/*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, and a
* couple of non-obvious setup and teardown pieces which were implemented after
* days of debugging pain. :*/
#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 <asm/paravirt.h>
#include <asm/desc.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/poll.h>
#include <asm/highmem.h>
#include <asm/asm-offsets.h>
#include <asm/i387.h>
#include "lg.h"
/* Found in switcher.S */
extern char start_switcher_text[], end_switcher_text[], switch_to_guest[];
extern unsigned long default_idt_entries[];
/* Every guest maps the core switcher code. */
#define SHARED_SWITCHER_PAGES \
DIV_ROUND_UP(end_switcher_text - start_switcher_text, PAGE_SIZE)
/* Pages for switcher itself, then two pages per cpu */
#define TOTAL_SWITCHER_PAGES (SHARED_SWITCHER_PAGES + 2 * NR_CPUS)
/* We map at -4M for ease of mapping into the guest (one PTE page). */
#define SWITCHER_ADDR 0xFFC00000
static struct vm_struct *switcher_vma;
static struct page **switcher_page;
static int cpu_had_pge;
static struct {
unsigned long offset;
unsigned short segment;
} lguest_entry;
/* This One Big lock protects all inter-guest data structures. */
DEFINE_MUTEX(lguest_lock);
static DEFINE_PER_CPU(struct lguest *, last_guest);
/* FIXME: Make dynamic. */
#define MAX_LGUEST_GUESTS 16
struct lguest lguests[MAX_LGUEST_GUESTS];
/* Offset from where switcher.S was compiled to where we've copied it */
static unsigned long switcher_offset(void)
{
return SWITCHER_ADDR - (unsigned long)start_switcher_text;
}
/* This cpu's struct lguest_pages. */
static struct lguest_pages *lguest_pages(unsigned int cpu)
{
return &(((struct lguest_pages *)
(SWITCHER_ADDR + SHARED_SWITCHER_PAGES*PAGE_SIZE))[cpu]);
}
static __init int map_switcher(void)
{
int i, err;
struct page **pagep;
switcher_page = kmalloc(sizeof(switcher_page[0])*TOTAL_SWITCHER_PAGES,
GFP_KERNEL);
if (!switcher_page) {
err = -ENOMEM;
goto out;
}
for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) {
unsigned long addr = get_zeroed_page(GFP_KERNEL);
if (!addr) {
err = -ENOMEM;
goto free_some_pages;
}
switcher_page[i] = virt_to_page(addr);
}
switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE,
VM_ALLOC, SWITCHER_ADDR, VMALLOC_END);
if (!switcher_vma) {
err = -ENOMEM;
printk("lguest: could not map switcher pages high\n");
goto free_pages;
}
pagep = switcher_page;
err = map_vm_area(switcher_vma, PAGE_KERNEL, &pagep);
if (err) {
printk("lguest: map_vm_area failed: %i\n", err);
goto free_vma;
}
memcpy(switcher_vma->addr, start_switcher_text,
end_switcher_text - start_switcher_text);
/* Fix up IDT entries to point into copied text. */
for (i = 0; i < IDT_ENTRIES; i++)
default_idt_entries[i] += switcher_offset();
for_each_possible_cpu(i) {
struct lguest_pages *pages = lguest_pages(i);
struct lguest_ro_state *state = &pages->state;
/* These fields are static: rest done in copy_in_guest_info */
state->host_gdt_desc.size = GDT_SIZE-1;
state->host_gdt_desc.address = (long)get_cpu_gdt_table(i);
store_idt(&state->host_idt_desc);
state->guest_idt_desc.size = sizeof(state->guest_idt)-1;
state->guest_idt_desc.address = (long)&state->guest_idt;
state->guest_gdt_desc.size = sizeof(state->guest_gdt)-1;
state->guest_gdt_desc.address = (long)&state->guest_gdt;
state->guest_tss.esp0 = (long)(&pages->regs + 1);
state->guest_tss.ss0 = LGUEST_DS;
/* No I/O for you! */
state->guest_tss.io_bitmap_base = sizeof(state->guest_tss);
setup_default_gdt_entries(state);
setup_default_idt_entries(state, default_idt_entries);
/* Setup LGUEST segments on all cpus */
get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
}
/* Initialize entry point into switcher. */
lguest_entry.offset = (long)switch_to_guest + switcher_offset();
lguest_entry.segment = LGUEST_CS;
printk(KERN_INFO "lguest: mapped switcher at %p\n",
switcher_vma->addr);
return 0;
free_vma:
vunmap(switcher_vma->addr);
free_pages:
i = TOTAL_SWITCHER_PAGES;
