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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Mon, 12 Jun 2017 21:03:23 +0000 (UTC)
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Subject: svn commit: r319873 - in head/sys: amd64/amd64 amd64/cloudabi32
 amd64/cloudabi64 amd64/ia32 amd64/linux amd64/linux32 arm/arm arm/cloudabi32
 arm64/arm64 arm64/cloudabi64 compat/ia32 i386/cloudabi32...
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Author: kib
Date: Mon Jun 12 21:03:23 2017
New Revision: 319873
URL: https://svnweb.freebsd.org/changeset/base/319873

Log:
  Move struct syscall_args syscall arguments parameters container into
  struct thread.
  
  For all architectures, the syscall trap handlers have to allocate the
  structure on the stack.  The structure takes 88 bytes on 64bit arches
  which is not negligible.  Also, it cannot be easily found by other
  code, which e.g. caused duplication of some members of the structure
  to struct thread already.  The change removes td_dbg_sc_code and
  td_dbg_sc_nargs which were directly copied from syscall_args.
  
  The structure is put into the copied on fork part of the struct thread
  to make the syscall arguments information correct in the child after
  fork.
  
  This move will also allow several more uses shortly.
  
  Reviewed by:	jhb (previous version)
  Sponsored by:	The FreeBSD Foundation
  MFC after:	3 weeks
  X-Differential revision:	https://reviews.freebsd.org/D11080

Modified:
  head/sys/amd64/amd64/trap.c
  head/sys/amd64/cloudabi32/cloudabi32_sysvec.c
  head/sys/amd64/cloudabi64/cloudabi64_sysvec.c
  head/sys/amd64/ia32/ia32_syscall.c
  head/sys/amd64/linux/linux_sysvec.c
  head/sys/amd64/linux32/linux32_sysvec.c
  head/sys/arm/arm/syscall.c
  head/sys/arm/cloudabi32/cloudabi32_sysvec.c
  head/sys/arm64/arm64/trap.c
  head/sys/arm64/cloudabi64/cloudabi64_sysvec.c
  head/sys/compat/ia32/ia32_util.h
  head/sys/i386/cloudabi32/cloudabi32_sysvec.c
  head/sys/i386/i386/trap.c
  head/sys/i386/linux/linux_sysvec.c
  head/sys/kern/init_main.c
  head/sys/kern/kern_fork.c
  head/sys/kern/kern_thread.c
  head/sys/kern/subr_syscall.c
  head/sys/kern/sys_process.c
  head/sys/mips/mips/trap.c
  head/sys/powerpc/powerpc/trap.c
  head/sys/riscv/riscv/trap.c
  head/sys/sparc64/sparc64/trap.c
  head/sys/sys/proc.h
  head/sys/sys/sysent.h

Modified: head/sys/amd64/amd64/trap.c
==============================================================================
--- head/sys/amd64/amd64/trap.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/amd64/amd64/trap.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -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 sysca
 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

Modified: head/sys/amd64/cloudabi32/cloudabi32_sysvec.c
==============================================================================
--- head/sys/amd64/cloudabi32/cloudabi32_sysvec.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/amd64/cloudabi32/cloudabi32_sysvec.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -90,10 +90,14 @@ cloudabi32_proc_setregs(struct thread *td, struct imag
 }
 
 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;

Modified: head/sys/amd64/cloudabi64/cloudabi64_sysvec.c
==============================================================================
--- head/sys/amd64/cloudabi64/cloudabi64_sysvec.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/amd64/cloudabi64/cloudabi64_sysvec.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -87,9 +87,13 @@ cloudabi64_proc_setregs(struct thread *td, struct imag
 }
 
 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;

Modified: head/sys/amd64/ia32/ia32_syscall.c
==============================================================================
--- head/sys/amd64/ia32/ia32_syscall.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/amd64/ia32/ia32_syscall.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -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

Modified: head/sys/amd64/linux/linux_sysvec.c
==============================================================================
--- head/sys/amd64/linux/linux_sysvec.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/amd64/linux/linux_sysvec.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -126,7 +126,7 @@ static boolean_t linux_trans_osrel(const Elf_Note *not
 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;

Modified: head/sys/amd64/linux32/linux32_sysvec.c
==============================================================================
--- head/sys/amd64/linux32/linux32_sysvec.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/amd64/linux32/linux32_sysvec.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -725,13 +725,15 @@ linux_rt_sigreturn(struct thread *td, struct linux_rt_
 }
 
 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;

Modified: head/sys/arm/arm/syscall.c
==============================================================================
--- head/sys/arm/arm/syscall.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/arm/arm/syscall.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -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 sysca
 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

