538 lines
20 KiB
C
538 lines
20 KiB
C
/*
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* Copyright (C) 2006, Rusty Russell <rusty@rustcorp.com.au> IBM Corporation.
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* Copyright (C) 2007, Jes Sorensen <jes@sgi.com> SGI.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
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* NON INFRINGEMENT. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/kernel.h>
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#include <linux/start_kernel.h>
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#include <linux/string.h>
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#include <linux/console.h>
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#include <linux/screen_info.h>
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#include <linux/irq.h>
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#include <linux/interrupt.h>
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#include <linux/clocksource.h>
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#include <linux/clockchips.h>
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#include <linux/cpu.h>
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#include <linux/lguest.h>
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#include <linux/lguest_launcher.h>
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#include <linux/lguest_bus.h>
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#include <asm/paravirt.h>
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#include <asm/param.h>
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#include <asm/page.h>
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#include <asm/pgtable.h>
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#include <asm/desc.h>
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#include <asm/setup.h>
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#include <asm/lguest.h>
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#include <asm/uaccess.h>
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#include <asm/i387.h>
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#include "../lg.h"
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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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/* 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 DEFINE_PER_CPU(struct lguest *, last_guest);
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/*S:010
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* We are getting close to the Switcher.
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*
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* Remember that each CPU has two pages which are visible to the Guest when it
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* runs on that CPU. This has to contain the state for that Guest: we copy the
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* state in just before we run the Guest.
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*
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* Each Guest has "changed" flags which indicate what has changed in the Guest
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* since it last ran. We saw this set in interrupts_and_traps.c and
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* segments.c.
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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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/* Copying all this data can be quite expensive. We usually run the
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* same Guest we ran last time (and that Guest hasn't run anywhere else
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* meanwhile). If that's not the case, we pretend everything in the
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* Guest has changed. */
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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 copies are pretty cheap, so we do them unconditionally: */
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/* Save the current Host top-level page directory. */
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pages->state.host_cr3 = __pa(current->mm->pgd);
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/* Set up the Guest's page tables to see this CPU's pages (and no
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* other CPU's pages). */
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map_switcher_in_guest(lg, pages);
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/* Set up the two "TSS" members which tell the CPU what stack to use
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* for traps which do directly into the Guest (ie. traps at privilege
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* level 1). */
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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-to-Guest 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 which the Guest can change. */
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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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/* Mark the Guest as unchanged for next time. */
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lg->changed = 0;
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}
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/* Finally: the code to actually call into the Switcher to run the Guest. */
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static void run_guest_once(struct lguest *lg, struct lguest_pages *pages)
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{
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/* This is a dummy value we need for GCC's sake. */
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unsigned int clobber;
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/* Copy the guest-specific information into this CPU's "struct
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* lguest_pages". */
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copy_in_guest_info(lg, pages);
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/* Set the trap number to 256 (impossible value). If we fault while
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* switching to the Guest (bad segment registers or bug), this will
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* cause us to abort the Guest. */
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lg->regs->trapnum = 256;
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/* Now: we push the "eflags" register on the stack, then do an "lcall".
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* This is how we change from using the kernel code segment to using
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* the dedicated lguest code segment, as well as jumping into the
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* Switcher.
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*
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* The lcall also pushes the old code segment (KERNEL_CS) onto the
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* stack, then the address of this call. This stack layout happens to
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* exactly match the stack of an interrupt... */
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asm volatile("pushf; lcall *lguest_entry"
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/* This is how we tell GCC that %eax ("a") and %ebx ("b")
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* are changed by this routine. The "=" means output. */
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: "=a"(clobber), "=b"(clobber)
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/* %eax contains the pages pointer. ("0" refers to the
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* 0-th argument above, ie "a"). %ebx contains the
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* physical address of the Guest's top-level page
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* directory. */
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: "0"(pages), "1"(__pa(lg->pgdirs[lg->pgdidx].pgdir))
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/* We tell gcc that all these registers could change,
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* which means we don't have to save and restore them in
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* the Switcher. */
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: "memory", "%edx", "%ecx", "%edi", "%esi");
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}
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/*:*/
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/*H:040 This is the i386-specific code to setup and run the Guest. Interrupts
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* are disabled: we own the CPU. */
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void lguest_arch_run_guest(struct lguest *lg)
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{
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/* Remember the awfully-named TS bit? If the Guest has asked
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* to set it we set it now, so we can trap and pass that trap
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* to the Guest if it uses the FPU. */
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if (lg->ts)
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lguest_set_ts();
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/* SYSENTER is an optimized way of doing system calls. We
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* can't allow it because it always jumps to privilege level 0.
