[src/trunk]: src/sys/arch/arm/include Modify __lwp_getprivate_fast to call _l...

[matt <matt%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/22b4917b7e7d
branches:  trunk
changeset: 773704:22b4917b7e7d
user:      matt <matt%NetBSD.org@localhost>
date:      Mon Feb 13 17:07:45 2012 +0000

description:
Modify __lwp_getprivate_fast to call _lwp_getprivate if the mrc instruction
returns 0 (some ARM cores are broken and don't raise an undefined exception
when encountering an unknown or privileged mrc instruction in user mode).

diffstat:

 sys/arch/arm/include/mcontext.h |  13 +++++++++++--
 1 files changed, 11 insertions(+), 2 deletions(-)

diffs (29 lines):

diff -r 9e5798a01e3c -r 22b4917b7e7d sys/arch/arm/include/mcontext.h
--- a/sys/arch/arm/include/mcontext.h   Mon Feb 13 16:35:59 2012 +0000
+++ b/sys/arch/arm/include/mcontext.h   Mon Feb 13 17:07:45 2012 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: mcontext.h,v 1.9 2011/04/07 10:20:29 matt Exp $        */
+/*     $NetBSD: mcontext.h,v 1.10 2012/02/13 17:07:45 matt Exp $       */
 
 /*-
  * Copyright (c) 2001, 2002 The NetBSD Foundation, Inc.
@@ -112,9 +112,18 @@
 static __inline void *
 __lwp_getprivate_fast(void)
 {
+       extern void *_lwp_getprivate(void);
        void *rv;
        __asm("mrc p15, 0, %0, c13, c0, 3" : "=r"(rv));
-       return rv;
+       if (__predict_true(rv))
+               return rv;
+       /*
+        * Some ARM cores are broken and don't raise an undefined fault when an
+        * unrecogized mrc instruction is encountered, but just return zero.
+        * To do deal with that, if we get a zero we (re-)fetch the value using
+        * syscall.
+        */
+       return _lwp_getprivate();
 }
 
 #endif /* !_ARM_MCONTEXT_H_ */