diff --git a/sys/amd64/amd64/trap.c b/sys/amd64/amd64/trap.c
index d77cbedd383c..7fef80d1ff30 100644
--- a/sys/amd64/amd64/trap.c
+++ b/sys/amd64/amd64/trap.c
@@ -829,16 +829,18 @@ dblfault_handler(struct trapframe *frame)
 }
 
 int
-cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+cpu_fetch_syscall_args(struct thread *td)
 {
 	struct proc *p;
 	struct trapframe *frame;
 	register_t *argp;
+	struct syscall_args *sa;
 	caddr_t params;
 	int reg, regcnt, error;
 
 	p = td->td_proc;
 	frame = td->td_frame;
+	sa = &td->td_sa;
 	reg = 0;
 	regcnt = 6;
 
@@ -889,7 +891,6 @@ cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
 void
 amd64_syscall(struct thread *td, int traced)
 {
-	struct syscall_args sa;
 	int error;
 	ksiginfo_t ksi;
 
@@ -899,7 +900,7 @@ amd64_syscall(struct thread *td, int traced)
 		/* NOT REACHED */
 	}
 #endif
-	error = syscallenter(td, &sa);
+	error = syscallenter(td);
 
 	/*
 	 * Traced syscall.
@@ -915,15 +916,16 @@ amd64_syscall(struct thread *td, int traced)
 
 	KASSERT(PCB_USER_FPU(td->td_pcb),
 	    ("System call %s returning with kernel FPU ctx leaked",
-	     syscallname(td->td_proc, sa.code)));
+	     syscallname(td->td_proc, td->td_sa.code)));
 	KASSERT(td->td_pcb->pcb_save == get_pcb_user_save_td(td),
 	    ("System call %s returning with mangled pcb_save",
-	     syscallname(td->td_proc, sa.code)));
+	     syscallname(td->td_proc, td->td_sa.code)));
 	KASSERT(td->td_md.md_invl_gen.gen == 0,
 	    ("System call %s returning with leaked invl_gen %lu",
-	    syscallname(td->td_proc, sa.code), td->td_md.md_invl_gen.gen));
+	    syscallname(td->td_proc, td->td_sa.code),
+	    td->td_md.md_invl_gen.gen));
 
-	syscallret(td, error, &sa);
+	syscallret(td, error);
 
 	/*
 	 * If the user-supplied value of %rip is not a canonical
diff --git a/sys/amd64/cloudabi32/cloudabi32_sysvec.c b/sys/amd64/cloudabi32/cloudabi32_sysvec.c
index abede1ac4ce1..d5dd58cfa6d6 100644
--- a/sys/amd64/cloudabi32/cloudabi32_sysvec.c
+++ b/sys/amd64/cloudabi32/cloudabi32_sysvec.c
@@ -90,11 +90,15 @@ cloudabi32_proc_setregs(struct thread *td, struct image_params *imgp,
 }
 
 static int
-cloudabi32_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+cloudabi32_fetch_syscall_args(struct thread *td)
 {
-	struct trapframe *frame = td->td_frame;
+	struct trapframe *frame;
+	struct syscall_args *sa;
 	int error;
 
+	frame = td->td_frame;
+	sa = &td->td_sa;
+
 	/* Obtain system call number. */
 	sa->code = frame->tf_rax;
 	if (sa->code >= CLOUDABI32_SYS_MAXSYSCALL)
diff --git a/sys/amd64/cloudabi64/cloudabi64_sysvec.c b/sys/amd64/cloudabi64/cloudabi64_sysvec.c
index 84f0cb387de7..679888bf52ad 100644
--- a/sys/amd64/cloudabi64/cloudabi64_sysvec.c
+++ b/sys/amd64/cloudabi64/cloudabi64_sysvec.c
@@ -87,9 +87,13 @@ cloudabi64_proc_setregs(struct thread *td, struct image_params *imgp,
 }
 
 static int
-cloudabi64_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+cloudabi64_fetch_syscall_args(struct thread *td)
 {
-	struct trapframe *frame = td->td_frame;
+	struct trapframe *frame;
+	struct syscall_args *sa;
+
+	frame = td->td_frame;
+	sa = &td->td_sa;
 