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* A normal Guest won't try it because we don't advertise it in
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* CPUID, but a malicious Guest (or malicious Guest userspace
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* program) could, so we tell the CPU to disable it before
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* running the Guest. */
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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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/* Now we actually run the Guest. It will pop back out when
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* something interesting happens, and we can examine its
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* registers to see what it was doing. */
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run_guest_once(lg, lguest_pages(raw_smp_processor_id()));
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/* The "regs" pointer contains two extra entries which are not
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* really registers: a trap number which says what interrupt or
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* trap made the switcher code come back, and an error code
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* which some traps set. */
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/* If the Guest page faulted, then the cr2 register will tell
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* us the bad virtual address. We have to grab this now,
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* because once we re-enable interrupts an interrupt could
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* fault and thus overwrite cr2, or we could even move off to a
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* different CPU. */
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if (lg->regs->trapnum == 14)
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lg->arch.last_pagefault = read_cr2();
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/* Similarly, if we took a trap because the Guest used the FPU,
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* we have to restore the FPU it expects to see. */
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else if (lg->regs->trapnum == 7)
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math_state_restore();
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/* Restore SYSENTER if it's supposed to be on. */
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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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}
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/*H:130 Our Guest is usually so well behaved; it never tries to do things it
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* isn't allowed to. Unfortunately, Linux's paravirtual infrastructure isn't
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* quite complete, because it doesn't contain replacements for the Intel I/O
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* instructions. As a result, the Guest sometimes fumbles across one during
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* the boot process as it probes for various things which are usually attached
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* to a PC.
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*
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* When the Guest uses one of these instructions, we get trap #13 (General
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* Protection Fault) and come here. We see if it's one of those troublesome
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* instructions and skip over it. We return true if we did. */
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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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/* The eip contains the *virtual* address of the Guest's instruction:
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* guest_pa just subtracts the Guest's page_offset. */
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unsigned long physaddr = guest_pa(lg, lg->regs->eip);
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/* The guest_pa() function only works for Guest kernel addresses, but
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* that's all we're trying to do anyway. */
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if (lg->regs->eip < lg->page_offset)
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return 0;
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/* Decoding x86 instructions is icky. */
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lgread(lg, &insn, physaddr, 1);
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/* 0x66 is an "operand prefix". It means it's using the upper 16 bits
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of the eax register. */
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if (insn == 0x66) {
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shift = 16;
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/* The instruction is 1 byte so far, read the next byte. */
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insnlen = 1;
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lgread(lg, &insn, physaddr + insnlen, 1);
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}
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/* We can ignore the lower bit for the moment and decode the 4 opcodes
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* we need to emulate. */
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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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/* OK, we don't know what this is, can't emulate. */
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return 0;
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}
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/* If it was an "IN" instruction, they expect the result to be read
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* into %eax, so we change %eax. We always return all-ones, which
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* traditionally means "there's nothing there". */
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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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/* Finally, we've "done" the instruction, so move past it. */
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lg->regs->eip += insnlen;
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/* Success! */
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return 1;
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}
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/*H:050 Once we've re-enabled interrupts, we look at why the Guest exited. */
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void lguest_arch_handle_trap(struct lguest *lg)
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{
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switch (lg->regs->trapnum) {
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case 13: /* We've intercepted a GPF. */
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/* Check if this was one of those annoying IN or OUT
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* instructions which we need to emulate. If so, we
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* just go back into the Guest after we've done it. */
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if (lg->regs->errcode == 0) {
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if (emulate_insn(lg))
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return;
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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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/* The Guest accessed a virtual address that wasn't
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* mapped. This happens a lot: we don't actually set
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* up most of the page tables for the Guest at all when
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* we start: as it runs it asks for more and more, and
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* we set them up as required. In this case, we don't
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* even tell the Guest that the fault happened.
