Feather-Trace: add generic ftdev device driver

This patch adds the ftdev device driver, which is used to export
samples collected with Feather-Trace to userspace.

2 files changed, 433 insertions, 1 deletions

diff --git a/litmus/Makefile b/litmus/Makefile
index 4c6130b58bae..bca61e6deb71 100644
--- a/litmus/Makefile
+++ b/litmus/Makefile
@@ -2,4 +2,4 @@
 # Makefile for LITMUS^RT
 #
 
-obj-$(CONFIG_FEATHER_TRACE) += ft_event.o
+obj-$(CONFIG_FEATHER_TRACE) += ft_event.o ftdev.o
diff --git a/litmus/ftdev.c b/litmus/ftdev.c
new file mode 100644
index 000000000000..a3c679d1c5c7
--- /dev/null
+++ b/litmus/ftdev.c
@@ -0,0 +1,432 @@
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/cdev.h>
+#include <asm/uaccess.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/vmalloc.h>
+
+#include <litmus/feather_trace.h>
+#include <litmus/ftdev.h>
+
+struct ft_buffer* alloc_ft_buffer(unsigned int count, size_t size)
+{
+        struct ft_buffer* buf;
+        size_t total = (size + 1) * count;
+        char* mem;
+
+        buf = kmalloc(sizeof(*buf), GFP_KERNEL);
+        if (!buf)
+                return NULL;
+
+
+        mem = vmalloc(total);
+
+        if (!mem) {
+                kfree(buf);
+                return NULL;
+        }
+
+        if (!init_ft_buffer(buf, count, size,
+                            mem + (count * size),  /* markers at the end */
+                            mem)) {                /* buffer objects     */
+                vfree(mem);
+                kfree(buf);
+                return NULL;
+        }
+        return buf;
+}
+
+void free_ft_buffer(struct ft_buffer* buf)
+{
+        if (buf) {
+                vfree(buf->buffer_mem);
+                kfree(buf);
+        }
+}
+
+struct ftdev_event {
+        int id;
+        struct ftdev_event* next;
+};
+
+static int activate(struct ftdev_event** chain, int id)
+{
+        struct ftdev_event* ev = kmalloc(sizeof(*ev), GFP_KERNEL);
+        if (ev) {
+                printk(KERN_INFO
+                       "Enabling feather-trace event %d.\n", (int) id);
+                ft_enable_event(id);
+                ev->id = id;
+                ev->next = *chain;
+                *chain    = ev;
+        }
+        return ev ? 0 : -ENOMEM;
+}
+
+static void deactivate(struct ftdev_event** chain, int id)
+{
+        struct ftdev_event **cur = chain;
+        struct ftdev_event *nxt;
+        while (*cur) {
+                if ((*cur)->id == id) {
+                        nxt   = (*cur)->next;
+                        kfree(*cur);
+                        *cur  = nxt;
+                        printk(KERN_INFO
+                               "Disabling feather-trace event %d.\n", (int) id);
+                        ft_disable_event(id);
+                        break;
+                }
+                cur = &(*cur)->next;
+        }
+}
+
+static int ftdev_open(struct inode *in, struct file *filp)
+{
+        struct ftdev* ftdev;
+        struct ftdev_minor* ftdm;
+        unsigned int buf_idx = iminor(in);
+        int err = 0;
+
+        ftdev = container_of(in->i_cdev, struct ftdev, cdev);
+
+        if (buf_idx >= ftdev->minor_cnt) {
+                err = -ENODEV;
+                goto out;
+        }
+        if (ftdev->can_open && (err = ftdev->can_open(ftdev, buf_idx)))
+                goto out;
+
+        ftdm = ftdev->minor + buf_idx;
+        ftdm->ftdev = ftdev;
+        filp->private_data = ftdm;
+
+        if (mutex_lock_interruptible(&ftdm->lock)) {
+                err = -ERESTARTSYS;
+                goto out;
+        }
+
+        if (!ftdm->readers && ftdev->alloc)
+                err = ftdev->alloc(ftdev, buf_idx);
+        if (0 == err)
+                ftdm->readers++;
+
+        mutex_unlock(&ftdm->lock);
+out:
+        return err;
+}
+
+static int ftdev_release(struct inode *in, struct file *filp)
+{
+        struct ftdev* ftdev;
+        struct ftdev_minor* ftdm;
+        unsigned int buf_idx = iminor(in);
+        int err = 0;
+
+        ftdev = container_of(in->i_cdev, struct ftdev, cdev);
+
+        if (buf_idx >= ftdev->minor_cnt) {
+                err = -ENODEV;
+                goto out;
+        }
+        ftdm = ftdev->minor + buf_idx;
+
+        if (mutex_lock_interruptible(&ftdm->lock)) {
+                err = -ERESTARTSYS;
+                goto out;
+        }
+
+        if (ftdm->readers == 1) {
+                while (ftdm->events)
+                        deactivate(&ftdm->events, ftdm->events->id);
+
+                /* wait for any pending events to complete */
+                set_current_state(TASK_UNINTERRUPTIBLE);
+                schedule_timeout(HZ);
+
+                printk(KERN_ALERT "Failed trace writes: %u\n",
+                       ftdm->buf->failed_writes);
