diff options
Diffstat (limited to 'drivers/lguest/core.c')
| -rw-r--r-- | drivers/lguest/core.c | 462 |
1 files changed, 462 insertions, 0 deletions
diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c new file mode 100644 index 0000000..ce909ec --- /dev/null +++ b/drivers/lguest/core.c @@ -0,0 +1,462 @@ +/* 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/paravirt.h> +#include <asm/desc.h> +#include <asm/pgtable.h> +#include <asm/uaccess.h> +#include <asm/poll.h> +#include <asm/highmem.h> +#include <asm/asm-offsets.h> +#include <asm/i387.h> +#include "lg.h" + +/* Found in switcher.S */ +extern char start_switcher_text[], end_switcher_text[], switch_to_guest[]; +extern unsigned long default_idt_entries[]; + +/* Every guest maps the core switcher code. */ +#define SHARED_SWITCHER_PAGES \ + DIV_ROUND_UP(end_switcher_text - start_switcher_text, PAGE_SIZE) +/* Pages for switcher itself, then two pages per cpu */ +#define TOTAL_SWITCHER_PAGES (SHARED_SWITCHER_PAGES + 2 * NR_CPUS) + +/* We map at -4M for ease of mapping into the guest (one PTE page). */ +#define SWITCHER_ADDR 0xFFC00000 + +static struct vm_struct *switcher_vma; +static struct page **switcher_page; + +static int cpu_had_pge; +static struct { + unsigned long offset; + unsigned short segment; +} lguest_entry; + +/* This One Big lock protects all inter-guest data structures. */ +DEFINE_MUTEX(lguest_lock); +static DEFINE_PER_CPU(struct lguest *, last_guest); + +/* FIXME: Make dynamic. */ +#define MAX_LGUEST_GUESTS 16 +struct lguest lguests[MAX_LGUEST_GUESTS]; + +/* Offset from where switcher.S was compiled to where we've copied it */ +static unsigned long switcher_offset(void) +{ + return SWITCHER_ADDR - (unsigned long)start_switcher_text; +} + +/* This cpu's struct lguest_pages. */ +static struct lguest_pages *lguest_pages(unsigned int cpu) +{ + return &(((struct lguest_pages *) + (SWITCHER_ADDR + SHARED_SWITCHER_PAGES*PAGE_SIZE))[cpu]); +} + +static __init int map_switcher(void) +{ + int i, err; + struct page **pagep; + + switcher_page = kmalloc(sizeof(switcher_page[0])*TOTAL_SWITCHER_PAGES, + GFP_KERNEL); + if (!switcher_page) { + err = -ENOMEM; + goto out; + } + + for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) { + unsigned long addr = get_zeroed_page(GFP_KERNEL); + if (!addr) { + err = -ENOMEM; + goto free_some_pages; + } + switcher_page[i] = virt_to_page(addr); + } + + switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE, + VM_ALLOC, SWITCHER_ADDR, VMALLOC_END); + if (!switcher_vma) { + err = -ENOMEM; + printk("lguest: could not map switcher pages high\n"); + goto free_pages; + } + + pagep = switcher_page; + err = map_vm_area(switcher_vma, PAGE_KERNEL, &pagep); + if (err) { + printk("lguest: map_vm_area failed: %i\n", err); + goto free_vma; + } + memcpy(switcher_vma->addr, start_switcher_text, + end_switcher_text - start_switcher_text); + + /* Fix up IDT entries to point into copied text. */ + for (i = 0; i < IDT_ENTRIES; i++) + default_idt_entries[i] += switcher_offset(); + + for_each_possible_cpu(i) { + struct lguest_pages *pages = lguest_pages(i); + struct lguest_ro_state *state = &pages->state; + + /* These fields are static: rest done in copy_in_guest_info */ + state->host_gdt_desc.size = GDT_SIZE-1; + state->host_gdt_desc.address = (long)get_cpu_gdt_table(i); + store_idt(&state->host_idt_desc); + state->guest_idt_desc.size = sizeof(state->guest_idt)-1; + state->guest_idt_desc.address = (long)&state->guest_idt; + state->guest_gdt_desc.size = sizeof(state->guest_gdt)-1; + state->guest_gdt_desc.address = (long)&state->guest_gdt; + state->guest_tss.esp0 = (long)(&pages->regs + 1); + state->guest_tss.ss0 = LGUEST_DS; + /* No I/O for you! */ + state->guest_tss.io_bitmap_base = sizeof(state->guest_tss); + setup_default_gdt_entries(state); + setup_default_idt_entries(state, default_idt_entries); + + /* Setup LGUEST segments on all cpus */ + get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT; + get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT; + } + + /* Initialize