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/* $Id: VMMR0TripleFaultHack.cpp $ */
/** @file
* VMM - Host Context Ring 0, Triple Fault Debugging Hack.
*
* Only use this when desperate. May not work on all systems, esp. newer ones,
* since it require BIOS support for the warm reset vector at 0467h.
*/
/*
* Copyright (C) 2011-2023 Oracle and/or its affiliates.
*
* This file is part of VirtualBox base platform packages, as
* available from https://www.virtualbox.org.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation, in version 3 of the
* License.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <https://www.gnu.org/licenses>.
*
* SPDX-License-Identifier: GPL-3.0-only
*/
/*********************************************************************************************************************************
* Header Files *
*********************************************************************************************************************************/
#define LOG_GROUP LOG_GROUP_VMM
#include <VBox/vmm/vmm.h>
#include "VMMInternal.h"
#include <VBox/param.h>
#include <iprt/asm-amd64-x86.h>
#include <iprt/assert.h>
#include <iprt/memobj.h>
#include <iprt/mem.h>
#include <iprt/string.h>
/*********************************************************************************************************************************
* Global Variables *
*********************************************************************************************************************************/
static RTR0MEMOBJ g_hMemPage0;
static RTR0MEMOBJ g_hMapPage0;
static uint8_t *g_pbPage0;
static RTR0MEMOBJ g_hMemLowCore;
static RTR0MEMOBJ g_hMapLowCore;
static uint8_t *g_pbLowCore;
static RTHCPHYS g_HCPhysLowCore;
/** @name For restoring memory we've overwritten.
* @{ */
static uint32_t g_u32SavedVector;
static uint16_t g_u16SavedCadIndicator;
static void *g_pvSavedLowCore;
/** @} */
/*********************************************************************************************************************************
* Internal Functions *
*********************************************************************************************************************************/
/* VMMR0TripleFaultHackA.asm */
DECLASM(void) vmmR0TripleFaultHackStart(void);
DECLASM(void) vmmR0TripleFaultHackEnd(void);
DECLASM(void) vmmR0TripleFaultHackTripleFault(void);
/**
* Initalizes the triple fault / boot hack.
*
* Always call vmmR0TripleFaultHackTerm to clean up, even when this call fails.
*
* @returns VBox status code.
*/
int vmmR0TripleFaultHackInit(void)
{
/*
* Map the first page.
*/
int rc = RTR0MemObjEnterPhys(&g_hMemPage0, 0, HOST_PAGE_SIZE, RTMEM_CACHE_POLICY_DONT_CARE);
AssertRCReturn(rc, rc);
rc = RTR0MemObjMapKernel(&g_hMapPage0, g_hMemPage0, (void *)-1, 0, RTMEM_PROT_READ | RTMEM_PROT_WRITE);
AssertRCReturn(rc, rc);
g_pbPage0 = (uint8_t *)RTR0MemObjAddress(g_hMapPage0);
LogRel(("0040:0067 = %04x:%04x\n", RT_MAKE_U16(g_pbPage0[0x467+2], g_pbPage0[0x467+3]), RT_MAKE_U16(g_pbPage0[0x467+0], g_pbPage0[0x467+1]) ));
/*
* Allocate some "low core" memory. If that fails, just grab some memory.
*/
//rc = RTR0MemObjAllocPhys(&g_hMemLowCore, HOST_PAGE_SIZE, _1M - 1);
//__debugbreak();
rc = RTR0MemObjEnterPhys(&g_hMemLowCore, 0x7000, HOST_PAGE_SIZE, RTMEM_CACHE_POLICY_DONT_CARE);
AssertRCReturn(rc, rc);
rc = RTR0MemObjMapKernel(&g_hMapLowCore, g_hMemLowCore, (void *)-1, 0, RTMEM_PROT_READ | RTMEM_PROT_WRITE);
AssertRCReturn(rc, rc);
g_pbLowCore = (uint8_t *)RTR0MemObjAddress(g_hMapLowCore);
g_HCPhysLowCore = RTR0MemObjGetPagePhysAddr(g_hMapLowCore, 0);
LogRel(("Low core at %RHp mapped at %p\n", g_HCPhysLowCore, g_pbLowCore));
/*
* Save memory we'll be overwriting.
