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author | Michael Neuling <mikey@neuling.org> | 2009-04-01 18:02:42 +0000 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-01-18 10:34:01 -0800 |
commit | 816972c12bfc3a1a92a64bf0fba633501004e4c6 (patch) | |
tree | 16964dbe9204b19c4631fd1f961f3107aea8e658 /arch/powerpc/kernel/align.c | |
parent | 6f5195525e548d474a77ce00baa927e5c7ed6976 (diff) |
powerpc: Disable VSX or current process in giveup_fpu/altivec
commit 7e875e9dc8af70d126fa632446e967327ac3fdda upstream.
When we call giveup_fpu, we need to need to turn off VSX for the
current process. If we don't, on return to userspace it may execute a
VSX instruction before the next FP instruction, and not have its
register state refreshed correctly from the thread_struct. Ditto for
altivec.
This caused a bug where an unaligned lfs or stfs results in
fix_alignment calling giveup_fpu so it can use the FPRs (in order to
do a single <-> double conversion), and then returning to userspace
with FP off but VSX on. Then if a VSX instruction is executed, before
another FP instruction, it will proceed without another exception and
hence have the incorrect register state for VSX registers 0-31.
lfs unaligned <- alignment exception turns FP off but leaves VSX on
VSX instruction <- no exception since VSX on, hence we get the
wrong VSX register values for VSX registers 0-31,
which overlap the FPRs.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'arch/powerpc/kernel/align.c')
0 files changed, 0 insertions, 0 deletions