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-rw-r--r--arch/um/kernel/irq.c766
1 files changed, 766 insertions, 0 deletions
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
new file mode 100644
index 0000000000..635d44606b
--- /dev/null
+++ b/arch/um/kernel/irq.c
@@ -0,0 +1,766 @@
+// 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>
+#include <irq_kern.h>
+#include <linux/time-internal.h>
+
+
+/* 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_reg array for each fd -
+ * one entry per IRQ type
+ */
+struct irq_reg {
+ void *id;
+ int irq;
+ /* it's cheaper to store this than to query it */
+ int events;
+ bool active;
+ bool pending;
+ bool wakeup;
+#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
+ bool pending_on_resume;
+ void (*timetravel_handler)(int, int, void *,
+ struct time_travel_event *);
+ struct time_travel_event event;
+#endif
+};
+
+struct irq_entry {
+ struct list_head list;
+ int fd;
+ struct irq_reg reg[NUM_IRQ_TYPES];
+ bool suspended;
+ bool sigio_workaround;
+};
+
+static DEFINE_SPINLOCK(irq_lock);
+static LIST_HEAD(active_fds);
+static DECLARE_BITMAP(irqs_allocated, UM_LAST_SIGNAL_IRQ);
+static bool irqs_suspended;
+
+static void irq_io_loop(struct irq_reg *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->active = true;
+ } else {
+ irq->pending = true;
+ }
+}
+
+#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
+static void irq_event_handler(struct time_travel_event *ev)
+{
+ struct irq_reg *reg = container_of(ev, struct irq_reg, event);
+
+ /* do nothing if suspended - just to cause a wakeup */
+ if (irqs_suspended)
+ return;
+
+ generic_handle_irq(reg->irq);
+}
+
+static bool irq_do_timetravel_handler(struct irq_entry *entry,
+ enum um_irq_type t)
+{
+ struct irq_reg *reg = &entry->reg[t];
+
+ if (!reg->timetravel_handler)
+ return false;
+
+ /*
+ * Handle all messages - we might get multiple even while
+ * interrupts are already suspended, due to suspend order
+ * etc. Note that time_travel_add_irq_event() will not add
+ * an event twice, if it's pending already "first wins".
+ */
+ reg->timetravel_handler(reg->irq, entry->fd, reg->id, &reg->event);
+
+ if (!reg->event.pending)
+ return false;
+
+ if (irqs_suspended)
+ reg->pending_on_resume = true;
+ return true;
+}
+#else
+static bool irq_do_timetravel_handler(struct irq_entry *entry,
+ enum um_irq_type t)
+{
+ return false;
+}
+#endif
+
+static void sigio_reg_handler(int idx, struct irq_entry *entry, enum um_irq_type t,
+ struct uml_pt_regs *regs,
+ bool timetravel_handlers_only)
+{
+ struct irq_reg *reg = &entry->reg[t];
+
+ if (!reg->events)
+ return;
+
+ if (os_epoll_triggered(idx, reg->events) <= 0)
+ return;
+
+ if (irq_do_timetravel_handler(entry, t))
+ return;
+
+ /*
+ * If we're called to only run time-travel handlers then don't
+ * actually proceed but mark sigio as pending (if applicable).
+ * For suspend/resume, timetravel_handlers_only may be true
+ * despite time-travel not being configured and used.
