Revert "Fix compilation on Redox by removing use of access in ld_so"

This reverts commit d9bacaec04.

src/ld_so/linker.rs

@@ -26,6 +26,7 @@ use crate::{
 };
 
 use super::{
+    access,
     debug::{RTLDDebug, RTLDState, _dl_debug_state, _r_debug},
     tcb::{Master, Tcb},
     PAGE_SIZE,
@@ -163,7 +164,20 @@ impl Linker {
                 if self.verbose {
                     println!("check {}", path);
                 }
-                return Ok(Some(self.load_recursive(name, &path)?));
+                let access = unsafe {
+                    let path_c = CString::new(path.as_bytes()).map_err(|err| {
+                        Error::Malformed(format!("invalid path '{}': {}", path, err))
+                    })?;
+
+                    // TODO: Use R_OK | X_OK
+                    // We cannot use unix stdlib because errno is thead local variable
+                    // and fs:[0] is not set yet.
+                    access(path_c.as_ptr(), unistd::F_OK) == 0
+                };
+
+                if access {
+                    return Ok(Some(self.load_recursive(name, &path)?));
+                }
             }
 
             Err(Error::Malformed(format!("failed to locate '{}'", name)))

src/ld_so/mod.rs

@@ -79,6 +79,12 @@ pub fn static_init(sp: &'static Stack) {
     }
 }
 
+// Wrapper over the systemcall, Do not use outside of ld_so
+pub unsafe fn access(path: *const c_char, mode: c_int) -> c_int {
+    let path = CStr::from_ptr(path);
+    syscall!(ACCESS, (path).as_ptr(), mode) as c_int
+}
+
 #[cfg(target_os = "linux")]
 pub unsafe fn init(sp: &'static Stack) {
     let mut tp = 0usize;