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19b75ef59a
freebsd-dev/sys/amd64/vmm/intel/vmcs.c
Tycho Nightingale 58a6aaf7ec Provide further mitigation against CVE-2017-5715 by flushing the 
return stack buffer (RSB) upon returning from the guest.

This was inspired by this linux commit:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/x86/kvm?id=117cc7a908c83697b0b737d15ae1eb5943afe35b

Reviewed by:	grehan
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D14272
2018-02-12 14:45:27 +00:00

520 lines
12 KiB
C
Raw Blame History

/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2011 NetApp, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY NETAPP, INC ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL NETAPP, INC OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#include "opt_ddb.h"
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/pcpu.h>
#include <vm/vm.h>
#include <vm/pmap.h>
#include <machine/segments.h>
#include <machine/vmm.h>
#include "vmm_host.h"
#include "vmx_cpufunc.h"
#include "vmcs.h"
#include "ept.h"
#include "vmx.h"
#ifdef DDB
#include <ddb/ddb.h>
#endif
SYSCTL_DECL(_hw_vmm_vmx);
static int no_flush_rsb;
SYSCTL_INT(_hw_vmm_vmx, OID_AUTO, no_flush_rsb, CTLFLAG_RW,
&no_flush_rsb, 0, "Do not flush RSB upon vmexit");
static uint64_t
vmcs_fix_regval(uint32_t encoding, uint64_t val)
{
switch (encoding) {
case VMCS_GUEST_CR0:
val = vmx_fix_cr0(val);
break;
case VMCS_GUEST_CR4:
val = vmx_fix_cr4(val);
break;
default:
break;
}
return (val);
}
static uint32_t
vmcs_field_encoding(int ident)
{
switch (ident) {
case VM_REG_GUEST_CR0:
return (VMCS_GUEST_CR0);
case VM_REG_GUEST_CR3:
return (VMCS_GUEST_CR3);
case VM_REG_GUEST_CR4:
return (VMCS_GUEST_CR4);
case VM_REG_GUEST_DR7:
return (VMCS_GUEST_DR7);
case VM_REG_GUEST_RSP:
return (VMCS_GUEST_RSP);
case VM_REG_GUEST_RIP:
return (VMCS_GUEST_RIP);
case VM_REG_GUEST_RFLAGS:
return (VMCS_GUEST_RFLAGS);
case VM_REG_GUEST_ES:
return (VMCS_GUEST_ES_SELECTOR);
case VM_REG_GUEST_CS:
return (VMCS_GUEST_CS_SELECTOR);
case VM_REG_GUEST_SS:
return (VMCS_GUEST_SS_SELECTOR);
case VM_REG_GUEST_DS:
return (VMCS_GUEST_DS_SELECTOR);
case VM_REG_GUEST_FS:
return (VMCS_GUEST_FS_SELECTOR);
case VM_REG_GUEST_GS:
