1 files changed, 382 insertions, 0 deletions
diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c
new file mode 100644
index 00000000000..80d1b58c769
--- /dev/null
+++ b/drivers/lguest/lguest_user.c
@@ -0,0 +1,382 @@
+/*P:200 This contains all the /dev/lguest code, whereby the userspace launcher
+ * controls and communicates with the Guest.  For example, the first write will
+ * tell us the memory size, pagetable, entry point and kernel address offset.
+ * A read will run the Guest until a signal is pending (-EINTR), or the Guest
+ * does a DMA out to the Launcher.  Writes are also used to get a DMA buffer
+ * registered by the Guest and to send the Guest an interrupt. :*/
+#include <linux/uaccess.h>
+#include <linux/miscdevice.h>
+#include <linux/fs.h>
+#include "lg.h"
+
+/*L:030 setup_regs() doesn't really belong in this file, but it gives us an
+ * early glimpse deeper into the Host so it's worth having here.
+ *
+ * Most of the Guest's registers are left alone: we used get_zeroed_page() to
+ * allocate the structure, so they will be 0. */
+static void setup_regs(struct lguest_regs *regs, unsigned long start)
+{
+	/* There are four "segment" registers which the Guest needs to boot:
+	 * The "code segment" register (cs) refers to the kernel code segment
+	 * __KERNEL_CS, and the "data", "extra" and "stack" segment registers
+	 * refer to the kernel data segment __KERNEL_DS.
+	 *
+	 * The privilege level is packed into the lower bits.  The Guest runs
+	 * at privilege level 1 (GUEST_PL).*/
+	regs->ds = regs->es = regs->ss = __KERNEL_DS|GUEST_PL;
+	regs->cs = __KERNEL_CS|GUEST_PL;
+
+	/* The "eflags" register contains miscellaneous flags.  Bit 1 (0x002)
+	 * is supposed to always be "1".  Bit 9 (0x200) controls whether
+	 * interrupts are enabled.  We always leave interrupts enabled while
+	 * running the Guest. */
+	regs->eflags = 0x202;
+
+	/* The "Extended Instruction Pointer" register says where the Guest is
+	 * running. */
+	regs->eip = start;
+
+	/* %esi points to our boot information, at physical address 0, so don't
+	 * touch it. */
+}
+
+/*L:310 To send DMA into the Guest, the Launcher needs to be able to ask for a
+ * DMA buffer.  This is done by writing LHREQ_GETDMA and the key to
+ * /dev/lguest. */
+static long user_get_dma(struct lguest *lg, const u32 __user *input)
+{
+	unsigned long key, udma, irq;
+
+	/* Fetch the key they wrote to us. */
+	if (get_user(key, input) != 0)
+		return -EFAULT;
+	/* Look for a free Guest DMA buffer bound to that key. */
+	udma = get_dma_buffer(lg, key, &irq);
+	if (!udma)
+		return -ENOENT;
+
+	/* We need to tell the Launcher what interrupt the Guest expects after
+	 * the buffer is filled.  We stash it in udma->used_len. */
+	lgwrite_u32(lg, udma + offsetof(struct lguest_dma, used_len), irq);
+
+	/* The (guest-physical) address of the DMA buffer is returned from
+	 * the write(). */
+	return udma;
+}
+
+/*L:315 To force the Guest to stop running and return to the Launcher, the
+ * Waker sets writes LHREQ_BREAK and the value "1" to /dev/lguest.  The
+ * Launcher then writes LHREQ_BREAK and "0" to release the Waker. */
+static int break_guest_out(struct lguest *lg, const u32 __user *input)
+{
+	unsigned long on;
+
+	/* Fetch whether they're turning break on or off.. */
+	if (get_user(on, input) != 0)
+		return -EFAULT;
+
+	if (on) {
+		lg->break_out = 1;
+		/* Pop it out (may be running on different CPU) */
+		wake_up_process(lg->tsk);
+		/* Wait for them to reset it */
+		return wait_event_interruptible(lg->break_wq, !lg->break_out);
+	} else {
+		lg->break_out = 0;
+		wake_up(&lg->break_wq);
+		return 0;
+	}
+}
+
+/*L:050 Sending an interrupt is done by writing LHREQ_IRQ and an interrupt
+ * number to /dev/lguest. */
+static int user_send_irq(struct lguest *lg, const u32 __user *input)
+{
+	u32 irq;
+
+	if (get_user(irq, input) != 0)
+		return -EFAULT;
+	if (irq >= LGUEST_IRQS)
+		return -EINVAL;
+	/* Next time the Guest runs, the core code will see if it can deliver
+	 * this interrupt. */
+	set_bit(irq, lg->irqs_pending);
+	return 0;
+}
+
+/*L:040 Once our Guest is initialized, the Launcher makes it run by reading
+ * from /dev/lguest. */
+static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
+{
+	struct lguest *lg = file->private_data;
+
+	/* You must write LHREQ_INITIALIZE first! */
+	if (!lg)
+		return -EINVAL;
+
+	/* If you're not the task which owns the guest, go away. */
+	if (current != lg->tsk)
+		return -EPERM;
+
+	/* If the guest is already dead, we indicate why */
+	if (lg->dead) {
+		size_t len;
+
+		/* lg->dead either contains an error code, or a string. */
+		if (IS_ERR(lg->dead))
+			return PTR_ERR(lg->dead);
+
+		/* We can only return as much as the buffer they read with. */
+		len = min(size, strlen(lg->dead)+1);
+		if (copy_to_user(user, lg->dead, len) != 0)
+			return -EFAULT;
+		return len;
+	}
+
+	/* If we returned from read() last time because the Guest sent DMA,
+	 * clear the flag. */
+	if (lg->dma_is_pending)
+		lg->dma_is_pending = 0;
+
+	/* Run the Guest until something interesting happens. */
+	return run_guest(lg, (unsigned long __user *)user);
+}
+
+/*L:020 The initialization write supplies 4 32-bit values (in addition to the
+ * 32-bit LHREQ_INITIALIZE value).  These are:
+ *
+ * pfnlimit: The highest (Guest-physical) page number the Guest should be
+ * allowed to access.  The Launcher has to live in Guest memory, so it sets
+ * this to ensure the Guest can't reach it.
