runtime,os,syscall,internal/poll: replace getdirentries on iOS

The getdirentries syscall is considered private API on iOS and is
rejected by the App Store submission checks. Replace it with the
fdopendir/readdir_r/closedir syscalls.

Fixes #28984

Change-Id: I73341b124310e9cb34834a95f946769f337ec5b7
Reviewed-on: https://go-review.googlesource.com/c/153338
Reviewed-by: Keith Randall <khr@golang.org>

src/internal/poll/fd_opendir_ios.go

@@ -0,0 +1,35 @@
+// 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 darwin
+// +build arm arm64
+
+package poll
+
+import (
+	"syscall"
+	_ "unsafe" // for go:linkname
+)
+
+// OpenDir returns a pointer to a DIR structure suitable for
+// ReadDir. In case of an error, the name of the failed
+// syscall is returned along with a syscall.Errno.
+func (fd *FD) OpenDir() (uintptr, string, error) {
+	// fdopendir(3) takes control of the file descriptor,
+	// so use a dup.
+	fd2, call, err := fd.Dup()
+	if err != nil {
+		return 0, call, err
+	}
+	dir, err := fdopendir(fd2)
+	if err != nil {
+		syscall.Close(fd2)
+		return 0, "fdopendir", err
+	}
+	return dir, "", nil
+}
+
+// Implemented in syscall/syscall_darwin.go.
+//go:linkname fdopendir syscall.fdopendir
+func fdopendir(fd int) (dir uintptr, err error)

src/os/dir_ios.go

@@ -0,0 +1,87 @@
+// 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.
+
+// +build darwin
+// +build arm arm64
+
+package os
+
+import (
+	"io"
+	"runtime"
+	"syscall"
+	"unsafe"
+)
+
+// Auxiliary information if the File describes a directory
+type dirInfo struct {
+	dir uintptr // Pointer to DIR structure from dirent.h
+}
+
+func (d *dirInfo) close() {
+	if d.dir == 0 {
+		return
+	}
+	closedir(d.dir)
+	d.dir = 0
+}
+
+func (f *File) readdirnames(n int) (names []string, err error) {
+	if f.dirinfo == nil {
+		dir, call, errno := f.pfd.OpenDir()
+		if errno != nil {
+			return nil, wrapSyscallError(call, errno)
+		}
+		f.dirinfo = &dirInfo{
+			dir: dir,
+		}
+	}
+	d := f.dirinfo
+
+	size := n
+	if size <= 0 {
+		size = 100
+		n = -1
+	}
+
+	names = make([]string, 0, size)
+	var dirent syscall.Dirent
+	var entptr uintptr
+	for len(names) < size {
+		if res := readdir_r(d.dir, uintptr(unsafe.Pointer(&dirent)), uintptr(unsafe.Pointer(&entptr))); res != 0 {
+			return names, wrapSyscallError("readdir", syscall.Errno(res))
+		}
+		if entptr == 0 { // EOF
+			break
+		}
+		if dirent.Ino == 0 {
+			continue
+		}
+		name := (*[len(syscall.Dirent{}.Name)]byte)(unsafe.Pointer(&dirent.Name))[:]
+		for i, c := range name {
+			if c == 0 {
+				name = name[:i]
+				break
+			}
+		}
+		// Check for useless names before allocating a string.
+		if string(name) == "." || string(name) == ".." {
+			continue
+		}
+		names = append(names, string(name))
+		runtime.KeepAlive(f)
+	}
+	if n >= 0 && len(names) == 0 {
+		return names, io.EOF
+	}
+	return names, nil
+}
+
+// Implemented in syscall/syscall_darwin.go.
+
+//go:linkname closedir syscall.closedir
+func closedir(dir uintptr) (err error)
+
+//go:linkname readdir_r syscall.readdir_r
+func readdir_r(dir, entry, result uintptr) (res int)

src/os/dir_unix.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build aix darwin dragonfly freebsd js,wasm linux nacl netbsd openbsd solaris
+// +build aix darwin,!arm,!arm64 dragonfly freebsd js,wasm linux nacl netbsd openbsd solaris
 
 package os
 
@@ -12,37 +12,19 @@ import (
 	"syscall"
 )
 
+// Auxiliary information if the File describes a directory
+type dirInfo struct {
+	buf  []byte // buffer for directory I/O
+	nbuf int    // length of buf; return value from Getdirentries
+	bufp int    // location of next record in buf.
+}
+
 const (
 	// More than 5760 to work around https://golang.org/issue/24015.
 	blockSize = 8192
 )
 