return (VMCS_GUEST_GS_SELECTOR);
case VM_REG_GUEST_TR:
return (VMCS_GUEST_TR_SELECTOR);
case VM_REG_GUEST_LDTR:
return (VMCS_GUEST_LDTR_SELECTOR);
case VM_REG_GUEST_EFER:
return (VMCS_GUEST_IA32_EFER);
case VM_REG_GUEST_PDPTE0:
return (VMCS_GUEST_PDPTE0);
case VM_REG_GUEST_PDPTE1:
return (VMCS_GUEST_PDPTE1);
case VM_REG_GUEST_PDPTE2:
return (VMCS_GUEST_PDPTE2);
case VM_REG_GUEST_PDPTE3:
return (VMCS_GUEST_PDPTE3);
default:
return (-1);
}
}
static int
vmcs_seg_desc_encoding(int seg, uint32_t *base, uint32_t *lim, uint32_t *acc)
{
switch (seg) {
case VM_REG_GUEST_ES:
*base = VMCS_GUEST_ES_BASE;
*lim = VMCS_GUEST_ES_LIMIT;
*acc = VMCS_GUEST_ES_ACCESS_RIGHTS;
break;
case VM_REG_GUEST_CS:
*base = VMCS_GUEST_CS_BASE;
*lim = VMCS_GUEST_CS_LIMIT;
*acc = VMCS_GUEST_CS_ACCESS_RIGHTS;
break;
case VM_REG_GUEST_SS:
*base = VMCS_GUEST_SS_BASE;
*lim = VMCS_GUEST_SS_LIMIT;
*acc = VMCS_GUEST_SS_ACCESS_RIGHTS;
break;
case VM_REG_GUEST_DS:
*base = VMCS_GUEST_DS_BASE;
*lim = VMCS_GUEST_DS_LIMIT;
*acc = VMCS_GUEST_DS_ACCESS_RIGHTS;
break;
case VM_REG_GUEST_FS:
*base = VMCS_GUEST_FS_BASE;
*lim = VMCS_GUEST_FS_LIMIT;
*acc = VMCS_GUEST_FS_ACCESS_RIGHTS;
break;
case VM_REG_GUEST_GS:
*base = VMCS_GUEST_GS_BASE;
*lim = VMCS_GUEST_GS_LIMIT;
*acc = VMCS_GUEST_GS_ACCESS_RIGHTS;
break;
case VM_REG_GUEST_TR:
*base = VMCS_GUEST_TR_BASE;
*lim = VMCS_GUEST_TR_LIMIT;
*acc = VMCS_GUEST_TR_ACCESS_RIGHTS;
break;
case VM_REG_GUEST_LDTR:
*base = VMCS_GUEST_LDTR_BASE;
*lim = VMCS_GUEST_LDTR_LIMIT;
*acc = VMCS_GUEST_LDTR_ACCESS_RIGHTS;
break;
case VM_REG_GUEST_IDTR:
*base = VMCS_GUEST_IDTR_BASE;
*lim = VMCS_GUEST_IDTR_LIMIT;
*acc = VMCS_INVALID_ENCODING;
break;
case VM_REG_GUEST_GDTR:
*base = VMCS_GUEST_GDTR_BASE;
*lim = VMCS_GUEST_GDTR_LIMIT;
*acc = VMCS_INVALID_ENCODING;
break;
default:
return (EINVAL);
}
return (0);
}
int
vmcs_getreg(struct vmcs *vmcs, int running, int ident, uint64_t *retval)
{
int error;
uint32_t encoding;
/*
* If we need to get at vmx-specific state in the VMCS we can bypass
* the translation of 'ident' to 'encoding' by simply setting the
* sign bit. As it so happens the upper 16 bits are reserved (i.e
* set to 0) in the encodings for the VMCS so we are free to use the
* sign bit.
