container/init: wrap syscall helper functions

This allows tests to stub all kernel behaviour, enabling measurement of all function call arguments and error injection.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/initsymlink_test.go

@@ -1,8 +1,54 @@
 package container
 
-import "testing"
+import (
+	"io/fs"
+	"os"
+	"testing"
+)
 
 func TestSymlinkOp(t *testing.T) {
+	checkOpBehaviour(t, []opBehaviourTestCase{
+		{"mkdir", &Params{ParentPerm: 0700}, &SymlinkOp{
+			Target:   MustAbs("/etc/nixos"),
+			LinkName: "/etc/static/nixos",
+		}, nil, nil, []kexpect{
+			{"mkdirAll", expectArgs{"/sysroot/etc", os.FileMode(0700)}, nil, errUnique},
+		}, wrapErrSelf(errUnique)},
+
+		{"abs", &Params{ParentPerm: 0755}, &SymlinkOp{
+			Target:      MustAbs("/etc/mtab"),
+			LinkName:    "etc/mtab",
+			Dereference: true,
+		}, nil, msg.WrapErr(fs.ErrInvalid, `path "etc/mtab" is not absolute`), nil, nil},
+
+		{"readlink", &Params{ParentPerm: 0755}, &SymlinkOp{
+			Target:      MustAbs("/etc/mtab"),
+			LinkName:    "/etc/mtab",
+			Dereference: true,
+		}, []kexpect{
+			{"readlink", expectArgs{"/etc/mtab"}, "/proc/mounts", errUnique},
+		}, wrapErrSelf(errUnique), nil, nil},
+
+		{"success noderef", &Params{ParentPerm: 0700}, &SymlinkOp{
+			Target:   MustAbs("/etc/nixos"),
+			LinkName: "/etc/static/nixos",
+		}, nil, nil, []kexpect{
+			{"mkdirAll", expectArgs{"/sysroot/etc", os.FileMode(0700)}, nil, nil},
+			{"symlink", expectArgs{"/etc/static/nixos", "/sysroot/etc/nixos"}, nil, nil},
+		}, nil},
+
+		{"success", &Params{ParentPerm: 0755}, &SymlinkOp{
+			Target:      MustAbs("/etc/mtab"),
+			LinkName:    "/etc/mtab",
+			Dereference: true,
+		}, []kexpect{
+			{"readlink", expectArgs{"/etc/mtab"}, "/proc/mounts", nil},
+		}, nil, []kexpect{
+			{"mkdirAll", expectArgs{"/sysroot/etc", os.FileMode(0755)}, nil, nil},
+			{"symlink", expectArgs{"/proc/mounts", "/sysroot/etc/mtab"}, nil, nil},
+		}, nil},
+	})
+
 	checkOpsValid(t, []opValidTestCase{
 		{"nil", (*SymlinkOp)(nil), false},
 		{"zero", new(SymlinkOp), false},