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gid2525
Expert Cheater
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Joined: 21 Oct 2013
Posts: 101
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 Posted: Wed Feb 17, 2021 3:28 am Post subject: Major BUGS with operations in FPU stack Breakpoints (7.2) |
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FPU operations in the stack don't get reported properly during a break and trace. Also when stepping into after a few steps. Like for instance if I were to break and trace some time before here:
fld dword ptr [2979B740]
fstp dword ptr [ebp-30]
mov eax,esi
fld dword ptr [ebp-20]
fstp dword ptr [ebp-54]
fld dword ptr [ebp-54]
frndint
fstp qword ptr [ebp-18]
movsd xmm0,[ebp-18]
The [ebp-30], [ebp-20], [ebp-54], [ebp-18], etc. All will show 0.00. Which is certainly NOT the case as I used x32dbg just fine (I actually had to because Cheat engine wouldn't show me the FPU stack amounts).
PeaceBeUponYou in the cheatthegame discord was also talking about it mentions:
"most of the processes (games) mask FPU arithmetic exception, that is why they do not crash"
"but doing it in CEs Tutorial will tell u that an exception (like division by 0) was caused"
Basically its been a bug for a while. It would be nice to get it fixed.
Thanks!
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Dark Byte
Site Admin
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Joined: 09 May 2003
Posts: 25804
Location: The netherlands
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| Posted: Wed Feb 17, 2021 3:59 am Post subject: |
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I can't reproduce it..
I tried with this AA script
| Code: |
alloc(bla,1024)
alloc(val,4)
alloc(store,4)
alloc(stck,88)
val:
dd #100
stck:
dd (float)1
dd (float)2
dd (float)3
dd (float)4
dd (float)5
dd (float)6
dd (float)7
dd (float)8
dd (float)9
dd (float)10
dd (float)11
dd (float)12
dd (float)13
dd (float)14
dd (float)15
dd (float)16
dd (float)17
dd (float)18
dd (float)19
dd (float)20
dd (float)21
dd (float)22
bla:
push ebp
lea ebp,[stck+54]
fild [val]
fstp [store]
fld dword ptr [store]
fstp dword ptr [ebp-30]
mov eax,esi
fld dword ptr [ebp-20]
fstp dword ptr [ebp-54]
fld dword ptr [ebp-54]
frndint
fstp qword ptr [ebp-18]
movsd xmm0,[ebp-18]
pop ebp
ret
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have you set the field to show FPU registers instead of XMM registers?
| Description: |
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| Filesize: |
100.82 KB |
| Viewed: |
1855 Time(s) |
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| Description: |
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| Filesize: |
110.87 KB |
| Viewed: |
1855 Time(s) |
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MMM-304
Expert Cheater
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Joined: 17 Aug 2020
Posts: 170
Location: Milkey Way
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| Posted: Wed Feb 17, 2021 10:52 am Post subject: |
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Its true. Debugging FPU instruction (especially arithmetic operation on values from 0.1-1 ) just corrupts data.
@DB try these
| Code: |
push (float)100
push (float)200
push (float)300
push (float)400
fld [esp]
fld [esp+4]
fld [esp+8]
fld [esp+C]
// you will see that after 2 flds the third one corrupts x87FPU stack and declears it as "Empty"
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also operations like fpatan , fdiv , fmul all do
BIG NOTE: These are visible during single stepping (or with break and trace form)
using fld/fild and quickly fstp/fistp doesnt show any error. tho fst will (cuz its not poped  )
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gid2525
Expert Cheater
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Joined: 21 Oct 2013
Posts: 101
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| Posted: Wed Feb 17, 2021 11:53 am Post subject: |
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| MMM-304 wrote: | Its true. Debugging FPU instruction (especially arithmetic operation on values from 0.1-1 ) just corrupts data.
@DB try these
| Code: |
push (float)100
push (float)200
push (float)300
push (float)400
fld [esp]
fld [esp+4]
fld [esp+8]
fld [esp+C]
// you will see that after 2 flds the third one corrupts x87FPU stack and declears it as "Empty"
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also operations like fpatan , fdiv , fmul all do
BIG NOTE: These are visible during single stepping (or with break and trace form)
using fld/fild and quickly fstp/fistp doesnt show any error. tho fst will (cuz its not poped ) |
YAASS. PLEASE FIX! This just kills trying to debug/trace FPU stuff. Thanks!
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Dark Byte
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Joined: 09 May 2003
Posts: 25804
Location: The netherlands
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| Posted: Wed Feb 17, 2021 2:06 pm Post subject: |
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you forgot to mention which debugger interface you use.
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gid2525
Expert Cheater
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Joined: 21 Oct 2013
Posts: 101
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| Posted: Wed Feb 17, 2021 2:57 pm Post subject: |
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| Dark Byte wrote: | | you forgot to mention which debugger interface you use. |
I'm using the VEH debugger..is that what you mean? DVBM won't work for me anyway cause AMD Ryzen 9 3900X. But I would prefer the VEH gets fixed of course 
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Dark Byte
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Joined: 09 May 2003
Posts: 25804
Location: The netherlands
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| Posted: Wed Feb 17, 2021 3:12 pm Post subject: |
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It's fixed in the sourcecode on github
The windows debugger interface doesn't have that issue, and the 32-bit CE version also doesn't have that issue with veh debug
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MMM-304
Expert Cheater
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Joined: 17 Aug 2020
Posts: 170
Location: Milkey Way
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| Posted: Thu Feb 18, 2021 6:22 am Post subject: |
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hmm..
I was using VEH on CE 64-bit that supports SSE4-AVX instruction sets as well
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gid2525
Expert Cheater
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Joined: 21 Oct 2013
Posts: 101
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| Posted: Fri Feb 19, 2021 8:56 am Post subject: |
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| Dark Byte wrote: | It's fixed in the sourcecode on github
The windows debugger interface doesn't have that issue, and the 32-bit CE version also doesn't have that issue with veh debug |
Yea I use the cheatengine-x86_64-SSE4-AVX2.exe file.. Did you fix that one? Im not sure how to compile it or where on the github pag 
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Dark Byte
Site Admin
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Joined: 09 May 2003
Posts: 25804
Location: The netherlands
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| Posted: Fri Feb 19, 2021 9:17 am Post subject: |
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next version is fixed
just use cheatengine-i386.exe for now if you target a 32 bit process
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Do not ask me about online cheats. I don't know any and wont help finding them.
Like my help? Join me on Patreon so i can keep helping |
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gid2525
Expert Cheater
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Joined: 21 Oct 2013
Posts: 101
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| Posted: Fri Feb 19, 2021 11:25 am Post subject: |
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| Dark Byte wrote: | next version is fixed
just use cheatengine-i386.exe for now if you target a 32 bit process |
Ah, you mean 7.3? Do you have an eta for that? Just curious. Thanks!
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