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-rw-r--r--pkg/abi/linux/tty.go28
-rw-r--r--pkg/sentry/fs/tty/line_discipline.go354
-rw-r--r--pkg/sentry/fs/tty/master.go3
-rw-r--r--pkg/sentry/fs/tty/slave.go3
4 files changed, 298 insertions, 90 deletions
diff --git a/pkg/abi/linux/tty.go b/pkg/abi/linux/tty.go
index f9e641af9..84b6ccc87 100644
--- a/pkg/abi/linux/tty.go
+++ b/pkg/abi/linux/tty.go
@@ -14,9 +14,16 @@
package linux
+import (
+ "unicode/utf8"
+)
+
const (
// NumControlCharacters is the number of control characters in Termios.
NumControlCharacters = 19
+ // disabledChar is used to indicate that a control character is
+ // disabled.
+ disabledChar = 0
)
// Termios is struct termios, defined in uapi/asm-generic/termbits.h.
@@ -86,6 +93,27 @@ func (t *KernelTermios) FromTermios(term Termios) {
t.ControlCharacters = term.ControlCharacters
}
+// IsTerminating returns whether c is a line terminating character.
+func (t *KernelTermios) IsTerminating(c rune) bool {
+ if t.IsEOF(c) {
+ return true
+ }
+ switch byte(c) {
+ case disabledChar:
+ return false
+ case '\n', t.ControlCharacters[VEOL]:
+ return true
+ case t.ControlCharacters[VEOL2]:
+ return t.LEnabled(IEXTEN)
+ }
+ return false
+}
+
+// IsEOF returns whether c is the EOF character.
+func (t *KernelTermios) IsEOF(c rune) bool {
+ return utf8.RuneLen(c) == 1 && byte(c) == t.ControlCharacters[VEOF] && t.ControlCharacters[VEOF] != disabledChar
+}
+
// Input flags.
const (
IGNBRK = 0000001
diff --git a/pkg/sentry/fs/tty/line_discipline.go b/pkg/sentry/fs/tty/line_discipline.go
index a3aa95ece..bdc4f5b92 100644
--- a/pkg/sentry/fs/tty/line_discipline.go
+++ b/pkg/sentry/fs/tty/line_discipline.go
@@ -28,9 +28,90 @@ import (
)
const (
+ // canonMaxBytes is the number of bytes that fit into a single line of
+ // terminal input in canonical mode. This corresponds to N_TTY_BUF_SIZE
+ // in include/linux/tty.h.
+ canonMaxBytes = 4096
+
+ // nonCanonMaxBytes is the maximum number of bytes that can be read at
+ // a time in noncanonical mode.
+ nonCanonMaxBytes = canonMaxBytes - 1
+
spacesPerTab = 8
)
+// 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
+// processed (i.e. undergo termios transformations) as they are added to the
+// read buffer. The read buffer is readable when its length is nonzero and
+// readable is true.
+type queue struct {
+ waiter.Queue `state:"nosave"`
+
+ // readBuf is buffer of data ready to be read when readable is true.
+ // This data has been processed.
+ readBuf bytes.Buffer `state:".([]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)"`
+
+ // readable indicates whether the read buffer can be read from. In
+ // canonical mode, there can be an unterminated line in the read buffer,
+ // so readable must be checked.
+ readable bool
+}
+
+// saveReadBuf is invoked by stateify.
+func (q *queue) saveReadBuf() []byte {
+ return append([]byte(nil), q.readBuf.Bytes()...)
+}
+
+// loadReadBuf is invoked by stateify.
+func (q *queue) loadReadBuf(b []byte) {
+ q.readBuf.Write(b)
+}
+
+// saveWaitBuf is invoked by stateify.
+func (q *queue) saveWaitBuf() []byte {
+ return append([]byte(nil), q.waitBuf.Bytes()...)
+}
+
+// loadWaitBuf is invoked by stateify.
+func (q *queue) loadWaitBuf(b []byte) {
+ q.waitBuf.Write(b)
+}
+
+// readReadiness returns whether q is ready to be read from.
+func (q *queue) readReadiness(t *linux.KernelTermios) waiter.EventMask {
+ if q.readBuf.Len() > 0 && q.readable {
+ return waiter.EventIn
+ }
+ return waiter.EventMask(0)
+}
+
+// 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
+}
+
+// readableSize writes the number of readable bytes to userspace.
