bpf: add override for bpf_probe_read_user_str

bpf/aya-bpf/src/helpers.rs

@@ -20,6 +20,26 @@ pub unsafe fn bpf_probe_read<T>(src: *const T) -> Result<T, c_long> {
     Ok(v.assume_init())
 }
 
+#[inline]
+pub unsafe fn bpf_probe_read_user_str(src: *const u8, dest: &mut [u8]) -> Result<usize, c_long> {
+    let len = gen::bpf_probe_read_user_str(
+        dest.as_mut_ptr() as *mut c_void,
+        dest.len() as u32,
+        src as *const c_void,
+    );
+    if len < 0 {
+        return Err(-1);
+    }
+
+    let mut len = len as usize;
+    if len > dest.len() {
+        // this can never happen, it's needed to tell the verifier that len is
+        // bounded
+        len = dest.len();
+    }
+    Ok(len as usize)
+}
+
 #[inline]
 pub fn bpf_get_current_comm() -> Result<[c_char; 16], c_long> {
     let mut comm: [c_char; 16usize] = [0; 16];