From c20a84c91048c76c1379011c96b1a5cee5c7d9a0 Mon Sep 17 00:00:00 2001 From: Kyle McMartin Date: Sat, 1 Mar 2008 10:25:52 -0800 Subject: [PATCH] [PARISC] futex: special case cmpxchg NULL in kernel space 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 --- include/asm-parisc/futex.h | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/include/asm-parisc/futex.h b/include/asm-parisc/futex.h index dbee6e60aa..fdc6d055ef 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 -#endif +#endif /*__KERNEL__*/ +#endif /*_ASM_PARISC_FUTEX_H*/ -- 2.39.5