446 lines
12 KiB
C
446 lines
12 KiB
C
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/*P:200 This contains all the /dev/lguest code, whereby the userspace
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* launcher controls and communicates with the Guest. For example,
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* the first write will tell us the Guest's memory layout and entry
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* point. A read will run the Guest until something happens, such as
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* a signal or the Guest accessing a device.
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:*/
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#include <linux/uaccess.h>
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#include <linux/miscdevice.h>
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#include <linux/fs.h>
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#include <linux/sched.h>
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#include <linux/file.h>
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#include <linux/slab.h>
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#include <linux/export.h>
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#include "lg.h"
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/*L:052
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The Launcher can get the registers, and also set some of them.
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*/
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static int getreg_setup(struct lg_cpu *cpu, const unsigned long __user *input)
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{
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unsigned long which;
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/* We re-use the ptrace structure to specify which register to read. */
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if (get_user(which, input) != 0)
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return -EFAULT;
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/*
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* We set up the cpu register pointer, and their next read will
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* actually get the value (instead of running the guest).
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*
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* The last argument 'true' says we can access any register.
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*/
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cpu->reg_read = lguest_arch_regptr(cpu, which, true);
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if (!cpu->reg_read)
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return -ENOENT;
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/* And because this is a write() call, we return the length used. */
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return sizeof(unsigned long) * 2;
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}
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static int setreg(struct lg_cpu *cpu, const unsigned long __user *input)
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{
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unsigned long which, value, *reg;
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/* We re-use the ptrace structure to specify which register to read. */
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if (get_user(which, input) != 0)
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return -EFAULT;
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input++;
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if (get_user(value, input) != 0)
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return -EFAULT;
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/* The last argument 'false' means we can't access all registers. */
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reg = lguest_arch_regptr(cpu, which, false);
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if (!reg)
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return -ENOENT;
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*reg = value;
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/* And because this is a write() call, we return the length used. */
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return sizeof(unsigned long) * 3;
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}
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/*L:050
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* Sending an interrupt is done by writing LHREQ_IRQ and an interrupt
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* number to /dev/lguest.
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*/
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static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input)
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{
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unsigned long irq;
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if (get_user(irq, input) != 0)
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return -EFAULT;
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if (irq >= LGUEST_IRQS)
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return -EINVAL;
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/*
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* Next time the Guest runs, the core code will see if it can deliver
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* this interrupt.
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*/
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set_interrupt(cpu, irq);
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return 0;
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}
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/*L:053
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* Deliver a trap: this is used by the Launcher if it can't emulate
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* an instruction.
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*/
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static int trap(struct lg_cpu *cpu, const unsigned long __user *input)
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{
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unsigned long trapnum;
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if (get_user(trapnum, input) != 0)
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return -EFAULT;
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if (!deliver_trap(cpu, trapnum))
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return -EINVAL;
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return 0;
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}
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/*L:040
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* Once our Guest is initialized, the Launcher makes it run by reading
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* from /dev/lguest.
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*/
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static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
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{
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struct lguest *lg = file->private_data;
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struct lg_cpu *cpu;
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unsigned int cpu_id = *o;
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/* You must write LHREQ_INITIALIZE first! */
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if (!lg)
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return -EINVAL;
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/* Watch out for arbitrary vcpu indexes! */
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if (cpu_id >= lg->nr_cpus)
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return -EINVAL;
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cpu = &lg->cpus[cpu_id];
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/* If you're not the task which owns the Guest, go away. */
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if (current != cpu->tsk)
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return -EPERM;
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/* If the Guest is already dead, we indicate why */
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if (lg->dead) {
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size_t len;
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/* lg->dead either contains an error code, or a string. */
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if (IS_ERR(lg->dead))
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return PTR_ERR(lg->dead);
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/* We can only return as much as the buffer they read with. */
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len = min(size, strlen(lg->dead)+1);
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if (copy_to_user(user, lg->dead, len) != 0)
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return -EFAULT;
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return len;
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}
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/*
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* If we returned from read() last time because the Guest sent I/O,
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* clear the flag.