+ */
+ if (timetravel_handlers_only) {
+#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
+ mark_sigio_pending();
+#endif
+ return;
+ }
+
+ irq_io_loop(reg, regs);
+}
+
+static void _sigio_handler(struct uml_pt_regs *regs,
+ bool timetravel_handlers_only)
+{
+ struct irq_entry *irq_entry;
+ int n, i;
+
+ if (timetravel_handlers_only && !um_irq_timetravel_handler_used())
+ return;
+
+ 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++) {
+ enum um_irq_type t;
+
+ irq_entry = os_epoll_get_data_pointer(i);
+
+ for (t = 0; t < NUM_IRQ_TYPES; t++)
+ sigio_reg_handler(i, irq_entry, t, regs,
+ timetravel_handlers_only);
+ }
+ }
+
+ if (!timetravel_handlers_only)
+ free_irqs();
+}
+
+void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
+{
+ _sigio_handler(regs, irqs_suspended);
+}
+
+static struct irq_entry *get_irq_entry_by_fd(int fd)
+{
+ struct irq_entry *walk;
+
+ lockdep_assert_held(&irq_lock);
+
+ list_for_each_entry(walk, &active_fds, list) {
+ if (walk->fd == fd)
+ return walk;
+ }
+
+ return NULL;
+}
+
+static void free_irq_entry(struct irq_entry *to_free, bool remove)
+{
+ if (!to_free)
+ return;
+
+ if (remove)
+ os_del_epoll_fd(to_free->fd);
+ list_del(&to_free->list);
+ kfree(to_free);
+}
+
+static bool update_irq_entry(struct irq_entry *entry)
+{
+ enum um_irq_type i;
+ int events = 0;
+
+ for (i = 0; i < NUM_IRQ_TYPES; i++)
+ events |= entry->reg[i].events;
+
+ if (events) {
+ /* will modify (instead of add) if needed */
+ os_add_epoll_fd(events, entry->fd, entry);
+ return true;
+ }
+
+ os_del_epoll_fd(entry->fd);
+ return false;
+}
+
+static void update_or_free_irq_entry(struct irq_entry *entry)
+{
+ if (!update_irq_entry(entry))
+ free_irq_entry(entry, false);
+}
+
+static int activate_fd(int irq, int fd, enum um_irq_type type, void *dev_id,
+ void (*timetravel_handler)(int, int, void *,
+ struct time_travel_event *))
+{
+ struct irq_entry *irq_entry;
+ int err, events = os_event_mask(type);
+ unsigned long flags;
+
+ err = os_set_fd_async(fd);
+ if (err < 0)
+ goto out;
+
+ spin_lock_irqsave(&irq_lock, flags);
+ irq_entry = get_irq_entry_by_fd(fd);
+ if (irq_entry) {
+ /* cannot register the same FD twice with the same type */
+ if (WARN_ON(irq_entry->reg[type].events)) {
+ err = -EALREADY;
+ goto out_unlock;
+ }
+
+ /* temporarily disable to avoid IRQ-side locking */
+ os_del_epoll_fd(fd);
+ } else {
+ irq_entry = kzalloc(sizeof(*irq_entry), GFP_ATOMIC);
+ if (!irq_entry) {
+ err = -ENOMEM;
+ goto out_unlock;
+ }
+ irq_entry->fd = fd;
+ list_add_tail(&irq_entry->list, &active_fds);
+ maybe_sigio_broken(fd);
+ }
+
+ irq_entry->reg[type].id = dev_id;
+ irq_entry->reg[type].irq = irq;
+ irq_entry->reg[type].active = true;
+ irq_entry->reg[type].events = events;
+
+#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
+ if (um_irq_timetravel_handler_used()) {
+ irq_entry->reg[type].timetravel_handler = timetravel_handler;
+ irq_entry->reg[type].event.fn = irq_event_handler;
+ }
+#endif
+
+ WARN_ON(!update_irq_entry(irq_entry));
+ spin_unlock_irqrestore(&irq_lock, flags);
+
+ return 0;
+out_unlock:
+ spin_unlock_irqrestore(&irq_lock, flags);
+out:
+ return err;
+}
+
+/*
+ * Remove the entry or entries for a specific FD, if you
+ * don't want to remove all the possible entries then use
+ * um_free_irq() or deactivate_fd() instead.
