diff --git a/lib/libc/sys/procctl.2 b/lib/libc/sys/procctl.2
index 432ed5919a8..ce7a2be5d5e 100644
--- a/lib/libc/sys/procctl.2
+++ b/lib/libc/sys/procctl.2
@@ -454,6 +454,16 @@ and the
 .Va si_code
 member is set to
 .Dv TRAP_CAP .
+The system call number is stored in the
+.Va si_syscall
+field of the
+.Fa siginfo
+signal handler parameter.
+The other system call parameters can be read from the
+.Fa ucontext_t
+but the system call number is typically stored in the register
+that also contains the return value and so is unavailable in the
+signal handler.
 .Pp
 See
 .Xr capsicum 4
diff --git a/share/man/man3/siginfo.3 b/share/man/man3/siginfo.3
index acc8785b2f0..7f8a809cdfa 100644
--- a/share/man/man3/siginfo.3
+++ b/share/man/man3/siginfo.3
@@ -85,6 +85,8 @@ timer overrun count
 .It Vt int Ta Va si_mqd Ta
 .Tn POSIX
 message queue ID
+.It Vt int Ta Va si_syscall Ta
+system-call number for system calls blocked by Capsicum
 .El
 .Pp
 The
diff --git a/sys/amd64/amd64/trap.c b/sys/amd64/amd64/trap.c
index 55649687ce5..b08495f3f13 100644
--- a/sys/amd64/amd64/trap.c
+++ b/sys/amd64/amd64/trap.c
@@ -1059,6 +1059,7 @@ cpu_fetch_syscall_args(struct thread *td)
 	sa = &td->td_sa;
 
 	sa->code = frame->tf_rax;
+	sa->original_code = sa->code;
 
 	if (__predict_false(sa->code == SYS_syscall ||
 	    sa->code == SYS___syscall ||
diff --git a/sys/amd64/cloudabi32/cloudabi32_sysvec.c b/sys/amd64/cloudabi32/cloudabi32_sysvec.c
index 164f87e90e9..26924ed5a98 100644
--- a/sys/amd64/cloudabi32/cloudabi32_sysvec.c
+++ b/sys/amd64/cloudabi32/cloudabi32_sysvec.c
@@ -101,6 +101,7 @@ cloudabi32_fetch_syscall_args(struct thread *td)
 
 	/* Obtain system call number. */
 	sa->code = frame->tf_rax;
+	sa->original_code = sa->code;
 	if (sa->code >= CLOUDABI32_SYS_MAXSYSCALL)
 		return (ENOSYS);
 	sa->callp = &cloudabi32_sysent[sa->code];
diff --git a/sys/amd64/cloudabi64/cloudabi64_sysvec.c b/sys/amd64/cloudabi64/cloudabi64_sysvec.c
index d3893902b08..c08d912e84d 100644
--- a/sys/amd64/cloudabi64/cloudabi64_sysvec.c
+++ b/sys/amd64/cloudabi64/cloudabi64_sysvec.c
@@ -98,6 +98,7 @@ cloudabi64_fetch_syscall_args(struct thread *td)
 
 	/* Obtain system call number. */
 	sa->code = frame->tf_rax;
+	sa->original_code = sa->code;
 	if (sa->code >= CLOUDABI64_SYS_MAXSYSCALL)
 		return (ENOSYS);
 	sa->callp = &cloudabi64_sysent[sa->code];
diff --git a/sys/amd64/ia32/ia32_syscall.c b/sys/amd64/ia32/ia32_syscall.c
index 6c9399d1a52..9294ef8ce74 100644
--- a/sys/amd64/ia32/ia32_syscall.c
+++ b/sys/amd64/ia32/ia32_syscall.c
@@ -150,6 +150,7 @@ ia32_fetch_syscall_args(struct thread *td)
 
 	params = (caddr_t)frame->tf_rsp + sizeof(u_int32_t);
 	sa->code = frame->tf_rax;
+	sa->original_code = sa->code;
 
 	/*
 	 * Need to check if this is a 32 bit or 64 bit syscall.
diff --git a/sys/amd64/include/proc.h b/sys/amd64/include/proc.h
index 59796e729ac..0f8cf50e326 100644
--- a/sys/amd64/include/proc.h
+++ b/sys/amd64/include/proc.h
@@ -92,6 +92,7 @@ struct mdproc {
 
 struct syscall_args {
 	u_int code;
+	u_int original_code;
 	struct sysent *callp;
 	register_t args[8];
 };
diff --git a/sys/amd64/linux/linux_sysvec.c b/sys/amd64/linux/linux_sysvec.c
index c5538932b1e..566af6de29e 100644
--- a/sys/amd64/linux/linux_sysvec.c
+++ b/sys/amd64/linux/linux_sysvec.c
@@ -191,6 +191,7 @@ linux_fetch_syscall_args(struct thread *td)
 	sa->args[4] = frame->tf_r8;
 	sa->args[5] = frame->tf_r9;
 	sa->code = frame->tf_rax;
+	sa->original_code = sa->code;
 
