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-rw-r--r--arch/um/kernel/irq.c599
1 files changed, 599 insertions, 0 deletions
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
new file mode 100644
index 000000000..3577118bb
--- /dev/null
+++ b/arch/um/kernel/irq.c
@@ -0,0 +1,599 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2017 - Cambridge Greys Ltd
+ * Copyright (C) 2011 - 2014 Cisco Systems Inc
+ * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Derived (i.e. mostly copied) from arch/i386/kernel/irq.c:
+ * Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
+ */
+
+#include <linux/cpumask.h>
+#include <linux/hardirq.h>
+#include <linux/interrupt.h>
+#include <linux/kernel_stat.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <as-layout.h>
+#include <kern_util.h>
+#include <os.h>
+#include <irq_user.h>
+
+
+extern void free_irqs(void);
+
+/* When epoll triggers we do not know why it did so
+ * we can also have different IRQs for read and write.
+ * This is why we keep a small irq_fd array for each fd -
+ * one entry per IRQ type
+ */
+
+struct irq_entry {
+ struct irq_entry *next;
+ int fd;
+ struct irq_fd *irq_array[MAX_IRQ_TYPE + 1];
+};
+
+static struct irq_entry *active_fds;
+
+static DEFINE_SPINLOCK(irq_lock);
+
+static void irq_io_loop(struct irq_fd *irq, struct uml_pt_regs *regs)
+{
+/*
+ * irq->active guards against reentry
+ * irq->pending accumulates pending requests
+ * if pending is raised the irq_handler is re-run
+ * until pending is cleared
+ */
+ if (irq->active) {
+ irq->active = false;
+ do {
+ irq->pending = false;
+ do_IRQ(irq->irq, regs);
+ } while (irq->pending && (!irq->purge));
+ if (!irq->purge)
+ irq->active = true;
+ } else {
+ irq->pending = true;
+ }
+}
+
+void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
+{
+ struct irq_entry *irq_entry;
+ struct irq_fd *irq;
+
+ int n, i, j;
+
+ while (1) {
+ /* This is now lockless - epoll keeps back-referencesto the irqs
+ * which have trigger it so there is no need to walk the irq
+ * list and lock it every time. We avoid locking by turning off
+ * IO for a specific fd by executing os_del_epoll_fd(fd) before
+ * we do any changes to the actual data structures
+ */
+ n = os_waiting_for_events_epoll();
+
+ if (n <= 0) {
+ if (n == -EINTR)
+ continue;
+ else
+ break;
+ }
+
+ for (i = 0; i < n ; i++) {
+ /* Epoll back reference is the entry with 3 irq_fd
+ * leaves - one for each irq type.
+ */
+ irq_entry = (struct irq_entry *)
+ os_epoll_get_data_pointer(i);
+ for (j = 0; j < MAX_IRQ_TYPE ; j++) {
+ irq = irq_entry->irq_array[j];
+ if (irq == NULL)
+ continue;
+ if (os_epoll_triggered(i, irq->events) > 0)
+ irq_io_loop(irq, regs);
+ if (irq->purge) {
+ irq_entry->irq_array[j] = NULL;
+ kfree(irq);
+ }
+ }
+ }
+ }
+
+ free_irqs();
+}
+
+static int assign_epoll_events_to_irq(struct irq_entry *irq_entry)
+{
+ int i;
+ int events = 0;
+ struct irq_fd *irq;
+
+ for (i = 0; i < MAX_IRQ_TYPE ; i++) {
+ irq = irq_entry->irq_array[i];
+ if (irq != NULL)
+ events = irq->events | events;
+ }
+ if (events > 0) {
+ /* os_add_epoll will call os_mod_epoll if this already exists */
+ return os_add_epoll_fd(events, irq_entry->fd, irq_entry);
+ }
+ /* No events - delete */
+ return os_del_epoll_fd(irq_entry->fd);
+}
+
+
+
+static int activate_fd(int irq, int fd, int type, void *dev_id)
+{
+ struct irq_fd *new_fd;
+ struct irq_entry *irq_entry;
+ int i, err, events;
+ unsigned long flags;
+
+ err = os_set_fd_async(fd);
+ if (err < 0)
+ goto out;
+
+ spin_lock_irqsave(&irq_lock, flags);
+
+ /* Check if we have an entry for this fd */
+
+ err = -EBUSY;
+ for (irq_entry = active_fds;
+ irq_entry != NULL; irq_entry = irq_entry->next) {
+ if (irq_entry->fd == fd)
+ break;
+ }
+
+ if (irq_entry == NULL) {
+ /* This needs to be atomic as it may be called from an
+ * IRQ context.
