powerpc/32: Add warning on misaligned copy_page() or clear_page()

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copy_page() and clear_page() expect page aligned destination, and
use dcbz instruction to clear entire cache lines based on the
assumption that the destination is cache aligned.

As shown during analysis of a bug in BTRFS filesystem, a misaligned
copy_page() can create bugs that are difficult to locate (see Link).

Add an explicit WARNING when copy_page() or clear_page() are called
with misaligned destination.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=204371
Link: https://lore.kernel.org/r/c6cea38f90480268d439ca44a645647e260fff09.1565941808.git.christophe.leroy@c-s.fr

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Christophe Leroy 2019-08-16 07:52:20 +00:00 • committed by Michael Ellerman

parent f204338f8e

commit 7ab0b7cb89

2 changed files with 9 additions and 0 deletions

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4

arch/powerpc/include/asm/page_32.h

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5

arch/powerpc/kernel/misc_32.S

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