From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt --- drivers/pps/clients/pps-ldisc.c | 141 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 141 insertions(+) create mode 100644 drivers/pps/clients/pps-ldisc.c (limited to 'drivers/pps/clients/pps-ldisc.c') diff --git a/drivers/pps/clients/pps-ldisc.c b/drivers/pps/clients/pps-ldisc.c new file mode 100644 index 000000000..fa5660f3c --- /dev/null +++ b/drivers/pps/clients/pps-ldisc.c @@ -0,0 +1,141 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * pps-ldisc.c -- PPS line discipline + * + * Copyright (C) 2008 Rodolfo Giometti + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include +#include + +static void pps_tty_dcd_change(struct tty_struct *tty, bool active) +{ + struct pps_device *pps; + struct pps_event_time ts; + + pps_get_ts(&ts); + + pps = pps_lookup_dev(tty); + /* + * This should never fail, but the ldisc locking is very + * convoluted, so don't crash just in case. + */ + if (WARN_ON_ONCE(pps == NULL)) + return; + + /* Now do the PPS event report */ + pps_event(pps, &ts, active ? PPS_CAPTUREASSERT : + PPS_CAPTURECLEAR, NULL); + + dev_dbg(&pps->dev, "PPS %s at %lu\n", + active ? "assert" : "clear", jiffies); +} + +static int (*alias_n_tty_open)(struct tty_struct *tty); + +static int pps_tty_open(struct tty_struct *tty) +{ + struct pps_source_info info; + struct tty_driver *drv = tty->driver; + int index = tty->index + drv->name_base; + struct pps_device *pps; + int ret; + + info.owner = THIS_MODULE; + info.dev = NULL; + snprintf(info.name, PPS_MAX_NAME_LEN, "%s%d", drv->driver_name, index); + snprintf(info.path, PPS_MAX_NAME_LEN, "/dev/%s%d", drv->name, index); + info.mode = PPS_CAPTUREBOTH | \ + PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \ + PPS_CANWAIT | PPS_TSFMT_TSPEC; + + pps = pps_register_source(&info, PPS_CAPTUREBOTH | \ + PPS_OFFSETASSERT | PPS_OFFSETCLEAR); + if (IS_ERR(pps)) { + pr_err("cannot register PPS source \"%s\"\n", info.path); + return PTR_ERR(pps); + } + pps->lookup_cookie = tty; + + /* Now open the base class N_TTY ldisc */ + ret = alias_n_tty_open(tty); + if (ret < 0) { + pr_err("cannot open tty ldisc \"%s\"\n", info.path); + goto err_unregister; + } + + dev_dbg(&pps->dev, "source \"%s\" added\n", info.path); + + return 0; + +err_unregister: + pps_unregister_source(pps); + return ret; +} + +static void (*alias_n_tty_close)(struct tty_struct *tty); + +static void pps_tty_close(struct tty_struct *tty) +{ + struct pps_device *pps = pps_lookup_dev(tty); + + alias_n_tty_close(tty); + + if (WARN_ON(!pps)) + return; + + dev_info(&pps->dev, "removed\n"); + pps_unregister_source(pps); +} + +static struct tty_ldisc_ops pps_ldisc_ops; + +/* + * Module stuff + */ + +static int __init pps_tty_init(void) +{ + int err; + + /* Inherit the N_TTY's ops */ + n_tty_inherit_ops(&pps_ldisc_ops); + + /* Save N_TTY's open()/close() methods */ + alias_n_tty_open = pps_ldisc_ops.open; + alias_n_tty_close = pps_ldisc_ops.close; + + /* Init PPS_TTY data */ + pps_ldisc_ops.owner = THIS_MODULE; + pps_ldisc_ops.num = N_PPS; + pps_ldisc_ops.name = "pps_tty"; + pps_ldisc_ops.dcd_change = pps_tty_dcd_change; + pps_ldisc_ops.open = pps_tty_open; + pps_ldisc_ops.close = pps_tty_close; + + err = tty_register_ldisc(&pps_ldisc_ops); + if (err) + pr_err("can't register PPS line discipline\n"); + else + pr_info("PPS line discipline registered\n"); + + return err; +} + +static void __exit pps_tty_cleanup(void) +{ + tty_unregister_ldisc(&pps_ldisc_ops); +} + +module_init(pps_tty_init); +module_exit(pps_tty_cleanup); + +MODULE_ALIAS_LDISC(N_PPS); +MODULE_AUTHOR("Rodolfo Giometti "); +MODULE_DESCRIPTION("PPS TTY device driver"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1