Index: sys/amd64/linux/linux_ptrace.c
===================================================================
--- sys/amd64/linux/linux_ptrace.c
+++ sys/amd64/linux/linux_ptrace.c
@@ -94,6 +94,12 @@
     LINUX_PTRACE_O_TRACESECCOMP | LINUX_PTRACE_O_EXITKILL |	\
     LINUX_PTRACE_O_SUSPEND_SECCOMP)
 
+#define	LINUX_PTRACE_SYSCALL_INFO_NONE	0
+#define	LINUX_PTRACE_SYSCALL_INFO_ENTRY	1
+#define	LINUX_PTRACE_SYSCALL_INFO_EXIT	2
+
+#define	LINUX_ARCH_AMD64		0xc000003e
+
 static int
 map_signum(int lsig, int *bsigp)
 {
@@ -203,6 +209,28 @@
 	l_ulong gs;
 };
 
+struct syscall_info {
+	uint8_t op;
+	uint32_t arch;
+	uint64_t instruction_pointer;
+	uint64_t stack_pointer;
+	union {
+		struct {
+			uint64_t nr;
+			uint64_t args[6];
+		} entry;
+		struct {
+			int64_t rval;
+			uint8_t is_error;
+		} exit;
+		struct {
+			uint64_t nr;
+			uint64_t args[6];
+			uint32_t ret_data;
+		} seccomp;
+	};
+};
+
 /*
  * Translate amd64 ptrace registers between Linux and FreeBSD formats.
  * The translation is pretty straighforward, for all registers but
@@ -560,9 +588,67 @@
 static int
 linux_ptrace_get_syscall_info(struct thread *td, pid_t pid, l_ulong addr, l_ulong data)
 {
+	struct ptrace_lwpinfo lwpinfo;
+	struct ptrace_sc_ret sr;
+	struct reg b_reg;
+	struct syscall_info si;
+	int error;
 
-	linux_msg(td, "PTRACE_GET_SYSCALL_INFO not implemented; returning EINVAL");
-	return (EINVAL);
+	error = kern_ptrace(td, PT_GETREGS, pid, &b_reg, 0);
+	if (error != 0)
+		return (error);
+
+	error = kern_ptrace(td, PT_LWPINFO, pid, &lwpinfo, sizeof(lwpinfo));
+	if (error != 0) {
+		linux_msg(td, "PT_LWPINFO failed with error %d", error);
+		return (error);
+	}
+
+	memset(&si, 0, sizeof(si));
+
+	if (lwpinfo.pl_flags & PL_FLAG_SCE) {
+		si.op = LINUX_PTRACE_SYSCALL_INFO_ENTRY;
+		si.entry.nr = lwpinfo.pl_syscall_code;
+
+		error = kern_ptrace(td, PT_GET_SC_ARGS, pid, &si.entry.args, sizeof(si.entry.args));
+		if (error != 0) {
+			linux_msg(td, "PT_GET_SC_ARGS failed with error %d", error);
+			return (error);
+		}
+	} else if (lwpinfo.pl_flags & PL_FLAG_SCX) {
+		si.op = LINUX_PTRACE_SYSCALL_INFO_EXIT;
+		error = kern_ptrace(td, PT_GET_SC_RET, pid, &sr, sizeof(sr));
+
+		if (error != 0) {
+			linux_msg(td, "PT_GET_SC_RET failed with error %d", error);
+			return (error);
+		}
+		linux_msg(td, "sr_error %d, sr_retval[0] %#lx, sr_retval[1] %#lx", sr.sr_error, (long)sr.sr_retval[0], (long)sr.sr_retval[1]);
+
+		if (sr.sr_error == 0) {
+			si.exit.rval = sr.sr_retval[0];
+			si.exit.is_error = 0;
+		} else if (sr.sr_error > 0) {
+			si.exit.rval = bsd_to_linux_errno(sr.sr_error);
+			si.exit.is_error = 1;
+		} else {
+			/* XXX: Not sure what to do here. */
+			si.exit.rval = sr.sr_retval[0];
+			si.exit.is_error = 0;
+		}
+	} else {
+		si.op = LINUX_PTRACE_SYSCALL_INFO_NONE;
+	}
+
+	si.arch = LINUX_ARCH_AMD64;
+	si.instruction_pointer = b_reg.r_rip;
+	si.stack_pointer = b_reg.r_rsp;
+
+	error = copyout(&si, (void *)data, sizeof(si));
+	if (error == 0)
+		td->td_retval[0] = sizeof(si);
+
+	return (error);
 }
 
 int
Index: sys/kern/sys_process.c
===================================================================
--- sys/kern/sys_process.c
+++ sys/kern/sys_process.c
@@ -924,9 +924,7 @@
 			error = EINVAL;
 			break;
 		}
-		bzero(addr, sizeof(td2->td_sa.args));
-		bcopy(td2->td_sa.args, addr, td2->td_sa.callp->sy_narg *
-		    sizeof(register_t));
+		bcopy(td2->td_sa.args, addr, sizeof(td2->td_sa.args));
 		break;
 
 	case PT_GET_SC_RET: