diff --git a/plan9/mksyscall.go b/plan9/mksyscall.go
new file mode 100644
index 0000000..c403de1
--- /dev/null
+++ b/plan9/mksyscall.go
@@ -0,0 +1,393 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build ignore
+
+/*
+This program reads a file containing function prototypes
+(like syscall_plan9.go) and generates system call bodies.
+The prototypes are marked by lines beginning with "//sys"
+and read like func declarations if //sys is replaced by func, but:
+	* The parameter lists must give a name for each argument.
+	  This includes return parameters.
+	* The parameter lists must give a type for each argument:
+	  the (x, y, z int) shorthand is not allowed.
+	* If the return parameter is an error number, it must be named errno.
+
+A line beginning with //sysnb is like //sys, except that the
+goroutine will not be suspended during the execution of the system
+call.  This must only be used for system calls which can never
+block, as otherwise the system call could cause all goroutines to
+hang.
+*/
+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"os"
+	"regexp"
+	"strings"
+)
+
+var (
+	b32       = flag.Bool("b32", false, "32bit big-endian")
+	l32       = flag.Bool("l32", false, "32bit little-endian")
+	plan9     = flag.Bool("plan9", false, "plan9")
+	openbsd   = flag.Bool("openbsd", false, "openbsd")
+	netbsd    = flag.Bool("netbsd", false, "netbsd")
+	dragonfly = flag.Bool("dragonfly", false, "dragonfly")
+	arm       = flag.Bool("arm", false, "arm") // 64-bit value should use (even, odd)-pair
+	tags      = flag.String("tags", "", "build tags")
+	filename  = flag.String("output", "", "output file name (standard output if omitted)")
+)
+
+// cmdLine returns this programs's commandline arguments
+func cmdLine() string {
+	return "go run mksyscall.go " + strings.Join(os.Args[1:], " ")
+}
+
+// buildTags returns build tags
+func buildTags() string {
+	return *tags
+}
+
+// Param is function parameter
+type Param struct {
+	Name string
+	Type string
+}
+
+// usage prints the program usage
+func usage() {
+	fmt.Fprintf(os.Stderr, "usage: go run mksyscall.go [-b32 | -l32] [-tags x,y] [file ...]\n")
+	os.Exit(1)
+}
+
+// parseParamList parses parameter list and returns a slice of parameters
+func parseParamList(list string) []string {
+	list = strings.TrimSpace(list)
+	if list == "" {
+		return []string{}
+	}
+	return regexp.MustCompile(`\s*,\s*`).Split(list, -1)
+}
+
+// parseParam splits a parameter into name and type
+func parseParam(p string) Param {
+	ps := regexp.MustCompile(`^(\S*) (\S*)$`).FindStringSubmatch(p)
+	if ps == nil {
+		fmt.Fprintf(os.Stderr, "malformed parameter: %s\n", p)
+		os.Exit(1)
+	}
+	return Param{ps[1], ps[2]}
+}
+
+func main() {
+	// Get the OS and architecture (using GOARCH_TARGET if it exists)
+	goos := os.Getenv("GOOS")
+	goarch := os.Getenv("GOARCH_TARGET")
+	if goarch == "" {
+		goarch = os.Getenv("GOARCH")
+	}
+
+	// Check that we are using the Docker-based build system if we should
+	if goos == "linux" {
+		if os.Getenv("GOLANG_SYS_BUILD") != "docker" {
+			fmt.Fprintf(os.Stderr, "In the Docker-based build system, mksyscall should not be called directly.\n")
+			fmt.Fprintf(os.Stderr, "See README.md\n")
+			os.Exit(1)
+		}
+	}
+
+	flag.Usage = usage
+	flag.Parse()
+	if len(flag.Args()) <= 0 {
+		fmt.Fprintf(os.Stderr, "no files to parse provided\n")
+		usage()
+	}
+
+	endianness := ""
+	if *b32 {
+		endianness = "big-endian"
+	} else if *l32 {
+		endianness = "little-endian"
+	}
+
+	libc := false
+	if goos == "darwin" && strings.Contains(buildTags(), ",go1.12") {
+		libc = true
+	}
+	trampolines := map[string]bool{}
+
+	text := ""
+	for _, path := range flag.Args() {
+		file, err := os.Open(path)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, err.Error())
+			os.Exit(1)
+		}
+		s := bufio.NewScanner(file)
+		for s.Scan() {
+			t := s.Text()
+			t = strings.TrimSpace(t)
+			t = regexp.MustCompile(`\s+`).ReplaceAllString(t, ` `)
+			nonblock := regexp.MustCompile(`^\/\/sysnb `).FindStringSubmatch(t)
+			if regexp.MustCompile(`^\/\/sys `).FindStringSubmatch(t) == nil && nonblock == nil {
+				continue
+			}
+
+			// Line must be of the form
+			//	func Open(path string, mode int, perm int) (fd int, errno error)
+			// Split into name, in params, out params.
