371 lines
10 KiB
C
371 lines
10 KiB
C
|
/*P:400
|
||
|
|
* This contains run_guest() which actually calls into the Host<->Guest
|
||
|
|
* Switcher and analyzes the return, such as determining if the Guest wants the
|
||
|
|
* Host to do something. This file also contains useful helper routines.
|
||
|
|
:*/
|
||
|
|
#include <linux/module.h>
|
||
|
|
#include <linux/stringify.h>
|
||
|
|
#include <linux/stddef.h>
|
||
|
|
#include <linux/io.h>
|
||
|
|
#include <linux/mm.h>
|
||
|
|
#include <linux/vmalloc.h>
|
||
|
|
#include <linux/cpu.h>
|
||
|
|
#include <linux/freezer.h>
|
||
|
|
#include <linux/highmem.h>
|
||
|
|
#include <linux/slab.h>
|
||
|
|
#include <asm/paravirt.h>
|
||
|
|
#include <asm/pgtable.h>
|
||
|
|
#include <asm/uaccess.h>
|
||
|
|
#include <asm/poll.h>
|
||
|
|
#include <asm/asm-offsets.h>
|
||
|
|
#include "lg.h"
|
||
|
|
|
||
|
|
unsigned long switcher_addr;
|
||
|
|
struct page **lg_switcher_pages;
|
||
|
|
static struct vm_struct *switcher_vma;
|
||
|
|
|
||
|
|
/* This One Big lock protects all inter-guest data structures. */
|
||
|
|
DEFINE_MUTEX(lguest_lock);
|
||
|
|
|
||
|
|
/*H:010
|
||
|
|
* We need to set up the Switcher at a high virtual address. Remember the
|
||
|
|
* Switcher is a few hundred bytes of assembler code which actually changes the
|
||
|
|
* CPU to run the Guest, and then changes back to the Host when a trap or
|
||
|
|
* interrupt happens.
|
||
|
|
*
|
||
|
|
* The Switcher code must be at the same virtual address in the Guest as the
|
||
|
|
* Host since it will be running as the switchover occurs.
|
||
|
|
*
|
||
|
|
* Trying to map memory at a particular address is an unusual thing to do, so
|
||
|
|
* it's not a simple one-liner.
|
||
|
|
*/
|
||
|
|
static __init int map_switcher(void)
|
||
|
|
{
|
||
|
|
int i, err;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Map the Switcher in to high memory.
|
||
|
|
*
|
||
|
|
* It turns out that if we choose the address 0xFFC00000 (4MB under the
|
||
|
|
* top virtual address), it makes setting up the page tables really
|
||
|
|
* easy.
|
||
|
|
*/
|
||
|
|
|
||
|
|
/* We assume Switcher text fits into a single page. */
|
||
|
|
if (end_switcher_text - start_switcher_text > PAGE_SIZE) {
|
||
|
|
printk(KERN_ERR "lguest: switcher text too large (%zu)\n",
|
||
|
|
end_switcher_text - start_switcher_text);
|
||
|
|
return -EINVAL;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* We allocate an array of struct page pointers. map_vm_area() wants
|
||
|
|
* this, rather than just an array of pages.
|
||
|
|
*/
|
||
|
|
lg_switcher_pages = kmalloc(sizeof(lg_switcher_pages[0])
|
||
|
|
* TOTAL_SWITCHER_PAGES,
|
||
|
|
GFP_KERNEL);
|
||
|
|
if (!lg_switcher_pages) {
|
||
|
|
err = -ENOMEM;
|
||
|
|
goto out;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Now we actually allocate the pages. The Guest will see these pages,
|
||
|
|
* so we make sure they're zeroed.
|
||
|
|
*/
|
||
|
|
for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) {
|
||
|
|
lg_switcher_pages[i] = alloc_page(GFP_KERNEL|__GFP_ZERO);
|
||
|
|
if (!lg_switcher_pages[i]) {
|
||
|
|
err = -ENOMEM;
|
||
|
|
goto free_some_pages;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* We place the Switcher underneath the fixmap area, which is the
|
||
|
|
* highest virtual address we can get. This is important, since we
|
||
|
|
* tell the Guest it can't access this memory, so we want its ceiling
|
||
|
|
* as high as possible.
