linux/drivers/gpu/drm/drm_debugfs.c
Desmond Cheong Zhi Xi 5eff9585de drm: avoid blocking in drm_clients_info's rcu section
Inside drm_clients_info, the rcu_read_lock is held to lock
pid_task()->comm. However, within this protected section, a call to
drm_is_current_master is made, which involves a mutex lock in a future
patch. However, this is illegal because the mutex lock might block
while in the RCU read-side critical section.

Since drm_is_current_master isn't protected by rcu_read_lock, we avoid
this by moving it out of the RCU critical section.

The following report came from intel-gfx ci's
igt@debugfs_test@read_all_entries testcase:

=============================
[ BUG: Invalid wait context ]
5.13.0-CI-Patchwork_20515+ #1 Tainted: G        W
-----------------------------
debugfs_test/1101 is trying to lock:
ffff888132d901a8 (&dev->master_mutex){+.+.}-{3:3}, at:
drm_is_current_master+0x1e/0x50
other info that might help us debug this:
context-{4:4}
3 locks held by debugfs_test/1101:
 #0: ffff88810fdffc90 (&p->lock){+.+.}-{3:3}, at:
 seq_read_iter+0x53/0x3b0
 #1: ffff888132d90240 (&dev->filelist_mutex){+.+.}-{3:3}, at:
 drm_clients_info+0x63/0x2a0
 #2: ffffffff82734220 (rcu_read_lock){....}-{1:2}, at:
 drm_clients_info+0x1b1/0x2a0
stack backtrace:
CPU: 8 PID: 1101 Comm: debugfs_test Tainted: G        W
5.13.0-CI-Patchwork_20515+ #1
Hardware name: Intel Corporation CometLake Client Platform/CometLake S
UDIMM (ERB/CRB), BIOS CMLSFWR1.R00.1263.D00.1906260926 06/26/2019
Call Trace:
 dump_stack+0x7f/0xad
 __lock_acquire.cold.78+0x2af/0x2ca
 lock_acquire+0xd3/0x300
 ? drm_is_current_master+0x1e/0x50
 ? __mutex_lock+0x76/0x970
 ? lockdep_hardirqs_on+0xbf/0x130
 __mutex_lock+0xab/0x970
 ? drm_is_current_master+0x1e/0x50
 ? drm_is_current_master+0x1e/0x50
 ? drm_is_current_master+0x1e/0x50
 drm_is_current_master+0x1e/0x50
 drm_clients_info+0x107/0x2a0
 seq_read_iter+0x178/0x3b0
 seq_read+0x104/0x150
 full_proxy_read+0x4e/0x80
 vfs_read+0xa5/0x1b0
 ksys_read+0x5a/0xd0
 do_syscall_64+0x39/0xb0
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210712043508.11584-3-desmondcheongzx@gmail.com
2021-07-20 20:14:42 +02:00

476 lines
12 KiB
C

/*
* Created: Sun Dec 21 13:08:50 2008 by bgamari@gmail.com
*
* Copyright 2008 Ben Gamari <bgamari@gmail.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#include <linux/debugfs.h>
#include <linux/export.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <drm/drm_atomic.h>
#include <drm/drm_auth.h>
#include <drm/drm_client.h>
#include <drm/drm_debugfs.h>
#include <drm/drm_device.h>
#include <drm/drm_drv.h>
#include <drm/drm_edid.h>
#include <drm/drm_file.h>
#include <drm/drm_gem.h>
#include "drm_crtc_internal.h"
#include "drm_internal.h"
#if defined(CONFIG_DEBUG_FS)
/***************************************************
* Initialization, etc.
