static int notrace s390_validate_registers()

in kernel/nmi.c [183:333]

• 100 lines of code
• 19 McCabe index (conditional complexity)

static int notrace s390_validate_registers(union mci mci, int umode)
{
	struct mcesa *mcesa;
	void *fpt_save_area;
	union ctlreg2 cr2;
	int kill_task;
	u64 zero;

	kill_task = 0;
	zero = 0;

	if (!mci.gr) {
		/*
		 * General purpose registers couldn't be restored and have
		 * unknown contents. Stop system or terminate process.
		 */
		if (!umode)
			s390_handle_damage();
		kill_task = 1;
	}
	if (!mci.fp) {
		/*
		 * Floating point registers can't be restored. If the
		 * kernel currently uses floating point registers the
		 * system is stopped. If the process has its floating
		 * pointer registers loaded it is terminated.
		 */
		if (S390_lowcore.fpu_flags & KERNEL_VXR_V0V7)
			s390_handle_damage();
		if (!test_cpu_flag(CIF_FPU))
			kill_task = 1;
	}
	fpt_save_area = &S390_lowcore.floating_pt_save_area;
	if (!mci.fc) {
		/*
		 * Floating point control register can't be restored.
		 * If the kernel currently uses the floating pointer
		 * registers and needs the FPC register the system is
		 * stopped. If the process has its floating pointer
		 * registers loaded it is terminated. Otherwise the
		 * FPC is just validated.
		 */
		if (S390_lowcore.fpu_flags & KERNEL_FPC)
			s390_handle_damage();
		asm volatile(
			"	lfpc	%0\n"
			:
			: "Q" (zero));
		if (!test_cpu_flag(CIF_FPU))
			kill_task = 1;
	} else {
		asm volatile(
			"	lfpc	%0\n"
			:
			: "Q" (S390_lowcore.fpt_creg_save_area));
	}

	mcesa = __va(S390_lowcore.mcesad & MCESA_ORIGIN_MASK);
	if (!MACHINE_HAS_VX) {
		/* Validate floating point registers */
		asm volatile(
			"	ld	0,0(%0)\n"
			"	ld	1,8(%0)\n"
			"	ld	2,16(%0)\n"
			"	ld	3,24(%0)\n"
			"	ld	4,32(%0)\n"
			"	ld	5,40(%0)\n"
			"	ld	6,48(%0)\n"
			"	ld	7,56(%0)\n"
			"	ld	8,64(%0)\n"
			"	ld	9,72(%0)\n"
			"	ld	10,80(%0)\n"
			"	ld	11,88(%0)\n"
			"	ld	12,96(%0)\n"
			"	ld	13,104(%0)\n"
			"	ld	14,112(%0)\n"
			"	ld	15,120(%0)\n"
			:
			: "a" (fpt_save_area)
			: "memory");
	} else {
		/* Validate vector registers */
		union ctlreg0 cr0;

		if (!mci.vr) {
			/*
			 * Vector registers can't be restored. If the kernel
			 * currently uses vector registers the system is
			 * stopped. If the process has its vector registers
			 * loaded it is terminated. Otherwise just validate
			 * the registers.
			 */
			if (S390_lowcore.fpu_flags & KERNEL_VXR)
				s390_handle_damage();
			if (!test_cpu_flag(CIF_FPU))
				kill_task = 1;
		}
		cr0.val = S390_lowcore.cregs_save_area[0];
		cr0.afp = cr0.vx = 1;
		__ctl_load(cr0.val, 0, 0);
		asm volatile(
			"	la	1,%0\n"
			"	.word	0xe70f,0x1000,0x0036\n" /* vlm 0,15,0(1) */
			"	.word	0xe70f,0x1100,0x0c36\n" /* vlm 16,31,256(1) */
			:
			: "Q" (*(struct vx_array *)mcesa->vector_save_area)
			: "1");
		__ctl_load(S390_lowcore.cregs_save_area[0], 0, 0);
	}
	/* Validate access registers */
	asm volatile(
		"	lam	0,15,0(%0)\n"
		:
		: "a" (&S390_lowcore.access_regs_save_area)
		: "memory");
	if (!mci.ar) {
		/*
		 * Access registers have unknown contents.
		 * Terminating task.
		 */
		kill_task = 1;
	}
	/* Validate guarded storage registers */
	cr2.val = S390_lowcore.cregs_save_area[2];
	if (cr2.gse) {
		if (!mci.gs) {
			/*
			 * Guarded storage register can't be restored and
			 * the current processes uses guarded storage.
			 * It has to be terminated.
			 */
			kill_task = 1;
		} else {
			load_gs_cb((struct gs_cb *)mcesa->guarded_storage_save_area);
		}
	}
	/*
	 * The getcpu vdso syscall reads CPU number from the programmable
	 * field of the TOD clock. Disregard the TOD programmable register
	 * validity bit and load the CPU number into the TOD programmable
	 * field unconditionally.
	 */
	set_tod_programmable_field(raw_smp_processor_id());
	/* Validate clock comparator register */
	set_clock_comparator(S390_lowcore.clock_comparator);

	if (!mci.ms || !mci.pm || !mci.ia)
		kill_task = 1;

	return kill_task;
}