DIAG(execve): trace exec::execve (real fork+exec path, not posix_spawn) - log exe open + interp(ld.so) open, the two ENOENT-masking points

src/platform/redox/exec.rs

@@ -77,13 +77,25 @@ pub fn execve(
     arg_env: ArgEnv,
     interp_override: Option<InterpOverride>,
 ) -> Result<Infallible> {
+    let dbg = |m: &str| {
+        let _ = syscall::write(2, m.as_bytes());
+    };
+    dbg("EXECVE-DIAG: enter\n");
     // NOTE: We must omit O_CLOEXEC and close manually, otherwise it will be closed before we
     // have even read it!
     let (mut image_file, stat, arg0) = match exec {
         Executable::AtPath(path) => {
+            {
+                let mut b = alloc::string::String::from("EXECVE-DIAG: opening exe '");
+                b.push_str(core::str::from_utf8(path.to_bytes()).unwrap_or("<utf8?>"));
+                b.push_str("'\n");
+                dbg(&b);
+            }
             let Ok(src_fd) = File::open(path, O_RDONLY as c_int) else {
+                dbg("EXECVE-DIAG: exe File::open FAILED -> ENOENT\n");
                 return Err(Error::new(ENOENT));
             };
+            dbg("EXECVE-DIAG: exe opened ok\n");
 
             let mut src_stat = Stat::default();
             redox_rt::sys::fstat(*src_fd as usize, &mut src_stat)?;
@@ -166,8 +178,18 @@ pub fn execve(
     let mut args: Vec<&[u8]> = Vec::with_capacity(len);
 
     if let Some(interpreter) = &interpreter_path {
+        {
+            let mut b = alloc::string::String::from("EXECVE-DIAG: needs interp '");
+            b.push_str(core::str::from_utf8(interpreter.as_bytes()).unwrap_or("<utf8?>"));
+            b.push_str("'\n");
+            dbg(&b);
+        }
         image_file = File::open(CStr::borrow(&interpreter), O_RDONLY as c_int)
-            .map_err(|_| Error::new(ENOENT))?;
+            .map_err(|_| {
+                dbg("EXECVE-DIAG: interp File::open FAILED -> ENOENT\n");
+                Error::new(ENOENT)
+            })?;
+        dbg("EXECVE-DIAG: interp opened ok\n");
 
         // Push interpreter to arguments
         args.push(interpreter.as_bytes());