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*
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* The errcode tells whether this was a read or a
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* write, and whether kernel or userspace code. */
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if (demand_page(lg, lg->arch.last_pagefault, lg->regs->errcode))
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return;
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/* OK, it's really not there (or not OK): the Guest
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* needs to know. We write out the cr2 value so it
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* knows where the fault occurred.
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*
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* Note that if the Guest were really messed up, this
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* could happen before it's done the INITIALIZE
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* hypercall, so lg->lguest_data will be NULL */
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if (lg->lguest_data &&
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put_user(lg->arch.last_pagefault, &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 the Guest doesn't want to know, we already
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* restored the Floating Point Unit, so we just
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* continue without telling it. */
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if (!lg->ts)
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return;
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break;
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case 32 ... 255:
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/* These values mean a real interrupt occurred, in which case
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* the Host handler has already been run. We just do a
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* friendly check if another process should now be run, then
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* return to run the Guest again */
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cond_resched();
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return;
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case LGUEST_TRAP_ENTRY:
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/* Our 'struct hcall_args' maps directly over our regs: we set
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* up the pointer now to indicate a hypercall is pending. */
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lg->hcall = (struct hcall_args *)lg->regs;
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return;
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}
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/* We didn't handle the trap, so it needs to go to the Guest. */
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if (!deliver_trap(lg, lg->regs->trapnum))
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/* If the Guest doesn't have a handler (either it hasn't
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* registered any yet, or it's one of the faults we don't let
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* it handle), it dies with a cryptic error message. */
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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 ? lg->arch.last_pagefault
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: lg->regs->errcode);
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}
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/* Now we can look at each of the routines this calls, in increasing order of
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* complexity: do_hypercalls(), emulate_insn(), maybe_do_interrupt(),
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* deliver_trap() and demand_page(). After all those, we'll be ready to
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* examine the Switcher, and our philosophical understanding of the Host/Guest
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* duality will be complete. :*/
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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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/*H:020 Now the Switcher is mapped and every thing else is ready, we need to do
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* some more i386-specific initialization. */
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void __init lguest_arch_host_init(void)
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{
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int i;
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/* Most of the i386/switcher.S doesn't care that it's been moved; on
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* Intel, jumps are relative, and it doesn't access any references to
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* external code or data.
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*
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* The only exception is the interrupt handlers in switcher.S: their
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* addresses are placed in a table (default_idt_entries), so we need to
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* update the table with the new addresses. switcher_offset() is a
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* convenience function which returns the distance between the builtin
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* switcher code and the high-mapped copy we just made. */
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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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/*
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* Set up the Switcher's per-cpu areas.
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*
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* Each CPU gets two pages of its own within the high-mapped region
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* (aka. "struct lguest_pages"). Much of this can be initialized now,
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* but some depends on what Guest we are running (which is set up in
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* copy_in_guest_info()).
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*/
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for_each_possible_cpu(i) {
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/* lguest_pages() returns this CPU's two pages. */
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struct lguest_pages *pages = lguest_pages(i);
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/* This is a convenience pointer to make the code fit one
