diff --git a/src/c_str.rs b/src/c_str.rs
index 56f1b084f7..91c891eb53 100644
--- a/src/c_str.rs
+++ b/src/c_str.rs
@@ -1,3 +1,5 @@
+//! Nul-terminated byte strings.
+
 use core::{marker::PhantomData, ptr::NonNull, str::Utf8Error};
 
 use alloc::{
diff --git a/src/c_vec.rs b/src/c_vec.rs
index a6edbf27ee..bb2800df2e 100644
--- a/src/c_vec.rs
+++ b/src/c_vec.rs
@@ -1,3 +1,5 @@
+//! Equivalent of Rust's `Vec<T>`, but using relibc's own allocator.
+
 use crate::{
     io::{self, Write},
     platform::{self, types::*, WriteByte},
diff --git a/src/header/mod.rs b/src/header/mod.rs
index 338c6683ac..3bb28d8e36 100644
--- a/src/header/mod.rs
+++ b/src/header/mod.rs
@@ -1,3 +1,5 @@
+//! POSIX header implementations.
+
 pub mod _aio;
 pub mod _fenv;
 pub mod arpa_inet;
diff --git a/src/ld_so/mod.rs b/src/ld_so/mod.rs
index b32c393e68..2806f09f3f 100644
--- a/src/ld_so/mod.rs
+++ b/src/ld_so/mod.rs
@@ -1,3 +1,5 @@
+//! Dynamic loading and linking.
+
 use core::{mem, ptr};
 use goblin::elf::program_header::{self, program_header32, program_header64, ProgramHeader};
 
diff --git a/src/lib.rs b/src/lib.rs
index 4ae044e0dc..d2697004d4 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,11 @@
+//! POSIX C library, implemented in Rust.
+//!
+//! This crate exists to provide a standard libc as its public API. This is
+//! largely provided by automatically generated bindings to the functions and
+//! data structures in the [`header`] module.
+//!
+//! Currently, Linux and Redox syscall backends are supported.
+
 #![no_std]
 #![allow(warnings)]
 #![allow(non_camel_case_types)]
diff --git a/src/platform/linux/mod.rs b/src/platform/linux/mod.rs
index 4667f761de..541c9430ad 100644
--- a/src/platform/linux/mod.rs
+++ b/src/platform/linux/mod.rs
@@ -65,6 +65,7 @@ pub fn e_raw(sys: usize) -> Result<usize> {
     }
 }
 
+/// Linux syscall implementation of the platform abstraction layer.
 pub struct Sys;
 
 impl Sys {
diff --git a/src/platform/mod.rs b/src/platform/mod.rs
index e8bab124be..7d3ebc50c2 100644
--- a/src/platform/mod.rs
+++ b/src/platform/mod.rs
@@ -1,3 +1,5 @@
+//! Platform abstractions and environment.
+
 use crate::{
     error::ResultExt,
     io::{self, Read, Write},
@@ -38,9 +40,11 @@ pub use redox_rt::auxv_defs;
 use self::types::*;
 pub mod types;
 
+/// The global `errno` variable used internally in relibc.
 #[thread_local]
 pub static ERRNO: Cell<c_int> = Cell::new(0);
 
+/// The `argv` argument available to a program's `main` function.
 #[allow(non_upper_case_globals)]
 pub static mut argv: *mut *mut c_char = ptr::null_mut();
 #[allow(non_upper_case_globals)]
diff --git a/src/platform/pal/mod.rs b/src/platform/pal/mod.rs
index c80069001e..6c55a98955 100644
--- a/src/platform/pal/mod.rs
+++ b/src/platform/pal/mod.rs
@@ -25,6 +25,7 @@ mod signal;
 pub use self::socket::PalSocket;
 mod socket;
 
+/// Platform abstraction layer, a platform-agnostic abstraction over syscalls.
 pub trait Pal {
     fn access(path: CStr, mode: c_int) -> Result<()>;
 
diff --git a/src/platform/redox/mod.rs b/src/platform/redox/mod.rs
index e186b5de90..8cbd5b7b8e 100644
--- a/src/platform/redox/mod.rs
+++ b/src/platform/redox/mod.rs
@@ -74,6 +74,7 @@ macro_rules! path_from_c_str {
 
 use self::{exec::Executable, path::canonicalize};
 
+/// Redox syscall implementation of the platform abstraction layer.
 pub struct Sys;
 
 impl Pal for Sys {
diff --git a/src/platform/types.rs b/src/platform/types.rs
index 202bea286b..10ac216107 100644
--- a/src/platform/types.rs
+++ b/src/platform/types.rs
@@ -1,3 +1,5 @@
+//! C data types for this platform.
+
 use core::i32;
 
 // Use repr(u8) as LLVM expects `void*` to be the same as `i8*` to help enable
diff --git a/src/start.rs b/src/start.rs
index 5f2326ec3a..754a7bbe07 100644
--- a/src/start.rs
+++ b/src/start.rs
@@ -1,3 +1,5 @@
+//! Startup code.
+
 use alloc::{boxed::Box, vec::Vec};
 use core::{intrinsics, ptr};
 
diff --git a/src/sync/mod.rs b/src/sync/mod.rs
index 254bd68108..6b22256386 100644
--- a/src/sync/mod.rs
+++ b/src/sync/mod.rs
@@ -1,3 +1,5 @@
+//! Synchronization primitives.
+
 // TODO: set this for entire crate when possible
 #![deny(unsafe_op_in_unsafe_fn)]