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*/
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if (cpu->pending.trap)
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cpu->pending.trap = 0;
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/* Run the Guest until something interesting happens. */
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return run_guest(cpu, (unsigned long __user *)user);
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}
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/*L:025
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* This actually initializes a CPU. For the moment, a Guest is only
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* uniprocessor, so "id" is always 0.
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*/
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static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip)
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{
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/* We have a limited number of CPUs in the lguest struct. */
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if (id >= ARRAY_SIZE(cpu->lg->cpus))
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return -EINVAL;
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/* Set up this CPU's id, and pointer back to the lguest struct. */
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cpu->id = id;
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cpu->lg = container_of(cpu, struct lguest, cpus[id]);
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cpu->lg->nr_cpus++;
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/* Each CPU has a timer it can set. */
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init_clockdev(cpu);
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/*
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* We need a complete page for the Guest registers: they are accessible
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* to the Guest and we can only grant it access to whole pages.
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*/
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cpu->regs_page = get_zeroed_page(GFP_KERNEL);
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if (!cpu->regs_page)
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return -ENOMEM;
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/* We actually put the registers at the end of the page. */
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cpu->regs = (void *)cpu->regs_page + PAGE_SIZE - sizeof(*cpu->regs);
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/*
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* Now we initialize the Guest's registers, handing it the start
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* address.
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*/
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lguest_arch_setup_regs(cpu, start_ip);
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/*
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* We keep a pointer to the Launcher task (ie. current task) for when
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* other Guests want to wake this one (eg. console input).
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*/
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cpu->tsk = current;
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/*
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* We need to keep a pointer to the Launcher's memory map, because if
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* the Launcher dies we need to clean it up. If we don't keep a
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* reference, it is destroyed before close() is called.
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*/
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cpu->mm = get_task_mm(cpu->tsk);
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/*
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* We remember which CPU's pages this Guest used last, for optimization
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* when the same Guest runs on the same CPU twice.
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*/
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cpu->last_pages = NULL;
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/* No error == success. */
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return 0;
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}
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/*L:020
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* The initialization write supplies 3 pointer sized (32 or 64 bit) values (in
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* addition to the LHREQ_INITIALIZE value). These are:
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*
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* base: The start of the Guest-physical memory inside the Launcher memory.
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*
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* pfnlimit: The highest (Guest-physical) page number the Guest should be
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* allowed to access. The Guest memory lives inside the Launcher, so it sets
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* this to ensure the Guest can only reach its own memory.
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*
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* start: The first instruction to execute ("eip" in x86-speak).
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*/
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static int initialize(struct file *file, const unsigned long __user *input)
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{
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/* "struct lguest" contains all we (the Host) know about a Guest. */
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struct lguest *lg;
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int err;
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unsigned long args[4];
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/*
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* We grab the Big Lguest lock, which protects against multiple
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* simultaneous initializations.
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*/
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mutex_lock(&lguest_lock);
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/* You can't initialize twice! Close the device and start again... */
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if (file->private_data) {
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err = -EBUSY;
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goto unlock;
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}
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if (copy_from_user(args, input, sizeof(args)) != 0) {
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err = -EFAULT;
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goto unlock;
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}
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lg = kzalloc(sizeof(*lg), GFP_KERNEL);
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if (!lg) {
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err = -ENOMEM;
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goto unlock;
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}
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/* Populate the easy fields of our "struct lguest" */
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lg->mem_base = (void __user *)args[0];
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lg->pfn_limit = args[1];
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lg->device_limit = args[3];
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/* This is the first cpu (cpu 0) and it will start booting at args[2] */
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err = lg_cpu_start(&lg->cpus[0], 0, args[2]);
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if (err)
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goto free_lg;
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/*
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* Initialize the Guest's shadow page tables. This allocates
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* memory, so can fail.
