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>

3 files changed, 79 insertions, 1 deletions

diff --git a/arch/s390/include/uapi/asm/Kbuild b/arch/s390/include/uapi/asm/Kbuild
index 6848ba5c1454..86b761e583e3 100644
--- a/arch/s390/include/uapi/asm/Kbuild
+++ b/arch/s390/include/uapi/asm/Kbuild
@@ -12,6 +12,7 @@ header-y += dasd.h
 header-y += debug.h
 header-y += errno.h
 header-y += fcntl.h
+header-y += guarded_storage.h
 header-y += hypfs.h
 header-y += ioctl.h
 header-y += ioctls.h
diff --git a/arch/s390/include/uapi/asm/guarded_storage.h b/arch/s390/include/uapi/asm/guarded_storage.h
new file mode 100644
index 000000000000..852850e8e17e
--- /dev/null
+++ b/arch/s390/include/uapi/asm/guarded_storage.h
@@ -0,0 +1,77 @@
+#ifndef _GUARDED_STORAGE_H
+#define _GUARDED_STORAGE_H
+
+#include <linux/types.h>
+
+struct gs_cb {
+	__u64 reserved;
+	__u64 gsd;
+	__u64 gssm;
+	__u64 gs_epl_a;
+};
+
+struct gs_epl {
+	__u8 pad1;
+	union {
+		__u8 gs_eam;
+		struct {
+			__u8	: 6;
+			__u8 e	: 1;
+			__u8 b	: 1;
+		};
+	};
+	union {
+		__u8 gs_eci;
+		struct {
+			__u8 tx	: 1;
+			__u8 cx	: 1;
+			__u8	: 5;
+			__u8 in	: 1;
+		};
+	};
+	union {
+		__u8 gs_eai;
+		struct {
+			__u8	: 1;
+			__u8 t	: 1;
+			__u8 as	: 2;
+			__u8 ar	: 4;
+		};
+	};
+	__u32 pad2;
+	__u64 gs_eha;
+	__u64 gs_eia;
+	__u64 gs_eoa;
+	__u64 gs_eir;
+	__u64 gs_era;
+};
+
+#define GS_ENABLE	0
+#define	GS_DISABLE	1
+#define GS_SET_BC_CB	2
+#define GS_CLEAR_BC_CB	3
+#define GS_BROADCAST	4
+
+static inline void load_gs_cb(struct gs_cb *gs_cb)
+{
+	asm volatile(".insn rxy,0xe3000000004d,0,%0" : : "Q" (*gs_cb));
+}
+
+static inline void store_gs_cb(struct gs_cb *gs_cb)
+{
+	asm volatile(".insn rxy,0xe30000000049,0,%0" : : "Q" (*gs_cb));
+}
+
+static inline void save_gs_cb(struct gs_cb *gs_cb)
+{
+	if (gs_cb)
+		store_gs_cb(gs_cb);
+}
+
+static inline void restore_gs_cb(struct gs_cb *gs_cb)
+{
+	if (gs_cb)
+		load_gs_cb(gs_cb);
+}
+
+#endif /* _GUARDED_STORAGE_H */
diff --git a/arch/s390/include/uapi/asm/unistd.h b/arch/s390/include/uapi/asm/unistd.h
index 152de9b796e1..ea42290e7d51 100644
--- a/arch/s390/include/uapi/asm/unistd.h
+++ b/arch/s390/include/uapi/asm/unistd.h
@@ -313,7 +313,7 @@
 #define __NR_copy_file_range	375
 #define __NR_preadv2		376
 #define __NR_pwritev2		377
-/* Number 378 is reserved for guarded storage */
+#define __NR_s390_guarded_storage	378
 #define __NR_statx		379
 #define NR_syscalls 380