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![Lukas Wunner](/assets/img/avatar_default.png)
When a hotplug driver calls pci_hp_register(), all steps necessary for registration are carried out in one go, including creation of a kobject and addition to sysfs. That's a problem for pciehp once it's converted to enable/disable the slot exclusively from the IRQ thread: The thread needs to be spawned after creation of the kobject (because it uses the kobject's name), but before addition to sysfs (because it will handle enable/disable requests submitted via sysfs). pci_hp_deregister() does offer a ->release callback that's invoked after deletion from sysfs and before destruction of the kobject. But because pci_hp_register() doesn't offer a counterpart, hotplug drivers' ->probe and ->remove code becomes asymmetric, which is error prone as recently discovered use-after-free bugs in pciehp's ->remove hook have shown. In a sense, this appears to be a case of the midlayer antipattern: "The core thesis of the "midlayer mistake" is that midlayers are bad and should not exist. That common functionality which it is so tempting to put in a midlayer should instead be provided as library routines which can [be] used, augmented, or ignored by each bottom level driver independently. Thus every subsystem that supports multiple implementations (or drivers) should provide a very thin top layer which calls directly into the bottom layer drivers, and a rich library of support code that eases the implementation of those drivers. This library is available to, but not forced upon, those drivers." -- Neil Brown (2009), https://lwn.net/Articles/336262/ The presence of midlayer traits in the PCI hotplug core might be ascribed to its age: When it was introduced in February 2002, the blessings of a library approach might not have been well known: https://git.kernel.org/tglx/history/c/a8a2069f432c For comparison, the driver core does offer split functions for creating a kobject (device_initialize()) and addition to sysfs (device_add()) as an alternative to carrying out everything at once (device_register()). This was introduced in October 2002: https://git.kernel.org/tglx/history/c/8b290eb19962 The odd ->release callback in the PCI hotplug core was added in 2003: https://git.kernel.org/tglx/history/c/69f8d663b595 Clearly, a library approach would not force every hotplug driver to implement a ->release callback, but rather allow the driver to remove the sysfs files, release its data structures and finally destroy the kobject. Alternatively, a driver may choose to remove everything with pci_hp_deregister(), then release its data structures. To this end, offer drivers pci_hp_initialize() and pci_hp_add() as a split-up version of pci_hp_register(). Likewise, offer pci_hp_del() and pci_hp_destroy() as a split-up version of pci_hp_deregister(). Eliminate the ->release callback and move its code into each driver's teardown routine. Declare pci_hp_deregister() void, in keeping with the usual kernel pattern that enablement can fail, but disablement cannot. It only returned an error if the caller passed in a NULL pointer or a slot which has never or is no longer registered or is sharing its name with another slot. Those would be bugs, so WARN about them. Few hotplug drivers actually checked the return value and those that did only printed a useless error message to dmesg. Remove that. For most drivers the conversion was straightforward since it doesn't matter whether the code in the ->release callback is executed before or after destruction of the kobject. But in the case of ibmphp, it was unclear to me whether setting slot_cur->ctrl and slot_cur->bus_on to NULL needs to happen before the kobject is destroyed, so I erred on the side of caution and ensured that the order stays the same. Another nontrivial case is pnv_php, I've found the list and kref logic difficult to understand, however my impression was that it is safe to delete the list element and drop the references until after the kobject is destroyed. Signed-off-by: Lukas Wunner <lukas@wunner.de> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com> # drivers/platform/x86 Cc: Rafael J. Wysocki <rjw@rjwysocki.net> Cc: Len Brown <lenb@kernel.org> Cc: Scott Murray <scott@spiteful.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Gavin Shan <gwshan@linux.vnet.ibm.com> Cc: Sebastian Ott <sebott@linux.vnet.ibm.com> Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com> Cc: Corentin Chary <corentin.chary@gmail.com> Cc: Darren Hart <dvhart@infradead.org> Cc: Andy Shevchenko <andy@infradead.org>
366 lines
9 KiB
C
366 lines
9 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* Standard Hot Plug Controller Driver
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*
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* Copyright (C) 1995,2001 Compaq Computer Corporation
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* Copyright (C) 2001 Greg Kroah-Hartman (greg@kroah.com)
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* Copyright (C) 2001 IBM Corp.
