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    Subject[PATCH 2/8] lguest: the host code (lg.ko).
    From
    Date
    This is the host module (lg.ko) which supports lguest:

    arch/i386/lguest/hypervisor.S:
    The actual guest <-> host switching code. This is compiled into
    a C array, which is mapped to 0xFFC01000 in host and guests.

    arch/i386/lguest/core.c:
    The core of the hypervisor, which calls into the assembler
    code which does this actual switch. Also contains helper
    routines.

    arch/i386/lguest/hypercalls.c:
    The entry point for the 19 hypercalls.

    arch/i386/lguest/interrupts_and_traps.c:
    Handling of interrupts and traps, except page faults.

    arch/i386/lguest/io.c:
    I/O from guest to host, and between guests.

    arch/i386/lguest/lguest_user.c:
    /dev/lguest interface for lguest program to launch/control guests.

    arch/i386/lguest/page_tables.c:
    Shadow Page table handling: generally we build up the shadow
    page tables by converting from guest page tables when a fault occurs.

    arch/i386/lguest/segments.c:
    Segmentation (GDT) handling: we have to ensure they're trimmed
    to avoid guest access to the switching code.

    Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
    * * *

    diff -r a31396449b82 arch/i386/lguest/core.c
    --- /dev/null Thu Jan 01 00:00:00 1970 +0000
    +++ b/arch/i386/lguest/core.c Mon Feb 12 12:59:41 2007 +1100
    @@ -0,0 +1,432 @@
    +/* World's simplest hypervisor, to test paravirt_ops and show
    + * unbelievers that virtualization is the future. Plus, it's fun! */
    +#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/lguest.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"
    +
    +/* This is our hypervisor, compiled from hypervisor.S. */
    +static char __initdata hypervisor_blob[] = {
    +#include "hypervisor-blob.c"
    +};
    +
    +#define MAX_LGUEST_GUESTS \
    + (((PAGE_SIZE << HYPERVISOR_PAGE_ORDER) - sizeof(hypervisor_blob)) \
    + / sizeof(struct lguest_state))
    +
    +static struct vm_struct *hypervisor_vma;
    +static int cpu_had_pge;
    +static struct {
    + unsigned long offset;
    + unsigned short segment;
    +} lguest_entry __attribute_used__;
    +struct page *hype_pages; /* Contiguous pages. */
    +struct lguest lguests[MAX_LGUEST_GUESTS];
    +DEFINE_MUTEX(lguest_lock);
    +
    +/* IDT entries are at start of hypervisor. */
    +const unsigned long *__lguest_default_idt_entries(void)
    +{
    + return (void *)HYPE_ADDR;
    +}
    +
    +/* Next is switch_to_guest */
    +static void *__lguest_switch_to_guest(void)
    +{
    + return (void *)HYPE_ADDR + HYPE_DATA_SIZE;
    +}
    +
    +/* Then we use everything else to hold guest state. */
    +struct lguest_state *__lguest_states(void)
    +{
    + return (void *)HYPE_ADDR + sizeof(hypervisor_blob);
    +}
    +
    +static __init int map_hypervisor(void)
    +{
    + unsigned int i;
    + int err;
    + struct page *pages[HYPERVISOR_PAGES], **pagep = pages;
    +
    + hype_pages = alloc_pages(GFP_KERNEL|__GFP_ZERO, HYPERVISOR_PAGE_ORDER);
    + if (!hype_pages)
    + return -ENOMEM;
    +
    + hypervisor_vma = __get_vm_area(PAGE_SIZE << HYPERVISOR_PAGE_ORDER,
    + VM_ALLOC, HYPE_ADDR, VMALLOC_END);
    + if (!hypervisor_vma) {
    + err = -ENOMEM;
    + printk("lguest: could not map hypervisor pages high\n");
    + goto free_pages;
    + }
    +
    + for (i = 0; i < HYPERVISOR_PAGES; i++)
    + pages[i] = hype_pages + i;
    +
    + err = map_vm_area(hypervisor_vma, PAGE_KERNEL, &pagep);
    + if (err) {
    + printk("lguest: map_vm_area failed: %i\n", err);
    + goto free_vma;
    + }
    + memcpy(hypervisor_vma->addr, hypervisor_blob, sizeof(hypervisor_blob));
    +
    + /* Setup LGUEST segments on all cpus */
    + for_each_possible_cpu(i) {
    + 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 hypervisor. */
    + lguest_entry.offset = (long)__lguest_switch_to_guest();
    + lguest_entry.segment = LGUEST_CS;
    +
    + printk("lguest: mapped hypervisor at %p\n", hypervisor_vma->addr);
    + return 0;
    +
    +free_vma:
    + vunmap(hypervisor_vma->addr);
    +free_pages:
    + __free_pages(hype_pages, HYPERVISOR_PAGE_ORDER);
    + return err;
    +}
    +
    +static __exit void unmap_hypervisor(void)
    +{
    + vunmap(hypervisor_vma->addr);
    + __free_pages(hype_pages, HYPERVISOR_PAGE_ORDER);
    +}
    +
    +/* 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->state->regs.eip);
    +
    + /* This only works for addresses in linear mapping... */
    + if (lg->state->regs.eip < lg->page_offset)
    + return 0;
    + lhread(lg, &insn, physaddr, 1);
    +
    + /* Operand size prefix means it's actually for ax. */
    + if (insn == 0x66) {
    + shift = 16;
    + insnlen = 1;
    + lhread(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->state->regs.eax = 0xFFFFFFFF;
    + else
    + lg->state->regs.eax |= (0xFFFF << shift);
    + }
    + lg->state->regs.eip += insnlen;
    + return 1;
    +}
    +
    +int find_free_guest(void)
    +{
    + unsigned int i;
    + for (i = 0; i < MAX_LGUEST_GUESTS; i++)
    + if (!lguests[i].state)
    + return i;
    + return -1;
    +}
    +
    +int lguest_address_ok(const struct lguest *lg, unsigned long addr)
    +{
    + return addr / PAGE_SIZE < lg->pfn_limit;
    +}
    +
    +/* Just like get_user, but don't let guest access lguest binary. */
    +u32 lhread_u32(struct lguest *lg, u32 addr)
    +{
    + u32 val = 0;
    +
    + /* Don't let them access lguest_add */
    + if (!lguest_address_ok(lg, addr)
    + || get_user(val, (u32 __user *)addr) != 0)
    + kill_guest(lg, "bad read address %u", addr);
    + return val;
    +}
    +
    +void lhwrite_u32(struct lguest *lg, u32 addr, u32 val)
    +{
    + if (!lguest_address_ok(lg, addr)
    + || put_user(val, (u32 __user *)addr) != 0)
    + kill_guest(lg, "bad write address %u", addr);
    +}
    +
    +void lhread(struct lguest *lg, void *b, u32 addr, unsigned bytes)
    +{
    + if (addr + bytes < addr || !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 %u len %u", addr, bytes);
    + }
    +}
    +
    +void lhwrite(struct lguest *lg, u32 addr, const void *b, unsigned bytes)
    +{
    + if (addr + bytes < addr
    + || !lguest_address_ok(lg, addr+bytes)
    + || copy_to_user((void __user *)addr, b, bytes) != 0)
    + kill_guest(lg, "bad write address %u len %u", addr, bytes);
    +}
    +
    +/* Saves exporting idt_table from kernel */
    +static struct desc_struct *get_idt_table(void)
    +{
    + struct Xgt_desc_struct idt;
    +
    + asm("sidt %0":"=m" (idt));
    + return (void *)idt.address;
    +}
    +
    +static int usermode(struct lguest_regs *regs)
    +{
    + return (regs->cs & SEGMENT_RPL_MASK) == USER_RPL;
    +}
    +
    +/* Trap page resets this when it reloads gs. */
    +static int new_gfp_eip(struct lguest *lg, struct lguest_regs *regs)
    +{
    + u32 eip;
    + get_user(eip, &lg->lguest_data->gs_gpf_eip);
    + if (eip == regs->eip)
    + return 0;
    + put_user(regs->eip, &lg->lguest_data->gs_gpf_eip);
    + return 1;
    +}
    +
    +static void set_ts(unsigned int guest_ts)
    +{
    + u32 cr0;
    + if (guest_ts) {
    + asm("movl %%cr0,%0":"=r" (cr0));
    + if (!(cr0 & 8))
    + asm("movl %0,%%cr0": :"r" (cr0|8));
    + }
    +}
    +
    +static void run_guest_once(struct lguest *lg)
    +{
    + unsigned int clobber;
    +
    + /* Put eflags on stack, lcall does rest. */
    + asm volatile("pushf; lcall *lguest_entry"
    + : "=a"(clobber), "=d"(clobber)
    + : "0"(lg->state), "1"(get_idt_table())
    + : "memory");
    +}
    +
    +int run_guest(struct lguest *lg, char *__user user)
    +{
    + struct lguest_regs *regs = &lg->state->regs;
    +
    + while (!lg->dead) {
    + unsigned int cr2 = 0; /* Damn gcc */
    +
    + /* Hypercalls first: we might have been out to userspace */
    + if (do_async_hcalls(lg))
    + goto pending_dma;
    +
    + if (regs->trapnum == LGUEST_TRAP_ENTRY) {
    + /* Only do hypercall once. */
    + regs->trapnum = 255;
    + if (hypercall(lg, regs))
    + goto pending_dma;
    + }
    +
    + if (signal_pending(current))
    + return -EINTR;
    + maybe_do_interrupt(lg);
    +
    + try_to_freeze();
    +
    + if (lg->dead)
    + break;
    +
    + if (lg->halted) {
    + set_current_state(TASK_INTERRUPTIBLE);
    + schedule_timeout(1);
    + continue;
    + }
    +
    + /* Restore limits on TLS segments if in user mode. */
    + if (usermode(regs)) {
    + unsigned int i;
    + for (i = 0; i < ARRAY_SIZE(lg->tls_limits); i++)
    + lg->state->gdt_table[GDT_ENTRY_TLS_MIN+i].a
    + |= lg->tls_limits[i];
    + }
    +
    + local_irq_disable();
    + map_trap_page(lg);
    +
    + /* Host state to be restored after the guest returns. */
    + asm("sidt %0":"=m"(lg->state->host.idt));
    + lg->state->host.gdt = __get_cpu_var(cpu_gdt_descr);
