dmapool: make DMAPOOL_DEBUG detect corruption of free marker

This can help to catch the case where hardware is writing after dma free.

[akpm@linux-foundation.org: tidy code, fix comment, use sizeof(page->offset), use pr_err()]
Signed-off-by: Matthieu Castet <matthieu.castet@parrot.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 24 insertions, 0 deletions

diff --git a/mm/dmapool.c b/mm/dmapool.c
index da1b0f0b8709..c69781e97cf9 100644
--- a/mm/dmapool.c
+++ b/mm/dmapool.c
@@ -332,6 +332,30 @@ void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
         retval = offset + page->vaddr;
         *handle = offset + page->dma;
 #ifdef  DMAPOOL_DEBUG
+        {
+                int i;
+                u8 *data = retval;
+                /* page->offset is stored in first 4 bytes */
+                for (i = sizeof(page->offset); i < pool->size; i++) {
+                        if (data[i] == POOL_POISON_FREED)
+                                continue;
+                        if (pool->dev)
+                                dev_err(pool->dev,
+                                        "dma_pool_alloc %s, %p (corruped)\n",
+                                        pool->name, retval);
+                        else
+                                pr_err("dma_pool_alloc %s, %p (corruped)\n",
+                                        pool->name, retval);
+
+                        /*
+                         * Dump the first 4 bytes even if they are not
+                         * POOL_POISON_FREED
+                         */
+                        print_hex_dump(KERN_ERR, "", DUMP_PREFIX_OFFSET, 16, 1,
+                                        data, pool->size, 1);
+                        break;
+                }
+        }
         memset(retval, POOL_POISON_ALLOCATED, pool->size);
 #endif
         spin_unlock_irqrestore(&pool->lock, flags);