+ */
+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);
+ free_irq_entry(to_free, true);
+ 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 *entry;
+ unsigned long flags;
+
+ spin_lock_irqsave(&irq_lock, flags);
+ list_for_each_entry(entry, &active_fds, list) {
+ enum um_irq_type i;
+
+ for (i = 0; i < NUM_IRQ_TYPES; i++) {
+ struct irq_reg *reg = &entry->reg[i];
+
+ if (!reg->events)
+ continue;
+ if (reg->irq != irq)
+ continue;
+ if (reg->id != dev)
+ continue;
+
+ os_del_epoll_fd(entry->fd);
+ reg->events = 0;
+ update_or_free_irq_entry(entry);
+ goto out;
+ }
+ }
+out:
+ spin_unlock_irqrestore(&irq_lock, flags);
+}
+
+void deactivate_fd(int fd, int irqnum)
+{
+ struct irq_entry *entry;
+ unsigned long flags;
+ enum um_irq_type i;
+
+ os_del_epoll_fd(fd);
+
+ spin_lock_irqsave(&irq_lock, flags);
+ entry = get_irq_entry_by_fd(fd);
+ if (!entry)
+ goto out;
+
+ for (i = 0; i < NUM_IRQ_TYPES; i++) {
+ if (!entry->reg[i].events)
+ continue;
+ if (entry->reg[i].irq == irqnum)
+ entry->reg[i].events = 0;
+ }
+
+ update_or_free_irq_entry(entry);
+out:
+ 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 *entry;
+
+ /* 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();
+
+ /* we can no longer call kfree() here so just deactivate */
+ list_for_each_entry(entry, &active_fds, list)
+ os_del_epoll_fd(entry->fd);
+ 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(int irq, void *dev)
+{
+ if (WARN(irq < 0 || irq > UM_LAST_SIGNAL_IRQ,
+ "freeing invalid irq %d", irq))
+ return;
+
+ free_irq_by_irq_and_dev(irq, dev);
+ free_irq(irq, dev);
+ clear_bit(irq, irqs_allocated);
+}
+EXPORT_SYMBOL(um_free_irq);
+
+static int
+_um_request_irq(int irq, int fd, enum um_irq_type type,
+ irq_handler_t handler, unsigned long irqflags,
+ const char *devname, void *dev_id,
+ void (*timetravel_handler)(int, int, void *,
+ struct time_travel_event *))
+{
+ int err;
+
+ if (irq == UM_IRQ_ALLOC) {
+ int i;
+
+ for (i = UM_FIRST_DYN_IRQ; i < NR_IRQS; i++) {
+ if (!test_and_set_bit(i, irqs_allocated)) {
+ irq = i;
+ break;
+ }
+ }
+ }
+
+ if (irq < 0)
+ return -ENOSPC;
+
+ if (fd != -1) {
+ err = activate_fd(irq, fd, type, dev_id, timetravel_handler);
+ if (err)
+ goto error;
+ }
+
+ err = request_irq(irq, handler, irqflags, devname, dev_id);
+ if (err < 0)
+ goto error;
+
+ return irq;
+error:
+ clear_bit(irq, irqs_allocated);
+ return err;
+}
+
+int um_request_irq(int irq, int fd, enum um_irq_type type,
+ irq_handler_t handler, unsigned long irqflags,
+ const char *devname, void *dev_id)
+{
+ return _um_request_irq(irq, fd, type, handler, irqflags,
+ devname, dev_id, NULL);
+}
+EXPORT_SYMBOL(um_request_irq);
+
+#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
+int um_request_irq_tt(int irq, int fd, enum um_irq_type type,
+ irq_handler_t handler, unsigned long irqflags,
+ const char *devname, void *dev_id,
+ void (*timetravel_handler)(int, int, void *,
+ struct time_travel_event *))
+{
+ return _um_request_irq(irq, fd, type, handler, irqflags,
+ devname, dev_id, timetravel_handler);
+}
+EXPORT_SYMBOL(um_request_irq_tt);
+
+void sigio_run_timetravel_handlers(void)
+{
+ _sigio_handler(NULL, true);
+}
+#endif
+
+#ifdef CONFIG_PM_SLEEP
+void um_irqs_suspend(void)
+{
+ struct irq_entry *entry;
+ unsigned long flags;
+
+ irqs_suspended = true;
+
+ spin_lock_irqsave(&irq_lock, flags);
+ list_for_each_entry(entry, &active_fds, list) {
+ enum um_irq_type t;
+ bool clear = true;
+
+ for (t = 0; t < NUM_IRQ_TYPES; t++) {
+ if (!entry->reg[t].events)
+ continue;
+
+ /*
+ * For the SIGIO_WRITE_IRQ, which is used to handle the
+ * SIGIO workaround thread, we need special handling:
+ * enable wake for it itself, but below we tell it about
+ * any FDs that should be suspended.
