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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background.c (4343B)

      1/*
      2 * JFFS2 -- Journalling Flash File System, Version 2.
      3 *
      4 * Copyright © 2001-2007 Red Hat, Inc.
      5 * Copyright © 2004-2010 David Woodhouse <dwmw2@infradead.org>
      6 *
      7 * Created by David Woodhouse <dwmw2@infradead.org>
      8 *
      9 * For licensing information, see the file 'LICENCE' in this directory.
     10 *
     11 */
     12
     13#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
     14
     15#include <linux/kernel.h>
     16#include <linux/jffs2.h>
     17#include <linux/mtd/mtd.h>
     18#include <linux/completion.h>
     19#include <linux/sched/signal.h>
     20#include <linux/freezer.h>
     21#include <linux/kthread.h>
     22#include "nodelist.h"
     23
     24
     25static int jffs2_garbage_collect_thread(void *);
     26
     27void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c)
     28{
     29	assert_spin_locked(&c->erase_completion_lock);
     30	if (c->gc_task && jffs2_thread_should_wake(c))
     31		send_sig(SIGHUP, c->gc_task, 1);
     32}
     33
     34/* This must only ever be called when no GC thread is currently running */
     35int jffs2_start_garbage_collect_thread(struct jffs2_sb_info *c)
     36{
     37	struct task_struct *tsk;
     38	int ret = 0;
     39
     40	BUG_ON(c->gc_task);
     41
     42	init_completion(&c->gc_thread_start);
     43	init_completion(&c->gc_thread_exit);
     44
     45	tsk = kthread_run(jffs2_garbage_collect_thread, c, "jffs2_gcd_mtd%d", c->mtd->index);
     46	if (IS_ERR(tsk)) {
     47		pr_warn("fork failed for JFFS2 garbage collect thread: %ld\n",
     48			-PTR_ERR(tsk));
     49		complete(&c->gc_thread_exit);
     50		ret = PTR_ERR(tsk);
     51	} else {
     52		/* Wait for it... */
     53		jffs2_dbg(1, "Garbage collect thread is pid %d\n", tsk->pid);
     54		wait_for_completion(&c->gc_thread_start);
     55		ret = tsk->pid;
     56	}
     57
     58	return ret;
     59}
     60
     61void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c)
     62{
     63	int wait = 0;
     64	spin_lock(&c->erase_completion_lock);
     65	if (c->gc_task) {
     66		jffs2_dbg(1, "Killing GC task %d\n", c->gc_task->pid);
     67		send_sig(SIGKILL, c->gc_task, 1);
     68		wait = 1;
     69	}
     70	spin_unlock(&c->erase_completion_lock);
     71	if (wait)
     72		wait_for_completion(&c->gc_thread_exit);
     73}
     74
     75static int jffs2_garbage_collect_thread(void *_c)
     76{
     77	struct jffs2_sb_info *c = _c;
     78	sigset_t hupmask;
     79
     80	siginitset(&hupmask, sigmask(SIGHUP));
     81	allow_signal(SIGKILL);
     82	allow_signal(SIGSTOP);
     83	allow_signal(SIGHUP);
     84
     85	c->gc_task = current;
     86	complete(&c->gc_thread_start);
     87
     88	set_user_nice(current, 10);
     89
     90	set_freezable();
     91	for (;;) {
     92		sigprocmask(SIG_UNBLOCK, &hupmask, NULL);
     93	again:
     94		spin_lock(&c->erase_completion_lock);
     95		if (!jffs2_thread_should_wake(c)) {
     96			set_current_state (TASK_INTERRUPTIBLE);
     97			spin_unlock(&c->erase_completion_lock);
     98			jffs2_dbg(1, "%s(): sleeping...\n", __func__);
     99			schedule();
    100		} else {
    101			spin_unlock(&c->erase_completion_lock);
    102		}
    103		/* Problem - immediately after bootup, the GCD spends a lot
    104		 * of time in places like jffs2_kill_fragtree(); so much so
    105		 * that userspace processes (like gdm and X) are starved
    106		 * despite plenty of cond_resched()s and renicing.  Yield()
    107		 * doesn't help, either (presumably because userspace and GCD
    108		 * are generally competing for a higher latency resource -
    109		 * disk).
    110		 * This forces the GCD to slow the hell down.   Pulling an
    111		 * inode in with read_inode() is much preferable to having
    112		 * the GC thread get there first. */
    113		schedule_timeout_interruptible(msecs_to_jiffies(50));
    114
    115		if (kthread_should_stop()) {
    116			jffs2_dbg(1, "%s(): kthread_stop() called\n", __func__);
    117			goto die;
    118		}
    119
    120		/* Put_super will send a SIGKILL and then wait on the sem.
    121		 */
    122		while (signal_pending(current) || freezing(current)) {
    123			unsigned long signr;
    124
    125			if (try_to_freeze())
    126				goto again;
    127
    128			signr = kernel_dequeue_signal();
    129
    130			switch(signr) {
    131			case SIGSTOP:
    132				jffs2_dbg(1, "%s(): SIGSTOP received\n",
    133					  __func__);
    134				kernel_signal_stop();
    135				break;
    136
    137			case SIGKILL:
    138				jffs2_dbg(1, "%s(): SIGKILL received\n",
    139					  __func__);
    140				goto die;
    141
    142			case SIGHUP:
    143				jffs2_dbg(1, "%s(): SIGHUP received\n",
    144					  __func__);
    145				break;
    146			default:
    147				jffs2_dbg(1, "%s(): signal %ld received\n",
    148					  __func__, signr);
    149			}
    150		}
    151		/* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
    152		sigprocmask(SIG_BLOCK, &hupmask, NULL);
    153
    154		jffs2_dbg(1, "%s(): pass\n", __func__);
    155		if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
    156			pr_notice("No space for garbage collection. Aborting GC thread\n");
    157			goto die;
    158		}
    159	}
    160 die:
    161	spin_lock(&c->erase_completion_lock);
    162	c->gc_task = NULL;
    163	spin_unlock(&c->erase_completion_lock);
    164	kthread_complete_and_exit(&c->gc_thread_exit, 0);
    165}