Create pkg/system and move stuff there from archive

This is a package for generic system calls etc that for some reason
is not yet supported by "syscall", or where it is different enough
for the different ports to need portability wrappers.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)

system/stat_linux.go

@@ -0,0 +1,13 @@
+package system
+
+import (
+	"syscall"
+)
+
+func GetLastAccess(stat *syscall.Stat_t) syscall.Timespec {
+	return stat.Atim
+}
+
+func GetLastModification(stat *syscall.Stat_t) syscall.Timespec {
+	return stat.Mtim
+}

system/stat_unsupported.go

@@ -0,0 +1,13 @@
+// +build !linux
+
+package system
+
+import "syscall"
+
+func GetLastAccess(stat *syscall.Stat_t) syscall.Timespec {
+	return stat.Atimespec
+}
+
+func GetLastModification(stat *syscall.Stat_t) syscall.Timespec {
+	return stat.Mtimespec
+}

system/utimes_linux.go

@@ -0,0 +1,31 @@
+package system
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+func LUtimesNano(path string, ts []syscall.Timespec) error {
+	// These are not currently available in syscall
+	AT_FDCWD := -100
+	AT_SYMLINK_NOFOLLOW := 0x100
+
+	var _path *byte
+	_path, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return err
+	}
+
+	if _, _, err := syscall.Syscall6(syscall.SYS_UTIMENSAT, uintptr(AT_FDCWD), uintptr(unsafe.Pointer(_path)), uintptr(unsafe.Pointer(&ts[0])), uintptr(AT_SYMLINK_NOFOLLOW), 0, 0); err != 0 && err != syscall.ENOSYS {
+		return err
+	}
+
+	return nil
+}
+
+func UtimesNano(path string, ts []syscall.Timespec) error {
+	if err := syscall.UtimesNano(path, ts); err != nil {
+		return err
+	}
+	return nil
+}

system/utimes_unsupported.go

@@ -0,0 +1,13 @@
+// +build !linux
+
+package system
+
+import "syscall"
+
+func LUtimesNano(path string, ts []syscall.Timespec) error {
+	return ErrNotSupportedPlatform
+}
+
+func UtimesNano(path string, ts []syscall.Timespec) error {
+	return ErrNotSupportedPlatform
+}

system/xattrs_linux.go

@@ -0,0 +1,59 @@
+package system
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+// Returns a nil slice and nil error if the xattr is not set
+func Lgetxattr(path string, attr string) ([]byte, error) {
+	pathBytes, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return nil, err
+	}
+	attrBytes, err := syscall.BytePtrFromString(attr)
+	if err != nil {
+		return nil, err
+	}
+
+	dest := make([]byte, 128)
+	destBytes := unsafe.Pointer(&dest[0])
+	sz, _, errno := syscall.Syscall6(syscall.SYS_LGETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(destBytes), uintptr(len(dest)), 0, 0)
+	if errno == syscall.ENODATA {
+		return nil, nil
+	}
+	if errno == syscall.ERANGE {
+		dest = make([]byte, sz)
+		destBytes := unsafe.Pointer(&dest[0])
+		sz, _, errno = syscall.Syscall6(syscall.SYS_LGETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(destBytes), uintptr(len(dest)), 0, 0)
+	}
+	if errno != 0 {
+		return nil, errno
+	}
+
+	return dest[:sz], nil
+}
+
+var _zero uintptr
+
+func Lsetxattr(path string, attr string, data []byte, flags int) error {
+	pathBytes, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return err
+	}
+	attrBytes, err := syscall.BytePtrFromString(attr)
+	if err != nil {
+		return err
+	}
+	var dataBytes unsafe.Pointer
+	if len(data) > 0 {
+		dataBytes = unsafe.Pointer(&data[0])
+	} else {
+		dataBytes = unsafe.Pointer(&_zero)
+	}
+	_, _, errno := syscall.Syscall6(syscall.SYS_LSETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(dataBytes), uintptr(len(data)), uintptr(flags), 0)
+	if errno != 0 {
+		return errno
+	}
+	return nil
+}

system/xattrs_unsupported.go

@@ -0,0 +1,11 @@
+// +build !linux
+
+package system
+
+func Lgetxattr(path string, attr string) ([]byte, error) {
+	return nil, ErrNotSupportedPlatform
+}
+
+func Lsetxattr(path string, attr string, data []byte, flags int) error {
+	return ErrNotSupportedPlatform
+}