Re: somebody dropped a (warning) bomb

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Feb 9 2007 08:16, linux-os (Dick Johnson) wrote:
>On Fri, 9 Feb 2007, Jan Engelhardt wrote:
>> On Feb 8 2007 16:42, Linus Torvalds wrote:
>>>
>> Further, giving again answer to the question whether they generate
>> signed or unsigned comparisons: Have you ever seen a computer which
>> addresses memory with negative numbers? Since the answer is most likely
>> no, signed comparisons would
>
>Yes, most all do. Indexed memory operands are signed displacements. See
>page 2-16, Intel486 Microprocessor Programmer's Reference Manual. This

I was referring to "absolute memory", not the offset magic that assembler
allows. After all, (reg+relativeOffset) will yield an absolute address.
What I was out at: for machines that have more than 2 GB of memory, you
don't call the address that is given by 0x80000000U actually "byte
-2147483648", but "byte 2147483648".

>gets hidden by higher-level languages such as 'C'. It is also non-obvious
>when using the AT&T (GNU) assembly language. However, the Intel documentation
>shows it clearly:
> 			MOV	AL,  [EBX+0xFFFFFFFF]	; -1

It can be debated what exactly this is... negative offset or "using
overflow to get where we want".



Jan
-- 
ft: http://freshmeat.net/p/chaostables/
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux