tree 3a7208a2a8c47bdd263c16df4b5c77eb64d251df
parent 17d8428e4c911f7877d8470bca7a09a4b2aa2d57
author Linus Torvalds <torvalds@linux-foundation.org> 1316118513 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1316118513 -0700

asm alternatives: remove incorrect alignment notes

On x86-64, they were just wasteful: with the explicitly added (now
unnecessary) padding, the size of the alternatives structure was 16
bytes, and an alignment of 8 bytes didn't hurt much.

However, it was still silly, since the natural size and alignment for
the structure is actually just 12 bytes, 4-byte aligned since commit
59e97e4d6fbc ("x86: Make alternative instruction pointers relative").
So removing the padding, and removing the extra alignment is just a good
idea.

On x86-32, the alignment of 4 bytes was correct, but was incorrectly
hardcoded as 8 bytes in <asm/alternative-asm.h>.  That header file had
used to be an x86-64 only header file, but various unification efforts
have made it be used for x86-32 too (ie the unification of rwlock and
rwsem).

That in turn caused x86-32 boot failures, because the extra alignment
would result in random zero-filled words in the altinstructions section,
causing oopses early at boot when doing alternative instruction
replacement.

So just remove all the alignment noise entirely.  It's wrong, and it's
unnecessary.  The section itself is already properly aligned by the
linker scripts, and all additions to the section had better be of the
proper 12-byte format, keeping it aligned.  So if the align directive
were to ever make a difference, that would be an indication of a serious
bug to begin with.

Reported-by: Werner Landgraf <w.landgraf@ru.r>
Acked-by: Andrew Lutomirski <luto@mit.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>