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authorKyle McMartin <kyle@shortfin.cabal.ca>2008-04-15 10:45:11 -0500
committerChris Wright <chrisw@sous-sol.org>2008-04-18 18:53:29 -0700
commitfe23b328b6fd02f23a30690baf45a4092162d760 (patch)
parente9a3ef655c451a9dd1b4df795f6eac253eed6af0 (diff)
PARISC futex: special case cmpxchg NULL in kernel space
upstream commit: c20a84c91048c76c1379011c96b1a5cee5c7d9a0 commit f9e77acd4060fefbb60a351cdb8d30fca27fe194 Author: Thomas Gleixner <tglx@linutronix.de> Date: Sun Feb 24 02:10:05 2008 +0000 futex: runtime enable pi and robust functionality which was backported to stable based on mainline Commit a0c1e9073ef7428a14309cba010633a6cd6719ea added code to futex.c to detect whether futex_atomic_cmpxchg_inatomic was implemented at run time: + curval = cmpxchg_futex_value_locked(NULL, 0, 0); + if (curval == -EFAULT) + futex_cmpxchg_enabled = 1; This is bogus on parisc, since page zero in kernel virtual space is the gateway page for syscall entry, and should not be read from the kernel. (That, and we really don't like the kernel faulting on its own address space...) Signed-off-by: Kyle McMartin <kyle@mcmartin.ca> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com> Signed-off-by: Chris Wright <chrisw@sous-sol.org>
1 files changed, 8 insertions, 2 deletions
diff --git a/include/asm-parisc/futex.h b/include/asm-parisc/futex.h
index dbee6e60aa81..fdc6d055ef7f 100644
--- a/include/asm-parisc/futex.h
+++ b/include/asm-parisc/futex.h
@@ -56,6 +56,12 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
int err = 0;
int uval;
+ /* futex.c wants to do a cmpxchg_inatomic on kernel NULL, which is
+ * our gateway page, and causes no end of trouble...
+ */
+ if (segment_eq(KERNEL_DS, get_fs()) && !uaddr)
+ return -EFAULT;
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
return -EFAULT;
@@ -67,5 +73,5 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
return uval;
+#endif /*__KERNEL__*/
+#endif /*_ASM_PARISC_FUTEX_H*/