+			f := regexp.MustCompile(`^\/\/sys(nb)? (\w+)\(([^()]*)\)\s*(?:\(([^()]+)\))?\s*(?:=\s*((?i)SYS_[A-Z0-9_]+))?$`).FindStringSubmatch(t)
+			if f == nil {
+				fmt.Fprintf(os.Stderr, "%s:%s\nmalformed //sys declaration\n", path, t)
+				os.Exit(1)
+			}
+			funct, inps, outps, sysname := f[2], f[3], f[4], f[5]
+
+			// Split argument lists on comma.
+			in := parseParamList(inps)
+			out := parseParamList(outps)
+
+			// Try in vain to keep people from editing this file.
+			// The theory is that they jump into the middle of the file
+			// without reading the header.
+			text += "// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT\n\n"
+
+			// Go function header.
+			outDecl := ""
+			if len(out) > 0 {
+				outDecl = fmt.Sprintf(" (%s)", strings.Join(out, ", "))
+			}
+			text += fmt.Sprintf("func %s(%s)%s {\n", funct, strings.Join(in, ", "), outDecl)
+
+			// Check if err return available
+			errvar := ""
+			for _, param := range out {
+				p := parseParam(param)
+				if p.Type == "error" {
+					errvar = p.Name
+					break
+				}
+			}
+
+			// Prepare arguments to Syscall.
+			var args []string
+			n := 0
+			for _, param := range in {
+				p := parseParam(param)
+				if regexp.MustCompile(`^\*`).FindStringSubmatch(p.Type) != nil {
+					args = append(args, "uintptr(unsafe.Pointer("+p.Name+"))")
+				} else if p.Type == "string" && errvar != "" {
+					text += fmt.Sprintf("\tvar _p%d *byte\n", n)
+					text += fmt.Sprintf("\t_p%d, %s = BytePtrFromString(%s)\n", n, errvar, p.Name)
+					text += fmt.Sprintf("\tif %s != nil {\n\t\treturn\n\t}\n", errvar)
+					args = append(args, fmt.Sprintf("uintptr(unsafe.Pointer(_p%d))", n))
+					n++
+				} else if p.Type == "string" {
+					fmt.Fprintf(os.Stderr, path+":"+funct+" uses string arguments, but has no error return\n")
+					text += fmt.Sprintf("\tvar _p%d *byte\n", n)
+					text += fmt.Sprintf("\t_p%d, _ = BytePtrFromString(%s)\n", n, p.Name)
+					args = append(args, fmt.Sprintf("uintptr(unsafe.Pointer(_p%d))", n))
+					n++
+				} else if regexp.MustCompile(`^\[\](.*)`).FindStringSubmatch(p.Type) != nil {
+					// Convert slice into pointer, length.
+					// Have to be careful not to take address of &a[0] if len == 0:
+					// pass dummy pointer in that case.
+					// Used to pass nil, but some OSes or simulators reject write(fd, nil, 0).