+
+                if (ftdev->free)
+                        ftdev->free(ftdev, buf_idx);
+        }
+
+        ftdm->readers--;
+        mutex_unlock(&ftdm->lock);
+out:
+        return err;
+}
+
+/* based on ft_buffer_read
+ * @returns < 0 : page fault
+ *          = 0 : no data available
+ *          = 1 : one slot copied
+ */
+static int ft_buffer_copy_to_user(struct ft_buffer* buf, char __user *dest)
+{
+        unsigned int idx;
+        int err = 0;
+        if (buf->free_count != buf->slot_count) {
+                /* data available */
+                idx = buf->read_idx % buf->slot_count;
+                if (buf->slots[idx] == SLOT_READY) {
+                        err = copy_to_user(dest, ((char*) buf->buffer_mem) +
+                                           idx * buf->slot_size,
+                                           buf->slot_size);
+                        if (err == 0) {
+                                /* copy ok */
+                                buf->slots[idx] = SLOT_FREE;
+                                buf->read_idx++;
+                                fetch_and_inc(&buf->free_count);
+                                err = 1;
+                        }
+                }
+        }
+        return err;
+}
+
+static ssize_t ftdev_read(struct file *filp,
+                          char __user *to, size_t len, loff_t *f_pos)
+{
+        /*      we ignore f_pos, this is strictly sequential */
+
+        ssize_t err = 0;
+        size_t chunk;
+        int copied;
+        struct ftdev_minor* ftdm = filp->private_data;
+
+        if (mutex_lock_interruptible(&ftdm->lock)) {
+                err = -ERESTARTSYS;
+                goto out;
+        }
+
+
+        chunk = ftdm->buf->slot_size;
+        while (len >= chunk) {
+                copied = ft_buffer_copy_to_user(ftdm->buf, to);
+                if (copied == 1) {
+                        len    -= chunk;
+                        to     += chunk;
+                        err    += chunk;
+                } else if (err == 0 && copied == 0 && ftdm->events) {
+                        /* Only wait if there are any events enabled and only
+                         * if we haven't copied some data yet. We cannot wait
+                         * here with copied data because that data would get
+                         * lost if the task is interrupted (e.g., killed).
+                         */
+                        mutex_unlock(&ftdm->lock);
+                        set_current_state(TASK_INTERRUPTIBLE);
+
+                        schedule_timeout(50);
+
+                        if (signal_pending(current)) {
+                                if (err == 0)
+                                        /* nothing read yet, signal problem */
+                                        err = -ERESTARTSYS;
+                                goto out;
+                        }
+                        if (mutex_lock_interruptible(&ftdm->lock)) {
+                                err = -ERESTARTSYS;
+                                goto out;
+                        }
+                } else if (copied < 0) {
+                        /* page fault */
+                        err = copied;
+                        break;
+                } else
+                        /* nothing left to get, return to user space */
+                        break;
+        }
+        mutex_unlock(&ftdm->lock);
+out:
+        return err;
+}
+
+static long ftdev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+        long err = -ENOIOCTLCMD;
+        struct ftdev_minor* ftdm = filp->private_data;
+
+        if (mutex_lock_interruptible(&ftdm->lock)) {
+                err = -ERESTARTSYS;
+                goto out;
+        }
+
+        /* FIXME: check id against list of acceptable events */
+
+        switch (cmd) {
+        case  FTDEV_ENABLE_CMD:
+                if (activate(&ftdm->events, arg))
+                        err = -ENOMEM;
+                else
+                        err = 0;
+                break;
+
+        case FTDEV_DISABLE_CMD:
+                deactivate(&ftdm->events, arg);
+                err = 0;
+                break;
+
+        default:
+                printk(KERN_DEBUG "ftdev: strange ioctl (%u, %lu)\n", cmd, arg);
+        };
+
+        mutex_unlock(&ftdm->lock);
+out:
+        return err;
+}
+
+static ssize_t ftdev_write(struct file *filp, const char __user *from,
+                           size_t len, loff_t *f_pos)
+{
+        struct ftdev_minor* ftdm = filp->private_data;
+        ssize_t err = -EINVAL;
+        struct ftdev* ftdev = ftdm->ftdev;
+
+        /* dispatch write to buffer-specific code, if available */
+        if (ftdev->write)
