![Todd Poynor](/assets/img/avatar_default.png)
If kcalloc() returns NULL in put_mapping(), continue to clean up state, including dropping the reference on the struct device and free attribute memory. Signed-off-by: Todd Poynor <toddpoynor@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
401 lines
10 KiB
C
401 lines
10 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Copyright (C) 2018 Google, Inc. */
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#include "gasket_sysfs.h"
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#include "gasket_core.h"
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#include <linux/device.h>
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#include <linux/printk.h>
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/*
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* Pair of kernel device and user-specified pointer. Used in lookups in sysfs
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* "show" functions to return user data.
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*/
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struct gasket_sysfs_mapping {
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/*
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* The device bound to this mapping. If this is NULL, then this mapping
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* is free.
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*/
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struct device *device;
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/* The Gasket descriptor for this device. */
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struct gasket_dev *gasket_dev;
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/* This device's set of sysfs attributes/nodes. */
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struct gasket_sysfs_attribute *attributes;
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/* The number of live elements in "attributes". */
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int attribute_count;
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/* Protects structure from simultaneous access. */
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struct mutex mutex;
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/* Tracks active users of this mapping. */
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struct kref refcount;
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};
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/*
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* Data needed to manage users of this sysfs utility.
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* Currently has a fixed size; if space is a concern, this can be dynamically
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* allocated.
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*/
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/*
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* 'Global' (file-scoped) list of mappings between devices and gasket_data
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* pointers. This removes the requirement to have a gasket_sysfs_data
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* handle in all files.
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*/
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static struct gasket_sysfs_mapping dev_mappings[GASKET_SYSFS_NUM_MAPPINGS];
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/* Callback when a mapping's refcount goes to zero. */
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static void release_entry(struct kref *ref)
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{
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/* All work is done after the return from kref_put. */
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}
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/* Look up mapping information for the given device. */
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static struct gasket_sysfs_mapping *get_mapping(struct device *device)
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{
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int i;
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for (i = 0; i < GASKET_SYSFS_NUM_MAPPINGS; i++) {
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mutex_lock(&dev_mappings[i].mutex);
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if (dev_mappings[i].device == device) {
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kref_get(&dev_mappings[i].refcount);
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mutex_unlock(&dev_mappings[i].mutex);
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return &dev_mappings[i];
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}
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mutex_unlock(&dev_mappings[i].mutex);
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}
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dev_dbg(device, "%s: Mapping to device %s not found\n",
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__func__, device->kobj.name);
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return NULL;
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}
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/* Put a reference to a mapping. */
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static void put_mapping(struct gasket_sysfs_mapping *mapping)
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{
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int i;
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int num_files_to_remove = 0;
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struct device_attribute *files_to_remove;
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struct device *device;
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if (!mapping) {
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pr_debug("%s: Mapping should not be NULL\n", __func__);
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return;
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}
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mutex_lock(&mapping->mutex);
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if (kref_put(&mapping->refcount, release_entry)) {
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dev_dbg(mapping->device, "Removing Gasket sysfs mapping\n");
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/*
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* We can't remove the sysfs nodes in the kref callback, since
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* device_remove_file() blocks until the node is free.
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* Readers/writers of sysfs nodes, though, will be blocked on
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* the mapping mutex, resulting in deadlock. To fix this, the
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* sysfs nodes are removed outside the lock.
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*/
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device = mapping->device;
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num_files_to_remove = mapping->attribute_count;
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files_to_remove = kcalloc(num_files_to_remove,
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sizeof(*files_to_remove),
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GFP_KERNEL);
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if (files_to_remove)
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for (i = 0; i < num_files_to_remove; i++)
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files_to_remove[i] =
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mapping->attributes[i].attr;
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else
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num_files_to_remove = 0;
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kfree(mapping->attributes);
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mapping->attributes = NULL;
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mapping->attribute_count = 0;
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put_device(mapping->device);
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mapping->device = NULL;
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mapping->gasket_dev = NULL;
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}
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mutex_unlock(&mapping->mutex);
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if (num_files_to_remove != 0) {
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for (i = 0; i < num_files_to_remove; ++i)
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device_remove_file(device, &files_to_remove[i]);
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kfree(files_to_remove);
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}
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}
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/*
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* Put a reference to a mapping N times.
