X-Git-Url: http://pilppa.org/gitweb/?a=blobdiff_plain;ds=sidebyside;f=drivers%2Flguest%2Flguest_user.c;h=3b92a61ba8d23b14e1ac8e5b342929a314b669be;hb=4db3531487bdde4027b701da7c1b8d094ae2cc91;hp=e90d7a783dafab8d94002230812758bea7782cfc;hpb=b43035a5ec4deecd43019728ab9347df82dd121f;p=linux-2.6-omap-h63xx.git diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c index e90d7a783da..3b92a61ba8d 100644 --- a/drivers/lguest/lguest_user.c +++ b/drivers/lguest/lguest_user.c @@ -1,49 +1,29 @@ -/* Userspace control of the guest, via /dev/lguest. */ +/*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 #include #include #include "lg.h" -static void setup_regs(struct lguest_regs *regs, unsigned long start) -{ - /* Write out stack in format lguest expects, so we can switch to it. */ - regs->ds = regs->es = regs->ss = __KERNEL_DS|GUEST_PL; - regs->cs = __KERNEL_CS|GUEST_PL; - regs->eflags = 0x202; /* Interrupts enabled. */ - regs->eip = start; - /* esi points to our boot information (physical address 0) */ -} - -/* + addr */ -static long user_get_dma(struct lguest *lg, const u32 __user *input) -{ - unsigned long key, udma, irq; - - if (get_user(key, input) != 0) - return -EFAULT; - udma = get_dma_buffer(lg, key, &irq); - if (!udma) - return -ENOENT; - - /* We put irq number in udma->used_len. */ - lgwrite_u32(lg, udma + offsetof(struct lguest_dma, used_len), irq); - return udma; -} - -/* 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: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 lguest *lg, const unsigned long __user *input) { unsigned long on; - /* Fetch whether they're turning break on or off.. */ + /* 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) */ + /* Pop it out of the Guest (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); @@ -54,59 +34,86 @@ static int break_guest_out(struct lguest *lg, const u32 __user *input) } } -/* + irq */ -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 lguest *lg, 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); 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 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 (lg->dma_is_pending) - lg->dma_is_pending = 0; + /* If we returned from read() last time because the Guest notified, + * clear the flag. */ + if (lg->pending_notify) + lg->pending_notify = 0; + /* Run the Guest until something interesting happens. */ return run_guest(lg, (unsigned long __user *)user); } -/* Take: pfnlimit, pgdir, start, pageoffset. */ -static int initialize(struct file *file, const u32 __user *input) +/*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, i; - u32 args[4]; + int err; + unsigned long args[4]; - /* 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) { err = -EBUSY; goto unlock; @@ -117,60 +124,94 @@ static int initialize(struct file *file, const u32 __user *input) goto unlock; } - i = find_free_guest(); - if (i < 0) { - err = -ENOSPC; + lg = kzalloc(sizeof(*lg), GFP_KERNEL); + if (!lg) { + err = -ENOMEM; goto unlock; } - lg = &lguests[i]; - lg->guestid = i; - lg->pfn_limit = args[0]; - lg->page_offset = args[3]; + + /* Populate the easy fields of our "struct lguest" */ + lg->mem_base = (void __user *)(long)args[0]; + lg->pfn_limit = args[1]; + + /* 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); - err = init_guest_pagetable(lg, args[1]); + /* 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; - setup_regs(lg->regs, args[2]); - setup_guest_gdt(lg); + /* Now we initialize the Guest's registers, handing it the start + * address. */ + lguest_arch_setup_regs(lg, args[3]); + + /* 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)); + kfree(lg); unlock: mutex_unlock(&lguest_lock); return err; } -static ssize_t write(struct file *file, const char __user *input, +/*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. */ +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; - u32 req; + const unsigned long __user *input = (const unsigned long __user *)in; + unsigned long req; 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; @@ -180,45 +221,79 @@ static ssize_t write(struct file *file, const char __user *input, 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); + return user_send_irq(lg, input); case LHREQ_BREAK: - return break_guest_out(lg, (const u32 __user *)input); + return break_guest_out(lg, 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); - 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, 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",