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Commit 8a6fc708 authored by Joerg Roedel's avatar Joerg Roedel
Browse files

dma-debug: add debugfs file for driver filter 



This patch adds the dma-api/driver_filter file to debugfs. The root user
can write a driver name into this file to see only dma-api errors for
that particular driver in the kernel log. Writing an empty string to
that file disables the driver filter.

Signed-off-by: default avatarJoerg Roedel <joerg.roedel@amd.com>
parent 2e507d84

lib/dma-debug.c

+101 −1
Original line number Diff line number Diff line
@@ -23,9 +23,11 @@ 
#include <linux/dma-debug.h>

#include <linux/spinlock.h>

#include <linux/debugfs.h>

#include <linux/uaccess.h>

#include <linux/device.h>

#include <linux/types.h>

#include <linux/sched.h>

#include <linux/ctype.h>

#include <linux/list.h>

#include <linux/slab.h>
@@ -98,6 +100,7 @@ static struct dentry *show_all_errors_dent __read_mostly; 
static struct dentry *show_num_errors_dent  __read_mostly;

static struct dentry *num_free_entries_dent __read_mostly;

static struct dentry *min_free_entries_dent __read_mostly;

static struct dentry *filter_dent           __read_mostly;



/* per-driver filter related state */
@@ -160,7 +163,8 @@ static bool driver_filter(struct device *dev) 
		read_lock_irqsave(&driver_name_lock, flags);



		if (drv->name &&

		    strncmp(current_driver_name, drv->name, 63) == 0) {

		    strncmp(current_driver_name, drv->name,

			    NAME_MAX_LEN-1) == 0) {

			current_driver = drv;

			ret = true;

		}
@@ -454,6 +458,97 @@ out_err: 
	return -ENOMEM;

}



static ssize_t filter_read(struct file *file, char __user *user_buf,

			   size_t count, loff_t *ppos)

{

	unsigned long flags;

	char buf[NAME_MAX_LEN + 1];

	int len;



	if (!current_driver_name[0])

		return 0;



	/*

	 * We can't copy to userspace directly because current_driver_name can

	 * only be read under the driver_name_lock with irqs disabled. So

	 * create a temporary copy first.

	 */

	read_lock_irqsave(&driver_name_lock, flags);

	len = scnprintf(buf, NAME_MAX_LEN + 1, "%s\n", current_driver_name);

	read_unlock_irqrestore(&driver_name_lock, flags);



	return simple_read_from_buffer(user_buf, count, ppos, buf, len);

}



static ssize_t filter_write(struct file *file, const char __user *userbuf,

			    size_t count, loff_t *ppos)

{

	unsigned long flags;

	char buf[NAME_MAX_LEN];

	size_t len = NAME_MAX_LEN - 1;

	int i;



	/*

	 * We can't copy from userspace directly. Access to

	 * current_driver_name is protected with a write_lock with irqs

	 * disabled. Since copy_from_user can fault and may sleep we

	 * need to copy to temporary buffer first

	 */

	len = min(count, len);

	if (copy_from_user(buf, userbuf, len))

		return -EFAULT;



	buf[len] = 0;



	write_lock_irqsave(&driver_name_lock, flags);



	/* Now handle the string we got from userspace very carefully.

	 * The rules are:

	 *         - only use the first token we got

	 *         - token delimiter is everything looking like a space

	 *           character (' ', '\n', '\t' ...)

	 *

	 */

	if (!isalnum(buf[0])) {

		/*

		   If the first character userspace gave us is not

		 * alphanumerical then assume the filter should be

		 * switched off.

		 */

		if (current_driver_name[0])

			printk(KERN_INFO "DMA-API: switching off dma-debug "

					 "driver filter\n");

		current_driver_name[0] = 0;

		current_driver = NULL;

		goto out_unlock;

	}



	/*

	 * Now parse out the first token and use it as the name for the

	 * driver to filter for.

	 */

	for (i = 0; i < NAME_MAX_LEN; ++i) {

		current_driver_name[i] = buf[i];

		if (isspace(buf[i]) || buf[i] == ' ' || buf[i] == 0)

			break;

	}

	current_driver_name[i] = 0;

	current_driver = NULL;



	printk(KERN_INFO "DMA-API: enable driver filter for driver [%s]\n",

	       current_driver_name);



out_unlock:

	write_unlock_irqrestore(&driver_name_lock, flags);



	return count;

}



const struct file_operations filter_fops = {

	.read  = filter_read,

	.write = filter_write,

};



static int dma_debug_fs_init(void)

{

	dma_debug_dent = debugfs_create_dir("dma-api", NULL);
@@ -497,6 +592,11 @@ static int dma_debug_fs_init(void) 
	if (!min_free_entries_dent)

		goto out_err;



	filter_dent = debugfs_create_file("driver_filter", 0644,

					  dma_debug_dent, NULL, &filter_fops);

	if (!filter_dent)

		goto out_err;



	return 0;



out_err: