/*
* Copyright (C) 2017 - Cambridge Greys Ltd
* Copyright (C) 2011 - 2014 Cisco Systems Inc
* Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
* Licensed under the GPL
* 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;
}