    +
    + /* Even if *we* don't want FPU trap, guest might... */
    + set_ts(lg->ts);
    +
    + run_guest_once(lg);
    +
    + /* Save cr2 now if we page-faulted. */
    + if (regs->trapnum == 14)
    + asm("movl %%cr2,%0" :"=r" (cr2));
    + else if (regs->trapnum == 7)
    + math_state_restore();
    + local_irq_enable();
    +
    + switch (regs->trapnum) {
    + case 13: /* We've intercepted a GPF. */
    + if (regs->errcode == 0) {
    + if (emulate_insn(lg))
    + continue;
    +
    + /* FIXME: If it's reloading %gs in a loop? */
    + if (usermode(regs) && new_gfp_eip(lg,regs))
    + continue;
    + }
    +
    + if (reflect_trap(lg, &lg->gpf_trap, 1))
    + continue;
    + break;
    + case 14: /* We've intercepted a page fault. */
    + if (demand_page(lg, cr2, regs->errcode & 2))
    + continue;
    +
    + /* If lguest_data is NULL, this won't hurt. */
    + put_user(cr2, &lg->lguest_data->cr2);
    + if (reflect_trap(lg, &lg->page_trap, 1))
    + continue;
    + kill_guest(lg, "unhandled page fault at %#x"
    + " (eip=%#x, errcode=%#x)",
    + cr2, regs->eip, regs->errcode);
    + 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;
    + if (reflect_trap(lg, &lg->fpu_trap, 0))
    + continue;
    + kill_guest(lg, "unhandled FPU fault at %#x",
    + regs->eip);
    + break;
    + case 32 ... 255: /* Real interrupt, fall thru */
    + cond_resched();
    + case LGUEST_TRAP_ENTRY: /* Handled at top of loop */
    + continue;
    + case 6: /* Invalid opcode before they installed handler */
    + check_bug_kill(lg);
    + }
    + kill_guest(lg,"unhandled trap %i at %#x (err=%i)",
    + regs->trapnum, regs->eip, regs->errcode);
    + }
    + return -ENOENT;
    +
    +pending_dma:
    + put_user(lg->pending_dma, (unsigned long *)user);
    + put_user(lg->pending_addr, (unsigned long *)user+1);
    + return sizeof(unsigned long)*2;
    +}
    +
    +#define STRUCT_LGUEST_ELEM_SIZE(elem) sizeof(((struct lguest_state *)0)->elem)
    +
    +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())
    + return -EPERM;
    +
    + err = map_hypervisor();
    + if (err)
    + return err;
    +
    + err = init_pagetables(hype_pages);
    + if (err) {
    + unmap_hypervisor();
    + return err;
    + }
    + lguest_io_init();
    +
    + err = lguest_device_init();
    + if (err) {
    + free_pagetables();
    + unmap_hypervisor();
    + 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, 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_hypervisor();
    + 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>");
    diff -r a31396449b82 arch/i386/lguest/hypercalls.c
    --- /dev/null Thu Jan 01 00:00:00 1970 +0000
    +++ b/arch/i386/lguest/hypercalls.c Mon Feb 12 13:00:04 2007 +1100
    @@ -0,0 +1,186 @@
    +/* Actual hypercalls, which allow guests to actually do something.
    + Copyright (C) 2006 Rusty Russell IBM Corporation
    +
    + This program is free software; you can redistribute it and/or modify
    + it under the terms of the GNU General Public License as published by
    + the Free Software Foundation; either version 2 of the License, or
    + (at your option) any later version.
    +
    + This program is distributed in the hope that it will be useful,
    + but WITHOUT ANY WARRANTY; without even the implied warranty of
    + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    + GNU General Public License for more details.
    +
    + You should have received a copy of the GNU General Public License
    + along with this program; if not, write to the Free Software
    + Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
    +*/
    +#include <linux/uaccess.h>
    +#include <linux/syscalls.h>
    +#include <linux/mm.h>
    +#include <asm/lguest.h>
    +#include <asm/page.h>
    +#include <asm/pgtable.h>
    +#include <irq_vectors.h>
    +#include "lg.h"
    +
    +static void guest_set_stack(struct lguest *lg,
    + u32 seg, u32 esp, unsigned int pages)
    +{
    + /* You cannot have a stack segment with priv level 0. */
    + if ((seg & 0x3) != GUEST_DPL)
    + kill_guest(lg, "bad stack segment %i", seg);
    + if (pages > 2)
    + kill_guest(lg, "bad stack pages %u", pages);
    + lg->state->tss.ss1 = seg;
    + lg->state->tss.esp1 = esp;
    + lg->stack_pages = pages;
    + pin_stack_pages(lg);
    +}
    +
    +/* Return true if DMA to host userspace now pending. */
    +static int do_hcall(struct lguest *lg, struct lguest_regs *regs)
    +{
    + switch (regs->eax) {
    + case LHCALL_FLUSH_ASYNC:
    + break;
    + case LHCALL_LGUEST_INIT:
    + kill_guest(lg, "already have lguest_data");
    + break;
    + case LHCALL_CRASH: {
    + char msg[128];
    + lhread(lg, msg, regs->edx, sizeof(msg));
    + msg[sizeof(msg)-1] = '\0';
    + kill_guest(lg, "CRASH: %s", msg);
    + break;
    + }
    + case LHCALL_LOAD_GDT:
    + load_guest_gdt(lg, regs->edx, regs->ebx);
    + break;
    + case LHCALL_NEW_PGTABLE:
    + guest_new_pagetable(lg, regs->edx);
    + break;
    + case LHCALL_FLUSH_TLB:
    + if (regs->edx)
    + guest_pagetable_clear_all(lg);
    + else
    + guest_pagetable_flush_user(lg);
    + break;
    + case LHCALL_LOAD_IDT_ENTRY:
    + load_guest_idt_entry(lg, regs->edx, regs->ebx, regs->ecx);
    + break;
    + case LHCALL_SET_STACK:
    + guest_set_stack(lg, regs->edx, regs->ebx, regs->ecx);
    + break;
    + case LHCALL_TS:
    + lg->ts = regs->edx;
    + break;
    + case LHCALL_TIMER_READ: {
    + u32 now = jiffies;
    + mb();
    + regs->eax = now - lg->last_timer;
    + lg->last_timer = now;
    + break;
    + }
    + case LHCALL_TIMER_START:
    + lg->timer_on = 1;
    + if (regs->edx != HZ)
    + kill_guest(lg, "Bad clock speed %i", regs->edx);
    + lg->last_timer = jiffies;
    + break;
    + case LHCALL_HALT:
    + lg->halted = 1;
    + break;
    + case LHCALL_GET_WALLCLOCK: {
    + struct timeval tv;
    + do_gettimeofday(&tv);
    + regs->eax = tv.tv_sec;
    + break;
    + }
    + case LHCALL_BIND_DMA:
    + regs->eax = bind_dma(lg, regs->edx, regs->ebx,
    + regs->ecx >> 8, regs->ecx & 0xFF);
    + break;
    + case LHCALL_SEND_DMA:
    + return send_dma(lg, regs->edx, regs->ebx);
    + case LHCALL_SET_PTE:
    + guest_set_pte(lg, regs->edx, regs->ebx, regs->ecx);
    + break;
    + case LHCALL_SET_UNKNOWN_PTE:
    + guest_pagetable_clear_all(lg);
    + break;
    + case LHCALL_SET_PUD:
    + guest_set_pud(lg, regs->edx, regs->ebx);
    + break;
    + case LHCALL_LOAD_TLS:
    + guest_load_tls(lg, (struct desc_struct __user*)regs->edx);
    + break;
    + default:
    + kill_guest(lg, "Bad hypercall %i\n", regs->eax);
    + }
    + return 0;
    +}
    +
    +/* We always do queued calls before actual hypercall. */
    +int do_async_hcalls(struct lguest *lg)
    +{
    + unsigned int i, pending;
    + u8 st[LHCALL_RING_SIZE];
    +
    + if (!lg->lguest_data)
    + return 0;
    +
    + copy_from_user(&st, &lg->lguest_data->hcall_status, sizeof(st));
    + for (i = 0; i < ARRAY_SIZE(st); i++) {
    + struct lguest_regs regs;
    + unsigned int n = lg->next_hcall;
    +
    + if (st[n] == 0xFF)
    + break;
    +
    + if (++lg->next_hcall == LHCALL_RING_SIZE)
    + lg->next_hcall = 0;
    +
    + get_user(regs.eax, &lg->lguest_data->hcalls[n].eax);
    + get_user(regs.edx, &lg->lguest_data->hcalls[n].edx);
    + get_user(regs.ecx, &lg->lguest_data->hcalls[n].ecx);
    + get_user(regs.ebx, &lg->lguest_data->hcalls[n].ebx);
    + pending = do_hcall(lg, &regs);
    + put_user(0xFF, &lg->lguest_data->hcall_status[n]);
    + if (pending)
    + return 1;
    + }
    +
    + set_wakeup_process(lg, NULL);
    + return 0;
    +}
    +
    +int hypercall(struct lguest *lg, struct lguest_regs *regs)
    +{
    + int pending;
    +
    + if (!lg->lguest_data) {
    + if (regs->eax != LHCALL_LGUEST_INIT) {
    + kill_guest(lg, "hypercall %i before LGUEST_INIT",
    + regs->eax);
    + return 0;
    + }
    +
    + lg->lguest_data = (struct lguest_data __user *)regs->edx;
    + /* We check here so we can simply copy_to_user/from_user */
    + if (!lguest_address_ok(lg, (long)lg->lguest_data)
    + || !lguest_address_ok(lg, (long)(lg->lguest_data+1))){
    + kill_guest(lg, "bad guest page %p", lg->lguest_data);
    + return 0;
    + }
    + get_user(lg->noirq_start, &lg->lguest_data->noirq_start);
    + get_user(lg->noirq_end, &lg->lguest_data->noirq_end);
    + /* We reserve the top pgd entry. */
    + put_user(4U*1024*1024, &lg->lguest_data->reserve_mem);
    + put_user(lg->guestid, &lg->lguest_data->guestid);
    + return 0;
    + }
    + pending = do_hcall(lg, regs);
    + set_wakeup_process(lg, NULL);
    + return pending;
    +}
    diff -r a31396449b82 arch/i386/lguest/hypervisor.S
    --- /dev/null Thu Jan 01 00:00:00 1970 +0000
    +++ b/arch/i386/lguest/hypervisor.S Mon Feb 12 12:59:41 2007 +1100
    @@ -0,0 +1,170 @@
    +/* This code sits at 0xFFFF1000 to do the low-level guest<->host switch.
