build.rs: support both existing make and proposed

runtime/build.rs

@@ -9,12 +9,14 @@ fn auto_layout() {
     use std::io::Write;
     use std::path::PathBuf;
 
+    const PLATFORM_CFG_VAR: &str = "LIBTOCK_PLATFORM";
     const LINKER_FLASH_CFG_VAR: &str = "LINKER_FLASH";
     const LINKER_RAM_CFG_VAR: &str = "LINKER_RAM";
     const LAYOUT_GENERIC_FILENAME: &str = "libtock_layout.ld";
 
     // Note: we need to print these rerun-if commands before using the variable
     // or file, so that if the build script fails cargo knows when to re-run it.
+    println!("cargo:rerun-if-env-changed={}", PLATFORM_CFG_VAR);
     println!("cargo:rerun-if-env-changed={}", LINKER_FLASH_CFG_VAR);
     println!("cargo:rerun-if-env-changed={}", LINKER_RAM_CFG_VAR);
 
@@ -30,32 +32,56 @@ fn auto_layout() {
         "Build path contains a newline, which is unsupported"
     );
 
+    // Where we are going to put the custom linker script for this particular
+    // build.
+    let out_platform_path: PathBuf = [out_dir, "layout.ld"].iter().collect();
+
+    // Choose the linker file we are going to use for this build. That can be
+    // specified by choosing a platform, where the linker file will be selected
+    // from `runtime/layouts`, or by explicitly setting the flash and RAM
+    // addresses.
+
     // Read the platform environment variable as a String (our platform names
     // should all be valid UTF-8).
-    let linker_flash = std::env::var(LINKER_FLASH_CFG_VAR).expect("Please specify LINKER_FLASH");
-    let linker_ram = std::env::var(LINKER_RAM_CFG_VAR).expect("Please specify LINKER_RAM");
+    let platform = std::env::var(PLATFORM_CFG_VAR);
 
-    // Create a valid linker file with the specified flash and ram locations.
-    //
-    // ```
-    // TBF_HEADER_SIZE = 0x60;
-    //
-    // FLASH_START = 0x00040000;
-    // FLASH_LENGTH = 0x00040000;
-    //
-    // RAM_START = 0x20008000;
-    // RAM_LENGTH = 62K;
-    //
-    // INCLUDE libtock_layout.ld
-    // ```
-    let out_platform_path: PathBuf = [out_dir, "layout.ld"].iter().collect();
-    let mut file = File::create(out_platform_path).expect("Could not create linker file");
-    write!(file, "TBF_HEADER_SIZE = 0x60;\n").expect("Could not write linker file");
-    write!(file, "FLASH_START = {};\n", linker_flash).expect("Could not write linker file");
-    write!(file, "FLASH_LENGTH = 0x000D0000;\n",).expect("Could not write linker file");
-    write!(file, "RAM_START = {};\n", linker_ram).expect("Could not write linker file");
-    write!(file, "RAM_LENGTH = 46K;\n",).expect("Could not write linker file");
-    write!(file, "INCLUDE libtock_layout.ld\n").expect("Could not write linker file");
+    // Read the explicit flash and RAM addresses.
+    let linker_flash = std::env::var(LINKER_FLASH_CFG_VAR);
+    let linker_ram = std::env::var(LINKER_RAM_CFG_VAR);
+
+    if let Ok(platform) = platform {
+        // Copy the platform-specific layout file into OUT_DIR.
+        let platform_filename = format!("{}.ld", platform);
+        let platform_path: PathBuf = ["layouts", &platform_filename].iter().collect();
+        println!("cargo:rerun-if-changed={}", platform_path.display());
+        assert!(platform_path.exists(), "Unknown platform {}", platform);
+        copy(&platform_path, out_platform_path)
+            .expect("Unable to copy platform layout into OUT_DIR");
+    } else if let (Ok(linker_flash), Ok(linker_ram)) = (linker_flash, linker_ram) {
+        // Create a valid linker file with the specified flash and ram locations.
+        //
+        // ```
+        // TBF_HEADER_SIZE = 0x60;
+        //
+        // FLASH_START = 0x00040000;
+        // FLASH_LENGTH = 0x00040000;
+        //
+        // RAM_START = 0x20008000;
+        // RAM_LENGTH = 62K;
+        //
+        // INCLUDE libtock_layout.ld
+        // ```
+        let out_platform_path: PathBuf = [out_dir, "layout.ld"].iter().collect();
+        let mut file = File::create(out_platform_path).expect("Could not create linker file");
+        write!(file, "TBF_HEADER_SIZE = 0x60;\n").expect("Could not write linker file");
+        write!(file, "FLASH_START = {};\n", linker_flash).expect("Could not write linker file");
+        write!(file, "FLASH_LENGTH = 0x000D0000;\n",).expect("Could not write linker file");
+        write!(file, "RAM_START = {};\n", linker_ram).expect("Could not write linker file");
+        write!(file, "RAM_LENGTH = 46K;\n",).expect("Could not write linker file");
+        write!(file, "INCLUDE libtock_layout.ld\n").expect("Could not write linker file");
+    } else {
+        panic!("Need to set LIBTOCK_PLATFORM or (LINKER_FLASH and LINKER_RAM)");
+    }
 
     // Copy the generic layout file into OUT_DIR.
     let out_layout_generic: PathBuf = [out_dir, LAYOUT_GENERIC_FILENAME].iter().collect();