diff --git a/sys/compat/freebsd32/freebsd32_syscall.h b/sys/compat/freebsd32/freebsd32_syscall.h
index bcdb1579cb57..6f91a1190a1c 100644
--- a/sys/compat/freebsd32/freebsd32_syscall.h
+++ b/sys/compat/freebsd32/freebsd32_syscall.h
@@ -499,4 +499,5 @@
 #define	FREEBSD32_SYS_freebsd32___sysctlbyname	570
 #define	FREEBSD32_SYS_shm_open2	571
 #define	FREEBSD32_SYS_shm_rename	572
-#define	FREEBSD32_SYS_MAXSYSCALL	573
+#define	FREEBSD32_SYS_sigfastblock	573
+#define	FREEBSD32_SYS_MAXSYSCALL	574
diff --git a/sys/compat/freebsd32/freebsd32_syscalls.c b/sys/compat/freebsd32/freebsd32_syscalls.c
index 223c6772829b..deefa2d22630 100644
--- a/sys/compat/freebsd32/freebsd32_syscalls.c
+++ b/sys/compat/freebsd32/freebsd32_syscalls.c
@@ -609,4 +609,5 @@ const char *freebsd32_syscallnames[] = {
 	"freebsd32___sysctlbyname",			/* 570 = freebsd32___sysctlbyname */
 	"shm_open2",			/* 571 = shm_open2 */
 	"shm_rename",			/* 572 = shm_rename */
+	"sigfastblock",			/* 573 = sigfastblock */
 };
diff --git a/sys/compat/freebsd32/freebsd32_sysent.c b/sys/compat/freebsd32/freebsd32_sysent.c
index 52baae6c02b7..b703c0fa1e3b 100644
--- a/sys/compat/freebsd32/freebsd32_sysent.c
+++ b/sys/compat/freebsd32/freebsd32_sysent.c
@@ -662,4 +662,5 @@ struct sysent freebsd32_sysent[] = {
 	{ AS(freebsd32___sysctlbyname_args), (sy_call_t *)freebsd32___sysctlbyname, AUE_SYSCTL, NULL, 0, 0, SYF_CAPENABLED, SY_THR_STATIC },	/* 570 = freebsd32___sysctlbyname */
 	{ AS(shm_open2_args), (sy_call_t *)sys_shm_open2, AUE_SHMOPEN, NULL, 0, 0, SYF_CAPENABLED, SY_THR_STATIC },	/* 571 = shm_open2 */
 	{ AS(shm_rename_args), (sy_call_t *)sys_shm_rename, AUE_SHMRENAME, NULL, 0, 0, 0, SY_THR_STATIC },	/* 572 = shm_rename */
+	{ AS(sigfastblock_args), (sy_call_t *)sys_sigfastblock, AUE_NULL, NULL, 0, 0, SYF_CAPENABLED, SY_THR_STATIC },	/* 573 = sigfastblock */
 };
diff --git a/sys/compat/freebsd32/freebsd32_systrace_args.c b/sys/compat/freebsd32/freebsd32_systrace_args.c
index 178bbf0a8427..2abc302f3079 100644
--- a/sys/compat/freebsd32/freebsd32_systrace_args.c
+++ b/sys/compat/freebsd32/freebsd32_systrace_args.c
@@ -3355,6 +3355,14 @@ systrace_args(int sysnum, void *params, uint64_t *uarg, int *n_args)
 		*n_args = 3;
 		break;
 	}
+	/* sigfastblock */
+	case 573: {
+		struct sigfastblock_args *p = params;
+		iarg[0] = p->cmd; /* int */
+		uarg[1] = (intptr_t) p->ptr; /* uint32_t * */
+		*n_args = 2;
+		break;
+	}
 	default:
 		*n_args = 0;
 		break;
@@ -9041,6 +9049,19 @@ systrace_entry_setargdesc(int sysnum, int ndx, char *desc, size_t descsz)
 			break;
 		};
 		break;
+	/* sigfastblock */
+	case 573:
+		switch(ndx) {
+		case 0:
+			p = "int";
+			break;
+		case 1:
+			p = "userland uint32_t *";
+			break;
+		default:
+			break;
+		};
+		break;
 	default:
 		break;
 	};
@@ -10930,6 +10951,11 @@ systrace_return_setargdesc(int sysnum, int ndx, char *desc, size_t descsz)
 		if (ndx == 0 || ndx == 1)
 			p = "int";
 		break;
+	/* sigfastblock */
+	case 573:
+		if (ndx == 0 || ndx == 1)
+			p = "int";
+		break;
 	default:
 		break;
 	};
diff --git a/sys/kern/init_sysent.c b/sys/kern/init_sysent.c
index b64105fdea34..edb76ee279ae 100644
--- a/sys/kern/init_sysent.c
+++ b/sys/kern/init_sysent.c
@@ -628,4 +628,5 @@ struct sysent sysent[] = {
 	{ AS(__sysctlbyname_args), (sy_call_t *)sys___sysctlbyname, AUE_SYSCTL, NULL, 0, 0, SYF_CAPENABLED, SY_THR_STATIC },	/* 570 = __sysctlbyname */
 	{ AS(shm_open2_args), (sy_call_t *)sys_shm_open2, AUE_SHMOPEN, NULL, 0, 0, SYF_CAPENABLED, SY_THR_STATIC },	/* 571 = shm_open2 */
 	{ AS(shm_rename_args), (sy_call_t *)sys_shm_rename, AUE_SHMRENAME, NULL, 0, 0, 0, SY_THR_STATIC },	/* 572 = shm_rename */
