![Rusty Russell](/assets/img/avatar_default.png)
Documentation: The Launcher Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
486 lines
13 KiB
C
486 lines
13 KiB
C
/*P:400 This contains run_guest() which actually calls into the Host<->Guest
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* Switcher and analyzes the return, such as determining if the Guest wants the
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* Host to do something. This file also contains useful helper routines, and a
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* couple of non-obvious setup and teardown pieces which were implemented after
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* days of debugging pain. :*/
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#include <linux/module.h>
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#include <linux/stringify.h>
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#include <linux/stddef.h>
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#include <linux/io.h>
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#include <linux/mm.h>
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#include <linux/vmalloc.h>
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#include <linux/cpu.h>
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#include <linux/freezer.h>
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#include <asm/paravirt.h>
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#include <asm/desc.h>
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#include <asm/pgtable.h>
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#include <asm/uaccess.h>
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#include <asm/poll.h>
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#include <asm/highmem.h>
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#include <asm/asm-offsets.h>
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#include <asm/i387.h>
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#include "lg.h"
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/* Found in switcher.S */
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extern char start_switcher_text[], end_switcher_text[], switch_to_guest[];
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extern unsigned long default_idt_entries[];
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/* Every guest maps the core switcher code. */
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#define SHARED_SWITCHER_PAGES \
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DIV_ROUND_UP(end_switcher_text - start_switcher_text, PAGE_SIZE)
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/* Pages for switcher itself, then two pages per cpu */
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#define TOTAL_SWITCHER_PAGES (SHARED_SWITCHER_PAGES + 2 * NR_CPUS)
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/* We map at -4M for ease of mapping into the guest (one PTE page). */
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#define SWITCHER_ADDR 0xFFC00000
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static struct vm_struct *switcher_vma;
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static struct page **switcher_page;
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static int cpu_had_pge;
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static struct {
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unsigned long offset;
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unsigned short segment;
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} lguest_entry;
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/* This One Big lock protects all inter-guest data structures. */
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DEFINE_MUTEX(lguest_lock);
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static DEFINE_PER_CPU(struct lguest *, last_guest);
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/* FIXME: Make dynamic. */
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#define MAX_LGUEST_GUESTS 16
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struct lguest lguests[MAX_LGUEST_GUESTS];
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/* Offset from where switcher.S was compiled to where we've copied it */
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static unsigned long switcher_offset(void)
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{
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return SWITCHER_ADDR - (unsigned long)start_switcher_text;
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}
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/* This cpu's struct lguest_pages. */
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static struct lguest_pages *lguest_pages(unsigned int cpu)
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{
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return &(((struct lguest_pages *)
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(SWITCHER_ADDR + SHARED_SWITCHER_PAGES*PAGE_SIZE))[cpu]);
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}
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static __init int map_switcher(void)
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{
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int i, err;
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struct page **pagep;
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switcher_page = kmalloc(sizeof(switcher_page[0])*TOTAL_SWITCHER_PAGES,
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GFP_KERNEL);
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if (!switcher_page) {
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err = -ENOMEM;
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goto out;
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}
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for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) {
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unsigned long addr = get_zeroed_page(GFP_KERNEL);
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if (!addr) {
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err = -ENOMEM;
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goto free_some_pages;
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}
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switcher_page[i] = virt_to_page(addr);
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}
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switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE,
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VM_ALLOC, SWITCHER_ADDR, VMALLOC_END);
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if (!switcher_vma) {
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err = -ENOMEM;
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printk("lguest: could not map switcher pages high\n");
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goto free_pages;
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}
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pagep = switcher_page;
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err = map_vm_area(switcher_vma, PAGE_KERNEL, &pagep);
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if (err) {
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printk("lguest: map_vm_area failed: %i\n", err);
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goto free_vma;
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}
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memcpy(switcher_vma->addr, start_switcher_text,
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end_switcher_text - start_switcher_text);
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/* Fix up IDT entries to point into copied text. */