 	if (sa->code >= p->p_sysent->sv_size)
 		/* nosys */
diff --git a/sys/amd64/linux32/linux32_sysvec.c b/sys/amd64/linux32/linux32_sysvec.c
index 504d57e418a..7dfd57a74a1 100644
--- a/sys/amd64/linux32/linux32_sysvec.c
+++ b/sys/amd64/linux32/linux32_sysvec.c
@@ -662,6 +662,7 @@ linux32_fetch_syscall_args(struct thread *td)
 	sa->args[4] = frame->tf_rdi;
 	sa->args[5] = frame->tf_rbp;	/* Unconfirmed */
 	sa->code = frame->tf_rax;
+	sa->original_code = sa->code;
 
 	if (sa->code >= p->p_sysent->sv_size)
 		/* nosys */
diff --git a/sys/arm/arm/syscall.c b/sys/arm/arm/syscall.c
index a851db6e455..a635de0ec71 100644
--- a/sys/arm/arm/syscall.c
+++ b/sys/arm/arm/syscall.c
@@ -108,6 +108,7 @@ cpu_fetch_syscall_args(struct thread *td)
 	nap = 4;
 	sa = &td->td_sa;
 	sa->code = td->td_frame->tf_r7;
+	sa->original_code = sa->code;
 	ap = &td->td_frame->tf_r0;
 	if (sa->code == SYS_syscall) {
 		sa->code = *ap++;
diff --git a/sys/arm/cloudabi32/cloudabi32_sysvec.c b/sys/arm/cloudabi32/cloudabi32_sysvec.c
index a8c5da47d26..4df57b22e13 100644
--- a/sys/arm/cloudabi32/cloudabi32_sysvec.c
+++ b/sys/arm/cloudabi32/cloudabi32_sysvec.c
@@ -78,6 +78,7 @@ cloudabi32_fetch_syscall_args(struct thread *td)
 
 	/* Obtain system call number. */
 	sa->code = frame->tf_r12;
+	sa->original_code = sa->code;
 	if (sa->code >= CLOUDABI32_SYS_MAXSYSCALL)
 		return (ENOSYS);
 	sa->callp = &cloudabi32_sysent[sa->code];
diff --git a/sys/arm/include/proc.h b/sys/arm/include/proc.h
index a37ccd8f621..9566c264731 100644
--- a/sys/arm/include/proc.h
+++ b/sys/arm/include/proc.h
@@ -75,6 +75,7 @@ struct mdproc {
  */
 struct syscall_args {
 	u_int code;
+	u_int original_code;
 	struct sysent *callp;
 	register_t args[MAXARGS];
 } __aligned(8);
diff --git a/sys/arm64/arm64/elf32_machdep.c b/sys/arm64/arm64/elf32_machdep.c
index 206413b4517..7cedbffc4d4 100644
--- a/sys/arm64/arm64/elf32_machdep.c
+++ b/sys/arm64/arm64/elf32_machdep.c
@@ -175,6 +175,7 @@ freebsd32_fetch_syscall_args(struct thread *td)
 
 	/* r7 is the syscall id */
 	sa->code = td->td_frame->tf_x[7];
+	sa->original_code = sa->code;
 
 	if (sa->code == SYS_syscall) {
 		sa->code = *ap++;
diff --git a/sys/arm64/arm64/trap.c b/sys/arm64/arm64/trap.c
index 744b646b31c..2b2d2e433ef 100644
--- a/sys/arm64/arm64/trap.c
+++ b/sys/arm64/arm64/trap.c
@@ -130,6 +130,7 @@ cpu_fetch_syscall_args(struct thread *td)
 	dst_ap = &sa->args[0];
 
 	sa->code = td->td_frame->tf_x[8];
+	sa->original_code = sa->code;
 
 	if (__predict_false(sa->code == SYS_syscall || sa->code == SYS___syscall)) {
 		sa->code = *ap++;
diff --git a/sys/arm64/cloudabi32/cloudabi32_sysvec.c b/sys/arm64/cloudabi32/cloudabi32_sysvec.c
index 889393560ed..b7be5cc0e5e 100644
--- a/sys/arm64/cloudabi32/cloudabi32_sysvec.c
+++ b/sys/arm64/cloudabi32/cloudabi32_sysvec.c
@@ -75,6 +75,7 @@ cloudabi32_fetch_syscall_args(struct thread *td)
 
