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libdasm's Issues

libdasm and multy-byte nop

From [email protected] on February 05, 2014 17:03:15

libdasm can't disassemble multy-byte nop and give wrong output.

Original issue: http://code.google.com/p/libdasm/issues/detail?id=2

libdasm misinterprets JLE

From [email protected] on January 23, 2014 17:57:15

This is regarding a bug in libdasm library. I've noticed that libdasm misinterprets a specific instruction.(JLE)

Sample Opcode :

'\x39\x56\x38\x0F\x8E\x1E\x01\x00\x00\x8B\xBD\xE4\xEB\xFF\xFF'

Actual dis-assembly of above opcodes :

00433441 |. 3956 38 CMP DWORD PTR DS:[ESI+38],EDX
00433444 |. 0F8E 1E010000 JLE 0x00433568
0043344A |> 8BBD E4EBFFFF MOV EDI,DWORD PTR SS:[EBP-141C]

libdasm output:

debasish@debasish ~/Downloads/libdasm-beta/examples $ hexdump test.bin
0000000 5639 0f38 1e8e 0001 8b00 e4bd ffeb 00ff
000000f
debasish@debasish ~/Downloads/libdasm-beta/examples $ ./das test.bin
00000000 395638 cmp [esi+0x38],edx
00000003 0f8e1e010000 jng 0x127
00000009 8bbde4ebffff mov edi,[ebp-0x141c]
debasish@debasish ~/Downloads/libdasm-beta/examples $

You can see, in third line libdasm misinterprets the jle (Jump if less or equal ) instruction to jng (Jump if not greater).

cheers,
Debasish

Attachment: libdasm_bug.py

Original issue: http://code.google.com/p/libdasm/issues/detail?id=1