Commit 230aef7a authored Aug 07, 2013 by Anton Blanchard Committed by Benjamin Herrenschmidt Aug 14, 2013

powerpc: Handle unaligned ldbrx/stdbrx



Normally when we haven't implemented an alignment handler for
a load or store instruction the process will be terminated.

The alignment handler uses the DSISR (or a pseudo one) to locate
the right handler. Unfortunately ldbrx and stdbrx overlap lfs and
stfs so we incorrectly think ldbrx is an lfs and stdbrx is an
stfs.

This bug is particularly nasty - instead of terminating the
process we apply an incorrect fixup and continue on.

With more and more overlapping instructions we should stop
creating a pseudo DSISR and index using the instruction directly,
but for now add a special case to catch ldbrx/stdbrx.

Signed-off-by: Anton Blanchard <anton@samba.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

parent 5b63fee1

arch/powerpc/kernel/align.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -764,6 +764,16 @@ int fix_alignment(struct pt_regs *regs)
		nb = aligninfo[instr].len;
		flags = aligninfo[instr].flags;

		/* ldbrx/stdbrx overlap lfs/stfs in the DSISR unfortunately */
		if (IS_XFORM(instruction) && ((instruction >> 1) & 0x3ff) == 532) {
		nb = 8;
		flags = LD+SW;
		} else if (IS_XFORM(instruction) &&
		((instruction >> 1) & 0x3ff) == 660) {
		nb = 8;
		flags = ST+SW;
		}

		/* Byteswap little endian loads and stores */
		swiz = 0;
		if (regs->msr & MSR_LE) {

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