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Use separate descriptors in bhyve's stdio uart backend.

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bhyve was previously using stdin for both reading and writing to the
console, which made it difficult to redirect console output.  Use
stdin for reading and stdout for writing.  This makes it easier to use
bhyve as a backend for syzkaller.

As a side effect, the change fixes a minor bug which would cause bhyve
to fail with ENOTCAPABLE if configured to use nmdm for com1 and stdio
for com2.

bhyveload already uses separate descriptors, as does the bvmcons driver.

Reviewed by:	jhb
MFC after:	1 month
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D19788
This commit is contained in:
Mark Johnston 2019-04-22 13:57:52 +00:00
parent cddbc3b408
commit d6ef759e5d
1 changed files with 70 additions and 60 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

130
usr.sbin/bhyve/uart_emul.c
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@ -100,8 +100,8 @@ struct fifo {
struct ttyfd {
bool opened;
int fd; /* tty device file descriptor */
struct termios tio_orig, tio_new; /* I/O Terminals */
int rfd; /* fd for reading */
int wfd; /* fd for writing, may be == rfd */
};
struct uart_softc {
@ -141,16 +141,15 @@ ttyclose(void)
static void
ttyopen(struct ttyfd *tf)
{
struct termios orig, new;
tcgetattr(tf->fd, &tf->tio_orig);
tf->tio_new = tf->tio_orig;
cfmakeraw(&tf->tio_new);
tf->tio_new.c_cflag |= CLOCAL;
tcsetattr(tf->fd, TCSANOW, &tf->tio_new);
if (tf->fd == STDIN_FILENO) {
tio_stdio_orig = tf->tio_orig;
tcgetattr(tf->rfd, &orig);
new = orig;
cfmakeraw(&new);
new.c_cflag |= CLOCAL;
tcsetattr(tf->rfd, TCSANOW, &new);
if (uart_stdio) {
tio_stdio_orig = orig;
atexit(ttyclose);
}
}
@ -160,7 +159,7 @@ ttyread(struct ttyfd *tf)
{
unsigned char rb;
if (read(tf->fd, &rb, 1) == 1)
if (read(tf->rfd, &rb, 1) == 1)
return (rb);
else
return (-1);
@ -170,7 +169,7 @@ static void
ttywrite(struct ttyfd *tf, unsigned char wb)
{
(void)write(tf->fd, &wb, 1);
(void)write(tf->wfd, &wb, 1);
}
static void
@ -190,7 +189,7 @@ rxfifo_reset(struct uart_softc *sc, int size)
* Flush any unread input from the tty buffer.
*/
while (1) {
nread = read(sc->tty.fd, flushbuf, sizeof(flushbuf));
nread = read(sc->tty.rfd, flushbuf, sizeof(flushbuf));
if (nread != sizeof(flushbuf))
break;
}
@ -277,7 +276,7 @@ uart_opentty(struct uart_softc *sc)
{
ttyopen(&sc->tty);
sc->mev = mevent_add(sc->tty.fd, EVF_READ, uart_drain, sc);
sc->mev = mevent_add(sc->tty.rfd, EVF_READ, uart_drain, sc);
assert(sc->mev != NULL);
}
@ -374,7 +373,7 @@ uart_drain(int fd, enum ev_type ev, void *arg)
sc = arg;
assert(fd == sc->tty.fd);
assert(fd == sc->tty.rfd);
assert(ev == EVF_READ);
/*
@ -636,69 +635,80 @@ uart_init(uart_intr_func_t intr_assert, uart_intr_func_t intr_deassert,
return (sc);
}
static int
uart_stdio_backend(struct uart_softc *sc)
{
#ifndef WITHOUT_CAPSICUM
cap_rights_t rights;
cap_ioctl_t cmds[] = { TIOCGETA, TIOCSETA, TIOCGWINSZ };
#endif
if (uart_stdio)
return (-1);
sc->tty.rfd = STDIN_FILENO;
sc->tty.wfd = STDOUT_FILENO;
sc->tty.opened = true;
if (fcntl(sc->tty.rfd, F_SETFL, O_NONBLOCK) != 0)
return (-1);
if (fcntl(sc->tty.wfd, F_SETFL, O_NONBLOCK) != 0)
return (-1);
#ifndef WITHOUT_CAPSICUM
cap_rights_init(&rights, CAP_EVENT, CAP_IOCTL, CAP_READ);
if (caph_rights_limit(sc->tty.rfd, &rights) == -1)
errx(EX_OSERR, "Unable to apply rights for sandbox");
if (caph_ioctls_limit(sc->tty.rfd, cmds, nitems(cmds)) == -1)
errx(EX_OSERR, "Unable to apply rights for sandbox");
#endif
uart_stdio = true;
return (0);
}
static int
uart_tty_backend(struct uart_softc *sc, const char *opts)
{
#ifndef WITHOUT_CAPSICUM
cap_rights_t rights;
cap_ioctl_t cmds[] = { TIOCGETA, TIOCSETA, TIOCGWINSZ };
#endif
int fd;
int retval;
retval = -1;
fd = open(opts, O_RDWR | O_NONBLOCK);
if (fd > 0 && isatty(fd)) {
sc->tty.fd = fd;
sc->tty.opened = true;
retval = 0;
}
if (fd < 0 || !isatty(fd))
return (-1);
return (retval);
sc->tty.rfd = sc->tty.wfd = fd;
sc->tty.opened = true;
#ifndef WITHOUT_CAPSICUM
cap_rights_init(&rights, CAP_EVENT, CAP_IOCTL, CAP_READ, CAP_WRITE);
if (caph_rights_limit(fd, &rights) == -1)
errx(EX_OSERR, "Unable to apply rights for sandbox");
if (caph_ioctls_limit(fd, cmds, nitems(cmds)) == -1)
errx(EX_OSERR, "Unable to apply rights for sandbox");
#endif
return (0);
}
int
uart_set_backend(struct uart_softc *sc, const char *opts)
{
int retval;
#ifndef WITHOUT_CAPSICUM
cap_rights_t rights;
cap_ioctl_t cmds[] = { TIOCGETA, TIOCSETA, TIOCGWINSZ };
#endif
retval = -1;
if (opts == NULL)
return (0);
if (strcmp("stdio", opts) == 0) {
if (!uart_stdio) {
sc->tty.fd = STDIN_FILENO;
sc->tty.opened = true;
uart_stdio = true;
retval = 0;
}
} else if (uart_tty_backend(sc, opts) == 0) {
retval = 0;
}
/* Make the backend file descriptor non-blocking */
if (strcmp("stdio", opts) == 0)
retval = uart_stdio_backend(sc);
else
retval = uart_tty_backend(sc, opts);
if (retval == 0)
retval = fcntl(sc->tty.fd, F_SETFL, O_NONBLOCK);
if (retval == 0) {
#ifndef WITHOUT_CAPSICUM
cap_rights_init(&rights, CAP_EVENT, CAP_IOCTL, CAP_READ,
CAP_WRITE);
if (caph_rights_limit(sc->tty.fd, &rights) == -1)
errx(EX_OSERR, "Unable to apply rights for sandbox");
if (caph_ioctls_limit(sc->tty.fd, cmds, nitems(cmds)) == -1)
errx(EX_OSERR, "Unable to apply rights for sandbox");
if (!uart_stdio) {
if (caph_limit_stdin() == -1)
errx(EX_OSERR,
"Unable to apply rights for sandbox");
}
#endif
uart_opentty(sc);
}
return (retval);
}