s390: add a system call for guarded storage

This adds a new system call to enable the use of guarded storage for
user space processes. The system call takes two arguments, a command
and pointer to a guarded storage control block:

    s390_guarded_storage(int command, struct gs_cb *gs_cb);

The second argument is relevant only for the GS_SET_BC_CB command.

The commands in detail:

0 - GS_ENABLE
    Enable the guarded storage facility for the current task. The
    initial content of the guarded storage control block will be
    all zeros. After the enablement the user space code can use
    load-guarded-storage-controls instruction (LGSC) to load an
    arbitrary control block. While a task is enabled the kernel
    will save and restore the current content of the guarded
    storage registers on context switch.
1 - GS_DISABLE
    Disables the use of the guarded storage facility for the current
    task. The kernel will cease to save and restore the content of
    the guarded storage registers, the task specific content of
    these registers is lost.
2 - GS_SET_BC_CB
    Set a broadcast guarded storage control block. This is called
    per thread and stores a specific guarded storage control block
    in the task struct of the current task. This control block will
    be used for the broadcast event GS_BROADCAST.
3 - GS_CLEAR_BC_CB
    Clears the broadcast guarded storage control block. The guarded-
    storage control block is removed from the task struct that was
    established by GS_SET_BC_CB.
4 - GS_BROADCAST
    Sends a broadcast to all thread siblings of the current task.
    Every sibling that has established a broadcast guarded storage
    control block will load this control block and will be enabled
    for guarded storage. The broadcast guarded storage control block
    is used up, a second broadcast without a refresh of the stored
    control block with GS_SET_BC_CB will not have any effect.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

15 files changed, 322 insertions, 31 deletions

diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile
index 060ce548fe8b..aa5adbdaf200 100644
--- a/arch/s390/kernel/Makefile
+++ b/arch/s390/kernel/Makefile
@@ -57,7 +57,7 @@ obj-y	:= traps.o time.o process.o base.o early.o setup.o idle.o vtime.o
 obj-y	+= processor.o sys_s390.o ptrace.o signal.o cpcmd.o ebcdic.o nmi.o
 obj-y	+= debug.o irq.o ipl.o dis.o diag.o vdso.o als.o
 obj-y	+= sysinfo.o jump_label.o lgr.o os_info.o machine_kexec.o pgm_check.o
-obj-y	+= runtime_instr.o cache.o fpu.o dumpstack.o
+obj-y	+= runtime_instr.o cache.o fpu.o dumpstack.o guarded_storage.o
 obj-y	+= entry.o reipl.o relocate_kernel.o
 
 extra-y				+= head.o head64.o vmlinux.lds
diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c
index c4b3570ded5b..6bb29633e1f1 100644
--- a/arch/s390/kernel/asm-offsets.c
+++ b/arch/s390/kernel/asm-offsets.c
@@ -175,7 +175,7 @@ int main(void)
 	/* software defined ABI-relevant lowcore locations 0xe00 - 0xe20 */
 	OFFSET(__LC_DUMP_REIPL, lowcore, ipib);
 	/* hardware defined lowcore locations 0x1000 - 0x18ff */
-	OFFSET(__LC_VX_SAVE_AREA_ADDR, lowcore, vector_save_area_addr);
+	OFFSET(__LC_MCESAD, lowcore, mcesad);
 	OFFSET(__LC_EXT_PARAMS2, lowcore, ext_params2);
 	OFFSET(__LC_FPREGS_SAVE_AREA, lowcore, floating_pt_save_area);
 	OFFSET(__LC_GPREGS_SAVE_AREA, lowcore, gpregs_save_area);
diff --git a/arch/s390/kernel/compat_wrapper.c b/arch/s390/kernel/compat_wrapper.c
index e89cc2e71db1..986642a3543b 100644
--- a/arch/s390/kernel/compat_wrapper.c
+++ b/arch/s390/kernel/compat_wrapper.c
@@ -178,4 +178,5 @@ COMPAT_SYSCALL_WRAP3(getpeername, int, fd, struct sockaddr __user *, usockaddr,
 COMPAT_SYSCALL_WRAP6(sendto, int, fd, void __user *, buff, size_t, len, unsigned int, flags, struct sockaddr __user *, addr, int, addr_len);
 COMPAT_SYSCALL_WRAP3(mlock2, unsigned long, start, size_t, len, int, flags);
 COMPAT_SYSCALL_WRAP6(copy_file_range, int, fd_in, loff_t __user *, off_in, int, fd_out, loff_t __user *, off_out, size_t, len, unsigned int, flags);
+COMPAT_SYSCALL_WRAP2(s390_guarded_storage, int, command, struct gs_cb *, gs_cb);
 COMPAT_SYSCALL_WRAP5(statx, int, dfd, const char __user *, path, unsigned, flags, unsigned, mask, struct statx __user *, buffer);
diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
index 4e65c79cc5f2..95298a41076f 100644
--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -358,6 +358,8 @@ static __init void detect_machine_facilities(void)
 		S390_lowcore.machine_flags |= MACHINE_FLAG_NX;
 		__ctl_set_bit(0, 20);
 	}
+	if (test_facility(133))
+		S390_lowcore.machine_flags |= MACHINE_FLAG_GS;
 }
 
