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: Tom Musta <tmusta@gmail.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index b1faa15..0121d21 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -212,11 +212,19 @@
{
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 @@
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 @@
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);