 	/* Obtain system call number. */
 	sa->code = frame->tf_rax;
diff --git a/sys/amd64/ia32/ia32_syscall.c b/sys/amd64/ia32/ia32_syscall.c
index 6e96eddb00af..c07b38cb438a 100644
--- a/sys/amd64/ia32/ia32_syscall.c
+++ b/sys/amd64/ia32/ia32_syscall.c
@@ -105,16 +105,18 @@ ia32_set_syscall_retval(struct thread *td, int error)
 }
 
 int
-ia32_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+ia32_fetch_syscall_args(struct thread *td)
 {
 	struct proc *p;
 	struct trapframe *frame;
+	struct syscall_args *sa;
 	caddr_t params;
 	u_int32_t args[8], tmp;
 	int error, i;
 
 	p = td->td_proc;
 	frame = td->td_frame;
+	sa = &td->td_sa;
 
 	params = (caddr_t)frame->tf_rsp + sizeof(u_int32_t);
 	sa->code = frame->tf_rax;
@@ -175,7 +177,6 @@ void
 ia32_syscall(struct trapframe *frame)
 {
 	struct thread *td;
-	struct syscall_args sa;
 	register_t orig_tf_rflags;
 	int error;
 	ksiginfo_t ksi;
@@ -184,7 +185,7 @@ ia32_syscall(struct trapframe *frame)
 	td = curthread;
 	td->td_frame = frame;
 
-	error = syscallenter(td, &sa);
+	error = syscallenter(td);
 
 	/*
 	 * Traced syscall.
@@ -198,7 +199,7 @@ ia32_syscall(struct trapframe *frame)
 		trapsignal(td, &ksi);
 	}
 
-	syscallret(td, error, &sa);
+	syscallret(td, error);
 }
 
 static void
diff --git a/sys/amd64/linux/linux_sysvec.c b/sys/amd64/linux/linux_sysvec.c
index 6e12d41a8f0e..f77c2c943524 100644
--- a/sys/amd64/linux/linux_sysvec.c
+++ b/sys/amd64/linux/linux_sysvec.c
@@ -126,7 +126,7 @@ static boolean_t linux_trans_osrel(const Elf_Note *note, int32_t *osrel);
 static void	linux_vdso_install(void *param);
 static void	linux_vdso_deinstall(void *param);
 static void	linux_set_syscall_retval(struct thread *td, int error);
-static int	linux_fetch_syscall_args(struct thread *td, struct syscall_args *sa);
+static int	linux_fetch_syscall_args(struct thread *td);
 static void	linux_exec_setregs(struct thread *td, struct image_params *imgp,
 		    u_long stack);
 static int	linux_vsyscall(struct thread *td);
@@ -217,13 +217,15 @@ translate_traps(int signal, int trap_code)
 }
 
 static int
-linux_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+linux_fetch_syscall_args(struct thread *td)
 {
 	struct proc *p;
 	struct trapframe *frame;
+	struct syscall_args *sa;
 
 	p = td->td_proc;
 	frame = td->td_frame;
+	sa = &td->td_sa;
 
 	sa->args[0] = frame->tf_rdi;
 	sa->args[1] = frame->tf_rsi;
diff --git a/sys/amd64/linux32/linux32_sysvec.c b/sys/amd64/linux32/linux32_sysvec.c
index c264f3ab0e3c..ea849ba3d847 100644
--- a/sys/amd64/linux32/linux32_sysvec.c
+++ b/sys/amd64/linux32/linux32_sysvec.c
@@ -725,13 +725,15 @@ linux_rt_sigreturn(struct thread *td, struct linux_rt_sigreturn_args *args)
 }
 
 static int
-linux32_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+linux32_fetch_syscall_args(struct thread *td)
 {
 	struct proc *p;
 	struct trapframe *frame;
+	struct syscall_args *sa;
 
 	p = td->td_proc;
 	frame = td->td_frame;
+	sa = &td->td_sa;
 
 	sa->args[0] = frame->tf_rbx;
 	sa->args[1] = frame->tf_rcx;
diff --git a/sys/arm/arm/syscall.c b/sys/arm/arm/syscall.c
index 1ff48abd22e8..8c33fff30a19 100644
--- a/sys/arm/arm/syscall.c
+++ b/sys/arm/arm/syscall.c
@@ -99,12 +99,14 @@ __FBSDID("$FreeBSD$");
 void swi_handler(struct trapframe *);
 
 int
-cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+cpu_fetch_syscall_args(struct thread *td)
 {
 	struct proc *p;
 	register_t *ap;
+	struct syscall_args *sa;
 	int error;
 
