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[PARISC] fix panic on prefetch(NULL) on PA7300LC

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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.

Cc: stable@vger.kernel.org
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
This commit is contained in:
James Bottomley 2012-05-16 11:10:27 +01:00
parent 207f583d71
commit b3cb867481
1 changed files with 6 additions and 1 deletions
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7
arch/parisc/include/asm/prefetch.h
View file

@ -21,7 +21,12 @@
#define ARCH_HAS_PREFETCH #define ARCH_HAS_PREFETCH
static inline void prefetch(const void *addr) 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. */ /* LDD is a PA2.0 addition. */