-func (f *File) readdir(n int) (fi []FileInfo, err error) {
-	dirname := f.name
-	if dirname == "" {
-		dirname = "."
-	}
-	names, err := f.Readdirnames(n)
-	fi = make([]FileInfo, 0, len(names))
-	for _, filename := range names {
-		fip, lerr := lstat(dirname + "/" + filename)
-		if IsNotExist(lerr) {
-			// File disappeared between readdir + stat.
-			// Just treat it as if it didn't exist.
-			continue
-		}
-		if lerr != nil {
-			return fi, lerr
-		}
-		fi = append(fi, fip)
-	}
-	if len(fi) == 0 && err == nil && n > 0 {
-		// Per File.Readdir, the slice must be non-empty or err
-		// must be non-nil if n > 0.
-		err = io.EOF
-	}
-	return fi, err
-}
+func (d *dirInfo) close() {}
 
 func (f *File) readdirnames(n int) (names []string, err error) {
 	// If this file has no dirinfo, create one.

src/os/file_unix.go

@@ -9,6 +9,7 @@ package os
 import (
 	"internal/poll"
 	"internal/syscall/unix"
+	"io"
 	"runtime"
 	"syscall"
 )
@@ -155,13 +156,6 @@ func newFile(fd uintptr, name string, kind newFileKind) *File {
 	return f
 }
 
-// Auxiliary information if the File describes a directory
-type dirInfo struct {
-	buf  []byte // buffer for directory I/O
-	nbuf int    // length of buf; return value from Getdirentries
-	bufp int    // location of next record in buf.
-}
-
 // epipecheck raises SIGPIPE if we get an EPIPE error on standard
 // output or standard error. See the SIGPIPE docs in os/signal, and
 // issue 11845.
@@ -230,6 +224,9 @@ func (file *file) close() error {
 	if file == nil {
 		return syscall.EINVAL
 	}
+	if file.dirinfo != nil {
+		file.dirinfo.close()
+	}
 	var err error
 	if e := file.pfd.Close(); e != nil {
 		if e == poll.ErrFileClosing {
@@ -358,3 +355,30 @@ func Symlink(oldname, newname string) error {
 	}
 	return nil
 }
+
+func (f *File) readdir(n int) (fi []FileInfo, err error) {
+	dirname := f.name
+	if dirname == "" {
+		dirname = "."
+	}
+	names, err := f.Readdirnames(n)
+	fi = make([]FileInfo, 0, len(names))
+	for _, filename := range names {
+		fip, lerr := lstat(dirname + "/" + filename)
+		if IsNotExist(lerr) {
+			// File disappeared between readdir + stat.
+			// Just treat it as if it didn't exist.
+			continue
+		}
+		if lerr != nil {
+			return fi, lerr
+		}
+		fi = append(fi, fip)
+	}
+	if len(fi) == 0 && err == nil && n > 0 {
+		// Per File.Readdir, the slice must be non-empty or err
+		// must be non-nil if n > 0.
+		err = io.EOF
+	}
+	return fi, err
+}

src/runtime/sys_darwin_32.go

@@ -19,3 +19,14 @@ func syscall_syscall9(fn, a1, a2, a3, a4, a5, a6, a7, a8, a9 uintptr) (r1, r2, e
 	return
 }
 func syscall9()
+
+//go:linkname syscall_syscallPtr syscall.syscallPtr
+//go:nosplit
+//go:cgo_unsafe_args
+func syscall_syscallPtr(fn, a1, a2, a3 uintptr) (r1, r2, err uintptr) {
+	entersyscallblock()
+	libcCall(unsafe.Pointer(funcPC(syscallPtr)), unsafe.Pointer(&fn))
+	exitsyscall()
+	return
+}
+func syscallPtr()

src/runtime/sys_darwin_386.s

@@ -675,6 +675,11 @@ ok:
 	POPL	BP
 	RET
 
+// Not used on 386.
+TEXT runtime·syscallPtr(SB),NOSPLIT,$0
+	MOVL	$0xf1, 0xf1  // crash
+	RET
+
 // syscall6 calls a function in libc on behalf of the syscall package.
 // syscall6 takes a pointer to a struct like:
 // struct {

src/runtime/sys_darwin_64.go

@@ -19,3 +19,14 @@ func syscall_syscallX(fn, a1, a2, a3 uintptr) (r1, r2, err uintptr) {
 	return
 }
 func syscallX()
+
+//go:linkname syscall_syscallXPtr syscall.syscallXPtr
+//go:nosplit
+//go:cgo_unsafe_args
+func syscall_syscallXPtr(fn, a1, a2, a3 uintptr) (r1, r2, err uintptr) {
+	entersyscallblock()
+	libcCall(unsafe.Pointer(funcPC(syscallXPtr)), unsafe.Pointer(&fn))
+	exitsyscall()
+	return
+}
+func syscallXPtr()

src/runtime/sys_darwin_amd64.s

@@ -637,6 +637,11 @@ ok:
 	POPQ	BP
 	RET
 
+// Not used on amd64.
+TEXT runtime·syscallXPtr(SB),NOSPLIT,$0
+	MOVL	$0xf1, 0xf1  // crash
+	RET
+
 // syscall6 calls a function in libc on behalf of the syscall package.
 // syscall6 takes a pointer to a struct like:
 // struct {