**************************************************/
static int drm_name_info(struct seq_file *m, void *data)
{
struct drm_info_node *node = (struct drm_info_node *) m->private;
struct drm_minor *minor = node->minor;
struct drm_device *dev = minor->dev;
struct drm_master *master;
mutex_lock(&dev->master_mutex);
master = dev->master;
seq_printf(m, "%s", dev->driver->name);
if (dev->dev)
seq_printf(m, " dev=%s", dev_name(dev->dev));
if (master && master->unique)
seq_printf(m, " master=%s", master->unique);
if (dev->unique)
seq_printf(m, " unique=%s", dev->unique);
seq_printf(m, "\n");
mutex_unlock(&dev->master_mutex);
return 0;
}
static int drm_clients_info(struct seq_file *m, void *data)
{
struct drm_info_node *node = (struct drm_info_node *) m->private;
struct drm_device *dev = node->minor->dev;
struct drm_file *priv;
kuid_t uid;
seq_printf(m,
"%20s %5s %3s master a %5s %10s\n",
"command",
"pid",
"dev",
"uid",
"magic");
/* dev->filelist is sorted youngest first, but we want to present
* oldest first (i.e. kernel, servers, clients), so walk backwardss.
*/
mutex_lock(&dev->filelist_mutex);
list_for_each_entry_reverse(priv, &dev->filelist, lhead) {
struct task_struct *task;
bool is_current_master = drm_is_current_master(priv);
rcu_read_lock(); /* locks pid_task()->comm */
task = pid_task(priv->pid, PIDTYPE_PID);
uid = task ? __task_cred(task)->euid : GLOBAL_ROOT_UID;
seq_printf(m, "%20s %5d %3d %c %c %5d %10u\n",
task ? task->comm : "<unknown>",
pid_vnr(priv->pid),
priv->minor->index,
is_current_master ? 'y' : 'n',
priv->authenticated ? 'y' : 'n',
from_kuid_munged(seq_user_ns(m), uid),
priv->magic);
rcu_read_unlock();
}
mutex_unlock(&dev->filelist_mutex);
return 0;
}
static int drm_gem_one_name_info(int id, void *ptr, void *data)
{
struct drm_gem_object *obj = ptr;
struct seq_file *m = data;
seq_printf(m, "%6d %8zd %7d %8d\n",
obj->name, obj->size,
obj->handle_count,
kref_read(&obj->refcount));
return 0;
}
static int drm_gem_name_info(struct seq_file *m, void *data)
{
struct drm_info_node *node = (struct drm_info_node *) m->private;
struct drm_device *dev = node->minor->dev;
seq_printf(m, " name size handles refcount\n");
mutex_lock(&dev->object_name_lock);
idr_for_each(&dev->object_name_idr, drm_gem_one_name_info, m);
mutex_unlock(&dev->object_name_lock);
return 0;
}
static const struct drm_info_list drm_debugfs_list[] = {
{"name", drm_name_info, 0},
{"clients", drm_clients_info, 0},
{"gem_names", drm_gem_name_info, DRIVER_GEM},
};
#define DRM_DEBUGFS_ENTRIES ARRAY_SIZE(drm_debugfs_list)
static int drm_debugfs_open(struct inode *inode, struct file *file)
{
struct drm_info_node *node = inode->i_private;
return single_open(file, node->info_ent->show, node);
}
static const struct file_operations drm_debugfs_fops = {
.owner = THIS_MODULE,
.open = drm_debugfs_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
/**
* drm_debugfs_create_files - Initialize a given set of debugfs files for DRM
* minor
* @files: The array of files to create
* @count: The number of files given
* @root: DRI debugfs dir entry.
* @minor: device minor number
*
* Create a given set of debugfs files represented by an array of
* &struct drm_info_list in the given root directory. These files will be removed
* automatically on drm_debugfs_cleanup().
