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murder



Joined: 03 Nov 2011
Posts: 10
murder
When I try to compile code like this
Code:
mov qword[RegKey+14+rax],'\CLSID'     

I`ve got "value out of range" (in 64-bit mode)

but this
Code:
mov    rdx,'\CLSID' 
mov    qword[RegKey+14+rax],rdx    

still work

sorry for my english Embarassed
Post 03 Nov 2011, 17:01
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17270
Location: In your JS exploiting you and your system
revolution
You can't define a large constant like '\CLSID' with mov m64,imm.

See the Intel manual for operand bounds. The largest is this:
Intel manual wrote:
MOV r/m64,imm32
BTW: Are you aware that '\CLSID' is not a pointer to a memory location, but is in actually an immediate constant?
Post 03 Nov 2011, 18:20
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murder



Joined: 03 Nov 2011
Posts: 10
murder
Quote:
Intel manual wrote:
MOV r/m64,imm32


ok, thanks.

I didnt know about this restriction. Sorry.
Post 04 Nov 2011, 13:56
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Madis731



Joined: 25 Sep 2003
Posts: 2141
Location: Estonia
Madis731
CPUs limit instruction lengths to 15 bytes.
If 64-bit architecture would allow full 64-bit immediates then
MOV m64,imm64 could be inflated to 20 bytes by only using
Code:
mov qword[rax+rax*8+123456789ABCDEF0h],123456789ABCDEF0h    

I did a simple calculation from the following line that takes 12 bytes
Code:
mov qword[rax+rax*8+12345678h],12345678h    


Thx revolution!


Last edited by Madis731 on 07 Nov 2011, 19:23; edited 1 time in total
Post 07 Nov 2011, 18:35
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17270
Location: In your JS exploiting you and your system
revolution
Madis731 wrote:
CPUs limit instruction lengths to 16 bytes.
Erm ... 15 bytes, right?
Post 07 Nov 2011, 19:09
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17270
Location: In your JS exploiting you and your system
revolution
Madis731 wrote:
If 64-bit architecture would allow full 64-bit immediates then
MOV m64,imm64 could be inflated to 20 bytes by only using
Code:
mov dqword[rax+rax*8+123456789ABCDEF0h],123456789ABCDEF0h    

I did a simple calculation from the following line that takes 12 bytes
Code:
mov qword[rax+rax*8+12345678h],12345678h    
Do you mean:
Code:
mov qword[rax+rax*8+123456789ABCDEF0h],123456789ABCDEF0h    
dqword would be 128 bits!
Post 07 Nov 2011, 19:13
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Madis731



Joined: 25 Sep 2003
Posts: 2141
Location: Estonia
Madis731
Sorry, wasn't thinking straight. I was not referencing any documents like I should've done Smile and like I usually do. Fixed!
Post 07 Nov 2011, 19:25
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