600 lines
14 KiB
C
600 lines
14 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2017 - Cambridge Greys Ltd
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* Copyright (C) 2011 - 2014 Cisco Systems Inc
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* Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
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* Derived (i.e. mostly copied) from arch/i386/kernel/irq.c:
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* Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
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*/
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#include <linux/cpumask.h>
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#include <linux/hardirq.h>
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#include <linux/interrupt.h>
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#include <linux/kernel_stat.h>
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/seq_file.h>
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#include <linux/slab.h>
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#include <as-layout.h>
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#include <kern_util.h>
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#include <os.h>
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#include <irq_user.h>
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extern void free_irqs(void);
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/* When epoll triggers we do not know why it did so
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* we can also have different IRQs for read and write.
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* This is why we keep a small irq_fd array for each fd -
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* one entry per IRQ type
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*/
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struct irq_entry {
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struct irq_entry *next;
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int fd;
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struct irq_fd *irq_array[MAX_IRQ_TYPE + 1];
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};
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static struct irq_entry *active_fds;
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static DEFINE_SPINLOCK(irq_lock);
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static void irq_io_loop(struct irq_fd *irq, struct uml_pt_regs *regs)
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{
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/*
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* irq->active guards against reentry
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* irq->pending accumulates pending requests
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* if pending is raised the irq_handler is re-run
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* until pending is cleared
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*/
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if (irq->active) {
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irq->active = false;
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do {
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irq->pending = false;
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do_IRQ(irq->irq, regs);
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} while (irq->pending && (!irq->purge));
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if (!irq->purge)
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irq->active = true;
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} else {
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irq->pending = true;
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}
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}
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void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
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{
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struct irq_entry *irq_entry;
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struct irq_fd *irq;
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int n, i, j;
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while (1) {
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/* This is now lockless - epoll keeps back-referencesto the irqs
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* which have trigger it so there is no need to walk the irq
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* list and lock it every time. We avoid locking by turning off
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* IO for a specific fd by executing os_del_epoll_fd(fd) before
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* we do any changes to the actual data structures
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*/
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n = os_waiting_for_events_epoll();
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if (n <= 0) {
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if (n == -EINTR)
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continue;
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else
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break;
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}
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for (i = 0; i < n ; i++) {
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/* Epoll back reference is the entry with 3 irq_fd
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* leaves - one for each irq type.
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*/
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irq_entry = (struct irq_entry *)
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os_epoll_get_data_pointer(i);
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for (j = 0; j < MAX_IRQ_TYPE ; j++) {
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irq = irq_entry->irq_array[j];
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if (irq == NULL)
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continue;
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if (os_epoll_triggered(i, irq->events) > 0)
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irq_io_loop(irq, regs);
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if (irq->purge) {
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irq_entry->irq_array[j] = NULL;
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kfree(irq);
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}
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}
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}
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}
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free_irqs();
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}
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static int assign_epoll_events_to_irq(struct irq_entry *irq_entry)
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{
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int i;
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int events = 0;
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struct irq_fd *irq;
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for (i = 0; i < MAX_IRQ_TYPE ; i++) {
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irq = irq_entry->irq_array[i];
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if (irq != NULL)
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events = irq->events | events;
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}
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if (events > 0) {
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/* os_add_epoll will call os_mod_epoll if this already exists */
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return os_add_epoll_fd(events, irq_entry->fd, irq_entry);
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}
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/* No events - delete */
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return os_del_epoll_fd(irq_entry->fd);
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}
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static int activate_fd(int irq, int fd, int type, void *dev_id)
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{
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struct irq_fd *new_fd;
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struct irq_entry *irq_entry;
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int i, err, events;
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unsigned long flags;
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err = os_set_fd_async(fd);
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if (err < 0)
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goto out;
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spin_lock_irqsave(&irq_lock, flags);
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/* Check if we have an entry for this fd */
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err = -EBUSY;
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for (irq_entry = active_fds;
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irq_entry != NULL; irq_entry = irq_entry->next) {
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if (irq_entry->fd == fd)
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break;
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}
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if (irq_entry == NULL) {
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/* This needs to be atomic as it may be called from an
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* IRQ context.
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*/
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irq_entry = kmalloc(sizeof(struct irq_entry), GFP_ATOMIC);
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if (irq_entry == NULL) {
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printk(KERN_ERR
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"Failed to allocate new IRQ entry\n");
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goto out_unlock;
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}
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irq_entry->fd = fd;
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for (i = 0; i < MAX_IRQ_TYPE; i++)
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irq_entry->irq_array[i] = NULL;
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irq_entry->next = active_fds;
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active_fds = irq_entry;
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}
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/* Check if we are trying to re-register an interrupt for a
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* particular fd
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*/
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if (irq_entry->irq_array[type] != NULL) {
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printk(KERN_ERR
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"Trying to reregister IRQ %d FD %d TYPE %d ID %p\n",
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irq, fd, type, dev_id
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);
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goto out_unlock;
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} else {
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/* New entry for this fd */
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err = -ENOMEM;
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new_fd = kmalloc(sizeof(struct irq_fd), GFP_ATOMIC);
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if (new_fd == NULL)
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goto out_unlock;
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events = os_event_mask(type);
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*new_fd = ((struct irq_fd) {
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.id = dev_id,
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.irq = irq,
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.type = type,
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.events = events,
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.active = true,
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.pending = false,
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.purge = false
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});
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/* Turn off any IO on this fd - allows us to
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* avoid locking the IRQ loop
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*/
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os_del_epoll_fd(irq_entry->fd);
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irq_entry->irq_array[type] = new_fd;
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}
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/* Turn back IO on with the correct (new) IO event mask */
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assign_epoll_events_to_irq(irq_entry);
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spin_unlock_irqrestore(&irq_lock, flags);
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maybe_sigio_broken(fd, (type != IRQ_NONE));
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return 0;
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out_unlock:
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spin_unlock_irqrestore(&irq_lock, flags);
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out:
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return err;
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}
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/*
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* Walk the IRQ list and dispose of any unused entries.
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* Should be done under irq_lock.
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*/
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static void garbage_collect_irq_entries(void)
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{
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int i;
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bool reap;
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struct irq_entry *walk;
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struct irq_entry *previous = NULL;
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struct irq_entry *to_free;
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if (active_fds == NULL)
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return;
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walk = active_fds;
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while (walk != NULL) {
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reap = true;
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for (i = 0; i < MAX_IRQ_TYPE ; i++) {
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if (walk->irq_array[i] != NULL) {
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reap = false;
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break;
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}
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}
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if (reap) {
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if (previous == NULL)
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active_fds = walk->next;
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else
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previous->next = walk->next;
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to_free = walk;
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} else {
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to_free = NULL;
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}
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walk = walk->next;
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kfree(to_free);
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}
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}
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/*
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* Walk the IRQ list and get the descriptor for our FD
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*/
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static struct irq_entry *get_irq_entry_by_fd(int fd)
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{
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struct irq_entry *walk = active_fds;
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while (walk != NULL) {
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if (walk->fd == fd)
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return walk;
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walk = walk->next;
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}
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return NULL;
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}
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/*
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* Walk the IRQ list and dispose of an entry for a specific
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* device, fd and number. Note - if sharing an IRQ for read
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* and writefor the same FD it will be disposed in either case.
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* If this behaviour is undesirable use different IRQ ids.
