// 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_event;
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;
#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
static bool irqs_pending;
#endif
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 cause a wakeup and mark as pending */
if (irqs_suspended) {
irqs_pending = true;
reg->pending_event = true;
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;
return true;
}
static void irq_do_pending_events(bool timetravel_handlers_only)
{
struct irq_entry *entry;
if (!irqs_pending || timetravel_handlers_only)
return;
irqs_pending = false;
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];
/*
* Any timetravel_handler was invoked already, just
* directly run the IRQ.
*/
if (reg->pending_event) {
irq_enter();
generic_handle_irq(reg->irq);
irq_exit();
reg->pending_event = false;
}
}
}
}
#else
static bool irq_do_timetravel_handler(struct irq_entry *entry,
enum um_irq_type t)
{
return false;
}
static void irq_do_pending_events(bool timetravel_handlers_only)
{
}
#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
reg->pending_event = true;
irqs_pending = true;
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;
/* Flush out pending events that were ignored due to time-travel. */
if (!irqs_suspended)
irq_do_pending_events(timetravel_handlers_only);
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)
{
preempt_disable();
_sigio_handler(regs, irqs_suspended);
preempt_enable();
}
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;
spin_lock_irqsave(&irq_lock, flags);
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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