 static inline void save_vector_registers(void)
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 6a7d737d514c..fa8b8f28e08b 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -47,7 +47,7 @@ STACK_SIZE  = 1 << STACK_SHIFT
 STACK_INIT = STACK_SIZE - STACK_FRAME_OVERHEAD - __PT_SIZE
 
 _TIF_WORK	= (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \
-		   _TIF_UPROBE)
+		   _TIF_UPROBE | _TIF_GUARDED_STORAGE)
 _TIF_TRACE	= (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP | \
 		   _TIF_SYSCALL_TRACEPOINT)
 _CIF_WORK	= (_CIF_MCCK_PENDING | _CIF_ASCE_PRIMARY | \
@@ -332,6 +332,8 @@ ENTRY(system_call)
 	TSTMSK	__TI_flags(%r12),_TIF_UPROBE
 	jo	.Lsysc_uprobe_notify
 #endif
+	TSTMSK	__TI_flags(%r12),_TIF_GUARDED_STORAGE
+	jo	.Lsysc_guarded_storage
 	TSTMSK	__PT_FLAGS(%r11),_PIF_PER_TRAP
 	jo	.Lsysc_singlestep
 	TSTMSK	__TI_flags(%r12),_TIF_SIGPENDING
@@ -409,6 +411,14 @@ ENTRY(system_call)
 #endif
 
 #
+# _TIF_GUARDED_STORAGE is set, call guarded_storage_load
+#
+.Lsysc_guarded_storage:
+	lgr	%r2,%r11		# pass pointer to pt_regs
+	larl	%r14,.Lsysc_return
+	jg	gs_load_bc_cb
+
+#
 # _PIF_PER_TRAP is set, call do_per_trap
 #
 .Lsysc_singlestep:
@@ -663,6 +673,8 @@ ENTRY(io_int_handler)
 	jo	.Lio_sigpending
 	TSTMSK	__TI_flags(%r12),_TIF_NOTIFY_RESUME
 	jo	.Lio_notify_resume
+	TSTMSK	__TI_flags(%r12),_TIF_GUARDED_STORAGE
+	jo	.Lio_guarded_storage
 	TSTMSK	__LC_CPU_FLAGS,_CIF_FPU
 	jo	.Lio_vxrs
 	TSTMSK	__LC_CPU_FLAGS,(_CIF_ASCE_PRIMARY|_CIF_ASCE_SECONDARY)
@@ -697,6 +709,18 @@ ENTRY(io_int_handler)
 	jg	load_fpu_regs
 