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*/
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#define IGNORE_IRQ 1
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#define IGNORE_DEV (1<<1)
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static void do_free_by_irq_and_dev(
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struct irq_entry *irq_entry,
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unsigned int irq,
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void *dev,
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int flags
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)
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{
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int i;
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struct irq_fd *to_free;
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for (i = 0; i < MAX_IRQ_TYPE ; i++) {
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if (irq_entry->irq_array[i] != NULL) {
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if (
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((flags & IGNORE_IRQ) ||
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(irq_entry->irq_array[i]->irq == irq)) &&
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((flags & IGNORE_DEV) ||
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(irq_entry->irq_array[i]->id == dev))
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) {
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/* Turn off any IO on this fd - allows us to
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* avoid locking the IRQ loop
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*/
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os_del_epoll_fd(irq_entry->fd);
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to_free = irq_entry->irq_array[i];
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irq_entry->irq_array[i] = NULL;
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assign_epoll_events_to_irq(irq_entry);
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if (to_free->active)
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to_free->purge = true;
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else
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kfree(to_free);
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}
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}
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}
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}
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void free_irq_by_fd(int fd)
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{
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struct irq_entry *to_free;
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unsigned long flags;
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spin_lock_irqsave(&irq_lock, flags);
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to_free = get_irq_entry_by_fd(fd);
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if (to_free != NULL) {
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do_free_by_irq_and_dev(
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to_free,
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-1,
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NULL,
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IGNORE_IRQ | IGNORE_DEV
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);
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}
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garbage_collect_irq_entries();
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spin_unlock_irqrestore(&irq_lock, flags);
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}
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EXPORT_SYMBOL(free_irq_by_fd);
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static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
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{
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struct irq_entry *to_free;
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unsigned long flags;
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spin_lock_irqsave(&irq_lock, flags);
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to_free = active_fds;
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while (to_free != NULL) {
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do_free_by_irq_and_dev(
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to_free,
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irq,
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dev,
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0
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);
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to_free = to_free->next;
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}
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garbage_collect_irq_entries();
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spin_unlock_irqrestore(&irq_lock, flags);
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}
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void deactivate_fd(int fd, int irqnum)
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{
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struct irq_entry *to_free;
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unsigned long flags;
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os_del_epoll_fd(fd);
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spin_lock_irqsave(&irq_lock, flags);
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to_free = get_irq_entry_by_fd(fd);
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if (to_free != NULL) {
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do_free_by_irq_and_dev(
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to_free,
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irqnum,
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NULL,
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IGNORE_DEV
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);
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}
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garbage_collect_irq_entries();
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spin_unlock_irqrestore(&irq_lock, flags);
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ignore_sigio_fd(fd);
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}
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EXPORT_SYMBOL(deactivate_fd);
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/*
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* Called just before shutdown in order to provide a clean exec
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* environment in case the system is rebooting. No locking because
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* that would cause a pointless shutdown hang if something hadn't
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* released the lock.
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*/
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int deactivate_all_fds(void)
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{
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struct irq_entry *to_free;
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/* Stop IO. The IRQ loop has no lock so this is our
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* only way of making sure we are safe to dispose
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* of all IRQ handlers
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*/
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os_set_ioignore();
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to_free = active_fds;
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while (to_free != NULL) {
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do_free_by_irq_and_dev(
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to_free,
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-1,
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NULL,
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IGNORE_IRQ | IGNORE_DEV
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);
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to_free = to_free->next;
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}
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/* don't garbage collect - we can no longer call kfree() here */
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os_close_epoll_fd();
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return 0;
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}
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/*
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* do_IRQ handles all normal device IRQs (the special
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* SMP cross-CPU interrupts have their own specific
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* handlers).
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*/
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unsigned int do_IRQ(int irq, struct uml_pt_regs *regs)
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{
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struct pt_regs *old_regs = set_irq_regs((struct pt_regs *)regs);
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irq_enter();
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generic_handle_irq(irq);
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irq_exit();
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set_irq_regs(old_regs);
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return 1;
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}
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void um_free_irq(unsigned int irq, void *dev)
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{
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free_irq_by_irq_and_dev(irq, dev);
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free_irq(irq, dev);
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}
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EXPORT_SYMBOL(um_free_irq);
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int um_request_irq(unsigned int irq, int fd, int type,
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irq_handler_t handler,
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unsigned long irqflags, const char * devname,
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void *dev_id)
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{
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int err;
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if (fd != -1) {
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err = activate_fd(irq, fd, type, dev_id);
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if (err)
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return err;
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}
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return request_irq(irq, handler, irqflags, devname, dev_id);
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}
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EXPORT_SYMBOL(um_request_irq);
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/*
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* irq_chip must define at least enable/disable and ack when
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* the edge handler is used.
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*/
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static void dummy(struct irq_data *d)
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{
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}
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/* This is used for everything else than the timer. */
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static struct irq_chip normal_irq_type = {
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.name = "SIGIO",
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.irq_disable = dummy,
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.irq_enable = dummy,
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.irq_ack = dummy,
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.irq_mask = dummy,
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.irq_unmask = dummy,
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};
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static struct irq_chip SIGVTALRM_irq_type = {
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.name = "SIGVTALRM",
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.irq_disable = dummy,
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.irq_enable = dummy,
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.irq_ack = dummy,
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.irq_mask = dummy,
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.irq_unmask = dummy,
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};
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void __init init_IRQ(void)
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{
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int i;
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irq_set_chip_and_handler(TIMER_IRQ, &SIGVTALRM_irq_type, handle_edge_irq);
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for (i = 1; i <= LAST_IRQ; i++)
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irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
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/* Initialize EPOLL Loop */
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os_setup_epoll();
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}
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/*
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* IRQ stack entry and exit:
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*
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* Unlike i386, UML doesn't receive IRQs on the normal kernel stack
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* and switch over to the IRQ stack after some preparation. We use
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* sigaltstack to receive signals on a separate stack from the start.