    + Layout is: default_idt_entries (1k), then switch_to_guest entry point. */
    +#include <linux/linkage.h>
    +#include <asm/asm-offsets.h>
    +#include "lg.h"
    +
    +#define SAVE_REGS \
    + /* Save old guest/host state */ \
    + pushl %es; \
    + pushl %ds; \
    + pushl %fs; \
    + pushl %eax; \
    + pushl %gs; \
    + pushl %ebp; \
    + pushl %edi; \
    + pushl %esi; \
    + pushl %edx; \
    + pushl %ecx; \
    + pushl %ebx; \
    +
    +.text
    +ENTRY(_start) /* ld complains unless _start is defined. */
    +/* %eax contains ptr to target guest state, %edx contains host idt. */
    +switch_to_guest:
    + pushl %ss
    + SAVE_REGS
    + /* Save old stack, switch to guest's stack. */
    + movl %esp, LGUEST_STATE_host_stackptr(%eax)
    + movl %eax, %esp
    + /* Guest registers will be at: %esp-$LGUEST_STATE_regs */
    + addl $LGUEST_STATE_regs, %esp
    + /* Switch to guest's GDT, IDT. */
    + lgdt LGUEST_STATE_gdt(%eax)
    + lidt LGUEST_STATE_idt(%eax)
    + /* Save page table top. */
    + movl %cr3, %ebx
    + movl %ebx, LGUEST_STATE_host_pgdir(%eax)
    + /* Set host's TSS to available (clear byte 5 bit 2). */
    + movl (LGUEST_STATE_host_gdt+2)(%eax), %ebx
    + andb $0xFD, (GDT_ENTRY_TSS*8 + 5)(%ebx)
    + /* Switch to guest page tables */
    + popl %ebx
    + movl %ebx, %cr3
    + /* Switch to guest's TSS. */
    + movl $(GDT_ENTRY_TSS*8), %ebx
    + ltr %bx
    + /* Restore guest regs */
    + popl %ebx
    + popl %ecx
    + popl %edx
    + popl %esi
    + popl %edi
    + popl %ebp
    + popl %gs
    + /* Now we've loaded gs, neuter the TLS entries down to 1 byte/page */
    + addl $(LGUEST_STATE_gdt_table+GDT_ENTRY_TLS_MIN*8), %eax
    + movw $0,(%eax)
    + movw $0,8(%eax)
    + movw $0,16(%eax)
    + popl %eax
    + popl %fs
    + popl %ds
    + popl %es
    + /* Skip error code and trap number */
    + addl $8, %esp
    + iret
    +
    +#define SWITCH_TO_HOST \
    + SAVE_REGS; \
    + /* Save old pgdir */ \
    + movl %cr3, %eax; \
    + pushl %eax; \
    + /* Load lguest ds segment for convenience. */ \
    + movl $(LGUEST_DS), %eax; \
    + movl %eax, %ds; \
    + /* Now figure out who we are */ \
    + movl %esp, %eax; \
    + subl $LGUEST_STATE_regs, %eax; \
    + /* Switch to host page tables (GDT, IDT and stack are in host \
    + mem, so need this first) */ \
    + movl LGUEST_STATE_host_pgdir(%eax), %ebx; \
    + movl %ebx, %cr3; \
    + /* Set guest's TSS to available (clear byte 5 bit 2). */ \
    + andb $0xFD, (LGUEST_STATE_gdt_table+GDT_ENTRY_TSS*8+5)(%eax);\
    + /* Switch to host's GDT & IDT. */ \
    + lgdt LGUEST_STATE_host_gdt(%eax); \
    + lidt LGUEST_STATE_host_idt(%eax); \
    + /* Switch to host's stack. */ \
    + movl LGUEST_STATE_host_stackptr(%eax), %esp; \
    + /* Switch to host's TSS */ \
    + movl $(GDT_ENTRY_TSS*8), %eax; \
    + ltr %ax; \
    + /* Restore host regs */ \
    + popl %ebx; \
    + popl %ecx; \
    + popl %edx; \
    + popl %esi; \
    + popl %edi; \
    + popl %ebp; \
    + popl %gs; \
    + popl %eax; \
    + popl %fs; \
    + popl %ds; \
    + popl %es; \
    + popl %ss
    +
    +/* Return to run_guest_once. */
    +return_to_host:
    + SWITCH_TO_HOST
    + iret
    +
    +deliver_to_host:
    + SWITCH_TO_HOST
    +decode_idt_and_jmp:
    + /* Decode IDT and jump to hosts' irq handler. When that does iret, it
    + * will return to run_guest_once. This is a feature. */
    + /* We told gcc we'd clobber edx and eax... */
    + movl LGUEST_STATE_trapnum(%eax), %eax
    + leal (%edx,%eax,8), %eax
    + movzwl (%eax),%edx
    + movl 4(%eax), %eax
    + xorw %ax, %ax
    + orl %eax, %edx
    + jmp *%edx
    +
    +deliver_to_host_with_errcode:
    + SWITCH_TO_HOST
    + pushl LGUEST_STATE_errcode(%eax)
    + jmp decode_idt_and_jmp
    +
    +/* Real hardware interrupts are delivered straight to the host. Others
    + cause us to return to run_guest_once so it can decide what to do. Note
    + that some of these are overridden by the guest to deliver directly, and
    + never enter here (see load_guest_idt_entry). */
    +.macro IRQ_STUB N TARGET
    + .data; .long 1f; .text; 1:
    + /* Make an error number for most traps, which don't have one. */
    + .if (\N <> 2) && (\N <> 8) && (\N < 10 || \N > 14) && (\N <> 17)
    + pushl $0
    + .endif
    + pushl $\N
    + jmp \TARGET
    + ALIGN
    +.endm
    +
    +.macro IRQ_STUBS FIRST LAST TARGET
    + irq=\FIRST
    + .rept \LAST-\FIRST+1
    + IRQ_STUB irq \TARGET
    + irq=irq+1
    + .endr
    +.endm
    +
    +/* We intercept every interrupt, because we may need to switch back to
    + * host. Unfortunately we can't tell them apart except by entry
    + * point, so we need 256 entry points.
    + */
    +irq_stubs:
    +.data
    +default_idt_entries:
    +.text
    + IRQ_STUBS 0 1 return_to_host /* First two traps */
    + IRQ_STUB 2 deliver_to_host_with_errcode /* NMI */
    + IRQ_STUBS 3 31 return_to_host /* Rest of traps */
    + IRQ_STUBS 32 127 deliver_to_host /* Real interrupts */
    + IRQ_STUB 128 return_to_host /* System call (overridden) */
    + IRQ_STUBS 129 255 deliver_to_host /* Other real interrupts */
    +
    +/* Everything after this is used for the lguest_state structs. */
    +ALIGN
    diff -r a31396449b82 arch/i386/lguest/interrupts_and_traps.c
    --- /dev/null Thu Jan 01 00:00:00 1970 +0000
    +++ b/arch/i386/lguest/interrupts_and_traps.c Mon Feb 12 12:59:41 2007 +1100
    @@ -0,0 +1,230 @@
    +#include <linux/uaccess.h>
    +#include "lg.h"
    +
    +static void push_guest_stack(struct lguest *lg, u32 __user **gstack, u32 val)
    +{
    + lhwrite_u32(lg, (u32)--(*gstack), val);
    +}
    +
    +int reflect_trap(struct lguest *lg, const struct host_trap *trap, int has_err)
    +{
    + u32 __user *gstack;
    + u32 eflags, ss, irq_enable;
    + struct lguest_regs *regs = &lg->state->regs;
    +
    + if (!trap->addr)
    + return 0;
    +
    + /* If they want a ring change, we use new stack and push old ss/esp */
    + if ((regs->ss&0x3) != GUEST_DPL) {
    + gstack = (u32 __user *)guest_pa(lg, lg->state->tss.esp1);
    + ss = lg->state->tss.ss1;
    + push_guest_stack(lg, &gstack, regs->ss);
    + push_guest_stack(lg, &gstack, regs->esp);
    + } else {
    + gstack = (u32 __user *)guest_pa(lg, regs->esp);
    + ss = regs->ss;
    + }
    +
    + /* We use IF bit in eflags to indicate whether irqs were disabled
    + (it's always 0, since irqs are enabled when guest is running). */
    + eflags = regs->eflags;
    + get_user(irq_enable, &lg->lguest_data->irq_enabled);
    + eflags |= (irq_enable & 512);
    +
    + push_guest_stack(lg, &gstack, eflags);
    + push_guest_stack(lg, &gstack, regs->cs);
    + push_guest_stack(lg, &gstack, regs->eip);
    +
    + if (has_err)
    + push_guest_stack(lg, &gstack, regs->errcode);
    +
    + /* Change the real stack so hypervisor returns to trap handler */
    + regs->ss = ss;
    + regs->esp = (u32)gstack + lg->page_offset;
    + regs->cs = (__KERNEL_CS|GUEST_DPL);
    + regs->eip = trap->addr;
    +
    + /* GS will be neutered on way back to guest. */
    + put_user(0, &lg->lguest_data->gs_gpf_eip);
    +
    + /* Disable interrupts for an interrupt gate. */
    + if (trap->disable_interrupts)
    + put_user(0, &lg->lguest_data->irq_enabled);
    + return 1;
    +}
    +
    +void maybe_do_interrupt(struct lguest *lg)
    +{
    + unsigned int irq;
    + DECLARE_BITMAP(irqs, LGUEST_IRQS);
    +
    + if (!lg->lguest_data)
    + return;
    +
    + /* If timer has changed, set timer interrupt. */
    + if (lg->timer_on && jiffies != lg->last_timer)
    + set_bit(0, lg->irqs_pending);
    +
    + /* Mask out any interrupts they have blocked. */
    + copy_from_user(&irqs, lg->lguest_data->interrupts, sizeof(irqs));
    + bitmap_andnot(irqs, lg->irqs_pending, irqs, LGUEST_IRQS);
    +
    + irq = find_first_bit(irqs, LGUEST_IRQS);
    + if (irq >= LGUEST_IRQS)
    + return;
    +
    + /* If they're halted, we re-enable interrupts. */
    + if (lg->halted) {
    + /* Re-enable interrupts. */
    + put_user(512, &lg->lguest_data->irq_enabled);
    + lg->halted = 0;
    + } else {
    + /* Maybe they have interrupts disabled? */
    + u32 irq_enabled;
    + get_user(irq_enabled, &lg->lguest_data->irq_enabled);
    + if (!irq_enabled)
    + return;
    + }
    +
    + if (lg->interrupt[irq].addr != 0) {
    + clear_bit(irq, lg->irqs_pending);
    + reflect_trap(lg, &lg->interrupt[irq], 0);
    + }
    +}
    +
    +void check_bug_kill(struct lguest *lg)
    +{
    +#ifdef CONFIG_BUG
    + u32 eip = lg->state->regs.eip - PAGE_OFFSET;
    + u16 insn;
    +
    + /* This only works for addresses in linear mapping... */
    + if (lg->state->regs.eip < PAGE_OFFSET)
    + return;
    + lhread(lg, &insn, eip, sizeof(insn));
    + if (insn == 0x0b0f) {
    +#ifdef CONFIG_DEBUG_BUGVERBOSE
    + u16 l;
    + u32 f;
    + char file[128];
    + lhread(lg, &l, eip+sizeof(insn), sizeof(l));
    + lhread(lg, &f, eip+sizeof(insn)+sizeof(l), sizeof(f));
    + lhread(lg, file, f - PAGE_OFFSET, sizeof(file));
    + file[sizeof(file)-1] = 0;
    + kill_guest(lg, "BUG() at %#x %s:%u", eip, file, l);
    +#else
    + kill_guest(lg, "BUG() at %#x", eip);
    +#endif /* CONFIG_DEBUG_BUGVERBOSE */
    + }
    +#endif /* CONFIG_BUG */
    +}
    +
    +static void copy_trap(struct lguest *lg,
    + struct host_trap *trap,
    + const struct desc_struct *desc)
    +{
    + u8 type = ((desc->b >> 8) & 0xF);
    +
    + /* Not present? */
    + if (!(desc->b & 0x8000)) {
    + trap->addr = 0;
    + return;
    + }
    + if (type != 0xE && type != 0xF)
    + kill_guest(lg, "bad IDT type %i", type);
    + trap->disable_interrupts = (type == 0xE);
    + trap->addr = ((desc->a & 0x0000FFFF) | (desc->b & 0xFFFF0000));
    +}
    +
    +/* FIXME: Put this in hypervisor.S and do something clever with relocs? */
    +static u8 tramp[]
    += { 0x0f, 0xa8, 0x0f, 0xa9, /* push %gs; pop %gs */
    + 0x36, 0xc7, 0x05, 0x55, 0x55, 0x55, 0x55, 0x00, 0x00, 0x00, 0x00,
    + /* movl 0, %ss:lguest_data.gs_gpf_eip */
    + 0xe9, 0x55, 0x55, 0x55, 0x55 /* jmp dstaddr */
    +};
    +#define TRAMP_MOVL_TARGET_OFF 7
    +#define TRAMP_JMP_TARGET_OFF 16
    +
    +static u32 setup_trampoline(struct lguest *lg, unsigned int i, u32 dstaddr)
    +{
    + u32 addr, off;
    +
    + off = sizeof(tramp)*i;
    + memcpy(lg->trap_page + off, tramp, sizeof(tramp));
    +
    + /* 0 is to be placed in lguest_data.gs_gpf_eip. */
    + addr = (u32)&lg->lguest_data->gs_gpf_eip + lg->page_offset;
    + memcpy(lg->trap_page + off + TRAMP_MOVL_TARGET_OFF, &addr, 4);
    +
    + /* Address is relative to where end of jmp will be. */
    + addr = dstaddr - ((-4*1024*1024) + off + sizeof(tramp));
    + memcpy(lg->trap_page + off + TRAMP_JMP_TARGET_OFF, &addr, 4);
    + return (-4*1024*1024) + off;
    +}
    +
    +/* We bounce through the trap page, for two reasons: firstly, we need
    + the interrupt destination always mapped, to avoid double faults,
    + secondly we want to reload %gs to make it innocuous on entering kernel.
    + */
    +static void setup_idt(struct lguest *lg,
    + unsigned int i,
    + const struct desc_struct *desc)
    +{
    + u8 type = ((desc->b >> 8) & 0xF);
    + u32 taddr;
    +
    + /* Not present? */
    + if (!(desc->b & 0x8000)) {
    + /* FIXME: When we need this, we'll know... */
    + if (lg->state->idt_table[i].a & 0x8000)
    + kill_guest(lg, "removing interrupts not supported");
    + return;
    + }
    +
    + /* We could reflect and disable interrupts, but guest can do itself. */
    + if (type != 0xF)
    + kill_guest(lg, "bad direct IDT %i type %i", i, type);
    +
    + taddr = setup_trampoline(lg, i, (desc->a&0xFFFF)|(desc->b&0xFFFF0000));
    +
    + lg->state->idt_table[i].a = (((__KERNEL_CS|GUEST_DPL)<<16)
    + | (taddr & 0x0000FFFF));
    + lg->state->idt_table[i].b = (desc->b&0xEF00)|(taddr&0xFFFF0000);
    +}
    +
    +void load_guest_idt_entry(struct lguest *lg, unsigned int i, u32 low, u32 high)
    +{
    + struct desc_struct d = { low, high };
    +
    + switch (i) {
    + /* Ignore NMI, doublefault, hypercall, spurious interrupt. */
    + case 2:
    + case 8:
    + case 15:
    + case LGUEST_TRAP_ENTRY:
    + /* FIXME: We should handle debug and int3 */
    + case 1:
    + case 3:
    + return;
    + /* We intercept page fault, general protection fault and fpu missing */
    + case 13:
    + copy_trap(lg, &lg->gpf_trap, &d);
    + return;
    + case 14:
    + copy_trap(lg, &lg->page_trap, &d);
    + return;
    + case 7:
    + copy_trap(lg, &lg->fpu_trap, &d);
    + return;
    + }
    +
    + /* Other traps go straight to guest. */
    + if (i < FIRST_EXTERNAL_VECTOR || i == SYSCALL_VECTOR)
    + setup_idt(lg, i, &d);
    + /* A virtual interrupt */
    + else if (i < FIRST_EXTERNAL_VECTOR + LGUEST_IRQS)
    + copy_trap(lg, &lg->interrupt[i-FIRST_EXTERNAL_VECTOR], &d);
    +}
    +
    diff -r a31396449b82 arch/i386/lguest/io.c
    --- /dev/null Thu Jan 01 00:00:00 1970 +0000
    +++ b/arch/i386/lguest/io.c Mon Feb 12 12:59:41 2007 +1100
    @@ -0,0 +1,413 @@
    +/* Simple I/O model for guests, based on shared memory.
    + * Copyright (C) 2006 Rusty Russell IBM Corporation
    + *
    + * This program is free software; you can redistribute it and/or modify
    + * it under the terms of the GNU General Public License as published by
    + * the Free Software Foundation; either version 2 of the License, or
    + * (at your option) any later version.
    + *
    + * This program is distributed in the hope that it will be useful,
    + * but WITHOUT ANY WARRANTY; without even the implied warranty of
    + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    + * GNU General Public License for more details.
    + *
    + * You should have received a copy of the GNU General Public License
    + * along with this program; if not, write to the Free Software
    + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
    + */
    +#include <linux/types.h>
    +#include <linux/futex.h>
    +#include <linux/jhash.h>
    +#include <linux/mm.h>
    +#include <linux/highmem.h>
    +#include <linux/uaccess.h>
    +#include "lg.h"
    +
    +static struct list_head dma_hash[64];
    +
    +/* FIXME: allow multi-page lengths. */
    +static int check_dma_list(struct lguest *lg, const struct lguest_dma *dma)
    +{
    + unsigned int i;
    +
    + for (i = 0; i < LGUEST_MAX_DMA_SECTIONS; i++) {
    + if (!dma->len[i])
    + return 1;
    + if (!lguest_address_ok(lg, dma->addr[i]))
    + goto kill;
    + if (dma->len[i] > PAGE_SIZE)
    + goto kill;
    + /* We could do over a page, but is it worth it? */
    + if ((dma->addr[i] % PAGE_SIZE) + dma->len[i] > PAGE_SIZE)
    + goto kill;
    + }
    + return 1;
    +
    +kill:
    + kill_guest(lg, "bad DMA entry: %u@%#x", dma->len[i], dma->addr[i]);
    + return 0;
    +}
    +
    +static unsigned int hash(const union futex_key *key)
    +{
    + return jhash2((u32*)&key->both.word,
    + (sizeof(key->both.word)+sizeof(key->both.ptr))/4,
    + key->both.offset)
    + % ARRAY_SIZE(dma_hash);
    +}
    +
    +/* Must hold read lock on dmainfo owner's current->mm->mmap_sem */
    +static void unlink_dma(struct lguest_dma_info *dmainfo)
    +{
    + BUG_ON(!mutex_is_locked(&lguest_lock));
    + dmainfo->interrupt = 0;
    + list_del(&dmainfo->list);
    + drop_futex_key_refs(&dmainfo->key);
    +}
    +
    +static inline int key_eq(const union futex_key *a, const union futex_key *b)
    +{
    + return (a->both.word == b->both.word
    + && a->both.ptr == b->both.ptr
    + && a->both.offset == b->both.offset);
    +}
    +
    +static u32 unbind_dma(struct lguest *lg,
    + const union futex_key *key,
    + unsigned long dmas)
    +{
    + int i, ret = 0;
    +
    + for (i = 0; i < LGUEST_MAX_DMA; i++) {
    + if (key_eq(key, &lg->dma[i].key) && dmas == lg->dma[i].dmas) {
    + unlink_dma(&lg->dma[i]);
    + ret = 1;
    + break;
    + }
    + }
    + return ret;
    +}
    +
    +u32 bind_dma(struct lguest *lg,
    + unsigned long addr, unsigned long dmas, u16 numdmas, u8 interrupt)
    +{
    + unsigned int i;
    + u32 ret = 0;
    + union futex_key key;
    +
    + if (interrupt >= LGUEST_IRQS)
    + return 0;
    +
    + mutex_lock(&lguest_lock);
    + down_read(&current->mm->mmap_sem);
    + if (get_futex_key((u32 __user *)addr, &key) != 0) {
    + kill_guest(lg, "bad dma address %#lx", addr);
    + goto unlock;
    + }
    + get_futex_key_refs(&key);
    +
    + if (interrupt == 0)
    + ret = unbind_dma(lg, &key, dmas);
    + else {
    + for (i = 0; i < LGUEST_MAX_DMA; i++) {
    + if (lg->dma[i].interrupt == 0) {
    + lg->dma[i].dmas = dmas;
    + lg->dma[i].num_dmas = numdmas;
    + lg->dma[i].next_dma = 0;
    + lg->dma[i].key = key;
    + lg->dma[i].guestid = lg->guestid;
    + lg->dma[i].interrupt = interrupt;
    + list_add(&lg->dma[i].list,
    + &dma_hash[hash(&key)]);
    + ret = 1;
    + goto unlock;
    + }
    + }
    + }
    + drop_futex_key_refs(&key);
    +unlock:
    + up_read(&current->mm->mmap_sem);
    + mutex_unlock(&lguest_lock);
    + return ret;
    +}
    +
    +/* lhread from another guest */
    +static int lhread_other(struct lguest *lg,
    + void *buf, u32 addr, unsigned bytes)
    +{
    + if (addr + bytes < addr
    + || !lguest_address_ok(lg, addr+bytes)
    + || access_process_vm(lg->tsk, addr, buf, bytes, 0) != bytes) {
    + memset(buf, 0, bytes);
    + kill_guest(lg, "bad address in registered DMA struct");
    + return 0;
    + }
    + return 1;
    +}
    +
    +/* lhwrite to another guest */
    +static int lhwrite_other(struct lguest *lg, u32 addr,
    + const void *buf, unsigned bytes)
    +{
    + if (addr + bytes < addr
    + || !lguest_address_ok(lg, addr+bytes)
    + || (access_process_vm(lg->tsk, addr, (void *)buf, bytes, 1)
    + != bytes)) {
    + kill_guest(lg, "bad address writing to registered DMA");
    + return 0;
    + }
    + return 1;
    +}
    +
    +static u32 copy_data(const struct lguest_dma *src,
    + const struct lguest_dma *dst,
    + struct page *pages[])
    +{
    + unsigned int totlen, si, di, srcoff, dstoff;
    + void *maddr = NULL;
    +
    + totlen = 0;
    + si = di = 0;
    + srcoff = dstoff = 0;
    + while (si < LGUEST_MAX_DMA_SECTIONS && src->len[si]
    + && di < LGUEST_MAX_DMA_SECTIONS && dst->len[di]) {
    + u32 len = min(src->len[si] - srcoff, dst->len[di] - dstoff);
    +
    + if (!maddr)
    + maddr = kmap(pages[di]);
    +
    + /* FIXME: This is not completely portable, since
    + archs do different things for copy_to_user_page. */
    + if (copy_from_user(maddr + (dst->addr[di] + dstoff)%PAGE_SIZE,
    + (void *__user)src->addr[si], len) != 0) {
    + totlen = 0;
    + break;
    + }
    +
    + totlen += len;
    + srcoff += len;
    + dstoff += len;
    + if (srcoff == src->len[si]) {
    + si++;
    + srcoff = 0;
    + }
    + if (dstoff == dst->len[di]) {
    + kunmap(pages[di]);
    + maddr = NULL;
    + di++;
    + dstoff = 0;
    + }
    + }
    +
    + if (maddr)
    + kunmap(pages[di]);
    +
    + return totlen;
    +}
    +
    +/* Src is us, ie. current. */
    +static u32 do_dma(struct lguest *srclg, const struct lguest_dma *src,
    + struct lguest *dstlg, const struct lguest_dma *dst)
    +{
    + int i;
    + u32 ret;
    + struct page *pages[LGUEST_MAX_DMA_SECTIONS];
    +
    + if (!check_dma_list(dstlg, dst) || !check_dma_list(srclg, src))
    + return 0;
    +
    + /* First get the destination pages */
    + for (i = 0; i < LGUEST_MAX_DMA_SECTIONS; i++) {
    + if (dst->len[i] == 0)
    + break;
    + if (get_user_pages(dstlg->tsk, dstlg->mm,
    + dst->addr[i], 1, 1, 1, pages+i, NULL)
    + != 1) {
    + ret = 0;
    + goto drop_pages;
    + }
    + }
    +
    + /* Now copy until we run out of src or dst. */
    + ret = copy_data(src, dst, pages);
    +
    +drop_pages:
    + while (--i >= 0)
    + put_page(pages[i]);
    + return ret;
    +}
    +
    +/* We cache one process to wakeup: helps for batching & wakes outside locks. */
    +void set_wakeup_process(struct lguest *lg, struct task_struct *p)
    +{
    + if (p == lg->wake)
    + return;
    +
    + if (lg->wake) {
    + wake_up_process(lg->wake);
    + put_task_struct(lg->wake);
    + }
    + lg->wake = p;
    + if (lg->wake)
    + get_task_struct(lg->wake);
    +}
    +
    +static int dma_transfer(struct lguest *srclg,
    + unsigned long udma,
    + struct lguest_dma_info *dst)
    +{
    + struct lguest_dma dst_dma, src_dma;
    + struct lguest *dstlg;
    + u32 i, dma = 0;
    +
    + dstlg = &lguests[dst->guestid];
    + /* Get our dma list. */
    + lhread(srclg, &src_dma, udma, sizeof(src_dma));
    +
    + /* We can't deadlock against them dmaing to us, because this
    + * is all under the lguest_lock. */
    + down_read(&dstlg->mm->mmap_sem);
    +
    + for (i = 0; i < dst->num_dmas; i++) {
    + dma = (dst->next_dma + i) % dst->num_dmas;
    + if (!lhread_other(dstlg, &dst_dma,
    + dst->dmas + dma * sizeof(struct lguest_dma),
    + sizeof(dst_dma))) {
    + goto fail;
    + }
    + if (!dst_dma.used_len)
    + break;
    + }
    + if (i != dst->num_dmas) {
    + unsigned long used_lenp;
    + unsigned int ret;
    +
    + ret = do_dma(srclg, &src_dma, dstlg, &dst_dma);
    + /* Put used length in src. */
    + lhwrite_u32(srclg,
    + udma+offsetof(struct lguest_dma, used_len), ret);
    + if (ret == 0 && src_dma.len[0] != 0)
    + goto fail;
    +
    + /* Make sure destination sees contents before length. */
    + mb();
    + used_lenp = dst->dmas
    + + dma * sizeof(struct lguest_dma)
    + + offsetof(struct lguest_dma, used_len);
    + lhwrite_other(dstlg, used_lenp, &ret, sizeof(ret));
    + dst->next_dma++;
    + }
    + up_read(&dstlg->mm->mmap_sem);
    +
    + /* Do this last so dst doesn't simply sleep on lock. */
    + set_bit(dst->interrupt, dstlg->irqs_pending);
    + set_wakeup_process(srclg, dstlg->tsk);
    + return i == dst->num_dmas;
    +
    +fail:
    + up_read(&dstlg->mm->mmap_sem);
    + return 0;
    +}
    +
    +int send_dma(struct lguest *lg, unsigned long addr, unsigned long udma)
    +{
    + union futex_key key;
    + int pending = 0, empty = 0;
    +
    +again:
    + mutex_lock(&lguest_lock);
    + down_read(&current->mm->mmap_sem);
    + if (get_futex_key((u32 __user *)addr, &key) != 0) {
    + kill_guest(lg, "bad sending DMA address");
    + goto unlock;
    + }
    + /* Shared mapping? Look for other guests... */
    + if (key.shared.offset & 1) {
    + struct lguest_dma_info *i, *n;
    + list_for_each_entry_safe(i, n, &dma_hash[hash(&key)], list) {
    + if (i->guestid == lg->guestid)
    + continue;
    + if (!key_eq(&key, &i->key))
    + continue;
    +
    + empty += dma_transfer(lg, udma, i);
    + break;
    + }
    + if (empty == 1) {
    + /* Give any recipients one chance to restock. */
    + up_read(&current->mm->mmap_sem);
    + mutex_unlock(&lguest_lock);
    + yield();
    + empty++;
    + goto again;
    + }
    + pending = 0;
    + } else {
    + /* Private mapping: tell our userspace. */
    + lg->dma_is_pending = 1;
    + lg->pending_dma = udma;
    + lg->pending_addr = addr;
    + pending = 1;
    + }
    +unlock:
    + up_read(&current->mm->mmap_sem);
    + mutex_unlock(&lguest_lock);
    + return pending;
    +}
    +
    +void release_all_dma(struct lguest *lg)
    +{
    + unsigned int i;
    +
    + BUG_ON(!mutex_is_locked(&lguest_lock));
    +
    + down_read(&lg->mm->mmap_sem);
    + for (i = 0; i < LGUEST_MAX_DMA; i++) {
    + if (lg->dma[i].interrupt)
    + unlink_dma(&lg->dma[i]);
    + }
    + up_read(&lg->mm->mmap_sem);
    +}
    +
    +/* Userspace wants a dma buffer from this guest. */
    +unsigned long get_dma_buffer(struct lguest *lg,
    + unsigned long addr, unsigned long *interrupt)
    +{
    + unsigned long ret = 0;
    + union futex_key key;
    + struct lguest_dma_info *i;
    +
    + mutex_lock(&lguest_lock);
    + down_read(&current->mm->mmap_sem);
    + if (get_futex_key((u32 __user *)addr, &key) != 0) {
    + kill_guest(lg, "bad registered DMA buffer");
    + goto unlock;
    + }
    + list_for_each_entry(i, &dma_hash[hash(&key)], list) {
    + if (key_eq(&key, &i->key) && i->guestid == lg->guestid) {
    + unsigned int j;
    + for (j = 0; j < i->num_dmas; j++) {
    + struct lguest_dma dma;
    +
    + ret = i->dmas + j * sizeof(struct lguest_dma);
    + lhread(lg, &dma, ret, sizeof(dma));
    + if (dma.used_len == 0)
    + break;
    + }
    + *interrupt = i->interrupt;
    + break;
    + }
    + }
    +unlock:
    + up_read(&current->mm->mmap_sem);
    + mutex_unlock(&lguest_lock);
    + return ret;
    +}
    +
    +void lguest_io_init(void)
    +{
    + unsigned int i;
    +
    + for (i = 0; i < ARRAY_SIZE(dma_hash); i++)
    + INIT_LIST_HEAD(&dma_hash[i]);
    +}
    diff -r a31396449b82 arch/i386/lguest/lg.h
    --- a/arch/i386/lguest/lg.h Mon Feb 12 12:59:39 2007 +1100
    +++ b/arch/i386/lguest/lg.h Mon Feb 12 12:59:41 2007 +1100
    @@ -3,8 +3,8 @@

    #include <asm/desc.h>
    /* 64k ought to be enough for anybody! */
    -#define HYPERVISOR_MAP_ORDER 16
    -#define HYPERVISOR_PAGES ((1 << HYPERVISOR_MAP_ORDER)/PAGE_SIZE)
    +#define HYPERVISOR_PAGE_ORDER (16 - PAGE_SHIFT)
    +#define HYPERVISOR_PAGES (1 << HYPERVISOR_PAGE_ORDER)

    #define GDT_ENTRY_LGUEST_CS 10
    #define GDT_ENTRY_LGUEST_DS 11
    diff -r a31396449b82 arch/i386/lguest/lguest_user.c
    --- /dev/null Thu Jan 01 00:00:00 1970 +0000
    +++ b/arch/i386/lguest/lguest_user.c Mon Feb 12 12:59:41 2007 +1100
    @@ -0,0 +1,242 @@
    +/* Userspace control of the guest, via /dev/lguest. */
    +#include <linux/uaccess.h>
    +#include <linux/miscdevice.h>
    +#include <linux/fs.h>
    +#include "lg.h"
    +
    +static struct lguest_state *setup_guest_state(unsigned int num, void *pgdir,
    + unsigned long start)
    +{
    + struct lguest_state *guest = &__lguest_states()[num];
    + unsigned int i;
    + const long *def = __lguest_default_idt_entries();
    + struct lguest_regs *regs;
    +
    + guest->gdt_table[GDT_ENTRY_KERNEL_CS] = FULL_EXEC_SEGMENT;
    + guest->gdt_table[GDT_ENTRY_KERNEL_DS] = FULL_SEGMENT;
    + guest->gdt.size = GDT_ENTRIES*8-1;
    + guest->gdt.address = (unsigned long)&guest->gdt_table;
    +
    + /* Other guest's IDTs are initialized from default. */
    + guest->idt.size = 8 * IDT_ENTRIES;
    + guest->idt.address = (long)guest->idt_table;
    + for (i = 0; i < IDT_ENTRIES; i++) {
    + u32 flags = 0x8e00;
    +
    + /* They can't "int" into any of them except hypercall. */
    + if (i == LGUEST_TRAP_ENTRY)
    + flags |= (GUEST_DPL << 13);
    +
    + guest->idt_table[i].a = (LGUEST_CS<<16) | (def[i]&0x0000FFFF);
    + guest->idt_table[i].b = (def[i]&0xFFFF0000) | flags;
    + }
    +
    + memset(&guest->tss, 0, sizeof(guest->tss));
    + guest->tss.ss0 = LGUEST_DS;
    + guest->tss.esp0 = (unsigned long)(guest+1);
    + guest->tss.io_bitmap_base = sizeof(guest->tss); /* No I/O for you! */
    +
    + /* Write out stack in format lguest expects, so we can switch to it. */
    + regs = &guest->regs;
    + regs->cr3 = __pa(pgdir);
    + regs->eax = regs->ebx = regs->ecx = regs->edx = regs->esp = 0;
    + regs->edi = LGUEST_MAGIC_EDI;
    + regs->ebp = LGUEST_MAGIC_EBP;
    + regs->esi = LGUEST_MAGIC_ESI;
    + regs->gs = regs->fs = 0;
    + regs->ds = regs->es = __KERNEL_DS|GUEST_DPL;
    + regs->trapnum = regs->errcode = 0;
    + regs->eip = start;
    + regs->cs = __KERNEL_CS|GUEST_DPL;
    + regs->eflags = 0x202; /* Interrupts enabled. */
    + regs->ss = __KERNEL_DS|GUEST_DPL;
    +
    + if (!fixup_gdt_table(guest->gdt_table, ARRAY_SIZE(guest->gdt_table),
    + &guest->regs, &guest->tss))
    + return NULL;
    +
    + return guest;
    +}
    +
    +/* + addr */
    +static long user_get_dma(struct lguest *lg, const u32 __user *input)
    +{
    + unsigned long addr, udma, irq;
    +
    + if (get_user(addr, input) != 0)
    + return -EFAULT;
    + udma = get_dma_buffer(lg, addr, &irq);
    + if (!udma)
    + return -ENOENT;
    +
    + /* We put irq number in udma->used_len. */
    + lhwrite_u32(lg, udma + offsetof(struct lguest_dma, used_len), irq);
    + return udma;
    +}
    +
    +/* + irq */
    +static int user_send_irq(struct lguest *lg, const u32 __user *input)
    +{
    + u32 irq;
    +
    + if (get_user(irq, input) != 0)
    + return -EFAULT;
    + if (irq >= LGUEST_IRQS)
    + return -EINVAL;
    + set_bit(irq, lg->irqs_pending);
    + return 0;
    +}
    +
    +static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
    +{
    + struct lguest *lg = file->private_data;
    +
    + if (!lg)
    + return -EINVAL;
    +
    + if (lg->dead) {
    + size_t len;
    +
    + if (lg->dead == (void *)-1)
    + return -ENOMEM;
    +
    + 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;
    +
    + return run_guest(lg, user);
    +}
    +
    +/* Take: pfnlimit, pgdir, start, pageoffset. */
    +static int initialize(struct file *file, const u32 __user *input)
    +{
    + struct lguest *lg;
    + int err, i;
    + u32 args[4];
    +
    + if (file->private_data)
    + return -EBUSY;
    +
    + if (copy_from_user(args, input, sizeof(args)) != 0)
    + return -EFAULT;
    +
    + if (args[1] <= PAGE_SIZE)
    + return -EINVAL;
    +
    + mutex_lock(&lguest_lock);
    + i = find_free_guest();
    + if (i < 0) {
    + err = -ENOSPC;
    + goto unlock;
    + }
    + lg = &lguests[i];
    + lg->guestid = i;
    + lg->pfn_limit = args[0];
    + lg->page_offset = args[3];
    +
    + lg->trap_page = (u32 *)get_zeroed_page(GFP_KERNEL);
    + if (!lg->trap_page) {
    + err = -ENOMEM;
    + goto release_guest;
    + }
    +
    + err = init_guest_pagetable(lg, args[1]);
    + if (err)
    + goto free_trap_page;
    +
    + lg->state = setup_guest_state(i, lg->pgdirs[lg->pgdidx].pgdir,args[2]);
    + if (!lg->state) {
    + err = -ENOEXEC;
    + goto release_pgtable;
    + }
    + mutex_unlock(&lguest_lock);
    +
    + lg->tsk = current;
    + lg->mm = get_task_mm(current);
    + file->private_data = lg;
    + return sizeof(args);
    +
    +release_pgtable:
    + free_guest_pagetable(lg);
    +free_trap_page:
    + free_page((long)lg->trap_page);
    +release_guest:
    + memset(lg, 0, sizeof(*lg));
    +unlock:
    + mutex_unlock(&lguest_lock);
    + return err;
    +}
    +
    +static ssize_t write(struct file *file, const char __user *input,
    + size_t size, loff_t *off)
    +{
    + struct lguest *lg = file->private_data;
    + u32 req;
    +
    + if (get_user(req, input) != 0)
    + return -EFAULT;
    + input += sizeof(req);
    +
    + if (req != LHREQ_INITIALIZE && !lg)
    + return -EINVAL;
    + if (lg && lg->dead)
    + return -ENOENT;
    +
    + switch (req) {
    + case LHREQ_INITIALIZE:
    + return initialize(file, (const u32 __user *)input);
    + case LHREQ_GETDMA:
    + return user_get_dma(lg, (const u32 __user *)input);
    + case LHREQ_IRQ:
    + return user_send_irq(lg, (const u32 __user *)input);
    + default:
    + return -EINVAL;
    + }
    +}
    +
    +static int close(struct inode *inode, struct file *file)
    +{
    + struct lguest *lg = file->private_data;
    +
    + if (!lg)
    + return 0;
    +
    + mutex_lock(&lguest_lock);
    + release_all_dma(lg);
    + free_page((long)lg->trap_page);
    + free_guest_pagetable(lg);
    + mmput(lg->mm);
    + if (lg->dead != (void *)1)
    + kfree(lg->dead);
    + memset(lg->state, 0, sizeof(*lg->state));
    + memset(lg, 0, sizeof(*lg));
    + mutex_unlock(&lguest_lock);
    + return 0;
    +}
    +
    +static struct file_operations lguest_fops = {
    + .owner = THIS_MODULE,
    + .release = close,
    + .write = write,
    + .read = read,
    +};
    +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);
    +}
    diff -r a31396449b82 arch/i386/lguest/page_tables.c
    --- /dev/null Thu Jan 01 00:00:00 1970 +0000
    +++ b/arch/i386/lguest/page_tables.c Mon Feb 12 12:59:41 2007 +1100
    @@ -0,0 +1,374 @@
    +/* Shadow page table operations.
    + * Copyright (C) Rusty Russell IBm Corporation 2006.