src/runtime/sys_darwin_arm.s

@@ -417,6 +417,29 @@ TEXT runtime·syscall(SB),NOSPLIT,$0
 ok:
 	RET
 
+// syscallPtr is like syscall except the libc function reports an
+// error by returning NULL.
+TEXT runtime·syscallPtr(SB),NOSPLIT,$0
+	MOVW.W	R0, -4(R13)	// push structure pointer
+	MOVW	0(R0), R12	// fn
+	MOVW	8(R0), R1	// a2
+	MOVW	12(R0), R2	// a3
+	MOVW	4(R0), R0	// a1
+	BL	(R12)
+	MOVW.P	4(R13), R2	// pop structure pointer
+	MOVW	R0, 16(R2)	// save r1
+	MOVW	R1, 20(R2)	// save r2
+	MOVW	$0, R3
+	CMP	R0, R3
+	BNE	ok
+	MOVW.W	R2, -4(R13)	// push structure pointer
+	BL	libc_error(SB)
+	MOVW	(R0), R0
+	MOVW.P	4(R13), R2	// pop structure pointer
+	MOVW	R0, 24(R2)	// save err
+ok:
+	RET
+
 // syscall6 calls a function in libc on behalf of the syscall package.
 // syscall6 takes a pointer to a struct like:
 // struct {

src/runtime/sys_darwin_arm64.s

@@ -465,6 +465,34 @@ TEXT runtime·syscallX(SB),NOSPLIT,$0
 ok:
 	RET
 
+// syscallXPtr is like syscallX except that the libc function reports an
+// error by returning NULL.
+TEXT runtime·syscallXPtr(SB),NOSPLIT,$0
+	SUB	$16, RSP	// push structure pointer
+	MOVD	R0, (RSP)
+
+	MOVD	0(R0), R12	// fn
+	MOVD	16(R0), R1	// a2
+	MOVD	24(R0), R2	// a3
+	MOVD	8(R0), R0	// a1
+	BL	(R12)
+
+	MOVD	(RSP), R2	// pop structure pointer
+	ADD	$16, RSP
+	MOVD	R0, 32(R2)	// save r1
+	MOVD	R1, 40(R2)	// save r2
+	CMP	$0, R0
+	BNE	ok
+	SUB	$16, RSP	// push structure pointer
+	MOVD	R2, (RSP)
+	BL	libc_error(SB)
+	MOVW	(R0), R0
+	MOVD	(RSP), R2	// pop structure pointer
+	ADD	$16, RSP
+	MOVD	R0, 48(R2)	// save err
+ok:
+	RET
+
 // syscall6 calls a function in libc on behalf of the syscall package.
 // syscall6 takes a pointer to a struct like:
 // struct {

src/syscall/dirent_bsd_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin dragonfly freebsd netbsd openbsd
+// +build darwin,!arm,!arm64 dragonfly freebsd netbsd openbsd
 
 package syscall_test
 

src/syscall/syscall_darwin.go

@@ -270,7 +270,6 @@ func Kill(pid int, signum Signal) (err error) { return kill(pid, int(signum), 1)
 //sys	Fsync(fd int) (err error)
 //  Fsync is not called for os.File.Sync(). Please see internal/poll/fd_fsync_darwin.go
 //sys	Ftruncate(fd int, length int64) (err error)
-//sys	Getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error) = SYS___getdirentries64
 //sys	Getdtablesize() (size int)
 //sysnb	Getegid() (egid int)
 //sysnb	Geteuid() (uid int)

src/syscall/syscall_darwin_386.go

@@ -16,6 +16,7 @@ func setTimeval(sec, usec int64) Timeval {
 
 //sys	Fstat(fd int, stat *Stat_t) (err error) = SYS_fstat64
 //sys	Fstatfs(fd int, stat *Statfs_t) (err error) = SYS_fstatfs64
+//sys	Getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error) = SYS___getdirentries64
 //sysnb	Gettimeofday(tp *Timeval) (err error)
 //sys	Lstat(path string, stat *Stat_t) (err error) = SYS_lstat64
 //sys	Stat(path string, stat *Stat_t) (err error) = SYS_stat64

src/syscall/syscall_darwin_amd64.go

@@ -16,6 +16,7 @@ func setTimeval(sec, usec int64) Timeval {
 
 //sys	Fstat(fd int, stat *Stat_t) (err error) = SYS_fstat64
 //sys	Fstatfs(fd int, stat *Statfs_t) (err error) = SYS_fstatfs64
+//sys	Getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error) = SYS___getdirentries64
 //sysnb	Gettimeofday(tp *Timeval) (err error)
 //sys	Lstat(path string, stat *Stat_t) (err error) = SYS_lstat64
 //sys	Stat(path string, stat *Stat_t) (err error) = SYS_stat64