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* These two functions make sure the rest of the kernel won't be too
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* upset by being on a different stack. The IRQ stack has a
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* thread_info structure at the bottom so that current et al continue
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* to work.
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*
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* to_irq_stack copies the current task's thread_info to the IRQ stack
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* thread_info and sets the tasks's stack to point to the IRQ stack.
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*
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* from_irq_stack copies the thread_info struct back (flags may have
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* been modified) and resets the task's stack pointer.
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*
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* Tricky bits -
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*
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* What happens when two signals race each other? UML doesn't block
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* signals with sigprocmask, SA_DEFER, or sa_mask, so a second signal
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* could arrive while a previous one is still setting up the
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* thread_info.
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*
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* There are three cases -
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* The first interrupt on the stack - sets up the thread_info and
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* handles the interrupt
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* A nested interrupt interrupting the copying of the thread_info -
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* can't handle the interrupt, as the stack is in an unknown state
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* A nested interrupt not interrupting the copying of the
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* thread_info - doesn't do any setup, just handles the interrupt
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*
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* The first job is to figure out whether we interrupted stack setup.
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* This is done by xchging the signal mask with thread_info->pending.
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* If the value that comes back is zero, then there is no setup in
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* progress, and the interrupt can be handled. If the value is
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* non-zero, then there is stack setup in progress. In order to have
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* the interrupt handled, we leave our signal in the mask, and it will
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* be handled by the upper handler after it has set up the stack.
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*
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* Next is to figure out whether we are the outer handler or a nested
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* one. As part of setting up the stack, thread_info->real_thread is
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* set to non-NULL (and is reset to NULL on exit). This is the
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* nesting indicator. If it is non-NULL, then the stack is already
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* set up and the handler can run.
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*/
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static unsigned long pending_mask;
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unsigned long to_irq_stack(unsigned long *mask_out)
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{
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struct thread_info *ti;
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unsigned long mask, old;
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int nested;
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mask = xchg(&pending_mask, *mask_out);
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if (mask != 0) {
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/*
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* If any interrupts come in at this point, we want to
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* make sure that their bits aren't lost by our
|
|
* putting our bit in. So, this loop accumulates bits
|
|
* until xchg returns the same value that we put in.
|
|
* When that happens, there were no new interrupts,
|
|
* and pending_mask contains a bit for each interrupt
|
|
* that came in.
|
|
*/
|
|
old = *mask_out;
|
|
do {
|
|
old |= mask;
|
|
mask = xchg(&pending_mask, old);
|
|
} while (mask != old);
|
|
return 1;
|
|
}
|
|
|
|
ti = current_thread_info();
|
|
nested = (ti->real_thread != NULL);
|
|
if (!nested) {
|
|
struct task_struct *task;
|
|
struct thread_info *tti;
|
|
|
|
task = cpu_tasks[ti->cpu].task;
|
|
tti = task_thread_info(task);
|
|
|
|
*ti = *tti;
|
|
ti->real_thread = tti;
|
|
task->stack = ti;
|
|
}
|
|
|
|
mask = xchg(&pending_mask, 0);
|
|
*mask_out |= mask | nested;
|
|
return 0;
|
|
}
|
|
|
|
unsigned long from_irq_stack(int nested)
|
|
{
|
|
struct thread_info *ti, *to;
|
|
unsigned long mask;
|
|
|
|
ti = current_thread_info();
|
|
|
|
pending_mask = 1;
|
|
|
|
to = ti->real_thread;
|
|
current->stack = to;
|
|
ti->real_thread = NULL;
|
|
*to = *ti;
|
|
|
|
mask = xchg(&pending_mask, 0);
|
|
return mask & ~1;
|
|
}
|
|
|