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* Copyright (C) 2003-2004 Intel Corporation
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*
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* All rights reserved.
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*
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* Send feedback to <greg@kroah.com>, <kristen.c.accardi@intel.com>
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*
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*/
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/kernel.h>
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#include <linux/types.h>
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#include <linux/slab.h>
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#include <linux/pci.h>
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#include "shpchp.h"
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/* Global variables */
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bool shpchp_debug;
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bool shpchp_poll_mode;
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int shpchp_poll_time;
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#define DRIVER_VERSION "0.4"
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#define DRIVER_AUTHOR "Dan Zink <dan.zink@compaq.com>, Greg Kroah-Hartman <greg@kroah.com>, Dely Sy <dely.l.sy@intel.com>"
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#define DRIVER_DESC "Standard Hot Plug PCI Controller Driver"
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MODULE_AUTHOR(DRIVER_AUTHOR);
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MODULE_DESCRIPTION(DRIVER_DESC);
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MODULE_LICENSE("GPL");
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module_param(shpchp_debug, bool, 0644);
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module_param(shpchp_poll_mode, bool, 0644);
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module_param(shpchp_poll_time, int, 0644);
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MODULE_PARM_DESC(shpchp_debug, "Debugging mode enabled or not");
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MODULE_PARM_DESC(shpchp_poll_mode, "Using polling mechanism for hot-plug events or not");
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MODULE_PARM_DESC(shpchp_poll_time, "Polling mechanism frequency, in seconds");
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#define SHPC_MODULE_NAME "shpchp"
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static int set_attention_status(struct hotplug_slot *slot, u8 value);
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static int enable_slot(struct hotplug_slot *slot);
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static int disable_slot(struct hotplug_slot *slot);
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static int get_power_status(struct hotplug_slot *slot, u8 *value);
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static int get_attention_status(struct hotplug_slot *slot, u8 *value);
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static int get_latch_status(struct hotplug_slot *slot, u8 *value);
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static int get_adapter_status(struct hotplug_slot *slot, u8 *value);
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static struct hotplug_slot_ops shpchp_hotplug_slot_ops = {
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.set_attention_status = set_attention_status,
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.enable_slot = enable_slot,
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.disable_slot = disable_slot,
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.get_power_status = get_power_status,
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.get_attention_status = get_attention_status,
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.get_latch_status = get_latch_status,
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.get_adapter_status = get_adapter_status,
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};
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static int init_slots(struct controller *ctrl)
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{
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struct slot *slot;
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struct hotplug_slot *hotplug_slot;
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struct hotplug_slot_info *info;
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char name[SLOT_NAME_SIZE];
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int retval;
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int i;
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for (i = 0; i < ctrl->num_slots; i++) {
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slot = kzalloc(sizeof(*slot), GFP_KERNEL);
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if (!slot) {
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retval = -ENOMEM;
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goto error;
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}
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hotplug_slot = kzalloc(sizeof(*hotplug_slot), GFP_KERNEL);
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if (!hotplug_slot) {
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retval = -ENOMEM;
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goto error_slot;
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}
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slot->hotplug_slot = hotplug_slot;
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info = kzalloc(sizeof(*info), GFP_KERNEL);
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if (!info) {
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retval = -ENOMEM;
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goto error_hpslot;
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}
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hotplug_slot->info = info;
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slot->hp_slot = i;
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slot->ctrl = ctrl;
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slot->bus = ctrl->pci_dev->subordinate->number;
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slot->device = ctrl->slot_device_offset + i;
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slot->hpc_ops = ctrl->hpc_ops;
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slot->number = ctrl->first_slot + (ctrl->slot_num_inc * i);
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slot->wq = alloc_workqueue("shpchp-%d", 0, 0, slot->number);
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if (!slot->wq) {
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retval = -ENOMEM;
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goto error_info;
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}
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mutex_init(&slot->lock);
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INIT_DELAYED_WORK(&slot->work, shpchp_queue_pushbutton_work);
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/* register this slot with the hotplug pci core */
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hotplug_slot->private = slot;
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snprintf(name, SLOT_NAME_SIZE, "%d", slot->number);
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hotplug_slot->ops = &shpchp_hotplug_slot_ops;
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ctrl_dbg(ctrl, "Registering domain:bus:dev=%04x:%02x:%02x hp_slot=%x sun=%x slot_device_offset=%x\n",
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pci_domain_nr(ctrl->pci_dev->subordinate),
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slot->bus, slot->device, slot->hp_slot, slot->number,
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ctrl->slot_device_offset);
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retval = pci_hp_register(slot->hotplug_slot,
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ctrl->pci_dev->subordinate, slot->device, name);
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if (retval) {
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ctrl_err(ctrl, "pci_hp_register failed with error %d\n",
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retval);
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goto error_slotwq;
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}
