custom_method.c

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/*
 * debugfs.c - ACPI debugfs interface to userspace.
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/uaccess.h>
#include <linux/debugfs.h>
#include <acpi/acpi_drivers.h>

#include "internal.h"

#define _COMPONENT      ACPI_SYSTEM_COMPONENT
ACPI_MODULE_NAME("custom_method");
MODULE_LICENSE("GPL");

static struct dentry *cm_dentry;

/* /sys/kernel/debug/acpi/custom_method */

static ssize_t cm_write(struct file *file, const char __user * user_buf,
            size_t count, loff_t *ppos)
{
    static char *buf;
    static u32 max_size;
    static u32 uncopied_bytes;

    struct acpi_table_header table;
    acpi_status status;

    if (!(*ppos)) {
        /* parse the table header to get the table length */
        if (count <= sizeof(struct acpi_table_header))
            return -EINVAL;
        if (copy_from_user(&table, user_buf,
                   sizeof(struct acpi_table_header)))
            return -EFAULT;
        uncopied_bytes = max_size = table.length;
        buf = kzalloc(max_size, GFP_KERNEL);
        if (!buf)
            return -ENOMEM;
    }

    if (buf == NULL)
        return -EINVAL;

    if ((*ppos > max_size) ||
        (*ppos + count > max_size) ||
        (*ppos + count < count) ||
        (count > uncopied_bytes))
        return -EINVAL;

    if (copy_from_user(buf + (*ppos), user_buf, count)) {
        kfree(buf);
        buf = NULL;
        return -EFAULT;
    }

    uncopied_bytes -= count;
    *ppos += count;

    if (!uncopied_bytes) {
        status = acpi_install_method(buf);
        kfree(buf);
        buf = NULL;
        if (ACPI_FAILURE(status))
            return -EINVAL;
        add_taint(TAINT_OVERRIDDEN_ACPI_TABLE);
    }

    return count;
}

static const struct file_operations cm_fops = {
    .write = cm_write,
    .llseek = default_llseek,
};

static int __init acpi_custom_method_init(void)
{
    if (acpi_debugfs_dir == NULL)
        return -ENOENT;

    cm_dentry = debugfs_create_file("custom_method", S_IWUSR,
                    acpi_debugfs_dir, NULL, &cm_fops);
    if (cm_dentry == NULL)
        return -ENODEV;

    return 0;
}

static void __exit acpi_custom_method_exit(void)
{
    if (cm_dentry)
        debugfs_remove(cm_dentry);
 }

module_init(acpi_custom_method_init);
module_exit(acpi_custom_method_exit);