Use the entry point macro for lib.rs too

blog/content/second-edition/posts/09-paging-implementation/index.md

@@ -359,9 +359,32 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
 
 We no longer need to use `extern "C"` or `no_mangle` for our entry point, as the macro defines the real lower level `_start` entry point for us. The `kernel_main` function is now a completely normal Rust function, so we can choose an arbitrary name for it. The important thing is that it is type-checked so that a compilation error occurs when we use a wrong function signature, for example by adding an argument or changing the argument type.
 
+Let's perform the same change in our `lib.rs`:
+
+```rust
+// in src/lib.rs
+
+#[cfg(test)]
+use bootloader::{entry_point, BootInfo};
+
+#[cfg(test)]
+entry_point!(test_kernel_main);
+
+/// Entry point for `cargo xtest`
+#[cfg(test)]
+fn test_kernel_main(_boot_info: &'static BootInfo) -> ! {
+    // like before
+    init();
+    test_main();
+    hlt_loop();
+}
+```
+
+Since the entry point is only used in test mode, we add the `#[cfg(test)]` attribute to all items. We give our test entry point the distinct name `test_kernel_main` to avoid confusion with the `kernel_main` of our `main.rs`. We don't use the `BootInfo` parameter for now, so we prefix the parameter name with a `_` to silence the unused variable warning.
+
 ## Implementation
 
-Now that we have access to physical memory, we can finally start our implementation. First, we will take a look at the currently active page tables that our kernel runs on. In the second step, we will create a translation function that returns the physical address that a given virtual address is mapped to. As the last step, we will try to modify the page tables in order to create a new mapping.
+Now that we have access to physical memory, we can finally start to implement our page table code. First, we will take a look at the currently active page tables that our kernel runs on. In the second step, we will create a translation function that returns the physical address that a given virtual address is mapped to. As the last step, we will try to modify the page tables in order to create a new mapping.
 
 Before we begin, we create a new `memory` module for our code: