Re: [git pull] "big box" x86 changes, boot protocol

[Jeremy Fitzhardinge <jeremy@goop.org>]

Andrew Morton wrote:
>> +	memcpy(&early_res[i], &early_res[i + 1],
>> +	       (j - 1 - i) * sizeof(struct early_res));
>>     
>
> nit: memcpy() shouldn't be used for overlapping copies.  It happens to be
> OK (for dst<src) in the kernel implementations.  We hope.
>   

Definitely shouldn't be assumed.  At one point in the distant past I had 
a ppc memcpy which would clobber a destination cacheline before reading 
the source, so source and dest within a cacheline's distance would be 
trouble, regardless of the direction.  Arch-specific code which knows 
about the arch-specific details of memcpy might be safer, I guess, but 
its still fairly brittle.

    J