+func (q *queue) readableSize(ctx context.Context, io usermem.IO, args arch.SyscallArguments) error {
+ var size int32
+ if q.readable {
+ size = int32(q.readBuf.Len())
+ }
+
+ _, err := usermem.CopyObjectOut(ctx, io, args[2].Pointer(), size, usermem.IOOpts{
+ AddressSpaceActive: true,
+ })
+ return err
+
+}
+
// lineDiscipline dictates how input and output are handled between the
// pseudoterminal (pty) master and slave. It can be configured to alter I/O,
// modify control characters (e.g. Ctrl-C for SIGINT), etc. The following man
@@ -50,7 +131,7 @@ const (
//
// input from terminal +-------------+ input to process (e.g. bash)
// +------------------------>| input queue |---------------------------+
-// | +-------------+ |
+// | (inputQueueWrite) +-------------+ (inputQueueRead) |
// | |
// | v
// masterFD slaveFD
@@ -58,7 +139,7 @@ const (
// | |
// | output to terminal +--------------+ output from process |
// +------------------------| output queue |<--------------------------+
-// +--------------+
+// (outputQueueRead) +--------------+ (outputQueueWrite)
//
// Lock order:
// inMu
@@ -102,14 +183,25 @@ func (l *lineDiscipline) getTermios(ctx context.Context, io usermem.IO, args arc
// setTermios sets a linux.Termios for the tty.
func (l *lineDiscipline) setTermios(ctx context.Context, io usermem.IO, args arch.SyscallArguments) (uintptr, error) {
+ l.inMu.Lock()
+ defer l.inMu.Unlock()
l.termiosMu.Lock()
defer l.termiosMu.Unlock()
+ oldCanonEnabled := l.termios.LEnabled(linux.ICANON)
// We must copy a Termios struct, not KernelTermios.
var t linux.Termios
_, err := usermem.CopyObjectIn(ctx, io, args[2].Pointer(), &t, usermem.IOOpts{
AddressSpaceActive: true,
})
l.termios.FromTermios(t)
+
+ // If canonical mode is turned off, move bytes from inQueue's wait
+ // buffer to its read buffer. Anything already in the read buffer is
+ // now readable.
+ if oldCanonEnabled && !l.termios.LEnabled(linux.ICANON) {
+ l.pushWaitBuf(&l.inQueue, transformInput)
+ }
+
return 0, err
}
@@ -118,7 +210,9 @@ func (l *lineDiscipline) masterReadiness() waiter.EventMask {
defer l.inMu.Unlock()
l.outMu.Lock()
defer l.outMu.Unlock()
- return l.inQueue.writeReadiness() | l.outQueue.readReadiness()
+ // We don't have to lock a termios because the default master termios
+ // is immutable.
+ return l.inQueue.writeReadiness(&linux.MasterTermios) | l.outQueue.readReadiness(&linux.MasterTermios)
}
func (l *lineDiscipline) slaveReadiness() waiter.EventMask {
@@ -126,93 +220,97 @@ func (l *lineDiscipline) slaveReadiness() waiter.EventMask {
defer l.inMu.Unlock()
l.outMu.Lock()
defer l.outMu.Unlock()
- return l.outQueue.writeReadiness() | l.inQueue.readReadiness()
-}
-
-// queue represents one of the input or output queues between a pty master and
-// slave.
-type queue struct {
- waiter.Queue `state:"nosave"`
- buf bytes.Buffer `state:".([]byte)"`
-}
-
-// saveBuf is invoked by stateify.
-func (q *queue) saveBuf() []byte {
- return append([]byte(nil), q.buf.Bytes()...)
-}
-
-// loadBuf is invoked by stateify.
-func (q *queue) loadBuf(b []byte) {
- q.buf.Write(b)
-}
-
-// readReadiness returns whether q is ready to be read from.
-//
-// Preconditions: q's mutex must be held.
-func (q *queue) readReadiness() waiter.EventMask {
- ready := waiter.EventMask(0)
- if q.buf.Len() > 0 {
- ready |= waiter.EventIn
- }
- return ready
+ l.termiosMu.Lock()
+ defer l.termiosMu.Unlock()
+ return l.outQueue.writeReadiness(&l.termios) | l.inQueue.readReadiness(&l.termios)
}
-// writeReadiness returns whether q is ready to be written to.