+ */
+ if (entry->reg[t].wakeup ||
+ entry->reg[t].irq == SIGIO_WRITE_IRQ
+#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
+ || entry->reg[t].timetravel_handler
+#endif
+ ) {
+ clear = false;
+ break;
+ }
+ }
+
+ if (clear) {
+ entry->suspended = true;
+ os_clear_fd_async(entry->fd);
+ entry->sigio_workaround =
+ !__ignore_sigio_fd(entry->fd);
+ }
+ }
+ spin_unlock_irqrestore(&irq_lock, flags);
+}
+
+void um_irqs_resume(void)
+{
+ struct irq_entry *entry;
+ unsigned long flags;
+
+
+ local_irq_save(flags);
+#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
+ /*
+ * We don't need to lock anything here since we're in resume
+ * and nothing else is running, but have disabled IRQs so we
+ * don't try anything else with the interrupt list from there.
+ */
+ list_for_each_entry(entry, &active_fds, list) {
+ enum um_irq_type t;
+
+ for (t = 0; t < NUM_IRQ_TYPES; t++) {
+ struct irq_reg *reg = &entry->reg[t];
+
+ if (reg->pending_on_resume) {
+ irq_enter();
+ generic_handle_irq(reg->irq);
+ irq_exit();
+ reg->pending_on_resume = false;
+ }
+ }
+ }
+#endif
+
+ spin_lock(&irq_lock);
+ list_for_each_entry(entry, &active_fds, list) {
+ if (entry->suspended) {
+ int err = os_set_fd_async(entry->fd);
+
+ WARN(err < 0, "os_set_fd_async returned %d\n", err);
+ entry->suspended = false;
+
+ if (entry->sigio_workaround) {
+ err = __add_sigio_fd(entry->fd);
+ WARN(err < 0, "add_sigio_returned %d\n", err);
+ }
+ }
+ }
+ spin_unlock_irqrestore(&irq_lock, flags);
+
+ irqs_suspended = false;
+ send_sigio_to_self();
+}
+
+static int normal_irq_set_wake(struct irq_data *d, unsigned int on)
+{
+ struct irq_entry *entry;
+ unsigned long flags;
+
+ spin_lock_irqsave(&irq_lock, flags);
+ list_for_each_entry(entry, &active_fds, list) {
+ enum um_irq_type t;
+
+ for (t = 0; t < NUM_IRQ_TYPES; t++) {
+ if (!entry->reg[t].events)
+ continue;
+
+ if (entry->reg[t].irq != d->irq)
+ continue;
+ entry->reg[t].wakeup = on;
+ goto unlock;
+ }
+ }
+unlock:
+ spin_unlock_irqrestore(&irq_lock, flags);
+ return 0;
+}
+#else
+#define normal_irq_set_wake NULL
+#endif
+
+/*
+ * 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 other 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,
+ .irq_set_wake = normal_irq_set_wake,
+};
+
+static struct irq_chip alarm_irq_type = {
+ .name = "SIGALRM",
+ .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, &alarm_irq_type, handle_edge_irq);
+
+ for (i = 1; i < UM_LAST_SIGNAL_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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