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for (i = 0; i < IDT_ENTRIES; i++)
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default_idt_entries[i] += switcher_offset();
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for_each_possible_cpu(i) {
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struct lguest_pages *pages = lguest_pages(i);
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struct lguest_ro_state *state = &pages->state;
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/* These fields are static: rest done in copy_in_guest_info */
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state->host_gdt_desc.size = GDT_SIZE-1;
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state->host_gdt_desc.address = (long)get_cpu_gdt_table(i);
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store_idt(&state->host_idt_desc);
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state->guest_idt_desc.size = sizeof(state->guest_idt)-1;
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state->guest_idt_desc.address = (long)&state->guest_idt;
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state->guest_gdt_desc.size = sizeof(state->guest_gdt)-1;
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state->guest_gdt_desc.address = (long)&state->guest_gdt;
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state->guest_tss.esp0 = (long)(&pages->regs + 1);
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state->guest_tss.ss0 = LGUEST_DS;
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/* No I/O for you! */
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state->guest_tss.io_bitmap_base = sizeof(state->guest_tss);
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setup_default_gdt_entries(state);
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setup_default_idt_entries(state, default_idt_entries);
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/* Setup LGUEST segments on all cpus */
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get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
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get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
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}
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/* Initialize entry point into switcher. */
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lguest_entry.offset = (long)switch_to_guest + switcher_offset();
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lguest_entry.segment = LGUEST_CS;
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printk(KERN_INFO "lguest: mapped switcher at %p\n",
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switcher_vma->addr);
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return 0;
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free_vma:
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vunmap(switcher_vma->addr);
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free_pages:
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i = TOTAL_SWITCHER_PAGES;
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free_some_pages:
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for (--i; i >= 0; i--)
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__free_pages(switcher_page[i], 0);
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kfree(switcher_page);
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out:
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return err;
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}
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static void unmap_switcher(void)
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{
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unsigned int i;
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vunmap(switcher_vma->addr);
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for (i = 0; i < TOTAL_SWITCHER_PAGES; i++)
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__free_pages(switcher_page[i], 0);
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}
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/* IN/OUT insns: enough to get us past boot-time probing. */
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static int emulate_insn(struct lguest *lg)
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{
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u8 insn;
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unsigned int insnlen = 0, in = 0, shift = 0;
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unsigned long physaddr = guest_pa(lg, lg->regs->eip);
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/* This only works for addresses in linear mapping... */
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if (lg->regs->eip < lg->page_offset)
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return 0;
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lgread(lg, &insn, physaddr, 1);
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/* Operand size prefix means it's actually for ax. */
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if (insn == 0x66) {
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shift = 16;
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insnlen = 1;
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lgread(lg, &insn, physaddr + insnlen, 1);
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}
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switch (insn & 0xFE) {
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case 0xE4: /* in <next byte>,%al */
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insnlen += 2;
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in = 1;
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break;
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case 0xEC: /* in (%dx),%al */
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insnlen += 1;
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in = 1;
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break;
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case 0xE6: /* out %al,<next byte> */
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insnlen += 2;
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break;
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case 0xEE: /* out %al,(%dx) */
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insnlen += 1;
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break;
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default:
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return 0;
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}
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if (in) {
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/* Lower bit tells is whether it's a 16 or 32 bit access */
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if (insn & 0x1)
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lg->regs->eax = 0xFFFFFFFF;
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else
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lg->regs->eax |= (0xFFFF << shift);
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}
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lg->regs->eip += insnlen;
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return 1;
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}
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/*L:305
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* Dealing With Guest Memory.
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*
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* When the Guest gives us (what it thinks is) a physical address, we can use
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* the normal copy_from_user() & copy_to_user() on that address: remember,
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* Guest physical == Launcher virtual.
