--- /dev/null
+/*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 Guest's memory layout and entry
+ * point. A read will run the Guest until something happens, such as
+ * a signal or the Guest accessing a device.
+:*/
+#include <linux/uaccess.h>
+#include <linux/miscdevice.h>
+#include <linux/fs.h>
+#include <linux/sched.h>
+#include <linux/file.h>
+#include <linux/slab.h>
+#include <linux/export.h>
+#include "lg.h"
+
+/*L:052
+ The Launcher can get the registers, and also set some of them.
+*/
+static int getreg_setup(struct lg_cpu *cpu, const unsigned long __user *input)
+{
+ unsigned long which;
+
+ /* We re-use the ptrace structure to specify which register to read. */
+ if (get_user(which, input) != 0)
+ return -EFAULT;
+
+ /*
+ * We set up the cpu register pointer, and their next read will
+ * actually get the value (instead of running the guest).
+ *
+ * The last argument 'true' says we can access any register.
+ */
+ cpu->reg_read = lguest_arch_regptr(cpu, which, true);
+ if (!cpu->reg_read)
+ return -ENOENT;
+
+ /* And because this is a write() call, we return the length used. */
+ return sizeof(unsigned long) * 2;
+}
+
+static int setreg(struct lg_cpu *cpu, const unsigned long __user *input)
+{
+ unsigned long which, value, *reg;
+
+ /* We re-use the ptrace structure to specify which register to read. */
+ if (get_user(which, input) != 0)
+ return -EFAULT;
+ input++;
+ if (get_user(value, input) != 0)
+ return -EFAULT;
+
+ /* The last argument 'false' means we can't access all registers. */
+ reg = lguest_arch_regptr(cpu, which, false);
+ if (!reg)
+ return -ENOENT;
+
+ *reg = value;
+
+ /* And because this is a write() call, we return the length used. */
+ return sizeof(unsigned long) * 3;
+}
+
+/*L:050
+ * Sending an interrupt is done by writing LHREQ_IRQ and an interrupt
+ * number to /dev/lguest.
+ */
+static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input)
+{
+ unsigned long 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_interrupt(cpu, irq);
+ return 0;
+}
+
+/*L:053
+ * Deliver a trap: this is used by the Launcher if it can't emulate
+ * an instruction.
+ */
+static int trap(struct lg_cpu *cpu, const unsigned long __user *input)
+{
+ unsigned long trapnum;
+
+ if (get_user(trapnum, input) != 0)
+ return -EFAULT;
+
+ if (!deliver_trap(cpu, trapnum))
+ return -EINVAL;
+
+ 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;
+ struct lg_cpu *cpu;
+ unsigned int cpu_id = *o;
+
+ /* You must write LHREQ_INITIALIZE first! */
+ if (!lg)
+ return -EINVAL;
+
+ /* Watch out for arbitrary vcpu indexes! */
+ if (cpu_id >= lg->nr_cpus)
+ return -EINVAL;
+
+ cpu = &lg->cpus[cpu_id];
+
+ /* If you're not the task which owns the Guest, go away. */
+ if (current != cpu->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 I/O,
+ * clear the flag.
+ */
+ if (cpu->pending.trap)
+ cpu->pending.trap = 0;
+
+ /* Run the Guest until something interesting happens. */
+ return run_guest(cpu, (unsigned long __user *)user);
+}
+
+/*L:025
+ * This actually initializes a CPU. For the moment, a Guest is only
+ * uniprocessor, so "id" is always 0.
+ */
+static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip)
+{
+ /* We have a limited number of CPUs in the lguest struct. */
+ if (id >= ARRAY_SIZE(cpu->lg->cpus))
+ return -EINVAL;
+
+ /* Set up this CPU's id, and pointer back to the lguest struct. */
+ cpu->id = id;
+ cpu->lg = container_of(cpu, struct lguest, cpus[id]);
+ cpu->lg->nr_cpus++;
+
+ /* Each CPU has a timer it can set. */
+ init_clockdev(cpu);
+
+ /*
+ * 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.
+ */
+ cpu->regs_page = get_zeroed_page(GFP_KERNEL);
+ if (!cpu->regs_page)
+ return -ENOMEM;
+
+ /* We actually put the registers at the end of the page. */
+ cpu->regs = (void *)cpu->regs_page + PAGE_SIZE - sizeof(*cpu->regs);
+
+ /*
+ * Now we initialize the Guest's registers, handing it the start
+ * address.
+ */
+ lguest_arch_setup_regs(cpu, start_ip);
+
+ /*
+ * We keep a pointer to the Launcher task (ie. current task) for when
+ * other Guests want to wake this one (eg. console input).
+ */
+ cpu->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.
+ */
+ cpu->mm = get_task_mm(cpu->tsk);
+
+ /*
+ * We remember which CPU's pages this Guest used last, for optimization
+ * when the same Guest runs on the same CPU twice.