 #
+# _TIF_GUARDED_STORAGE is set, call guarded_storage_load
+#
+.Lio_guarded_storage:
+	# TRACE_IRQS_ON already done at .Lio_return
+	ssm	__LC_SVC_NEW_PSW	# reenable interrupts
+	lgr	%r2,%r11		# pass pointer to pt_regs
+	brasl	%r14,gs_load_bc_cb
+	ssm	__LC_PGM_NEW_PSW	# disable I/O and ext. interrupts
+	TRACE_IRQS_OFF
+	j	.Lio_return
+
+#
 # _TIF_NEED_RESCHED is set, call schedule
 #
 .Lio_reschedule:
diff --git a/arch/s390/kernel/entry.h b/arch/s390/kernel/entry.h
index 33f901865326..dbf5f7e18246 100644
--- a/arch/s390/kernel/entry.h
+++ b/arch/s390/kernel/entry.h
@@ -74,12 +74,14 @@ long sys_sigreturn(void);
 
 long sys_s390_personality(unsigned int personality);
 long sys_s390_runtime_instr(int command, int signum);
+long sys_s390_guarded_storage(int command, struct gs_cb __user *);
 long sys_s390_pci_mmio_write(unsigned long, const void __user *, size_t);
 long sys_s390_pci_mmio_read(unsigned long, void __user *, size_t);
 
 DECLARE_PER_CPU(u64, mt_cycles[8]);
 
 void verify_facilities(void);
+void gs_load_bc_cb(struct pt_regs *regs);
 void set_fs_fixup(void);
 
 #endif /* _ENTRY_H */
diff --git a/arch/s390/kernel/guarded_storage.c b/arch/s390/kernel/guarded_storage.c
new file mode 100644
index 000000000000..6f064745c3b1
--- /dev/null
+++ b/arch/s390/kernel/guarded_storage.c
@@ -0,0 +1,128 @@
+/*
+ * Copyright IBM Corp. 2016
+ * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/syscalls.h>
+#include <linux/signal.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <asm/guarded_storage.h>
+#include "entry.h"
+
+void exit_thread_gs(void)
+{
+	kfree(current->thread.gs_cb);
+	kfree(current->thread.gs_bc_cb);
+	current->thread.gs_cb = current->thread.gs_bc_cb = NULL;
+}
+
+static int gs_enable(void)
+{
+	struct gs_cb *gs_cb;
+
+	if (!current->thread.gs_cb) {
+		gs_cb = kzalloc(sizeof(*gs_cb), GFP_KERNEL);
+		if (!gs_cb)
+			return -ENOMEM;
+		gs_cb->gsd = 25;
+		preempt_disable();
+		__ctl_set_bit(2, 4);
+		load_gs_cb(gs_cb);
+		current->thread.gs_cb = gs_cb;
+		preempt_enable();
+	}
+	return 0;
+}
+
+static int gs_disable(void)
+{
+	if (current->thread.gs_cb) {
+		preempt_disable();
+		kfree(current->thread.gs_cb);
+		current->thread.gs_cb = NULL;
+		__ctl_clear_bit(2, 4);
+		preempt_enable();
+	}
+	return 0;
+}
+
+static int gs_set_bc_cb(struct gs_cb __user *u_gs_cb)
+{
+	struct gs_cb *gs_cb;
+
+	gs_cb = current->thread.gs_bc_cb;
+	if (!gs_cb) {
+		gs_cb = kzalloc(sizeof(*gs_cb), GFP_KERNEL);
+		if (!gs_cb)
+			return -ENOMEM;
+		current->thread.gs_bc_cb = gs_cb;
+	}
+	if (copy_from_user(gs_cb, u_gs_cb, sizeof(*gs_cb)))
+		return -EFAULT;
+	return 0;
+}
+
+static int gs_clear_bc_cb(void)
+{
+	struct gs_cb *gs_cb;
+
+	gs_cb = current->thread.gs_bc_cb;
+	current->thread.gs_bc_cb = NULL;
+	kfree(gs_cb);
+	return 0;
+}
+
+void gs_load_bc_cb(struct pt_regs *regs)
+{
+	struct gs_cb *gs_cb;
+
+	preempt_disable();
+	clear_thread_flag(TIF_GUARDED_STORAGE);
+	gs_cb = current->thread.gs_bc_cb;
+	if (gs_cb) {
+		kfree(current->thread.gs_cb);
+		current->thread.gs_bc_cb = NULL;
+		__ctl_set_bit(2, 4);
+		load_gs_cb(gs_cb);
+		current->thread.gs_cb = gs_cb;
+	}
+	preempt_enable();
+}
+
+static int gs_broadcast(void)
+{
+	struct task_struct *sibling;
+
+	read_lock(&tasklist_lock);
+	for_each_thread(current, sibling) {
+		if (!sibling->thread.gs_bc_cb)
+			continue;
+		if (test_and_set_tsk_thread_flag(sibling, TIF_GUARDED_STORAGE))
+			kick_process(sibling);
+	}
+	read_unlock(&tasklist_lock);
+	return 0;
+}
+
+SYSCALL_DEFINE2(s390_guarded_storage, int, command,
+		struct gs_cb __user *, gs_cb)
+{
+	if (!MACHINE_HAS_GS)
+		return -EOPNOTSUPP;
+	switch (command) {
+	case GS_ENABLE:
+		return gs_enable();
+	case GS_DISABLE:
+		return gs_disable();
+	case GS_SET_BC_CB:
+		return gs_set_bc_cb(gs_cb);
+	case GS_CLEAR_BC_CB:
+		return gs_clear_bc_cb();
+	case GS_BROADCAST:
+		return gs_broadcast();
+	default:
+		return -EINVAL;
+	}
+}
diff --git a/arch/s390/kernel/machine_kexec.c b/arch/s390/kernel/machine_kexec.c
index 3074c1d83829..db5658daf994 100644
--- a/arch/s390/kernel/machine_kexec.c
+++ b/arch/s390/kernel/machine_kexec.c
@@ -27,6 +27,7 @@
 #include <asm/cacheflush.h>
 #include <asm/os_info.h>
 #include <asm/switch_to.h>
+#include <asm/nmi.h>
 