free_some_pages:
for (--i; i >= 0; i--)
__free_pages(switcher_page[i], 0);
kfree(switcher_page);
out:
return err;
}
static void unmap_switcher(void)
{
unsigned int i;
vunmap(switcher_vma->addr);
for (i = 0; i < TOTAL_SWITCHER_PAGES; i++)
__free_pages(switcher_page[i], 0);
}
/* IN/OUT insns: enough to get us past boot-time probing. */
static int emulate_insn(struct lguest *lg)
{
u8 insn;
unsigned int insnlen = 0, in = 0, shift = 0;
unsigned long physaddr = guest_pa(lg, lg->regs->eip);
/* This only works for addresses in linear mapping... */
if (lg->regs->eip < lg->page_offset)
return 0;
lgread(lg, &insn, physaddr, 1);
/* Operand size prefix means it's actually for ax. */
if (insn == 0x66) {
shift = 16;
insnlen = 1;
lgread(lg, &insn, physaddr + insnlen, 1);
}
switch (insn & 0xFE) {
case 0xE4: /* in <next byte>,%al */
insnlen += 2;
in = 1;
break;
case 0xEC: /* in (%dx),%al */
insnlen += 1;
in = 1;
break;
case 0xE6: /* out %al,<next byte> */
insnlen += 2;
break;
case 0xEE: /* out %al,(%dx) */
insnlen += 1;
break;
default:
return 0;
}
if (in) {
/* Lower bit tells is whether it's a 16 or 32 bit access */
if (insn & 0x1)
lg->regs->eax = 0xFFFFFFFF;
else
lg->regs->eax |= (0xFFFF << shift);
}
lg->regs->eip += insnlen;
return 1;
}
/*L:305
* Dealing 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 that address: remember,
* Guest physical == Launcher virtual.
*
* 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. */
int lguest_address_ok(const struct lguest *lg,
unsigned long addr, unsigned long len)
{
return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr);
}
/* This is a convenient routine to get a 32-bit value from the Guest (a very
* common operation). Here we can see how useful the kill_lguest() routine we
* met in the Launcher can be: we return a random value (0) instead of needing
* to return an error. */
u32 lgread_u32(struct lguest *lg, unsigned long addr)
{
u32 val = 0;
/* Don't let them access lguest binary. */
if (!lguest_address_ok(lg, addr, sizeof(val))
|| get_user(val, (u32 __user *)addr) != 0)
kill_guest(lg, "bad read address %#lx", addr);
return val;
}
/* Same thing for writing a value. */
void lgwrite_u32(struct lguest *lg, unsigned long addr, u32 val)
{
if (!lguest_address_ok(lg, addr, sizeof(val))
|| put_user(val, (u32 __user *)addr) != 0)
kill_guest(lg, "bad write address %#lx", addr);
}
/* This routine is more generic, and copies a range of Guest bytes into a
* buffer. If the copy_from_user() fails, we fill the buffer with zeroes, so
* the caller doesn't end up using uninitialized kernel memory. */
void lgread(struct lguest *lg, void *b, unsigned long addr, unsigned bytes)
{
if (!lguest_address_ok(lg, addr, bytes)
|| copy_from_user(b, (void __user *)addr, bytes) != 0) {
/* copy_from_user should do this, but as we rely on it... */
memset(b, 0, bytes);
kill_guest(lg, "bad read address %#lx len %u", addr, bytes);
}
}
/* Similarly, our generic routine to copy into a range of Guest bytes. */
void lgwrite(struct lguest *lg, unsigned long addr, const void *b,
unsigned bytes)
{
if (!lguest_address_ok(lg, addr, bytes)
|| copy_to_user((void __user *)addr, b, bytes) != 0)
kill_guest(lg, "bad write address %#lx len %u", addr, bytes);
}
/* (end of memory access helper routines) :*/
static void set_ts(void)
{
u32 cr0;
cr0 = read_cr0();
if (!(cr0 & 8))
write_cr0(cr0|8);
}
static void copy_in_guest_info(struct lguest *lg, struct lguest_pages *pages)
{
if (__get_cpu_var(last_guest) != lg || lg->last_pages != pages) {
__get_cpu_var(last_guest) = lg;
lg->last_pages = pages;
lg->changed = CHANGED_ALL;
}
/* These are pretty cheap, so we do them unconditionally. */
pages->state.host_cr3 = __pa(current->mm->pgd);
map_switcher_in_guest(lg, pages);
pages->state.guest_tss.esp1 = lg->esp1;
pages->state.guest_tss.ss1 = lg->ss1;
/* Copy direct trap entries. */
if (lg->changed & CHANGED_IDT)
copy_traps(lg, pages->state.guest_idt, default_idt_entries);
