dma-debug: add dumping facility via debugfs

While debugging a DMA mapping leak, I needed to access
debug_dma_dump_mappings() but easily from user space.

This patch adds a /sys/kernel/debug/dma-api/dump file which contain all
current DMA mapping.

Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 28 insertions, 0 deletions

diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 56cd836a902c..45d51e8e26f6 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -829,6 +829,33 @@ static const struct file_operations filter_fops = {
         .llseek = default_llseek,
 };
 
+static int dump_show(struct seq_file *seq, void *v)
+{
+        int idx;
+
+        for (idx = 0; idx < HASH_SIZE; idx++) {
+                struct hash_bucket *bucket = &dma_entry_hash[idx];
+                struct dma_debug_entry *entry;
+                unsigned long flags;
+
+                spin_lock_irqsave(&bucket->lock, flags);
+                list_for_each_entry(entry, &bucket->list, list) {
+                        seq_printf(seq,
+                                   "%s %s %s idx %d P=%llx N=%lx D=%llx L=%llx %s %s\n",
+                                   dev_name(entry->dev),
+                                   dev_driver_string(entry->dev),
+                                   type2name[entry->type], idx,
+                                   phys_addr(entry), entry->pfn,
+                                   entry->dev_addr, entry->size,
+                                   dir2name[entry->direction],
+                                   maperr2str[entry->map_err_type]);
+                }
+                spin_unlock_irqrestore(&bucket->lock, flags);
+        }
+        return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(dump);
+
 static void dma_debug_fs_init(void)
 {
         struct dentry *dentry = debugfs_create_dir("dma-api", NULL);
@@ -841,6 +868,7 @@ static void dma_debug_fs_init(void)
         debugfs_create_u32("min_free_entries", 0444, dentry, &min_free_entries);
         debugfs_create_u32("nr_total_entries", 0444, dentry, &nr_total_entries);
         debugfs_create_file("driver_filter", 0644, dentry, NULL, &filter_fops);
+        debugfs_create_file("dump", 0444, dentry, NULL, &dump_fops);
 }
 
 static int device_dma_allocations(struct device *dev, struct dma_debug_entry **out_entry)