arm64: Signal handling support

This patch adds support for signal handling. The sigreturn is done via
VDSO, introduced by a previous patch. The SA_RESTORER is still defined
as it is required for 32-bit (compat) support but it is not to be used
for 64-bit applications.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>

arch/arm64/include/asm/sigcontext.h

@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_SIGCONTEXT_H
+#define __ASM_SIGCONTEXT_H
+
+#include <linux/types.h>
+
+/*
+ * Signal context structure - contains all info to do with the state
+ * before the signal handler was invoked.
+ */
+struct sigcontext {
+	__u64 fault_address;
+	/* AArch64 registers */
+	__u64 regs[31];
+	__u64 sp;
+	__u64 pc;
+	__u64 pstate;
+	/* 4K reserved for FP/SIMD state and future expansion */
+	__u8 __reserved[4096] __attribute__((__aligned__(16)));
+};
+
+/*
+ * Header to be used at the beginning of structures extending the user
+ * context. Such structures must be placed after the rt_sigframe on the stack
+ * and be 16-byte aligned. The last structure must be a dummy one with the
+ * magic and size set to 0.
+ */
+struct _aarch64_ctx {
+	__u32 magic;
+	__u32 size;
+};
+
+#define FPSIMD_MAGIC	0x46508001
+
+struct fpsimd_context {
+	struct _aarch64_ctx head;
+	__u32 fpsr;
+	__u32 fpcr;
+	__uint128_t vregs[32];
+};
+
+#ifdef __KERNEL__
+/*
+ * Auxiliary context saved in the sigcontext.__reserved array. Not exported to
+ * user space as it will change with the addition of new context. User space
+ * should check the magic/size information.
+ */
+struct aux_context {
+	struct fpsimd_context fpsimd;
+	/* additional context to be added before "end" */
+	struct _aarch64_ctx end;
+};
+#endif
+
+#endif