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*
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* But we can't trust the Guest: it might be trying to access the Launcher
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* code. We have to check that the range is below the pfn_limit the Launcher
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* gave us. We have to make sure that addr + len doesn't give us a false
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* positive by overflowing, too. */
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int lguest_address_ok(const struct lguest *lg,
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unsigned long addr, unsigned long len)
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{
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return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr);
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}
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/* This is a convenient routine to get a 32-bit value from the Guest (a very
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* common operation). Here we can see how useful the kill_lguest() routine we
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* met in the Launcher can be: we return a random value (0) instead of needing
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* to return an error. */
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u32 lgread_u32(struct lguest *lg, unsigned long addr)
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{
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u32 val = 0;
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/* Don't let them access lguest binary. */
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if (!lguest_address_ok(lg, addr, sizeof(val))
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|| get_user(val, (u32 __user *)addr) != 0)
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kill_guest(lg, "bad read address %#lx", addr);
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return val;
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}
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/* Same thing for writing a value. */
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void lgwrite_u32(struct lguest *lg, unsigned long addr, u32 val)
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{
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if (!lguest_address_ok(lg, addr, sizeof(val))
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|| put_user(val, (u32 __user *)addr) != 0)
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kill_guest(lg, "bad write address %#lx", addr);
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}
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/* This routine is more generic, and copies a range of Guest bytes into a
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* buffer. If the copy_from_user() fails, we fill the buffer with zeroes, so
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* the caller doesn't end up using uninitialized kernel memory. */
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void lgread(struct lguest *lg, void *b, unsigned long addr, unsigned bytes)
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{
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if (!lguest_address_ok(lg, addr, bytes)
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|| copy_from_user(b, (void __user *)addr, bytes) != 0) {
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/* copy_from_user should do this, but as we rely on it... */
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memset(b, 0, bytes);
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kill_guest(lg, "bad read address %#lx len %u", addr, bytes);
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}
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}
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/* Similarly, our generic routine to copy into a range of Guest bytes. */
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void lgwrite(struct lguest *lg, unsigned long addr, const void *b,
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unsigned bytes)
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{
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if (!lguest_address_ok(lg, addr, bytes)
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|| copy_to_user((void __user *)addr, b, bytes) != 0)
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kill_guest(lg, "bad write address %#lx len %u", addr, bytes);
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}
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/* (end of memory access helper routines) :*/
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static void set_ts(void)
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{
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u32 cr0;
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cr0 = read_cr0();
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if (!(cr0 & 8))
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write_cr0(cr0|8);
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}
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static void copy_in_guest_info(struct lguest *lg, struct lguest_pages *pages)
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{
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if (__get_cpu_var(last_guest) != lg || lg->last_pages != pages) {
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__get_cpu_var(last_guest) = lg;
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lg->last_pages = pages;
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lg->changed = CHANGED_ALL;
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}
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/* These are pretty cheap, so we do them unconditionally. */
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pages->state.host_cr3 = __pa(current->mm->pgd);
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map_switcher_in_guest(lg, pages);
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pages->state.guest_tss.esp1 = lg->esp1;
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pages->state.guest_tss.ss1 = lg->ss1;
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/* Copy direct trap entries. */
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if (lg->changed & CHANGED_IDT)
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copy_traps(lg, pages->state.guest_idt, default_idt_entries);
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/* Copy all GDT entries but the TSS. */
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if (lg->changed & CHANGED_GDT)
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copy_gdt(lg, pages->state.guest_gdt);
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/* If only the TLS entries have changed, copy them. */
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else if (lg->changed & CHANGED_GDT_TLS)
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copy_gdt_tls(lg, pages->state.guest_gdt);
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lg->changed = 0;
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}
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static void run_guest_once(struct lguest *lg, struct lguest_pages *pages)
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{
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unsigned int clobber;
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copy_in_guest_info(lg, pages);
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/* Put eflags on stack, lcall does rest: suitable for iret return. */
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asm volatile("pushf; lcall *lguest_entry"
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: "=a"(clobber), "=b"(clobber)
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: "0"(pages), "1"(__pa(lg->pgdirs[lg->pgdidx].pgdir))
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: "memory", "%edx", "%ecx", "%edi", "%esi");
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}
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int run_guest(struct lguest *lg, unsigned long __user *user)
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{
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while (!lg->dead) {
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unsigned int cr2 = 0; /* Damn gcc */
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/* Hypercalls first: we might have been out to userspace */
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do_hypercalls(lg);
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if (lg->dma_is_pending) {
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if (put_user(lg->pending_dma, user) ||
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put_user(lg->pending_key, user+1))
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return -EFAULT;
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return sizeof(unsigned long)*2;
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}
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if (signal_pending(current))