-func (q *queue) writeReadiness() waiter.EventMask {
- return waiter.EventOut
+func (l *lineDiscipline) inputQueueReadSize(ctx context.Context, io usermem.IO, args arch.SyscallArguments) error {
+ l.inMu.Lock()
+ defer l.inMu.Unlock()
+ return l.inQueue.readableSize(ctx, io, args)
}
func (l *lineDiscipline) inputQueueRead(ctx context.Context, dst usermem.IOSequence) (int64, error) {
l.inMu.Lock()
defer l.inMu.Unlock()
- return l.queueRead(ctx, dst, &l.inQueue)
+ return l.queueRead(ctx, dst, &l.inQueue, transformInput)
}
func (l *lineDiscipline) inputQueueWrite(ctx context.Context, src usermem.IOSequence) (int64, error) {
l.inMu.Lock()
defer l.inMu.Unlock()
- return l.queueWrite(ctx, src, &l.inQueue, false)
+ return l.queueWrite(ctx, src, &l.inQueue, transformInput)
+}
+
+func (l *lineDiscipline) outputQueueReadSize(ctx context.Context, io usermem.IO, args arch.SyscallArguments) error {
+ l.outMu.Lock()
+ defer l.outMu.Unlock()
+ return l.outQueue.readableSize(ctx, io, args)
}
func (l *lineDiscipline) outputQueueRead(ctx context.Context, dst usermem.IOSequence) (int64, error) {
l.outMu.Lock()
defer l.outMu.Unlock()
- return l.queueRead(ctx, dst, &l.outQueue)
+ return l.queueRead(ctx, dst, &l.outQueue, transformOutput)
}
func (l *lineDiscipline) outputQueueWrite(ctx context.Context, src usermem.IOSequence) (int64, error) {
l.outMu.Lock()
defer l.outMu.Unlock()
- return l.queueWrite(ctx, src, &l.outQueue, true)
+ return l.queueWrite(ctx, src, &l.outQueue, transformOutput)
}
// queueRead reads from q to userspace.
//
// Preconditions: q's lock must be held.
-func (l *lineDiscipline) queueRead(ctx context.Context, dst usermem.IOSequence, q *queue) (int64, error) {
- // Copy bytes out to user-space. queueRead doesn't have to do any
- // processing or other extra work -- that's all taken care of when
- // writing to a queue.
- n, err := q.buf.WriteTo(dst.Writer(ctx))
+func (l *lineDiscipline) queueRead(ctx context.Context, dst usermem.IOSequence, q *queue, f transform) (int64, error) {
+ if !q.readable {
+ return 0, syserror.ErrWouldBlock
+ }
+
+ // Read out from the read buffer.
+ n := canonMaxBytes
+ if n > int(dst.NumBytes()) {
+ n = int(dst.NumBytes())
+ }
+ if n > q.readBuf.Len() {
+ n = q.readBuf.Len()
+ }
+ n, err := dst.Writer(ctx).Write(q.readBuf.Bytes()[:n])
+ if err != nil {
+ return 0, 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.
+ l.termiosMu.Lock()
+ defer l.termiosMu.Unlock()
+ l.pushWaitBuf(q, f)
// If state changed, notify any waiters. If nothing was available to
// read, let the caller know we could block.
if n > 0 {
q.Notify(waiter.EventOut)
- } else if err == nil {
+ } else {
return 0, syserror.ErrWouldBlock
}
- return int64(n), err
+ return int64(n), nil
}
-// queueWrite writes to q from userspace. `output` is whether the queue being
-// written to should be subject to output processing (i.e. whether it is the
-// output queue).
+// queueWrite writes to q from userspace. f is the function used to perform
+// processing on data being written and write it to the read buffer.
//
// Precondition: q's lock must be held.
-func (l *lineDiscipline) queueWrite(ctx context.Context, src usermem.IOSequence, q *queue, output bool) (int64, error) {
+func (l *lineDiscipline) queueWrite(ctx context.Context, src usermem.IOSequence, q *queue, f transform) (int64, error) {
// TODO: Use CopyInTo/safemem to avoid extra copying.
- // Get the bytes to write from user-space.
+ // Copy in the bytes to write from user-space.
b := make([]byte, src.NumBytes())
n, err := src.CopyIn(ctx, b)
if err != nil {
@@ -220,49 +318,69 @@ func (l *lineDiscipline) queueWrite(ctx context.Context, src usermem.IOSequence,
}
b = b[:n]
+ // Write as much as possible to the read buffer.
+ l.termiosMu.Lock()
+ defer l.termiosMu.Unlock()
+ n = f(l, q, b)
+
+ // Write remaining data to the wait buffer.