+	sa = &td->td_sa;
 	sa->code = td->td_frame->tf_r7;
 	ap = &td->td_frame->tf_r0;
 	if (sa->code == SYS_syscall) {
@@ -141,15 +143,14 @@ cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
 static void
 syscall(struct thread *td, struct trapframe *frame)
 {
-	struct syscall_args sa;
 	int error;
 
-	sa.nap = 4;
+	td->td_sa.nap = 4;
 
-	error = syscallenter(td, &sa);
+	error = syscallenter(td);
 	KASSERT(error != 0 || td->td_ar == NULL,
 	    ("returning from syscall with td_ar set!"));
-	syscallret(td, error, &sa);
+	syscallret(td, error);
 }
 
 void
diff --git a/sys/arm/cloudabi32/cloudabi32_sysvec.c b/sys/arm/cloudabi32/cloudabi32_sysvec.c
index 100fa479acda..a0bebcc99641 100644
--- a/sys/arm/cloudabi32/cloudabi32_sysvec.c
+++ b/sys/arm/cloudabi32/cloudabi32_sysvec.c
@@ -67,11 +67,15 @@ cloudabi32_proc_setregs(struct thread *td, struct image_params *imgp,
 }
 
 static int
-cloudabi32_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+cloudabi32_fetch_syscall_args(struct thread *td)
 {
-	struct trapframe *frame = td->td_frame;
+	struct trapframe *frame;
+	struct syscall_args *sa;
 	int error;
 
+	frame = td->td_frame;
+	sa = &td->td_sa;
+
 	/* Obtain system call number. */
 	sa->code = frame->tf_r12;
 	if (sa->code >= CLOUDABI32_SYS_MAXSYSCALL)
diff --git a/sys/arm64/arm64/trap.c b/sys/arm64/arm64/trap.c
index d425fb99ca9d..47971af04aac 100644
--- a/sys/arm64/arm64/trap.c
+++ b/sys/arm64/arm64/trap.c
@@ -92,15 +92,17 @@ call_trapsignal(struct thread *td, int sig, int code, void *addr)
 }
 
 int
-cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+cpu_fetch_syscall_args(struct thread *td)
 {
 	struct proc *p;
 	register_t *ap;
+	struct syscall_args *sa;
 	int nap;
 
 	nap = 8;
 	p = td->td_proc;
 	ap = td->td_frame->tf_x;
+	sa = &td->td_sa;
 
 	sa->code = td->td_frame->tf_x[8];
 
@@ -132,12 +134,11 @@ cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
 static void
 svc_handler(struct thread *td, struct trapframe *frame)
 {
-	struct syscall_args sa;
 	int error;
 
 	if ((frame->tf_esr & ESR_ELx_ISS_MASK) == 0) {
-		error = syscallenter(td, &sa);
-		syscallret(td, error, &sa);
+		error = syscallenter(td);
+		syscallret(td, error);
 	} else {
 		call_trapsignal(td, SIGILL, ILL_ILLOPN, (void *)frame->tf_elr);
 		userret(td, frame);
diff --git a/sys/arm64/cloudabi64/cloudabi64_sysvec.c b/sys/arm64/cloudabi64/cloudabi64_sysvec.c
index fbad0ba70db7..f6e75f563668 100644
--- a/sys/arm64/cloudabi64/cloudabi64_sysvec.c
+++ b/sys/arm64/cloudabi64/cloudabi64_sysvec.c
@@ -67,11 +67,15 @@ cloudabi64_proc_setregs(struct thread *td, struct image_params *imgp,
 }
 
 static int
-cloudabi64_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+cloudabi64_fetch_syscall_args(struct thread *td)
 {
-	struct trapframe *frame = td->td_frame;
+	struct trapframe *frame;
+	struct syscall_args *sa;
 	int i;
 
