Linux 64-bit. Why is this out-of-range?

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system error

Joined: 01 Sep 2013
Posts: 670

system error 28 Oct 2014, 08:51

I tried this simple code

Code:

format ELF64 executable

mov     rdi,[m]
and     rdi,7FFFFFFFFh ;error: value out of range
call    exit

m dq 56

Am I missing something here?

28 Oct 2014, 08:51

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20430
Location: In your JS exploiting you and your system

revolution 28 Oct 2014, 08:58

The x86 instructions can't encode the constant 2^35-1 with the AND.

You can use "mov rax,0x7ffffffff" and "and rdi,rax".

Or did you mean 2^31-1 i.e. 0x7fffffff?

28 Oct 2014, 08:58

system error

Joined: 01 Sep 2013
Posts: 670

system error 28 Oct 2014, 09:12

revolution wrote:

The x86 instructions can't encode the constant 2^35-1 with the AND.
You can use "mov rax,0x7ffffffff" and "and rdi,rax".

Ok. That helps.
Plus, probably no such thing as AND R64,IMM64 in 64-bit mode anyway.

p/s: Server is too slow. I don't know, could be my internet quota limit as well.

28 Oct 2014, 09:12

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