Commit 6506b471 authored by Tom Musta's avatar Tom Musta Committed by Benjamin Herrenschmidt
Browse files

powerpc: Fix Unaligned Loads and Stores 



This patch modifies the unaligned access routines of the sstep.c
module so that it properly reverses the bytes of storage operands
in the little endian kernel kernel.   This is implemented by
breaking an unaligned little endian access into a combination of
single byte accesses plus an overal byte reversal operation.

Signed-off-by: default avatarTom Musta <tmusta@gmail.com>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 630c8a5f

arch/powerpc/lib/sstep.c

+45 −0
Original line number Diff line number Diff line
@@ -212,11 +212,19 @@ static int __kprobes read_mem_unaligned(unsigned long *dest, unsigned long ea, 
{

	int err;

	unsigned long x, b, c;

#ifdef __LITTLE_ENDIAN__

	int len = nb; /* save a copy of the length for byte reversal */

#endif



	/* unaligned, do this in pieces */

	x = 0;

	for (; nb > 0; nb -= c) {

#ifdef __LITTLE_ENDIAN__

		c = 1;

#endif

#ifdef __BIG_ENDIAN__

		c = max_align(ea);

#endif

		if (c > nb)

			c = max_align(nb);

		err = read_mem_aligned(&b, ea, c);
@@ -225,7 +233,24 @@ static int __kprobes read_mem_unaligned(unsigned long *dest, unsigned long ea, 
		x = (x << (8 * c)) + b;

		ea += c;

	}

#ifdef __LITTLE_ENDIAN__

	switch (len) {

	case 2:

		*dest = byterev_2(x);

		break;

	case 4:

		*dest = byterev_4(x);

		break;

#ifdef __powerpc64__

	case 8:

		*dest = byterev_8(x);

		break;

#endif

	}

#endif

#ifdef __BIG_ENDIAN__

	*dest = x;

#endif

	return 0;

}
@@ -273,9 +298,29 @@ static int __kprobes write_mem_unaligned(unsigned long val, unsigned long ea, 
	int err;

	unsigned long c;



#ifdef __LITTLE_ENDIAN__

	switch (nb) {

	case 2:

		val = byterev_2(val);

		break;

	case 4:

		val = byterev_4(val);

		break;

#ifdef __powerpc64__

	case 8:

		val = byterev_8(val);

		break;

#endif

	}

#endif

	/* unaligned or little-endian, do this in pieces */

	for (; nb > 0; nb -= c) {

#ifdef __LITTLE_ENDIAN__

		c = 1;

#endif

#ifdef __BIG_ENDIAN__

		c = max_align(ea);

#endif

		if (c > nb)

			c = max_align(nb);

		err = write_mem_aligned(val >> (nb - c) * 8, ea, c);