+	frame = td->td_frame;
+	sa = &td->td_sa;
+
 	/* Obtain system call number. */
 	sa->code = frame->tf_x[8];
 	if (sa->code >= CLOUDABI64_SYS_MAXSYSCALL)
diff --git a/sys/compat/ia32/ia32_util.h b/sys/compat/ia32/ia32_util.h
index 6b5f9a11de49..41aad4e8cac1 100644
--- a/sys/compat/ia32/ia32_util.h
+++ b/sys/compat/ia32/ia32_util.h
@@ -50,7 +50,7 @@
 #define	IA32_MAXVMEM	0			/* Unlimited */
 
 struct syscall_args;
-int ia32_fetch_syscall_args(struct thread *td, struct syscall_args *sa);
+int ia32_fetch_syscall_args(struct thread *td);
 void ia32_set_syscall_retval(struct thread *, int);
 void ia32_fixlimit(struct rlimit *rl, int which);
 
diff --git a/sys/i386/cloudabi32/cloudabi32_sysvec.c b/sys/i386/cloudabi32/cloudabi32_sysvec.c
index c2a21fa90461..e50a19c5be87 100644
--- a/sys/i386/cloudabi32/cloudabi32_sysvec.c
+++ b/sys/i386/cloudabi32/cloudabi32_sysvec.c
@@ -85,11 +85,15 @@ cloudabi32_proc_setregs(struct thread *td, struct image_params *imgp,
 }
 
 static int
-cloudabi32_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+cloudabi32_fetch_syscall_args(struct thread *td)
 {
-	struct trapframe *frame = td->td_frame;
+	struct trapframe *frame;
+	struct syscall_args *sa;
 	int error;
 
+	frame = td->td_frame;
+	sa = &td->td_sa;
+
 	/* Obtain system call number. */
 	sa->code = frame->tf_eax;
 	if (sa->code >= CLOUDABI32_SYS_MAXSYSCALL)
diff --git a/sys/i386/i386/trap.c b/sys/i386/i386/trap.c
index ef0a61c13382..3ad3ff997c67 100644
--- a/sys/i386/i386/trap.c
+++ b/sys/i386/i386/trap.c
@@ -1012,16 +1012,18 @@ dblfault_handler()
 }
 
 int
-cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+cpu_fetch_syscall_args(struct thread *td)
 {
 	struct proc *p;
 	struct trapframe *frame;
+	struct syscall_args *sa;
 	caddr_t params;
 	long tmp;
 	int error;
 
 	p = td->td_proc;
 	frame = td->td_frame;
+	sa = &td->td_sa;
 
 	params = (caddr_t)frame->tf_esp + sizeof(int);
 	sa->code = frame->tf_eax;
@@ -1082,7 +1084,6 @@ void
 syscall(struct trapframe *frame)
 {
 	struct thread *td;
-	struct syscall_args sa;
 	register_t orig_tf_eflags;
 	int error;
 	ksiginfo_t ksi;
@@ -1099,7 +1100,7 @@ syscall(struct trapframe *frame)
 	td = curthread;
 	td->td_frame = frame;
 
-	error = syscallenter(td, &sa);
+	error = syscallenter(td);
 
 	/*
 	 * Traced syscall.
@@ -1115,10 +1116,10 @@ syscall(struct trapframe *frame)
 
 	KASSERT(PCB_USER_FPU(td->td_pcb),
 	    ("System call %s returning with kernel FPU ctx leaked",
-	     syscallname(td->td_proc, sa.code)));
+	     syscallname(td->td_proc, td->td_sa.code)));
 	KASSERT(td->td_pcb->pcb_save == get_pcb_user_save_td(td),
 	    ("System call %s returning with mangled pcb_save",
-	     syscallname(td->td_proc, sa.code)));
+	     syscallname(td->td_proc, td->td_sa.code)));
 