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*/
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err = init_guest_pagetable(lg);
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if (err)
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goto free_regs;
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/* We keep our "struct lguest" in the file's private_data. */
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file->private_data = lg;
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mutex_unlock(&lguest_lock);
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/* And because this is a write() call, we return the length used. */
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return sizeof(args);
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free_regs:
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/* FIXME: This should be in free_vcpu */
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free_page(lg->cpus[0].regs_page);
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free_lg:
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kfree(lg);
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unlock:
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mutex_unlock(&lguest_lock);
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return err;
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}
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/*L:010
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* The first operation the Launcher does must be a write. All writes
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* start with an unsigned long number: for the first write this must be
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* LHREQ_INITIALIZE to set up the Guest. After that the Launcher can use
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* writes of other values to send interrupts or set up receipt of notifications.
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*
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* Note that we overload the "offset" in the /dev/lguest file to indicate what
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* CPU number we're dealing with. Currently this is always 0 since we only
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* support uniprocessor Guests, but you can see the beginnings of SMP support
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* here.
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*/
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static ssize_t write(struct file *file, const char __user *in,
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size_t size, loff_t *off)
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{
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/*
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* Once the Guest is initialized, we hold the "struct lguest" in the
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* file private data.
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*/
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struct lguest *lg = file->private_data;
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const unsigned long __user *input = (const unsigned long __user *)in;
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unsigned long req;
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struct lg_cpu *uninitialized_var(cpu);
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unsigned int cpu_id = *off;
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/* The first value tells us what this request is. */
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if (get_user(req, input) != 0)
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return -EFAULT;
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input++;
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/* If you haven't initialized, you must do that first. */
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if (req != LHREQ_INITIALIZE) {
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if (!lg || (cpu_id >= lg->nr_cpus))
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return -EINVAL;
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cpu = &lg->cpus[cpu_id];
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/* Once the Guest is dead, you can only read() why it died. */
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if (lg->dead)
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return -ENOENT;
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}
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switch (req) {
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case LHREQ_INITIALIZE:
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return initialize(file, input);
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case LHREQ_IRQ:
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return user_send_irq(cpu, input);
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case LHREQ_GETREG:
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return getreg_setup(cpu, input);
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case LHREQ_SETREG:
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return setreg(cpu, input);
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case LHREQ_TRAP:
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return trap(cpu, input);
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default:
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return -EINVAL;
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}
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}
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static int open(struct inode *inode, struct file *file)
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{
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file->private_data = NULL;
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return 0;
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}
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/*L:060
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* The final piece of interface code is the close() routine. It reverses
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* everything done in initialize(). This is usually called because the
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* Launcher exited.
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*
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* Note that the close routine returns 0 or a negative error number: it can't
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* really fail, but it can whine. I blame Sun for this wart, and K&R C for
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* letting them do it.
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:*/
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static int close(struct inode *inode, struct file *file)
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{
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struct lguest *lg = file->private_data;
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unsigned int i;
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/* If we never successfully initialized, there's nothing to clean up */
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if (!lg)
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return 0;
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/*
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* We need the big lock, to protect from inter-guest I/O and other
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* Launchers initializing guests.
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*/
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mutex_lock(&lguest_lock);
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/* Free up the shadow page tables for the Guest. */
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free_guest_pagetable(lg);
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for (i = 0; i < lg->nr_cpus; i++) {
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/* Cancels the hrtimer set via LHCALL_SET_CLOCKEVENT. */
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hrtimer_cancel(&lg->cpus[i].hrt);
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/* We can free up the register page we allocated. */
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free_page(lg->cpus[i].regs_page);
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/*
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* Now all the memory cleanups are done, it's safe to release
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* the Launcher's memory management structure.
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*/
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|
|
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);
|
||
|
|
}
|