asm-generic: add generic futex for !CONFIG_SMP

Follow m68k futex implementation for !CONFIG_SMP.

Signed-off-by: Ley Foon Tan <lftan@altera.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 114 insertions, 0 deletions

diff --git a/include/asm-generic/futex.h b/include/asm-generic/futex.h
index 01f227e14254..b59b5a52637e 100644
--- a/include/asm-generic/futex.h
+++ b/include/asm-generic/futex.h
@@ -5,6 +5,119 @@
 #include <linux/uaccess.h>
 #include <asm/errno.h>
 
+#ifndef CONFIG_SMP
+/*
+ * The following implementation only for uniprocessor machines.
+ * For UP, it's relies on the fact that pagefault_disable() also disables
+ * preemption to ensure mutual exclusion.
+ *
+ */
+
+/**
+ * futex_atomic_op_inuser() - Atomic arithmetic operation with constant
+ *                        argument and comparison of the previous
+ *                        futex value with another constant.
+ *
+ * @encoded_op: encoded operation to execute
+ * @uaddr:      pointer to user space address
+ *
+ * Return:
+ * 0 - On success
+ * <0 - On error
+ */
+static inline int
+futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
+{
+        int op = (encoded_op >> 28) & 7;
+        int cmp = (encoded_op >> 24) & 15;
+        int oparg = (encoded_op << 8) >> 20;
+        int cmparg = (encoded_op << 20) >> 20;
+        int oldval, ret;
+        u32 tmp;
+
+        if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
+                oparg = 1 << oparg;
+
+        pagefault_disable();
+
+        ret = -EFAULT;
+        if (unlikely(get_user(oldval, uaddr) != 0))
+                goto out_pagefault_enable;
+
+        ret = 0;
+        tmp = oldval;
+
+        switch (op) {
+        case FUTEX_OP_SET:
+                tmp = oparg;
+                break;
+        case FUTEX_OP_ADD:
+                tmp += oparg;
+                break;
+        case FUTEX_OP_OR:
+                tmp |= oparg;
+                break;
+        case FUTEX_OP_ANDN:
+                tmp &= ~oparg;
+                break;
+        case FUTEX_OP_XOR:
+                tmp ^= oparg;
+                break;
+        default:
+                ret = -ENOSYS;
+        }
+
+        if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0))
+                ret = -EFAULT;
+
+out_pagefault_enable:
+        pagefault_enable();
+
+        if (ret == 0) {
+                switch (cmp) {
+                case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
+                case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
+                case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
+                case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
+                case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
+                case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
+                default: ret = -ENOSYS;
+                }
+        }
+        return ret;
+}
+
+/**
+ * futex_atomic_cmpxchg_inatomic() - Compare and exchange the content of the
+ *                              uaddr with newval if the current value is
+ *                              oldval.
+ * @uval:       pointer to store content of @uaddr
+ * @uaddr:      pointer to user space address
+ * @oldval:     old value
+ * @newval:     new value to store to @uaddr
+ *
+ * Return:
+ * 0 - On success
+ * <0 - On error
+ */
+static inline int
+futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
+                              u32 oldval, u32 newval)
+{
+        u32 val;
+
+        if (unlikely(get_user(val, uaddr) != 0))
+                return -EFAULT;
+
+        if (val == oldval && unlikely(put_user(newval, uaddr) != 0))
+                return -EFAULT;
+
+        *uval = val;
+
+        return 0;
+}
+
+#else
 static inline int
 futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
 {
@@ -54,4 +167,5 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
         return -ENOSYS;
 }
 
+#endif /* CONFIG_SMP */
 #endif