b43: Rewrite DMA Tx status handling sanity checks

This rewrites the error handling policies in the TX status handler.
It tries to be error-tolerant as in "try hard to not crash the machine".
It won't recover from errors (that are bugs in the firmware or driver),
because that's impossible. However, it will return a more or less useful
error message and bail out. It also tries hard to use rate-limited messages
to not flood the syslog in case of a failure.

Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/drivers/net/wireless/b43/dma.c b/drivers/net/wireless/b43/dma.c
index 18b97c0..027be27 100644 (file)
--- a/drivers/net/wireless/b43/dma.c
+++ b/drivers/net/wireless/b43/dma.c
@@ -874,7 +874,7 @@ static void free_all_descbuffers(struct b43_dmaring *ring)
        for (i = 0; i < ring->nr_slots; i++) {
                desc = ring->ops->idx2desc(ring, i, &meta);
 
-               if (!meta->skb) {
+               if (!meta->skb || b43_dma_ptr_is_poisoned(meta->skb)) {
                        B43_WARN_ON(!ring->tx);
                        continue;
                }
@@ -926,7 +926,7 @@ struct b43_dmaring *b43_setup_dmaring(struct b43_wldev *dev,
                                      enum b43_dmatype type)
 {
        struct b43_dmaring *ring;
-       int err;
+       int i, err;
        dma_addr_t dma_test;
 
        ring = kzalloc(sizeof(*ring), GFP_KERNEL);
@@ -941,6 +941,8 @@ struct b43_dmaring *b43_setup_dmaring(struct b43_wldev *dev,
                             GFP_KERNEL);
        if (!ring->meta)
                goto err_kfree_ring;
+       for (i = 0; i < ring->nr_slots; i++)
+               ring->meta->skb = B43_DMA_PTR_POISON;
 
        ring->type = type;
        ring->dev = dev;
@@ -1251,11 +1253,13 @@ struct b43_dmaring *parse_cookie(struct b43_wldev *dev, u16 cookie, int *slot)
        case 0x5000:
                ring = dma->tx_ring_mcast;
                break;
-       default:
-               B43_WARN_ON(1);
        }
        *slot = (cookie & 0x0FFF);
-       B43_WARN_ON(!(ring && *slot >= 0 && *slot < ring->nr_slots));
+       if (unlikely(!ring || *slot < 0 || *slot >= ring->nr_slots)) {
+               b43dbg(dev->wl, "TX-status contains "
+                      "invalid cookie: 0x%04X\n", cookie);
+               return NULL;
+       }
 
        return ring;
 }
@@ -1494,19 +1498,40 @@ void b43_dma_handle_txstatus(struct b43_wldev *dev,
        struct b43_dmaring *ring;
        struct b43_dmadesc_generic *desc;
        struct b43_dmadesc_meta *meta;
-       int slot;
+       int slot, firstused;
        bool frame_succeed;
 
        ring = parse_cookie(dev, status->cookie, &slot);
        if (unlikely(!ring))
                return;
-
        B43_WARN_ON(!ring->tx);
+
+       /* Sanity check: TX packets are processed in-order on one ring.
+        * Check if the slot deduced from the cookie really is the first
+        * used slot. */
+       firstused = ring->current_slot - ring->used_slots + 1;
+       if (firstused < 0)
+               firstused = ring->nr_slots + firstused;
+       if (unlikely(slot != firstused)) {
+               /* This possibly is a firmware bug and will result in
+                * malfunction, memory leaks and/or stall of DMA functionality. */
+               b43dbg(dev->wl, "Out of order TX status report on DMA ring %d. "
+                      "Expected %d, but got %d\n",
+                      ring->index, firstused, slot);
+               return;
+       }
+
        ops = ring->ops;
        while (1) {
-               B43_WARN_ON(!(slot >= 0 && slot < ring->nr_slots));
+               B43_WARN_ON(slot < 0 || slot >= ring->nr_slots);
                desc = ops->idx2desc(ring, slot, &meta);
 
+               if (b43_dma_ptr_is_poisoned(meta->skb)) {
+                       b43dbg(dev->wl, "Poisoned TX slot %d (first=%d) "
+                              "on ring %d\n",
+                              slot, firstused, ring->index);
+                       break;
+               }
                if (meta->skb) {
                        struct b43_private_tx_info *priv_info =
                                b43_get_priv_tx_info(IEEE80211_SKB_CB(meta->skb));
@@ -1522,7 +1547,14 @@ void b43_dma_handle_txstatus(struct b43_wldev *dev,
                if (meta->is_last_fragment) {
                        struct ieee80211_tx_info *info;
 
-                       BUG_ON(!meta->skb);
+                       if (unlikely(!meta->skb)) {
+                               /* This is a scatter-gather fragment of a frame, so
+                                * the skb pointer must not be NULL. */
+                               b43dbg(dev->wl, "TX status unexpected NULL skb "
+                                      "at slot %d (first=%d) on ring %d\n",
+                                      slot, firstused, ring->index);
+                               break;
+                       }
 
                        info = IEEE80211_SKB_CB(meta->skb);
 
@@ -1540,20 +1572,29 @@ void b43_dma_handle_txstatus(struct b43_wldev *dev,
 #endif /* DEBUG */
                        ieee80211_tx_status(dev->wl->hw, meta->skb);
 
-                       /* skb is freed by ieee80211_tx_status() */
-                       meta->skb = NULL;
+                       /* skb will be freed by ieee80211_tx_status().
+                        * Poison our pointer. */
+                       meta->skb = B43_DMA_PTR_POISON;
                } else {
                        /* No need to call free_descriptor_buffer here, as
                         * this is only the txhdr, which is not allocated.
                         */
-                       B43_WARN_ON(meta->skb);
+                       if (unlikely(meta->skb)) {
+                               b43dbg(dev->wl, "TX status unexpected non-NULL skb "
+                                      "at slot %d (first=%d) on ring %d\n",
+                                      slot, firstused, ring->index);
+                               break;
+                       }
                }
 
                /* Everything unmapped and free'd. So it's not used anymore. */
                ring->used_slots--;
 
-               if (meta->is_last_fragment)
+               if (meta->is_last_fragment) {
+                       /* This is the last scatter-gather
+                        * fragment of the frame. We are done. */
                        break;
+               }
                slot = next_slot(ring, slot);
        }
        if (ring->stopped) {

diff --git a/drivers/net/wireless/b43/dma.h b/drivers/net/wireless/b43/dma.h
index 356a0ff..e607b39 100644 (file)
--- a/drivers/net/wireless/b43/dma.h
+++ b/drivers/net/wireless/b43/dma.h
@@ -1,7 +1,7 @@
 #ifndef B43_DMA_H_
 #define B43_DMA_H_
 
-#include <linux/ieee80211.h>
+#include <linux/err.h>
 
 #include "b43.h"
 
@@ -164,6 +164,10 @@ struct b43_dmadesc_generic {
 #define B43_RXRING_SLOTS               64
 #define B43_DMA0_RX_BUFFERSIZE         IEEE80211_MAX_FRAME_LEN
 
+/* Pointer poison */
+#define B43_DMA_PTR_POISON             ((void *)ERR_PTR(-ENOMEM))
+#define b43_dma_ptr_is_poisoned(ptr)   (unlikely((ptr) == B43_DMA_PTR_POISON))
+
 
 struct sk_buff;
 struct b43_private;