::Parse for SyscallArgument {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let name = input.parse()?;
+        input.parse::<Token![:]>()?;
+        let ty = input.parse()?;
+
+        Ok(Self { name, ty })
+    }
+}
+
+impl ToTokens for SyscallArgument {
+    fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
+        let Self { name, ty } = self;
+        tokens.extend(quote!(#name: #ty))
+    }
+}
+
+impl ToTokens for SyscallDefinition {
+    fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
+        let Self {
+            attributes,
+            name,
+            arguments,
+            return_type,
+        } = self;
+        let return_type = return_type.as_ref().map(|ty| quote!(-> #ty));
+        tokens.extend(quote! {
+            #attributes
+            syscall #name (#arguments) #return_type;
+        });
+    }
+}