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return -ERESTARTSYS;
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/* If Waker set break_out, return to Launcher. */
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if (lg->break_out)
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return -EAGAIN;
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maybe_do_interrupt(lg);
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try_to_freeze();
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if (lg->dead)
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break;
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if (lg->halted) {
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set_current_state(TASK_INTERRUPTIBLE);
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schedule();
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continue;
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}
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local_irq_disable();
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/* Even if *we* don't want FPU trap, guest might... */
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if (lg->ts)
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set_ts();
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/* Don't let Guest do SYSENTER: we can't handle it. */
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if (boot_cpu_has(X86_FEATURE_SEP))
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wrmsr(MSR_IA32_SYSENTER_CS, 0, 0);
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run_guest_once(lg, lguest_pages(raw_smp_processor_id()));
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/* Save cr2 now if we page-faulted. */
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if (lg->regs->trapnum == 14)
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cr2 = read_cr2();
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else if (lg->regs->trapnum == 7)
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math_state_restore();
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if (boot_cpu_has(X86_FEATURE_SEP))
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wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
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local_irq_enable();
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switch (lg->regs->trapnum) {
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case 13: /* We've intercepted a GPF. */
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if (lg->regs->errcode == 0) {
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if (emulate_insn(lg))
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continue;
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}
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break;
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case 14: /* We've intercepted a page fault. */
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if (demand_page(lg, cr2, lg->regs->errcode))
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continue;
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/* If lguest_data is NULL, this won't hurt. */
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if (put_user(cr2, &lg->lguest_data->cr2))
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kill_guest(lg, "Writing cr2");
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break;
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case 7: /* We've intercepted a Device Not Available fault. */
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/* If they don't want to know, just absorb it. */
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if (!lg->ts)
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continue;
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break;
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case 32 ... 255: /* Real interrupt, fall thru */
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cond_resched();
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case LGUEST_TRAP_ENTRY: /* Handled at top of loop */
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continue;
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}
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if (deliver_trap(lg, lg->regs->trapnum))
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continue;
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kill_guest(lg, "unhandled trap %li at %#lx (%#lx)",
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lg->regs->trapnum, lg->regs->eip,
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lg->regs->trapnum == 14 ? cr2 : lg->regs->errcode);
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}
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return -ENOENT;
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}
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int find_free_guest(void)
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{
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unsigned int i;
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for (i = 0; i < MAX_LGUEST_GUESTS; i++)
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if (!lguests[i].tsk)
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return i;
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return -1;
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}
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static void adjust_pge(void *on)
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{
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if (on)
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write_cr4(read_cr4() | X86_CR4_PGE);
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else
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write_cr4(read_cr4() & ~X86_CR4_PGE);
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}
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static int __init init(void)
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{
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int err;
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if (paravirt_enabled()) {
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printk("lguest is afraid of %s\n", paravirt_ops.name);
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return -EPERM;
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}
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err = map_switcher();
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if (err)
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return err;
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err = init_pagetables(switcher_page, SHARED_SWITCHER_PAGES);
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if (err) {
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unmap_switcher();
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return err;
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}
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lguest_io_init();
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err = lguest_device_init();
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if (err) {
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free_pagetables();
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unmap_switcher();
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return err;
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}
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lock_cpu_hotplug();
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if (cpu_has_pge) { /* We have a broader idea of "global". */
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cpu_had_pge = 1;
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on_each_cpu(adjust_pge, (void *)0, 0, 1);
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clear_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
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}
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unlock_cpu_hotplug();
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return 0;
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}
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static void __exit fini(void)
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{
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lguest_device_remove();
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free_pagetables();
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unmap_switcher();
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lock_cpu_hotplug();
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if (cpu_had_pge) {
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set_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
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on_each_cpu(adjust_pge, (void *)1, 0, 1);
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}
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unlock_cpu_hotplug();
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}
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module_init(init);
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module_exit(fini);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
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