diff options
Diffstat (limited to 'drivers/lguest/lguest_user.c')
| -rw-r--r-- | drivers/lguest/lguest_user.c | 574 |
1 files changed, 367 insertions, 207 deletions
diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c index 80d1b58c769..4263f4cc8c5 100644 --- a/drivers/lguest/lguest_user.c +++ b/drivers/lguest/lguest_user.c @@ -1,124 +1,224 @@ -/*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. :*/ +/*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 doing a NOTIFY out to the Launcher. There is + * also a way for the Launcher to attach eventfds to particular NOTIFY + * values instead of returning from the read() call. +:*/ #include <linux/uaccess.h> #include <linux/miscdevice.h> #include <linux/fs.h> +#include <linux/sched.h> +#include <linux/eventfd.h> +#include <linux/file.h> +#include <linux/slab.h> +#include <linux/export.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. +/*L:056 + * Before we move on, let's jump ahead and look at what the kernel does when + * it needs to look up the eventfds. That will complete our picture of how we + * use RCU. * - * 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) + * The notification value is in cpu->pending_notify: we return true if it went + * to an eventfd. + */ +bool send_notify_to_eventfd(struct lg_cpu *cpu) { - /* 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. + unsigned int i; + struct lg_eventfd_map *map; + + /* + * This "rcu_read_lock()" helps track when someone is still looking at + * the (RCU-using) eventfds array. It's not actually a lock at all; + * indeed it's a noop in many configurations. (You didn't expect me to + * explain all the RCU secrets here, did you?) + */ + rcu_read_lock(); + /* + * rcu_dereference is the counter-side of rcu_assign_pointer(); it + * makes sure we don't access the memory pointed to by + * cpu->lg->eventfds before cpu->lg->eventfds is set. Sounds crazy, + * but Alpha allows this! Paul McKenney points out that a really + * aggressive compiler could have the same effect: + * http://lists.ozlabs.org/pipermail/lguest/2009-July/001560.html * - * 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. */ + * So play safe, use rcu_dereference to get the rcu-protected pointer: + */ + map = rcu_dereference(cpu->lg->eventfds); + /* + * Simple array search: even if they add an eventfd while we do this, + * we'll continue to use the old array and just won't see the new one. + */ + for (i = 0; i < map->num; i++) { + if (map->map[i].addr == cpu->pending_notify) { + eventfd_signal(map->map[i].event, 1); + cpu->pending_notify = 0; + break; + } + } + /* We're done with the rcu-protected variable cpu->lg->eventfds. */ + rcu_read_unlock(); + + /* If we cleared the notification, it's because we found a match. */ + return cpu->pending_notify == 0; } -/*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) +/*L:055 + * One of the more tricksy tricks in the Linux Kernel is a technique called + * Read Copy Update. Since one point of lguest is to teach lguest journeyers + * about kernel coding, I use it here. (In case you're curious, other purposes + * include learning about virtualization and instilling a deep appreciation for + * simplicity and puppies). + * + * We keep a simple array which maps LHCALL_NOTIFY values to eventfds, but we + * add new eventfds without ever blocking readers from accessing the array. + * The current Launcher only does this during boot, so that never happens. But + * Read Copy Update is cool, and adding a lock risks damaging even more puppies + * than this code does. + * + * We allocate a brand new one-larger array, copy the old one and add our new + * element. Then we make the lg eventfd pointer point to the new array. + * That's the easy part: now we need to free the old one, but we need to make + * sure no slow CPU somewhere is still looking at it. That's what + * synchronize_rcu does for us: waits until every CPU has indicated that it has + * moved on to know it's no longer using the old one. + * + * If that's unclear, see http://en.wikipedia.org/wiki/Read-copy-update. + */ +static int add_eventfd(struct lguest *lg, unsigned long addr, int fd) { - unsigned long key, udma, irq; + struct lg_eventfd_map *new, *old = lg->eventfds; - /* 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; + /* + * We don't allow notifications on value 0 anyway (pending_notify of + * 0 means "nothing pending"). + */ + if (!addr) + return -EINVAL; + + /* + * Replace the old array with the new one, carefully: others can + * be accessing it at the same time. + */ + new = kmalloc(sizeof(*new) + sizeof(new->map[0]) * (old->num + 1), + GFP_KERNEL); + if (!new) + return -ENOMEM; + + /* First make identical copy. */ + memcpy(new->map, old->map, sizeof(old->map[0]) * old->num); + new->num = old->num; + + /* Now append new entry. */ + new->map[new->num].addr = addr; + new->map[new->num].event = eventfd_ctx_fdget(fd); + if (IS_ERR(new->map[new->num].event)) { + int err = PTR_ERR(new->map[new->num].event); + kfree(new); + return err; + } + new->num++; + + /* + * Now put new one in place: rcu_assign_pointer() is a fancy way of + * doing "lg->eventfds = new", but it uses memory barriers to make + * absolutely sure that the contents of "new" written above is nailed + * down before we actually do the assignment. + * + * We have to think about these kinds of things when we're operating on + * live data without locks. + */ + rcu_assign_pointer(lg->eventfds, new); + + /* + * We're not in a big hurry. Wait until no one's looking at old + * version, then free it. + */ + synchronize_rcu(); + kfree(old); + + return 0; } -/*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) +/*L:052 + * Receiving notifications from the Guest is usually done by attaching a + * particular LHCALL_NOTIFY value to an event filedescriptor. The eventfd will + * become readable when the Guest does an LHCALL_NOTIFY with that value. + * + * This is really convenient for processing each virtqueue in a separate + * thread. + */ +static int attach_eventfd(struct lguest *lg, const unsigned long __user *input) { - unsigned long on; + unsigned long addr, fd; + int err; - /* Fetch whether they're turning break on or off.. */ - if (get_user(on, input) != 0) + if (get_user(addr, input) != 0) + return -EFAULT; + input++; + if (get_user(fd, 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; - } + /* + * Just make sure two callers don't add eventfds at once. We really + * only need to lock against callers adding to the same Guest, so using + * the Big Lguest Lock is overkill. But this is setup, not a fast path. + */ + mutex_lock(&lguest_lock); + err = add_eventfd(lg, addr, fd); + mutex_unlock(&lguest_lock); + + return err; } -/*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) +/*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) { - u32 irq; + 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_bit(irq, lg->irqs_pending); + + /* + * Next time the Guest runs, the core code will see if it can deliver + * this interrupt. + */ + set_interrupt(cpu, irq); return 0; } -/*L:040 Once our Guest is initialized, the Launcher makes it run by reading - * from /dev/lguest. */ +/*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; - /* If you're not the task which owns the guest, go away. */ - if (current != lg->tsk) + /* 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 the Guest is already dead, we indicate why */ if (lg->dead) { size_t len; @@ -133,43 +233,98 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) 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; + /* + * If we returned from read() last time because the Guest sent I/O, + * clear the flag. + */ + if (cpu->pending_notify) + cpu->pending_notify = 0; /* Run the Guest until something interesting happens. */ - return run_guest(lg, (unsigned long __user *)user); + 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 4 32-bit values (in addition to the - * 32-bit LHREQ_INITIALIZE value). These are: +/*L:020 + * The initialization write supplies 3 pointer sized (32 or 64 bit) values (in + * addition to the 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. + * base: The start of the Guest-physical memory inside the Launcher memory. * - * pgdir: The (Guest-physical) address of the top of the initial Guest - * pagetables (which are set up by the Launcher). + * 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). - * - * 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) +static int initialize(struct file *file, const unsigned long __user *input) { - /* "struct lguest" contains everything we (the Host) know about a - * Guest. */ + /* "struct lguest" contains all we (the Host) know about a Guest. */ struct lguest *lg; - int err, i; - u32 args[4]; + int err; + unsigned long args[3]; - /* We grab the Big Lguest lock, which protects the global array - * "lguests" and multiple simultaneous initializations. */ + /* + * 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) { @@ -182,63 +337,35 @@ static int initialize(struct file *file, const u32 __user *input) goto unlock; } - /* Find an unused guest. */ - i = find_free_guest(); - if (i < 0) { - err = -ENOSPC; + lg = kzalloc(sizeof(*lg), GFP_KERNEL); + if (!lg) { + err = -ENOMEM; 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) { + lg->eventfds = kmalloc(sizeof(*lg->eventfds), GFP_KERNEL); + if (!lg->eventfds) { err = -ENOMEM; - goto release_guest; + goto free_lg; } - /* 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]); + lg->eventfds->num = 0; - /* 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); + /* Populate the easy fields of our "struct lguest" */ + lg->mem_base = (void __user *)args[0]; + lg->pfn_limit = args[1]; - /* Initialize the queue for the waker to wait on */ - init_waitqueue_head(&lg->break_wq); + /* 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_eventfds; - /* 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; + /* + * 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; @@ -249,92 +376,121 @@ static int initialize(struct file *file, const u32 __user *input) return sizeof(args); free_regs: - free_page(lg->regs_page); -release_guest: - memset(lg, 0, sizeof(*lg)); + /* FIXME: This should be in free_vcpu */ + free_page(lg->cpus[0].regs_page); +free_eventfds: + kfree(lg->eventfds); +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 a 32 bit number: for the first write this must be +/*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 get DMA buffers and send interrupts. */ -static ssize_t write(struct file *file, const char __user *input, + * 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. */ + /* + * Once the Guest is initialized, we hold the "struct lguest" in the + * file private data. + */ struct lguest *lg = file->private_data; - u32 req; + 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 += sizeof(req); + input++; /* 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; + 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, (const u32 __user *)input); - case LHREQ_GETDMA: - return user_get_dma(lg, (const u32 __user *)input); + return initialize(file, 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); + return user_send_irq(cpu, input); + case LHREQ_EVENTFD: + return attach_eventfd(lg, input); default: return -EINVAL; } } -/*L:060 The final piece of interface code is the close() routine. It reverses +/*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. :*/ + * 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. */ + /* + * 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(). */ + + 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); + } + + /* Release any eventfds they registered. */ + for (i = 0; i < lg->eventfds->num; i++) + eventfd_ctx_put(lg->eventfds->map[i].event); + kfree(lg->eventfds); + + /* + * 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)); + /* Free the memory allocated to the lguest_struct */ + kfree(lg); /* Release lock and exit. */ mutex_unlock(&lguest_lock); @@ -347,24 +503,28 @@ static int close(struct inode *inode, struct file *file) * 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. + * 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 struct file_operations lguest_fops = { + * work happens in the read(), write() and close() routines: + */ +static const struct file_operations lguest_fops = { .owner = THIS_MODULE, .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(). */ +/* + * 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", |