 	/* Obtain system call number. */
 	sa->code = frame->tf_x[0];
+	sa->original_code = sa->code;
 	if (sa->code >= CLOUDABI32_SYS_MAXSYSCALL)
 		return (ENOSYS);
 	sa->callp = &cloudabi32_sysent[sa->code];
diff --git a/sys/arm64/cloudabi64/cloudabi64_sysvec.c b/sys/arm64/cloudabi64/cloudabi64_sysvec.c
index bdbd828b7b6..624d8669345 100644
--- a/sys/arm64/cloudabi64/cloudabi64_sysvec.c
+++ b/sys/arm64/cloudabi64/cloudabi64_sysvec.c
@@ -78,6 +78,7 @@ cloudabi64_fetch_syscall_args(struct thread *td)
 
 	/* Obtain system call number. */
 	sa->code = frame->tf_x[8];
+	sa->original_code = sa->code;
 	if (sa->code >= CLOUDABI64_SYS_MAXSYSCALL)
 		return (ENOSYS);
 	sa->callp = &cloudabi64_sysent[sa->code];
diff --git a/sys/arm64/include/proc.h b/sys/arm64/include/proc.h
index bb933dc9824..3800798d79b 100644
--- a/sys/arm64/include/proc.h
+++ b/sys/arm64/include/proc.h
@@ -49,6 +49,7 @@ struct mdproc {
 #define	MAXARGS		8
 struct syscall_args {
 	u_int code;
+	u_int original_code;
 	struct sysent *callp;
 	register_t args[MAXARGS];
 };
diff --git a/sys/arm64/linux/linux_sysvec.c b/sys/arm64/linux/linux_sysvec.c
index e1d3708b70e..7749c1cd7fc 100644
--- a/sys/arm64/linux/linux_sysvec.c
+++ b/sys/arm64/linux/linux_sysvec.c
@@ -125,6 +125,7 @@ linux_fetch_syscall_args(struct thread *td)
 	sa = &td->td_sa;
 
 	sa->code = td->td_frame->tf_x[8];
+	sa->original_code = sa->code;
 	/* LINUXTODO: generic syscall? */
 	if (sa->code >= p->p_sysent->sv_size)
 		sa->callp = &p->p_sysent->sv_table[0];
diff --git a/sys/i386/cloudabi32/cloudabi32_sysvec.c b/sys/i386/cloudabi32/cloudabi32_sysvec.c
index 4f12d2b6cbc..e0a50f6697a 100644
--- a/sys/i386/cloudabi32/cloudabi32_sysvec.c
+++ b/sys/i386/cloudabi32/cloudabi32_sysvec.c
@@ -96,6 +96,7 @@ cloudabi32_fetch_syscall_args(struct thread *td)
 
 	/* Obtain system call number. */
 	sa->code = frame->tf_eax;
+	sa->original_code = sa->code;
 	if (sa->code >= CLOUDABI32_SYS_MAXSYSCALL)
 		return (ENOSYS);
 	sa->callp = &cloudabi32_sysent[sa->code];
diff --git a/sys/i386/i386/trap.c b/sys/i386/i386/trap.c
index 045478149be..07abac23c9d 100644
--- a/sys/i386/i386/trap.c
+++ b/sys/i386/i386/trap.c
@@ -1052,6 +1052,7 @@ cpu_fetch_syscall_args(struct thread *td)
 #endif
 
 	sa->code = frame->tf_eax;
+	sa->original_code = sa->code;
 	params = (caddr_t)frame->tf_esp + sizeof(uint32_t);
 
 	/*
diff --git a/sys/i386/include/proc.h b/sys/i386/include/proc.h
index 2950946ff15..76e1ac61147 100644
--- a/sys/i386/include/proc.h
+++ b/sys/i386/include/proc.h
@@ -64,6 +64,7 @@ struct mdproc {
 
 struct syscall_args {
 	u_int code;
+	u_int original_code;
 	struct sysent *callp;
 	register_t args[8];
 };
diff --git a/sys/i386/linux/linux_sysvec.c b/sys/i386/linux/linux_sysvec.c
index adb70fded6d..a0959d55b58 100644
--- a/sys/i386/linux/linux_sysvec.c
+++ b/sys/i386/linux/linux_sysvec.c
@@ -756,6 +756,7 @@ linux_fetch_syscall_args(struct thread *td)
 	sa = &td->td_sa;
 
