[PATCH 3.17 006/122] MIPS: asm: uaccess: Add v1 register to clobber list on EVA

From: Greg Kroah-Hartman
Date: Fri Dec 05 2014 - 18:51:02 EST

3.17-stable review patch. If anyone has any objections, please let me know.


From: Markos Chandras <markos.chandras@xxxxxxxxxx>

commit 58563817cfed0432e9a54476d5fc6c3aeba475e4 upstream.

When EVA is turned on and prefetching is being used in memcpy.S,
the v1 register is being used as a helper register to the PREFE
instruction. However, v1 ($3) was not in the clobber list, which
means that the compiler did not preserve it across function calls,
and that could corrupt the value of the register leading to all
sorts of userland crashes. We fix this problem by using the
DADDI_SCRATCH macro to define the clobbered register when

Signed-off-by: Markos Chandras <markos.chandras@xxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Patchwork: https://patchwork.linux-mips.org/patch/8510/
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/mips/include/asm/uaccess.h | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

--- a/arch/mips/include/asm/uaccess.h
+++ b/arch/mips/include/asm/uaccess.h
@@ -773,10 +773,11 @@ extern void __put_user_unaligned_unknown
"jal\t" #destination "\n\t"

-#define DADDI_SCRATCH "$0"
+#if defined(CONFIG_CPU_DADDI_WORKAROUNDS) || (defined(CONFIG_EVA) && \
#define DADDI_SCRATCH "$3"
+#define DADDI_SCRATCH "$0"

extern size_t __copy_user(void *__to, const void *__from, size_t __n);

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