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*
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* In higher-level resource acquire/release function pairs, the release function
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* will need to release a mapping 2x - once for the refcount taken in the
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* release function itself, and once for the count taken in the acquire call.
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*/
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static void put_mapping_n(struct gasket_sysfs_mapping *mapping, int times)
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{
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int i;
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for (i = 0; i < times; i++)
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put_mapping(mapping);
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}
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void gasket_sysfs_init(void)
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{
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int i;
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for (i = 0; i < GASKET_SYSFS_NUM_MAPPINGS; i++) {
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dev_mappings[i].device = NULL;
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mutex_init(&dev_mappings[i].mutex);
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}
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}
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int gasket_sysfs_create_mapping(struct device *device,
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struct gasket_dev *gasket_dev)
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{
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struct gasket_sysfs_mapping *mapping;
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int map_idx = -1;
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/*
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* We need a function-level mutex to protect against the same device
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* being added [multiple times] simultaneously.
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*/
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static DEFINE_MUTEX(function_mutex);
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mutex_lock(&function_mutex);
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dev_dbg(device, "Creating sysfs entries for device\n");
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/* Check that the device we're adding hasn't already been added. */
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mapping = get_mapping(device);
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if (mapping) {
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dev_err(device,
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"Attempting to re-initialize sysfs mapping for device\n");
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put_mapping(mapping);
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mutex_unlock(&function_mutex);
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return -EBUSY;
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}
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/* Find the first empty entry in the array. */
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for (map_idx = 0; map_idx < GASKET_SYSFS_NUM_MAPPINGS; ++map_idx) {
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mutex_lock(&dev_mappings[map_idx].mutex);
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if (!dev_mappings[map_idx].device)
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/* Break with the mutex held! */
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break;
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mutex_unlock(&dev_mappings[map_idx].mutex);
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}
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if (map_idx == GASKET_SYSFS_NUM_MAPPINGS) {
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dev_err(device, "All mappings have been exhausted\n");
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mutex_unlock(&function_mutex);
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return -ENOMEM;
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}
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dev_dbg(device, "Creating sysfs mapping for device %s\n",
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device->kobj.name);
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mapping = &dev_mappings[map_idx];
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mapping->attributes = kcalloc(GASKET_SYSFS_MAX_NODES,
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sizeof(*mapping->attributes),
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GFP_KERNEL);
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if (!mapping->attributes) {
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dev_dbg(device, "Unable to allocate sysfs attribute array\n");
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mutex_unlock(&mapping->mutex);
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mutex_unlock(&function_mutex);
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return -ENOMEM;
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}
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kref_init(&mapping->refcount);
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mapping->device = get_device(device);
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mapping->gasket_dev = gasket_dev;
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mapping->attribute_count = 0;
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mutex_unlock(&mapping->mutex);
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mutex_unlock(&function_mutex);
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/* Don't decrement the refcount here! One open count keeps it alive! */
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return 0;
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}
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int gasket_sysfs_create_entries(struct device *device,
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const struct gasket_sysfs_attribute *attrs)
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{
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int i;
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int ret;
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struct gasket_sysfs_mapping *mapping = get_mapping(device);
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if (!mapping) {
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dev_dbg(device,
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"Creating entries for device without first "
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"initializing mapping\n");
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return -EINVAL;
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}
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mutex_lock(&mapping->mutex);
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for (i = 0; strcmp(attrs[i].attr.attr.name, GASKET_ARRAY_END_MARKER);
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i++) {
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if (mapping->attribute_count == GASKET_SYSFS_MAX_NODES) {
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dev_err(device,
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"Maximum number of sysfs nodes reached for "
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"device\n");
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mutex_unlock(&mapping->mutex);
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put_mapping(mapping);
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return -ENOMEM;
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}
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ret = device_create_file(device, &attrs[i].attr);
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if (ret) {
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dev_dbg(device, "Unable to create device entries\n");
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mutex_unlock(&mapping->mutex);
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put_mapping(mapping);
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return ret;
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}
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mapping->attributes[mapping->attribute_count] = attrs[i];
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++mapping->attribute_count;
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}
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mutex_unlock(&mapping->mutex);
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put_mapping(mapping);
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return 0;
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}
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EXPORT_SYMBOL(gasket_sysfs_create_entries);
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void gasket_sysfs_remove_mapping(struct device *device)