    + * GPL v2 and any later version */
    +#include <linux/mm.h>
    +#include <linux/types.h>
    +#include <linux/spinlock.h>
    +#include <linux/random.h>
    +#include <linux/percpu.h>
    +#include <asm/tlbflush.h>
    +#include "lg.h"
    +
    +#define PTES_PER_PAGE_SHIFT 10
    +#define PTES_PER_PAGE (1 << PTES_PER_PAGE_SHIFT)
    +#define HYPERVISOR_PGD_ENTRY (PTES_PER_PAGE - 1)
    +
    +static DEFINE_PER_CPU(u32 *, hypervisor_pte_pages) = { NULL };
    +#define hypervisor_pte_page(cpu) per_cpu(hypervisor_pte_pages, cpu)
    +
    +static unsigned vaddr_to_pgd(unsigned long vaddr)
    +{
    + return vaddr >> (PAGE_SHIFT + PTES_PER_PAGE_SHIFT);
    +}
    +
    +/* These access the real versions. */
    +static u32 *toplev(struct lguest *lg, u32 i, unsigned long vaddr)
    +{
    + unsigned int index = vaddr_to_pgd(vaddr);
    +
    + if (index >= HYPERVISOR_PGD_ENTRY) {
    + kill_guest(lg, "attempt to access hypervisor pages");
    + index = 0;
    + }
    + return &lg->pgdirs[i].pgdir[index];
    +}
    +
    +static u32 *pteof(struct lguest *lg, u32 top, unsigned long vaddr)
    +{
    + u32 *page = __va(top&PAGE_MASK);
    + BUG_ON(!(top & _PAGE_PRESENT));
    + return &page[(vaddr >> PAGE_SHIFT) % PTES_PER_PAGE];
    +}
    +
    +/* These access the guest versions. */
    +static u32 gtoplev(struct lguest *lg, unsigned long vaddr)
    +{
    + unsigned int index = vaddr >> (PAGE_SHIFT + PTES_PER_PAGE_SHIFT);
    + return lg->pgdirs[lg->pgdidx].cr3 + index * sizeof(u32);
    +}
    +
    +static u32 gpteof(struct lguest *lg, u32 gtop, unsigned long vaddr)
    +{
    + u32 gpage = (gtop&PAGE_MASK);
    + BUG_ON(!(gtop & _PAGE_PRESENT));
    + return gpage + ((vaddr >> PAGE_SHIFT) % PTES_PER_PAGE) * sizeof(u32);
    +}
    +
    +static void release_pte(u32 pte)
    +{
    + if (pte & _PAGE_PRESENT)
    + put_page(pfn_to_page(pte >> PAGE_SHIFT));
    +}
    +
    +/* Do a virtual -> physical mapping on a user page. */
    +static unsigned long get_pfn(unsigned long virtpfn, int write)
    +{
    + struct vm_area_struct *vma;
    + struct page *page;
    + unsigned long ret = -1UL;
    +
    + down_read(&current->mm->mmap_sem);
    + if (get_user_pages(current, current->mm, virtpfn << PAGE_SHIFT,
    + 1, write, 1, &page, &vma) == 1)
    + ret = page_to_pfn(page);
    + up_read(&current->mm->mmap_sem);
    + return ret;
    +}
    +
    +static u32 check_pgtable_entry(struct lguest *lg, u32 entry)
    +{
    + if ((entry & (_PAGE_PWT|_PAGE_PSE))
    + || (entry >> PAGE_SHIFT) >= lg->pfn_limit)
    + kill_guest(lg, "bad page table entry");
    + return entry & ~_PAGE_GLOBAL;
    +}
    +
    +static u32 get_pte(struct lguest *lg, u32 entry, int write)
    +{
    + u32 pfn;
    +
    + pfn = get_pfn(entry >> PAGE_SHIFT, write);
    + if (pfn == -1UL) {
    + kill_guest(lg, "failed to get page %u", entry>>PAGE_SHIFT);
    + return 0;
    + }
    + return ((pfn << PAGE_SHIFT) | (entry & (PAGE_SIZE-1)));
    +}
    +
    +/* FIXME: We hold reference to pages, which prevents them from being
    + swapped. It'd be nice to have a callback when Linux wants to swap out. */
    +
    +/* We fault pages in, which allows us to update accessed/dirty bits.
    + * Return NULL or the pte page. */
    +static int page_in(struct lguest *lg, u32 vaddr, unsigned flags)
    +{
    + u32 gtop, gpte;
    + u32 *top, *pte, *ptepage;
    + u32 val;
    +
    + gtop = gtoplev(lg, vaddr);
    + val = lhread_u32(lg, gtop);
    + if (!(val & _PAGE_PRESENT))
    + return 0;
    +
    + top = toplev(lg, lg->pgdidx, vaddr);
    + if (!(*top & _PAGE_PRESENT)) {
    + /* Get a PTE page for them. */
    + ptepage = (void *)get_zeroed_page(GFP_KERNEL);
    + /* FIXME: Steal from self in this case? */
    + if (!ptepage) {
    + kill_guest(lg, "out of memory allocating pte page");
    + return 0;
    + }
    + val = check_pgtable_entry(lg, val);
    + *top = (__pa(ptepage) | (val & (PAGE_SIZE-1)));
    + } else
    + ptepage = __va(*top & PAGE_MASK);
    +
    + gpte = gpteof(lg, val, vaddr);
    + val = lhread_u32(lg, gpte);
    +
    + /* No page, or write to readonly page? */
    + if (!(val&_PAGE_PRESENT) || ((flags&_PAGE_DIRTY) && !(val&_PAGE_RW)))
    + return 0;
    +
    + pte = pteof(lg, *top, vaddr);
    + val = check_pgtable_entry(lg, val) | flags;
    +
    + /* We're done with the old pte. */
    + release_pte(*pte);
    +
    + /* We don't make it writable if this isn't a write: later
    + * write will fault so we can set dirty bit in guest. */
    + if (val & _PAGE_DIRTY)
    + *pte = get_pte(lg, val, 1);
    + else
    + *pte = get_pte(lg, val & ~_PAGE_RW, 0);
    +
    + /* Now we update dirty/accessed on guest. */
    + lhwrite_u32(lg, gpte, val);
    + return 1;
    +}
    +
    +int demand_page(struct lguest *lg, u32 vaddr, int write)
    +{
    + return page_in(lg, vaddr, (write ? _PAGE_DIRTY : 0)|_PAGE_ACCESSED);
    +}
    +
    +void pin_stack_pages(struct lguest *lg)
    +{
    + unsigned int i;
    + u32 stack = lg->state->tss.esp1;
    +
    + for (i = 0; i < lg->stack_pages; i++)
    + if (!demand_page(lg, stack - i*PAGE_SIZE, 1))
    + kill_guest(lg, "bad stack page %i@%#x", i, stack);
    +}
    +
    +static unsigned int find_pgdir(struct lguest *lg, u32 pgtable)
    +{
    + unsigned int i;
    + for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++)
    + if (lg->pgdirs[i].cr3 == pgtable)
    + break;
    + return i;
    +}
    +
    +static void release_pgd(struct lguest *lg, u32 *pgd)
    +{
    + if (*pgd & _PAGE_PRESENT) {
    + unsigned int i;
    + u32 *ptepage = __va(*pgd & ~(PAGE_SIZE-1));
    + for (i = 0; i < PTES_PER_PAGE; i++)
    + release_pte(ptepage[i]);
    + free_page((long)ptepage);
    + *pgd = 0;
    + }
    +}
    +
    +static void flush_user_mappings(struct lguest *lg, int idx)
    +{
    + unsigned int i;
    + for (i = 0; i < vaddr_to_pgd(lg->page_offset); i++)
    + release_pgd(lg, lg->pgdirs[idx].pgdir + i);
    +}
    +
    +void guest_pagetable_flush_user(struct lguest *lg)
    +{
    + flush_user_mappings(lg, lg->pgdidx);
    +}
    +
    +static unsigned int new_pgdir(struct lguest *lg, u32 cr3)
    +{
    + unsigned int next;
    +
    + next = (lg->pgdidx + random32()) % ARRAY_SIZE(lg->pgdirs);
    + if (!lg->pgdirs[next].pgdir) {
    + lg->pgdirs[next].pgdir = (u32 *)get_zeroed_page(GFP_KERNEL);
    + if (!lg->pgdirs[next].pgdir)
    + next = lg->pgdidx;
    + }
    + lg->pgdirs[next].cr3 = cr3;
    + /* Release all the non-kernel mappings. */
    + flush_user_mappings(lg, next);
    +
    + return next;
    +}
    +
    +void guest_new_pagetable(struct lguest *lg, u32 pgtable)
    +{
    + int newpgdir;
    +
    + newpgdir = find_pgdir(lg, pgtable);
    + if (newpgdir == ARRAY_SIZE(lg->pgdirs))
    + newpgdir = new_pgdir(lg, pgtable);
    + lg->pgdidx = newpgdir;
    + lg->state->regs.cr3 = __pa(lg->pgdirs[lg->pgdidx].pgdir);
    + pin_stack_pages(lg);
    +}
    +
    +static void release_all_pagetables(struct lguest *lg)
    +{
    + unsigned int i, j;
    +
    + for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++)
    + if (lg->pgdirs[i].pgdir)
    + for (j = 0; j < HYPERVISOR_PGD_ENTRY; j++)
    + release_pgd(lg, lg->pgdirs[i].pgdir + j);
    +}
    +
    +void guest_pagetable_clear_all(struct lguest *lg)
    +{
    + release_all_pagetables(lg);
    + pin_stack_pages(lg);
    +}
    +
    +static void do_set_pte(struct lguest *lg, int idx,
    + unsigned long vaddr, u32 val)
    +{
    + u32 *top = toplev(lg, idx, vaddr);
    + if (*top & _PAGE_PRESENT) {
    + u32 *pte = pteof(lg, *top, vaddr);
    + release_pte(*pte);
    + if (val & (_PAGE_DIRTY | _PAGE_ACCESSED)) {
    + val = check_pgtable_entry(lg, val);
    + *pte = get_pte(lg, val, val & _PAGE_DIRTY);
    + } else
    + *pte = 0;
    + }
    +}
    +
    +void guest_set_pte(struct lguest *lg,
    + unsigned long cr3, unsigned long vaddr, u32 val)
    +{
    + /* Kernel mappings must be changed on all top levels. */
    + if (vaddr >= lg->page_offset) {
    + unsigned int i;
    + for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++)
    + if (lg->pgdirs[i].pgdir)
    + do_set_pte(lg, i, vaddr, val);
    + } else {
    + int pgdir = find_pgdir(lg, cr3);