+					text += fmt.Sprintf("\tvar _p%d unsafe.Pointer\n", n)
+					text += fmt.Sprintf("\tif len(%s) > 0 {\n\t\t_p%d = unsafe.Pointer(&%s[0])\n\t}", p.Name, n, p.Name)
+					text += fmt.Sprintf(" else {\n\t\t_p%d = unsafe.Pointer(&_zero)\n\t}\n", n)
+					args = append(args, fmt.Sprintf("uintptr(_p%d)", n), fmt.Sprintf("uintptr(len(%s))", p.Name))
+					n++
+				} else if p.Type == "int64" && (*openbsd || *netbsd) {
+					args = append(args, "0")
+					if endianness == "big-endian" {
+						args = append(args, fmt.Sprintf("uintptr(%s>>32)", p.Name), fmt.Sprintf("uintptr(%s)", p.Name))
+					} else if endianness == "little-endian" {
+						args = append(args, fmt.Sprintf("uintptr(%s)", p.Name), fmt.Sprintf("uintptr(%s>>32)", p.Name))
+					} else {
+						args = append(args, fmt.Sprintf("uintptr(%s)", p.Name))
+					}
+				} else if p.Type == "int64" && *dragonfly {
+					if regexp.MustCompile(`^(?i)extp(read|write)`).FindStringSubmatch(funct) == nil {
+						args = append(args, "0")
+					}
+					if endianness == "big-endian" {
+						args = append(args, fmt.Sprintf("uintptr(%s>>32)", p.Name), fmt.Sprintf("uintptr(%s)", p.Name))
+					} else if endianness == "little-endian" {
+						args = append(args, fmt.Sprintf("uintptr(%s)", p.Name), fmt.Sprintf("uintptr(%s>>32)", p.Name))
+					} else {
+						args = append(args, fmt.Sprintf("uintptr(%s)", p.Name))
+					}
+				} else if p.Type == "int64" && endianness != "" {
+					if len(args)%2 == 1 && *arm {
+						// arm abi specifies 64-bit argument uses
+						// (even, odd) pair
+						args = append(args, "0")
+					}
+					if endianness == "big-endian" {
+						args = append(args, fmt.Sprintf("uintptr(%s>>32)", p.Name), fmt.Sprintf("uintptr(%s)", p.Name))
+					} else {
+						args = append(args, fmt.Sprintf("uintptr(%s)", p.Name), fmt.Sprintf("uintptr(%s>>32)", p.Name))
+					}
+				} else {
+					args = append(args, fmt.Sprintf("uintptr(%s)", p.Name))
+				}
+			}
+
+			// Determine which form to use; pad args with zeros.
+			asm := "Syscall"
+			if nonblock != nil {
+				if errvar == "" && goos == "linux" {
+					asm = "RawSyscallNoError"
+				} else {
+					asm = "RawSyscall"
+				}
+			} else {
+				if errvar == "" && goos == "linux" {
+					asm = "SyscallNoError"
+				}
+			}
+			if len(args) <= 3 {
+				for len(args) < 3 {
+					args = append(args, "0")
+				}
+			} else if len(args) <= 6 {
+				asm += "6"
+				for len(args) < 6 {
+					args = append(args, "0")
+				}
+			} else if len(args) <= 9 {
+				asm += "9"
+				for len(args) < 9 {
+					args = append(args, "0")
+				}
+			} else {
+				fmt.Fprintf(os.Stderr, "%s:%s too many arguments to system call\n", path, funct)
+			}
+
+			// System call number.
+			if sysname == "" {
+				sysname = "SYS_" + funct
+				sysname = regexp.MustCompile(`([a-z])([A-Z])`).ReplaceAllString(sysname, `${1}_$2`)
+				sysname = strings.ToUpper(sysname)
+			}
+
+			var libcFn string
+			if libc {
+				asm = "syscall_" + strings.ToLower(asm[:1]) + asm[1:] // internal syscall call
+				sysname = strings.TrimPrefix(sysname, "SYS_")         // remove SYS_
+				sysname = strings.ToLower(sysname)                    // lowercase
+				if sysname == "getdirentries64" {
+					// Special case - libSystem name and
+					// raw syscall name don't match.
+					sysname = "__getdirentries64"
+				}
+				libcFn = sysname
+				sysname = "funcPC(libc_" + sysname + "_trampoline)"
+			}
+
+			// Actual call.
+			arglist := strings.Join(args, ", ")
+			call := fmt.Sprintf("%s(%s, %s)", asm, sysname, arglist)
+
+			// Assign return values.
