s390/gs: add regset for the guarded storage broadcast control block

The guarded storage interface allows to register a control block for
each thread that is activated with the guarded storage broadcast event.
To retrieve the complete state of a process from the kernel a register
set for the stored broadcast control block is required.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/ptrace.c

@@ -1171,10 +1171,48 @@ static int s390_gs_cb_set(struct task_struct *target,
 {
 	struct gs_cb *data = target->thread.gs_cb;
 
+	if (!MACHINE_HAS_GS)
+		return -ENODEV;
+	if (!data) {
+		data = kzalloc(sizeof(*data), GFP_KERNEL);
+		if (!data)
+			return -ENOMEM;
+		target->thread.gs_cb = data;
+	}
+	return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+				  data, 0, sizeof(struct gs_cb));
+}
+
+static int s390_gs_bc_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_bc_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_bc_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_bc_cb;
+
+	if (!MACHINE_HAS_GS)
+		return -ENODEV;
+	if (!data) {
+		data = kzalloc(sizeof(*data), GFP_KERNEL);
+		if (!data)
+			return -ENOMEM;
+		target->thread.gs_bc_cb = data;
+	}
 	return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 				  data, 0, sizeof(struct gs_cb));
 }
@@ -1244,6 +1282,14 @@ static const struct user_regset s390_regsets[] = {
 		.get = s390_gs_cb_get,
 		.set = s390_gs_cb_set,
 	},
+	{
+		.core_note_type = NT_S390_GS_BC,
+		.n = sizeof(struct gs_cb) / sizeof(__u64),
+		.size = sizeof(__u64),
+		.align = sizeof(__u64),
+		.get = s390_gs_bc_get,
+		.set = s390_gs_bc_set,
+	},
 };
 
 static const struct user_regset_view user_s390_view = {

include/uapi/linux/elf.h

@@ -410,6 +410,7 @@ typedef struct elf64_shdr {
 #define NT_S390_VXRS_LOW	0x309	/* s390 vector registers 0-15 upper half */
 #define NT_S390_VXRS_HIGH	0x30a	/* s390 vector registers 16-31 */
 #define NT_S390_GS_CB	0x30b		/* s390 guarded storage registers */
+#define NT_S390_GS_BC	0x30c		/* s390 guarded storage broadcast control block */
 #define NT_ARM_VFP	0x400		/* ARM VFP/NEON registers */
 #define NT_ARM_TLS	0x401		/* ARM TLS register */
 #define NT_ARM_HW_BREAK	0x402		/* ARM hardware breakpoint registers */