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* statement to a line. */
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struct lguest_ro_state *state = &pages->state;
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/* The Global Descriptor Table: the Host has a different one
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* for each CPU. We keep a descriptor for the GDT which says
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* where it is and how big it is (the size is actually the last
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* byte, not the size, hence the "-1"). */
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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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/* All CPUs on the Host use the same Interrupt Descriptor
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* Table, so we just use store_idt(), which gets this CPU's IDT
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* descriptor. */
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store_idt(&state->host_idt_desc);
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/* The descriptors for the Guest's GDT and IDT can be filled
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* out now, too. We copy the GDT & IDT into ->guest_gdt and
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* ->guest_idt before actually running the Guest. */
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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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/* We know where we want the stack to be when the Guest enters
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* the switcher: in pages->regs. The stack grows upwards, so
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* we start it at the end of that structure. */
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state->guest_tss.esp0 = (long)(&pages->regs + 1);
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/* And this is the GDT entry to use for the stack: we keep a
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* couple of special LGUEST entries. */
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state->guest_tss.ss0 = LGUEST_DS;
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/* x86 can have a finegrained bitmap which indicates what I/O
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* ports the process can use. We set it to the end of our
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* structure, meaning "none". */
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state->guest_tss.io_bitmap_base = sizeof(state->guest_tss);
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/* Some GDT entries are the same across all Guests, so we can
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* set them up now. */
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setup_default_gdt_entries(state);
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/* Most IDT entries are the same for all Guests, too.*/
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setup_default_idt_entries(state, default_idt_entries);
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/* The Host needs to be able to use the LGUEST segments on this
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* CPU, too, so put them in the Host GDT. */
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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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/* In the Switcher, we want the %cs segment register to use the
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* LGUEST_CS GDT entry: we've put that in the Host and Guest GDTs, so
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* it will be undisturbed when we switch. To change %cs and jump we
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* need this structure to feed to Intel's "lcall" instruction. */
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lguest_entry.offset = (long)switch_to_guest + switcher_offset();
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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. */
|
|
lock_cpu_hotplug();
|
|
if (cpu_has_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, 0, 1);
|
|
/* Turn off the feature in the global feature set. */
|
|
clear_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
|
|
}
|
|
unlock_cpu_hotplug();
|
|
};
|
|
/*:*/
|
|
|
|
void __exit lguest_arch_host_fini(void)
|
|
{
|
|
/* If we had PGE before we started, turn it back on now. */
|
|
lock_cpu_hotplug();
|
|
if (cpu_had_pge) {
|
|
set_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
|
|
/* adjust_pge's argument "1" means set PGE. */
|
|
on_each_cpu(adjust_pge, (void *)1, 0, 1);
|
|
}
|
|
unlock_cpu_hotplug();
|
|
}
|
|
|
|
|
|
/*H:122 The i386-specific hypercalls simply farm out to the right functions. */
|
|
int lguest_arch_do_hcall(struct lguest *lg, struct hcall_args *args)
|
|
{
|
|
switch (args->arg0) {
|
|
case LHCALL_LOAD_GDT:
|
|
load_guest_gdt(lg, args->arg1, args->arg2);
|
|
break;
|
|
case LHCALL_LOAD_IDT_ENTRY:
|
|
load_guest_idt_entry(lg, args->arg1, args->arg2, args->arg3);
|
|
break;
|
|
case LHCALL_LOAD_TLS:
|
|
guest_load_tls(lg, args->arg1);
|
|
break;
|
|
default:
|
|
/* Bad Guest. Bad! */
|
|
return -EIO;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/*H:126 i386-specific hypercall initialization: */
|
|
int lguest_arch_init_hypercalls(struct lguest *lg)
|
|
{
|
|
u32 tsc_speed;
|
|
|
|
/* The pointer to the Guest's "struct lguest_data" is the only
|
|
* argument. We check that address now. */
|
|
if (!lguest_address_ok(lg, lg->hcall->arg1, sizeof(*lg->lguest_data)))
|
|
return -EFAULT;
|
|
|
|
/* Having checked it, we simply set lg->lguest_data to point straight
|
|
* into the Launcher's memory at the right place and then use
|
|
* copy_to_user/from_user from now on, instead of lgread/write. I put
|
|
* this in to show that I'm not immune to writing stupid
|
|
* optimizations. */
|
|
lg->lguest_data = lg->mem_base + lg->hcall->arg1;
|
|
|
|
/* We insist that the Time Stamp Counter exist and doesn't change with
|
|
* cpu frequency. Some devious chip manufacturers decided that TSC
|
|
* changes could be handled in software. I decided that time going
|
|
* backwards might be good for benchmarks, but it's bad for users.
|
|
*
|
|
* We also insist that the TSC be stable: the kernel detects unreliable
|
|
* TSCs for its own purposes, and we use that here. */
|
|
if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && !check_tsc_unstable())
|
|
tsc_speed = tsc_khz;
|
|
else
|
|
tsc_speed = 0;
|
|
if (put_user(tsc_speed, &lg->lguest_data->tsc_khz))
|
|
return -EFAULT;
|
|
|
|
return 0;
|
|
}
|
|
/* Now we've examined the hypercall code; our Guest can make requests. There
|
|
* is one other way we can do things for the Guest, as we see in
|
|
* emulate_insn(). :*/
|