/* Copyright (C) 2010-2017  B.A.T.M.A.N. contributors:
 *
 * Marek Lindner
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 */

#include "log.h"
#include "main.h"

#include <linux/compiler.h>
#include <linux/debugfs.h>
#include <linux/errno.h>
#include <linux/export.h>
#include <linux/fcntl.h>
#include <linux/fs.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/sched.h> /* for linux/wait.h */
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/stddef.h>
#include <linux/types.h>
#include <linux/uaccess.h>
#include <linux/wait.h>
#include <stdarg.h>

#define BATADV_LOG_BUFF_MASK (batadv_log_buff_len - 1)

static const int batadv_log_buff_len = BATADV_LOG_BUF_LEN;

static char *batadv_log_char_addr(struct batadv_priv_debug_log *debug_log,
				  size_t idx)
{
	return &debug_log->log_buff[idx & BATADV_LOG_BUFF_MASK];
}

static void batadv_emit_log_char(struct batadv_priv_debug_log *debug_log,
				 char c)
{
	char *char_addr;

	char_addr = batadv_log_char_addr(debug_log, debug_log->log_end);
	*char_addr = c;
	debug_log->log_end++;

	if (debug_log->log_end - debug_log->log_start > batadv_log_buff_len)
		debug_log->log_start = debug_log->log_end - batadv_log_buff_len;
}

__printf(2, 3)
static int batadv_fdebug_log(struct batadv_priv_debug_log *debug_log,
			     const char *fmt, ...)
{
	va_list args;
	static char debug_log_buf[256];
	char *p;

	if (!debug_log)
		return 0;

	spin_lock_bh(&debug_log->lock);
	va_start(args, fmt);
	vscnprintf(debug_log_buf, sizeof(debug_log_buf), fmt, args);
	va_end(args);

	for (p = debug_log_buf; *p != 0; p++)
		batadv_emit_log_char(debug_log, *p);

	spin_unlock_bh(&debug_log->lock);

	wake_up(&debug_log->queue_wait);

	return 0;
}

int batadv_debug_log(struct batadv_priv *bat_priv, const char *fmt, ...)
{
	va_list args;
	char tmp_log_buf[256];

	va_start(args, fmt);
	vscnprintf(tmp_log_buf, sizeof(tmp_log_buf), fmt, args);
	batadv_fdebug_log(bat_priv->debug_log, "[%10u] %s",
			  jiffies_to_msecs(jiffies), tmp_log_buf);
	va_end(args);

	return 0;
}

static int batadv_log_open(struct inode *inode, struct file *file)
{
	if (!try_module_get(THIS_MODULE))
		return -EBUSY;

	nonseekable_open(inode, file);
	file->private_data = inode->i_private;
	return 0;
}

static int batadv_log_release(struct inode *inode, struct file *file)
{
	module_put(THIS_MODULE);
	return 0;
}

static bool batadv_log_empty(struct batadv_priv_debug_log *debug_log)
{
	return !(debug_log->log_start - debug_log->log_end);
}

static ssize_t batadv_log_read(struct file *file, char __user *buf,
			       size_t count, loff_t *ppos)
{
	struct batadv_priv *bat_priv = file->private_data;
	struct batadv_priv_debug_log *debug_log = bat_priv->debug_log;
	int error, i = 0;
	char *char_addr;
	char c;

	if ((file->f_flags & O_NONBLOCK) && batadv_log_empty(debug_log))
		return -EAGAIN;

	if (!buf)
		return -EINVAL;

	if (count == 0)
		return 0;

	if (!access_ok(VERIFY_WRITE, buf, count))
		return -EFAULT;

	error = wait_event_interruptible(debug_log->queue_wait,
					 (!batadv_log_empty(debug_log)));

	if (error)
		return error;

	spin_lock_bh(&debug_log->lock);

	while ((!error) && (i < count) &&
	       (debug_log->log_start != debug_log->log_end)) {
		char_addr = batadv_log_char_addr(debug_log,
						 debug_log->log_start);
		c = *char_addr;

		debug_log->log_start++;

		spin_unlock_bh(&debug_log->lock);

		error = __put_user(c, buf);

		spin_lock_bh(&debug_log->lock);

		buf++;
		i++;
	}

	spin_unlock_bh(&debug_log->lock);

	if (!error)
		return i;

	return error;
}

static unsigned int batadv_log_poll(struct file *file, poll_table *wait)
{
	struct batadv_priv *bat_priv = file->private_data;
	struct batadv_priv_debug_log *debug_log = bat_priv->debug_log;

	poll_wait(file, &debug_log->queue_wait, wait);

	if (!batadv_log_empty(debug_log))
		return POLLIN | POLLRDNORM;

