1 files changed, 103 insertions, 0 deletions
diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c
new file mode 100644
index 000000000..d39a9b474
--- /dev/null
+++ b/drivers/acpi/custom_method.c
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * custom_method.c - debugfs interface for customizing ACPI control method
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/uaccess.h>
+#include <linux/debugfs.h>
+#include <linux/acpi.h>
+#include <linux/security.h>
+
+#include "internal.h"
+
+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;
+	int ret;
+
+	ret = security_locked_down(LOCKDOWN_ACPI_TABLES);
+	if (ret)
+		return ret;
+
+	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;
+		/* make sure the buf is not allocated */
+		kfree(buf);
+		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)) {
+		kfree(buf);
+		buf = NULL;
+		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, LOCKDEP_NOW_UNRELIABLE);
+	}
+
+	return count;
+}
+
+static const struct file_operations cm_fops = {
+	.write = cm_write,
+	.llseek = default_llseek,
+};
+
+static int __init acpi_custom_method_init(void)
+{
+	cm_dentry = debugfs_create_file("custom_method", S_IWUSR,
+					acpi_debugfs_dir, NULL, &cm_fops);
+	return 0;
+}
+
+static void __exit acpi_custom_method_exit(void)
+{
+	debugfs_remove(cm_dentry);
+}
+
+module_init(acpi_custom_method_init);
+module_exit(acpi_custom_method_exit);