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206 lines
4.1 KiB
206 lines
4.1 KiB
/*++
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Copyright (c) 1989 Microsoft Corporation
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Module Name:
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npxnp.c
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Abstract:
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This module contains support for non-Flat mode NPX faults when
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the application has it's CR0_EM bit clear.
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Author:
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Ken Reneris (kenr) 8-Dec-1994
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Environment:
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User Mode only
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Revision History:
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--*/
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#pragma warning(disable:4201) // nameless struct/union
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#include "csrdll.h"
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static UCHAR MOD16[] = { 0, 1, 2, 0 };
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static UCHAR MOD32[] = { 0, 1, 4, 0 };
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UCHAR
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NpxNpReadCSEip (
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IN PCONTEXT Context
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)
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#pragma warning(disable:4035)
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{
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_asm {
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push es
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mov ecx, Context
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mov eax, [ecx] CONTEXT.SegCs
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mov es, ax
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mov eax, [ecx] CONTEXT.Eip
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inc dword ptr [ecx] CONTEXT.Eip ; Advance EIP
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mov al, es:[eax]
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pop es
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}
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}
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#pragma warning(default:4035)
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VOID
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NpxNpSkipInstruction (
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IN PCONTEXT Context
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)
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/*++
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Routine Description:
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This functions gains control when the system has no installed
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NPX support, but the thread has cleared it's EM bit in CR0.
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The purpose of this function is to move the instruction
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pointer forward over the current NPX instruction.
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Enviroment:
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16:16 mode
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Arguments:
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Return Value:
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--*/
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{
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BOOLEAN fPrefix;
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UCHAR ibyte, Mod, rm;
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UCHAR Address32Bits;
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ULONG CallerCs;
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Address32Bits = 0; // assume called from 16:16
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//
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// Lookup and determine callers default mode
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//
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CallerCs = Context->SegCs;
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_asm {
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mov eax, CallerCs
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lar eax, eax
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test eax, 400000h
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jz short IsDefault16Bit
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mov Address32Bits, 1
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IsDefault16Bit:
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}
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//
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// No sense in using a try-except since we are not on the
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// correct stack. A fault here could occur if the start
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// of an NPX instruction is near the end of a selector, and the
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// end of the instruction is past the selectors end. This
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// would kill the app anyway.
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//
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//
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// Read any instruction prefixes
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//
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fPrefix = TRUE;
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while (fPrefix) {
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ibyte = NpxNpReadCSEip(Context);
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switch (ibyte) {
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case 0x2e: // cs override, skip it
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case 0x36: // ss override, skip it
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case 0x3e: // ds override, skip it
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case 0x26: // es override, skip it
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case 0x64: // fs override, skip it
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case 0x65: // gs override, skip it
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case 0x66: // operand size override, skip it
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break;
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case 0x67:
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// address size override
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Address32Bits ^= 1;
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break;
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default:
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fPrefix = FALSE;
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break;
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}
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}
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//
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// Handle first byte of NPX instruction
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//
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if (ibyte == 0x9b) {
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//
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// FWait instruction - single byte opcode - all done
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//
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return;
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}
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if (ibyte < 0xD8 || ibyte > 0xDF) {
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//
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// Not an ESC instruction
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//
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#if DBG
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DbgPrint ("P5_FPU_PATCH: 16: Not NPX ESC instruction\n");
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#endif
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return;
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}
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//
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// Get ModR/M byte for NPX opcode
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//
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ibyte = NpxNpReadCSEip(Context);
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if (ibyte > 0xbf) {
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//
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// Outside of ModR/M range for addressing, all done
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//
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return;
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}
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Mod = ibyte >> 6;
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rm = ibyte & 0x7;
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if (Address32Bits) {
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Context->Eip += MOD32 [Mod];
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if (Mod == 0 && rm == 5) {
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// disp 32
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Context->Eip += 4;
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}
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//
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// If SIB byte, read it
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//
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if (rm == 4) {
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ibyte = NpxNpReadCSEip(Context);
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if (Mod == 0 && (ibyte & 7) == 5) {
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// disp 32
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Context->Eip += 4;
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}
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}
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} else {
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Context->Eip += MOD16 [Mod];
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if (Mod == 0 && rm == 6) {
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// disp 16
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Context->Eip += 2;
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}
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}
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}
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