+ *
+ * pgdir: The (Guest-physical) address of the top of the initial Guest
+ * pagetables (which are set up by the Launcher).
+ *
+ * start: The first instruction to execute ("eip" in x86-speak).
+ *
+ * page_offset: The PAGE_OFFSET constant in the Guest kernel.  We should
+ * probably wean the code off this, but it's a very useful constant!  Any
+ * address above this is within the Guest kernel, and any kernel address can
+ * quickly converted from physical to virtual by adding PAGE_OFFSET.  It's
+ * 0xC0000000 (3G) by default, but it's configurable at kernel build time.
+ */
+static int initialize(struct file *file, const u32 __user *input)
+{
+	/* "struct lguest" contains everything we (the Host) know about a
+	 * Guest. */
+	struct lguest *lg;
+	int err, i;
+	u32 args[4];
+
+	/* We grab the Big Lguest lock, which protects the global array
+	 * "lguests" and multiple simultaneous initializations. */
+	mutex_lock(&lguest_lock);
+	/* You can't initialize twice!  Close the device and start again... */
+	if (file->private_data) {
+		err = -EBUSY;
+		goto unlock;
+	}
+
+	if (copy_from_user(args, input, sizeof(args)) != 0) {
+		err = -EFAULT;
+		goto unlock;
+	}
+
+	/* Find an unused guest. */
+	i = find_free_guest();
+	if (i < 0) {
+		err = -ENOSPC;
+		goto unlock;
+	}
+	/* OK, we have an index into the "lguest" array: "lg" is a convenient
+	 * pointer. */
+	lg = &lguests[i];
+
+	/* Populate the easy fields of our "struct lguest" */
+	lg->guestid = i;
+	lg->pfn_limit = args[0];
+	lg->page_offset = args[3];
+
+	/* We need a complete page for the Guest registers: they are accessible
+	 * to the Guest and we can only grant it access to whole pages. */
+	lg->regs_page = get_zeroed_page(GFP_KERNEL);
+	if (!lg->regs_page) {
+		err = -ENOMEM;
+		goto release_guest;
+	}
+	/* We actually put the registers at the bottom of the page. */
+	lg->regs = (void *)lg->regs_page + PAGE_SIZE - sizeof(*lg->regs);
+
+	/* Initialize the Guest's shadow page tables, using the toplevel
+	 * address the Launcher gave us.  This allocates memory, so can
+	 * fail. */
+	err = init_guest_pagetable(lg, args[1]);
+	if (err)
+		goto free_regs;
+
+	/* Now we initialize the Guest's registers, handing it the start
+	 * address. */
+	setup_regs(lg->regs, args[2]);
+
+	/* There are a couple of GDT entries the Guest expects when first
+	 * booting. */
+	setup_guest_gdt(lg);
+
+	/* The timer for lguest's clock needs initialization. */
+	init_clockdev(lg);
+
+	/* We keep a pointer to the Launcher task (ie. current task) for when
+	 * other Guests want to wake this one (inter-Guest I/O). */
+	lg->tsk = current;
+	/* We need to keep a pointer to the Launcher's memory map, because if
+	 * the Launcher dies we need to clean it up.  If we don't keep a
+	 * reference, it is destroyed before close() is called. */
+	lg->mm = get_task_mm(lg->tsk);
+
+	/* Initialize the queue for the waker to wait on */
+	init_waitqueue_head(&lg->break_wq);
+
+	/* We remember which CPU's pages this Guest used last, for optimization
+	 * when the same Guest runs on the same CPU twice. */
+	lg->last_pages = NULL;
+
+	/* We keep our "struct lguest" in the file's private_data. */
+	file->private_data = lg;
+
+	mutex_unlock(&lguest_lock);
+
+	/* And because this is a write() call, we return the length used. */
+	return sizeof(args);
+
+free_regs:
+	free_page(lg->regs_page);
+release_guest:
+	memset(lg, 0, sizeof(*lg));
+unlock:
+	mutex_unlock(&lguest_lock);
+	return err;
+}
+
+/*L:010 The first operation the Launcher does must be a write.  All writes
+ * start with a 32 bit number: for the first write this must be
+ * LHREQ_INITIALIZE to set up the Guest.  After that the Launcher can use
+ * writes of other values to get DMA buffers and send interrupts. */
+static ssize_t write(struct file *file, const char __user *input,
