add new system file

hc

2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/drivers/acpi/custom_method.c
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@@ -1,3 +1,4 @@
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+// SPDX-License-Identifier: GPL-2.0-only
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 /*
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  * custom_method.c - debugfs interface for customizing ACPI control method
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  */
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@@ -8,11 +9,10 @@
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 #include <linux/uaccess.h>
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 #include <linux/debugfs.h>
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 #include <linux/acpi.h>
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+#include <linux/security.h>
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 #include "internal.h"
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-#define _COMPONENT		ACPI_SYSTEM_COMPONENT
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-ACPI_MODULE_NAME("custom_method");
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 MODULE_LICENSE("GPL");
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 static struct dentry *cm_dentry;
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@@ -28,6 +28,11 @@
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 	struct acpi_table_header table;
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 	acpi_status status;
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+	int ret;
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+
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+	ret = security_locked_down(LOCKDOWN_ACPI_TABLES);
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+	if (ret)
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+		return ret;
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 	if (!(*ppos)) {
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 		/* parse the table header to get the table length */
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@@ -84,21 +89,14 @@
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 static int __init acpi_custom_method_init(void)
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 {
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-	if (acpi_debugfs_dir == NULL)
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-		return -ENOENT;
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-
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 	cm_dentry = debugfs_create_file("custom_method", S_IWUSR,
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 					acpi_debugfs_dir, NULL, &cm_fops);
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-	if (cm_dentry == NULL)
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-		return -ENODEV;
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-
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 	return 0;
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 }
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 static void __exit acpi_custom_method_exit(void)
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 {
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-	if (cm_dentry)
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-		debugfs_remove(cm_dentry);
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+	debugfs_remove(cm_dentry);
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 }
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 module_init(acpi_custom_method_init);