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powerpc: Fix Unaligned Loads and Stores

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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>
This commit is contained in:
Tom Musta 2013-10-18 14:42:08 -05:00 • committed by Benjamin Herrenschmidt
parent 630c8a5fc9
commit 6506b4718b
1 changed files with 45 additions and 0 deletions
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45
arch/powerpc/lib/sstep.c
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@ -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);