diff options
Diffstat (limited to 'drivers/lguest/lguest_user.c')
-rw-r--r-- | drivers/lguest/lguest_user.c | 359 |
1 files changed, 359 insertions, 0 deletions
diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c new file mode 100644 index 0000000..e73a000 --- /dev/null +++ b/drivers/lguest/lguest_user.c @@ -0,0 +1,359 @@ +/*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, pagetable, entry point and kernel address + * offset. A read will run the Guest until something happens, such as a signal + * or the Guest doing a NOTIFY out to the Launcher. :*/ +#include <linux/uaccess.h> +#include <linux/miscdevice.h> +#include <linux/fs.h> +#include <linux/sched.h> +#include "lg.h" + +/*L:055 When something happens, the Waker process needs a way to stop the + * kernel running the Guest and return to the Launcher. So the Waker writes + * LHREQ_BREAK and the value "1" to /dev/lguest to do this. Once the Launcher + * has done whatever needs attention, it writes LHREQ_BREAK and "0" to release + * the Waker. */ +static int break_guest_out(struct lg_cpu *cpu, const unsigned long __user*input) +{ + unsigned long on; + + /* Fetch whether they're turning break on or off. */ + if (get_user(on, input) != 0) + return -EFAULT; + + if (on) { + cpu->break_out = 1; + /* Pop it out of the Guest (may be running on different CPU) */ + wake_up_process(cpu->tsk); + /* Wait for them to reset it */ + return wait_event_interruptible(cpu->break_wq, !cpu->break_out); + } else { + cpu->break_out = 0; + wake_up(&cpu->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 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_bit(irq, cpu->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; + 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_notify) + cpu->pending_notify = 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 the 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 - id), struct lguest, cpus[0]); + 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 bottom 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); + + /* Initialize the queue for the Waker to wait on */ + init_waitqueue_head(&cpu->break_wq); + + /* 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 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. + * + * 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). + */ +static int initialize(struct file *file, const unsigned long __user *input) +{ + /* "struct lguest" contains everything 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]; + + /* This is the first cpu (cpu 0) and it will start booting at args[3] */ + err = lg_cpu_start(&lg->cpus[0], 0, args[3]); + if (err) + goto release_guest; + + /* 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[2]); + 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); +release_guest: + 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. + * + * 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; + + /* If you're not the task which owns the Guest, all you can do + * is break the Launcher out of running the Guest. */ + if (current != cpu->tsk && req != LHREQ_BREAK) + return -EPERM; + } + + switch (req) { + case LHREQ_INITIALIZE: + return initialize(file, input); + case LHREQ_IRQ: + return user_send_irq(cpu, input); + case LHREQ_BREAK: + return break_guest_out(cpu, 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; + 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); + /* 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, 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 = { + .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); +} |