Port most syscalls to VFS2.

pipe and pipe2 aren't ported, pending a slight rework of pipe FDs for VFS2.
mount and umount2 aren't ported out of temporary laziness. access and faccessat
need additional FSImpl methods to implement properly, but are stubbed to
prevent googletest from CHECK-failing. Other syscalls require additional
plumbing.

Updates #1623

PiperOrigin-RevId: 297188448

1 files changed, 137 insertions, 0 deletions

diff --git a/pkg/sentry/syscalls/linux/vfs2/execve.go b/pkg/sentry/syscalls/linux/vfs2/execve.go
new file mode 100644
index 000000000..aef0078a8
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/vfs2/execve.go
@@ -0,0 +1,137 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package vfs2
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/fspath"
+	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/fsbridge"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/loader"
+	slinux "gvisor.dev/gvisor/pkg/sentry/syscalls/linux"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+// Execve implements linux syscall execve(2).
+func Execve(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	pathnameAddr := args[0].Pointer()
+	argvAddr := args[1].Pointer()
+	envvAddr := args[2].Pointer()
+	return execveat(t, linux.AT_FDCWD, pathnameAddr, argvAddr, envvAddr, 0 /* flags */)
+}
+
+// Execveat implements linux syscall execveat(2).
+func Execveat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	dirfd := args[0].Int()
+	pathnameAddr := args[1].Pointer()
+	argvAddr := args[2].Pointer()
+	envvAddr := args[3].Pointer()
+	flags := args[4].Int()
+	return execveat(t, dirfd, pathnameAddr, argvAddr, envvAddr, flags)
+}
+
+func execveat(t *kernel.Task, dirfd int32, pathnameAddr, argvAddr, envvAddr usermem.Addr, flags int32) (uintptr, *kernel.SyscallControl, error) {
+	if flags&^(linux.AT_EMPTY_PATH|linux.AT_SYMLINK_NOFOLLOW) != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	pathname, err := t.CopyInString(pathnameAddr, linux.PATH_MAX)
+	if err != nil {
+		return 0, nil, err
+	}
+	var argv, envv []string
+	if argvAddr != 0 {
+		var err error
+		argv, err = t.CopyInVector(argvAddr, slinux.ExecMaxElemSize, slinux.ExecMaxTotalSize)
+		if err != nil {
+			return 0, nil, err
+		}
+	}
+	if envvAddr != 0 {
+		var err error
+		envv, err = t.CopyInVector(envvAddr, slinux.ExecMaxElemSize, slinux.ExecMaxTotalSize)
+		if err != nil {
+			return 0, nil, err
+		}
+	}
+
+	root := t.FSContext().RootDirectoryVFS2()
+	defer root.DecRef()
+	var executable fsbridge.File
+	closeOnExec := false
+	if path := fspath.Parse(pathname); dirfd != linux.AT_FDCWD && !path.Absolute {
+		// We must open the executable ourselves since dirfd is used as the
+		// starting point while resolving path, but the task working directory
+		// is used as the starting point while resolving interpreters (Linux:
+		// fs/binfmt_script.c:load_script() => fs/exec.c:open_exec() =>
+		// do_open_execat(fd=AT_FDCWD)), and the loader package is currently
+		// incapable of handling this correctly.
+		if !path.HasComponents() && flags&linux.AT_EMPTY_PATH == 0 {
+			return 0, nil, syserror.ENOENT
+		}
+		dirfile, dirfileFlags := t.FDTable().GetVFS2(dirfd)
+		if dirfile == nil {
+			return 0, nil, syserror.EBADF
+		}
+		start := dirfile.VirtualDentry()
+		start.IncRef()
+		dirfile.DecRef()
+		closeOnExec = dirfileFlags.CloseOnExec
+		file, err := t.Kernel().VFS().OpenAt(t, t.Credentials(), &vfs.PathOperation{
+			Root:               root,
+			Start:              start,
+			Path:               path,
+			FollowFinalSymlink: flags&linux.AT_SYMLINK_NOFOLLOW == 0,
+		}, &vfs.OpenOptions{
+			Flags:    linux.O_RDONLY,
+			FileExec: true,
+		})
+		start.DecRef()
+		if err != nil {
+			return 0, nil, err
+		}
+		defer file.DecRef()
+		executable = fsbridge.NewVFSFile(file)
+	}
+
+	// Load the new TaskContext.
+	mntns := t.MountNamespaceVFS2() // FIXME(jamieliu): useless refcount change
+	defer mntns.DecRef()
+	wd := t.FSContext().WorkingDirectoryVFS2()
+	defer wd.DecRef()
+	remainingTraversals := uint(linux.MaxSymlinkTraversals)
+	loadArgs := loader.LoadArgs{
+		Opener:              fsbridge.NewVFSLookup(mntns, root, wd),
+		RemainingTraversals: &remainingTraversals,
+		ResolveFinal:        flags&linux.AT_SYMLINK_NOFOLLOW == 0,
+		Filename:            pathname,
+		File:                executable,
+		CloseOnExec:         closeOnExec,
+		Argv:                argv,
+		Envv:                envv,
+		Features:            t.Arch().FeatureSet(),
+	}
+
+	tc, se := t.Kernel().LoadTaskImage(t, loadArgs)
+	if se != nil {
+		return 0, nil, se.ToError()
+	}
+
+	ctrl, err := t.Execve(tc)
+	return 0, ctrl, err
+}