entry point into switcher. */ + lguest_entry.offset = (long)switch_to_guest + switcher_offset(); + lguest_entry.segment = LGUEST_CS; + + printk(KERN_INFO "lguest: mapped switcher at %p\n", + switcher_vma->addr); + return 0; + +free_vma: + vunmap(switcher_vma->addr); +free_pages: + i = TOTAL_SWITCHER_PAGES; +free_some_pages: + for (--i; i >= 0; i--) + __free_pages(switcher_page[i], 0); + kfree(switcher_page); +out: + return err; +} + +static void unmap_switcher(void) +{ + unsigned int i; + + vunmap(switcher_vma->addr); + for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) + __free_pages(switcher_page[i], 0); +} + +/* IN/OUT insns: enough to get us past boot-time probing. */ +static int emulate_insn(struct lguest *lg) +{ + u8 insn; + unsigned int insnlen = 0, in = 0, shift = 0; + unsigned long physaddr = guest_pa(lg, lg->regs->eip); + + /* This only works for addresses in linear mapping... */ + if (lg->regs->eip < lg->page_offset) + return 0; + lgread(lg, &insn, physaddr, 1); + + /* Operand size prefix means it's actually for ax. */ + if (insn == 0x66) { + shift = 16; + insnlen = 1; + lgread(lg, &insn, physaddr + insnlen, 1); + } + + switch (insn & 0xFE) { + case 0xE4: /* in <next byte>,%al */ + insnlen += 2; + in = 1; + break; + case 0xEC: /* in (%dx),%al */ + insnlen += 1; + in = 1; + break; + case 0xE6: /* out %al,<next byte> */ + insnlen += 2; + break; + case 0xEE: /* out %al,(%dx) */ + insnlen += 1; + break; + default: + return 0; + } + + if (in) { + /* Lower bit tells is whether it's a 16 or 32 bit access */ + if (insn & 0x1) + lg->regs->eax = 0xFFFFFFFF; + else + lg->regs->eax |= (0xFFFF << shift); + } + lg->regs->eip += insnlen; + return 1; +} + +int lguest_address_ok(const struct lguest *lg, + unsigned long addr, unsigned long len) +{ + return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr); +} + +/* Just like get_user, but don't let guest access lguest binary. */ +u32 lgread_u32(struct lguest *lg, unsigned long addr) +{ + u32 val = 0; + + /* Don't let them access lguest binary */ + if (!lguest_address_ok(lg, addr, sizeof(val)) + || get_user(val, (u32 __user *)addr) != 0) + kill_guest(lg, "bad read address %#lx", addr); + return val; +} + +void lgwrite_u32(struct lguest *lg, unsigned long addr, u32 val) +{ + if (!lguest_address_ok(lg, addr, sizeof(val)) + || put_user(val, (u32 __user *)addr) != 0) + kill_guest(lg, "bad write address %#lx", addr); +} + +void lgread(struct lguest *lg, void *b, unsigned long addr, unsigned bytes) +{ + if (!lguest_address_ok(lg, addr, bytes) + || copy_from_user(b, (void __user *)addr, bytes) != 0) { + /* copy_from_user should do this, but as we rely on it... */ + memset(b, 0, bytes); + kill_guest(lg, "bad read address %#lx len %u", addr, bytes); + } +} + +void lgwrite(struct lguest *lg, unsigned long addr, const void *b, + unsigned bytes) +{ + if (!lguest_address_ok(lg, addr, bytes) + || copy_to_user((void __user *)addr, b, bytes) != 0) + kill_guest(lg, "bad write address %#lx len %u", addr, bytes); +} + +static void set_ts(void) +{ + u32 cr0; + + cr0 = read_cr0(); + if (!(cr0 & 8)) + write_cr0(cr0|8); +} + +static void copy_in_guest_info(struct lguest *lg, struct lguest_pages *pages) +{ + if (__get_cpu_var(last_guest) != lg || lg->last_pages != pages) { + __get_cpu_var(last_guest) = lg; + lg->last_pages = pages; + lg->changed = CHANGED_ALL; + } + + /* These are pretty cheap, so we do them unconditionally. */ + pages->state.host_cr3 = __pa(current->mm->pgd); + map_switcher_in_guest(lg, pages); + pages->state.guest_tss.esp1 = lg->esp1; + pages->state.guest_tss.ss1 = lg->ss1; + + /* Copy direct trap entries. */ + if (lg->changed & CHANGED_IDT) + copy_traps(lg, pages->state.guest_idt, default_idt_entries); + + /* Copy all GDT entries but the TSS. */ + if (lg->changed & CHANGED_GDT) + copy_gdt(lg, pages->state.guest_gdt); + /* If only the TLS entries have changed, copy them. */ + else if (lg->changed & CHANGED_GDT_TLS) + copy_gdt_tls(lg, pages->state.guest_gdt); + + lg->changed = 0; +} + +static void run_guest_once(struct lguest *lg, struct lguest_pages *pages) +{ + unsigned int clobber; + + copy_in_guest_info(lg, pages); + + /* Put eflags on stack, lcall does rest: suitable for iret return. */ + asm volatile("pushf; lcall *lguest_entry" + : "=a"(clobber), "=b"(clobber) + : "0"(pages), "1"(__pa(lg->pgdirs[lg->pgdidx].pgdir)) + : "memory", "%edx", "%ecx", "%edi", "%esi"); +} + +int run_guest(struct lguest *lg, unsigned long __user *user) +{ + while (!lg->dead) { + unsigned int cr2 = 0; /* Damn gcc */ + + /* Hypercalls first: we might have been out to userspace */ + do_hypercalls(lg); + if (lg->dma_is_pending) { + if (put_user(lg->pending_dma, user) || + put_user(lg->pending_key, user+1)) + return -EFAULT; + return sizeof(unsigned long)*2; + } + + if (signal_pending(current)) + return -ERESTARTSYS; + + /* If Waker set break_out, return to Launcher. */ + if (lg->break_out) + return -EAGAIN; + + maybe_do_interrupt(lg); + + try_to_freeze(); + + if (lg->dead) + break; + + if (lg->halted) { + set_current_state(TASK_INTERRUPTIBLE); + schedule(); + continue; + } + + local_irq_disable(); + + /* Even if *we* don't want FPU trap, guest might... */ + if (lg->ts) + set_ts(); + + /* Don't let Guest do SYSENTER: we can't handle it. */ + if (boot_cpu_has(X86_FEATURE_SEP)) + wrmsr(MSR_IA32_SYSENTER_CS, 0, 0); + + run_guest_once(lg, lguest_pages(raw_smp_processor_id())); + + /* Save cr2 now if we page-faulted. */ + if (lg->regs->trapnum == 14) + cr2 = read_cr2(); + else if (lg->regs->trapnum == 7) + math_state_restore(); + + if (boot_cpu_has(X86_FEATURE_SEP)) + wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0); + local_irq_enable(); + + switch (lg->regs->trapnum) { + case 13: /* We've intercepted a GPF. */ + if (lg->regs->errcode == 0) { + if (emulate_insn(lg)) + continue; + } + break; + case 14: /* We've intercepted a page fault. */ + if (demand_page(lg, cr2, lg->regs->errcode)) + continue; + + /* If lguest_data is NULL, this won't hurt. */ + if (put_user(cr2, &lg->lguest_data->cr2)) + kill_guest(lg, "Writing cr2"); + break; + case 7: /* We've intercepted a Device Not Available fault. */ + /* If they don't want to know, just absorb it. */ + if (!lg->ts) + continue; + break; + case 32 ... 255: /* Real interrupt, fall thru */ + cond_resched(); + case LGUEST_TRAP_ENTRY: /* Handled at top of loop */ + continue; + } + + if (deliver_trap(lg, lg->regs->trapnum)) + continue; + + kill_guest(lg, "unhandled trap %li at %#lx (%#lx)", + lg->regs->trapnum, lg->regs->eip, + lg->regs->trapnum == 14 ? cr2 : lg->regs->errcode); + } + return -ENOENT; +} + +int find_free_guest(void) +{ + unsigned int i; + for (i = 0; i < MAX_LGUEST_GUESTS; i++) + if (!lguests[i].tsk) + return i; + return -1; +} + +static void adjust_pge(void *on) +{ + if (on) + write_cr4(read_cr4() | X86_CR4_PGE); + else + write_cr4(read_cr4() & ~X86_CR4_PGE); +} + +static int __init init(void) +{ + int err; + + if (paravirt_enabled()) { + printk("lguest is afraid of %s\n", paravirt_ops.name); + return -EPERM; + } + + err = map_switcher(); + if (err) + return err; + + err = init_pagetables(switcher_page, SHARED_SWITCHER_PAGES); + if (err) { + unmap_switcher(); + return err; + } + lguest_io_init(); + + err = lguest_device_init(); + if (err) { + free_pagetables(); + unmap_switcher(); + return err; + } + lock_cpu_hotplug(); + if (cpu_has_pge) { /* We have a broader idea of "global". */ + cpu_had_pge = 1; + on_each_cpu(adjust_pge, (void *)0, 0, 1); + clear_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability); + } + unlock_cpu_hotplug(); + return 0; +} + +static void __exit fini(void) +{ + lguest_device_remove(); + free_pagetables(); + unmap_switcher(); + lock_cpu_hotplug(); + if (cpu_had_pge) { + set_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability); + on_each_cpu(adjust_pge, (void *)1, 0, 1); + } + unlock_cpu_hotplug(); +} + +module_init(init); +module_exit(fini); +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>"); |
