cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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pps-ldisc.c (3251B)

      1// SPDX-License-Identifier: GPL-2.0-or-later
      2/*
      3 * pps-ldisc.c -- PPS line discipline
      4 *
      5 * Copyright (C) 2008	Rodolfo Giometti <giometti@linux.it>
      6 */
      7
      8#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
      9
     10#include <linux/module.h>
     11#include <linux/serial_core.h>
     12#include <linux/tty.h>
     13#include <linux/pps_kernel.h>
     14#include <linux/bug.h>
     15
     16static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status)
     17{
     18	struct pps_device *pps;
     19	struct pps_event_time ts;
     20
     21	pps_get_ts(&ts);
     22
     23	pps = pps_lookup_dev(tty);
     24	/*
     25	 * This should never fail, but the ldisc locking is very
     26	 * convoluted, so don't crash just in case.
     27	 */
     28	if (WARN_ON_ONCE(pps == NULL))
     29		return;
     30
     31	/* Now do the PPS event report */
     32	pps_event(pps, &ts, status ? PPS_CAPTUREASSERT :
     33			PPS_CAPTURECLEAR, NULL);
     34
     35	dev_dbg(pps->dev, "PPS %s at %lu\n",
     36			status ? "assert" : "clear", jiffies);
     37}
     38
     39static int (*alias_n_tty_open)(struct tty_struct *tty);
     40
     41static int pps_tty_open(struct tty_struct *tty)
     42{
     43	struct pps_source_info info;
     44	struct tty_driver *drv = tty->driver;
     45	int index = tty->index + drv->name_base;
     46	struct pps_device *pps;
     47	int ret;
     48
     49	info.owner = THIS_MODULE;
     50	info.dev = NULL;
     51	snprintf(info.name, PPS_MAX_NAME_LEN, "%s%d", drv->driver_name, index);
     52	snprintf(info.path, PPS_MAX_NAME_LEN, "/dev/%s%d", drv->name, index);
     53	info.mode = PPS_CAPTUREBOTH | \
     54			PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
     55			PPS_CANWAIT | PPS_TSFMT_TSPEC;
     56
     57	pps = pps_register_source(&info, PPS_CAPTUREBOTH | \
     58				PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
     59	if (IS_ERR(pps)) {
     60		pr_err("cannot register PPS source \"%s\"\n", info.path);
     61		return PTR_ERR(pps);
     62	}
     63	pps->lookup_cookie = tty;
     64
     65	/* Now open the base class N_TTY ldisc */
     66	ret = alias_n_tty_open(tty);
     67	if (ret < 0) {
     68		pr_err("cannot open tty ldisc \"%s\"\n", info.path);
     69		goto err_unregister;
     70	}
     71
     72	dev_info(pps->dev, "source \"%s\" added\n", info.path);
     73
     74	return 0;
     75
     76err_unregister:
     77	pps_unregister_source(pps);
     78	return ret;
     79}
     80
     81static void (*alias_n_tty_close)(struct tty_struct *tty);
     82
     83static void pps_tty_close(struct tty_struct *tty)
     84{
     85	struct pps_device *pps = pps_lookup_dev(tty);
     86
     87	alias_n_tty_close(tty);
     88
     89	if (WARN_ON(!pps))
     90		return;
     91
     92	dev_info(pps->dev, "removed\n");
     93	pps_unregister_source(pps);
     94}
     95
     96static struct tty_ldisc_ops pps_ldisc_ops;
     97
     98/*
     99 * Module stuff
    100 */
    101
    102static int __init pps_tty_init(void)
    103{
    104	int err;
    105
    106	/* Inherit the N_TTY's ops */
    107	n_tty_inherit_ops(&pps_ldisc_ops);
    108
    109	/* Save N_TTY's open()/close() methods */
    110	alias_n_tty_open = pps_ldisc_ops.open;
    111	alias_n_tty_close = pps_ldisc_ops.close;
    112
    113	/* Init PPS_TTY data */
    114	pps_ldisc_ops.owner = THIS_MODULE;
    115	pps_ldisc_ops.num = N_PPS;
    116	pps_ldisc_ops.name = "pps_tty";
    117	pps_ldisc_ops.dcd_change = pps_tty_dcd_change;
    118	pps_ldisc_ops.open = pps_tty_open;
    119	pps_ldisc_ops.close = pps_tty_close;
    120
    121	err = tty_register_ldisc(&pps_ldisc_ops);
    122	if (err)
    123		pr_err("can't register PPS line discipline\n");
    124	else
    125		pr_info("PPS line discipline registered\n");
    126
    127	return err;
    128}
    129
    130static void __exit pps_tty_cleanup(void)
    131{
    132	tty_unregister_ldisc(&pps_ldisc_ops);
    133}
    134
    135module_init(pps_tty_init);
    136module_exit(pps_tty_cleanup);
    137
    138MODULE_ALIAS_LDISC(N_PPS);
    139MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
    140MODULE_DESCRIPTION("PPS TTY device driver");
    141MODULE_LICENSE("GPL");