-	syscallret(td, error, &sa);
+	syscallret(td, error);
 }
diff --git a/sys/i386/linux/linux_sysvec.c b/sys/i386/linux/linux_sysvec.c
index 49fafdc17fe0..a4919a02acef 100644
--- a/sys/i386/linux/linux_sysvec.c
+++ b/sys/i386/linux/linux_sysvec.c
@@ -850,13 +850,15 @@ linux_rt_sigreturn(struct thread *td, struct linux_rt_sigreturn_args *args)
 }
 
 static int
-linux_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+linux_fetch_syscall_args(struct thread *td)
 {
 	struct proc *p;
 	struct trapframe *frame;
+	struct syscall_args *sa;
 
 	p = td->td_proc;
 	frame = td->td_frame;
+	sa = &td->td_sa;
 
 	sa->code = frame->tf_eax;
 	sa->args[0] = frame->tf_ebx;
diff --git a/sys/kern/init_main.c b/sys/kern/init_main.c
index 4c0e4960b401..f71ba6efaf55 100644
--- a/sys/kern/init_main.c
+++ b/sys/kern/init_main.c
@@ -360,8 +360,7 @@ SYSINIT(diagwarn2, SI_SUB_LAST, SI_ORDER_THIRD + 2,
 #endif
 
 static int
-null_fetch_syscall_args(struct thread *td __unused,
-    struct syscall_args *sa __unused)
+null_fetch_syscall_args(struct thread *td __unused)
 {
 
 	panic("null_fetch_syscall_args");
diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index 5931df8ba2d6..5fafc6b81671 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -1099,7 +1099,7 @@ fork_return(struct thread *td, struct trapframe *frame)
 		 */
 		PROC_LOCK(p);
 		td->td_dbgflags |= TDB_SCX;
-		_STOPEVENT(p, S_SCX, td->td_dbg_sc_code);
+		_STOPEVENT(p, S_SCX, td->td_sa.code);
 		if ((p->p_ptevents & PTRACE_SCX) != 0 ||
 		    (td->td_dbgflags & TDB_BORN) != 0)
 			ptracestop(td, SIGTRAP, NULL);
diff --git a/sys/kern/kern_thread.c b/sys/kern/kern_thread.c
index b894245dae0d..d3e7e306a684 100644
--- a/sys/kern/kern_thread.c
+++ b/sys/kern/kern_thread.c
@@ -80,9 +80,9 @@ _Static_assert(offsetof(struct thread, td_flags) == 0xf4,
     "struct thread KBI td_flags");
 _Static_assert(offsetof(struct thread, td_pflags) == 0xfc,
     "struct thread KBI td_pflags");
-_Static_assert(offsetof(struct thread, td_frame) == 0x410,
+_Static_assert(offsetof(struct thread, td_frame) == 0x460,
     "struct thread KBI td_frame");
-_Static_assert(offsetof(struct thread, td_emuldata) == 0x4b8,
+_Static_assert(offsetof(struct thread, td_emuldata) == 0x508,
     "struct thread KBI td_emuldata");
 _Static_assert(offsetof(struct proc, p_flag) == 0xb0,
     "struct proc KBI p_flag");
@@ -100,9 +100,9 @@ _Static_assert(offsetof(struct thread, td_flags) == 0x9c,
     "struct thread KBI td_flags");
 _Static_assert(offsetof(struct thread, td_pflags) == 0xa4,
     "struct thread KBI td_pflags");
-_Static_assert(offsetof(struct thread, td_frame) == 0x2c8,
+_Static_assert(offsetof(struct thread, td_frame) == 0x2ec,
     "struct thread KBI td_frame");
-_Static_assert(offsetof(struct thread, td_emuldata) == 0x314,
+_Static_assert(offsetof(struct thread, td_emuldata) == 0x338,
     "struct thread KBI td_emuldata");
 _Static_assert(offsetof(struct proc, p_flag) == 0x68,
     "struct proc KBI p_flag");
diff --git a/sys/kern/subr_syscall.c b/sys/kern/subr_syscall.c
index 3c0a9323677b..6a5dc3f601ae 100644
--- a/sys/kern/subr_syscall.c
+++ b/sys/kern/subr_syscall.c
@@ -53,13 +53,15 @@ __FBSDID("$FreeBSD$");
 #include <security/audit/audit.h>
 
 static inline int
-syscallenter(struct thread *td, struct syscall_args *sa)
+syscallenter(struct thread *td)
 {
 	struct proc *p;
+	struct syscall_args *sa;
 	int error, traced;
 
