Re: how to add read/write data breakpoint?
Posted on 2021-04-26, 08:47
btw: i've got massive problems under VS2019 to debug the debugger itself - the dosbox or windows at whole is blocking very hard, mouse is invisble, etc. any tips to handle that?
Re: how to add read/write data breakpoint?
Posted on 2021-04-24, 08:02
just to be clear: i know that tracking memory reads can be very very very ... slow and that it will work only for core=normal
Re: how to add read/write data breakpoint?
Posted on 2021-04-22, 15:30
my second patch to svn 4448 added brakepoint at the hello world string with "BPMR 1dd:108 1" but it seems that my read-checks do not reach the string bytes - do i still miss some read functions? core=normal
Re: how to add read/write data breakpoint?
Posted on 2021-04-22, 09:52
i think i've found a way to get a host ptr from the location in my Find-Routine - but is that always the correct way or do i need to work with the get_tlb_read stuff like in the mem_readX_inline functions? CBreakpoint* CBreakpoint::FindMemReadBreakpoint(Bit8u const* const addr, Bit32u range) { std:: …
Re: DOSBox debugger
Posted on 2021-04-22, 07:17
Akuma wrote on 2020-06-03, 08:16: I would like to set a breakpoint on memory reads . That's the only thing I really miss. i try to implement that feature: how to add read/write data breakpoint? maybe you can have a look and help with the idea/implementation
Re: how to add read/write data breakpoint?
Posted on 2021-04-22, 07:00
seeking for help: attached is a WIP/Compilable but not working patch based on svn 4447 that shows my ideas how to hopefully cleanly add a memory read breakpoint feature to heavy-debug mode there is a new function DEBUG_CheckMemReadBreakpoint that gets called from (nearly) every memory reading …
Re: how to add read/write data breakpoint?
Posted on 2021-04-20, 14:42
and i think it will be only available for normal core mode
Re: how to add read/write data breakpoint?
Posted on 2021-04-19, 14:37
what i think so far what is needed dosbox\include\mem.h extend the host_reads like this (also for word,dword and WORDS_BIGENDIAN/C_UNALIGNED_MEMORY) static INLINE Bit8u host_readb( HostPt off ) { #ifdef C_HEAVY_DEBUG // check for mem-read-bp in range and activate bp if hit #endif return off[0]; } i …
how to add read/write data breakpoint?
Posted on 2021-04-17, 06:46
years ago i've added a feature for break point on memory read(write) ranges, slow and only available in heavy-debug mode something likes these commands BSMR seg:ofs range // detect reads BSMW seg:ofs range // detect writes BSRMW seg:ofs range // detect reads and writes but i've accidentally deleted …
Re: Using debug.exe and experimenting with x86 instructions in DOSBox
Posted on 2020-02-14, 15:08
A question: how does the CPU handle far calls in realmode? When e.g. an .exe file contains say "call far abdc:1234" does that mean the program will literally jump to that exact spot or is that what relocation items are for? every loading segment related data/code (jumps,call,offset,etc.) are …
Re: Using debug.exe and experimenting with x86 instructions in DOSBox
Posted on 2020-02-14, 12:15
Does the DOSBox debugger allow you to feed it a few instructions and execute them? no but as stated you can use a Visual Studio Debugger + simple x86 C/C++ Project for that (if VStudio is around) int main() { __asm { mov al, 2 mov dx,0xD007 add dx, al } return 0; } but maybe debug.exe fits already …
Re: Using debug.exe and experimenting with x86 instructions in DOSBox
Posted on 2020-02-14, 05:14
Looking for a way to quickly test the effect of x86 instructions 1. you can use visual studio with x86 inline assembler - works as long as segmented memory access or io ports access is not relevant to you, all 8/16/32bit opcodes still working 2. use Turbo/Borland C/C++ in Dosbox with Inline- …
Re: Ways to dump memory to a file->
Posted on 2020-02-09, 18:58
@Peter Swinkels reverse engineering is one of the stronges topics in software development - its very complicated and time consuming - you can spend month only on Alley Cats analysis (btw: someone does that already: https://github.com/gabonator/Work-in-progress/tree/master/DosGames/AlleyCat) 1. …
Re: repne/repnz movsw: Invalid instruction prefix mystery
Posted on 2019-08-21, 07:52
jmars seems to be right: https://c9x.me/x86/html/file_module_x86_id_279.html
Re: trouble with a program: cup386
Posted on 2019-08-20, 11:12
normal core?
Re: repne/repnz movsw: Invalid instruction prefix mystery
Posted on 2019-08-20, 11:12
thx for the help
Re: repne/repnz movsw: Invalid instruction prefix mystery
Posted on 2019-08-20, 09:52
so i think replacing repne/repnz on movs with rep would be the correct asm code for masm resulting in the same behavior but i will stay with db 0f2h, 0a5h for beeing binary equal 😀
Re: repne/repnz movsw: Invalid instruction prefix mystery
Posted on 2019-08-20, 09:28
MASM got the /Zm option for maximum Masm 5.1 compatiblity (that worked with former MASM version i think) - its shown using /? but it seems not to work - still the error USAM got the -Zm option but also do not seems to supress the error thx for the info: i will use a REPNE_MOVS macro in all places to …
Re: trouble with a program: cup386
Posted on 2019-08-20, 06:24
for unpacking old dos executables what executables - maybe someone know already how to unpack them no idea (cup386 don't seem to like EMM386) - but have you tried UNP from http://unp.bencastricum.nl/ - well known, works under dosbox and maybe able to unpack you exe
repne/repnz movsw: Invalid instruction prefix mystery
Posted on 2019-08-20, 06:04
im currently reverse engineering a small DOS 16bit program and stumbled over invalid prefix combinations comming out of IDA/ndisasm when using MASM to assemble it back to code TASM and NASM have no problem to assemble these instructions - but MASM/UASM failing im currious what is the correct code …
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