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diff --git a/src/VBox/VMM/VMMAll/GCMAll.cpp b/src/VBox/VMM/VMMAll/GCMAll.cpp
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+/** @file
+ * GCM - Guest Compatibility Manager - All Contexts.
+ */
+
+/*
+ * Copyright (C) 2022-2023 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_GIM
+#include <VBox/vmm/gcm.h>
+#include <VBox/vmm/em.h> /* For EMInterpretDisasCurrent */
+#include "GCMInternal.h"
+#include <VBox/vmm/vmcc.h>
+
+#include <VBox/dis.h> /* For DISCPUSTATE */
+#include <iprt/errcore.h>
+#include <iprt/string.h>
+
+
+/**
+ * Checks whether GCM is enabled for this VM.
+ *
+ * @retval true if GCM is on.
+ * @retval false if no GCM fixer is enabled.
+ *
+ * @param pVM The cross context VM structure.
+ */
+VMMDECL(bool) GCMIsEnabled(PVM pVM)
+{
+ return pVM->gcm.s.enmFixerIds != GCMFIXER_NONE;
+}
+
+
+/**
+ * Gets the GCM fixers configured for this VM.
+ *
+ * @returns The GCM provider Id.
+ * @param pVM The cross context VM structure.
+ */
+VMMDECL(int32_t) GCMGetFixers(PVM pVM)
+{
+ return pVM->gcm.s.enmFixerIds;
+}
+
+
+/**
+ * Whether \#DE exceptions in the guest should be intercepted by GCM and
+ * possibly fixed up.
+ *
+ * @returns true if needed, false otherwise.
+ * @param pVCpu The cross context virtual CPU structure.
+ */
+VMM_INT_DECL(bool) GCMShouldTrapXcptDE(PVMCPUCC pVCpu)
+{
+ LogFlowFunc(("entered\n"));
+ PVM pVM = pVCpu->CTX_SUFF(pVM);
+ if (!GCMIsEnabled(pVM))
+ return false;
+
+ LogFunc(("GCM checking if #DE needs trapping\n"));
+
+ /* See if the enabled fixers need to intercept #DE. */
+ if ( pVM->gcm.s.enmFixerIds
+ & (GCMFIXER_DBZ_DOS | GCMFIXER_DBZ_OS2 | GCMFIXER_DBZ_WIN9X))
+ {
+ LogRel(("GCM: #DE should be trapped\n"));
+ return true;
+ }
+
+ return false;
+}
+
+
+/**
+ * Exception handler for \#DE when registered by GCM.
+ *
+ * @returns Strict VBox status code.
+ * @retval VINF_SUCCESS retry division and continue.
+ * @retval VERR_NOT_FOUND deliver exception to guest.
+ *
+ * @param pVCpu The cross context virtual CPU structure.
+ * @param pCtx Pointer to the guest-CPU context.
+ * @param pDis Pointer to the disassembled instruction state at RIP.
+ * If NULL is passed, it implies the disassembly of the
+ * the instruction at RIP is the
+ * responsibility of GCM.
+ * @param pcbInstr Where to store the instruction length of
+ * the divide instruction. Optional, can be
+ * NULL.
+ *
+ * @thread EMT(pVCpu).
+ */
+VMM_INT_DECL(VBOXSTRICTRC) GCMXcptDE(PVMCPUCC pVCpu, PCPUMCTX pCtx, PDISCPUSTATE pDis, uint8_t *pcbInstr)
+{
+ PVMCC pVM = pVCpu->CTX_SUFF(pVM);
+ Assert(GCMIsEnabled(pVM));
+ Assert(pDis || pcbInstr);
+ RT_NOREF(pDis);
+ RT_NOREF(pcbInstr);
+
+ LogRel(("GCM: Intercepted #DE at CS:RIP=%04x:%RX64 (%RX64 linear) RDX:RAX=%RX64:%RX64 RCX=%RX64 RBX=%RX64\n",
+ pCtx->cs.Sel, pCtx->rip, pCtx->cs.u64Base + pCtx->rip, pCtx->rdx, pCtx->rax, pCtx->rcx, pCtx->rbx));
+
+ if (pVM->gcm.s.enmFixerIds & GCMFIXER_DBZ_OS2)
+ {
+ if (pCtx->rcx == 0 && pCtx->rdx == 1 && pCtx->rax == 0x86a0)
+ {
+ /* OS/2 1.x drivers loaded during boot: DX:AX = 100,000, CX < 2 causes overflow. */
+ /* Example: OS/2 1.0 KBD01.SYS, 16,945 bytes, dated 10/21/1987, div cx at offset 2:2ffeh */
+ /* Code later merged into BASEDD01.SYS, crash fixed in OS/2 1.30.1; this should
+ * fix all affected versions of OS/2 1.x.