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{
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struct gasket_sysfs_mapping *mapping = get_mapping(device);
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if (!mapping) {
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dev_err(device,
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"Attempted to remove non-existent sysfs mapping to "
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"device\n");
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return;
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}
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put_mapping_n(mapping, 2);
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}
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struct gasket_dev *gasket_sysfs_get_device_data(struct device *device)
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{
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struct gasket_sysfs_mapping *mapping = get_mapping(device);
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if (!mapping) {
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dev_err(device, "device not registered\n");
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return NULL;
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}
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return mapping->gasket_dev;
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}
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EXPORT_SYMBOL(gasket_sysfs_get_device_data);
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void gasket_sysfs_put_device_data(struct device *device, struct gasket_dev *dev)
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{
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struct gasket_sysfs_mapping *mapping = get_mapping(device);
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if (!mapping)
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return;
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/* See comment of put_mapping_n() for why the '2' is necessary. */
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put_mapping_n(mapping, 2);
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}
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EXPORT_SYMBOL(gasket_sysfs_put_device_data);
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struct gasket_sysfs_attribute *
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gasket_sysfs_get_attr(struct device *device, struct device_attribute *attr)
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{
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int i;
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int num_attrs;
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struct gasket_sysfs_mapping *mapping = get_mapping(device);
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struct gasket_sysfs_attribute *attrs = NULL;
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if (!mapping)
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return NULL;
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attrs = mapping->attributes;
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num_attrs = mapping->attribute_count;
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for (i = 0; i < num_attrs; ++i) {
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if (!strcmp(attrs[i].attr.attr.name, attr->attr.name))
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return &attrs[i];
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}
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dev_err(device, "Unable to find match for device_attribute %s\n",
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attr->attr.name);
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return NULL;
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}
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EXPORT_SYMBOL(gasket_sysfs_get_attr);
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void gasket_sysfs_put_attr(struct device *device,
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struct gasket_sysfs_attribute *attr)
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{
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int i;
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int num_attrs;
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struct gasket_sysfs_mapping *mapping = get_mapping(device);
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struct gasket_sysfs_attribute *attrs = NULL;
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if (!mapping)
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return;
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attrs = mapping->attributes;
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num_attrs = mapping->attribute_count;
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for (i = 0; i < num_attrs; ++i) {
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if (&attrs[i] == attr) {
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put_mapping_n(mapping, 2);
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return;
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}
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}
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dev_err(device, "Unable to put unknown attribute: %s\n",
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attr->attr.attr.name);
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}
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EXPORT_SYMBOL(gasket_sysfs_put_attr);
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ssize_t gasket_sysfs_register_store(struct device *device,
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struct device_attribute *attr,
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const char *buf, size_t count)
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{
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ulong parsed_value = 0;
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struct gasket_sysfs_mapping *mapping;
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struct gasket_dev *gasket_dev;
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struct gasket_sysfs_attribute *gasket_attr;
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if (count < 3 || buf[0] != '0' || buf[1] != 'x') {
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dev_err(device,
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"sysfs register write format: \"0x<hex value>\"\n");
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return -EINVAL;
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}
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if (kstrtoul(buf, 16, &parsed_value) != 0) {
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dev_err(device,
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"Unable to parse input as 64-bit hex value: %s\n", buf);
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return -EINVAL;
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}
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mapping = get_mapping(device);
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if (!mapping) {
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dev_err(device, "Device driver may have been removed\n");
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return 0;
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}
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gasket_dev = mapping->gasket_dev;
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if (!gasket_dev) {
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dev_err(device, "Device driver may have been removed\n");
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return 0;
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}
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gasket_attr = gasket_sysfs_get_attr(device, attr);
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if (!gasket_attr) {
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put_mapping(mapping);
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return count;
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}
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gasket_dev_write_64(gasket_dev, parsed_value,
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gasket_attr->data.bar_address.bar,
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gasket_attr->data.bar_address.offset);
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if (gasket_attr->write_callback)
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gasket_attr->write_callback(gasket_dev, gasket_attr,
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parsed_value);
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gasket_sysfs_put_attr(device, gasket_attr);
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put_mapping(mapping);
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return count;
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}
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EXPORT_SYMBOL(gasket_sysfs_register_store);
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