[PATCH] dma-debug: add dumping facility via debugfs

[Corentin Labbe]

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 <cla...@baylibre.com>
---
 kernel/dma/debug.c | 47 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 23cf5361bcf1..9253382f5729 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -144,6 +144,7 @@ static struct dentry *num_free_entries_dent __read_mostly;
 static struct dentry *min_free_entries_dent __read_mostly;
 static struct dentry *nr_total_entries_dent __read_mostly;
 static struct dentry *filter_dent           __read_mostly;
+static struct dentry *dump_dent             __read_mostly;
 
 /* per-driver filter related state */
 
@@ -840,6 +841,47 @@ static const struct file_operations filter_fops = {
        .llseek = default_llseek,
 };
 
+static int dump_read(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;
+}
+
+static int dump_open(struct inode *inode, struct file *file)
+{
+       return single_open(file, dump_read, inode->i_private);
+}
+
+static const struct file_operations dump_fops = {
+       .owner = THIS_MODULE,
+       .open = dump_open,
+       .read = seq_read,
+       .llseek = seq_lseek,
+       .release = single_release,
+};
+
 static int dma_debug_fs_init(void)
 {
        dma_debug_dent = debugfs_create_dir("dma-api", NULL);
@@ -894,6 +936,11 @@ static int dma_debug_fs_init(void)
        if (!filter_dent)
                goto out_err;
 
+       dump_dent = debugfs_create_file("dump", 0444,
+                                       dma_debug_dent, NULL, &dump_fops);
+       if (!dump_dent)
+               goto out_err;
+
        return 0;
 
 out_err:
-- 
2.19.2