|
||
|
|
*/
|
||
|
|
switcher_addr = FIXADDR_START - (TOTAL_SWITCHER_PAGES+1)*PAGE_SIZE;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Now we reserve the "virtual memory area" we want. We might
|
||
|
|
* not get it in theory, but in practice it's worked so far.
|
||
|
|
* The end address needs +1 because __get_vm_area allocates an
|
||
|
|
* extra guard page, so we need space for that.
|
||
|
|
*/
|
||
|
|
switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE,
|
||
|
|
VM_ALLOC, switcher_addr, switcher_addr
|
||
|
|
+ (TOTAL_SWITCHER_PAGES+1) * PAGE_SIZE);
|
||
|
|
if (!switcher_vma) {
|
||
|
|
err = -ENOMEM;
|
||
|
|
printk("lguest: could not map switcher pages high\n");
|
||
|
|
goto free_pages;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* This code actually sets up the pages we've allocated to appear at
|
||
|
|
* switcher_addr. map_vm_area() takes the vma we allocated above, the
|
||
|
|
* kind of pages we're mapping (kernel pages), and a pointer to our
|
||
|
|
* array of struct pages.
|
||
|
|
*/
|
||
|
|
err = map_vm_area(switcher_vma, PAGE_KERNEL_EXEC, lg_switcher_pages);
|
||
|
|
if (err) {
|
||
|
|
printk("lguest: map_vm_area failed: %i\n", err);
|
||
|
|
goto free_vma;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Now the Switcher is mapped at the right address, we can't fail!
|
||
|
|
* Copy in the compiled-in Switcher code (from x86/switcher_32.S).
|
||
|
|
*/
|
||
|
|
memcpy(switcher_vma->addr, start_switcher_text,
|
||
|
|
end_switcher_text - start_switcher_text);
|
||
|
|
|
||
|
|
printk(KERN_INFO "lguest: mapped switcher at %p\n",
|
||
|
|
switcher_vma->addr);
|
||
|
|
/* And we succeeded... */
|
||
|
|
return 0;
|
||
|
|
|
||
|
|
free_vma:
|
||
|
|
vunmap(switcher_vma->addr);
|
||
|
|
free_pages:
|
||
|
|
i = TOTAL_SWITCHER_PAGES;
|
||
|
|
free_some_pages:
|
||
|
|
for (--i; i >= 0; i--)
|
||
|
|
__free_pages(lg_switcher_pages[i], 0);
|
||
|
|
kfree(lg_switcher_pages);
|
||
|
|
out:
|
||
|
|
return err;
|
||
|
|
}
|
||
|
|
/*:*/
|
||
|
|
|
||
|
|
/* Cleaning up the mapping when the module is unloaded is almost... too easy. */
|
||
|
|
static void unmap_switcher(void)
|
||
|
|
{
|
||
|
|
unsigned int i;
|
||
|
|
|
||
|
|
/* vunmap() undoes *both* map_vm_area() and __get_vm_area(). */
|
||
|
|
vunmap(switcher_vma->addr);
|
||
|
|
/* Now we just need to free the pages we copied the switcher into */
|
||
|
|
for (i = 0; i < TOTAL_SWITCHER_PAGES; i++)
|
||
|
|
__free_pages(lg_switcher_pages[i], 0);
|
||
|
|
kfree(lg_switcher_pages);
|
||
|
|
}
|
||
|
|
|
||
|
|
/*H:032
|
||
|
|
* Dealing With Guest Memory.
|
||
|
|
*
|
||
|
|
* Before we go too much further into the Host, we need to grok the routines
|
||
|
|
* we use to deal with Guest memory.
|
||
|
|
*
|
||
|
|
* When the Guest gives us (what it thinks is) a physical address, we can use
|
||
|
|
* the normal copy_from_user() & copy_to_user() on the corresponding place in
|
||
|
|
* the memory region allocated by the Launcher.
|
||
|
|
*
|
||
|
|
* But we can't trust the Guest: it might be trying to access the Launcher
|
||
|
|
* code. We have to check that the range is below the pfn_limit the Launcher
|
||
|
|
* gave us. We have to make sure that addr + len doesn't give us a false
|
||
|
|
* positive by overflowing, too.
