From 471b15b212831af31c2fe36cd42cea7ec7b7785b Mon Sep 17 00:00:00 2001
From: Jamie Liu <jamieliu@google.com>
Date: Tue, 25 Feb 2020 13:25:36 -0800
Subject: 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
---
 pkg/sentry/syscalls/linux/vfs2/fd.go | 147 +++++++++++++++++++++++++++++++++++
 1 file changed, 147 insertions(+)
 create mode 100644 pkg/sentry/syscalls/linux/vfs2/fd.go

(limited to 'pkg/sentry/syscalls/linux/vfs2/fd.go')

diff --git a/pkg/sentry/syscalls/linux/vfs2/fd.go b/pkg/sentry/syscalls/linux/vfs2/fd.go
new file mode 100644
index 000000000..3afcea665
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/vfs2/fd.go
@@ -0,0 +1,147 @@
+// 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/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	slinux "gvisor.dev/gvisor/pkg/sentry/syscalls/linux"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+// Close implements Linux syscall close(2).
+func Close(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+
+	// Note that Remove provides a reference on the file that we may use to
+	// flush. It is still active until we drop the final reference below
+	// (and other reference-holding operations complete).
+	_, file := t.FDTable().Remove(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	err := file.OnClose(t)
+	return 0, nil, slinux.HandleIOErrorVFS2(t, false /* partial */, err, syserror.EINTR, "close", file)
+}
+
+// Dup implements Linux syscall dup(2).
+func Dup(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	newFD, err := t.NewFDFromVFS2(0, file, kernel.FDFlags{})
+	if err != nil {
+		return 0, nil, syserror.EMFILE
+	}
+	return uintptr(newFD), nil, nil
+}
+
+// Dup2 implements Linux syscall dup2(2).
+func Dup2(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	oldfd := args[0].Int()
+	newfd := args[1].Int()
+
+	if oldfd == newfd {
+		// As long as oldfd is valid, dup2() does nothing and returns newfd.
+		file := t.GetFileVFS2(oldfd)
+		if file == nil {
+			return 0, nil, syserror.EBADF
+		}
+		file.DecRef()
+		return uintptr(newfd), nil, nil
+	}
+
+	return dup3(t, oldfd, newfd, 0)
+}
+
+// Dup3 implements Linux syscall dup3(2).
+func Dup3(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	oldfd := args[0].Int()
+	newfd := args[1].Int()
+	flags := args[2].Uint()
+
+	if oldfd == newfd {
+		return 0, nil, syserror.EINVAL
+	}
+
+	return dup3(t, oldfd, newfd, flags)
+}
+
+func dup3(t *kernel.Task, oldfd, newfd int32, flags uint32) (uintptr, *kernel.SyscallControl, error) {
+	if flags&^linux.O_CLOEXEC != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	file := t.GetFileVFS2(oldfd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	err := t.NewFDAtVFS2(newfd, file, kernel.FDFlags{
+		CloseOnExec: flags&linux.O_CLOEXEC != 0,
+	})
+	if err != nil {
+		return 0, nil, err
+	}
+	return uintptr(newfd), nil, nil
+}
+
+// Fcntl implements linux syscall fcntl(2).
+func Fcntl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	cmd := args[1].Int()
+
+	file, flags := t.FDTable().GetVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	switch cmd {
+	case linux.F_DUPFD, linux.F_DUPFD_CLOEXEC:
+		minfd := args[2].Int()
+		fd, err := t.NewFDFromVFS2(minfd, file, kernel.FDFlags{
+			CloseOnExec: cmd == linux.F_DUPFD_CLOEXEC,
+		})
+		if err != nil {
+			return 0, nil, err
+		}
+		return uintptr(fd), nil, nil
+	case linux.F_GETFD:
+		return uintptr(flags.ToLinuxFDFlags()), nil, nil
+	case linux.F_SETFD:
+		flags := args[2].Uint()
+		t.FDTable().SetFlags(fd, kernel.FDFlags{
+			CloseOnExec: flags&linux.FD_CLOEXEC != 0,
+		})
+		return 0, nil, nil
+	case linux.F_GETFL:
+		return uintptr(file.StatusFlags()), nil, nil
+	case linux.F_SETFL:
+		return 0, nil, file.SetStatusFlags(t, t.Credentials(), args[2].Uint())
+	default:
+		// TODO(gvisor.dev/issue/1623): Everything else is not yet supported.
+		return 0, nil, syserror.EINVAL
+	}
+}
-- 
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