Modified: head/sys/arm/cloudabi32/cloudabi32_sysvec.c
==============================================================================
--- head/sys/arm/cloudabi32/cloudabi32_sysvec.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/arm/cloudabi32/cloudabi32_sysvec.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -67,10 +67,14 @@ cloudabi32_proc_setregs(struct thread *td, struct imag
 }
 
 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;

Modified: head/sys/arm64/arm64/trap.c
==============================================================================
--- head/sys/arm64/arm64/trap.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/arm64/arm64/trap.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -92,15 +92,17 @@ call_trapsignal(struct thread *td, int sig, int code, 
 }
 
 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 sysca
 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);

Modified: head/sys/arm64/cloudabi64/cloudabi64_sysvec.c
==============================================================================
--- head/sys/arm64/cloudabi64/cloudabi64_sysvec.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/arm64/cloudabi64/cloudabi64_sysvec.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -67,10 +67,14 @@ cloudabi64_proc_setregs(struct thread *td, struct imag
 }
 
 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];

Modified: head/sys/compat/ia32/ia32_util.h
==============================================================================
--- head/sys/compat/ia32/ia32_util.h	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/compat/ia32/ia32_util.h	Mon Jun 12 21:03:23 2017	(r319873)
@@ -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);
 

Modified: head/sys/i386/cloudabi32/cloudabi32_sysvec.c
==============================================================================
--- head/sys/i386/cloudabi32/cloudabi32_sysvec.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/i386/cloudabi32/cloudabi32_sysvec.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -85,10 +85,14 @@ cloudabi32_proc_setregs(struct thread *td, struct imag
 }
 
 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;

Modified: head/sys/i386/i386/trap.c
==============================================================================
--- head/sys/i386/i386/trap.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/i386/i386/trap.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -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);
 }

Modified: head/sys/i386/linux/linux_sysvec.c
==============================================================================
--- head/sys/i386/linux/linux_sysvec.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/i386/linux/linux_sysvec.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -850,13 +850,15 @@ linux_rt_sigreturn(struct thread *td, struct linux_rt_
 }
 
 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;

Modified: head/sys/kern/init_main.c
==============================================================================
--- head/sys/kern/init_main.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/kern/init_main.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -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");

Modified: head/sys/kern/kern_fork.c
==============================================================================
--- head/sys/kern/kern_fork.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/kern/kern_fork.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -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);

Modified: head/sys/kern/kern_thread.c
==============================================================================
--- head/sys/kern/kern_thread.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/kern/kern_thread.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -80,9 +80,9 @@ _Static_assert(offsetof(struct thread, td_flags) == 0x
     "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) == 0x
     "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");

Modified: head/sys/kern/subr_syscall.c
==============================================================================
--- head/sys/kern/subr_syscall.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/kern/subr_syscall.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -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 *s
 			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 *s
 		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 *s
 			 * 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 *s
 }
 
 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 syscal
 	    ("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 :

Modified: head/sys/kern/sys_process.c
==============================================================================
--- head/sys/kern/sys_process.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/kern/sys_process.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -1347,8 +1347,8 @@ kern_ptrace(struct thread *td, int req, pid_t pid, voi
 		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;

Modified: head/sys/mips/mips/trap.c
==============================================================================
--- head/sys/mips/mips/trap.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/mips/mips/trap.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -334,12 +334,16 @@ static int emulate_unaligned_access(struct trapframe *
 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);
 		}
 

Modified: head/sys/powerpc/powerpc/trap.c
==============================================================================
--- head/sys/powerpc/powerpc/trap.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/powerpc/powerpc/trap.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -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)

Modified: head/sys/riscv/riscv/trap.c
==============================================================================
--- head/sys/riscv/riscv/trap.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/riscv/riscv/trap.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -89,14 +89,16 @@ call_trapsignal(struct thread *td, int sig, int code, 
 }
 
 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

Modified: head/sys/sparc64/sparc64/trap.c
==============================================================================
--- head/sys/sparc64/sparc64/trap.c	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/sparc64/sparc64/trap.c	Mon Jun 12 21:03:23 2017	(r319873)
@@ -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);
 }

Modified: head/sys/sys/proc.h
==============================================================================
--- head/sys/sys/proc.h	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/sys/proc.h	Mon Jun 12 21:03:23 2017	(r319873)
@@ -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);

Modified: head/sys/sys/sysent.h
==============================================================================
--- head/sys/sys/sysent.h	Mon Jun 12 20:55:20 2017	(r319872)
+++ head/sys/sys/sysent.h	Mon Jun 12 21:03:23 2017	(r319873)
@@ -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;