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get_power_status(hotplug_slot, &info->power_status);
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get_attention_status(hotplug_slot, &info->attention_status);
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get_latch_status(hotplug_slot, &info->latch_status);
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get_adapter_status(hotplug_slot, &info->adapter_status);
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list_add(&slot->slot_list, &ctrl->slot_list);
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}
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return 0;
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error_slotwq:
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destroy_workqueue(slot->wq);
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error_info:
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kfree(info);
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error_hpslot:
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kfree(hotplug_slot);
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error_slot:
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kfree(slot);
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error:
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return retval;
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}
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void cleanup_slots(struct controller *ctrl)
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{
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struct slot *slot, *next;
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list_for_each_entry_safe(slot, next, &ctrl->slot_list, slot_list) {
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list_del(&slot->slot_list);
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cancel_delayed_work(&slot->work);
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destroy_workqueue(slot->wq);
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pci_hp_deregister(slot->hotplug_slot);
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kfree(slot->hotplug_slot->info);
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kfree(slot->hotplug_slot);
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kfree(slot);
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}
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}
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/*
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* set_attention_status - Turns the Amber LED for a slot on, off or blink
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*/
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static int set_attention_status(struct hotplug_slot *hotplug_slot, u8 status)
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{
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struct slot *slot = get_slot(hotplug_slot);
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ctrl_dbg(slot->ctrl, "%s: physical_slot = %s\n",
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__func__, slot_name(slot));
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hotplug_slot->info->attention_status = status;
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slot->hpc_ops->set_attention_status(slot, status);
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return 0;
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}
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static int enable_slot(struct hotplug_slot *hotplug_slot)
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{
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struct slot *slot = get_slot(hotplug_slot);
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ctrl_dbg(slot->ctrl, "%s: physical_slot = %s\n",
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__func__, slot_name(slot));
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return shpchp_sysfs_enable_slot(slot);
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}
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static int disable_slot(struct hotplug_slot *hotplug_slot)
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{
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struct slot *slot = get_slot(hotplug_slot);
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ctrl_dbg(slot->ctrl, "%s: physical_slot = %s\n",
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__func__, slot_name(slot));
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return shpchp_sysfs_disable_slot(slot);
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}
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static int get_power_status(struct hotplug_slot *hotplug_slot, u8 *value)
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{
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struct slot *slot = get_slot(hotplug_slot);
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int retval;
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ctrl_dbg(slot->ctrl, "%s: physical_slot = %s\n",
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__func__, slot_name(slot));
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retval = slot->hpc_ops->get_power_status(slot, value);
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if (retval < 0)
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*value = hotplug_slot->info->power_status;
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return 0;
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}
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static int get_attention_status(struct hotplug_slot *hotplug_slot, u8 *value)
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{
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struct slot *slot = get_slot(hotplug_slot);
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int retval;
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ctrl_dbg(slot->ctrl, "%s: physical_slot = %s\n",
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__func__, slot_name(slot));
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retval = slot->hpc_ops->get_attention_status(slot, value);
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if (retval < 0)
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*value = hotplug_slot->info->attention_status;
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return 0;
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}
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static int get_latch_status(struct hotplug_slot *hotplug_slot, u8 *value)
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{
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struct slot *slot = get_slot(hotplug_slot);
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int retval;
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ctrl_dbg(slot->ctrl, "%s: physical_slot = %s\n",
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__func__, slot_name(slot));
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retval = slot->hpc_ops->get_latch_status(slot, value);
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if (retval < 0)
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*value = hotplug_slot->info->latch_status;
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return 0;
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}
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static int get_adapter_status(struct hotplug_slot *hotplug_slot, u8 *value)
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{
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struct slot *slot = get_slot(hotplug_slot);
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int retval;
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ctrl_dbg(slot->ctrl, "%s: physical_slot = %s\n",
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__func__, slot_name(slot));
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retval = slot->hpc_ops->get_adapter_status(slot, value);
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if (retval < 0)
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*value = hotplug_slot->info->adapter_status;
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return 0;
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}
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static bool shpc_capable(struct pci_dev *bridge)
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{
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/*
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* It is assumed that AMD GOLAM chips support SHPC but they do not
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* have SHPC capability.