+			body := ""
+			ret := []string{"_", "_", "_"}
+			doErrno := false
+			for i := 0; i < len(out); i++ {
+				p := parseParam(out[i])
+				reg := ""
+				if p.Name == "err" && !*plan9 {
+					reg = "e1"
+					ret[2] = reg
+					doErrno = true
+				} else if p.Name == "err" && *plan9 {
+					ret[0] = "r0"
+					ret[2] = "e1"
+					break
+				} else {
+					reg = fmt.Sprintf("r%d", i)
+					ret[i] = reg
+				}
+				if p.Type == "bool" {
+					reg = fmt.Sprintf("%s != 0", reg)
+				}
+				if p.Type == "int64" && endianness != "" {
+					// 64-bit number in r1:r0 or r0:r1.
+					if i+2 > len(out) {
+						fmt.Fprintf(os.Stderr, "%s:%s not enough registers for int64 return\n", path, funct)
+					}
+					if endianness == "big-endian" {
+						reg = fmt.Sprintf("int64(r%d)<<32 | int64(r%d)", i, i+1)
+					} else {
+						reg = fmt.Sprintf("int64(r%d)<<32 | int64(r%d)", i+1, i)
+					}
+					ret[i] = fmt.Sprintf("r%d", i)
+					ret[i+1] = fmt.Sprintf("r%d", i+1)
+				}
+				if reg != "e1" || *plan9 {
+					body += fmt.Sprintf("\t%s = %s(%s)\n", p.Name, p.Type, reg)
+				}
+			}
+			if ret[0] == "_" && ret[1] == "_" && ret[2] == "_" {
+				text += fmt.Sprintf("\t%s\n", call)
+			} else {
+				if errvar == "" && goos == "linux" {
+					// raw syscall without error on Linux, see golang.org/issue/22924
+					text += fmt.Sprintf("\t%s, %s := %s\n", ret[0], ret[1], call)
+				} else {
+					text += fmt.Sprintf("\t%s, %s, %s := %s\n", ret[0], ret[1], ret[2], call)
+				}
+			}
+			text += body
+
+			if *plan9 && ret[2] == "e1" {
+				text += "\tif int32(r0) == -1 {\n"
+				text += "\t\terr = e1\n"
+				text += "\t}\n"
+			} else if doErrno {
+				text += "\tif e1 != 0 {\n"
+				text += "\t\terr = errnoErr(e1)\n"
+				text += "\t}\n"
+			}
+			text += "\treturn\n"
+			text += "}\n\n"
+
+			if libc && !trampolines[libcFn] {
+				// some system calls share a trampoline, like read and readlen.
+				trampolines[libcFn] = true
+				// Declare assembly trampoline.
+				text += fmt.Sprintf("func libc_%s_trampoline()\n", libcFn)
+				// Assembly trampoline calls the libc_* function, which this magic
+				// redirects to use the function from libSystem.
+				text += fmt.Sprintf("//go:linkname libc_%s libc_%s\n", libcFn, libcFn)
+				text += fmt.Sprintf("//go:cgo_import_dynamic libc_%s %s \"/usr/lib/libSystem.B.dylib\"\n", libcFn, libcFn)
+				text += "\n"
+			}
+		}
+		if err := s.Err(); err != nil {
+			fmt.Fprintf(os.Stderr, err.Error())
+			os.Exit(1)
+		}
+		file.Close()
+	}
+	fmt.Printf(srcTemplate, cmdLine(), buildTags(), text)
+}
+
+const srcTemplate = `// %s
+// Code generated by the command above; see README.md. DO NOT EDIT.
+
+// +build %s
+
+package plan9
+
+import "unsafe"
+
+%s
+`
diff --git a/plan9/mksyscall.pl b/plan9/mksyscall.pl
deleted file mode 100755
index f01800d..0000000
--- a/plan9/mksyscall.pl
+++ /dev/null
@@ -1,313 +0,0 @@
-#!/usr/bin/env perl
-# Copyright 2009 The Go Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style
-# license that can be found in the LICENSE file.
-
-# This program reads a file containing function prototypes
-# (like syscall_plan9.go) and generates system call bodies.
-# The prototypes are marked by lines beginning with "//sys"
-# and read like func declarations if //sys is replaced by func, but:
-#	* The parameter lists must give a name for each argument.
-#	  This includes return parameters.
-#	* The parameter lists must give a type for each argument:
-#	  the (x, y, z int) shorthand is not allowed.