+                err = ftdev->write(ftdm->buf, len, from);
+
+        return err;
+}
+
+struct file_operations ftdev_fops = {
+        .owner   = THIS_MODULE,
+        .open    = ftdev_open,
+        .release = ftdev_release,
+        .write   = ftdev_write,
+        .read    = ftdev_read,
+        .unlocked_ioctl = ftdev_ioctl,
+};
+
+int ftdev_init( struct ftdev* ftdev, struct module* owner,
+                const int minor_cnt, const char* name)
+{
+        int i, err;
+
+        BUG_ON(minor_cnt < 1);
+
+        cdev_init(&ftdev->cdev, &ftdev_fops);
+        ftdev->name = name;
+        ftdev->minor_cnt = minor_cnt;
+        ftdev->cdev.owner = owner;
+        ftdev->cdev.ops = &ftdev_fops;
+        ftdev->alloc    = NULL;
+        ftdev->free     = NULL;
+        ftdev->can_open = NULL;
+        ftdev->write    = NULL;
+
+        ftdev->minor = kcalloc(ftdev->minor_cnt, sizeof(*ftdev->minor),
+                        GFP_KERNEL);
+        if (!ftdev->minor) {
+                printk(KERN_WARNING "ftdev(%s): Could not allocate memory\n",
+                        ftdev->name);
+                err = -ENOMEM;
+                goto err_out;
+        }
+
+        for (i = 0; i < ftdev->minor_cnt; i++) {
+                mutex_init(&ftdev->minor[i].lock);
+                ftdev->minor[i].readers = 0;
+                ftdev->minor[i].buf     = NULL;
+                ftdev->minor[i].events  = NULL;
+        }
+
+        ftdev->class = class_create(owner, ftdev->name);
+        if (IS_ERR(ftdev->class)) {
+                err = PTR_ERR(ftdev->class);
+                printk(KERN_WARNING "ftdev(%s): "
+                        "Could not create device class.\n", ftdev->name);
+                goto err_dealloc;
+        }
+
+        return 0;
+
+err_dealloc:
+        kfree(ftdev->minor);
+err_out:
+        return err;
+}
+
+/*
+ * Destroy minor devices up to, but not including, up_to.
+ */
+static void ftdev_device_destroy(struct ftdev* ftdev, unsigned int up_to)
+{
+        dev_t minor_cntr;
+
+        if (up_to < 1)
+                up_to = (ftdev->minor_cnt < 1) ? 0 : ftdev->minor_cnt;
+
+        for (minor_cntr = 0; minor_cntr < up_to; ++minor_cntr)
+                device_destroy(ftdev->class, MKDEV(ftdev->major, minor_cntr));
+}
+
+void ftdev_exit(struct ftdev* ftdev)
+{
+        printk("ftdev(%s): Exiting\n", ftdev->name);
+        ftdev_device_destroy(ftdev, -1);
+        cdev_del(&ftdev->cdev);
+        unregister_chrdev_region(MKDEV(ftdev->major, 0), ftdev->minor_cnt);
+        class_destroy(ftdev->class);
+        kfree(ftdev->minor);
+}
+
+int register_ftdev(struct ftdev* ftdev)
+{
+        struct device **device;
+        dev_t trace_dev_tmp, minor_cntr;
+        int err;
+
+        err = alloc_chrdev_region(&trace_dev_tmp, 0, ftdev->minor_cnt,
+                        ftdev->name);
+        if (err) {
+                printk(KERN_WARNING "ftdev(%s): "
+                       "Could not allocate char. device region (%d minors)\n",
+                       ftdev->name, ftdev->minor_cnt);
+                goto err_out;
+        }
+
+        ftdev->major = MAJOR(trace_dev_tmp);
+
+        err = cdev_add(&ftdev->cdev, trace_dev_tmp, ftdev->minor_cnt);
+        if (err) {
+                printk(KERN_WARNING "ftdev(%s): "
+                       "Could not add cdev for major %u with %u minor(s).\n",
+                       ftdev->name, ftdev->major, ftdev->minor_cnt);
+                goto err_unregister;
+        }
+
+        /* create the minor device(s) */
+        for (minor_cntr = 0; minor_cntr < ftdev->minor_cnt; ++minor_cntr)
+        {
+                trace_dev_tmp = MKDEV(ftdev->major, minor_cntr);
+                device = &ftdev->minor[minor_cntr].device;
+
+                *device = device_create(ftdev->class, NULL, trace_dev_tmp, NULL,
+                                "litmus/%s%d", ftdev->name, minor_cntr);
+                if (IS_ERR(*device)) {
+                        err = PTR_ERR(*device);
+                        printk(KERN_WARNING "ftdev(%s): "
+                                "Could not create device major/minor number "
+                                "%u/%u\n", ftdev->name, ftdev->major,
+                                minor_cntr);
+                        printk(KERN_WARNING "ftdev(%s): "
+                                "will attempt deletion of allocated devices.\n",
+                                ftdev->name);
+                        goto err_minors;
+                }
+        }
+
+        return 0;
+
+err_minors:
+        ftdev_device_destroy(ftdev, minor_cntr);
+        cdev_del(&ftdev->cdev);
+err_unregister:
+        unregister_chrdev_region(MKDEV(ftdev->major, 0), ftdev->minor_cnt);
+err_out:
+        return err;
+}