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Text file src/syscall/mksyscall.pl

Documentation: syscall

     1#!/usr/bin/env perl
     2# Copyright 2009 The Go Authors. All rights reserved.
     3# Use of this source code is governed by a BSD-style
     4# license that can be found in the LICENSE file.
     5
     6# This program reads a file containing function prototypes
     7# (like syscall_darwin.go) and generates system call bodies.
     8# The prototypes are marked by lines beginning with "//sys"
     9# and read like func declarations if //sys is replaced by func, but:
    10#	* The parameter lists must give a name for each argument.
    11#	  This includes return parameters.
    12#	* The parameter lists must give a type for each argument:
    13#	  the (x, y, z int) shorthand is not allowed.
    14#	* If the return parameter is an error number, it must be named errno.
    15
    16# A line beginning with //sysnb is like //sys, except that the
    17# goroutine will not be suspended during the execution of the system
    18# call.  This must only be used for system calls which can never
    19# block, as otherwise the system call could cause all goroutines to
    20# hang.
    21
    22use strict;
    23
    24my $cmdline = "mksyscall.pl " . join(' ', @ARGV);
    25my $errors = 0;
    26my $_32bit = "";
    27my $plan9 = 0;
    28my $darwin = 0;
    29my $openbsd = 0;
    30my $netbsd = 0;
    31my $dragonfly = 0;
    32my $arm = 0; # 64-bit value should use (even, odd)-pair
    33my $tags = "";  # build tags
    34
    35if($ARGV[0] eq "-b32") {
    36	$_32bit = "big-endian";
    37	shift;
    38} elsif($ARGV[0] eq "-l32") {
    39	$_32bit = "little-endian";
    40	shift;
    41}
    42if($ARGV[0] eq "-plan9") {
    43	$plan9 = 1;
    44	shift;
    45}
    46if($ARGV[0] eq "-darwin") {
    47	$darwin = 1;
    48	shift;
    49}
    50if($ARGV[0] eq "-openbsd") {
    51	$openbsd = 1;
    52	shift;
    53}
    54if($ARGV[0] eq "-netbsd") {
    55	$netbsd = 1;
    56	shift;
    57}
    58if($ARGV[0] eq "-dragonfly") {
    59	$dragonfly = 1;
    60	shift;
    61}
    62if($ARGV[0] eq "-arm") {
    63	$arm = 1;
    64	shift;
    65}
    66if($ARGV[0] eq "-tags") {
    67	shift;
    68	$tags = $ARGV[0];
    69	shift;
    70}
    71
    72if($ARGV[0] =~ /^-/) {
    73	print STDERR "usage: mksyscall.pl [-b32 | -l32] [-tags x,y] [file ...]\n";
    74	exit 1;
    75}
    76
    77sub parseparamlist($) {
    78	my ($list) = @_;
    79	$list =~ s/^\s*//;
    80	$list =~ s/\s*$//;
    81	if($list eq "") {
    82		return ();
    83	}
    84	return split(/\s*,\s*/, $list);
    85}
    86
    87sub parseparam($) {
    88	my ($p) = @_;
    89	if($p !~ /^(\S*) (\S*)$/) {
    90		print STDERR "$ARGV:$.: malformed parameter: $p\n";
    91		$errors = 1;
    92		return ("xx", "int");
    93	}
    94	return ($1, $2);
    95}
    96
    97# set of trampolines we've already generated
    98my %trampolines;
    99
   100my $text = "";
   101while(<>) {
   102	chomp;
   103	s/\s+/ /g;
   104	s/^\s+//;
   105	s/\s+$//;
   106	my $nonblock = /^\/\/sysnb /;
   107	next if !/^\/\/sys / && !$nonblock;
   108
   109	# Line must be of the form
   110	#	func Open(path string, mode int, perm int) (fd int, errno error)
   111	# Split into name, in params, out params.
   112	if(!/^\/\/sys(nb)? (\w+)\(([^()]*)\)\s*(?:\(([^()]+)\))?\s*(?:=\s*((?i)_?SYS_[A-Z0-9_]+))?$/) {
   113		print STDERR "$ARGV:$.: malformed //sys declaration\n";
   114		$errors = 1;
   115		next;
   116	}
   117	my ($func, $in, $out, $sysname) = ($2, $3, $4, $5);
   118
   119	# Split argument lists on comma.
   120	my @in = parseparamlist($in);
   121	my @out = parseparamlist($out);
   122
   123	# Try in vain to keep people from editing this file.
   124	# The theory is that they jump into the middle of the file
   125	# without reading the header.
   126	$text .= "// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT\n\n";
   127
   128	if ($darwin && $func eq "ptrace") {
   129		# The ptrace function is called from forkAndExecInChild where stack
   130		# growth is forbidden.
   131		$text .= "//go:nosplit\n"
   132	}
   133
   134	# Go function header.