-#	* If the return parameter is an error number, it must be named errno.
-
-# A line beginning with //sysnb is like //sys, except that the
-# goroutine will not be suspended during the execution of the system
-# call.  This must only be used for system calls which can never
-# block, as otherwise the system call could cause all goroutines to
-# hang.
-
-use strict;
-
-my $cmdline = "mksyscall.pl " . join(' ', @ARGV);
-my $errors = 0;
-my $_32bit = "";
-my $plan9 = 0;
-my $openbsd = 0;
-my $netbsd = 0;
-my $dragonfly = 0;
-my $nacl = 0;
-my $arm = 0; # 64-bit value should use (even, odd)-pair
-
-if($ARGV[0] eq "-b32") {
-	$_32bit = "big-endian";
-	shift;
-} elsif($ARGV[0] eq "-l32") {
-	$_32bit = "little-endian";
-	shift;
-}
-if($ARGV[0] eq "-plan9") {
-	$plan9 = 1;
-	shift;
-}
-if($ARGV[0] eq "-openbsd") {
-	$openbsd = 1;
-	shift;
-}
-if($ARGV[0] eq "-netbsd") {
-	$netbsd = 1;
-	shift;
-}
-if($ARGV[0] eq "-dragonfly") {
-	$dragonfly = 1;
-	shift;
-}
-if($ARGV[0] eq "-nacl") {
-	$nacl = 1;
-	shift;
-}
-if($ARGV[0] eq "-arm") {
-	$arm = 1;
-	shift;
-}
-
-if($ARGV[0] =~ /^-/) {
-	print STDERR "usage: mksyscall.pl [-b32 | -l32] [file ...]\n";
-	exit 1;
-}
-
-sub parseparamlist($) {
-	my ($list) = @_;
-	$list =~ s/^\s*//;
-	$list =~ s/\s*$//;
-	if($list eq "") {
-		return ();
-	}
-	return split(/\s*,\s*/, $list);
-}
-
-sub parseparam($) {
-	my ($p) = @_;
-	if($p !~ /^(\S*) (\S*)$/) {
-		print STDERR "$ARGV:$.: malformed parameter: $p\n";
-		$errors = 1;
-		return ("xx", "int");
-	}
-	return ($1, $2);
-}
-
-my $text = "";
-while(<>) {
-	chomp;
-	s/\s+/ /g;
-	s/^\s+//;
-	s/\s+$//;
-	my $nonblock = /^\/\/sysnb /;
-	next if !/^\/\/sys / && !$nonblock;
-
-	# Line must be of the form
-	#	func Open(path string, mode int, perm int) (fd int, errno error)
-	# Split into name, in params, out params.
-	if(!/^\/\/sys(nb)? (\w+)\(([^()]*)\)\s*(?:\(([^()]+)\))?\s*(?:=\s*((?i)SYS_[A-Z0-9_]+))?$/) {
-		print STDERR "$ARGV:$.: malformed //sys declaration\n";
-		$errors = 1;
-		next;
-	}
-	my ($func, $in, $out, $sysname) = ($2, $3, $4, $5);
-
-	# Split argument lists on comma.
-	my @in = parseparamlist($in);
-	my @out = parseparamlist($out);
-
-	# Try in vain to keep people from editing this file.
-	# The theory is that they jump into the middle of the file
-	# without reading the header.
-	$text .= "// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT\n\n";
-
-	# Go function header.
-	my $out_decl = @out ? sprintf(" (%s)", join(', ', @out)) : "";
-	$text .= sprintf "func %s(%s)%s {\n", $func, join(', ', @in), $out_decl;
-
-	# Check if err return available
-	my $errvar = "";
-	foreach my $p (@out) {
-		my ($name, $type) = parseparam($p);
-		if($type eq "error") {
-			$errvar = $name;
-			last;
-		}
-	}
-
-	# Prepare arguments to Syscall.