+ */
+ cpu->last_pages = NULL;
+
+ /* No error == success. */
+ return 0;
+}
+
+/*L:020
+ * The initialization write supplies 3 pointer sized (32 or 64 bit) values (in
+ * addition to the LHREQ_INITIALIZE value). These are:
+ *
+ * base: The start of the Guest-physical memory inside the Launcher memory.
+ *
+ * pfnlimit: The highest (Guest-physical) page number the Guest should be
+ * allowed to access. The Guest memory lives inside the Launcher, so it sets
+ * this to ensure the Guest can only reach its own memory.
+ *
+ * start: The first instruction to execute ("eip" in x86-speak).
+ */
+static int initialize(struct file *file, const unsigned long __user *input)
+{
+ /* "struct lguest" contains all we (the Host) know about a Guest. */
+ struct lguest *lg;
+ int err;
+ unsigned long args[4];
+
+ /*
+ * We grab the Big Lguest lock, which protects against 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;
+ }
+
+ lg = kzalloc(sizeof(*lg), GFP_KERNEL);
+ if (!lg) {
+ err = -ENOMEM;
+ goto unlock;
+ }
+
+ /* Populate the easy fields of our "struct lguest" */
+ lg->mem_base = (void __user *)args[0];
+ lg->pfn_limit = args[1];
+ lg->device_limit = args[3];
+
+ /* This is the first cpu (cpu 0) and it will start booting at args[2] */
+ err = lg_cpu_start(&lg->cpus[0], 0, args[2]);
+ if (err)
+ goto free_lg;
+
+ /*
+ * Initialize the Guest's shadow page tables. This allocates
+ * memory, so can fail.
+ */
+ err = init_guest_pagetable(lg);
+ if (err)
+ goto free_regs;
+
+ /* 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:
+ /* FIXME: This should be in free_vcpu */
+ free_page(lg->cpus[0].regs_page);
+free_lg:
+ kfree(lg);
+unlock:
+ mutex_unlock(&lguest_lock);
+ return err;
+}
+
+/*L:010
+ * The first operation the Launcher does must be a write. All writes
+ * start with an unsigned long 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 send interrupts or set up receipt of notifications.
+ *
+ * Note that we overload the "offset" in the /dev/lguest file to indicate what
+ * CPU number we're dealing with. Currently this is always 0 since we only
+ * support uniprocessor Guests, but you can see the beginnings of SMP support
+ * here.
+ */
+static ssize_t write(struct file *file, const char __user *in,
+ 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;
+ const unsigned long __user *input = (const unsigned long __user *)in;
+ unsigned long req;
+ struct lg_cpu *uninitialized_var(cpu);
+ unsigned int cpu_id = *off;
+
+ /* The first value tells us what this request is. */
+ if (get_user(req, input) != 0)
+ return -EFAULT;
+ input++;
+
+ /* If you haven't initialized, you must do that first. */
+ if (req != LHREQ_INITIALIZE) {
+ if (!lg || (cpu_id >= lg->nr_cpus))
+ return -EINVAL;
+ cpu = &lg->cpus[cpu_id];
+
+ /* Once the Guest is dead, you can only read() why it died. */
+ if (lg->dead)
+ return -ENOENT;
+ }
+
+ switch (req) {
+ case LHREQ_INITIALIZE:
+ return initialize(file, input);
+ case LHREQ_IRQ:
+ return user_send_irq(cpu, input);
+ case LHREQ_GETREG:
+ return getreg_setup(cpu, input);
+ case LHREQ_SETREG:
+ return setreg(cpu, input);
+ case LHREQ_TRAP:
+ return trap(cpu, input);
+ default:
+ return -EINVAL;
+ }
+}
+
+static int open(struct inode *inode, struct file *file)
+{
+ file->private_data = NULL;
+
+ return 0;
+}
+
+/*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;
+ unsigned int i;
+
+ /* 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);
+
+ /* Free up the shadow page tables for the Guest. */
+ free_guest_pagetable(lg);
+
+ for (i = 0; i < lg->nr_cpus; i++) {
+ /* Cancels the hrtimer set via LHCALL_SET_CLOCKEVENT. */
+ hrtimer_cancel(&lg->cpus[i].hrt);
+ /* We can free up the register page we allocated. */
+ free_page(lg->cpus[i].regs_page);
+ /*
+ * Now all the memory cleanups are done, it's safe to release
+ * the Launcher's memory management structure.
+ */
+ mmput(lg->cpus[i].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);
+ /* Free the memory allocated to the lguest_struct */
+ kfree(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, but the Guest can't know that.
+ *
+ * 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 const struct file_operations lguest_fops = {
+ .owner = THIS_MODULE,
+ .open = open,
+ .release = close,
+ .write = write,
+ .read = read,
+ .llseek = default_llseek,
+};
+/*:*/
+
+/*
+ * 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);
+}
Code Review / kvmfornfv.git / blobdiff