   135	my $out_decl = @out ? sprintf(" (%s)", join(', ', @out)) : "";
   136	$text .= sprintf "func %s(%s)%s {\n", $func, join(', ', @in), $out_decl;
   137
   138	# Check if err return available
   139	my $errvar = "";
   140	foreach my $p (@out) {
   141		my ($name, $type) = parseparam($p);
   142		if($type eq "error") {
   143			$errvar = $name;
   144			last;
   145		}
   146	}
   147
   148	# Prepare arguments to Syscall.
   149	my @args = ();
   150	my $n = 0;
   151	foreach my $p (@in) {
   152		my ($name, $type) = parseparam($p);
   153		if($type =~ /^\*/) {
   154			push @args, "uintptr(unsafe.Pointer($name))";
   155		} elsif($type eq "string" && $errvar ne "") {
   156			$text .= "\tvar _p$n *byte\n";
   157			$text .= "\t_p$n, $errvar = BytePtrFromString($name)\n";
   158			$text .= "\tif $errvar != nil {\n\t\treturn\n\t}\n";
   159			push @args, "uintptr(unsafe.Pointer(_p$n))";
   160			$n++;
   161		} elsif($type eq "string") {
   162			print STDERR "$ARGV:$.: $func uses string arguments, but has no error return\n";
   163			$text .= "\tvar _p$n *byte\n";
   164			$text .= "\t_p$n, _ = BytePtrFromString($name)\n";
   165			push @args, "uintptr(unsafe.Pointer(_p$n))";
   166			$n++;
   167		} elsif($type =~ /^\[\](.*)/) {
   168			# Convert slice into pointer, length.
   169			# Have to be careful not to take address of &a[0] if len == 0:
   170			# pass dummy pointer in that case.
   171			# Used to pass nil, but some OSes or simulators reject write(fd, nil, 0).
   172			$text .= "\tvar _p$n unsafe.Pointer\n";
   173			$text .= "\tif len($name) > 0 {\n\t\t_p$n = unsafe.Pointer(\&${name}[0])\n\t}";
   174			$text .= " else {\n\t\t_p$n = unsafe.Pointer(&_zero)\n\t}";
   175			$text .= "\n";
   176			push @args, "uintptr(_p$n)", "uintptr(len($name))";
   177			$n++;
   178		} elsif($type eq "int64" && ($openbsd || $netbsd)) {
   179			push @args, "0";
   180			if($_32bit eq "big-endian") {
   181				push @args, "uintptr($name>>32)", "uintptr($name)";
   182			} elsif($_32bit eq "little-endian") {
   183				push @args, "uintptr($name)", "uintptr($name>>32)";
   184			} else {
   185				push @args, "uintptr($name)";
   186			}
   187		} elsif($type eq "int64" && $dragonfly) {
   188			if ($func !~ /^extp(read|write)/i) {
   189				push @args, "0";
   190			}
   191			if($_32bit eq "big-endian") {
   192				push @args, "uintptr($name>>32)", "uintptr($name)";
   193			} elsif($_32bit eq "little-endian") {
   194				push @args, "uintptr($name)", "uintptr($name>>32)";
   195			} else {
   196				push @args, "uintptr($name)";
   197			}
   198		} elsif($type eq "int64" && $_32bit ne "") {
   199			if(@args % 2 && $arm) {
   200				# arm abi specifies 64-bit argument uses
   201				# (even, odd) pair
   202				push @args, "0"
   203			}
   204			if($_32bit eq "big-endian") {
   205				push @args, "uintptr($name>>32)", "uintptr($name)";
   206			} else {
   207				push @args, "uintptr($name)", "uintptr($name>>32)";
   208			}
   209		} else {
   210			push @args, "uintptr($name)";
   211		}
   212	}
   213
   214	# Determine which form to use; pad args with zeros.
   215	my $asm = "Syscall";
   216	if ($nonblock) {
   217		if ($errvar eq "" && $ENV{'GOOS'} eq "linux") {
   218			$asm = "rawSyscallNoError";
   219		} else {
   220			$asm = "RawSyscall";
   221		}
   222	}
   223	if ($darwin) {
   224		# Call unexported syscall functions (which take
   225		# libc functions instead of syscall numbers).
   226		$asm = lcfirst($asm);
   227	}
   228	if(@args <= 3) {
   229		while(@args < 3) {
   230			push @args, "0";
   231		}
   232	} elsif(@args <= 6) {
   233		$asm .= "6";
   234		while(@args < 6) {
   235			push @args, "0";
   236		}
   237	} elsif(@args <= 9) {
   238		$asm .= "9";
   239		while(@args < 9) {
   240			push @args, "0";
   241		}
   242	} else {
   243		print STDERR "$ARGV:$.: too many arguments to system call\n";
   244	}
   245
   246	if ($darwin) {
   247		# Use extended versions for calls that generate a 64-bit result.
