s390/mcck: move register validation to C code

This update partially reverts commit 3037a52f ("s390/nmi:
do register validation as early as possible").

Storage error checks and control registers validation are left
in the assembler code, since correct ASCEs and page tables are
required to enable DAT - which is done before the C handler is
entered.

System damage, kernel instruction address and PSW MWP checks
are left in the assembler code as well, since there is no way
to proceed if one of these checks is failed.

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.
Signed-off-by: NAlexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: NHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: NHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: NVasily Gorbik <gor@linux.ibm.com>

arch/s390/include/asm/ctl_reg.h

@@ -21,8 +21,6 @@
 #define CR0_INTERRUPT_KEY_SUBMASK	BIT(63 - 57)
 #define CR0_MEASUREMENT_ALERT_SUBMASK	BIT(63 - 58)
 
-#define CR2_GUARDED_STORAGE		BIT(63 - 59)
-
 #define CR14_UNUSED_32			BIT(63 - 32)
 #define CR14_UNUSED_33			BIT(63 - 33)
 #define CR14_CHANNEL_REPORT_SUBMASK	BIT(63 - 35)

arch/s390/kernel/asm-offsets.c

@@ -14,8 +14,6 @@
 #include <linux/pgtable.h>
 #include <asm/idle.h>
 #include <asm/gmap.h>
-#include <asm/nmi.h>
-#include <asm/setup.h>
 #include <asm/stacktrace.h>
 
 int main(void)
@@ -108,7 +106,6 @@ int main(void)
 	OFFSET(__LC_LAST_UPDATE_CLOCK, lowcore, last_update_clock);
 	OFFSET(__LC_INT_CLOCK, lowcore, int_clock);
 	OFFSET(__LC_MCCK_CLOCK, lowcore, mcck_clock);
-	OFFSET(__LC_CLOCK_COMPARATOR, lowcore, clock_comparator);
 	OFFSET(__LC_BOOT_CLOCK, lowcore, boot_clock);
 	OFFSET(__LC_CURRENT, lowcore, current_task);
 	OFFSET(__LC_KERNEL_STACK, lowcore, kernel_stack);
@@ -145,9 +142,6 @@ int main(void)
 	OFFSET(__LC_CREGS_SAVE_AREA, lowcore, cregs_save_area);
 	OFFSET(__LC_PGM_TDB, lowcore, pgm_tdb);
 	BLANK();
-	/* extended machine check save area */
-	OFFSET(__MCESA_GS_SAVE_AREA, mcesa, guarded_storage_save_area);
-	BLANK();
 	/* gmap/sie offsets */
 	OFFSET(__GMAP_ASCE, gmap, asce);
 	OFFSET(__SIE_PROG0C, kvm_s390_sie_block, prog0c);