|
||
|
|
*/
|
||
|
|
bool lguest_address_ok(const struct lguest *lg,
|
||
|
|
unsigned long addr, unsigned long len)
|
||
|
|
{
|
||
|
|
return addr+len <= lg->pfn_limit * PAGE_SIZE && (addr+len >= addr);
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* This routine copies memory from the Guest. Here we can see how useful the
|
||
|
|
* kill_lguest() routine we met in the Launcher can be: we return a random
|
||
|
|
* value (all zeroes) instead of needing to return an error.
|
||
|
|
*/
|
||
|
|
void __lgread(struct lg_cpu *cpu, void *b, unsigned long addr, unsigned bytes)
|
||
|
|
{
|
||
|
|
if (!lguest_address_ok(cpu->lg, addr, bytes)
|
||
|
|
|| copy_from_user(b, cpu->lg->mem_base + addr, bytes) != 0) {
|
||
|
|
/* copy_from_user should do this, but as we rely on it... */
|
||
|
|
memset(b, 0, bytes);
|
||
|
|
kill_guest(cpu, "bad read address %#lx len %u", addr, bytes);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/* This is the write (copy into Guest) version. */
|
||
|
|
void __lgwrite(struct lg_cpu *cpu, unsigned long addr, const void *b,
|
||
|
|
unsigned bytes)
|
||
|
|
{
|
||
|
|
if (!lguest_address_ok(cpu->lg, addr, bytes)
|
||
|
|
|| copy_to_user(cpu->lg->mem_base + addr, b, bytes) != 0)
|
||
|
|
kill_guest(cpu, "bad write address %#lx len %u", addr, bytes);
|
||
|
|
}
|
||
|
|
/*:*/
|
||
|
|
|
||
|
|
/*H:030
|
||
|
|
* Let's jump straight to the the main loop which runs the Guest.
|
||
|
|
* Remember, this is called by the Launcher reading /dev/lguest, and we keep
|
||
|
|
* going around and around until something interesting happens.
|
||
|
|
*/
|
||
|
|
int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
|
||
|
|
{
|
||
|
|
/* We stop running once the Guest is dead. */
|
||
|
|
while (!cpu->lg->dead) {
|
||
|
|
unsigned int irq;
|
||
|
|
bool more;
|
||
|
|
|
||
|
|
/* First we run any hypercalls the Guest wants done. */
|
||
|
|
if (cpu->hcall)
|
||
|
|
do_hypercalls(cpu);
|
||
|
|
|
||
|
|
/*
|
||
|
|
* It's possible the Guest did a NOTIFY hypercall to the
|
||
|
|
* Launcher.
|
||
|
|
*/
|
||
|
|
if (cpu->pending_notify) {
|
||
|
|
/*
|
||
|
|
* Does it just needs to write to a registered
|
||
|
|
* eventfd (ie. the appropriate virtqueue thread)?
|
||
|
|
*/
|
||
|
|
if (!send_notify_to_eventfd(cpu)) {
|
||
|
|
/* OK, we tell the main Launcher. */
|
||
|
|
if (put_user(cpu->pending_notify, user))
|
||
|
|
return -EFAULT;
|
||
|
|
return sizeof(cpu->pending_notify);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* All long-lived kernel loops need to check with this horrible
|
||
|
|
* thing called the freezer. If the Host is trying to suspend,
|
||
|
|
* it stops us.
|
||
|
|
*/
|
||
|
|
try_to_freeze();
|
||
|
|
|
||
|
|
/* Check for signals */
|
||
|
|
if (signal_pending(current))
|
||
|
|
return -ERESTARTSYS;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Check if there are any interrupts which can be delivered now:
|
||
|
|
* if so, this sets up the hander to be executed when we next
|
||
|
|
* run the Guest.
|
||
|
|
*/
|
||
|
|
irq = interrupt_pending(cpu, &more);
|
||
|
|
if (irq < LGUEST_IRQS)
|
||
|
|
try_deliver_interrupt(cpu, irq, more);
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Just make absolutely sure the Guest is still alive. One of
|
||
|
|
* those hypercalls could have been fatal, for example.
