[PARISC] Fix futex support

Implements futex op support and makes futex cmpxchg atomic.
Tested on 64-bit SMP kernel running on 2 x PA8700s.

[jejb: checkpatch fixes]
Signed-off-by: Carlos O'Donell <carlos@systemhalted.org>
Tested-by: John David Anglin <dave.anglin@bell.net>
Cc: stable@kernel.org
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 60 insertions, 6 deletions

diff --git a/arch/parisc/include/asm/futex.h b/arch/parisc/include/asm/futex.h
index 67a33cc27ef..2388bdb3283 100644
--- a/arch/parisc/include/asm/futex.h
+++ b/arch/parisc/include/asm/futex.h
@@ -5,11 +5,14 @@
 
 #include <linux/futex.h>
 #include <linux/uaccess.h>
+#include <asm/atomic.h>
 #include <asm/errno.h>
 
 static inline int
 futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
 {
+        unsigned long int flags;
+        u32 val;
         int op = (encoded_op >> 28) & 7;
         int cmp = (encoded_op >> 24) & 15;
         int oparg = (encoded_op << 8) >> 20;
@@ -18,21 +21,58 @@ futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
         if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
                 oparg = 1 << oparg;
 
-        if (! access_ok (VERIFY_WRITE, uaddr, sizeof(u32)))
+        if (!access_ok(VERIFY_WRITE, uaddr, sizeof(*uaddr)))
                 return -EFAULT;
 
         pagefault_disable();
 
+        _atomic_spin_lock_irqsave(uaddr, flags);
+
         switch (op) {
         case FUTEX_OP_SET:
+                /* *(int *)UADDR2 = OPARG; */
+                ret = get_user(oldval, uaddr);
+                if (!ret)
+                        ret = put_user(oparg, uaddr);
+                break;
         case FUTEX_OP_ADD:
+                /* *(int *)UADDR2 += OPARG; */
+                ret = get_user(oldval, uaddr);
+                if (!ret) {
+                        val = oldval + oparg;
+                        ret = put_user(val, uaddr);
+                }
+                break;
         case FUTEX_OP_OR:
+                /* *(int *)UADDR2 |= OPARG; */
+                ret = get_user(oldval, uaddr);
+                if (!ret) {
+                        val = oldval | oparg;
+                        ret = put_user(val, uaddr);
+                }
+                break;
         case FUTEX_OP_ANDN:
+                /* *(int *)UADDR2 &= ~OPARG; */
+                ret = get_user(oldval, uaddr);
+                if (!ret) {
+                        val = oldval & ~oparg;
+                        ret = put_user(val, uaddr);
+                }
+                break;
         case FUTEX_OP_XOR:
+                /* *(int *)UADDR2 ^= OPARG; */
+                ret = get_user(oldval, uaddr);
+                if (!ret) {
+                        val = oldval ^ oparg;
+                        ret = put_user(val, uaddr);
+                }
+                break;
         default:
                 ret = -ENOSYS;
         }
 
+        _atomic_spin_unlock_irqrestore(uaddr, flags);
+
         pagefault_enable();
 
         if (!ret) {
@@ -54,7 +94,9 @@ static inline int
 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
                               u32 oldval, u32 newval)
 {
+        int ret;
         u32 val;
+        unsigned long flags;
 
         /* futex.c wants to do a cmpxchg_inatomic on kernel NULL, which is
          * our gateway page, and causes no end of trouble...
@@ -65,12 +107,24 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
         if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
                 return -EFAULT;
 
-        if (get_user(val, uaddr))
-                return -EFAULT;
-        if (val == oldval && put_user(newval, uaddr))
-                return -EFAULT;
+        /* HPPA has no cmpxchg in hardware and therefore the
+         * best we can do here is use an array of locks. The
+         * lock selected is based on a hash of the userspace
+         * address. This should scale to a couple of CPUs.
+         */
+
+        _atomic_spin_lock_irqsave(uaddr, flags);
+
+        ret = get_user(val, uaddr);
+
+        if (!ret && val == oldval)
+                ret = put_user(newval, uaddr);
+
         *uval = val;
-        return 0;
+
+        _atomic_spin_unlock_irqrestore(uaddr, flags);
+
+        return ret;
 }
 
 #endif /*__KERNEL__*/