*/
if (ident < 0)
encoding = ident & 0x7fffffff;
else
encoding = vmcs_field_encoding(ident);
if (encoding == (uint32_t)-1)
return (EINVAL);
if (!running)
VMPTRLD(vmcs);
error = vmread(encoding, retval);
if (!running)
VMCLEAR(vmcs);
return (error);
}
int
vmcs_setreg(struct vmcs *vmcs, int running, int ident, uint64_t val)
{
int error;
uint32_t encoding;
if (ident < 0)
encoding = ident & 0x7fffffff;
else
encoding = vmcs_field_encoding(ident);
if (encoding == (uint32_t)-1)
return (EINVAL);
val = vmcs_fix_regval(encoding, val);
if (!running)
VMPTRLD(vmcs);
error = vmwrite(encoding, val);
if (!running)
VMCLEAR(vmcs);
return (error);
}
int
vmcs_setdesc(struct vmcs *vmcs, int running, int seg, struct seg_desc *desc)
{
int error;
uint32_t base, limit, access;
error = vmcs_seg_desc_encoding(seg, &base, &limit, &access);
if (error != 0)
panic("vmcs_setdesc: invalid segment register %d", seg);
if (!running)
VMPTRLD(vmcs);
if ((error = vmwrite(base, desc->base)) != 0)
goto done;
if ((error = vmwrite(limit, desc->limit)) != 0)
goto done;
if (access != VMCS_INVALID_ENCODING) {
if ((error = vmwrite(access, desc->access)) != 0)
goto done;
}
done:
if (!running)
VMCLEAR(vmcs);
return (error);
}
int
vmcs_getdesc(struct vmcs *vmcs, int running, int seg, struct seg_desc *desc)
{
int error;
uint32_t base, limit, access;
uint64_t u64;
error = vmcs_seg_desc_encoding(seg, &base, &limit, &access);
if (error != 0)
panic("vmcs_getdesc: invalid segment register %d", seg);
if (!running)
VMPTRLD(vmcs);
if ((error = vmread(base, &u64)) != 0)
goto done;
desc->base = u64;
if ((error = vmread(limit, &u64)) != 0)
goto done;
desc->limit = u64;
if (access != VMCS_INVALID_ENCODING) {
if ((error = vmread(access, &u64)) != 0)
goto done;
desc->access = u64;
}
done:
if (!running)
VMCLEAR(vmcs);
return (error);
}
int
vmcs_set_msr_save(struct vmcs *vmcs, u_long g_area, u_int g_count)
{
int error;
VMPTRLD(vmcs);
/*
* Guest MSRs are saved in the VM-exit MSR-store area.
* Guest MSRs are loaded from the VM-entry MSR-load area.
* Both areas point to the same location in memory.
*/
if ((error = vmwrite(VMCS_EXIT_MSR_STORE, g_area)) != 0)
goto done;
if ((error = vmwrite(VMCS_EXIT_MSR_STORE_COUNT, g_count)) != 0)
goto done;
if ((error = vmwrite(VMCS_ENTRY_MSR_LOAD, g_area)) != 0)
goto done;
if ((error = vmwrite(VMCS_ENTRY_MSR_LOAD_COUNT, g_count)) != 0)
goto done;
error = 0;
done:
VMCLEAR(vmcs);
return (error);
}
int
vmcs_init(struct vmcs *vmcs)
{
int error, codesel, datasel, tsssel;
u_long cr0, cr4, efer;
uint64_t pat, fsbase, idtrbase;
codesel = vmm_get_host_codesel();
datasel = vmm_get_host_datasel();
tsssel = vmm_get_host_tsssel();
/*
* Make sure we have a "current" VMCS to work with.
*/
VMPTRLD(vmcs);
/* Host state */
/* Initialize host IA32_PAT MSR */
pat = vmm_get_host_pat();
if ((error = vmwrite(VMCS_HOST_IA32_PAT, pat)) != 0)
goto done;
/* Load the IA32_EFER MSR */
efer = vmm_get_host_efer();
if ((error = vmwrite(VMCS_HOST_IA32_EFER, efer)) != 0)
goto done;
/* Load the control registers */
cr0 = vmm_get_host_cr0();
if ((error = vmwrite(VMCS_HOST_CR0, cr0)) != 0)
goto done;
cr4 = vmm_get_host_cr4() | CR4_VMXE;
if ((error = vmwrite(VMCS_HOST_CR4, cr4)) != 0)
goto done;
/* Load the segment selectors */
if ((error = vmwrite(VMCS_HOST_ES_SELECTOR, datasel)) != 0)
goto done;
if ((error = vmwrite(VMCS_HOST_CS_SELECTOR, codesel)) != 0)
goto done;
if ((error = vmwrite(VMCS_HOST_SS_SELECTOR, datasel)) != 0)
goto done;
if ((error = vmwrite(VMCS_HOST_DS_SELECTOR, datasel)) != 0)
goto done;
if ((error = vmwrite(VMCS_HOST_FS_SELECTOR, datasel)) != 0)
goto done;
if ((error = vmwrite(VMCS_HOST_GS_SELECTOR, datasel)) != 0)
goto done;
if ((error = vmwrite(VMCS_HOST_TR_SELECTOR, tsssel)) != 0)
goto done;
/*
* Load the Base-Address for %fs and idtr.
*
* Note that we exclude %gs, tss and gdtr here because their base
* address is pcpu specific.
*/
fsbase = vmm_get_host_fsbase();
if ((error = vmwrite(VMCS_HOST_FS_BASE, fsbase)) != 0)
goto done;
idtrbase = vmm_get_host_idtrbase();
if ((error = vmwrite(VMCS_HOST_IDTR_BASE, idtrbase)) != 0)
goto done;
/* instruction pointer */
if (no_flush_rsb) {
if ((error = vmwrite(VMCS_HOST_RIP,
(u_long)vmx_exit_guest)) != 0)
goto done;
} else {
if ((error = vmwrite(VMCS_HOST_RIP,
(u_long)vmx_exit_guest_flush_rsb)) != 0)
goto done;
}
/* link pointer */
if ((error = vmwrite(VMCS_LINK_POINTER, ~0)) != 0)
goto done;
done:
VMCLEAR(vmcs);
return (error);
}
#ifdef DDB
extern int vmxon_enabled[];
DB_SHOW_COMMAND(vmcs, db_show_vmcs)
{
uint64_t cur_vmcs, val;
uint32_t exit;
if (!vmxon_enabled[curcpu]) {
db_printf("VMX not enabled\n");
return;
}
if (have_addr) {
db_printf("Only current VMCS supported\n");
return;
}
vmptrst(&cur_vmcs);
if (cur_vmcs == VMCS_INITIAL) {
db_printf("No current VM context\n");
return;
}
db_printf("VMCS: %jx\n", cur_vmcs);
db_printf("VPID: %lu\n", vmcs_read(VMCS_VPID));
db_printf("Activity: ");
val = vmcs_read(VMCS_GUEST_ACTIVITY);
switch (val) {
case 0:
db_printf("Active");
break;
case 1:
db_printf("HLT");
break;
case 2:
db_printf("Shutdown");
break;
case 3:
db_printf("Wait for SIPI");
break;
default:
db_printf("Unknown: %#lx", val);
}
db_printf("\n");
exit = vmcs_read(VMCS_EXIT_REASON);
if (exit & 0x80000000)
db_printf("Entry Failure Reason: %u\n", exit & 0xffff);
else
db_printf("Exit Reason: %u\n", exit & 0xffff);
db_printf("Qualification: %#lx\n", vmcs_exit_qualification());
db_printf("Guest Linear Address: %#lx\n",
vmcs_read(VMCS_GUEST_LINEAR_ADDRESS));
switch (exit & 0x8000ffff) {
case EXIT_REASON_EXCEPTION:
case EXIT_REASON_EXT_INTR:
val = vmcs_read(VMCS_EXIT_INTR_INFO);
db_printf("Interrupt Type: ");
switch (val >> 8 & 0x7) {
case 0:
db_printf("external");
break;
case 2:
db_printf("NMI");
break;
case 3:
db_printf("HW exception");
break;
case 4:
db_printf("SW exception");
break;
default:
db_printf("?? %lu", val >> 8 & 0x7);
break;
}
db_printf(" Vector: %lu", val & 0xff);
if (val & 0x800)
db_printf(" Error Code: %lx",
vmcs_read(VMCS_EXIT_INTR_ERRCODE));
db_printf("\n");
break;
case EXIT_REASON_EPT_FAULT:
case EXIT_REASON_EPT_MISCONFIG:
db_printf("Guest Physical Address: %#lx\n",
vmcs_read(VMCS_GUEST_PHYSICAL_ADDRESS));
break;
}
db_printf("VM-instruction error: %#lx\n", vmcs_instruction_error());
}
#endif
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