Example #1
0
/*H:040
 * This is the i386-specific code to setup and run the Guest.  Interrupts
 * are disabled: we own the CPU.
 */
void lguest_arch_run_guest(struct lg_cpu *cpu)
{
	/*
	 * Remember the awfully-named TS bit?  If the Guest has asked to set it
	 * we set it now, so we can trap and pass that trap to the Guest if it
	 * uses the FPU.
	 */
	if (cpu->ts && user_has_fpu())
		stts();

	/*
	 * SYSENTER is an optimized way of doing system calls.  We can't allow
	 * it because it always jumps to privilege level 0.  A normal Guest
	 * won't try it because we don't advertise it in CPUID, but a malicious
	 * Guest (or malicious Guest userspace program) could, so we tell the
	 * CPU to disable it before running the Guest.
	 */
	if (boot_cpu_has(X86_FEATURE_SEP))
		wrmsr(MSR_IA32_SYSENTER_CS, 0, 0);

	/*
	 * Now we actually run the Guest.  It will return when something
	 * interesting happens, and we can examine its registers to see what it
	 * was doing.
	 */
	run_guest_once(cpu, lguest_pages(raw_smp_processor_id()));

	/*
	 * Note that the "regs" structure contains two extra entries which are
	 * not really registers: a trap number which says what interrupt or
	 * trap made the switcher code come back, and an error code which some
	 * traps set.
	 */

	 /* Restore SYSENTER if it's supposed to be on. */
	 if (boot_cpu_has(X86_FEATURE_SEP))
		wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);

	/* Clear the host TS bit if it was set above. */
	if (cpu->ts && user_has_fpu())
		clts();

	/*
	 * If the Guest page faulted, then the cr2 register will tell us the
	 * bad virtual address.  We have to grab this now, because once we
	 * re-enable interrupts an interrupt could fault and thus overwrite
	 * cr2, or we could even move off to a different CPU.
	 */
	if (cpu->regs->trapnum == 14)
		cpu->arch.last_pagefault = read_cr2();
	/*
	 * Similarly, if we took a trap because the Guest used the FPU,
	 * we have to restore the FPU it expects to see.
	 * math_state_restore() may sleep and we may even move off to
	 * a different CPU. So all the critical stuff should be done
	 * before this.
	 */
	else if (cpu->regs->trapnum == 7 && !user_has_fpu())
		math_state_restore();
}
void __init lguest_arch_host_init(void)
{
	int i;

	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;

		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.sp0 = (long)(&pages->regs + 1);
		state->guest_tss.ss0 = LGUEST_DS;

		state->guest_tss.io_bitmap_base = sizeof(state->guest_tss);

		setup_default_gdt_entries(state);
		
		setup_default_idt_entries(state, default_idt_entries);

		get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
		get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
	}

	lguest_entry.offset = (long)switch_to_guest + switcher_offset();
	lguest_entry.segment = LGUEST_CS;


	get_online_cpus();
	if (cpu_has_pge) { 
		
		cpu_had_pge = 1;
		on_each_cpu(adjust_pge, (void *)0, 1);
		
		clear_cpu_cap(&boot_cpu_data, X86_FEATURE_PGE);
	}
	put_online_cpus();
}
void lguest_arch_run_guest(struct lg_cpu *cpu)
{
	if (cpu->ts)
		unlazy_fpu(current);

	if (boot_cpu_has(X86_FEATURE_SEP))
		wrmsr(MSR_IA32_SYSENTER_CS, 0, 0);

	run_guest_once(cpu, lguest_pages(raw_smp_processor_id()));


	 
	 if (boot_cpu_has(X86_FEATURE_SEP))
		wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);

	if (cpu->regs->trapnum == 14)
		cpu->arch.last_pagefault = read_cr2();
	else if (cpu->regs->trapnum == 7)
		math_state_restore();
}
Example #4
0
/*H:020
 * Now the Switcher is mapped and every thing else is ready, we need to do
 * some more i386-specific initialization.
 */
void __init lguest_arch_host_init(void)
{
	int i;

	/*
	 * Most of the x86/switcher_32.S doesn't care that it's been moved; on
	 * Intel, jumps are relative, and it doesn't access any references to
	 * external code or data.
	 *
	 * The only exception is the interrupt handlers in switcher.S: their
	 * addresses are placed in a table (default_idt_entries), so we need to
	 * update the table with the new addresses.  switcher_offset() is a
	 * convenience function which returns the distance between the
	 * compiled-in switcher code and the high-mapped copy we just made.
	 */
	for (i = 0; i < IDT_ENTRIES; i++)
		default_idt_entries[i] += switcher_offset();