|
||
|
|
*/
|
||
|
|
if (cpu->lg->dead)
|
||
|
|
break;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* If the Guest asked to be stopped, we sleep. The Guest's
|
||
|
|
* clock timer will wake us.
|
||
|
|
*/
|
||
|
|
if (cpu->halted) {
|
||
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
||
|
|
/*
|
||
|
|
* Just before we sleep, make sure no interrupt snuck in
|
||
|
|
* which we should be doing.
|
||
|
|
*/
|
||
|
|
if (interrupt_pending(cpu, &more) < LGUEST_IRQS)
|
||
|
|
set_current_state(TASK_RUNNING);
|
||
|
|
else
|
||
|
|
schedule();
|
||
|
|
continue;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* OK, now we're ready to jump into the Guest. First we put up
|
||
|
|
* the "Do Not Disturb" sign:
|
||
|
|
*/
|
||
|
|
local_irq_disable();
|
||
|
|
|
||
|
|
/* Actually run the Guest until something happens. */
|
||
|
|
lguest_arch_run_guest(cpu);
|
||
|
|
|
||
|
|
/* Now we're ready to be interrupted or moved to other CPUs */
|
||
|
|
local_irq_enable();
|
||
|
|
|
||
|
|
/* Now we deal with whatever happened to the Guest. */
|
||
|
|
lguest_arch_handle_trap(cpu);
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Special case: Guest is 'dead' but wants a reboot. */
|
||
|
|
if (cpu->lg->dead == ERR_PTR(-ERESTART))
|
||
|
|
return -ERESTART;
|
||
|
|
|
||
|
|
/* The Guest is dead => "No such file or directory" */
|
||
|
|
return -ENOENT;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*H:000
|
||
|
|
* Welcome to the Host!
|
||
|
|
*
|
||
|
|
* By this point your brain has been tickled by the Guest code and numbed by
|
||
|
|
* the Launcher code; prepare for it to be stretched by the Host code. This is
|
||
|
|
* the heart. Let's begin at the initialization routine for the Host's lg
|
||
|
|
* module.
|
||
|
|
*/
|
||
|
|
static int __init init(void)
|
||
|
|
{
|
||
|
|
int err;
|
||
|
|
|
||
|
|
/* Lguest can't run under Xen, VMI or itself. It does Tricky Stuff. */
|
||
|
|
if (get_kernel_rpl() != 0) {
|
||
|
|
printk("lguest is afraid of being a guest\n");
|
||
|
|
return -EPERM;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* First we put the Switcher up in very high virtual memory. */
|
||
|
|
err = map_switcher();
|
||
|
|
if (err)
|
||
|
|
goto out;
|
||
|
|
|
||
|
|
/* We might need to reserve an interrupt vector. */
|
||
|
|
err = init_interrupts();
|
||
|
|
if (err)
|
||
|
|
goto unmap;
|
||
|
|
|
||
|
|
/* /dev/lguest needs to be registered. */
|
||
|
|
err = lguest_device_init();
|
||
|
|
if (err)
|
||
|
|
goto free_interrupts;
|
||
|
|
|
||
|
|
/* Finally we do some architecture-specific setup. */
|
||
|
|
lguest_arch_host_init();
|
||
|
|
|
||
|
|
/* All good! */
|
||
|
|
return 0;
|
||
|
|
|
||
|
|
free_interrupts:
|
||
|
|
free_interrupts();
|
||
|
|
unmap:
|
||
|
|
unmap_switcher();
|
||
|
|
out:
|
||
|
|
return err;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Cleaning up is just the same code, backwards. With a little French. */
|
||
|
|
static void __exit fini(void)
|
||
|
|
{
|
||
|
|
lguest_device_remove();
|
||
|
|
free_interrupts();
|
||
|
|
unmap_switcher();
|
||
|
|
|
||
|
|
lguest_arch_host_fini();
|
||
|
|
}
|
||
|
|
/*:*/
|
||
|
|
|
||
|
|
/*
|
||
|
|
* The Host side of lguest can be a module. This is a nice way for people to
|
||
|
|
* play with it.
|
||
|
|
*/
|
||
|
|
module_init(init);
|
||
|
|
module_exit(fini);
|
||
|
|
MODULE_LICENSE("GPL");
|
||
|
|
MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
|