/* Copy all GDT entries but the TSS. */
if (lg->changed & CHANGED_GDT)
copy_gdt(lg, pages->state.guest_gdt);
/* If only the TLS entries have changed, copy them. */
else if (lg->changed & CHANGED_GDT_TLS)
copy_gdt_tls(lg, pages->state.guest_gdt);
lg->changed = 0;
}
static void run_guest_once(struct lguest *lg, struct lguest_pages *pages)
{
unsigned int clobber;
copy_in_guest_info(lg, pages);
/* Put eflags on stack, lcall does rest: suitable for iret return. */
asm volatile("pushf; lcall *lguest_entry"
: "=a"(clobber), "=b"(clobber)
: "0"(pages), "1"(__pa(lg->pgdirs[lg->pgdidx].pgdir))
: "memory", "%edx", "%ecx", "%edi", "%esi");
}
int run_guest(struct lguest *lg, unsigned long __user *user)
{
while (!lg->dead) {
unsigned int cr2 = 0; /* Damn gcc */
/* Hypercalls first: we might have been out to userspace */
do_hypercalls(lg);
if (lg->dma_is_pending) {
if (put_user(lg->pending_dma, user) ||
put_user(lg->pending_key, user+1))
return -EFAULT;
return sizeof(unsigned long)*2;
}
if (signal_pending(current))
return -ERESTARTSYS;
/* If Waker set break_out, return to Launcher. */
if (lg->break_out)
return -EAGAIN;
maybe_do_interrupt(lg);
try_to_freeze();
if (lg->dead)
break;
if (lg->halted) {
set_current_state(TASK_INTERRUPTIBLE);
schedule();
continue;
}
local_irq_disable();
/* Even if *we* don't want FPU trap, guest might... */
if (lg->ts)
set_ts();
/* Don't let Guest do SYSENTER: we can't handle it. */
if (boot_cpu_has(X86_FEATURE_SEP))
wrmsr(MSR_IA32_SYSENTER_CS, 0, 0);
run_guest_once(lg, lguest_pages(raw_smp_processor_id()));
/* Save cr2 now if we page-faulted. */
if (lg->regs->trapnum == 14)
cr2 = read_cr2();
else if (lg->regs->trapnum == 7)
math_state_restore();
if (boot_cpu_has(X86_FEATURE_SEP))
wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
local_irq_enable();
switch (lg->regs->trapnum) {
case 13: /* We've intercepted a GPF. */
if (lg->regs->errcode == 0) {
if (emulate_insn(lg))
continue;
}
break;
case 14: /* We've intercepted a page fault. */
if (demand_page(lg, cr2, lg->regs->errcode))
continue;
/* If lguest_data is NULL, this won't hurt. */
if (put_user(cr2, &lg->lguest_data->cr2))
kill_guest(lg, "Writing cr2");
break;
case 7: /* We've intercepted a Device Not Available fault. */
/* If they don't want to know, just absorb it. */
if (!lg->ts)
continue;
break;
case 32 ... 255: /* Real interrupt, fall thru */
cond_resched();
case LGUEST_TRAP_ENTRY: /* Handled at top of loop */
continue;
}
if (deliver_trap(lg, lg->regs->trapnum))
continue;
kill_guest(lg, "unhandled trap %li at %#lx (%#lx)",
lg->regs->trapnum, lg->regs->eip,
lg->regs->trapnum == 14 ? cr2 : lg->regs->errcode);
}
return -ENOENT;
}
int find_free_guest(void)
{
unsigned int i;
for (i = 0; i < MAX_LGUEST_GUESTS; i++)
if (!lguests[i].tsk)
return i;
return -1;
}
static void adjust_pge(void *on)
{
if (on)
write_cr4(read_cr4() | X86_CR4_PGE);
else
write_cr4(read_cr4() & ~X86_CR4_PGE);
}
static int __init init(void)
{
int err;
if (paravirt_enabled()) {
printk("lguest is afraid of %s\n", paravirt_ops.name);
return -EPERM;
}
err = map_switcher();
if (err)
return err;
err = init_pagetables(switcher_page, SHARED_SWITCHER_PAGES);
if (err) {
unmap_switcher();
return err;
}
lguest_io_init();
err = lguest_device_init();
if (err) {
free_pagetables();
unmap_switcher();
return err;
}
lock_cpu_hotplug();
if (cpu_has_pge) { /* We have a broader idea of "global". */
cpu_had_pge = 1;
on_each_cpu(adjust_pge, (void *)0, 0, 1);
clear_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
}
unlock_cpu_hotplug();
return 0;
}
static void __exit fini(void)
{
lguest_device_remove();
free_pagetables();
unmap_switcher();
lock_cpu_hotplug();
if (cpu_had_pge) {
set_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
on_each_cpu(adjust_pge, (void *)1, 0, 1);
}
unlock_cpu_hotplug();
}
module_init(init);
module_exit(fini);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