+ */
+ pCtx->rcx = 2;
+ return VINF_SUCCESS;
+ }
+ if ((uint16_t)pCtx->rbx == 0 && (uint16_t)pCtx->rdx == 0 && (uint16_t)pCtx->rax == 0x1000)
+ {
+ /* OS/2 2.1 and later boot loader: DX:AX = 0x1000, zero BX. May have junk in high words of all registers. */
+ /* Example: OS/2 MCP2 OS2LDR, 44,544 bytes, dated 03/08/2002, idiv bx at offset 847ah */
+ pCtx->rbx = (pCtx->rbx & ~0xffff) | 2;
+ return VINF_SUCCESS;
+ }
+ if (pCtx->rbx == 0 && pCtx->rdx == 0 && pCtx->rax == 0x100)
+ {
+ /* OS/2 2.0 boot loader: DX:AX = 0x100, zero BX. May have junk in high words of registers. */
+ /* Example: OS/2 2.0 OS2LDR, 32,256 bytes, dated 03/30/1992, idiv bx at offset 2298h */
+ pCtx->rbx = 2;
+ return VINF_SUCCESS;
+ }
+ }
+
+ if (pVM->gcm.s.enmFixerIds & GCMFIXER_DBZ_DOS)
+ {
+ /* NB: For 16-bit DOS software, we must generally only compare 16-bit registers.
+ * The contents of the high words may be unpredictable depending on the environment.
+ * For 32-bit Windows 3.x code that is not the case.
+ */
+ if (pCtx->rcx == 0 && pCtx->rdx == 0 && pCtx->rax == 0x100000)
+ {
+ /* NDIS.386 in WfW 3.11: CalibrateStall, EDX:EAX = 0x100000, zero ECX.
+ * Occurs when NDIS.386 loads.
+ */
+ pCtx->rcx = 0x20000; /* Want a large divisor to shorten stalls. */
+ return VINF_SUCCESS;
+ }
+ if (pCtx->rcx == 0 && pCtx->rdx == 0 && pCtx->rax > 0x100000)
+ {
+ /* NDIS.386 in WfW 3.11: NdisStallExecution, EDX:EAX = 0xYY00000, zero ECX.
+ * EDX:EAX is variable, but low 20 bits of EAX must be zero and EDX is likely
+ * to be zero as well.
+ * Only occurs if NdisStallExecution is called to do a longish stall.