 typedef void (*relocate_kernel_t)(kimage_entry_t *, unsigned long);
 
@@ -102,6 +103,8 @@ static void __do_machine_kdump(void *image)
  */
 static noinline void __machine_kdump(void *image)
 {
+	struct mcesa *mcesa;
+	unsigned long cr2_old, cr2_new;
 	int this_cpu, cpu;
 
 	lgr_info_log();
@@ -114,8 +117,16 @@ static noinline void __machine_kdump(void *image)
 			continue;
 	}
 	/* Store status of the boot CPU */
+	mcesa = (struct mcesa *)(S390_lowcore.mcesad & MCESA_ORIGIN_MASK);
 	if (MACHINE_HAS_VX)
-		save_vx_regs((void *) &S390_lowcore.vector_save_area);
+		save_vx_regs((__vector128 *) mcesa->vector_save_area);
+	if (MACHINE_HAS_GS) {
+		__ctl_store(cr2_old, 2, 2);
+		cr2_new = cr2_old | (1UL << 4);
+		__ctl_load(cr2_new, 2, 2);
+		save_gs_cb((struct gs_cb *) mcesa->guarded_storage_save_area);
+		__ctl_load(cr2_old, 2, 2);
+	}
 	/*
 	 * To create a good backchain for this CPU in the dump store_status
 	 * is passed the address of a function. The address is saved into
diff --git a/arch/s390/kernel/nmi.c b/arch/s390/kernel/nmi.c
index 9bf8327154ee..985589523970 100644
--- a/arch/s390/kernel/nmi.c
+++ b/arch/s390/kernel/nmi.c
@@ -106,6 +106,7 @@ static int notrace s390_validate_registers(union mci mci, int umode)
 	int kill_task;
 	u64 zero;
 	void *fpt_save_area;
+	struct mcesa *mcesa;
 
 	kill_task = 0;
 	zero = 0;
@@ -165,6 +166,7 @@ static int notrace s390_validate_registers(union mci mci, int umode)
 			     : : "Q" (S390_lowcore.fpt_creg_save_area));
 	}
 