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*/
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if (bridge->vendor == PCI_VENDOR_ID_AMD &&
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bridge->device == PCI_DEVICE_ID_AMD_GOLAM_7450)
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return true;
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if (pci_find_capability(bridge, PCI_CAP_ID_SHPC))
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return true;
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return false;
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}
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static int shpc_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
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{
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int rc;
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struct controller *ctrl;
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if (!shpc_capable(pdev))
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return -ENODEV;
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if (acpi_get_hp_hw_control_from_firmware(pdev))
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return -ENODEV;
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ctrl = kzalloc(sizeof(*ctrl), GFP_KERNEL);
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if (!ctrl)
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goto err_out_none;
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INIT_LIST_HEAD(&ctrl->slot_list);
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rc = shpc_init(ctrl, pdev);
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if (rc) {
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ctrl_dbg(ctrl, "Controller initialization failed\n");
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goto err_out_free_ctrl;
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}
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pci_set_drvdata(pdev, ctrl);
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/* Setup the slot information structures */
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rc = init_slots(ctrl);
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if (rc) {
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ctrl_err(ctrl, "Slot initialization failed\n");
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goto err_out_release_ctlr;
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}
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rc = shpchp_create_ctrl_files(ctrl);
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if (rc)
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goto err_cleanup_slots;
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pdev->shpc_managed = 1;
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return 0;
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err_cleanup_slots:
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cleanup_slots(ctrl);
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err_out_release_ctlr:
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ctrl->hpc_ops->release_ctlr(ctrl);
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err_out_free_ctrl:
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kfree(ctrl);
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err_out_none:
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return -ENODEV;
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}
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static void shpc_remove(struct pci_dev *dev)
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{
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struct controller *ctrl = pci_get_drvdata(dev);
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dev->shpc_managed = 0;
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shpchp_remove_ctrl_files(ctrl);
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ctrl->hpc_ops->release_ctlr(ctrl);
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kfree(ctrl);
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}
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static const struct pci_device_id shpcd_pci_tbl[] = {
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{PCI_DEVICE_CLASS(((PCI_CLASS_BRIDGE_PCI << 8) | 0x00), ~0)},
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{ /* end: all zeroes */ }
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};
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MODULE_DEVICE_TABLE(pci, shpcd_pci_tbl);
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static struct pci_driver shpc_driver = {
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.name = SHPC_MODULE_NAME,
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.id_table = shpcd_pci_tbl,
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.probe = shpc_probe,
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.remove = shpc_remove,
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};
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static int __init shpcd_init(void)
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{
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int retval;
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retval = pci_register_driver(&shpc_driver);
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dbg("%s: pci_register_driver = %d\n", __func__, retval);
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info(DRIVER_DESC " version: " DRIVER_VERSION "\n");
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return retval;
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}
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static void __exit shpcd_cleanup(void)
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{
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dbg("unload_shpchpd()\n");
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pci_unregister_driver(&shpc_driver);
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info(DRIVER_DESC " version: " DRIVER_VERSION " unloaded\n");
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}
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module_init(shpcd_init);
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module_exit(shpcd_cleanup);
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