 	VM_CNT_INC(v_syscall);
 	p = td->td_proc;
+	sa = &td->td_sa;
 
 	td->td_pticks = 0;
 	if (td->td_cowgen != p->p_cowgen)
@@ -72,7 +74,7 @@ syscallenter(struct thread *td, struct syscall_args *sa)
 			td->td_dbgflags |= TDB_SCE;
 		PROC_UNLOCK(p);
 	}
-	error = (p->p_sysent->sv_fetch_syscall_args)(td, sa);
+	error = (p->p_sysent->sv_fetch_syscall_args)(td);
 #ifdef KTRACE
 	if (KTRPOINT(td, KTR_SYSCALL))
 		ktrsyscall(sa->code, sa->narg, sa->args);
@@ -86,8 +88,6 @@ syscallenter(struct thread *td, struct syscall_args *sa)
 		STOPEVENT(p, S_SCE, sa->narg);
 		if (p->p_flag & P_TRACED) {
 			PROC_LOCK(p);
-			td->td_dbg_sc_code = sa->code;
-			td->td_dbg_sc_narg = sa->narg;
 			if (p->p_ptevents & PTRACE_SCE)
 				ptracestop((td), SIGTRAP, NULL);
 			PROC_UNLOCK(p);
@@ -97,11 +97,7 @@ syscallenter(struct thread *td, struct syscall_args *sa)
 			 * Reread syscall number and arguments if
 			 * debugger modified registers or memory.
 			 */
-			error = (p->p_sysent->sv_fetch_syscall_args)(td, sa);
-			PROC_LOCK(p);
-			td->td_dbg_sc_code = sa->code;
-			td->td_dbg_sc_narg = sa->narg;
-			PROC_UNLOCK(p);
+			error = (p->p_sysent->sv_fetch_syscall_args)(td);
 #ifdef KTRACE
 			if (KTRPOINT(td, KTR_SYSCALL))
 				ktrsyscall(sa->code, sa->narg, sa->args);
@@ -163,9 +159,10 @@ syscallenter(struct thread *td, struct syscall_args *sa)
 }
 
 static inline void
-syscallret(struct thread *td, int error, struct syscall_args *sa)
+syscallret(struct thread *td, int error)
 {
 	struct proc *p, *p2;
+	struct syscall_args *sa;
 	ksiginfo_t ksi;
 	int traced, error1;
 
@@ -173,6 +170,7 @@ syscallret(struct thread *td, int error, struct syscall_args *sa)
 	    ("fork() did not clear TDP_FORKING upon completion"));
 
 	p = td->td_proc;
+	sa = &td->td_sa;
 	if ((trap_enotcap || (p->p_flag2 & P2_TRAPCAP) != 0) &&
 	    IN_CAPABILITY_MODE(td)) {
 		error1 = (td->td_pflags & TDP_NERRNO) == 0 ? error :
diff --git a/sys/kern/sys_process.c b/sys/kern/sys_process.c
index 7bb167a14ef2..e18b7e6a2971 100644
--- a/sys/kern/sys_process.c
+++ b/sys/kern/sys_process.c
@@ -1347,8 +1347,8 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
 		pl->pl_siglist = td2->td_siglist;
 		strcpy(pl->pl_tdname, td2->td_name);
 		if ((td2->td_dbgflags & (TDB_SCE | TDB_SCX)) != 0) {
-			pl->pl_syscall_code = td2->td_dbg_sc_code;
-			pl->pl_syscall_narg = td2->td_dbg_sc_narg;
+			pl->pl_syscall_code = td2->td_sa.code;
+			pl->pl_syscall_narg = td2->td_sa.narg;
 		} else {
 			pl->pl_syscall_code = 0;
 			pl->pl_syscall_narg = 0;
diff --git a/sys/mips/mips/trap.c b/sys/mips/mips/trap.c
index 77b05801364b..0f1508c7f2d3 100644
--- a/sys/mips/mips/trap.c
+++ b/sys/mips/mips/trap.c
@@ -334,12 +334,16 @@ static int emulate_unaligned_access(struct trapframe *frame, int mode);
 extern void fswintrberr(void); /* XXX */
 
 int
-cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+cpu_fetch_syscall_args(struct thread *td)
 {
-	struct trapframe *locr0 = td->td_frame;
+	struct trapframe *locr0;
 	struct sysentvec *se;
+	struct syscall_args *sa;
 	int error, nsaved;
 
