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SubjectRe: [PATCH] dma-debug: add dumping facility via debugfs
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On 16/01/2019 13:44, Corentin Labbe wrote:
> 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>
> ---
> 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;
> +}

It's a shame that this is pretty much a duplication of
debug_dma_dump_mappings(), but there seems no straightforward way to
define one in terms of the other :/

(although given that we'd rather not have that weird external interface
anyway, maybe "now you can use debugfs instead" might be justification
enough for cleaning it up...)

> +
> +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,
> +};
> +

DEFINE_SHOW_ATTRIBUTE()?

Robin.

> 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:
>

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