readlink attempt

mirrord/layer/src/file/hooks.rs

@@ -948,17 +948,55 @@ unsafe extern "C" fn realpath_detour(
     source_path: *const c_char,
     output_path: *mut c_char,
 ) -> *mut c_char {
-    realpath_logic(source_path, output_path)
-        .unwrap_or_bypass_with(|_| FN_REALPATH(source_path, output_path))
+    realpath_logic(source_path, output_path).unwrap_or_bypass_with(|_bypass| {
+        #[cfg(target_os = "macos")]
+        let source_path = update_ptr_from_bypass(source_path, _bypass);
+        FN_REALPATH(source_path, output_path)
+    })
 }
 
 #[hook_guard_fn]
 unsafe extern "C" fn realpath_darwin_extsn_detour(
     source_path: *const c_char,
     output_path: *mut c_char,
 ) -> *mut c_char {
-    realpath_logic(source_path, output_path)
-        .unwrap_or_bypass_with(|_| FN_REALPATH_DARWIN_EXTSN(source_path, output_path))
+    realpath_logic(source_path, output_path).unwrap_or_bypass_with(|_bypass| {
+        #[cfg(target_os = "macos")]
+        let source_path = update_ptr_from_bypass(source_path, _bypass);
+        FN_REALPATH_DARWIN_EXTSN(source_path, output_path)
+    })
+}
+
+unsafe fn readlink_logic(
+    source_path: *const c_char,
+    output_path: *mut c_char,
+    buf_size: size_t,
+) -> Detour<ssize_t> {
+    let path = source_path.checked_into();
+
+    realpath(path).map(|res| {
+        let written_bytes = usize::min(buf_size, res.as_os_str().len());
+        output_path.copy_from_nonoverlapping(
+            res.as_os_str().as_encoded_bytes().as_ptr() as _,
+            written_bytes,
+        );
+        written_bytes as isize
+    })
+}
+
+/// When path is handled by us, just make it absolute and return, since resolving it remotely
+/// doesn't really matter for our case atm (might be in the future)
+#[hook_guard_fn]
+unsafe extern "C" fn readlink_detour(
+    source_path: *const c_char,
+    output_path: *mut c_char,
+    buf_size: size_t,
+) -> ssize_t {
+    readlink_logic(source_path, output_path, buf_size).unwrap_or_bypass_with(|_bypass| {
+        #[cfg(target_os = "macos")]
+        let source_path = update_ptr_from_bypass(source_path, _bypass);
+        FN_READLINK(source_path, output_path, buf_size)
+    })
 }
 
 fn vec_to_iovec(bytes: &[u8], iovecs: &[iovec]) {
@@ -1143,6 +1181,14 @@ pub(crate) unsafe fn enable_file_hooks(hook_manager: &mut HookManager) {
         FN_REALPATH
     );
 
+    replace!(
+        hook_manager,
+        "readlink",
+        readlink_detour,
+        FnReadlink,
+        FN_READLINK
+    );
+
     replace!(
         hook_manager,
         "realpath$DARWIN_EXTSN",