+	locr0 = td->td_frame;
+	sa = &td->td_sa;
+	
 	bzero(sa->args, sizeof(sa->args));
 
 	/* compute next PC after syscall instruction */
@@ -785,19 +789,18 @@ dofault:
 
 	case T_SYSCALL + T_USER:
 		{
-			struct syscall_args sa;
 			int error;
 
-			sa.trapframe = trapframe;
-			error = syscallenter(td, &sa);
+			td->td_sa.trapframe = trapframe;
+			error = syscallenter(td);
 
 #if !defined(SMP) && (defined(DDB) || defined(DEBUG))
 			if (trp == trapdebug)
-				trapdebug[TRAPSIZE - 1].code = sa.code;
+				trapdebug[TRAPSIZE - 1].code = td->td_sa.code;
 			else
-				trp[-1].code = sa.code;
+				trp[-1].code = td->td_sa.code;
 #endif
-			trapdebug_enter(td->td_frame, -sa.code);
+			trapdebug_enter(td->td_frame, -td->td_sa.code);
 
 			/*
 			 * The sync'ing of I & D caches for SYS_ptrace() is
@@ -805,7 +808,7 @@ dofault:
 			 * instead of being done here under a special check
 			 * for SYS_ptrace().
 			 */
-			syscallret(td, error, &sa);
+			syscallret(td, error);
 			return (trapframe->pc);
 		}
 
diff --git a/sys/powerpc/powerpc/trap.c b/sys/powerpc/powerpc/trap.c
index 526042580eab..473011429433 100644
--- a/sys/powerpc/powerpc/trap.c
+++ b/sys/powerpc/powerpc/trap.c
@@ -496,16 +496,18 @@ handle_onfault(struct trapframe *frame)
 }
 
 int
-cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+cpu_fetch_syscall_args(struct thread *td)
 {
 	struct proc *p;
 	struct trapframe *frame;
+	struct syscall_args *sa;
 	caddr_t	params;
 	size_t argsz;
 	int error, n, i;
 
 	p = td->td_proc;
 	frame = td->td_frame;
+	sa = &td->td_sa;
 
 	sa->code = frame->fixreg[0];
 	params = (caddr_t)(frame->fixreg + FIRSTARG);
@@ -587,7 +589,6 @@ void
 syscall(struct trapframe *frame)
 {
 	struct thread *td;
-	struct syscall_args sa;
 	int error;
 
 	td = curthread;
@@ -602,8 +603,8 @@ syscall(struct trapframe *frame)
             "r"(td->td_pcb->pcb_cpu.aim.usr_vsid), "r"(USER_SLB_SLBE));
 #endif
 
-	error = syscallenter(td, &sa);
-	syscallret(td, error, &sa);
+	error = syscallenter(td);
+	syscallret(td, error);
 }
 
 #if defined(__powerpc64__) && defined(AIM)
diff --git a/sys/riscv/riscv/trap.c b/sys/riscv/riscv/trap.c
index b6e5da5e7c61..5af0c014e3dc 100644
--- a/sys/riscv/riscv/trap.c
+++ b/sys/riscv/riscv/trap.c
@@ -89,14 +89,16 @@ call_trapsignal(struct thread *td, int sig, int code, void *addr)
 }
 
 int
-cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+cpu_fetch_syscall_args(struct thread *td)
 {
 	struct proc *p;
 	register_t *ap;
+	struct syscall_args *sa;
 	int nap;
 
 	nap = NARGREG;
 	p = td->td_proc;
+	sa = &td->td_sa;
 	ap = &td->td_frame->tf_a[0];
 
 	sa->code = td->td_frame->tf_t[0];
@@ -151,15 +153,14 @@ dump_regs(struct trapframe *frame)
 static void
 svc_handler(struct trapframe *frame)
 {
-	struct syscall_args sa;
 	struct thread *td;
 	int error;
 
 	td = curthread;
 	td->td_frame = frame;
 