*/
g_pvSavedLowCore = RTMemAlloc(HOST_PAGE_SIZE);
AssertReturn(g_pvSavedLowCore, VERR_NO_MEMORY);
memcpy(g_pvSavedLowCore, g_pbLowCore, HOST_PAGE_SIZE);
g_u32SavedVector = RT_MAKE_U32_FROM_U8(g_pbPage0[0x467], g_pbPage0[0x467+1], g_pbPage0[0x467+2], g_pbPage0[0x467+3]);
g_u16SavedCadIndicator = RT_MAKE_U16(g_pbPage0[0x472], g_pbPage0[0x472+1]);
/*
* Install the code.
*/
size_t cbCode = (uintptr_t)&vmmR0TripleFaultHackEnd - (uintptr_t)&vmmR0TripleFaultHackStart;
AssertLogRelReturn(cbCode <= HOST_PAGE_SIZE, VERR_OUT_OF_RANGE);
memcpy(g_pbLowCore, &vmmR0TripleFaultHackStart, cbCode);
g_pbPage0[0x467+0] = 0x00;
g_pbPage0[0x467+1] = 0x70;
g_pbPage0[0x467+2] = 0x00;
g_pbPage0[0x467+3] = 0x00;
g_pbPage0[0x472+0] = 0x34;
g_pbPage0[0x472+1] = 0x12;
/*
* Configure the status port and cmos shutdown command.
*/
uint32_t fSaved = ASMIntDisableFlags();
ASMOutU8(0x70, 0x0f);
ASMOutU8(0x71, 0x0a);
ASMOutU8(0x70, 0x05);
ASMInU8(0x71);
ASMReloadCR3();
ASMWriteBackAndInvalidateCaches();
ASMSetFlags(fSaved);
#if 1 /* For testing & debugging. */
vmmR0TripleFaultHackTripleFault();
#endif
return VINF_SUCCESS;
}
/**
* Try undo the harm done by the init function.
*
* This may leave the system in an unstable state since we might have been
* hijacking memory below 1MB that is in use by the kernel.
*/
void vmmR0TripleFaultHackTerm(void)
{
/*
* Restore overwritten memory.
*/
if ( g_pvSavedLowCore
&& g_pbLowCore)
memcpy(g_pbLowCore, g_pvSavedLowCore, HOST_PAGE_SIZE);
if (g_pbPage0)
{
g_pbPage0[0x467+0] = RT_BYTE1(g_u32SavedVector);
g_pbPage0[0x467+1] = RT_BYTE2(g_u32SavedVector);
g_pbPage0[0x467+2] = RT_BYTE3(g_u32SavedVector);
g_pbPage0[0x467+3] = RT_BYTE4(g_u32SavedVector);
g_pbPage0[0x472+0] = RT_BYTE1(g_u16SavedCadIndicator);
g_pbPage0[0x472+1] = RT_BYTE2(g_u16SavedCadIndicator);
}
/*
* Fix the CMOS.
*/
if (g_pvSavedLowCore)
{
uint32_t fSaved = ASMIntDisableFlags();
ASMOutU8(0x70, 0x0f);
ASMOutU8(0x71, 0x0a);
ASMOutU8(0x70, 0x00);
ASMInU8(0x71);
ASMReloadCR3();
ASMWriteBackAndInvalidateCaches();
ASMSetFlags(fSaved);
}
/*
* Release resources.
*/
RTMemFree(g_pvSavedLowCore);
g_pvSavedLowCore = NULL;
RTR0MemObjFree(g_hMemLowCore, true /*fFreeMappings*/);
g_hMemLowCore = NIL_RTR0MEMOBJ;
g_hMapLowCore = NIL_RTR0MEMOBJ;
g_pbLowCore = NULL;
g_HCPhysLowCore = NIL_RTHCPHYS;
RTR0MemObjFree(g_hMemPage0, true /*fFreeMappings*/);
g_hMemPage0 = NIL_RTR0MEMOBJ;
g_hMapPage0 = NIL_RTR0MEMOBJ;
g_pbPage0 = NULL;
}
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