   248		my ($name, $type) = parseparam($out[0]);
   249		if ($type eq "int64" || ($type eq "uintptr" && $_32bit eq "")) {
   250			$asm .= "X";
   251		}
   252	}
   253
   254	# System call number.
   255	my $funcname = "";
   256	if($sysname eq "") {
   257		$sysname = "SYS_$func";
   258		$sysname =~ s/([a-z])([A-Z])/${1}_$2/g;	# turn FooBar into Foo_Bar
   259		$sysname =~ y/a-z/A-Z/;
   260		if($darwin) {
   261			$sysname =~ y/A-Z/a-z/;
   262			$sysname = substr $sysname, 4;
   263			$funcname = "libc_$sysname";
   264		}
   265	}
   266	if($darwin) {
   267		if($funcname eq "") {
   268			$sysname = substr $sysname, 4;
   269			$funcname = "libc_$sysname";
   270		}
   271		$sysname = "funcPC(${funcname}_trampoline)";
   272	}
   273
   274	# Actual call.
   275	my $args = join(', ', @args);
   276	my $call = "$asm($sysname, $args)";
   277
   278	# Assign return values.
   279	my $body = "";
   280	my @ret = ("_", "_", "_");
   281	my $do_errno = 0;
   282	for(my $i=0; $i<@out; $i++) {
   283		my $p = $out[$i];
   284		my ($name, $type) = parseparam($p);
   285		my $reg = "";
   286		if($name eq "err" && !$plan9) {
   287			$reg = "e1";
   288			$ret[2] = $reg;
   289			$do_errno = 1;
   290		} elsif($name eq "err" && $plan9) {
   291			$ret[0] = "r0";
   292			$ret[2] = "e1";
   293			next;
   294		} else {
   295			$reg = sprintf("r%d", $i);
   296			$ret[$i] = $reg;
   297		}
   298		if($type eq "bool") {
   299			$reg = "$reg != 0";
   300		}
   301		if($type eq "int64" && $_32bit ne "") {
   302			# 64-bit number in r1:r0 or r0:r1.
   303			if($i+2 > @out) {
   304				print STDERR "$ARGV:$.: not enough registers for int64 return\n";
   305			}
   306			if($_32bit eq "big-endian") {
   307				$reg = sprintf("int64(r%d)<<32 | int64(r%d)", $i, $i+1);
   308			} else {
   309				$reg = sprintf("int64(r%d)<<32 | int64(r%d)", $i+1, $i);
   310			}
   311			$ret[$i] = sprintf("r%d", $i);
   312			$ret[$i+1] = sprintf("r%d", $i+1);
   313		}
   314		if($reg ne "e1" || $plan9) {
   315			$body .= "\t$name = $type($reg)\n";
   316		}
   317	}
   318	if ($ret[0] eq "_" && $ret[1] eq "_" && $ret[2] eq "_") {
   319		$text .= "\t$call\n";
   320	} else {
   321		if ($errvar eq "" && $ENV{'GOOS'} eq "linux") {
   322			# raw syscall without error on Linux, see golang.org/issue/22924
   323			$text .= "\t$ret[0], $ret[1] := $call\n";
   324		} else {
   325			$text .= "\t$ret[0], $ret[1], $ret[2] := $call\n";
   326		}
   327	}
   328	$text .= $body;
   329
   330	if ($plan9 && $ret[2] eq "e1") {
   331		$text .= "\tif int32(r0) == -1 {\n";
   332		$text .= "\t\terr = e1\n";
   333		$text .= "\t}\n";
   334	} elsif ($do_errno) {
   335		$text .= "\tif e1 != 0 {\n";
   336		$text .= "\t\terr = errnoErr(e1)\n";
   337		$text .= "\t}\n";
   338	}
   339	$text .= "\treturn\n";
   340	$text .= "}\n\n";
   341	if($darwin) {
   342		if (not exists $trampolines{$funcname}) {
   343			$trampolines{$funcname} = 1;
   344			# The assembly trampoline that jumps to the libc routine.
   345			$text .= "func ${funcname}_trampoline()\n";
   346			# Map syscall.funcname to just plain funcname.
   347			# (The jump to this function is in the assembly trampoline, generated by mksyscallasm_darwin.go.)
   348			$text .= "//go:linkname $funcname $funcname\n";
   349			# Tell the linker that funcname can be found in libSystem using varname without the libc_ prefix.
   350			my $basename = substr $funcname, 5;
   351			$text .= "//go:cgo_import_dynamic $funcname $basename \"/usr/lib/libSystem.B.dylib\"\n\n";
   352		}
   353	}
   354}
   355
   356chomp $text;
   357chomp $text;
   358
   359if($errors) {
   360	exit 1;
   361}
   362
   363print <<EOF;
   364// $cmdline
   365// Code generated by the command above; DO NOT EDIT.
   366
   367// +build $tags
   368
   369package syscall
   370
   371import "unsafe"
   372
   373$text
   374EOF
   375exit 0;

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