Mark _start as extern; fix wrong entry point name

blog/content/second-edition/posts/02-minimal-rust-kernel/index.md

@@ -210,7 +210,7 @@ pub extern fn rust_begin_panic(_msg: core::fmt::Arguments,
 }
 
 #[no_mangle] // don't mangle the name of this function
-pub fn _start() -> ! {
+pub extern fn _start() -> ! {
     // this function is the entry point, since the linker looks for a function
     // named `_start` by default
     loop {}
@@ -277,7 +277,7 @@ The implementation looks like this:
 static HELLO: &[u8] = b"Hello World!";
 
 #[no_mangle]
-pub fn _start() -> ! {
+pub extern fn _start() -> ! {
 	let vga_buffer = 0xb8000 as *const u8 as *mut u8;
 
     for (i, &byte) in HELLO.iter().enumerate() {

blog/content/second-edition/posts/03-vga-text-buffer/index.md

@@ -507,7 +507,7 @@ Now we can delete the `print_something` function and print directly from our `_s
 ```rust
 // in src/main.rs
 #[no_mangle]
-pub fn _start() -> ! {
+pub extern fn _start() -> ! {
     use core::fmt::Write;
     vga_buffer::WRITER.lock().write_str("Hello again").unwrap();
     write!(vga_buffer::WRITER.lock(), ", some numbers: {} {}", 42, 1.337).unwrap();
@@ -586,7 +586,7 @@ To use `println` in `main.rs`, we need to import the macros of the VGA buffer mo
 mod vga_buffer;
 
 #[no_mangle]
-pub extern fn rust_main() {
+pub extern fn _start() {
     println!("Hello World{}", "!");
 
     loop {}

src/main.rs

@@ -15,7 +15,7 @@ mod vga_buffer;
 /// This function is the entry point, since the linker looks for a function
 /// named `_start_` by default.
 #[no_mangle] // don't mangle the name of this function
-pub fn _start() -> ! {
+pub extern fn _start() -> ! {
     println!("Hello World{}", "!");
 
     loop {}