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Replace manual pty copies to/from userspace with safemem operations.

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Also, changing queue.writeBuf from a buffer.Bytes to a [][]byte should reduce
copying and reallocating of slices.

PiperOrigin-RevId: 239713547
Change-Id: I6ee5ff19c3ee2662f1af5749cae7b73db0569e96
This commit is contained in:
Kevin Krakauer
2019-03-21 18:05:07 -07:00
committed by Shentubot
parent ba828233b9
commit 0cd5f20044
3 changed files with 123 additions and 78 deletions
Download Patch File Download Diff File Expand all files Collapse all files
pkg/sentry/fs/tty/BUILD
+1
View File
@@ -24,6 +24,7 @@ go_library(
"//pkg/sentry/fs",
"//pkg/sentry/fs/fsutil",
"//pkg/sentry/kernel/auth",
"//pkg/sentry/safemem",
"//pkg/sentry/socket/unix/transport",
"//pkg/sentry/unimpl",
"//pkg/sentry/usermem",
pkg/sentry/fs/tty/line_discipline.go
+26 -20
View File
@@ -140,9 +140,9 @@ func (l *lineDiscipline) setTermios(ctx context.Context, io usermem.IO, args arc
// buffer to its read buffer. Anything already in the read buffer is
// now readable.
if oldCanonEnabled && !l.termios.LEnabled(linux.ICANON) {
if n := l.inQueue.pushWaitBuf(l); n > 0 {
l.slaveWaiter.Notify(waiter.EventIn)
}
l.inQueue.pushWaitBuf(l)
l.inQueue.readable = true
l.slaveWaiter.Notify(waiter.EventIn)
}
return 0, err
@@ -263,7 +263,7 @@ type outputQueueTransformer struct{}
// transform does output processing for one end of the pty. See
// drivers/tty/n_tty.c:do_output_char for an analogous kernel function.
//
// Precondition:
// Preconditions:
// * l.termiosMu must be held for reading.
// * q.mu must be held.
func (*outputQueueTransformer) transform(l *lineDiscipline, q *queue, buf []byte) int {
@@ -271,11 +271,11 @@ func (*outputQueueTransformer) transform(l *lineDiscipline, q *queue, buf []byte
// master termios never has ICANON set.
if !l.termios.OEnabled(linux.OPOST) {
n, _ := q.readBuf.Write(buf)
if q.readBuf.Len() > 0 {
q.readBuf = append(q.readBuf, buf...)
if len(q.readBuf) > 0 {
q.readable = true
}
return n
return len(buf)
}
var ret int
@@ -289,7 +289,7 @@ func (*outputQueueTransformer) transform(l *lineDiscipline, q *queue, buf []byte
l.column = 0
}
if l.termios.OEnabled(linux.ONLCR) {
q.readBuf.Write([]byte{'\r', '\n'})
q.readBuf = append(q.readBuf, '\r', '\n')
continue
}
case '\r':
@@ -308,7 +308,7 @@ func (*outputQueueTransformer) transform(l *lineDiscipline, q *queue, buf []byte
spaces := spacesPerTab - l.column%spacesPerTab
if l.termios.OutputFlags&linux.TABDLY == linux.XTABS {
l.column += spaces
q.readBuf.Write(bytes.Repeat([]byte{' '}, spacesPerTab))
q.readBuf = append(q.readBuf, bytes.Repeat([]byte{' '}, spacesPerTab)...)
continue
}
l.column += spaces
@@ -319,9 +319,12 @@ func (*outputQueueTransformer) transform(l *lineDiscipline, q *queue, buf []byte
default:
l.column++
}
q.readBuf.WriteRune(c)
// The compiler optimizes this by growing readBuf without
// creating the intermediate slice.
q.readBuf = append(q.readBuf, make([]byte, size)...)
utf8.EncodeRune(q.readBuf[len(q.readBuf)-size:], c)
}
if q.readBuf.Len() > 0 {
if len(q.readBuf) > 0 {
q.readable = true
}
return ret
@@ -338,7 +341,7 @@ type inputQueueTransformer struct{}
// drivers/tty/n_tty.c:n_tty_receive_char_special for an analogous kernel
// function.
