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, 149 insertions, 0 deletions

diff --git a/pkg/sentry/syscalls/linux/vfs2/getdents.go b/pkg/sentry/syscalls/linux/vfs2/getdents.go
new file mode 100644
index 000000000..ddc140b65
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/vfs2/getdents.go
@@ -0,0 +1,149 @@
+// 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 (
+	"fmt"
+
+	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sync"
+	"gvisor.dev/gvisor/pkg/syserror"
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+// Getdents implements Linux syscall getdents(2).
+func Getdents(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	return getdents(t, args, false /* isGetdents64 */)
+}
+
+// Getdents64 implements Linux syscall getdents64(2).
+func Getdents64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	return getdents(t, args, true /* isGetdents64 */)
+}
+
+func getdents(t *kernel.Task, args arch.SyscallArguments, isGetdents64 bool) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	addr := args[1].Pointer()
+	size := int(args[2].Uint())
+
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	cb := getGetdentsCallback(t, addr, size, isGetdents64)
+	err := file.IterDirents(t, cb)
+	n := size - cb.remaining
+	putGetdentsCallback(cb)
+	if n == 0 {
+		return 0, nil, err
+	}
+	return uintptr(n), nil, nil
+}
+
+type getdentsCallback struct {
+	t            *kernel.Task
+	addr         usermem.Addr
+	remaining    int
+	isGetdents64 bool
+}
+
+var getdentsCallbackPool = sync.Pool{
+	New: func() interface{} {
+		return &getdentsCallback{}
+	},
+}
+
+func getGetdentsCallback(t *kernel.Task, addr usermem.Addr, size int, isGetdents64 bool) *getdentsCallback {
+	cb := getdentsCallbackPool.Get().(*getdentsCallback)
+	*cb = getdentsCallback{
+		t:            t,
+		addr:         addr,
+		remaining:    size,
+		isGetdents64: isGetdents64,
+	}
+	return cb
+}
+
+func putGetdentsCallback(cb *getdentsCallback) {
+	cb.t = nil
+	getdentsCallbackPool.Put(cb)
+}
+
+// Handle implements vfs.IterDirentsCallback.Handle.
+func (cb *getdentsCallback) Handle(dirent vfs.Dirent) error {
+	var buf []byte
+	if cb.isGetdents64 {
+		// struct linux_dirent64 {
+		//     ino64_t        d_ino;    /* 64-bit inode number */
+		//     off64_t        d_off;    /* 64-bit offset to next structure */
+		//     unsigned short d_reclen; /* Size of this dirent */
+		//     unsigned char  d_type;   /* File type */
+		//     char           d_name[]; /* Filename (null-terminated) */
+		// };
+		size := 8 + 8 + 2 + 1 + 1 + len(dirent.Name)
+		if size < cb.remaining {
+			return syserror.EINVAL
+		}
+		buf = cb.t.CopyScratchBuffer(size)
+		usermem.ByteOrder.PutUint64(buf[0:8], dirent.Ino)
+		usermem.ByteOrder.PutUint64(buf[8:16], uint64(dirent.NextOff))
+		usermem.ByteOrder.PutUint16(buf[16:18], uint16(size))
+		buf[18] = dirent.Type
+		copy(buf[19:], dirent.Name)
+		buf[size-1] = 0 // NUL terminator
+	} else {
+		// struct linux_dirent {
+		//     unsigned long  d_ino;     /* Inode number */
+		//     unsigned long  d_off;     /* Offset to next linux_dirent */
+		//     unsigned short d_reclen;  /* Length of this linux_dirent */
+		//     char           d_name[];  /* Filename (null-terminated) */
+		//                       /* length is actually (d_reclen - 2 -
+		//                          offsetof(struct linux_dirent, d_name)) */
+		//     /*
+		//     char           pad;       // Zero padding byte
+		//     char           d_type;    // File type (only since Linux
+		//                               // 2.6.4); offset is (d_reclen - 1)
+		//     */
+		// };
+		if cb.t.Arch().Width() != 8 {
+			panic(fmt.Sprintf("unsupported sizeof(unsigned long): %d", cb.t.Arch().Width()))
+		}
+		size := 8 + 8 + 2 + 1 + 1 + 1 + len(dirent.Name)
+		if size < cb.remaining {
+			return syserror.EINVAL
+		}
+		buf = cb.t.CopyScratchBuffer(size)
+		usermem.ByteOrder.PutUint64(buf[0:8], dirent.Ino)
+		usermem.ByteOrder.PutUint64(buf[8:16], uint64(dirent.NextOff))
+		usermem.ByteOrder.PutUint16(buf[16:18], uint16(size))
+		copy(buf[18:], dirent.Name)
+		buf[size-3] = 0 // NUL terminator
+		buf[size-2] = 0 // zero padding byte
+		buf[size-1] = dirent.Type
+	}
+	n, err := cb.t.CopyOutBytes(cb.addr, buf)
+	if err != nil {
+		// Don't report partially-written dirents by advancing cb.addr or
+		// cb.remaining.
+		return err
+	}
+	cb.addr += usermem.Addr(n)
+	cb.remaining -= n
+	return nil
+}