+	mcesa = (struct mcesa *)(S390_lowcore.mcesad & MCESA_ORIGIN_MASK);
 	if (!MACHINE_HAS_VX) {
 		/* Validate floating point registers */
 		asm volatile(
@@ -209,8 +211,8 @@ static int notrace s390_validate_registers(union mci mci, int umode)
 			"	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 *)
-				 &S390_lowcore.vector_save_area) : "1");
+			: : "Q" (*(struct vx_array *) mcesa->vector_save_area)
+			: "1");
 		__ctl_load(S390_lowcore.cregs_save_area[0], 0, 0);
 	}
 	/* Validate access registers */
@@ -224,6 +226,19 @@ static int notrace s390_validate_registers(union mci mci, int umode)
 		 */
 		kill_task = 1;
 	}
+	/* Validate guarded storage registers */
+	if (MACHINE_HAS_GS && (S390_lowcore.cregs_save_area[2] & (1UL << 4))) {
+		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);
+	}
 	/*
 	 * We don't even try to validate the TOD register, since we simply
 	 * can't write something sensible into that register.
diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index f29e41c5e2ec..999d7154bbdc 100644
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -73,8 +73,10 @@ extern void kernel_thread_starter(void);
  */
 void exit_thread(struct task_struct *tsk)
 {
-	if (tsk == current)
+	if (tsk == current) {
 		exit_thread_runtime_instr();
+		exit_thread_gs();
+	}
 }
 
 void flush_thread(void)
@@ -159,6 +161,9 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long new_stackp,
 	/* Don't copy runtime instrumentation info */
 	p->thread.ri_cb = NULL;
 	frame->childregs.psw.mask &= ~PSW_MASK_RI;
+	/* Don't copy guarded storage control block */
+	p->thread.gs_cb = NULL;
+	p->thread.gs_bc_cb = NULL;
 
 	/* Set a new TLS ?  */
 	if (clone_flags & CLONE_SETTLS) {
diff --git a/arch/s390/kernel/processor.c b/arch/s390/kernel/processor.c
index 928b929a6261..c73709869447 100644
--- a/arch/s390/kernel/processor.c
+++ b/arch/s390/kernel/processor.c
@@ -95,7 +95,7 @@ static void show_cpu_summary(struct seq_file *m, void *v)
 {
 	static const char *hwcap_str[] = {
 		"esan3", "zarch", "stfle", "msa", "ldisp", "eimm", "dfp",
-		"edat", "etf3eh", "highgprs", "te", "vx", "vxd", "vxe"
+		"edat", "etf3eh", "highgprs", "te", "vx", "vxd", "vxe", "gs"
 	};
 	static const char * const int_hwcap_str[] = {
 		"sie"
diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index c14df0a1ec3c..c933e255b5d5 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -44,30 +44,42 @@ void update_cr_regs(struct task_struct *task)
 	struct pt_regs *regs = task_pt_regs(task);
 	struct thread_struct *thread = &task->thread;
 	struct per_regs old, new;
-
+	unsigned long cr0_old, cr0_new;
+	unsigned long cr2_old, cr2_new;
+	int cr0_changed, cr2_changed;
+
+	__ctl_store(cr0_old, 0, 0);
+	__ctl_store(cr2_old, 2, 2);
+	cr0_new = cr0_old;
+	cr2_new = cr2_old;
 	/* Take care of the enable/disable of transactional execution. */
 	if (MACHINE_HAS_TE) {
-		unsigned long cr, cr_new;
-
-		__ctl_store(cr, 0, 0);
 		/* Set or clear transaction execution TXC bit 8. */
-		cr_new = cr | (1UL << 55);
+		cr0_new |= (1UL << 55);
 		if (task->thread.per_flags & PER_FLAG_NO_TE)
-			cr_new &= ~(1UL << 55);
-		if (cr_new != cr)
-			__ctl_load(cr_new, 0, 0);
+			cr0_new &= ~(1UL << 55);
 		/* Set or clear transaction execution TDC bits 62 and 63. */
-		__ctl_store(cr, 2, 2);
-		cr_new = cr & ~3UL;
+		cr2_new &= ~3UL;
 		if (task->thread.per_flags & PER_FLAG_TE_ABORT_RAND) {
 			if (task->thread.per_flags & PER_FLAG_TE_ABORT_RAND_TEND)
-				cr_new |= 1UL;
+				cr2_new |= 1UL;
 			else
-				cr_new |= 2UL;
+				cr2_new |= 2UL;
 		}
-		if (cr_new != cr)
-			__ctl_load(cr_new, 2, 2);
 	}
+	/* Take care of enable/disable of guarded storage. */
+	if (MACHINE_HAS_GS) {
+		cr2_new &= ~(1UL << 4);
+		if (task->thread.gs_cb)
+			cr2_new |= (1UL << 4);
+	}
+	/* Load control register 0/2 iff changed */
+	cr0_changed = cr0_new != cr0_old;
+	cr2_changed = cr2_new != cr2_old;
+	if (cr0_changed)
+		__ctl_load(cr0_new, 0, 0);
+	if (cr2_changed)
+		__ctl_load(cr2_new, 2, 2);
 	/* Copy user specified PER registers */
 	new.control = thread->per_user.control;
 	new.start = thread->per_user.start;
@@ -1137,6 +1149,36 @@ static int s390_system_call_set(struct task_struct *target,
 				  data, 0, sizeof(unsigned int));
 }
 