	return 0;
}

static const struct file_operations batadv_log_fops = {
	.open           = batadv_log_open,
	.release        = batadv_log_release,
	.read           = batadv_log_read,
	.poll           = batadv_log_poll,
	.llseek         = no_llseek,
};

int batadv_debug_log_setup(struct batadv_priv *bat_priv)
{
	struct dentry *d;

	if (!bat_priv->debug_dir)
		goto err;

	bat_priv->debug_log = kzalloc(sizeof(*bat_priv->debug_log), GFP_ATOMIC);
	if (!bat_priv->debug_log)
		goto err;

	spin_lock_init(&bat_priv->debug_log->lock);
	init_waitqueue_head(&bat_priv->debug_log->queue_wait);

	d = debugfs_create_file("log", 0400, bat_priv->debug_dir, bat_priv,
				&batadv_log_fops);
	if (!d)
		goto err;

	return 0;

err:
	return -ENOMEM;
}

void batadv_debug_log_cleanup(struct batadv_priv *bat_priv)
{
	kfree(bat_priv->debug_log);
	bat_priv->debug_log = NULL;
}
/tree/net/rds/ib_fmr.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>net/rds/ib_fmr.c</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/net/rds/ib_fmr.c?id=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>2c5d9555d6d937966d79d4c6529a5f7b9206e405</a> (<a href='/cgit.cgi/linux/net-next.git/diff/net/rds/ib_fmr.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e&amp;id2=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>diff</a>)</td></tr></table>
<div class='commit-subject'>drm/i915: Check for NULL i915_vma in intel_unpin_fb_obj()</div><div class='commit-msg'>I've seen this trigger twice now, where the i915_gem_object_to_ggtt()
call in intel_unpin_fb_obj() returns NULL, resulting in an oops
immediately afterwards as the (inlined) call to i915_vma_unpin_fence()
tries to dereference it.

It seems to be some race condition where the object is going away at
shutdown time, since both times happened when shutting down the X
server.  The call chains were different:

 - VT ioctl(KDSETMODE, KD_TEXT):

    intel_cleanup_plane_fb+0x5b/0xa0 [i915]
    drm_atomic_helper_cleanup_planes+0x6f/0x90 [drm_kms_helper]
    intel_atomic_commit_tail+0x749/0xfe0 [i915]
    intel_atomic_commit+0x3cb/0x4f0 [i915]
    drm_atomic_commit+0x4b/0x50 [drm]
    restore_fbdev_mode+0x14c/0x2a0 [drm_kms_helper]
    drm_fb_helper_restore_fbdev_mode_unlocked+0x34/0x80 [drm_kms_helper]
    drm_fb_helper_set_par+0x2d/0x60 [drm_kms_helper]
    intel_fbdev_set_par+0x18/0x70 [i915]
    fb_set_var+0x236/0x460
    fbcon_blank+0x30f/0x350
    do_unblank_screen+0xd2/0x1a0
    vt_ioctl+0x507/0x12a0
    tty_ioctl+0x355/0xc30
    do_vfs_ioctl+0xa3/0x5e0
    SyS_ioctl+0x79/0x90
    entry_SYSCALL_64_fastpath+0x13/0x94

 - i915 unpin_work workqueue:

    intel_unpin_work_fn+0x58/0x140 [i915]
    process_one_work+0x1f1/0x480
    worker_thread+0x48/0x4d0
    kthread+0x101/0x140

and this patch purely papers over the issue by adding a NULL pointer
check and a WARN_ON_ONCE() to avoid the oops that would then generally
make the machine unresponsive.

Other callers of i915_gem_object_to_ggtt() seem to also check for the
returned pointer being NULL and warn about it, so this clearly has
happened before in other places.

[ Reported it originally to the i915 developers on Jan 8, applying the
  ugly workaround on my own now after triggering the problem for the
  second time with no feedback.

  This is likely to be the same bug reported as

     https://bugs.freedesktop.org/show_bug.cgi?id=98829
     https://bugs.freedesktop.org/show_bug.cgi?id=99134

  which has a patch for the underlying problem, but it hasn't gotten to
  me, so I'm applying the workaround. ]

Cc: Daniel Vetter &lt;daniel.vetter@intel.com&gt;
Cc: Jani Nikula &lt;jani.nikula@linux.intel.com&gt;
Cc: Ville Syrjälä &lt;ville.syrjala@linux.intel.com&gt;
Cc: Chris Wilson &lt;chris@chris-wilson.co.uk&gt;
Cc: Maarten Lankhorst &lt;maarten.lankhorst@linux.intel.com&gt;
Cc: Tvrtko Ursulin &lt;tvrtko.ursulin@intel.com&gt;
Cc: Imre Deak &lt;imre.deak@intel.com&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>Diffstat</a> (limited to 'net/rds/ib_fmr.c')</div><table summary='diffstat' class='diffstat'>