-	my @args = ();
-	my $n = 0;
-	foreach my $p (@in) {
-		my ($name, $type) = parseparam($p);
-		if($type =~ /^\*/) {
-			push @args, "uintptr(unsafe.Pointer($name))";
-		} elsif($type eq "string" && $errvar ne "") {
-			$text .= "\tvar _p$n *byte\n";
-			$text .= "\t_p$n, $errvar = BytePtrFromString($name)\n";
-			$text .= "\tif $errvar != nil {\n\t\treturn\n\t}\n";
-			push @args, "uintptr(unsafe.Pointer(_p$n))";
-			$n++;
-		} elsif($type eq "string") {
-			print STDERR "$ARGV:$.: $func uses string arguments, but has no error return\n";
-			$text .= "\tvar _p$n *byte\n";
-			$text .= "\t_p$n, _ = BytePtrFromString($name)\n";
-			push @args, "uintptr(unsafe.Pointer(_p$n))";
-			$n++;
-		} elsif($type =~ /^\[\](.*)/) {
-			# Convert slice into pointer, length.
-			# Have to be careful not to take address of &a[0] if len == 0:
-			# pass dummy pointer in that case.
-			# Used to pass nil, but some OSes or simulators reject write(fd, nil, 0).
-			$text .= "\tvar _p$n unsafe.Pointer\n";
-			$text .= "\tif len($name) > 0 {\n\t\t_p$n = unsafe.Pointer(\&${name}[0])\n\t}";
-			$text .= " else {\n\t\t_p$n = unsafe.Pointer(&_zero)\n\t}";
-			$text .= "\n";
-			push @args, "uintptr(_p$n)", "uintptr(len($name))";
-			$n++;
-		} elsif($type eq "int64" && ($openbsd || $netbsd)) {
-			push @args, "0";
-			if($_32bit eq "big-endian") {
-				push @args, "uintptr($name>>32)", "uintptr($name)";
-			} elsif($_32bit eq "little-endian") {
-				push @args, "uintptr($name)", "uintptr($name>>32)";
-			} else {
-				push @args, "uintptr($name)";
-			}
-		} elsif($type eq "int64" && $dragonfly) {
-			if ($func !~ /^extp(read|write)/i) {
-				push @args, "0";
-			}
-			if($_32bit eq "big-endian") {
-				push @args, "uintptr($name>>32)", "uintptr($name)";
-			} elsif($_32bit eq "little-endian") {
-				push @args, "uintptr($name)", "uintptr($name>>32)";
-			} else {
-				push @args, "uintptr($name)";
-			}
-		} elsif($type eq "int64" && $_32bit ne "") {
-			if(@args % 2 && $arm) {
-				# arm abi specifies 64-bit argument uses 
-				# (even, odd) pair
-				push @args, "0"
-			}
-			if($_32bit eq "big-endian") {
-				push @args, "uintptr($name>>32)", "uintptr($name)";
-			} else {
-				push @args, "uintptr($name)", "uintptr($name>>32)";
-			}
-		} else {
-			push @args, "uintptr($name)";
-		}
-	}
-
-	# Determine which form to use; pad args with zeros.
-	my $asm = "Syscall";
-	if ($nonblock) {
-		$asm = "RawSyscall";
-	}
-	if(@args <= 3) {
-		while(@args < 3) {
-			push @args, "0";
-		}
-	} elsif(@args <= 6) {
-		$asm .= "6";
-		while(@args < 6) {
-			push @args, "0";
-		}
-	} elsif(@args <= 9) {
-		$asm .= "9";
-		while(@args < 9) {
-			push @args, "0";
-		}
-	} else {
-		print STDERR "$ARGV:$.: too many arguments to system call\n";
-	}
-
-	# System call number.
-	if($sysname eq "") {
-		$sysname = "SYS_$func";
-		$sysname =~ s/([a-z])([A-Z])/${1}_$2/g;	# turn FooBar into Foo_Bar
-		$sysname =~ y/a-z/A-Z/;
-		if($nacl) {
-			$sysname =~ y/A-Z/a-z/;
-		}
-	}
-
-	# Actual call.
-	my $args = join(', ', @args);
-	my $call = "$asm($sysname, $args)";
-
-	# Assign return values.
