zephyr: provide a CONFIG_USERSPACE constant

Author: tylerwhall

rust-app/zephyr/Cargo.toml

@@ -14,7 +14,6 @@ compiler_builtins = { version = '0.1.2', optional = true }
 derive_more = { version = '0.14.1', default-features = false, features = ['no_std'] }
 
 [features]
-defaults = [ 'usermode', 'rustc-dep-of-std' ]
-usermode = []
+defaults = [ 'rustc-dep-of-std' ]
 rustc-dep-of-std = ['core', 'compiler_builtins', 'zephyr-sys/rustc-dep-of-std']
 have_std = []

rust-app/zephyr/build.rs

@@ -0,0 +1,5 @@
+fn main() {
+    if std::env::var("CONFIG_USERSPACE").expect("CONFIG_USERSPACE must be set") == "y" {
+        println!("cargo:rustc-cfg=usermode");
+    }
+}

rust-app/zephyr/src/lib.rs

@@ -14,6 +14,9 @@ pub mod uart;
 
 pub use time::*;
 
+// Set from environment from build.rs
+pub const CONFIG_USERSPACE: bool = cfg!(usermode);
+
 /// Convert a negative error code to a Result
 trait NegErr {
     fn neg_err(&self) -> Result<u32, u32>;