releases/3.3.8/parisc-fix-panic-on-prefetch-null-on-pa7300lc.patch

   1 From b3cb8674811d1851bbf1486a73d62b90c119b994 Mon Sep 17 00:00:00 2001
   2 From: James Bottomley <JBottomley@Parallels.com>
   3 Date: Wed, 16 May 2012 11:10:27 +0100
   4 Subject: PARISC: fix panic on prefetch(NULL) on PA7300LC
   5
   6 From: James Bottomley <JBottomley@Parallels.com>
   7
   8 commit b3cb8674811d1851bbf1486a73d62b90c119b994 upstream.
   9
  10 Due to an errata, the PA7300LC generates a TLB miss interruption even on the
  11 prefetch instruction.  This means that prefetch(NULL), which is supposed to be
  12 a nop on linux actually generates a NULL deref fault.  Fix this by testing the
  13 address of prefetch against NULL before doing the prefetch.
  14
  15 Signed-off-by: James Bottomley <JBottomley@Parallels.com>
  16 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  17
  18 ---
  19  arch/parisc/include/asm/prefetch.h |    7 ++++++-
  20  1 file changed, 6 insertions(+), 1 deletion(-)
  21
  22 --- a/arch/parisc/include/asm/prefetch.h
  23 +++ b/arch/parisc/include/asm/prefetch.h
  24 @@ -21,7 +21,12 @@
  25  #define ARCH_HAS_PREFETCH
  26  static inline void prefetch(const void *addr)
  27  {
  28 -       __asm__("ldw 0(%0), %%r0" : : "r" (addr));
  29 +       __asm__(
  30 +#ifndef CONFIG_PA20
  31 +               /* Need to avoid prefetch of NULL on PA7300LC */
  32 +               "       extrw,u,= %0,31,32,%%r0\n"
  33 +#endif
  34 +               "       ldw 0(%0), %%r0" : : "r" (addr));
  35  }
  36
  37  /* LDD is a PA2.0 addition. */