+static int s390_gs_cb_get(struct task_struct *target,
+			  const struct user_regset *regset,
+			  unsigned int pos, unsigned int count,
+			  void *kbuf, void __user *ubuf)
+{
+	struct gs_cb *data = target->thread.gs_cb;
+
+	if (!MACHINE_HAS_GS)
+		return -ENODEV;
+	if (!data)
+		return -ENODATA;
+	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+				   data, 0, sizeof(struct gs_cb));
+}
+
+static int s390_gs_cb_set(struct task_struct *target,
+			  const struct user_regset *regset,
+			  unsigned int pos, unsigned int count,
+			  const void *kbuf, const void __user *ubuf)
+{
+	struct gs_cb *data = target->thread.gs_cb;
+
+	if (!MACHINE_HAS_GS)
+		return -ENODEV;
+	if (!data)
+		return -ENODATA;
+	return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+				  data, 0, sizeof(struct gs_cb));
+}
+
 static const struct user_regset s390_regsets[] = {
 	{
 		.core_note_type = NT_PRSTATUS,
@@ -1194,6 +1236,14 @@ static const struct user_regset s390_regsets[] = {
 		.get = s390_vxrs_high_get,
 		.set = s390_vxrs_high_set,
 	},
+	{
+		.core_note_type = NT_S390_GS_CB,
+		.n = sizeof(struct gs_cb) / sizeof(__u64),
+		.size = sizeof(__u64),
+		.align = sizeof(__u64),
+		.get = s390_gs_cb_get,
+		.set = s390_gs_cb_set,
+	},
 };
 
 static const struct user_regset_view user_s390_view = {
@@ -1422,6 +1472,14 @@ static const struct user_regset s390_compat_regsets[] = {
 		.get = s390_compat_regs_high_get,
 		.set = s390_compat_regs_high_set,
 	},
+	{
+		.core_note_type = NT_S390_GS_CB,
+		.n = sizeof(struct gs_cb) / sizeof(__u64),
+		.size = sizeof(__u64),
+		.align = sizeof(__u64),
+		.get = s390_gs_cb_get,
+		.set = s390_gs_cb_set,
+	},
 };
 
 static const struct user_regset_view user_s390_compat_view = {
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index 911dc0b49be0..3ae756c0db3d 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -339,9 +339,15 @@ static void __init setup_lowcore(void)
 	lc->stfl_fac_list = S390_lowcore.stfl_fac_list;
 	memcpy(lc->stfle_fac_list, S390_lowcore.stfle_fac_list,
 	       MAX_FACILITY_BIT/8);
-	if (MACHINE_HAS_VX)
-		lc->vector_save_area_addr =
-			(unsigned long) &lc->vector_save_area;
+	if (MACHINE_HAS_VX || MACHINE_HAS_GS) {
+		unsigned long bits, size;
+
+		bits = MACHINE_HAS_GS ? 11 : 10;
+		size = 1UL << bits;
+		lc->mcesad = (__u64) memblock_virt_alloc(size, size);
+		if (MACHINE_HAS_GS)
+			lc->mcesad |= bits;
+	}
 	lc->vdso_per_cpu_data = (unsigned long) &lc->paste[0];
 	lc->sync_enter_timer = S390_lowcore.sync_enter_timer;
 	lc->async_enter_timer = S390_lowcore.async_enter_timer;
@@ -779,6 +785,12 @@ static int __init setup_hwcaps(void)
 			elf_hwcap |= HWCAP_S390_VXRS_BCD;
 	}
 
