[PATCH 2/3] powerpc: Fix Unaligned Loads and Stores
From: Tom Musta <hidden>
Date: 2013-10-18 19:42:13
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
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 <redacted> --- arch/powerpc/lib/sstep.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 45 insertions(+), 0 deletions(-)
diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index 5e0d0e9..570f2af 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c@@ -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);
--
1.7.1