+ */
+ irq_entry = kmalloc(sizeof(struct irq_entry), GFP_ATOMIC);
+ if (irq_entry == NULL) {
+ printk(KERN_ERR
+ "Failed to allocate new IRQ entry\n");
+ goto out_unlock;
+ }
+ irq_entry->fd = fd;
+ for (i = 0; i < MAX_IRQ_TYPE; i++)
+ irq_entry->irq_array[i] = NULL;
+ irq_entry->next = active_fds;
+ active_fds = irq_entry;
+ }
+
+ /* Check if we are trying to re-register an interrupt for a
+ * particular fd
+ */
+
+ if (irq_entry->irq_array[type] != NULL) {
+ printk(KERN_ERR
+ "Trying to reregister IRQ %d FD %d TYPE %d ID %p\n",
+ irq, fd, type, dev_id
+ );
+ goto out_unlock;
+ } else {
+ /* New entry for this fd */
+
+ err = -ENOMEM;
+ new_fd = kmalloc(sizeof(struct irq_fd), GFP_ATOMIC);
+ if (new_fd == NULL)
+ goto out_unlock;
+
+ events = os_event_mask(type);
+
+ *new_fd = ((struct irq_fd) {
+ .id = dev_id,
+ .irq = irq,
+ .type = type,
+ .events = events,
+ .active = true,
+ .pending = false,
+ .purge = false
+ });
+ /* Turn off any IO on this fd - allows us to
+ * avoid locking the IRQ loop
+ */
+ os_del_epoll_fd(irq_entry->fd);
+ irq_entry->irq_array[type] = new_fd;
+ }
+
+ /* Turn back IO on with the correct (new) IO event mask */
+ assign_epoll_events_to_irq(irq_entry);
+ spin_unlock_irqrestore(&irq_lock, flags);
+ maybe_sigio_broken(fd, (type != IRQ_NONE));
+
+ return 0;
+out_unlock:
+ spin_unlock_irqrestore(&irq_lock, flags);
+out:
+ return err;
+}
+
+/*
+ * Walk the IRQ list and dispose of any unused entries.
+ * Should be done under irq_lock.
+ */
+
+static void garbage_collect_irq_entries(void)
+{
+ int i;
+ bool reap;
+ struct irq_entry *walk;
+ struct irq_entry *previous = NULL;
+ struct irq_entry *to_free;
+
+ if (active_fds == NULL)
+ return;
+ walk = active_fds;
+ while (walk != NULL) {
+ reap = true;
+ for (i = 0; i < MAX_IRQ_TYPE ; i++) {
+ if (walk->irq_array[i] != NULL) {
+ reap = false;
+ break;
+ }
+ }
+ if (reap) {
+ if (previous == NULL)
+ active_fds = walk->next;
+ else
+ previous->next = walk->next;
+ to_free = walk;
+ } else {
+ to_free = NULL;
+ }
+ walk = walk->next;
+ kfree(to_free);
+ }
+}
+
+/*
+ * Walk the IRQ list and get the descriptor for our FD
+ */
+
+static struct irq_entry *get_irq_entry_by_fd(int fd)
+{
+ struct irq_entry *walk = active_fds;
+
+ while (walk != NULL) {
+ if (walk->fd == fd)
+ return walk;
+ walk = walk->next;
+ }
+ return NULL;
+}
+
+
+/*
+ * Walk the IRQ list and dispose of an entry for a specific
+ * device, fd and number. Note - if sharing an IRQ for read
+ * and writefor the same FD it will be disposed in either case.
+ * If this behaviour is undesirable use different IRQ ids.