*/
void drm_debugfs_create_files(const struct drm_info_list *files, int count,
struct dentry *root, struct drm_minor *minor)
{
struct drm_device *dev = minor->dev;
struct drm_info_node *tmp;
int i;
for (i = 0; i < count; i++) {
u32 features = files[i].driver_features;
if (features && !drm_core_check_all_features(dev, features))
continue;
tmp = kmalloc(sizeof(struct drm_info_node), GFP_KERNEL);
if (tmp == NULL)
continue;
tmp->minor = minor;
tmp->dent = debugfs_create_file(files[i].name,
S_IFREG | S_IRUGO, root, tmp,
&drm_debugfs_fops);
tmp->info_ent = &files[i];
mutex_lock(&minor->debugfs_lock);
list_add(&tmp->list, &minor->debugfs_list);
mutex_unlock(&minor->debugfs_lock);
}
}
EXPORT_SYMBOL(drm_debugfs_create_files);
int drm_debugfs_init(struct drm_minor *minor, int minor_id,
struct dentry *root)
{
struct drm_device *dev = minor->dev;
char name[64];
INIT_LIST_HEAD(&minor->debugfs_list);
mutex_init(&minor->debugfs_lock);
sprintf(name, "%d", minor_id);
minor->debugfs_root = debugfs_create_dir(name, root);
drm_debugfs_create_files(drm_debugfs_list, DRM_DEBUGFS_ENTRIES,
minor->debugfs_root, minor);
if (drm_drv_uses_atomic_modeset(dev)) {
drm_atomic_debugfs_init(minor);
}
if (drm_core_check_feature(dev, DRIVER_MODESET)) {
drm_framebuffer_debugfs_init(minor);
drm_client_debugfs_init(minor);
}
if (dev->driver->debugfs_init)
dev->driver->debugfs_init(minor);
return 0;
}
int drm_debugfs_remove_files(const struct drm_info_list *files, int count,
struct drm_minor *minor)
{
struct list_head *pos, *q;
struct drm_info_node *tmp;
int i;
mutex_lock(&minor->debugfs_lock);
for (i = 0; i < count; i++) {
list_for_each_safe(pos, q, &minor->debugfs_list) {
tmp = list_entry(pos, struct drm_info_node, list);
if (tmp->info_ent == &files[i]) {
debugfs_remove(tmp->dent);
list_del(pos);
kfree(tmp);
}
}
}
mutex_unlock(&minor->debugfs_lock);
return 0;
}
EXPORT_SYMBOL(drm_debugfs_remove_files);
static void drm_debugfs_remove_all_files(struct drm_minor *minor)
{
struct drm_info_node *node, *tmp;
mutex_lock(&minor->debugfs_lock);
list_for_each_entry_safe(node, tmp, &minor->debugfs_list, list) {
debugfs_remove(node->dent);
list_del(&node->list);
kfree(node);
}
mutex_unlock(&minor->debugfs_lock);
}
void drm_debugfs_cleanup(struct drm_minor *minor)
{
if (!minor->debugfs_root)
return;
drm_debugfs_remove_all_files(minor);
debugfs_remove_recursive(minor->debugfs_root);
minor->debugfs_root = NULL;
}
static int connector_show(struct seq_file *m, void *data)
{
struct drm_connector *connector = m->private;
seq_printf(m, "%s\n", drm_get_connector_force_name(connector->force));
return 0;
}
static int connector_open(struct inode *inode, struct file *file)
{
struct drm_connector *dev = inode->i_private;
return single_open(file, connector_show, dev);
}
static ssize_t connector_write(struct file *file, const char __user *ubuf,
size_t len, loff_t *offp)
{
struct seq_file *m = file->private_data;
struct drm_connector *connector = m->private;
char buf[12];
if (len > sizeof(buf) - 1)
return -EINVAL;
if (copy_from_user(buf, ubuf, len))
return -EFAULT;
buf[len] = '\0';
if (sysfs_streq(buf, "on"))
connector->force = DRM_FORCE_ON;
else if (sysfs_streq(buf, "digital"))
connector->force = DRM_FORCE_ON_DIGITAL;
else if (sysfs_streq(buf, "off"))
connector->force = DRM_FORCE_OFF;
else if (sysfs_streq(buf, "unspecified"))