+	/*
+	 * Guarded storage support HWCAP_S390_GS is bit 12.
+	 */
+	if (MACHINE_HAS_GS)
+		elf_hwcap |= HWCAP_S390_GS;
+
 	get_cpu_id(&cpu_id);
 	add_device_randomness(&cpu_id, sizeof(cpu_id));
 	switch (cpu_id.machine) {
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 47a973b5b4f1..286bcee800f4 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -51,6 +51,7 @@
 #include <asm/os_info.h>
 #include <asm/sigp.h>
 #include <asm/idle.h>
+#include <asm/nmi.h>
 #include "entry.h"
 
 enum {
@@ -78,6 +79,8 @@ struct pcpu {
 static u8 boot_core_type;
 static struct pcpu pcpu_devices[NR_CPUS];
 
+static struct kmem_cache *pcpu_mcesa_cache;
+
 unsigned int smp_cpu_mt_shift;
 EXPORT_SYMBOL(smp_cpu_mt_shift);
 
@@ -188,8 +191,10 @@ static void pcpu_ec_call(struct pcpu *pcpu, int ec_bit)
 static int pcpu_alloc_lowcore(struct pcpu *pcpu, int cpu)
 {
 	unsigned long async_stack, panic_stack;
+	unsigned long mcesa_origin, mcesa_bits;
 	struct lowcore *lc;
 
+	mcesa_origin = mcesa_bits = 0;
 	if (pcpu != &pcpu_devices[0]) {
 		pcpu->lowcore =	(struct lowcore *)
 			__get_free_pages(GFP_KERNEL | GFP_DMA, LC_ORDER);
@@ -197,20 +202,27 @@ static int pcpu_alloc_lowcore(struct pcpu *pcpu, int cpu)
 		panic_stack = __get_free_page(GFP_KERNEL);
 		if (!pcpu->lowcore || !panic_stack || !async_stack)
 			goto out;
+		if (MACHINE_HAS_VX || MACHINE_HAS_GS) {
+			mcesa_origin = (unsigned long)
+				kmem_cache_alloc(pcpu_mcesa_cache, GFP_KERNEL);
+			if (!mcesa_origin)
+				goto out;
+			mcesa_bits = MACHINE_HAS_GS ? 11 : 0;
+		}
 	} else {
 		async_stack = pcpu->lowcore->async_stack - ASYNC_FRAME_OFFSET;
 		panic_stack = pcpu->lowcore->panic_stack - PANIC_FRAME_OFFSET;
+		mcesa_origin = pcpu->lowcore->mcesad & MCESA_ORIGIN_MASK;
+		mcesa_bits = pcpu->lowcore->mcesad & MCESA_LC_MASK;
 	}
 	lc = pcpu->lowcore;
 	memcpy(lc, &S390_lowcore, 512);
 	memset((char *) lc + 512, 0, sizeof(*lc) - 512);
 	lc->async_stack = async_stack + ASYNC_FRAME_OFFSET;
 	lc->panic_stack = panic_stack + PANIC_FRAME_OFFSET;
+	lc->mcesad = mcesa_origin | mcesa_bits;
 	lc->cpu_nr = cpu;
 	lc->spinlock_lockval = arch_spin_lockval(cpu);
-	if (MACHINE_HAS_VX)
-		lc->vector_save_area_addr =
-			(unsigned long) &lc->vector_save_area;
 	if (vdso_alloc_per_cpu(lc))
 		goto out;
 	lowcore_ptr[cpu] = lc;
@@ -218,6 +230,9 @@ static int pcpu_alloc_lowcore(struct pcpu *pcpu, int cpu)
 	return 0;
 out:
 	if (pcpu != &pcpu_devices[0]) {
+		if (mcesa_origin)
+			kmem_cache_free(pcpu_mcesa_cache,
+					(void *) mcesa_origin);
 		free_page(panic_stack);
 		free_pages(async_stack, ASYNC_ORDER);
 		free_pages((unsigned long) pcpu->lowcore, LC_ORDER);
@@ -229,11 +244,17 @@ out:
 