-	my $body = "";
-	my @ret = ("_", "_", "_");
-	my $do_errno = 0;
-	for(my $i=0; $i<@out; $i++) {
-		my $p = $out[$i];
-		my ($name, $type) = parseparam($p);
-		my $reg = "";
-		if($name eq "err" && !$plan9) {
-			$reg = "e1";
-			$ret[2] = $reg;
-			$do_errno = 1;
-		} elsif($name eq "err" && $plan9) {
-			$ret[0] = "r0";
-			$ret[2] = "e1";
-			next;
-		} else {
-			$reg = sprintf("r%d", $i);
-			$ret[$i] = $reg;
-		}
-		if($type eq "bool") {
-			$reg = "$reg != 0";
-		}
-		if($type eq "int64" && $_32bit ne "") {
-			# 64-bit number in r1:r0 or r0:r1.
-			if($i+2 > @out) {
-				print STDERR "$ARGV:$.: not enough registers for int64 return\n";
-			}
-			if($_32bit eq "big-endian") {
-				$reg = sprintf("int64(r%d)<<32 | int64(r%d)", $i, $i+1);
-			} else {
-				$reg = sprintf("int64(r%d)<<32 | int64(r%d)", $i+1, $i);
-			}
-			$ret[$i] = sprintf("r%d", $i);
-			$ret[$i+1] = sprintf("r%d", $i+1);
-		}
-		if($reg ne "e1" || $plan9) {
-			$body .= "\t$name = $type($reg)\n";
-		}
-	}
-	if ($ret[0] eq "_" && $ret[1] eq "_" && $ret[2] eq "_") {
-		$text .= "\t$call\n";
-	} else {
-		$text .= "\t$ret[0], $ret[1], $ret[2] := $call\n";
-	}
-	$text .= $body;
-	
-	if ($plan9 && $ret[2] eq "e1") {
-		$text .= "\tif int32(r0) == -1 {\n";
-		$text .= "\t\terr = e1\n";
-		$text .= "\t}\n";
-	} elsif ($do_errno) {
-		$text .= "\tif e1 != 0 {\n";
-		$text .= "\t\terr = e1\n";
-		$text .= "\t}\n";
-	}
-	$text .= "\treturn\n";
-	$text .= "}\n\n";
-}
-
-chomp $text;
-chomp $text;
-
-if($errors) {
-	exit 1;
-}
-
-print <<EOF;
-// $cmdline
-// Code generated by the command above; DO NOT EDIT.
-
-package plan9
-
-import "unsafe"
-
-$text
-EOF
-exit 0;
diff --git a/plan9/zsyscall_plan9_386.go b/plan9/zsyscall_plan9_386.go
index 38fdee9..6819bc2 100644
--- a/plan9/zsyscall_plan9_386.go
+++ b/plan9/zsyscall_plan9_386.go
@@ -1,5 +1,7 @@
-// mksyscall.pl -l32 -plan9 syscall_plan9.go
-// Code generated by the command above; DO NOT EDIT.
+// go run mksyscall.go -l32 -plan9 -tags plan9,386 syscall_plan9.go
+// Code generated by the command above; see README.md. DO NOT EDIT.
+
+// +build plan9,386
 
 package plan9
 
diff --git a/plan9/zsyscall_plan9_amd64.go b/plan9/zsyscall_plan9_amd64.go
index 38fdee9..418abbb 100644
--- a/plan9/zsyscall_plan9_amd64.go
+++ b/plan9/zsyscall_plan9_amd64.go
@@ -1,5 +1,7 @@
-// mksyscall.pl -l32 -plan9 syscall_plan9.go
-// Code generated by the command above; DO NOT EDIT.
+// go run mksyscall.go -l32 -plan9 -tags plan9,amd64 syscall_plan9.go
+// Code generated by the command above; see README.md. DO NOT EDIT.
+
+// +build plan9,amd64
 
 package plan9
 
diff --git a/plan9/zsyscall_plan9_arm.go b/plan9/zsyscall_plan9_arm.go
index 4ff9e23..3e8a1a5 100644
--- a/plan9/zsyscall_plan9_arm.go
+++ b/plan9/zsyscall_plan9_arm.go
@@ -1,5 +1,5 @@
-// mksyscall.pl -l32 -plan9 -tags plan9,arm syscall_plan9.go
-// Code generated by the command above; DO NOT EDIT.
+// go run mksyscall.go -l32 -plan9 -tags plan9,arm syscall_plan9.go
+// Code generated by the command above; see README.md. DO NOT EDIT.
 
 // +build plan9,arm