+ nWaiting, _ := q.waitBuf.Write(b[n:])
+
// If state changed, notify any waiters. If we were unable to write
// anything, let the caller know we could block.
if n > 0 {
q.Notify(waiter.EventIn)
- } else {
+ } else if nWaiting == 0 {
return 0, syserror.ErrWouldBlock
}
+ return int64(n + nWaiting), nil
+}
- // Optionally perform line discipline transformations depending on
- // whether we're writing to the input queue or output queue.
- var buf *bytes.Buffer
- l.termiosMu.Lock()
- if output {
- buf = l.transformOutput(b)
- } else {
- buf = l.transformInput(b)
- }
- l.termiosMu.Unlock()
+// pushWaitBuf fills the queue's read buffer with data from the wait buffer.
+//
+// Precondition: l.inMu and l.termiosMu must be held.
+func (l *lineDiscipline) pushWaitBuf(q *queue, f transform) {
+ // Remove bytes from the wait buffer and move them to the read buffer.
+ n := f(l, q, q.waitBuf.Bytes())
+ q.waitBuf.Next(n)
- // Enqueue buf at the end of the queue.
- buf.WriteTo(&q.buf)
- return int64(n), err
+ // If state changed, notify any waiters.
+ if n > 0 {
+ q.Notify(waiter.EventIn)
+ }
}
+// transform functions require the passed in lineDiscipline's mutex to be held.
+type transform func(*lineDiscipline, *queue, []byte) int
+
// transformOutput does output processing for one end of the pty. See
// drivers/tty/n_tty.c:do_output_char for an analogous kernel function.
//
-// Precondition: l.termiosMu must be held.
-func (l *lineDiscipline) transformOutput(buf []byte) *bytes.Buffer {
+// Precondition: l.termiosMu and q's mutex must be held.
+func transformOutput(l *lineDiscipline, q *queue, buf []byte) int {
+ // transformOutput is effectively always in noncanonical mode, as the
+ // master termios never has ICANON set.
+
if !l.termios.OEnabled(linux.OPOST) {
- return bytes.NewBuffer(buf)
+ n, _ := q.readBuf.Write(buf)
+ if q.readBuf.Len() > 0 {
+ q.readable = true
+ }
+ return n
}
- var ret bytes.Buffer
+ var ret int
for len(buf) > 0 {
- c := l.removeRune(&buf)
+ c, size := l.peekRune(buf)
+ ret += size
+ buf = buf[size:]
switch c {
case '\n':
if l.termios.OEnabled(linux.ONLRET) {
l.column = 0
}
if l.termios.OEnabled(linux.ONLCR) {
- ret.Write([]byte{'\r', '\n'})
+ q.readBuf.Write([]byte{'\r', '\n'})
continue
}
case '\r':
@@ -281,7 +399,7 @@ func (l *lineDiscipline) transformOutput(buf []byte) *bytes.Buffer {
spaces := spacesPerTab - l.column%spacesPerTab
if l.termios.OutputFlags&linux.TABDLY == linux.XTABS {
l.column += spaces
- ret.Write(bytes.Repeat([]byte{' '}, 8))
+ q.readBuf.Write(bytes.Repeat([]byte{' '}, spacesPerTab))
continue
}
l.column += spaces
@@ -292,24 +410,40 @@ func (l *lineDiscipline) transformOutput(buf []byte) *bytes.Buffer {
default:
l.column++
}
- ret.WriteRune(c)
+ q.readBuf.WriteRune(c)
+ }
+ if q.readBuf.Len() > 0 {
+ q.readable = true
}
- return &ret
+ return ret
}
-// transformInput does input processing for one end of the pty. Characters
-// read are transformed according to flags set in the termios struct. See
+// transformInput does input processing for one end of the pty. Characters read
+// are transformed according to flags set in the termios struct. See
// drivers/tty/n_tty.c:n_tty_receive_char_special for an analogous kernel
// function.
//
-// Precondition: l.termiosMu must be held.
-func (l *lineDiscipline) transformInput(buf []byte) *bytes.Buffer {
- var ret bytes.Buffer
- for len(buf) > 0 {
- c := l.removeRune(&buf)
+// Precondition: l.termiosMu and q's mutex must be held.
+func transformInput(l *lineDiscipline, q *queue, buf []byte) int {
+ // If there's a line waiting to be read in canonical mode, don't write
+ // anything else to the read buffer.
