Add path option to the pty char backend which will create a symbolic link to the given path that points to the allocated PTY.
This avoids having to make QMP or HMP monitor queries to find out what the new PTY device path is. Based on patch from Paulo Neves: https://patchew.org/QEMU/1548509635-15776-1-git-send-email-ptsne...@gmail.com/ Tested with the following invocations that the link is created and removed when qemu stops: qemu-system-x86_64 -nodefaults -mon chardev=compat_monitor \ -chardev pty,path=test,id=compat_monitor0 qemu-system-x86_64 -nodefaults -monitor pty:test Also tested that when a link path is not passed invocations still work, e.g.: qemu-system-x86_64 -monitor pty Co-authored-by: Paulo Neves <ptsne...@gmail.com> Signed-off-by: Paulo Neves <ptsne...@gmail.com> [OP: rebase and address original patch review comments] Signed-off-by: Octavian Purdila <ta...@google.com> --- Changes since v1: * Keep the original Signed-off-by from Paulo and add one line description with further changes * Update commit message with justification for why the new functionality is useful * Don't close master_fd when symlink creation fails to avoid double close * Update documentation for clarity chardev/char-pty.c | 33 +++++++++++++++++++++++++++++++++ chardev/char.c | 5 +++++ qapi/char.json | 4 ++-- qemu-options.hx | 24 ++++++++++++++++++------ 4 files changed, 58 insertions(+), 8 deletions(-) diff --git a/chardev/char-pty.c b/chardev/char-pty.c index cc2f7617fe..b5a4eb59fc 100644 --- a/chardev/char-pty.c +++ b/chardev/char-pty.c @@ -29,6 +29,7 @@ #include "qemu/sockets.h" #include "qemu/error-report.h" #include "qemu/module.h" +#include "qemu/option.h" #include "qemu/qemu-print.h" #include "chardev/char-io.h" @@ -41,6 +42,7 @@ struct PtyChardev { int connected; GSource *timer_src; + char *symlink_path; }; typedef struct PtyChardev PtyChardev; @@ -204,6 +206,12 @@ static void char_pty_finalize(Object *obj) Chardev *chr = CHARDEV(obj); PtyChardev *s = PTY_CHARDEV(obj); + /* unlink symlink */ + if (s->symlink_path) { + unlink(s->symlink_path); + g_free(s->symlink_path); + } + pty_chr_state(chr, 0); object_unref(OBJECT(s->ioc)); pty_chr_timer_cancel(s); @@ -330,6 +338,7 @@ static void char_pty_open(Chardev *chr, int master_fd, slave_fd; char pty_name[PATH_MAX]; char *name; + char *symlink_path = backend->u.pty.data->device; master_fd = qemu_openpty_raw(&slave_fd, pty_name); if (master_fd < 0) { @@ -354,12 +363,36 @@ static void char_pty_open(Chardev *chr, g_free(name); s->timer_src = NULL; *be_opened = false; + + /* create symbolic link */ + if (symlink_path) { + int res = symlink(pty_name, symlink_path); + + if (res != 0) { + error_setg_errno(errp, errno, "Failed to create PTY symlink"); + } else { + s->symlink_path = g_strdup(symlink_path); + } + } +} + +static void char_pty_parse(QemuOpts *opts, ChardevBackend *backend, + Error **errp) +{ + const char *path = qemu_opt_get(opts, "path"); + ChardevHostdev *dev; + + backend->type = CHARDEV_BACKEND_KIND_PTY; + dev = backend->u.pty.data = g_new0(ChardevHostdev, 1); + qemu_chr_parse_common(opts, qapi_ChardevHostdev_base(dev)); + dev->device = path ? g_strdup(path) : NULL; } static void char_pty_class_init(ObjectClass *oc, void *data) { ChardevClass *cc = CHARDEV_CLASS(oc); + cc->parse = char_pty_parse; cc->open = char_pty_open; cc->chr_write = char_pty_chr_write; cc->chr_update_read_handler = pty_chr_update_read_handler; diff --git a/chardev/char.c b/chardev/char.c index 3c43fb1278..404c6b8a4f 100644 --- a/chardev/char.c +++ b/chardev/char.c @@ -428,6 +428,11 @@ QemuOpts *qemu_chr_parse_compat(const char *label, const char *filename, qemu_opt_set(opts, "path", p, &error_abort); return opts; } + if (strstart(filename, "pty:", &p)) { + qemu_opt_set(opts, "backend", "pty", &error_abort); + qemu_opt_set(opts, "path", p, &error_abort); + return opts; + } if (strstart(filename, "tcp:", &p) || strstart(filename, "telnet:", &p) || strstart(filename, "tn3270:", &p) || diff --git a/qapi/char.json b/qapi/char.json index 777dde55d9..4c74bfc437 100644 --- a/qapi/char.json +++ b/qapi/char.json @@ -509,7 +509,7 @@ ## # @ChardevHostdevWrapper: # -# @data: Configuration info for device and pipe chardevs +# @data: Configuration info for device, pty and pipe chardevs # # Since: 1.4 ## @@ -650,7 +650,7 @@ 'pipe': 'ChardevHostdevWrapper', 'socket': 'ChardevSocketWrapper', 'udp': 'ChardevUdpWrapper', - 'pty': 'ChardevCommonWrapper', + 'pty': 'ChardevHostdevWrapper', 'null': 'ChardevCommonWrapper', 'mux': 'ChardevMuxWrapper', 'msmouse': 'ChardevCommonWrapper', diff --git a/qemu-options.hx b/qemu-options.hx index 8ca7f34ef0..94ffb1a605 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -3569,7 +3569,7 @@ DEF("chardev", HAS_ARG, QEMU_OPTION_chardev, "-chardev console,id=id[,mux=on|off][,logfile=PATH][,logappend=on|off]\n" "-chardev serial,id=id,path=path[,mux=on|off][,logfile=PATH][,logappend=on|off]\n" #else - "-chardev pty,id=id[,mux=on|off][,logfile=PATH][,logappend=on|off]\n" + "-chardev pty,id=id[,path=path][,mux=on|off][,logfile=PATH][,logappend=on|off]\n" "-chardev stdio,id=id[,mux=on|off][,signal=on|off][,logfile=PATH][,logappend=on|off]\n" #endif #ifdef CONFIG_BRLAPI @@ -3808,12 +3808,18 @@ The available backends are: ``path`` specifies the name of the serial device to open. -``-chardev pty,id=id`` - Create a new pseudo-terminal on the host and connect to it. ``pty`` - does not take any options. +``-chardev pty,id=id[,path=path]`` + Create a new pseudo-terminal on the host and connect to it. ``pty`` is not available on Windows hosts. + If ``path`` is specified, QEMU will create a symbolic link at + that location which points to the new PTY device. + + This avoids having to make QMP or HMP monitor queries to find out + what the new PTY device path is. + + ``-chardev stdio,id=id[,signal=on|off]`` Connect to standard input and standard output of the QEMU process. @@ -4171,8 +4177,14 @@ SRST vc:80Cx24C - ``pty`` - [Linux only] Pseudo TTY (a new PTY is automatically allocated) + ``pty[:path]`` + [Linux only] Pseudo TTY (a new PTY is automatically allocated). + + If ``path`` is specified, QEMU will create a symbolic link at + that location which points to the new PTY device. + + This avoids having to make QMP or HMP monitor queries to find + out what the new PTY device path is. ``none`` No device is allocated. Note that for machine types which -- 2.45.1.288.g0e0cd299f1-goog
