Index: sys/amd64/linux/linux_machdep.c
===================================================================
--- sys/amd64/linux/linux_machdep.c
+++ sys/amd64/linux/linux_machdep.c
@@ -188,37 +188,6 @@
 	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
@@ -549,34 +549,6 @@
 	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
@@ -55,7 +55,6 @@
 
 /* DTrace probes */
 LIN_SDT_PROBE_DEFINE0(machdep, linux_mmap2, todo);
-LIN_SDT_PROBE_DEFINE0(machdep, linux_sigaltstack, todo);
 
 /*
  * LINUXTODO: deduplicate; linux_execve is common across archs, except that on
@@ -123,15 +122,6 @@
 	return (linux_madvise_common(td, PTROUT(uap->addr), uap->len, uap->behav));
 }
 
-/* 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
@@ -31,6 +31,7 @@
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/ktr.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
 #include <sys/sx.h>
@@ -184,6 +185,37 @@
 	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.h
===================================================================
--- sys/i386/linux/linux.h
+++ sys/i386/linux/linux.h
@@ -257,7 +257,7 @@
 } l_sigaction_t;
 
 typedef struct {
-	void		*ss_sp;
+	l_uintptr_t	ss_sp;
 	l_int		ss_flags;
 	l_size_t	ss_size;
 } l_stack_t;
Index: sys/i386/linux/linux_machdep.c
===================================================================
--- sys/i386/linux/linux_machdep.c
+++ sys/i386/linux/linux_machdep.c
@@ -517,34 +517,6 @@
 	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)
 {
Index: sys/i386/linux/linux_sysvec.c
===================================================================
--- sys/i386/linux/linux_sysvec.c
+++ sys/i386/linux/linux_sysvec.c
@@ -441,7 +441,7 @@
 	frame.sf_sc.uc_flags = 0;		/* XXX ??? */
 	frame.sf_sc.uc_link = NULL;		/* XXX ??? */
 
-	frame.sf_sc.uc_stack.ss_sp = td->td_sigstk.ss_sp;
+	frame.sf_sc.uc_stack.ss_sp = PTROUT(td->td_sigstk.ss_sp);
 	frame.sf_sc.uc_stack.ss_size = td->td_sigstk.ss_size;
 	frame.sf_sc.uc_stack.ss_flags = (td->td_pflags & TDP_ALTSTACK)
 	    ? ((oonstack) ? LINUX_SS_ONSTACK : 0) : LINUX_SS_DISABLE;
@@ -751,7 +751,7 @@
 
 	/* Call sigaltstack & ignore results. */
 	lss = &uc.uc_stack;
-	ss.ss_sp = lss->ss_sp;
+	ss.ss_sp = PTRIN(lss->ss_sp);
 	ss.ss_size = lss->ss_size;
 	ss.ss_flags = linux_to_bsd_sigaltstack(lss->ss_flags);