Linus Torvalds view of Kernel ‘Voodoo’

“From Linus Torvalds <>
Date Tue, 9 Aug 2011 08:41:00 -0700
Subject Re: [PATCH] treewide: Update sha_transform

On Tue, Aug 9, 2011 at 1:58 AM, Joe Perches wrote: > >
Eliminate possible sha_transform unaligned accesses to data by
copying > data to an aligned __u32 array if necessary.

This is wrong. Not only does it double the stack space, when I
tried it for git it just made things slower. So don’t do it.

If some architecture has a bad “get_unaligned_be32()”, then
that’s just something for the arch maintainers to fix.

> Add sha_transform wipe argument to force workspace clearing
if desired.

I disagree. As already mentioned, any competent compiler would
make that thing go away anyway. And there is no reason to believe
that it’s actually a real fix for any real security issue, so it’s
voodoo programming for several reasons.

We shouldn’t do voodoo stuff. Or rather, I’m perfectly ok if you
guys all do your little wax figures of me in the privacy of your
own homes – freedom of religion and all that – but please don’t do
it in the kernel.

Linus

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