+ */
+ pCtx->rcx = 22;
+ return VINF_SUCCESS;
+ }
+ if ((uint16_t)pCtx->rbx == 0 && (uint16_t)pCtx->rdx == 0 && (uint16_t)pCtx->rax == 0x64)
+ {
+ /* Norton Sysinfo or Diagnostics 8.0 DX:AX = 0x64 (100 decimal), zero BX. */
+ pCtx->rbx = (pCtx->rbx & 0xffff0000) | 1; /* BX = 1 */
+ return VINF_SUCCESS;
+ }
+ if ((uint16_t)pCtx->rbx == 0 && (uint16_t)pCtx->rdx == 0 && (uint16_t)pCtx->rax == 0xff)
+ {
+ /* IBM PC LAN Program 1.3: DX:AX=0xff (255 decimal), zero BX. */
+ /* NETWORK1.CMD, 64,324 bytes, dated 06/06/1988, div bx at offset 0xa400 in file. */
+ pCtx->rbx = (pCtx->rbx & 0xffff0000) | 1; /* BX = 1 */
+ return VINF_SUCCESS;
+ }
+ if ((uint16_t)pCtx->rdx == 0xffff && (uint16_t)pCtx->rax == 0xffff && (uint16_t)pCtx->rcx == 0xa8c0)
+ {
+ /* QNX 2.15C: DX:AX=0xffffffff (-1), constant CX = 0xa8c0 (43200). */
+ /* div cx at e.g. 2220:fa5 and 2220:10a0 in memory. */
+ pCtx->rdx = (pCtx->rdx & 0xffff0000) | 8; /* DX = 8 */
+ return VINF_SUCCESS;
+ }
+ if ((uint16_t)pCtx->rax > 0x1800 && ((uint16_t)pCtx->rax & 0x3f) == 0 && (uint16_t)pCtx->rbx == 0x19)
+ {
+ /* 3C501.COM ODI driver v1.21: AX > ~0x1900 (-1), BX = 0x19 (25). */
+ /* AX was shifted left by 6 bits so low bits must be zero. */
+ /* div bl at e.g. 06b3:2f80 and offset 0x2E80 in file. */
+ pCtx->rax = (pCtx->rax & 0xffff0000) | 0x8c0; /* AX = 0x8c0 */
+ return VINF_SUCCESS;
+ }
+ if ((uint16_t)pCtx->rcx == 0x37 && ((uint16_t)pCtx->rdx > 0x34))
+ {
+ /* Turbo Pascal, classic Runtime Error 200: CX = 55, DX > ~54, AX/BX variable. */
+ /* div cx at variable offset in file. */
+ pCtx->rdx = (pCtx->rdx & 0xffff0000) | 0x30; /* DX = 48 */
+ return VINF_SUCCESS;
+ }
+ }
+
+ if (pVM->gcm.s.enmFixerIds & GCMFIXER_DBZ_WIN9X)
+ {
+ if (pCtx->rcx == 0 && pCtx->rdx == 0 && pCtx->rax == 0x100000)
+ {
+ /* NDIS.VXD in Win9x: EDX:EAX = 0x100000, zero ECX. */
+ /* Example: Windows 95 NDIS.VXD, 99,084 bytes, dated 07/11/1994, div ecx at 28:Cxxxx80B */
+ /* Crash fixed in Windows 98 SE. */
+ pCtx->rcx = 0x20000; /* Want a large divisor to shorten stalls. */
+ return VINF_SUCCESS;
+ }
+ if (pCtx->rcx < 3 && pCtx->rdx == 2 && pCtx->rax == 0x540be400)
+ {
+ /* SCSI.PDR, ESDI506.PDR in Win95: EDX:EAX = 0x2540be400 (10,000,000,000 decimal), ECX < 3. */
+ /* Example: Windows 95 SCSIPORT.PDR, 23,133 bytes, dated 07/11/1995, div ecx at 28:Cxxxx876 */
+ /* Example: Win95 OSR2 ESDI506.PDR, 24,390 bytes, dated 04/24/1996, div ecx at 28:Cxxxx8E3 */
+ /* Crash fixed in Windows 98. */
+ pCtx->rcx = 1000;
+ return VINF_SUCCESS;
+ }
+ if (pCtx->rcx == 0 && pCtx->rdx == 0x3d && pCtx->rax == 0x9000000)
+ {
+ /* Unknown source, Win9x shutdown, div ecx. */
+ /* GCM: Intercepted #DE at CS:RIP=0028:c0050f8e RDX:RAX=3d:9000000 (250000*1024*1024) RCX=0 RBX=c19200e8 [RBX variable] */
+ pCtx->rcx = 4096;
+ return VINF_SUCCESS;
+ }
+ }
+
+ /* If we got this far, deliver exception to guest. */
+ return VERR_NOT_FOUND;
+}
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