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Title: simply lea question
Post by: mineiro on December 03, 2011, 05:07:50 AM

Hello Sr's, I'm confused now about lea, I read StrLen.asm and have the line below:

lea ecx, [edi-01010101h] ; subtract 1 from each byte
generated listing give me:
8D 8B FEFEFEFF lea ecx, [ebx-01010101H]

olly reports:
Address Hex dump Command Comments
00401011 |. 8D8B FFFEFEFE LEA ECX,[EBX+FEFEFEFF]

why that FF?

should be?:
lea ecx, [edi-01010102h] ; subtract 1 from each byte
8D 8B FEFEFEFE lea ecx, [ebx-01010102H]

CPU Disasm - olly reports
Address Hex dump Command Comments
00401011 |. 8D8B FEFEFEFE LEA ECX,[EBX+FEFEFEFE]

the same to poasm.

Title: Re: simply lea question
Post by: MichaelW on December 03, 2011, 05:25:26 AM

Code Select


include \masm32\include\masm32rt.inc
.code
start:
    print hex$(-01010101h),13,10
    inkey
    exit
end start

Code Select

FEFEFEFF

Title: Re: simply lea question
Post by: mineiro on December 03, 2011, 09:11:09 AM

Thank you for the answer Sr MichaelW, I was tired when have posted, a simple 2 complement.
well, I need stop working a bit,

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General Forums => The Campus => Topic started by: mineiro on December 03, 2011, 05:07:50 AM