 	sa->code = frame->tf_eax;
+	sa->original_code = sa->code;
 	sa->args[0] = frame->tf_ebx;
 	sa->args[1] = frame->tf_ecx;
 	sa->args[2] = frame->tf_edx;
diff --git a/sys/kern/subr_syscall.c b/sys/kern/subr_syscall.c
index 85a0814a212..2304e3e7f3f 100644
--- a/sys/kern/subr_syscall.c
+++ b/sys/kern/subr_syscall.c
@@ -230,6 +230,7 @@ syscallret(struct thread *td)
 			ksi.ksi_signo = SIGTRAP;
 			ksi.ksi_errno = td->td_errno;
 			ksi.ksi_code = TRAP_CAP;
+			ksi.ksi_info.si_syscall = sa->original_code;
 			trapsignal(td, &ksi);
 		}
 	}
diff --git a/sys/mips/include/proc.h b/sys/mips/include/proc.h
index 0cb1d433387..29d832a162e 100644
--- a/sys/mips/include/proc.h
+++ b/sys/mips/include/proc.h
@@ -84,6 +84,7 @@ struct mdproc {
 #define	MAXARGS		8
 struct syscall_args {
 	u_int code;
+	u_int original_code;
 	struct sysent *callp;
 	register_t args[MAXARGS];
 };
diff --git a/sys/mips/mips/trap.c b/sys/mips/mips/trap.c
index 96a2de4ee81..9d7a0760637 100644
--- a/sys/mips/mips/trap.c
+++ b/sys/mips/mips/trap.c
@@ -355,6 +355,7 @@ cpu_fetch_syscall_args(struct thread *td)
 	else
 		locr0->pc += sizeof(int);
 	sa->code = locr0->v0;
+	sa->original_code = sa->code;
 
 	switch (sa->code) {
 	case SYS___syscall:
diff --git a/sys/powerpc/include/proc.h b/sys/powerpc/include/proc.h
index d4df3ccfefe..aac4e66b39f 100644
--- a/sys/powerpc/include/proc.h
+++ b/sys/powerpc/include/proc.h
@@ -62,6 +62,7 @@ struct mdproc {
 #define	MAXARGS		8
 struct syscall_args {
 	u_int code;
+	u_int original_code;
 	struct sysent *callp;
 	register_t args[MAXARGS];
 };
diff --git a/sys/powerpc/powerpc/trap.c b/sys/powerpc/powerpc/trap.c
index 3a1bdf7cde0..ab5189a0f41 100644
--- a/sys/powerpc/powerpc/trap.c
+++ b/sys/powerpc/powerpc/trap.c
@@ -667,6 +667,7 @@ cpu_fetch_syscall_args(struct thread *td)
 	sa = &td->td_sa;
 
 	sa->code = frame->fixreg[0];
+	sa->original_code = sa->code;
 	params = (caddr_t)(frame->fixreg + FIRSTARG);
 	n = NARGREG;
 
diff --git a/sys/riscv/include/proc.h b/sys/riscv/include/proc.h
index 4b5ae9ebe3e..1c6c8d2919b 100644
--- a/sys/riscv/include/proc.h
+++ b/sys/riscv/include/proc.h
@@ -48,6 +48,7 @@ struct mdproc {
 #define	MAXARGS		8
 struct syscall_args {
 	u_int code;
+	u_int original_code;
 	struct sysent *callp;
 	register_t args[MAXARGS];
 };
diff --git a/sys/riscv/riscv/trap.c b/sys/riscv/riscv/trap.c
index 07d7f84a94e..8844638c820 100644
--- a/sys/riscv/riscv/trap.c
+++ b/sys/riscv/riscv/trap.c
@@ -103,6 +103,7 @@ cpu_fetch_syscall_args(struct thread *td)
 	dst_ap = &sa->args[0];
 
 	sa->code = td->td_frame->tf_t[0];
+	sa->original_code = sa->code;
 
 	if (__predict_false(sa->code == SYS_syscall || sa->code == SYS___syscall)) {
 		sa->code = *ap++;
diff --git a/sys/sys/signal.h b/sys/sys/signal.h
index 8b45a521c3e..9dae3ce0474 100644
--- a/sys/sys/signal.h
+++ b/sys/sys/signal.h
@@ -255,6 +255,12 @@ typedef	struct __siginfo {
 		struct {
 			long	_band;		/* band event for SIGPOLL */
 		} _poll;			/* was this ever used ? */
+		struct {
+			int	_syscall;	/* Syscall number for signals
+						 * delivered as a result of
+						 * system calls denied by
+						 * Capsicum. */
+		} _capsicum;
 		struct {
 			long	__spare1__;
 			int	__spare2__[7];
@@ -267,6 +273,7 @@ typedef	struct __siginfo {
 #define si_overrun	_reason._timer._overrun
 #define si_mqd		_reason._mesgq._mqd
 #define si_band		_reason._poll._band
+#define si_syscall	_reason._capsicum._syscall
 
 #if defined(_WANT_LWPINFO32) || (defined(_KERNEL) && defined(__LP64__))
 struct siginfo32 {