debug source（调试器源代码）

1. About This is a clone of the MS-DOS DEBUG command. Some minor things aren't implemented. OTOH it has many features not available in the original MS DEBUG. For details see below. 2. Files Overview The files in this distribution are: debug.com the executable binary. debugx.com a DPMI aware version of debug. debxxvdd.dll a Win32 dll (VDD) loaded if debugx runs in a Windows XP NTVDM "DOS box". Makes debugx's L and W command work with sectors on this platform. debug.asm Assembler source code for DEBUG. Assemble with Masm or JWasm. debugtbl.inc include file for debug.asm, generated by mktables. instr.* data files on the instruction set. mktables.c C program to compile the internal instruction-set tables into source file debugtbl.inc. It runs under Linux or Turbo C (version 2.0, at least). Open Watcom v1.5 WCC works as well. readme.txt this file. debug.txt a DEBUG tutorial originally written by Michael Webster, extended to describe all additional features of FD DEBUG. SAMPLES contains samples of 16 and 32-bit DPMI clients in Masm and Nasm syntax. 3. Missing/Added Features a. The following are not implemented: - Loading of .HEX files. b. This debugger extends the MS-DOS version in the following ways: - The assembler and disassembler support all publicly documented instructions for Intel chips through the Pentium Pro (P6), except for the MMX instructions. The assembler and disassembler inform you if any instruction is inappropriate for the current processor. - FPU Opcodes are supported. - The current processor (for the purposes of assembler and disassembler warnings, above) can be declared to be something else via the following commands: m [x] set current processor. x=0 current processor is 8088. x=1..6 current processor is 80x86. 80586 is a Pentium and 80686 is a Pentium Pro. no argument = print current CPU/FPU types. mc [2|N] set math coprocessor. 2 = math coprocessor is a 287 (only valid if current processor is a 386). N = math coprocessor is absent no argument = math coprocessor is present - 'r register [value]' accepts 32-bit register names (for cpu 80386+). - You can do `r cx 1234' instead of having to put the `1234' on a separate line. - 'rn' displays FPU register status (currently for cpu 80386+ only) Just the raw hex values of the registers are displayed, though. - 'rx' switches among 8086 and 80386 register display (for cpu 80386+). - When doing `debug < file', debug will not hang if it reaches an end of file before encountering a `q' command. - This debugger saves and restores the program's Control-C and critical error interrupts, providing for better isolation between the debugger and the program being debugged. - 'tm 0|1' sets trace command mode, 0 = process INTs (default), 1 = single-step INTs (the MS-DOS Debug compatible mode). - 'xr' allows to reallocate an EMS handle and 'xa' allows to allocate an "empty" EMS handle (with zero pages) - but only if an EMM v4.0 is present. - Besides 'i' and 'o' exist the variations 'iw', 'id', 'ow' and 'od' to read/write a WORD or DWORD value from/to a port [DWORD values require a 80386+ cpu]. - 'h' can handle dword values. - register names can be used anywhere where a number is expected as input. That is, things like "u cs:ip" do work. - 'dm' displays the DOS memory control block (MCB) chain and the current PSP. - if DOS has set its InDOS flag, DEBUG will avoid to use int 21h internally, which allows to single-step through DOS code. - 'd', 't' and 'u' are automatically repeated if a blank line is entered. c. A DPMI aware version of the debugger, DEBUGX, is available, with the following additional features: - besides real-mode applications it can debug both 16-bit and 32-bit DPMI clients. [To debug DPMI clients a DPMI host has to be installed. Tested with cwsdpmi, hdpmi, WinXP NTVDM, 32rtm. In DosEmu and Windows 95/98/ME DOS boxes it is required to single-step through the initial switch to protected-mode, else DEBUGX will loose control of the debuggee.] - 'dl': display LDT descriptor(s) (in protected-mode only) - 'di': display interrupt vector(s) - 'dx': display extended memory (read via Int 15h, ah=87h). Requires a 80386 cpu. 'dx' is automatically repeated if a blank line is entered. - 'rn' displays FPU registers in "readable" format. - when running in a Windows XP DOS bos, DEBUGX will try to load and use DEBXXVDD.DLL. This DLL will allow DEBUGX to successfully execute its low-level disk access commands L and W in this OS - if the user has administrator rights. DEBXXVDD.DLL is public domain, the source can be downloaded from http://www.japheth.de/Download/debxxvdd.zip. Please be aware that you can do severe damage to your disk data if you use those low-level functions without knowing what you are doing. 4. History 0.95e [11 January 2003] Fixed a bug in the assember. 0.95f [10 September 2003] Converted to NASM; fixed some syntax incompatibilities. 0.98 [27 October 2003] Added EMS commands and copyright conditions. ------- changes below were done by me, japheth 0.99 [27 Septemb 2006] - bugfix: IF was not displayed correctly. - FS and GS registers displayed if cpu is 80386+. - RX displays the standard 32bit registers. - R register [value] understands the standard 32bit registers. 0.99a [28 Septemb 2006] - bugfix: JECXZ had wrong prefix (66h, should be 67h). - A and D understand the 32bit opcodes LOOP(Z|NZ|E|NE)D. 0.99b [29 Septemb 2006] - L and W now work with FAT32 drives. 0.99c [29 Septemb 2006] - RX changed. Now it toggles 16/32 bit register dump. - RN displays floating point register status. 0.99d [02 October 2006] - bugfix: RN displayed error-pointer registers wrong. 0.99e [12 October 2006] - XR command added to reallocate EMS handle. - XA command allows to allocate zero pages on EMS 4.0. - TM [0|1] added to be able to switch T to the ms-dos debug compatible behaviour (that is, T jumps into 'INT xx'). 0.99f [17 October 2006] - debug's EMS functions may work even with a "hidden" EMM. - bugfix: display of mappable pages didn't account for amount of these pages == 0. 0.99g [25 October 2006] - bugfix: U was unable to recognise [ESP] related memory operands (i.e. mov eax,[esp]). 0.99h [07 November 2006] - bugfix: R trying to display content of effective address has caused a GPF in v86-mode if this address was FFFFh of FFFDh. - IW, ID, OW and OD implemented. 0.99i [14 November 2006] - bugfix: a child PSP was created but not terminated, causing files not to be closed. It became obvious if stdin and/or stdout were redirected to files ("C:\>DEBUG >yyy") 0.99j [16 November 2006] - bugfix: using T if current instruction is an INT xx (and trace mode == 0) stopped debuggee one instruction *after* the INT (due to a x86 design weakness). - bugfix: the 0.99i bugfix had some problems on FreeDOS. 1.00 [25 November 2006] - bugfix: debuggee's psp was saved after program load only, but this has to