RISC-V: User-facing API

This patch contains code that is in some way visible to the user:
including via system calls, the VDSO, module loading and signal
handling.  It also contains some generic code that is ABI visible.

Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>

arch/riscv/include/uapi/asm/hwcap.h

@@ -0,0 +1,36 @@
+/*
+ * Copied from arch/arm64/include/asm/hwcap.h
+ *
+ * Copyright (C) 2012 ARM Ltd.
+ * Copyright (C) 2017 SiFive
+ *
+ * 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 __UAPI_ASM_HWCAP_H
+#define __UAPI_ASM_HWCAP_H
+
+/*
+ * Linux saves the floating-point registers according to the ISA Linux is
+ * executing on, as opposed to the ISA the user program is compiled for.  This
+ * is necessary for a handful of esoteric use cases: for example, userpsace
+ * threading libraries must be able to examine the actual machine state in
+ * order to fully reconstruct the state of a thread.
+ */
+#define COMPAT_HWCAP_ISA_I	(1 << ('I' - 'A'))
+#define COMPAT_HWCAP_ISA_M	(1 << ('M' - 'A'))
+#define COMPAT_HWCAP_ISA_A	(1 << ('A' - 'A'))
+#define COMPAT_HWCAP_ISA_F	(1 << ('F' - 'A'))
+#define COMPAT_HWCAP_ISA_D	(1 << ('D' - 'A'))
+#define COMPAT_HWCAP_ISA_C	(1 << ('C' - 'A'))
+
+#endif