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Subject[ 06/55] PARISC: fix panic on prefetch(NULL) on PA7300LC
3.0-stable review patch.  If anyone has any objections, please let me know.

------------------
From: James Bottomley <JBottomley@Parallels.com>

commit b3cb8674811d1851bbf1486a73d62b90c119b994 upstream.

Due to an errata, the PA7300LC generates a TLB miss interruption even on the
prefetch instruction. This means that prefetch(NULL), which is supposed to be
a nop on linux actually generates a NULL deref fault. Fix this by testing the
address of prefetch against NULL before doing the prefetch.

Signed-off-by: James Bottomley <JBottomley@Parallels.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/parisc/include/asm/prefetch.h | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
--- a/arch/parisc/include/asm/prefetch.h
+++ b/arch/parisc/include/asm/prefetch.h
@@ -21,7 +21,12 @@
#define ARCH_HAS_PREFETCH
static inline void prefetch(const void *addr)
{
- __asm__("ldw 0(%0), %%r0" : : "r" (addr));
+ __asm__(
+#ifndef CONFIG_PA20
+ /* Need to avoid prefetch of NULL on PA7300LC */
+ " extrw,u,= %0,31,32,%%r0\n"
+#endif
+ " ldw 0(%0), %%r0" : : "r" (addr));
}

/* LDD is a PA2.0 addition. */



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