+ if l.termios.LEnabled(linux.ICANON) && q.readable {
+ return 0
+ }
+
+ maxBytes := nonCanonMaxBytes
+ if l.termios.LEnabled(linux.ICANON) {
+ maxBytes = canonMaxBytes
+ }
+
+ var ret int
+ for len(buf) > 0 && q.readBuf.Len() < canonMaxBytes {
+ c, size := l.peekRune(buf)
switch c {
case '\r':
if l.termios.IEnabled(linux.IGNCR) {
+ buf = buf[size:]
+ ret += size
continue
}
if l.termios.IEnabled(linux.ICRNL) {
@@ -320,23 +454,63 @@ func (l *lineDiscipline) transformInput(buf []byte) *bytes.Buffer {
c = '\r'
}
}
- ret.WriteRune(c)
+
+ // In canonical mode, we discard non-terminating characters
+ // after the first 4095.
+ if l.shouldDiscard(q, c) {
+ buf = buf[size:]
+ ret += size
+ continue
+ }
+
+ // Stop if the buffer would be overfilled.
+ if q.readBuf.Len()+size > maxBytes {
+ break
+ }
+ buf = buf[size:]
+ ret += size
+
+ // If we get EOF, make the buffer available for reading.
+ if l.termios.LEnabled(linux.ICANON) && l.termios.IsEOF(c) {
+ q.readable = true
+ break
+ }
+
+ q.readBuf.WriteRune(c)
+
+ // If we finish a line, make it available for reading.
+ if l.termios.LEnabled(linux.ICANON) && l.termios.IsTerminating(c) {
+ q.readable = true
+ break
+ }
+ }
+
+ // In noncanonical mode, everything is readable.
+ if !l.termios.LEnabled(linux.ICANON) && q.readBuf.Len() > 0 {
+ q.readable = true
}
- return &ret
+
+ return ret
+}
+
+// shouldDiscard returns whether c should be discarded. In canonical mode, if
+// too many bytes are enqueued, we keep reading input and discarding it until
+// we find a terminating character. Signal/echo processing still occurs.
+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)
}
-// removeRune removes and returns the first rune from the byte array. The
-// buffer's length is updated accordingly.
-func (l *lineDiscipline) removeRune(b *[]byte) rune {
+// peekRune returns the first rune from the byte array depending on whether
+// UTF8 is enabled.
+func (l *lineDiscipline) peekRune(b []byte) (rune, int) {
var c rune
var size int
// If UTF-8 support is enabled, runes might be multiple bytes.
if l.termios.IEnabled(linux.IUTF8) {
- c, size = utf8.DecodeRune(*b)
+ c, size = utf8.DecodeRune(b)
} else {
- c = rune((*b)[0])
+ c = rune(b[0])
size = 1
}
- *b = (*b)[size:]
- return c
+ return c, size
}
diff --git a/pkg/sentry/fs/tty/master.go b/pkg/sentry/fs/tty/master.go
index 3c47ee517..74cdbe874 100644
--- a/pkg/sentry/fs/tty/master.go
+++ b/pkg/sentry/fs/tty/master.go
@@ -148,6 +148,9 @@ func (mf *masterFileOperations) Write(ctx context.Context, _ *fs.File, src userm
// Ioctl implements fs.FileOperations.Ioctl.
func (mf *masterFileOperations) Ioctl(ctx context.Context, io usermem.IO, args arch.SyscallArguments) (uintptr, error) {
switch args[1].Uint() {
+ case linux.FIONREAD: // linux.FIONREAD == linux.TIOCINQ
+ // Get the number of bytes in the output queue read buffer.
+ return 0, mf.t.ld.outputQueueReadSize(ctx, io, args)
case linux.TCGETS:
// N.B. TCGETS on the master actually returns the configuration
// of the slave end.
diff --git a/pkg/sentry/fs/tty/slave.go b/pkg/sentry/fs/tty/slave.go
index 9178071a4..f5eec726e 100644
--- a/pkg/sentry/fs/tty/slave.go
+++ b/pkg/sentry/fs/tty/slave.go
@@ -133,6 +133,9 @@ func (sf *slaveFileOperations) Write(ctx context.Context, _ *fs.File, src userme
// Ioctl implements fs.FileOperations.Ioctl.
func (sf *slaveFileOperations) Ioctl(ctx context.Context, io usermem.IO, args arch.SyscallArguments) (uintptr, error) {
switch args[1].Uint() {
+ case linux.FIONREAD: // linux.FIONREAD == linux.TIOCINQ
+ // Get the number of bytes in the input queue read buffer.
+ return 0, sf.si.t.ld.inputQueueReadSize(ctx, io, args)
case linux.TCGETS:
return sf.si.t.ld.getTermios(ctx, io, args)
case linux.TCSETS:
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-16 11:45:07 +0000