//
// Precondition:
// Preconditions:
// * l.termiosMu must be held for reading.
// * q.mu must be held.
func (*inputQueueTransformer) transform(l *lineDiscipline, q *queue, buf []byte) int {
@@ -354,7 +357,7 @@ func (*inputQueueTransformer) transform(l *lineDiscipline, q *queue, buf []byte)
}
var ret int
for len(buf) > 0 && q.readBuf.Len() < canonMaxBytes {
for len(buf) > 0 && len(q.readBuf) < canonMaxBytes {
c, size := l.peekRune(buf)
switch c {
case '\r':
@@ -381,7 +384,7 @@ func (*inputQueueTransformer) transform(l *lineDiscipline, q *queue, buf []byte)
}
// Stop if the buffer would be overfilled.
if q.readBuf.Len()+size > maxBytes {
if len(q.readBuf)+size > maxBytes {
break
}
cBytes := buf[:size]
@@ -394,12 +397,15 @@ func (*inputQueueTransformer) transform(l *lineDiscipline, q *queue, buf []byte)
break
}
q.readBuf.WriteRune(c)
// The compiler optimizes this by growing readBuf without
// creating the intermediate slice.
q.readBuf = append(q.readBuf, make([]byte, size)...)
utf8.EncodeRune(q.readBuf[len(q.readBuf)-size:], c)
// Anything written to the readBuf will have to be echoed.
if l.termios.LEnabled(linux.ECHO) {
if l.outQueue.writeBytes(cBytes, l) > 0 {
l.masterWaiter.Notify(waiter.EventIn)
}
l.outQueue.writeBytes(cBytes, l)
l.masterWaiter.Notify(waiter.EventIn)
}
// If we finish a line, make it available for reading.
@@ -410,7 +416,7 @@ func (*inputQueueTransformer) transform(l *lineDiscipline, q *queue, buf []byte)
}
// In noncanonical mode, everything is readable.
if !l.termios.LEnabled(linux.ICANON) && q.readBuf.Len() > 0 {
if !l.termios.LEnabled(linux.ICANON) && len(q.readBuf) > 0 {
q.readable = true
}
@@ -425,7 +431,7 @@ func (*inputQueueTransformer) transform(l *lineDiscipline, q *queue, buf []byte)
// * l.termiosMu must be held for reading.
// * q.mu must be held.
func (l *lineDiscipline) shouldDiscard(q *queue, c rune) bool {
return l.termios.LEnabled(linux.ICANON) && q.readBuf.Len()+utf8.RuneLen(c) >= canonMaxBytes && !l.termios.IsTerminating(c)
return l.termios.LEnabled(linux.ICANON) && len(q.readBuf)+utf8.RuneLen(c) >= canonMaxBytes && !l.termios.IsTerminating(c)
}
// peekRune returns the first rune from the byte array depending on whether
pkg/sentry/fs/tty/queue.go
+96 -58
View File
@@ -15,17 +15,21 @@
package tty
import (
"bytes"
"sync"
"gvisor.googlesource.com/gvisor/pkg/abi/linux"
"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
"gvisor.googlesource.com/gvisor/pkg/sentry/context"
"gvisor.googlesource.com/gvisor/pkg/sentry/safemem"
"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
"gvisor.googlesource.com/gvisor/pkg/syserror"
"gvisor.googlesource.com/gvisor/pkg/waiter"
)
// waitBufMaxBytes is the maximum size of a wait buffer. It is based on
// TTYB_DEFAULT_MEM_LIMIT.
const waitBufMaxBytes = 131072
// queue represents one of the input or output queues between a pty master and
// slave. Bytes written to a queue are added to the read buffer until it is
// full, at which point they are written to the wait buffer. Bytes are
@@ -40,12 +44,13 @@ type queue struct {
// readBuf is buffer of data ready to be read when readable is true.