+ */
+
+#define IGNORE_IRQ 1
+#define IGNORE_DEV (1<<1)
+
+static void do_free_by_irq_and_dev(
+ struct irq_entry *irq_entry,
+ unsigned int irq,
+ void *dev,
+ int flags
+)
+{
+ int i;
+ struct irq_fd *to_free;
+
+ for (i = 0; i < MAX_IRQ_TYPE ; i++) {
+ if (irq_entry->irq_array[i] != NULL) {
+ if (
+ ((flags & IGNORE_IRQ) ||
+ (irq_entry->irq_array[i]->irq == irq)) &&
+ ((flags & IGNORE_DEV) ||
+ (irq_entry->irq_array[i]->id == dev))
+ ) {
+ /* Turn off any IO on this fd - allows us to
+ * avoid locking the IRQ loop
+ */
+ os_del_epoll_fd(irq_entry->fd);
+ to_free = irq_entry->irq_array[i];
+ irq_entry->irq_array[i] = NULL;
+ assign_epoll_events_to_irq(irq_entry);
+ if (to_free->active)
+ to_free->purge = true;
+ else
+ kfree(to_free);
+ }
+ }
+ }
+}
+
+void free_irq_by_fd(int fd)
+{
+ struct irq_entry *to_free;
+ unsigned long flags;
+
+ spin_lock_irqsave(&irq_lock, flags);
+ to_free = get_irq_entry_by_fd(fd);
+ if (to_free != NULL) {
+ do_free_by_irq_and_dev(
+ to_free,
+ -1,
+ NULL,
+ IGNORE_IRQ | IGNORE_DEV
+ );
+ }
+ garbage_collect_irq_entries();
+ spin_unlock_irqrestore(&irq_lock, flags);
+}
+EXPORT_SYMBOL(free_irq_by_fd);
+
+static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
+{
+ struct irq_entry *to_free;
+ unsigned long flags;
+
+ spin_lock_irqsave(&irq_lock, flags);
+ to_free = active_fds;
+ while (to_free != NULL) {
+ do_free_by_irq_and_dev(
+ to_free,
+ irq,
+ dev,
+ 0
+ );
+ to_free = to_free->next;
+ }
+ garbage_collect_irq_entries();
+ spin_unlock_irqrestore(&irq_lock, flags);
+}
+
+
+void deactivate_fd(int fd, int irqnum)
+{
+ struct irq_entry *to_free;
+ unsigned long flags;
+
+ os_del_epoll_fd(fd);
+ spin_lock_irqsave(&irq_lock, flags);
+ to_free = get_irq_entry_by_fd(fd);
+ if (to_free != NULL) {
+ do_free_by_irq_and_dev(
+ to_free,
+ irqnum,
+ NULL,
+ IGNORE_DEV
+ );
+ }
+ garbage_collect_irq_entries();
+ spin_unlock_irqrestore(&irq_lock, flags);
+ ignore_sigio_fd(fd);
+}
+EXPORT_SYMBOL(deactivate_fd);
+
+/*
+ * Called just before shutdown in order to provide a clean exec
+ * environment in case the system is rebooting. No locking because
+ * that would cause a pointless shutdown hang if something hadn't
+ * released the lock.
+ */
+int deactivate_all_fds(void)
+{
+ struct irq_entry *to_free;
+
+ /* Stop IO. The IRQ loop has no lock so this is our
+ * only way of making sure we are safe to dispose
+ * of all IRQ handlers
+ */
+ os_set_ioignore();
+ to_free = active_fds;
+ while (to_free != NULL) {
+ do_free_by_irq_and_dev(
+ to_free,
+ -1,
+ NULL,
+ IGNORE_IRQ | IGNORE_DEV
+ );
+ to_free = to_free->next;
+ }
+ /* don't garbage collect - we can no longer call kfree() here */
+ os_close_epoll_fd();
+ return 0;
+}
+
+/*
+ * do_IRQ handles all normal device IRQs (the special
+ * SMP cross-CPU interrupts have their own specific
+ * handlers).
