[PATCH v2 01/15] RISC-V: Build Infastructure

[Palmer Dabbelt <palmer at dabbelt dot com>]

This patch lays out the top-level orginazition of the RISC-V port.  It
contains all the Implies files as well as various other fragments of
build infastructure for the RISC-V port.  This contains the only change
to a shared file: config.h.in.

RISC-V is a family of base ISAs with optional extensions.  The base ISAs
are RV32I and RV64I, which are 32-bit and 64-bit integer-only ISAs.
Support for these live in sysdeps/riscv/rv{32,64}.  In addition to these
ISAs, our glibc port supports most of the currently-defined extensions:
the A extension for atomics, the M extension for multiplication, the C
extension for compressed instructions, and the F/D extensions for
single/double precision IEEE floating-point.  Most of these extensions
are handled by GCC, but glibc defines various floating-point wrappers
(in sysdeps/riscv/rv{32,64}/rv{f,d}) and emulation routines (in
sysdeps/riscv/soft-fp).

We support running glibc-based programs on Linux, the suppor for which
lives in sysdeps/unix/sysv/linux/riscv.
---
 config.h.in                                  |   5 +
 nptl/Makefile                                |   4 +
 sysdeps/riscv/Implies                        |   5 +
 sysdeps/riscv/Makefile                       |  49 +++++++
 sysdeps/riscv/Versions                       |   4 +
 sysdeps/riscv/configure                      |   5 +
 sysdeps/riscv/configure.ac                   |   4 +
 sysdeps/riscv/nptl/Makefile                  |  26 ++++
 sysdeps/riscv/preconfigure                   |  54 +++++++
 sysdeps/riscv/rv32/Implies-after             |   1 +
 sysdeps/riscv/rv32/rvd/Implies               |   2 +
 sysdeps/riscv/rv32/rvf/Implies               |   1 +
 sysdeps/riscv/rv64/Implies-after             |   1 +
 sysdeps/riscv/rv64/rvd/Implies               |   3 +
 sysdeps/riscv/rv64/rvf/Implies               |   1 +
 sysdeps/unix/sysv/linux/riscv/Implies        |   1 +
 sysdeps/unix/sysv/linux/riscv/Makefile       | 100 +++++++++++++
 sysdeps/unix/sysv/linux/riscv/Versions       |   5 +
 sysdeps/unix/sysv/linux/riscv/configure      | 210 +++++++++++++++++++++++++++
 sysdeps/unix/sysv/linux/riscv/configure.ac   |  33 +++++
 sysdeps/unix/sysv/linux/riscv/rv32/Implies   |   3 +
 sysdeps/unix/sysv/linux/riscv/rv64/Implies   |   3 +
 sysdeps/unix/sysv/linux/riscv/rv64/Makefile  |   4 +
 sysdeps/unix/sysv/linux/riscv/shlib-versions |  17 +++
 24 files changed, 541 insertions(+)
 create mode 100644 sysdeps/riscv/Implies
 create mode 100644 sysdeps/riscv/Makefile
 create mode 100644 sysdeps/riscv/Versions
 create mode 100644 sysdeps/riscv/configure
 create mode 100644 sysdeps/riscv/configure.ac
 create mode 100644 sysdeps/riscv/nptl/Makefile
 create mode 100644 sysdeps/riscv/preconfigure
 create mode 100644 sysdeps/riscv/rv32/Implies-after
 create mode 100644 sysdeps/riscv/rv32/rvd/Implies
 create mode 100644 sysdeps/riscv/rv32/rvf/Implies
 create mode 100644 sysdeps/riscv/rv64/Implies-after
 create mode 100644 sysdeps/riscv/rv64/rvd/Implies
 create mode 100644 sysdeps/riscv/rv64/rvf/Implies
 create mode 100644 sysdeps/unix/sysv/linux/riscv/Implies
 create mode 100644 sysdeps/unix/sysv/linux/riscv/Makefile
 create mode 100644 sysdeps/unix/sysv/linux/riscv/Versions
 create mode 100755 sysdeps/unix/sysv/linux/riscv/configure
 create mode 100644 sysdeps/unix/sysv/linux/riscv/configure.ac
 create mode 100644 sysdeps/unix/sysv/linux/riscv/rv32/Implies
 create mode 100644 sysdeps/unix/sysv/linux/riscv/rv64/Implies
 create mode 100644 sysdeps/unix/sysv/linux/riscv/rv64/Makefile
 create mode 100644 sysdeps/unix/sysv/linux/riscv/shlib-versions

diff --git a/config.h.in b/config.h.in
index d928e7dd867c..b0b7cf26cb4b 100644
--- a/config.h.in
+++ b/config.h.in
@@ -100,6 +100,11 @@
 /* AArch64 big endian ABI */
 #undef HAVE_AARCH64_BE
 
+/* RISC-V integer ABI for ld.so.  */
+#undef RISCV_ABI_XLEN
+
+/* RISC-V floating-point ABI for ld.so.  */
+#undef RISCV_ABI_FLEN
 