// This data has been processed.
readBuf bytes.Buffer `state:".([]byte)"`
readBuf []byte
// waitBuf contains data that can't fit into readBuf. It is put here
// until it can be loaded into the read buffer. waitBuf contains data
// that hasn't been processed.
waitBuf bytes.Buffer `state:".([]byte)"`
waitBuf [][]byte
waitBufLen uint64
// readable indicates whether the read buffer can be read from. In
// canonical mode, there can be an unterminated line in the read buffer,
@@ -58,31 +63,54 @@ type queue struct {
transformer
}
// saveReadBuf is invoked by stateify.
func (q *queue) saveReadBuf() []byte {
return append([]byte(nil), q.readBuf.Bytes()...)
// ReadToBlocks implements safemem.Reader.ReadToBlocks.
func (q *queue) ReadToBlocks(dst safemem.BlockSeq) (uint64, error) {
src := safemem.BlockSeqOf(safemem.BlockFromSafeSlice(q.readBuf))
n, err := safemem.CopySeq(dst, src)
if err != nil {
return 0, err
}
q.readBuf = q.readBuf[n:]
// If we read everything, this queue is no longer readable.
if len(q.readBuf) == 0 {
q.readable = false
}
return n, nil
}
// loadReadBuf is invoked by stateify.
func (q *queue) loadReadBuf(b []byte) {
q.readBuf.Write(b)
}
// WriteFromBlocks implements safemem.Writer.WriteFromBlocks.
func (q *queue) WriteFromBlocks(src safemem.BlockSeq) (uint64, error) {
copyLen := src.NumBytes()
room := waitBufMaxBytes - q.waitBufLen
// If out of room, return EAGAIN.
if room == 0 && copyLen > 0 {
return 0, syserror.ErrWouldBlock
}
// Cap the size of the wait buffer.
if copyLen > room {
copyLen = room
src = src.TakeFirst64(room)
}
buf := make([]byte, copyLen)
// saveWaitBuf is invoked by stateify.
func (q *queue) saveWaitBuf() []byte {
return append([]byte(nil), q.waitBuf.Bytes()...)
}
// Copy the data into the wait buffer.
dst := safemem.BlockSeqOf(safemem.BlockFromSafeSlice(buf))
n, err := safemem.CopySeq(dst, src)
if err != nil {
return 0, err
}
q.waitBufAppend(buf)
// loadWaitBuf is invoked by stateify.
func (q *queue) loadWaitBuf(b []byte) {
q.waitBuf.Write(b)
return n, nil
}
// readReadiness returns whether q is ready to be read from.
func (q *queue) readReadiness(t *linux.KernelTermios) waiter.EventMask {
q.mu.Lock()
defer q.mu.Unlock()
if q.readBuf.Len() > 0 && q.readable {
if len(q.readBuf) > 0 && q.readable {
return waiter.EventIn
}
return waiter.EventMask(0)
@@ -90,8 +118,10 @@ func (q *queue) readReadiness(t *linux.KernelTermios) waiter.EventMask {
// writeReadiness returns whether q is ready to be written to.
func (q *queue) writeReadiness(t *linux.KernelTermios) waiter.EventMask {
// Like Linux, we don't impose a maximum size on what can be enqueued.
return waiter.EventOut
if q.waitBufLen < waitBufMaxBytes {
return waiter.EventOut
}
return waiter.EventMask(0)
}
// readableSize writes the number of readable bytes to userspace.
