acpi: Disable ACPI table override if securelevel is set

From the kernel documentation (initrd_table_override.txt):

  If the ACPI_INITRD_TABLE_OVERRIDE compile option is true, it is possible
  to override nearly any ACPI table provided by the BIOS with an
  instrumented, modified one.

When securelevel is set, the kernel should disallow any unauthenticated
changes to kernel space. ACPI tables contain code invoked by the kernel, so
do not allow ACPI tables to be overridden if securelevel is set.

Signed-off-by: Linn Crosetto <linn@hpe.com>
void __init acpi_osi_setup(char *str)
{
	struct osi_setup_entry *osi;
	bool enable = true;
	int i;

	if (!acpi_gbl_create_osi_method)
		return;

	if (str == NULL || *str == '\0') {
		printk(KERN_INFO PREFIX "_OSI method disabled\n");
		acpi_gbl_create_osi_method = FALSE;
		return;
	}

	if (*str == '!') {
		str++;
		if (*str == '\0') {
			osi_linux.default_disabling = 1;
			return;
		} else if (*str == '*') {
			acpi_update_interfaces(ACPI_DISABLE_ALL_STRINGS);
			for (i = 0; i < OSI_STRING_ENTRIES_MAX; i++) {
				osi = &osi_setup_entries[i];
				osi->enable = false;
			}
			return;
		}
		enable = false;
	}

	for (i = 0; i < OSI_STRING_ENTRIES_MAX; i++) {
		osi = &osi_setup_entries[i];
		if (!strcmp(osi->string, str)) {
			osi->enable = enable;
			break;
		} else if (osi->string[0] == '\0') {
			osi->enable = enable;
			strncpy(osi->string, str, OSI_STRING_LENGTH_MAX);
			break;
		}
	}
}

void __init acpi_osi_setup(char *str)
{
	struct osi_setup_entry *osi;
	bool enable = true;
	int i;

	if (!acpi_gbl_create_osi_method)
		return;

	if (str == NULL || *str == '\0') {
		printk(KERN_INFO PREFIX "_OSI method disabled\n");
		acpi_gbl_create_osi_method = FALSE;
		return;
	}

	if (*str == '!') {
		str++;
		if (*str == '\0') {
			osi_linux.default_disabling = 1;
			return;
		} else if (*str == '*') {
			acpi_update_interfaces(ACPI_DISABLE_ALL_STRINGS);
			for (i = 0; i < OSI_STRING_ENTRIES_MAX; i++) {
				osi = &osi_setup_entries[i];
				osi->enable = false;
			}
			return;
		}
		enable = false;
	}

	for (i = 0; i < OSI_STRING_ENTRIES_MAX; i++) {
		osi = &osi_setup_entries[i];
		if (!strcmp(osi->string, str)) {
			osi->enable = enable;
			break;
		} else if (osi->string[0] == '\0') {
			osi->enable = enable;
			strncpy(osi->string, str, OSI_STRING_LENGTH_MAX);
			break;
		}
	}
}