 static void pcpu_free_lowcore(struct pcpu *pcpu)
 {
+	unsigned long mcesa_origin;
+
 	pcpu_sigp_retry(pcpu, SIGP_SET_PREFIX, 0);
 	lowcore_ptr[pcpu - pcpu_devices] = NULL;
 	vdso_free_per_cpu(pcpu->lowcore);
 	if (pcpu == &pcpu_devices[0])
 		return;
+	if (MACHINE_HAS_VX || MACHINE_HAS_GS) {
+		mcesa_origin = pcpu->lowcore->mcesad & MCESA_ORIGIN_MASK;
+		kmem_cache_free(pcpu_mcesa_cache, (void *) mcesa_origin);
+	}
 	free_page(pcpu->lowcore->panic_stack-PANIC_FRAME_OFFSET);
 	free_pages(pcpu->lowcore->async_stack-ASYNC_FRAME_OFFSET, ASYNC_ORDER);
 	free_pages((unsigned long) pcpu->lowcore, LC_ORDER);
@@ -550,9 +571,11 @@ int smp_store_status(int cpu)
 	if (__pcpu_sigp_relax(pcpu->address, SIGP_STORE_STATUS_AT_ADDRESS,
 			      pa) != SIGP_CC_ORDER_CODE_ACCEPTED)
 		return -EIO;
-	if (!MACHINE_HAS_VX)
+	if (!MACHINE_HAS_VX && !MACHINE_HAS_GS)
 		return 0;
-	pa = __pa(pcpu->lowcore->vector_save_area_addr);
+	pa = __pa(pcpu->lowcore->mcesad & MCESA_ORIGIN_MASK);
+	if (MACHINE_HAS_GS)
+		pa |= pcpu->lowcore->mcesad & MCESA_LC_MASK;
 	if (__pcpu_sigp_relax(pcpu->address, SIGP_STORE_ADDITIONAL_STATUS,
 			      pa) != SIGP_CC_ORDER_CODE_ACCEPTED)
 		return -EIO;
@@ -897,12 +920,22 @@ void __init smp_fill_possible_mask(void)
 
 void __init smp_prepare_cpus(unsigned int max_cpus)
 {
+	unsigned long size;
+
 	/* request the 0x1201 emergency signal external interrupt */
 	if (register_external_irq(EXT_IRQ_EMERGENCY_SIG, do_ext_call_interrupt))
 		panic("Couldn't request external interrupt 0x1201");
 	/* request the 0x1202 external call external interrupt */
 	if (register_external_irq(EXT_IRQ_EXTERNAL_CALL, do_ext_call_interrupt))
 		panic("Couldn't request external interrupt 0x1202");
+	/* create slab cache for the machine-check-extended-save-areas */
+	if (MACHINE_HAS_VX || MACHINE_HAS_GS) {
+		size = 1UL << (MACHINE_HAS_GS ? 11 : 10);
+		pcpu_mcesa_cache = kmem_cache_create("nmi_save_areas",
+						     size, size, 0, NULL);
+		if (!pcpu_mcesa_cache)
+			panic("Couldn't create nmi save area cache");
+	}
 }
 
 void __init smp_prepare_boot_cpu(void)
diff --git a/arch/s390/kernel/syscalls.S b/arch/s390/kernel/syscalls.S
index 2659b5cfeddb..54fce7b065de 100644
--- a/arch/s390/kernel/syscalls.S
+++ b/arch/s390/kernel/syscalls.S
@@ -386,5 +386,5 @@ SYSCALL(sys_mlock2,compat_sys_mlock2)
 SYSCALL(sys_copy_file_range,compat_sys_copy_file_range) /* 375 */
 SYSCALL(sys_preadv2,compat_sys_preadv2)
 SYSCALL(sys_pwritev2,compat_sys_pwritev2)
-NI_SYSCALL
+SYSCALL(sys_s390_guarded_storage,compat_sys_s390_guarded_storage) /* 378 */
 SYSCALL(sys_statx,compat_sys_statx)