	/*
	 * Set up the Switcher's per-cpu areas.
	 *
	 * Each CPU gets two pages of its own within the high-mapped region
	 * (aka. "struct lguest_pages").  Much of this can be initialized now,
	 * but some depends on what Guest we are running (which is set up in
	 * copy_in_guest_info()).
	 */
	for_each_possible_cpu(i) {
		/* lguest_pages() returns this CPU's two pages. */
		struct lguest_pages *pages = lguest_pages(i);
		/* This is a convenience pointer to make the code neater. */
		struct lguest_ro_state *state = &pages->state;

		/*
		 * The Global Descriptor Table: the Host has a different one
		 * for each CPU.  We keep a descriptor for the GDT which says
		 * where it is and how big it is (the size is actually the last
		 * byte, not the size, hence the "-1").
		 */
		state->host_gdt_desc.size = GDT_SIZE-1;
		state->host_gdt_desc.address = (long)get_cpu_gdt_table(i);

		/*
		 * All CPUs on the Host use the same Interrupt Descriptor
		 * Table, so we just use store_idt(), which gets this CPU's IDT
		 * descriptor.
		 */
		store_idt(&state->host_idt_desc);

		/*
		 * The descriptors for the Guest's GDT and IDT can be filled
		 * out now, too.  We copy the GDT & IDT into ->guest_gdt and
		 * ->guest_idt before actually running the Guest.
		 */
		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;

		/*
		 * We know where we want the stack to be when the Guest enters
		 * the Switcher: in pages->regs.  The stack grows upwards, so
		 * we start it at the end of that structure.
		 */
		state->guest_tss.sp0 = (long)(&pages->regs + 1);
		/*
		 * And this is the GDT entry to use for the stack: we keep a
		 * couple of special LGUEST entries.
		 */
		state->guest_tss.ss0 = LGUEST_DS;

		/*
		 * x86 can have a finegrained bitmap which indicates what I/O
		 * ports the process can use.  We set it to the end of our
		 * structure, meaning "none".
		 */
		state->guest_tss.io_bitmap_base = sizeof(state->guest_tss);

		/*
		 * Some GDT entries are the same across all Guests, so we can
		 * set them up now.
		 */
		setup_default_gdt_entries(state);
		/* Most IDT entries are the same for all Guests, too.*/
		setup_default_idt_entries(state, default_idt_entries);

		/*
		 * The Host needs to be able to use the LGUEST segments on this
		 * CPU, too, so put them in the Host GDT.
		 */
		get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
		get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
	}

	/*
	 * In the Switcher, we want the %cs segment register to use the
	 * LGUEST_CS GDT entry: we've put that in the Host and Guest GDTs, so
	 * it will be undisturbed when we switch.  To change %cs and jump we
	 * need this structure to feed to Intel's "lcall" instruction.
	 */
	lguest_entry.offset = (long)switch_to_guest + switcher_offset();
	lguest_entry.segment = LGUEST_CS;

	/*
	 * Finally, we need to turn off "Page Global Enable".  PGE is an
	 * optimization where page table entries are specially marked to show
	 * they never change.  The Host kernel marks all the kernel pages this
	 * way because it's always present, even when userspace is running.
	 *
	 * Lguest breaks this: unbeknownst to the rest of the Host kernel, we
	 * switch to the Guest kernel.  If you don't disable this on all CPUs,
	 * you'll get really weird bugs that you'll chase for two days.
	 *
	 * I used to turn PGE off every time we switched to the Guest and back
	 * on when we return, but that slowed the Switcher down noticibly.
	 */

	/*
	 * We don't need the complexity of CPUs coming and going while we're
	 * doing this.
	 */
	get_online_cpus();
	if (boot_cpu_has(X86_FEATURE_PGE)) { /* We have a broader idea of "global". */
		/* Remember that this was originally set (for cleanup). */
		cpu_had_pge = 1;
		/*
		 * adjust_pge is a helper function which sets or unsets the PGE
		 * bit on its CPU, depending on the argument (0 == unset).
		 */
		on_each_cpu(adjust_pge, (void *)0, 1);
		/* Turn off the feature in the global feature set. */
		clear_cpu_cap(&boot_cpu_data, X86_FEATURE_PGE);
	}
	put_online_cpus();
}