notifier-error-inject.c

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#include <linux/module.h>

#include "notifier-error-inject.h"

static int debugfs_errno_set(void *data, u64 val)
{
    *(int *)data = clamp_t(int, val, -MAX_ERRNO, 0);
    return 0;
}

static int debugfs_errno_get(void *data, u64 *val)
{
    *val = *(int *)data;
    return 0;
}

DEFINE_SIMPLE_ATTRIBUTE(fops_errno, debugfs_errno_get, debugfs_errno_set,
            "%lld\n");

static struct dentry *debugfs_create_errno(const char *name, mode_t mode,
                struct dentry *parent, int *value)
{
    return debugfs_create_file(name, mode, parent, value, &fops_errno);
}

static int notifier_err_inject_callback(struct notifier_block *nb,
                unsigned long val, void *p)
{
    int err = 0;
    struct notifier_err_inject *err_inject =
        container_of(nb, struct notifier_err_inject, nb);
    struct notifier_err_inject_action *action;

    for (action = err_inject->actions; action->name; action++) {
        if (action->val == val) {
            err = action->error;
            break;
        }
    }
    if (err)
        pr_info("Injecting error (%d) to %s\n", err, action->name);

    return notifier_from_errno(err);
}

struct dentry *notifier_err_inject_dir;
EXPORT_SYMBOL_GPL(notifier_err_inject_dir);

struct dentry *notifier_err_inject_init(const char *name, struct dentry *parent,
            struct notifier_err_inject *err_inject, int priority)
{
    struct notifier_err_inject_action *action;
    mode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
    struct dentry *dir;
    struct dentry *actions_dir;

    err_inject->nb.notifier_call = notifier_err_inject_callback;
    err_inject->nb.priority = priority;

    dir = debugfs_create_dir(name, parent);
    if (!dir)
        return ERR_PTR(-ENOMEM);

    actions_dir = debugfs_create_dir("actions", dir);
    if (!actions_dir)
        goto fail;

    for (action = err_inject->actions; action->name; action++) {
        struct dentry *action_dir;

        action_dir = debugfs_create_dir(action->name, actions_dir);
        if (!action_dir)
            goto fail;

        /*
         * Create debugfs r/w file containing action->error. If
         * notifier call chain is called with action->val, it will
         * fail with the error code
         */
        if (!debugfs_create_errno("error", mode, action_dir,
                    &action->error))
            goto fail;
    }
    return dir;
fail:
    debugfs_remove_recursive(dir);
    return ERR_PTR(-ENOMEM);
}
EXPORT_SYMBOL_GPL(notifier_err_inject_init);

static int __init err_inject_init(void)
{
    notifier_err_inject_dir =
        debugfs_create_dir("notifier-error-inject", NULL);

    if (!notifier_err_inject_dir)
        return -ENOMEM;

    return 0;
}

static void __exit err_inject_exit(void)
{
    debugfs_remove_recursive(notifier_err_inject_dir);
}

module_init(err_inject_init);
module_exit(err_inject_exit);

MODULE_DESCRIPTION("Notifier error injection module");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Akinobu Mita <[email protected]>");