IB/uverbs: Add UVERBS_ATTR_FLAGS_IN to the specs language

This clearly indicates that the input is a bitwise combination of values
in an enum, and identifies which enum contains the definition of the bits.

Special accessors are provided that handle the mandatory validation of the
allowed bits and enforce the correct type for bitwise flags.

If we had introduced this at the start then the kabi would have uniformly
used u64 data to pass flags, however today there is a mixture of u64 and
u32 flags. All places are converted to accept both sizes and the accessor
fixes it. This allows all existing flags to grow to u64 in future without
any hassle.

Finally all flags are, by definition, optional. If flags are not passed
the accessor does not fail, but provides a value of zero.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>

drivers/infiniband/core/uverbs_ioctl.c

@@ -486,3 +486,54 @@ out:
 
 	return err;
 }
+
+int uverbs_get_flags64(u64 *to, const struct uverbs_attr_bundle *attrs_bundle,
+		       size_t idx, u64 allowed_bits)
+{
+	const struct uverbs_attr *attr;
+	u64 flags;
+
+	attr = uverbs_attr_get(attrs_bundle, idx);
+	/* Missing attribute means 0 flags */
+	if (IS_ERR(attr)) {
+		*to = 0;
+		return 0;
+	}
+
+	/*
+	 * New userspace code should use 8 bytes to pass flags, but we
+	 * transparently support old userspaces that were using 4 bytes as
+	 * well.
+	 */
+	if (attr->ptr_attr.len == 8)
+		flags = attr->ptr_attr.data;
+	else if (attr->ptr_attr.len == 4)
+		memcpy(&flags, &attr->ptr_attr.data, 4);
+	else
+		return -EINVAL;
+
+	if (flags & ~allowed_bits)
+		return -EINVAL;
+
+	*to = flags;
+	return 0;
+}
+EXPORT_SYMBOL(uverbs_get_flags64);
+
+int uverbs_get_flags32(u32 *to, const struct uverbs_attr_bundle *attrs_bundle,
+		       size_t idx, u64 allowed_bits)
+{
+	u64 flags;
+	int ret;
+
+	ret = uverbs_get_flags64(&flags, attrs_bundle, idx, allowed_bits);
+	if (ret)
+		return ret;
+
+	if (flags > U32_MAX)
+		return -EINVAL;
+	*to = flags;
+
+	return 0;
+}
+EXPORT_SYMBOL(uverbs_get_flags32);