From 8a6fc708b9bb48a79a385bdc2be0959ee2ab788d Mon Sep 17 00:00:00 2001 From: Joerg Roedel Date: Fri, 22 May 2009 21:23:13 +0200 Subject: 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: Joerg Roedel --- lib/dma-debug.c | 102 +++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 101 insertions(+), 1 deletion(-) (limited to 'lib') diff --git a/lib/dma-debug.c b/lib/dma-debug.c index c01f64780caf..c6330b1a7be7 100644 --- a/lib/dma-debug.c +++ b/lib/dma-debug.c @@ -23,9 +23,11 @@ #include #include #include +#include #include #include #include +#include #include #include @@ -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: -- cgit v1.2.2