+		     size_t size, loff_t *off)
+{
+	/* Once the guest is initialized, we hold the "struct lguest" in the
+	 * file private data. */
+	struct lguest *lg = file->private_data;
+	u32 req;
+
+	if (get_user(req, input) != 0)
+		return -EFAULT;
+	input += sizeof(req);
+
+	/* If you haven't initialized, you must do that first. */
+	if (req != LHREQ_INITIALIZE && !lg)
+		return -EINVAL;
+
+	/* Once the Guest is dead, all you can do is read() why it died. */
+	if (lg && lg->dead)
+		return -ENOENT;
+
+	/* If you're not the task which owns the Guest, you can only break */
+	if (lg && current != lg->tsk && req != LHREQ_BREAK)
+		return -EPERM;
+
+	switch (req) {
+	case LHREQ_INITIALIZE:
+		return initialize(file, (const u32 __user *)input);
+	case LHREQ_GETDMA:
+		return user_get_dma(lg, (const u32 __user *)input);
+	case LHREQ_IRQ:
+		return user_send_irq(lg, (const u32 __user *)input);
+	case LHREQ_BREAK:
+		return break_guest_out(lg, (const u32 __user *)input);
+	default:
+		return -EINVAL;
+	}
+}
+
+/*L:060 The final piece of interface code is the close() routine.  It reverses
+ * everything done in initialize().  This is usually called because the
+ * Launcher exited.
+ *
+ * Note that the close routine returns 0 or a negative error number: it can't
+ * really fail, but it can whine.  I blame Sun for this wart, and K&R C for
+ * letting them do it. :*/
+static int close(struct inode *inode, struct file *file)
+{
+	struct lguest *lg = file->private_data;
+
+	/* If we never successfully initialized, there's nothing to clean up */
+	if (!lg)
+		return 0;
+
+	/* We need the big lock, to protect from inter-guest I/O and other
+	 * Launchers initializing guests. */
+	mutex_lock(&lguest_lock);
+	/* Cancels the hrtimer set via LHCALL_SET_CLOCKEVENT. */
+	hrtimer_cancel(&lg->hrt);
+	/* Free any DMA buffers the Guest had bound. */
+	release_all_dma(lg);
+	/* Free up the shadow page tables for the Guest. */
+	free_guest_pagetable(lg);
+	/* Now all the memory cleanups are done, it's safe to release the
+	 * Launcher's memory management structure. */
+	mmput(lg->mm);
+	/* If lg->dead doesn't contain an error code it will be NULL or a
+	 * kmalloc()ed string, either of which is ok to hand to kfree(). */
+	if (!IS_ERR(lg->dead))
+		kfree(lg->dead);
+	/* We can free up the register page we allocated. */
+	free_page(lg->regs_page);
+	/* We clear the entire structure, which also marks it as free for the
+	 * next user. */
+	memset(lg, 0, sizeof(*lg));
+	/* Release lock and exit. */
+	mutex_unlock(&lguest_lock);
+
+	return 0;
+}
+
+/*L:000
+ * Welcome to our journey through the Launcher!
+ *
+ * The Launcher is the Host userspace program which sets up, runs and services
+ * the Guest.  In fact, many comments in the Drivers which refer to "the Host"
+ * doing things are inaccurate: the Launcher does all the device handling for
+ * the Guest.  The Guest can't tell what's done by the the Launcher and what by
+ * the Host.
+ *
+ * Just to confuse you: to the Host kernel, the Launcher *is* the Guest and we
+ * shall see more of that later.
+ *
+ * We begin our understanding with the Host kernel interface which the Launcher
+ * uses: reading and writing a character device called /dev/lguest.  All the
+ * work happens in the read(), write() and close() routines: */
+static struct file_operations lguest_fops = {
+	.owner	 = THIS_MODULE,
+	.release = close,
+	.write	 = write,
+	.read	 = read,
+};
+
+/* This is a textbook example of a "misc" character device.  Populate a "struct
+ * miscdevice" and register it with misc_register(). */
+static struct miscdevice lguest_dev = {
+	.minor	= MISC_DYNAMIC_MINOR,
+	.name	= "lguest",
+	.fops	= &lguest_fops,
+};
+
+int __init lguest_device_init(void)
+{
+	return misc_register(&lguest_dev);
+}
+
+void __exit lguest_device_remove(void)
+{
+	misc_deregister(&lguest_dev);
+}