+ */
+unsigned int do_IRQ(int irq, struct uml_pt_regs *regs)
+{
+ struct pt_regs *old_regs = set_irq_regs((struct pt_regs *)regs);
+ irq_enter();
+ generic_handle_irq(irq);
+ irq_exit();
+ set_irq_regs(old_regs);
+ return 1;
+}
+
+void um_free_irq(unsigned int irq, void *dev)
+{
+ free_irq_by_irq_and_dev(irq, dev);
+ free_irq(irq, dev);
+}
+EXPORT_SYMBOL(um_free_irq);
+
+int um_request_irq(unsigned int irq, int fd, int type,
+ irq_handler_t handler,
+ unsigned long irqflags, const char * devname,
+ void *dev_id)
+{
+ int err;
+
+ if (fd != -1) {
+ err = activate_fd(irq, fd, type, dev_id);
+ if (err)
+ return err;
+ }
+
+ return request_irq(irq, handler, irqflags, devname, dev_id);
+}
+
+EXPORT_SYMBOL(um_request_irq);
+
+/*
+ * irq_chip must define at least enable/disable and ack when
+ * the edge handler is used.
+ */
+static void dummy(struct irq_data *d)
+{
+}
+
+/* This is used for everything else than the timer. */
+static struct irq_chip normal_irq_type = {
+ .name = "SIGIO",
+ .irq_disable = dummy,
+ .irq_enable = dummy,
+ .irq_ack = dummy,
+ .irq_mask = dummy,
+ .irq_unmask = dummy,
+};
+
+static struct irq_chip SIGVTALRM_irq_type = {
+ .name = "SIGVTALRM",
+ .irq_disable = dummy,
+ .irq_enable = dummy,
+ .irq_ack = dummy,
+ .irq_mask = dummy,
+ .irq_unmask = dummy,
+};
+
+void __init init_IRQ(void)
+{
+ int i;
+
+ irq_set_chip_and_handler(TIMER_IRQ, &SIGVTALRM_irq_type, handle_edge_irq);
+
+
+ for (i = 1; i <= LAST_IRQ; i++)
+ irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
+ /* Initialize EPOLL Loop */
+ os_setup_epoll();
+}
+
+/*
+ * IRQ stack entry and exit:
+ *
+ * Unlike i386, UML doesn't receive IRQs on the normal kernel stack
+ * and switch over to the IRQ stack after some preparation. We use
+ * sigaltstack to receive signals on a separate stack from the start.
+ * These two functions make sure the rest of the kernel won't be too
+ * upset by being on a different stack. The IRQ stack has a
+ * thread_info structure at the bottom so that current et al continue
+ * to work.
+ *
+ * to_irq_stack copies the current task's thread_info to the IRQ stack
+ * thread_info and sets the tasks's stack to point to the IRQ stack.
+ *
+ * from_irq_stack copies the thread_info struct back (flags may have
+ * been modified) and resets the task's stack pointer.
+ *
+ * Tricky bits -
+ *
+ * What happens when two signals race each other? UML doesn't block
+ * signals with sigprocmask, SA_DEFER, or sa_mask, so a second signal
+ * could arrive while a previous one is still setting up the
+ * thread_info.
+ *
+ * There are three cases -
+ * The first interrupt on the stack - sets up the thread_info and
+ * handles the interrupt
+ * A nested interrupt interrupting the copying of the thread_info -
+ * can't handle the interrupt, as the stack is in an unknown state
+ * A nested interrupt not interrupting the copying of the
+ * thread_info - doesn't do any setup, just handles the interrupt
+ *
+ * The first job is to figure out whether we interrupted stack setup.
+ * This is done by xchging the signal mask with thread_info->pending.
+ * If the value that comes back is zero, then there is no setup in
+ * progress, and the interrupt can be handled. If the value is
+ * non-zero, then there is stack setup in progress. In order to have
+ * the interrupt handled, we leave our signal in the mask, and it will
+ * be handled by the upper handler after it has set up the stack.
+ *
+ * Next is to figure out whether we are the outer handler or a nested
+ * one. As part of setting up the stack, thread_info->real_thread is
+ * set to non-NULL (and is reset to NULL on exit). This is the
+ * nesting indicator. If it is non-NULL, then the stack is already
+ * set up and the handler can run.
+ */
+
+static unsigned long pending_mask;
+
+unsigned long to_irq_stack(unsigned long *mask_out)
+{
+ struct thread_info *ti;
+ unsigned long mask, old;
+ int nested;
+
+ mask = xchg(&pending_mask, *mask_out);
+ if (mask != 0) {
+ /*
+ * If any interrupts come in at this point, we want to
+ * 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;
+}
+
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