diff --git a/api/ruxos_posix_api/src/imp/mod.rs b/api/ruxos_posix_api/src/imp/mod.rs
index 7b7880d35..278d14056 100644
--- a/api/ruxos_posix_api/src/imp/mod.rs
+++ b/api/ruxos_posix_api/src/imp/mod.rs
@@ -14,7 +14,6 @@ pub mod getrandom;
 pub mod io;
 pub mod prctl;
 pub mod resources;
-pub mod rt_sig;
 pub mod stat;
 pub mod sys;
 pub mod task;
@@ -39,6 +38,8 @@ pub mod pipe;
 #[cfg(feature = "multitask")]
 pub mod pthread;
 #[cfg(feature = "signal")]
+pub mod rt_sig;
+#[cfg(feature = "signal")]
 pub mod signal;
 
 /// Invalid syscall
diff --git a/api/ruxos_posix_api/src/imp/rt_sig.rs b/api/ruxos_posix_api/src/imp/rt_sig.rs
index aa7a4ba7f..e7bce368d 100644
--- a/api/ruxos_posix_api/src/imp/rt_sig.rs
+++ b/api/ruxos_posix_api/src/imp/rt_sig.rs
@@ -11,7 +11,10 @@
 
 use axerrno::LinuxError;
 
-use crate::ctypes;
+use crate::{
+    ctypes::{self, k_sigaction},
+    sys_sigaction,
+};
 use core::{
     ffi::c_int,
     sync::atomic::{AtomicUsize, Ordering},
@@ -91,5 +94,30 @@ pub fn sys_rt_sigaction(
     _sigsetsize: ctypes::size_t,
 ) -> c_int {
     debug!("sys_rt_sigaction <= sig: {}", sig);
-    syscall_body!(sys_rt_sigaction, Ok(0))
+    syscall_body!(sys_rt_sigaction, {
+        unsafe {
+            let _sa = (*_sa).clone();
+            let _old = (*_old).clone();
+            let sa = k_sigaction::from(_sa);
+            let mut old_sa = k_sigaction::from(_old);
+            sys_sigaction(sig as _, Some(&sa), Some(&mut old_sa));
+        }
+        Ok(0)
+    })
+}
+
+impl From<ctypes::sigaction> for k_sigaction {
+    fn from(sa: ctypes::sigaction) -> Self {
+        let mut ret = Self {
+            ..Default::default()
+        };
+        ret.flags = sa.sa_flags as _;
+        let mask = sa.sa_mask.__bits[0]; // only get the first 64 signals
+        ret.mask[0] = mask as _;
+        ret.mask[1] = (mask >> 32) as _;
+
+        ret.handler = unsafe { sa.__sa_handler.sa_handler.clone() };
+        ret.restorer = sa.sa_restorer.clone();
+        ret
+    }
 }
diff --git a/api/ruxos_posix_api/src/imp/signal.rs b/api/ruxos_posix_api/src/imp/signal.rs
index 971408dc1..cffc3fd3e 100644
--- a/api/ruxos_posix_api/src/imp/signal.rs
+++ b/api/ruxos_posix_api/src/imp/signal.rs
@@ -86,8 +86,24 @@ pub unsafe fn sys_sigaltstack(
     syscall_body!(sys_sigaltstack, Ok(0))
 }
 
-/// TODO: send a signal to a process
-pub unsafe fn sys_kill(pid: pid_t, sig: c_int) -> c_int {
+/// send a signal to a process
+pub fn sys_kill(pid: pid_t, sig: c_int) -> c_int {
     debug!("sys_kill <= pid {} sig {}", pid, sig);
-    syscall_body!(sys_kill, Ok(0))
+    syscall_body!(sys_kill, {
+        match Signal::signal(sig as _, true) {
+            None => Err(LinuxError::EINVAL),
+            Some(_) => Ok(0),
+        }
+    })
+}
+
+/// send a signal to a thread
+pub fn sys_tkill(tid: pid_t, sig: c_int) -> c_int {
+    debug!("sys_tkill <= tid {} sig {}", tid, sig);
+    syscall_body!(sys_kill, {
+        match Signal::signal(sig as _, true) {
+            None => Err(LinuxError::EINVAL),
+            Some(_) => Ok(0),
+        }
+    })
 }
diff --git a/api/ruxos_posix_api/src/lib.rs b/api/ruxos_posix_api/src/lib.rs
index 263134c42..4e1c44086 100644
--- a/api/ruxos_posix_api/src/lib.rs
+++ b/api/ruxos_posix_api/src/lib.rs
@@ -50,7 +50,6 @@ pub use imp::getrandom::{sys_getrandom, sys_rand, sys_random, sys_srand};
 pub use imp::io::{sys_read, sys_readv, sys_write, sys_writev};
 pub use imp::prctl::{sys_arch_prctl, sys_prctl};
 pub use imp::resources::{sys_getrlimit, sys_prlimit64, sys_setrlimit};
-pub use imp::rt_sig::{sys_rt_sigaction, sys_rt_sigprocmask};
 pub use imp::stat::{
     sys_getegid, sys_geteuid, sys_getgid, sys_getpgid, sys_getuid, sys_setgid, sys_setpgid,
     sys_setuid, sys_umask,
@@ -107,7 +106,11 @@ pub use imp::pthread::{
     sys_pthread_setspecific,
 };
 #[cfg(feature = "signal")]
-pub use imp::signal::{sys_getitimer, sys_kill, sys_setitimer, sys_sigaction, sys_sigaltstack};
+pub use imp::rt_sig::{sys_rt_sigaction, sys_rt_sigprocmask};
+#[cfg(feature = "signal")]
+pub use imp::signal::{
+    sys_getitimer, sys_kill, sys_setitimer, sys_sigaction, sys_sigaltstack, sys_tkill,
+};
 
 #[cfg(feature = "multitask")]
 pub use imp::pthread::futex::sys_futex;
diff --git a/ulib/ruxmusl/src/aarch64/mod.rs b/ulib/ruxmusl/src/aarch64/mod.rs
index a1dbe05f4..519972584 100644
--- a/ulib/ruxmusl/src/aarch64/mod.rs
+++ b/ulib/ruxmusl/src/aarch64/mod.rs
@@ -228,6 +228,8 @@ pub fn syscall(syscall_id: SyscallId, args: [usize; 6]) -> isize {
             #[cfg(feature = "signal")]
             SyscallId::KILL => ruxos_posix_api::sys_kill(args[0] as pid_t, args[1] as c_int) as _,
             #[cfg(feature = "signal")]
+            SyscallId::TKILL => ruxos_posix_api::sys_tkill(args[0] as pid_t, args[1] as c_int) as _,
+            #[cfg(feature = "signal")]
             SyscallId::SIGALTSTACK => ruxos_posix_api::sys_sigaltstack(
                 args[0] as *const core::ffi::c_void,
                 args[1] as *mut core::ffi::c_void,
diff --git a/ulib/ruxmusl/src/aarch64/syscall_id.rs b/ulib/ruxmusl/src/aarch64/syscall_id.rs
index c4b8e4307..2eff2855b 100644
--- a/ulib/ruxmusl/src/aarch64/syscall_id.rs
+++ b/ulib/ruxmusl/src/aarch64/syscall_id.rs
@@ -84,6 +84,8 @@ pub enum SyscallId {
     #[cfg(feature = "signal")]
     KILL = 129,
     #[cfg(feature = "signal")]
+    TKILL = 130,
+    #[cfg(feature = "signal")]
     SIGALTSTACK = 132,
     #[cfg(feature = "signal")]
     RT_SIGACTION = 134,