arch/s390/kernel/entry.S

@@ -14,7 +14,6 @@
 #include <asm/alternative-asm.h>
 #include <asm/processor.h>
 #include <asm/cache.h>
-#include <asm/ctl_reg.h>
 #include <asm/dwarf.h>
 #include <asm/errno.h>
 #include <asm/ptrace.h>
@@ -506,8 +505,6 @@ ENTRY(mcck_int_handler)
 	BPOFF
 	la	%r1,4095		# validate r1
 	spt	__LC_CPU_TIMER_SAVE_AREA-4095(%r1)	# validate cpu timer
-	sckc	__LC_CLOCK_COMPARATOR			# validate comparator
-	lam	%a0,%a15,__LC_AREGS_SAVE_AREA-4095(%r1) # validate acrs
 	lmg	%r0,%r15,__LC_GPREGS_SAVE_AREA-4095(%r1)# validate gprs
 	lg	%r12,__LC_CURRENT
 	lmg	%r8,%r9,__LC_MCK_OLD_PSW
@@ -518,41 +515,7 @@ ENTRY(mcck_int_handler)
 	la	%r14,4095
 	lctlg	%c0,%c15,__LC_CREGS_SAVE_AREA-4095(%r14) # validate ctl regs
 	ptlb
-	lg	%r11,__LC_MCESAD-4095(%r14) # extended machine check save area
-	nill	%r11,0xfc00		# MCESA_ORIGIN_MASK
-	TSTMSK	__LC_CREGS_SAVE_AREA+16-4095(%r14),CR2_GUARDED_STORAGE
-	jno	0f
-	TSTMSK	__LC_MCCK_CODE,MCCK_CODE_GS_VALID
-	jno	0f
-	.insn	 rxy,0xe3000000004d,0,__MCESA_GS_SAVE_AREA(%r11) # LGSC
-0:	l	%r14,__LC_FP_CREG_SAVE_AREA-4095(%r14)
-	TSTMSK	__LC_MCCK_CODE,MCCK_CODE_FC_VALID
-	jo	0f
-	sr	%r14,%r14
-0:	sfpc	%r14
-	TSTMSK	__LC_MACHINE_FLAGS,MACHINE_FLAG_VX
-	jo	0f
-	lghi	%r14,__LC_FPREGS_SAVE_AREA
-	ld	%f0,0(%r14)
-	ld	%f1,8(%r14)
-	ld	%f2,16(%r14)
-	ld	%f3,24(%r14)
-	ld	%f4,32(%r14)
-	ld	%f5,40(%r14)
-	ld	%f6,48(%r14)
-	ld	%f7,56(%r14)
-	ld	%f8,64(%r14)
-	ld	%f9,72(%r14)
-	ld	%f10,80(%r14)
-	ld	%f11,88(%r14)
-	ld	%f12,96(%r14)
-	ld	%f13,104(%r14)
-	ld	%f14,112(%r14)
-	ld	%f15,120(%r14)
-	j	1f
-0:	VLM	%v0,%v15,0,%r11
-	VLM	%v16,%v31,256,%r11
-1:	lghi	%r14,__LC_CPU_TIMER_SAVE_AREA
+	lghi	%r14,__LC_CPU_TIMER_SAVE_AREA
 	mvc	__LC_MCCK_ENTER_TIMER(8),0(%r14)
 	TSTMSK	__LC_MCCK_CODE,MCCK_CODE_CPU_TIMER_VALID
 	jo	3f

arch/s390/kernel/nmi.c

@@ -189,12 +189,16 @@ void noinstr s390_handle_mcck(void)
  * returns 0 if all required registers are available
  * returns 1 otherwise
  */
-static int notrace s390_check_registers(union mci mci, int umode)
+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) {
 		/*
@@ -217,35 +221,89 @@ static int notrace s390_check_registers(union mci mci, int umode)
 		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.
+		 * 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));
 	}
 
-	if (MACHINE_HAS_VX) {
+	mcesa = (struct mcesa *)(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.
+			 * 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);
 	}
-	/* Check if access registers are valid */
+	/* 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.
@@ -253,7 +311,7 @@ static int notrace s390_check_registers(union mci mci, int umode)
 		 */
 		kill_task = 1;
 	}
-	/* Check guarded storage registers */
+	/* Validate guarded storage registers */
 	cr2.val = S390_lowcore.cregs_save_area[2];
 	if (cr2.gse) {
 		if (!mci.gs) {
@@ -263,15 +321,26 @@ static int notrace s390_check_registers(union mci mci, int umode)
 			 * 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;
 }
-NOKPROBE_SYMBOL(s390_check_registers);
+NOKPROBE_SYMBOL(s390_validate_registers);
 
 /*
  * Backup the guest's machine check info to its description block
@@ -369,7 +438,7 @@ int notrace s390_do_machine_check(struct pt_regs *regs)
 			s390_handle_damage();
 		}
 	}
-	if (s390_check_registers(mci, user_mode(regs))) {
+	if (s390_validate_registers(mci, user_mode(regs))) {
 		/*
 		 * Couldn't restore all register contents for the
 		 * user space process -> mark task for termination.