Remove the shim kernel crate

kernel/src/process/program_loader/shebang.rs

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use crate::prelude::*;
+
+/// Try to parse a buffer as a shebang line.
+///
+/// If the buffer starts with `#!` and its header is a valid shebang sequence,
+/// then the function returns `Ok(Some(parts))`,
+/// where `parts` is a `Vec` that contains the path of and the arguments for the interpreter.
+/// If the buffer starts with `#!` but some error occurs while parsing the file,
+/// then `Err(_)` is returned.
+/// If the buffer does not start with `#!`, then `Ok(None)` is returned.
+pub fn parse_shebang_line(file_header_buffer: &[u8]) -> Result<Option<Vec<CString>>> {
+    if !file_header_buffer.starts_with(b"#!") || !file_header_buffer.contains(&b'\n') {
+        // the file is not a shebang
+        return Ok(None);
+    }
+    let first_line_len = file_header_buffer.iter().position(|&c| c == b'\n').unwrap();
+    // skip #!
+    let shebang_header = &file_header_buffer[2..first_line_len];
+    let mut shebang_argv = Vec::new();
+    for arg in shebang_header.split(|&c| c == b' ') {
+        let arg = CString::new(arg)?;
+        shebang_argv.push(arg);
+    }
+    if shebang_argv.len() != 1 {
+        return_errno_with_message!(
+            Errno::EINVAL,
+            "One and only one intpreter program should be specified"
+        );
+    }
+    Ok(Some(shebang_argv))
+}