Index: sys/amd64/linux/linux_machdep.c
===================================================================
--- sys/amd64/linux/linux_machdep.c
+++ sys/amd64/linux/linux_machdep.c
@@ -209,37 +209,6 @@
 	return (kern_sigsuspend(td, sigmask));
 }
 
-int
-linux_sigaltstack(struct thread *td, struct linux_sigaltstack_args *uap)
-{
-	stack_t ss, oss;
-	l_stack_t lss;
-	int error;
-
-	memset(&lss, 0, sizeof(lss));
-	LINUX_CTR2(sigaltstack, "%p, %p", uap->uss, uap->uoss);
-
-	if (uap->uss != NULL) {
-		error = copyin(uap->uss, &lss, sizeof(l_stack_t));
-		if (error)
-			return (error);
-
-		ss.ss_sp = PTRIN(lss.ss_sp);
-		ss.ss_size = lss.ss_size;
-		ss.ss_flags = linux_to_bsd_sigaltstack(lss.ss_flags);
-	}
-	error = kern_sigaltstack(td, (uap->uss != NULL) ? &ss : NULL,
-	    (uap->uoss != NULL) ? &oss : NULL);
-	if (!error && uap->uoss != NULL) {
-		lss.ss_sp = PTROUT(oss.ss_sp);
-		lss.ss_size = oss.ss_size;
-		lss.ss_flags = bsd_to_linux_sigaltstack(oss.ss_flags);
-		error = copyout(&lss, uap->uoss, sizeof(l_stack_t));
-	}
-
-	return (error);
-}
-
 int
 linux_arch_prctl(struct thread *td, struct linux_arch_prctl_args *args)
 {
Index: sys/amd64/linux32/linux32_machdep.c
===================================================================
--- sys/amd64/linux32/linux32_machdep.c
+++ sys/amd64/linux32/linux32_machdep.c
@@ -567,34 +567,6 @@
 	return (kern_sigsuspend(td, sigmask));
 }
 
-int
-linux_sigaltstack(struct thread *td, struct linux_sigaltstack_args *uap)
-{
-	stack_t ss, oss;
-	l_stack_t lss;
-	int error;
-
-	if (uap->uss != NULL) {
-		error = copyin(uap->uss, &lss, sizeof(l_stack_t));
-		if (error)
-			return (error);
-
-		ss.ss_sp = PTRIN(lss.ss_sp);
-		ss.ss_size = lss.ss_size;
-		ss.ss_flags = linux_to_bsd_sigaltstack(lss.ss_flags);
-	}
-	error = kern_sigaltstack(td, (uap->uss != NULL) ? &ss : NULL,
-	    (uap->uoss != NULL) ? &oss : NULL);
-	if (!error && uap->uoss != NULL) {
-		lss.ss_sp = PTROUT(oss.ss_sp);
-		lss.ss_size = oss.ss_size;
-		lss.ss_flags = bsd_to_linux_sigaltstack(oss.ss_flags);
-		error = copyout(&lss, uap->uoss, sizeof(l_stack_t));
-	}
-
-	return (error);
-}
-
 int
 linux_gettimeofday(struct thread *td, struct linux_gettimeofday_args *uap)
 {
Index: sys/arm64/linux/linux_machdep.c
===================================================================
--- sys/arm64/linux/linux_machdep.c
+++ sys/arm64/linux/linux_machdep.c
@@ -56,7 +56,6 @@
 /* DTrace probes */
 LIN_SDT_PROBE_DEFINE0(machdep, linux_mmap2, todo);
 LIN_SDT_PROBE_DEFINE0(machdep, linux_rt_sigsuspend, todo);
-LIN_SDT_PROBE_DEFINE0(machdep, linux_sigaltstack, todo);
 
 /*
  * LINUXTODO: deduplicate; linux_execve is common across archs, except that on
@@ -133,15 +132,6 @@
 	return (EDOOFUS);
 }
 
-/* LINUXTODO: implement arm64 linux_sigaltstack */
-int
-linux_sigaltstack(struct thread *td, struct linux_sigaltstack_args *uap)
-{
-
-	LIN_SDT_PROBE0(machdep, linux_sigaltstack, todo);
-	return (EDOOFUS);
-}
-
 int
 linux_set_cloned_tls(struct thread *td, void *desc)
 {
Index: sys/compat/linux/linux_signal.c
===================================================================
--- sys/compat/linux/linux_signal.c
+++ sys/compat/linux/linux_signal.c
@@ -184,6 +184,37 @@
 	return (0);
 }
 
+int
+linux_sigaltstack(struct thread *td, struct linux_sigaltstack_args *uap)
+{
+	stack_t ss, oss;
+	l_stack_t lss;
+	int error;
+
+	memset(&lss, 0, sizeof(lss));
+	LINUX_CTR2(sigaltstack, "%p, %p", uap->uss, uap->uoss);
+
+	if (uap->uss != NULL) {
+		error = copyin(uap->uss, &lss, sizeof(l_stack_t));
+		if (error)
+			return (error);
+
+		ss.ss_sp = PTRIN(lss.ss_sp);
+		ss.ss_size = lss.ss_size;
+		ss.ss_flags = linux_to_bsd_sigaltstack(lss.ss_flags);
+	}
+	error = kern_sigaltstack(td, (uap->uss != NULL) ? &ss : NULL,
+	    (uap->uoss != NULL) ? &oss : NULL);
+	if (!error && uap->uoss != NULL) {
+		lss.ss_sp = PTROUT(oss.ss_sp);
+		lss.ss_size = oss.ss_size;
+		lss.ss_flags = bsd_to_linux_sigaltstack(oss.ss_flags);
+		error = copyout(&lss, uap->uoss, sizeof(l_stack_t));
+	}
+
+	return (error);
+}
+
 #if defined(__i386__) || (defined(__amd64__) && defined(COMPAT_LINUX32))
 int
 linux_signal(struct thread *td, struct linux_signal_args *args)
Index: sys/i386/linux/linux_machdep.c
===================================================================
--- sys/i386/linux/linux_machdep.c
+++ sys/i386/linux/linux_machdep.c
@@ -535,34 +535,6 @@
 	return (kern_sigsuspend(td, sigmask));
 }
 
-int
-linux_sigaltstack(struct thread *td, struct linux_sigaltstack_args *uap)
-{
-	stack_t ss, oss;
-	l_stack_t lss;
-	int error;
-
-	if (uap->uss != NULL) {
-		error = copyin(uap->uss, &lss, sizeof(l_stack_t));
-		if (error)
-			return (error);
-
-		ss.ss_sp = lss.ss_sp;
-		ss.ss_size = lss.ss_size;
-		ss.ss_flags = linux_to_bsd_sigaltstack(lss.ss_flags);
-	}
-	error = kern_sigaltstack(td, (uap->uss != NULL) ? &ss : NULL,
-	    (uap->uoss != NULL) ? &oss : NULL);
-	if (!error && uap->uoss != NULL) {
-		lss.ss_sp = oss.ss_sp;
-		lss.ss_size = oss.ss_size;
-		lss.ss_flags = bsd_to_linux_sigaltstack(oss.ss_flags);
-		error = copyout(&lss, uap->uoss, sizeof(l_stack_t));
-	}
-
-	return (error);
-}
-
 int
 linux_set_thread_area(struct thread *td, struct linux_set_thread_area_args *args)
 {