wifi: cfg80211: annotate iftype_data pointer with sparse

There were are a number of cases in mac80211 and iwlwifi (at
least) that used the sband->iftype_data pointer directly,
instead of using the accessors to find the right array entry
to use.

Make sparse warn when such a thing is done.

To not have a lot of casts, add two helper functions/macros

 - ieee80211_set_sband_iftype_data()
 - for_each_sband_iftype_data()

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 54 insertions, 5 deletions

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index aa9c26a03f30..922fd9e0d9b4 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -410,6 +410,19 @@ struct ieee80211_sta_eht_cap {
 	u8 eht_ppe_thres[IEEE80211_EHT_PPE_THRES_MAX_LEN];
 };
 
+/* sparse defines __CHECKER__; see Documentation/dev-tools/sparse.rst */
+#ifdef __CHECKER__
+/*
+ * This is used to mark the sband->iftype_data pointer which is supposed
+ * to be an array with special access semantics (per iftype), but a lot
+ * of code got it wrong in the past, so with this marking sparse will be
+ * noisy when the pointer is used directly.
+ */
+# define __iftd		__attribute__((noderef, address_space(__iftype_data)))
+#else
+# define __iftd
+#endif /* __CHECKER__ */
+
 /**
  * struct ieee80211_sband_iftype_data - sband data per interface type
  *
@@ -543,10 +556,48 @@ struct ieee80211_supported_band {
 	struct ieee80211_sta_s1g_cap s1g_cap;
 	struct ieee80211_edmg edmg_cap;
 	u16 n_iftype_data;
-	const struct ieee80211_sband_iftype_data *iftype_data;
+	const struct ieee80211_sband_iftype_data __iftd *iftype_data;
 };
 
 /**
+ * _ieee80211_set_sband_iftype_data - set sband iftype data array
+ * @sband: the sband to initialize
+ * @iftd: the iftype data array pointer
+ * @n_iftd: the length of the iftype data array
+ *
+ * Set the sband iftype data array; use this where the length cannot
+ * be derived from the ARRAY_SIZE() of the argument, but prefer
+ * ieee80211_set_sband_iftype_data() where it can be used.
+ */
+static inline void
+_ieee80211_set_sband_iftype_data(struct ieee80211_supported_band *sband,
+				 const struct ieee80211_sband_iftype_data *iftd,
+				 u16 n_iftd)
+{
+	sband->iftype_data = (const void __iftd __force *)iftd;
+	sband->n_iftype_data = n_iftd;
+}
+
+/**
+ * ieee80211_set_sband_iftype_data - set sband iftype data array
+ * @sband: the sband to initialize
+ * @iftd: the iftype data array
+ */
+#define ieee80211_set_sband_iftype_data(sband, iftd)	\
+	_ieee80211_set_sband_iftype_data(sband, iftd, ARRAY_SIZE(iftd))
+
+/**
+ * for_each_sband_iftype_data - iterate sband iftype data entries
+ * @sband: the sband whose iftype_data array to iterate
+ * @i: iterator counter
+ * @iftd: iftype data pointer to set
+ */
+#define for_each_sband_iftype_data(sband, i, iftd)				\
+	for (i = 0, iftd = (const void __force *)&(sband)->iftype_data[i];	\
+	     i < (sband)->n_iftype_data;					\
+	     i++, iftd = (const void __force *)&(sband)->iftype_data[i])
+
+/**
  * ieee80211_get_sband_iftype_data - return sband data for a given iftype
  * @sband: the sband to search for the STA on
  * @iftype: enum nl80211_iftype
@@ -557,6 +608,7 @@ static inline const struct ieee80211_sband_iftype_data *
 ieee80211_get_sband_iftype_data(const struct ieee80211_supported_band *sband,
 				u8 iftype)
 {
+	const struct ieee80211_sband_iftype_data *data;
 	int i;
 
 	if (WARN_ON(iftype >= NL80211_IFTYPE_MAX))
@@ -565,10 +617,7 @@ ieee80211_get_sband_iftype_data(const struct ieee80211_supported_band *sband,
 	if (iftype == NL80211_IFTYPE_AP_VLAN)
 		iftype = NL80211_IFTYPE_AP;
 
-	for (i = 0; i < sband->n_iftype_data; i++)  {
-		const struct ieee80211_sband_iftype_data *data =
-			&sband->iftype_data[i];
-
+	for_each_sband_iftype_data(sband, i, data) {
 		if (data->types_mask & BIT(iftype))
 			return data;
 	}