Messages in this thread |  | | Date | Fri, 24 Nov 2000 07:47:53 +0000 | From | Pavel Machek <> | Subject | Re: [PATCH] removal of "static foo = 0" |
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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
-- Philips Velo 1: 1"x4"x8", 300gram, 60, 12MB, 40bogomips, linux, mutt, details at http://atrey.karlin.mff.cuni.cz/~pavel/velo/index.html.
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