diff --git a/src/header/fcntl/mod.rs b/src/header/fcntl/mod.rs
--- a/src/header/fcntl/mod.rs
+++ b/src/header/fcntl/mod.rs
@@ -9,0 +10 @@
+    header::unistd::close,
@@ -75,0 +77,17 @@
+
+    if cmd == F_DUPFD_CLOEXEC {
+        let new_fd = Sys::fcntl(fildes, F_DUPFD_CLOEXEC, arg).or_minus_one_errno();
+        if new_fd >= 0 {
+            return new_fd;
+        }
+
+        let new_fd = Sys::fcntl(fildes, F_DUPFD, arg).or_minus_one_errno();
+        if new_fd < 0 {
+            return -1;
+        }
+        if Sys::fcntl(new_fd, F_SETFD, FD_CLOEXEC as c_ulonglong).or_minus_one_errno() < 0 {
+            let _ = close(new_fd);
+            return -1;
+        }
+        return new_fd;
+    }

diff --git a/src/pthread/mod.rs b/src/pthread/mod.rs
--- a/src/pthread/mod.rs
+++ b/src/pthread/mod.rs
@@ -2,6 +2,7 @@
 
 use core::{
     cell::UnsafeCell,
+    panic::AssertUnwindSafe,
     ptr,
     sync::atomic::{AtomicBool, AtomicUsize, Ordering},
 };
@@ -208,13 +209,41 @@ pub(crate) unsafe fn create(
 }
 
 /// A shim to wrap thread entry points in logic to set up TLS, for example
+fn catch_unwind<F: FnOnce()>(f: AssertUnwindSafe<F>) -> Result<(), ()> {
+    fn do_call<F: FnOnce()>(data: *mut u8) {
+        let callback = unsafe { &mut *data.cast::<Option<AssertUnwindSafe<F>>>() };
+        if let Some(callback) = callback.take() {
+            callback.0();
+        }
+    }
+
+    fn do_catch<F: FnOnce()>(_data: *mut u8, _payload: *mut u8) {}
+
+    let mut callback = Some(f);
+    let panicked = unsafe {
+        core::intrinsics::catch_unwind(
+            do_call::<F>,
+            (&mut callback as *mut Option<AssertUnwindSafe<F>>).cast(),
+            do_catch::<F>,
+        ) != 0
+    };
+
+    if panicked { Err(()) } else { Ok(()) }
+}
+
 unsafe extern "C" fn new_thread_shim(
     tcb: *mut Tcb,
     synchronization_mutex: *const Mutex<u64>,
 ) -> ! {
-    let tcb = unsafe { tcb.as_mut() }.expect_notls("non-null TLS is required");
+    let tcb = match unsafe { tcb.as_mut() } {
+        Some(tcb) => tcb,
+        None => {
+            log::error!("pthread: child thread started without a TCB");
+            unsafe { exit_current_thread(Retval(ptr::null_mut())) }
+        }
+    };
 
     #[cfg(not(target_os = "redox"))]
     {
@@ -227,12 +256,23 @@ unsafe extern "C" fn new_thread_shim(
         unsafe {
             tcb.activate(None);
         }
-        redox_rt::signal::setup_sighandler(&tcb.os_specific, false);
+        match catch_unwind(AssertUnwindSafe(|| {
+            redox_rt::signal::setup_sighandler(&tcb.os_specific, false)
+        })) {
+            Ok(()) => {}
+            Err(()) => {
+                log::error!("pthread: failed to set up child thread signal handler");
+                unsafe { exit_current_thread(Retval(ptr::null_mut())) }
+            }
+        }
     }
 
     let procmask = unsafe { (&*synchronization_mutex).as_ptr().read() };
 
-    unsafe { tcb.copy_masters() }.unwrap();
+    if let Err(err) = unsafe { tcb.copy_masters() } {
+        log::error!("pthread: failed to copy TLS masters for child thread: {err:?}");
+        unsafe { exit_current_thread(Retval(ptr::null_mut())) }
+    }
 
     unsafe { (*tcb).pthread.os_tid.get().write(Sys::current_os_tid()) };
 
@@ -240,11 +280,21 @@ unsafe extern "C" fn new_thread_shim(
 
     #[cfg(target_os = "redox")]
     {
-        redox_rt::signal::set_sigmask(Some(procmask), None)
-            .expect("failed to set procmask in child thread");
+        if let Err(err) = redox_rt::signal::set_sigmask(Some(procmask), None) {
+            log::error!("pthread: failed to set child thread signal mask: {err:?}");
+        }
     }
 
-    let retval = unsafe { entry_point(arg) };
+    let mut retval = ptr::null_mut();
+    match catch_unwind(AssertUnwindSafe(|| {
+        retval = unsafe { entry_point(arg) };
+    })) {
+        Ok(()) => {}
+        Err(()) => {
+            log::error!("pthread: child thread entry point panicked");
+            unsafe { exit_current_thread(Retval(ptr::null_mut())) }
+        }
+    }
 
     unsafe { exit_current_thread(Retval(retval)) }
 }