Re: [PATCH] removal of "static foo = 0"

Pavel Machek
2000-11-26T23:12:37Z

Hi!

> Sorry, John, I _have_ to [give good example to others]. The above says
> that _you_ my dear friend, do not know where the BSS clearing code is. It
> is not in setup.S. It is not even in the same directory, where setup.S is.
> It is in arch/i386/kernel/head.S, starting from line 120:
>
> /*
> * Clear BSS first so that there are no surprises...
> */
> xorl %eax,%eax
> movl $ SYMBOL_NAME(__bss_start),%edi
> movl $ SYMBOL_NAME(_end),%ecx
> subl %edi,%ecx
> cld
> rep
> stosb
>
> ... speaking of which (putting asbesto on and hiding from Andries ;) can't
> we optimize this code to move words at a time and not bytes.... ;)

There's better way: put bss clearing code at beggining of .C code and
do it with memset. [x86-64 does it this way.] It is both more obvious
[no assembly] and faster [memset is optimized].
Pavel

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