syscall: implement getwd on Solaris

In support of the changes required for #8609, it was suggested that
syscall.getwd() be updated to work on Solaris first since the runtime
uses it and today it's unimplemented.

Fixes #12507

Change-Id: Ifb58ac9db8540936d5685c2c58bdc465dbc836cb
Reviewed-on: https://go-review.googlesource.com/14420Reviewed-by: Aram Hăvărneanu <aram@mgk.ro>

src/syscall/mkerrors.sh

@@ -13,6 +13,11 @@ export LC_CTYPE=C
 
 CC=${CC:-gcc}
 
+if [[ "$GOOS" -eq "solaris" ]]; then
+	# Assumes GNU versions of utilities in PATH.
+	export PATH=/usr/gnu/bin:$PATH
+fi
+
 uname=$(uname)
 
 includes_Darwin='
@@ -195,6 +200,7 @@ includes_OpenBSD='
 '
 
 includes_SunOS='
+#include <limits.h>
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <sys/sockio.h>

src/syscall/mksyscall_solaris.pl

@@ -38,6 +38,11 @@ if($ARGV[0] =~ /^-/) {
 	exit 1;
 }
 
+if($ENV{'GOARCH'} eq "" || $ENV{'GOOS'} eq "") {
+	print STDERR "GOARCH or GOOS not defined in environment\n";
+	exit 1;
+}
+
 sub parseparamlist($) {
 	my ($list) = @_;
 	$list =~ s/^\s*//;
@@ -60,9 +65,9 @@ sub parseparam($) {
 
 my $package = "";
 my $text = "";
-my $vars = "";
 my $dynimports = "";
 my $linknames = "";
+my @vars = ();
 while(<>) {
 	chomp;
 	s/\s+/ /g;
@@ -100,20 +105,19 @@ while(<>) {
 	}
 
 	# System call pointer variable name.
-	my $sysvarname = "libc_$sysname";
+	my $sysvarname = "libc_${sysname}";
 
 	my $strconvfunc = "BytePtrFromString";
 	my $strconvtype = "*byte";
 
-	# Library proc address variable.
 	$sysname =~ y/A-Z/a-z/; # All libc functions are lowercase.
-	if($vars eq "") {
-		$vars .= "\t$sysvarname";
-	} else {
-		$vars .= ",\n\t$sysvarname";
-	}
-	$dynimports .= "//go:cgo_import_dynamic $sysvarname $sysname \"$modname.so\"\n";
-	$linknames .= "//go:linkname $sysvarname $sysvarname\n";
+
+	# Runtime import of function to allow cross-platform builds.
+	$dynimports .= "//go:cgo_import_dynamic ${sysvarname} ${sysname} \"$modname.so\"\n";
+	# Link symbol to proc address variable.
+	$linknames .= "//go:linkname ${sysvarname} ${sysvarname}\n";
+	# Library proc address variable.
+	push @vars, $sysvarname;
 
 	# Go function header.
 	$out = join(', ', @out);
@@ -264,6 +268,8 @@ print <<EOF;
 // $cmdline
 // MACHINE GENERATED BY THE COMMAND ABOVE; DO NOT EDIT
 
+// +build $ENV{'GOARCH'},$ENV{'GOOS'}
+
 package $package
 
 import "unsafe"
@@ -271,17 +277,20 @@ EOF
 
 print "import \"syscall\"\n" if $package ne "syscall";
 
-print <<EOF;
+my $vardecls = "\t" . join(",\n\t", @vars);
+$vardecls .= " libcFunc";
+
+chomp($_=<<EOF);
 
 $dynimports
 $linknames
 type libcFunc uintptr
 
 var (
-$vars libcFunc
+$vardecls
 )
 
 $text
-
 EOF
+print $_;
 exit 0;

src/syscall/syscall_solaris.go

@@ -142,12 +142,23 @@ func Getsockname(fd int) (sa Sockaddr, err error) {
 	return anyToSockaddr(&rsa)
 }
 
-// The const provides a compile-time constant so clients
-// can adjust to whether there is a working Getwd and avoid
-// even linking this function into the binary.  See ../os/getwd.go.
-const ImplementsGetwd = false
+const ImplementsGetwd = true
 
-func Getwd() (string, error) { return "", ENOTSUP }
+//sys	Getcwd(buf []byte) (n int, err error)
+
+func Getwd() (wd string, err error) {
+	var buf [PathMax]byte
+	// Getcwd will return an error if it failed for any reason.
+	_, err = Getcwd(buf[0:])
+	if err != nil {
+		return "", err
+	}
+	n := clen(buf[:])
+	if n < 1 {
+		return "", EINVAL
+	}
+	return string(buf[:n]), nil
+}
 
 /*
  * Wrapped

src/syscall/types_solaris.go

@@ -15,8 +15,14 @@ package syscall
 
 /*
 #define KERNEL
+// These defines ensure that builds done on newer versions of Solaris are
+// backwards-compatible with older versions of Solaris and
+// OpenSolaris-based derivatives.
+#define __USE_SUNOS_SOCKETS__          // msghdr
+#define __USE_LEGACY_PROTOTYPES__      // iovec
 #include <dirent.h>
 #include <fcntl.h>
+#include <limits.h>
 #include <signal.h>
 #include <termios.h>
 #include <stdio.h>
@@ -69,6 +75,7 @@ const (
 	sizeofInt      = C.sizeof_int
 	sizeofLong     = C.sizeof_long
 	sizeofLongLong = C.sizeof_longlong
+	PathMax        = C.PATH_MAX
 )
 
 // Basic types

src/syscall/zsyscall_solaris_amd64.go

@@ -7,6 +7,7 @@ package syscall
 
 import "unsafe"
 
+//go:cgo_import_dynamic libc_Getcwd getcwd "libc.so"
 //go:cgo_import_dynamic libc_getgroups getgroups "libc.so"
 //go:cgo_import_dynamic libc_setgroups setgroups "libc.so"
 //go:cgo_import_dynamic libc_fcntl fcntl "libc.so"
@@ -89,6 +90,7 @@ import "unsafe"
 //go:cgo_import_dynamic libc_recvfrom recvfrom "libsocket.so"
 //go:cgo_import_dynamic libc_recvmsg recvmsg "libsocket.so"
 
+//go:linkname libc_Getcwd libc_Getcwd
 //go:linkname libc_getgroups libc_getgroups
 //go:linkname libc_setgroups libc_setgroups
 //go:linkname libc_fcntl libc_fcntl
@@ -174,6 +176,7 @@ import "unsafe"
 type libcFunc uintptr
 
 var (
+	libc_Getcwd,
 	libc_getgroups,
 	libc_setgroups,
 	libc_fcntl,
@@ -257,6 +260,19 @@ var (
 	libc_recvmsg libcFunc
 )
 
+func Getcwd(buf []byte) (n int, err error) {
+	var _p0 *byte
+	if len(buf) > 0 {
+		_p0 = &buf[0]
+	}
+	r0, _, e1 := sysvicall6(uintptr(unsafe.Pointer(&libc_Getcwd)), 2, uintptr(unsafe.Pointer(_p0)), uintptr(len(buf)), 0, 0, 0, 0)
+	n = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
 func getgroups(ngid int, gid *_Gid_t) (n int, err error) {
 	r0, _, e1 := rawSysvicall6(uintptr(unsafe.Pointer(&libc_getgroups)), 2, uintptr(ngid), uintptr(unsafe.Pointer(gid)), 0, 0, 0, 0)
 	n = int(r0)

src/syscall/ztypes_solaris_amd64.go

@@ -11,6 +11,7 @@ const (
 	sizeofInt      = 0x4
 	sizeofLong     = 0x8
 	sizeofLongLong = 0x8
+	PathMax        = 0x400
 )
 
 type (