+	{ AS(sigfastblock_args), (sy_call_t *)sys_sigfastblock, AUE_NULL, NULL, 0, 0, SYF_CAPENABLED, SY_THR_STATIC },	/* 573 = sigfastblock */
 };
diff --git a/sys/kern/syscalls.c b/sys/kern/syscalls.c
index 3daa26a41f09..0df4e03756eb 100644
--- a/sys/kern/syscalls.c
+++ b/sys/kern/syscalls.c
@@ -579,4 +579,5 @@ const char *syscallnames[] = {
 	"__sysctlbyname",			/* 570 = __sysctlbyname */
 	"shm_open2",			/* 571 = shm_open2 */
 	"shm_rename",			/* 572 = shm_rename */
+	"sigfastblock",			/* 573 = sigfastblock */
 };
diff --git a/sys/kern/systrace_args.c b/sys/kern/systrace_args.c
index 01a9a4e63cbb..346415a69787 100644
--- a/sys/kern/systrace_args.c
+++ b/sys/kern/systrace_args.c
@@ -3347,6 +3347,14 @@ systrace_args(int sysnum, void *params, uint64_t *uarg, int *n_args)
 		*n_args = 3;
 		break;
 	}
+	/* sigfastblock */
+	case 573: {
+		struct sigfastblock_args *p = params;
+		iarg[0] = p->cmd; /* int */
+		uarg[1] = (intptr_t) p->ptr; /* uint32_t * */
+		*n_args = 2;
+		break;
+	}
 	default:
 		*n_args = 0;
 		break;
@@ -8946,6 +8954,19 @@ systrace_entry_setargdesc(int sysnum, int ndx, char *desc, size_t descsz)
 			break;
 		};
 		break;
+	/* sigfastblock */
+	case 573:
+		switch(ndx) {
+		case 0:
+			p = "int";
+			break;
+		case 1:
+			p = "userland uint32_t *";
+			break;
+		default:
+			break;
+		};
+		break;
 	default:
 		break;
 	};
@@ -10862,6 +10883,11 @@ systrace_return_setargdesc(int sysnum, int ndx, char *desc, size_t descsz)
 		if (ndx == 0 || ndx == 1)
 			p = "int";
 		break;
+	/* sigfastblock */
+	case 573:
+		if (ndx == 0 || ndx == 1)
+			p = "int";
+		break;
 	default:
 		break;
 	};
diff --git a/sys/sys/syscall.h b/sys/sys/syscall.h
index bfe648fa0808..5b183036661f 100644
--- a/sys/sys/syscall.h
+++ b/sys/sys/syscall.h
@@ -508,4 +508,5 @@
 #define	SYS___sysctlbyname	570
 #define	SYS_shm_open2	571
 #define	SYS_shm_rename	572
-#define	SYS_MAXSYSCALL	573
+#define	SYS_sigfastblock	573
+#define	SYS_MAXSYSCALL	574
diff --git a/sys/sys/syscall.mk b/sys/sys/syscall.mk
index 269010e25e71..c095831023a4 100644
--- a/sys/sys/syscall.mk
+++ b/sys/sys/syscall.mk
@@ -413,4 +413,5 @@ MIASM =  \
 	copy_file_range.o \
 	__sysctlbyname.o \
 	shm_open2.o \
-	shm_rename.o
+	shm_rename.o \
+	sigfastblock.o
diff --git a/sys/sys/sysproto.h b/sys/sys/sysproto.h
index 05acc23c5a07..6817ecf6f4ee 100644
--- a/sys/sys/sysproto.h
+++ b/sys/sys/sysproto.h
@@ -1819,6 +1819,10 @@ struct shm_rename_args {
 	char path_to_l_[PADL_(const char *)]; const char * path_to; char path_to_r_[PADR_(const char *)];
 	char flags_l_[PADL_(int)]; int flags; char flags_r_[PADR_(int)];
 };
+struct sigfastblock_args {
+	char cmd_l_[PADL_(int)]; int cmd; char cmd_r_[PADR_(int)];
+	char ptr_l_[PADL_(uint32_t *)]; uint32_t * ptr; char ptr_r_[PADR_(uint32_t *)];
+};
 int	nosys(struct thread *, struct nosys_args *);
 void	sys_sys_exit(struct thread *, struct sys_exit_args *);
 int	sys_fork(struct thread *, struct fork_args *);
@@ -2207,6 +2211,7 @@ int	sys_copy_file_range(struct thread *, struct copy_file_range_args *);
 int	sys___sysctlbyname(struct thread *, struct __sysctlbyname_args *);
 int	sys_shm_open2(struct thread *, struct shm_open2_args *);
 int	sys_shm_rename(struct thread *, struct shm_rename_args *);
+int	sys_sigfastblock(struct thread *, struct sigfastblock_args *);
 
 #ifdef COMPAT_43
 
@@ -3130,6 +3135,7 @@ int	freebsd12_shm_open(struct thread *, struct freebsd12_shm_open_args *);
 #define	SYS_AUE___sysctlbyname	AUE_SYSCTL
 #define	SYS_AUE_shm_open2	AUE_SHMOPEN
 #define	SYS_AUE_shm_rename	AUE_SHMRENAME
+#define	SYS_AUE_sigfastblock	AUE_NULL
 
 #undef PAD_
 #undef PADL_