@@ -100,7 +130,7 @@ func (q *queue) readableSize(ctx context.Context, io usermem.IO, args arch.Sysca
defer q.mu.Unlock()
var size int32
if q.readable {
size = int32(q.readBuf.Len())
size = int32(len(q.readBuf))
}
_, err := usermem.CopyObjectOut(ctx, io, args[2].Pointer(), size, usermem.IOOpts{
@@ -119,29 +149,19 @@ func (q *queue) readableSize(ctx context.Context, io usermem.IO, args arch.Sysca
func (q *queue) read(ctx context.Context, dst usermem.IOSequence, l *lineDiscipline) (int64, bool, error) {
q.mu.Lock()
defer q.mu.Unlock()
if !q.readable {
return 0, false, syserror.ErrWouldBlock
}
// Read out from the read buffer.
n := canonMaxBytes
if n > int(dst.NumBytes()) {
n = int(dst.NumBytes())
if dst.NumBytes() > canonMaxBytes {
dst = dst.TakeFirst(canonMaxBytes)
}
if n > q.readBuf.Len() {
n = q.readBuf.Len()
}
n, err := dst.Writer(ctx).Write(q.readBuf.Bytes()[:n])
n, err := dst.CopyOutFrom(ctx, q)
if err != nil {
return 0, false, err
}
// Discard bytes read out.
q.readBuf.Next(n)
// If we read everything, this queue is no longer readable.
if q.readBuf.Len() == 0 {
q.readable = false
}
// Move data from the queue's wait buffer to its read buffer.
nPushed := q.pushWaitBufLocked(l)
@@ -154,37 +174,32 @@ func (q *queue) read(ctx context.Context, dst usermem.IOSequence, l *lineDiscipl
// Preconditions:
// * l.termiosMu must be held for reading.
func (q *queue) write(ctx context.Context, src usermem.IOSequence, l *lineDiscipline) (int64, error) {
// TODO: Use CopyInTo/safemem to avoid extra copying.
// Copy in the bytes to write from user-space.
b := make([]byte, src.NumBytes())
n, err := src.CopyIn(ctx, b)
q.mu.Lock()
defer q.mu.Unlock()
// Copy data into the wait buffer.
n, err := src.CopyInTo(ctx, q)
if err != nil {
return 0, err
}
b = b[:n]
// If state changed, notify any waiters. If we were unable to write
// anything, let the caller know we could block.
if c := q.writeBytes(b, l); c > 0 {
return c, nil
}
return 0, syserror.ErrWouldBlock
// Push data from the wait to the read buffer.
q.pushWaitBufLocked(l)
return n, nil
}
// writeBytes writes to q from b.
//
// Preconditions:
// * l.termiosMu must be held for reading.
func (q *queue) writeBytes(b []byte, l *lineDiscipline) int64 {
func (q *queue) writeBytes(b []byte, l *lineDiscipline) {
q.mu.Lock()
defer q.mu.Unlock()
// Write as much as possible to the read buffer.
n := q.transform(l, q, b)
// Write remaining data to the wait buffer.
nWaiting, _ := q.waitBuf.Write(b[n:])
return int64(n + nWaiting)
// Write to the wait buffer.
q.waitBufAppend(b)
q.pushWaitBufLocked(l)
}
// pushWaitBuf fills the queue's read buffer with data from the wait buffer.
@@ -201,9 +216,32 @@ func (q *queue) pushWaitBuf(l *lineDiscipline) int {
// * l.termiosMu must be held for reading.
// * q.mu must be locked.
func (q *queue) pushWaitBufLocked(l *lineDiscipline) int {
// Remove bytes from the wait buffer and move them to the read buffer.
n := q.transform(l, q, q.waitBuf.Bytes())
q.waitBuf.Next(n)
if q.waitBufLen == 0 {
return 0
}
return n
// Move data from the wait to the read buffer.
var total int
var i int
for i = 0; i < len(q.waitBuf); i++ {
n := q.transform(l, q, q.waitBuf[i])
total += n
if n != len(q.waitBuf[i]) {
// The read buffer filled up without consuming the
// entire buffer.
q.waitBuf[i] = q.waitBuf[i][n:]
break
}
}
// Update wait buffer based on consumed data.
q.waitBuf = q.waitBuf[i:]
q.waitBufLen -= uint64(total)
return total
}
func (q *queue) waitBufAppend(b []byte) {
q.waitBuf = append(q.waitBuf, b)
q.waitBufLen += uint64(len(b))
}