connector->force = DRM_FORCE_UNSPECIFIED;
else
return -EINVAL;
return len;
}
static int edid_show(struct seq_file *m, void *data)
{
struct drm_connector *connector = m->private;
struct drm_property_blob *edid = connector->edid_blob_ptr;
if (connector->override_edid && edid)
seq_write(m, edid->data, edid->length);
return 0;
}
static int edid_open(struct inode *inode, struct file *file)
{
struct drm_connector *dev = inode->i_private;
return single_open(file, edid_show, dev);
}
static ssize_t edid_write(struct file *file, const char __user *ubuf,
size_t len, loff_t *offp)
{
struct seq_file *m = file->private_data;
struct drm_connector *connector = m->private;
char *buf;
struct edid *edid;
int ret;
buf = memdup_user(ubuf, len);
if (IS_ERR(buf))
return PTR_ERR(buf);
edid = (struct edid *) buf;
if (len == 5 && !strncmp(buf, "reset", 5)) {
connector->override_edid = false;
ret = drm_connector_update_edid_property(connector, NULL);
} else if (len < EDID_LENGTH ||
EDID_LENGTH * (1 + edid->extensions) > len)
ret = -EINVAL;
else {
connector->override_edid = false;
ret = drm_connector_update_edid_property(connector, edid);
if (!ret)
connector->override_edid = true;
}
kfree(buf);
return (ret) ? ret : len;
}
/*
* Returns the min and max vrr vfreq through the connector's debugfs file.
* Example usage: cat /sys/kernel/debug/dri/0/DP-1/vrr_range
*/
static int vrr_range_show(struct seq_file *m, void *data)
{
struct drm_connector *connector = m->private;
if (connector->status != connector_status_connected)
return -ENODEV;
seq_printf(m, "Min: %u\n", (u8)connector->display_info.monitor_range.min_vfreq);
seq_printf(m, "Max: %u\n", (u8)connector->display_info.monitor_range.max_vfreq);
return 0;
}
DEFINE_SHOW_ATTRIBUTE(vrr_range);
static const struct file_operations drm_edid_fops = {
.owner = THIS_MODULE,
.open = edid_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
.write = edid_write
};
static const struct file_operations drm_connector_fops = {
.owner = THIS_MODULE,
.open = connector_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
.write = connector_write
};
void drm_debugfs_connector_add(struct drm_connector *connector)
{
struct drm_minor *minor = connector->dev->primary;
struct dentry *root;
if (!minor->debugfs_root)
return;
root = debugfs_create_dir(connector->name, minor->debugfs_root);
connector->debugfs_entry = root;
/* force */
debugfs_create_file("force", S_IRUGO | S_IWUSR, root, connector,
&drm_connector_fops);
/* edid */
debugfs_create_file("edid_override", S_IRUGO | S_IWUSR, root, connector,
&drm_edid_fops);
/* vrr range */
debugfs_create_file("vrr_range", S_IRUGO, root, connector,
&vrr_range_fops);
}
void drm_debugfs_connector_remove(struct drm_connector *connector)
{
if (!connector->debugfs_entry)
return;
debugfs_remove_recursive(connector->debugfs_entry);
connector->debugfs_entry = NULL;
}
void drm_debugfs_crtc_add(struct drm_crtc *crtc)
{
struct drm_minor *minor = crtc->dev->primary;
struct dentry *root;
char *name;
name = kasprintf(GFP_KERNEL, "crtc-%d", crtc->index);
if (!name)
return;
root = debugfs_create_dir(name, minor->debugfs_root);
kfree(name);
crtc->debugfs_entry = root;
drm_debugfs_crtc_crc_add(crtc);
}
void drm_debugfs_crtc_remove(struct drm_crtc *crtc)
{
debugfs_remove_recursive(crtc->debugfs_entry);
crtc->debugfs_entry = NULL;
}
#endif /* CONFIG_DEBUG_FS */