-	error = syscallenter(td, &sa);
-	syscallret(td, error, &sa);
+	error = syscallenter(td);
+	syscallret(td, error);
 }
 
 static void
diff --git a/sys/sparc64/sparc64/trap.c b/sys/sparc64/sparc64/trap.c
index d2281b11e133..095a7a991a07 100644
--- a/sys/sparc64/sparc64/trap.c
+++ b/sys/sparc64/sparc64/trap.c
@@ -538,17 +538,19 @@ trap_pfault(struct thread *td, struct trapframe *tf)
 #define	REG_MAXARGS	6
 
 int
-cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+cpu_fetch_syscall_args(struct thread *td)
 {
 	struct trapframe *tf;
 	struct proc *p;
 	register_t *argp;
+	struct syscall_args *sa;
 	int reg;
 	int regcnt;
 	int error;
 
 	p = td->td_proc;
 	tf = td->td_frame;
+	sa = &td->td_sa;
 	reg = 0;
 	regcnt = REG_MAXARGS;
 
@@ -596,7 +598,6 @@ void
 syscall(struct trapframe *tf)
 {
 	struct thread *td;
-	struct syscall_args sa;
 	int error;
 
 	td = curthread;
@@ -612,6 +613,6 @@ syscall(struct trapframe *tf)
 	td->td_pcb->pcb_tpc = tf->tf_tpc;
 	TF_DONE(tf);
 
-	error = syscallenter(td, &sa);
-	syscallret(td, error, &sa);
+	error = syscallenter(td);
+	syscallret(td, error);
 }
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index 2ecbe4585356..2daf1a6aee7d 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -142,6 +142,7 @@ struct pargs {
  *      j - locked by proc slock
  *      k - only accessed by curthread
  *	k*- only accessed by curthread and from an interrupt
+ *	kx- only accessed by curthread and by debugger
  *      l - the attaching proc or attaching proc parent
  *      m - Giant
  *      n - not locked, lazy
@@ -296,11 +297,11 @@ struct thread {
 	u_char		td_pri_class;	/* (t) Scheduling class. */
 	u_char		td_user_pri;	/* (t) User pri from estcpu and nice. */
 	u_char		td_base_user_pri; /* (t) Base user pri */
-	u_int		td_dbg_sc_code;	/* (c) Syscall code to debugger. */
-	u_int		td_dbg_sc_narg;	/* (c) Syscall arg count to debugger.*/
 	uintptr_t	td_rb_list;	/* (k) Robust list head. */
 	uintptr_t	td_rbp_list;	/* (k) Robust priv list head. */
 	uintptr_t	td_rb_inact;	/* (k) Current in-action mutex loc. */
+	struct syscall_args td_sa;	/* (kx) Syscall parameters. Copied on
+					   fork for child tracing. */
 #define	td_endcopy td_pcb
 
 /*
@@ -1053,7 +1054,7 @@ void	userret(struct thread *, struct trapframe *);
 void	cpu_exit(struct thread *);
 void	exit1(struct thread *, int, int) __dead2;
 void	cpu_copy_thread(struct thread *td, struct thread *td0);
-int	cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa);
+int	cpu_fetch_syscall_args(struct thread *td);
 void	cpu_fork(struct thread *, struct proc *, struct thread *, int);
 void	cpu_fork_kthread_handler(struct thread *, void (*)(void *), void *);
 void	cpu_set_syscall_retval(struct thread *, int);
diff --git a/sys/sys/sysent.h b/sys/sys/sysent.h
index 643717603fdd..29540949ce24 100644
--- a/sys/sys/sysent.h
+++ b/sys/sys/sysent.h
@@ -119,8 +119,7 @@ struct sysentvec {
 	u_long		*sv_maxssiz;
 	u_int		sv_flags;
 	void		(*sv_set_syscall_retval)(struct thread *, int);
-	int		(*sv_fetch_syscall_args)(struct thread *, struct
-			    syscall_args *);
+	int		(*sv_fetch_syscall_args)(struct thread *);
 	const char	**sv_syscallnames;
 	vm_offset_t	sv_timekeep_base;
 	vm_offset_t	sv_shared_page_base;