// 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 #include #include #include #include #include #include #include #include #include #include #include #include #include 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_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, ®->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; }