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Guy
Expert Cheater
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Joined: 30 May 2009
Posts: 187
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 Posted: Sat Aug 29, 2009 1:23 am Post subject: Inline ASM x64 |
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Since Microsoft has dropped inline ASM support for their x64 compilers, are there any other suggested workarounds for "re-adding" inline ASM support?
Intrinsics are lacking, externally linking against .ASM files doesn't work if you need something *inlined*. I could modify the program during runtime to hard-code in what I want, but I prefer a less dynamic solution, that wouldn't cost me every single runtime.
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Slugsnack
Grandmaster Cheater Supreme
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Joined: 24 Jan 2007
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| Posted: Sat Aug 29, 2009 3:59 am Post subject: |
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| afaik you're going to have to make do with intrinsics
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Guy
Expert Cheater
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Posts: 187
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| Posted: Sat Aug 29, 2009 10:43 am Post subject: |
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| Slugsnack wrote: | | afaik you're going to have to make do with intrinsics |
I've come up with the idea of adding my own, pseudo-reassembler, which will replace specially-formatted instructions in your application after the linker pulls your app together.
e.g
| Code: |
*( ( ( unsigned char ** ) "\x92\x91" ) )[0] = 0;
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Generates..
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0040100A |. C600 00 MOV BYTE PTR DS:[EAX],0
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The pseudo-reassembler would replace the above with:
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0040100A 60 PUSHAD
0040100B 90 NOP
0040100C 90 NOP
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EDIT:
I'm expanding on the idea of using a script to replace specially-marked places in memory to represent what should be turned into blocks of ASM.
e.g.:
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#define __pushad( ) *( ( ( unsigned char ** ) "\x60\xFF\x00" ) )[0] = 0
#define __popad( ) *( ( ( unsigned char ** ) "\x61\xFF\x00" ) )[0] = 0
#ifdef _M_IX86
#define __popEAX( ) *( ( ( unsigned char ** ) "\x58\xFF\x00" ) )[0] = 0
#elif _M_X64
#define __popRAX( ) *( ( ( unsigned char ** ) "\x58\xFF\x00" ) )[0] = 0
#endif
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The "reassembler" script, to be ran after the compiling and linking process:
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#!/usr/bin/python
raw_size = 0x200
raw_offset = 0x400
f = open( "emit.exe", "rb" )
data = f.read( )
f.close( )
# Load anything before the code segment
new_data = data[:raw_offset]
cs = ""
cs += data[raw_offset:][:0x200]
### BEGIN CODE SEGMENT ###
#pushad
cs = cs.replace( "\xA2\x60\xFF\x00\x00", "\x60\x90\x90\x90\x90" )
#popad
cs = cs.replace( "\xA2\x61\xFF\x00\x00", "\x61\x90\x90\x90\x90" )
#pop EAX/pop RAX
cs = cs.replace( "\xA2\x58\xFF\x00\x00", "\x58\x90\x90\x90\x90" )
### END CODE SEGMENT ###
new_data += cs
# Load the data after the code segment
new_data += data[raw_offset+raw_size:]
f = open( "emit-new.exe", "wb" )
f.write( new_data )
f.close( )
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Of course, this technique could easily be adapted to allow users to emit bytes into the CPU stream, accomplishing the same effect as inline ASM.
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