mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-27 11:19:37 +00:00
![Martin Kepplinger](/assets/img/avatar_default.png)
There is a proposed change to the miscdevice's behaviour on open(). Currently
file->private_data stays NULL, but only because we don't have an open-entry in
struct file_operations.
This may change so that private_data, more consistently, is always set to
struct miscdevice, not only *if* the driver has it's own open() routine and
fops-entry, see https://lkml.org/lkml/2014/12/4/939 and commit
94e4fe2cab
In short: If we rely on file->private_data being NULL, we should ensure
it is NULL ourselves.
Signed-off-by: Martin Kepplinger <martink@posteo.de>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
445 lines
12 KiB
C
445 lines
12 KiB
C
/*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);
|
|
}
|