    + if (pgdir != ARRAY_SIZE(lg->pgdirs))
    + do_set_pte(lg, pgdir, vaddr, val);
    + }
    +}
    +
    +void guest_set_pud(struct lguest *lg, unsigned long cr3, u32 idx)
    +{
    + int pgdir;
    +
    + if (idx >= HYPERVISOR_PGD_ENTRY)
    + return;
    +
    + pgdir = find_pgdir(lg, cr3);
    + if (pgdir < ARRAY_SIZE(lg->pgdirs))
    + release_pgd(lg, lg->pgdirs[pgdir].pgdir + idx);
    +}
    +
    +int init_guest_pagetable(struct lguest *lg, u32 pgtable)
    +{
    + /* We assume this in flush_user_mappings, so check now */
    + if (vaddr_to_pgd(lg->page_offset) >= HYPERVISOR_PGD_ENTRY)
    + return -EINVAL;
    + lg->pgdidx = 0;
    + lg->pgdirs[lg->pgdidx].cr3 = pgtable;
    + lg->pgdirs[lg->pgdidx].pgdir = (u32*)get_zeroed_page(GFP_KERNEL);
    + if (!lg->pgdirs[lg->pgdidx].pgdir)
    + return -ENOMEM;
    + return 0;
    +}
    +
    +void free_guest_pagetable(struct lguest *lg)
    +{
    + unsigned int i;
    +
    + release_all_pagetables(lg);
    + for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++)
    + free_page((long)lg->pgdirs[i].pgdir);
    +}
    +
    +/* Caller must be preempt-safe */
    +void map_trap_page(struct lguest *lg)
    +{
    + int cpu = smp_processor_id();
    +
    + hypervisor_pte_page(cpu)[0] = (__pa(lg->trap_page)|_PAGE_PRESENT);
    +
    + /* Since hypervisor less that 4MB, we simply mug top pte page. */
    + lg->pgdirs[lg->pgdidx].pgdir[HYPERVISOR_PGD_ENTRY] =
    + (__pa(hypervisor_pte_page(cpu))| _PAGE_KERNEL);
    +}
    +
    +static void free_hypervisor_pte_pages(void)
    +{
    + int i;
    +
    + for_each_possible_cpu(i)
    + free_page((long)hypervisor_pte_page(i));
    +}
    +
    +static __init int alloc_hypervisor_pte_pages(void)
    +{
    + int i;
    +
    + for_each_possible_cpu(i) {
    + hypervisor_pte_page(i) = (u32 *)get_zeroed_page(GFP_KERNEL);
    + if (!hypervisor_pte_page(i)) {
    + free_hypervisor_pte_pages();
    + return -ENOMEM;
    + }
    + }
    + return 0;
    +}
    +
    +static __init void populate_hypervisor_pte_page(int cpu)
    +{
    + int i;
    + u32 *pte = hypervisor_pte_page(cpu);
    +
    + for (i = 0; i < HYPERVISOR_PAGES; i++) {
    + /* First entry set dynamically in map_trap_page */
    + pte[i+1] = ((page_to_pfn(&hype_pages[i]) << PAGE_SHIFT)
    + | _PAGE_KERNEL_EXEC);
    + }
    +}
    +
    +__init int init_pagetables(struct page hype_pages[])
    +{
    + int ret;
    + unsigned int i;
    +
    + ret = alloc_hypervisor_pte_pages();
    + if (ret)
    + return ret;
    +
    + for_each_possible_cpu(i)
    + populate_hypervisor_pte_page(i);
    + return 0;
    +}
    +
    +__exit void free_pagetables(void)
    +{
    + free_hypervisor_pte_pages();
    +}
    diff -r a31396449b82 arch/i386/lguest/segments.c
    --- /dev/null Thu Jan 01 00:00:00 1970 +0000
    +++ b/arch/i386/lguest/segments.c Mon Feb 12 12:59:41 2007 +1100
    @@ -0,0 +1,171 @@
    +#include "lg.h"
    +
    +/* Dealing with GDT entries is such a horror, I convert to sanity and back */
    +struct decoded_gdt_entry
    +{
    + u32 base, limit;
    + union {
    + struct {
    + unsigned type:4;
    + unsigned dtype:1;
    + unsigned dpl:2;
    + unsigned present:1;
    + unsigned unused:4;
    + unsigned avl:1;
    + unsigned mbz:1;
    + unsigned def:1;
    + unsigned page_granularity:1;
    + };
    + u16 raw_attributes;
    + };
    +};
    +
    +static struct decoded_gdt_entry decode_gdt_entry(const struct desc_struct *en)
    +{
    + struct decoded_gdt_entry de;
    + de.base = ((en->a >> 16) | ((en->b & 0xff) << 16)
    + | (en->b & 0xFF000000));
    + de.limit = ((en->a & 0xFFFF) | (en->b & 0xF0000));
    + de.raw_attributes = (en->b >> 8);
    + return de;
    +}
    +
    +static struct desc_struct encode_gdt_entry(const struct decoded_gdt_entry *de)
    +{
    + struct desc_struct en;
    + en.a = ((de->limit & 0xFFFF) | (de->base << 16));
    + en.b = (((de->base >> 16) & 0xFF)
    + | ((((u32)de->raw_attributes) & 0xF0FF) << 8)
    + | (de->limit & 0xF0000)
    + | (de->base & 0xFF000000));
    + return en;
    +}
    +
    +static int check_desc(const struct decoded_gdt_entry *dec)
    +{
    + return (dec->mbz == 0 && dec->dtype == 1 && (dec->type & 4) == 0);
    +}
    +
    +static void check_segment(const struct desc_struct *gdt, u32 *segreg)
    +{
    + if (*segreg > 255 || !(gdt[*segreg >> 3].b & 0x8000))
    + *segreg = 0;
    +}
    +
    +/* Ensure our manually-loaded segment regs don't fault in switch_to_guest. */
    +static void check_live_segments(const struct desc_struct *gdt,
    + struct lguest_regs *regs)
    +{
    + check_segment(gdt, &regs->es);
    + check_segment(gdt, &regs->ds);
    + check_segment(gdt, &regs->fs);
    + check_segment(gdt, &regs->gs);
    +}
    +
    +int fixup_gdt_table(struct desc_struct *gdt, unsigned int num,
    + struct lguest_regs *regs, struct x86_tss *tss)
    +{
    + unsigned int i;
    + struct decoded_gdt_entry dec;
    +
    + for (i = 0; i < num; i++) {
    + unsigned long base, length;
    +
    + /* We override these ones, so we don't care what they give. */
    + if (i == GDT_ENTRY_TSS
    + || i == GDT_ENTRY_LGUEST_CS
    + || i == GDT_ENTRY_LGUEST_DS
    + || i == GDT_ENTRY_DOUBLEFAULT_TSS)
    + continue;
    +
    + dec = decode_gdt_entry(&gdt[i]);
    + if (!dec.present)
    + continue;
    +
    + if (!check_desc(&dec))
    + return 0;
    +
    + base = dec.base;
    + length = dec.limit + 1;
    + if (dec.page_granularity) {
    + base *= PAGE_SIZE;
    + length *= PAGE_SIZE;
    + }
    +
    + /* Unacceptable base? */
    + if (base >= HYPE_ADDR)
    + return 0;
    +
    + /* Wrap around or segment overlaps hypervisor mem? */
    + if (!length
    + || base + length < base
    + || base + length > HYPE_ADDR) {
    + /* Trim to edge of hypervisor. */
    + length = HYPE_ADDR - base;
    + if (dec.page_granularity)
    + dec.limit = (length / PAGE_SIZE) - 1;
    + else
    + dec.limit = length - 1;
    + }
    + if (dec.dpl == 0)
    + dec.dpl = GUEST_DPL;
    + gdt[i] = encode_gdt_entry(&dec);
    + }
    + check_live_segments(gdt, regs);
    +
    + /* Now put in hypervisor data and code segments. */
    + gdt[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
    + gdt[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
    +
    + /* Finally, TSS entry */
    + dec.base = (unsigned long)tss;
    + dec.limit = sizeof(*tss)-1;
    + dec.type = 0x9;
    + dec.dtype = 0;
    + dec.def = 0;
    + dec.present = 1;
    + dec.mbz = 0;
    + dec.page_granularity = 0;
    + gdt[GDT_ENTRY_TSS] = encode_gdt_entry(&dec);
    +
    + return 1;
    +}
    +
    +void load_guest_gdt(struct lguest *lg, u32 table, u32 num)
    +{
    + if (num > GDT_ENTRIES)
    + kill_guest(lg, "too many gdt entries %i", num);
    +
    + lhread(lg, lg->state->gdt_table, table,
    + num * sizeof(lg->state->gdt_table[0]));
    + if (!fixup_gdt_table(lg->state->gdt_table, num,
    + &lg->state->regs, &lg->state->tss))
    + kill_guest(lg, "bad gdt table");
    +}
    +
    +/* We don't care about limit here, since we only let them use these in
    + * usermode (where lack of USER bit in pagetable protects hypervisor mem).
    + * However, we want to ensure it doesn't fault when loaded, since *we* are
    + * the ones who will load it in switch_to_guest.
    + */
    +void guest_load_tls(struct lguest *lg, const struct desc_struct __user *gtls)
    +{
    + unsigned int i;
    + struct desc_struct *tls = &lg->state->gdt_table[GDT_ENTRY_TLS_MIN];
    +
    + lhread(lg, tls, (u32)gtls, sizeof(*tls)*GDT_ENTRY_TLS_ENTRIES);
    + for (i = 0; i < ARRAY_SIZE(lg->tls_limits); i++) {
    + struct decoded_gdt_entry dec = decode_gdt_entry(&tls[i]);
    +
    + if (!dec.present)
    + continue;
    +
    + /* We truncate to one byte/page (depending on G bit) to neuter
    + it, so ensure it's more than 1 page below trap page. */
    + tls[i].a &= 0xFFFF0000;
    + lg->tls_limits[i] = dec.limit;
    + if (!check_desc(&dec) || dec.base > HYPE_ADDR - PAGE_SIZE)
    + kill_guest(lg, "bad TLS descriptor %i", i);
    + }
    + check_live_segments(lg->state->gdt_table, &lg->state->regs);
    +}

    -
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