 /* Linux specific: minimum supported kernel version.  */
 #undef	__LINUX_KERNEL_VERSION
diff --git a/nptl/Makefile b/nptl/Makefile
index 60d036a1ea42..f62d19febf1d 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -611,6 +611,10 @@ else
 librt = $(common-objpfx)rt/librt.a
 endif
 
+# `make check' sometimes triggers a rebuild of librt.so using this Makefile,
+# which ignores librt's dependence on libpthread
+$(common-objpfx)rt/librt.so: $(shared-thread-library)
+
 $(objpfx)tst-cancel17: $(librt)
 $(objpfx)tst-cancelx17: $(librt)
 $(objpfx)tst-_res1mod2.so: $(objpfx)tst-_res1mod1.so
diff --git a/sysdeps/riscv/Implies b/sysdeps/riscv/Implies
new file mode 100644
index 000000000000..c88325b8be16
--- /dev/null
+++ b/sysdeps/riscv/Implies
@@ -0,0 +1,5 @@
+init_array
+
+ieee754/ldbl-128
+ieee754/dbl-64
+ieee754/flt-32
diff --git a/sysdeps/riscv/Makefile b/sysdeps/riscv/Makefile
new file mode 100644
index 000000000000..64060531a1d5
--- /dev/null
+++ b/sysdeps/riscv/Makefile
@@ -0,0 +1,49 @@
+ifneq ($(all-rtld-routines),)
+CFLAGS-rtld.c += -mno-plt
+CFLAGS-dl-load.c += -mno-plt
+CFLAGS-dl-cache.c += -mno-plt
+CFLAGS-dl-lookup.c += -mno-plt
+CFLAGS-dl-object.c += -mno-plt
+CFLAGS-dl-reloc.c += -mno-plt
+CFLAGS-dl-deps.c += -mno-plt
+CFLAGS-dl-runtime.c += -mno-plt
+CFLAGS-dl-error.c += -mno-plt
+CFLAGS-dl-init.c += -mno-plt
+CFLAGS-dl-fini.c += -mno-plt
+CFLAGS-dl-debug.c += -mno-plt
+CFLAGS-dl-misc.c += -mno-plt
+CFLAGS-dl-version.c += -mno-plt
+CFLAGS-dl-profile.c += -mno-plt
+CFLAGS-dl-conflict.c += -mno-plt
+CFLAGS-dl-tls.c += -mno-plt
+CFLAGS-dl-origin.c += -mno-plt
+CFLAGS-dl-scope.c += -mno-plt
+CFLAGS-dl-execstack.c += -mno-plt
+CFLAGS-dl-caller.c += -mno-plt
+CFLAGS-dl-open.c += -mno-plt
+CFLAGS-dl-close.c += -mno-plt
+CFLAGS-dl-sysdep.c += -mno-plt
+CFLAGS-dl-environ.c += -mno-plt
+CFLAGS-dl-minimal.c += -mno-plt
+CFLAGS-dl-static.c += -mno-plt
+CFLAGS-dl-brk.c += -mno-plt
+CFLAGS-dl-sbrk.c += -mno-plt
+CFLAGS-dl-getcwd.c += -mno-plt
+CFLAGS-dl-openat64.c += -mno-plt
+CFLAGS-dl-opendir.c += -mno-plt
+CFLAGS-dl-fxstatat64.c += -mno-plt
+endif
+
+CFLAGS-closedir.c += -mno-plt
+CFLAGS-exit.c += -mno-plt
+CFLAGS-cxa_atexit.c += -mno-plt
+
+ifeq ($(subdir),misc)
+sysdep_headers += sys/asm.h
+endif
+
+ASFLAGS-.os += $(pic-ccflag)
+
+ifeq ($(subdir),math)
+CPPFLAGS += -I../soft-fp
+endif
diff --git a/sysdeps/riscv/Versions b/sysdeps/riscv/Versions
new file mode 100644
index 000000000000..aafa348a2395
--- /dev/null
+++ b/sysdeps/riscv/Versions
@@ -0,0 +1,4 @@
+libc {
+  GLIBC_2.27 {
+  }
+}
diff --git a/sysdeps/riscv/configure b/sysdeps/riscv/configure
new file mode 100644
index 000000000000..8dc92a2e7920
--- /dev/null
+++ b/sysdeps/riscv/configure
@@ -0,0 +1,5 @@
+# This file is generated from configure.ac by Autoconf.  DO NOT EDIT!
+ # Local configure fragment for sysdeps/riscv/elf.
+
+$as_echo "#define PI_STATIC_AND_HIDDEN 1" >>confdefs.h
+
diff --git a/sysdeps/riscv/configure.ac b/sysdeps/riscv/configure.ac
new file mode 100644
index 000000000000..34f62d4b4b82
--- /dev/null
+++ b/sysdeps/riscv/configure.ac
@@ -0,0 +1,4 @@
+GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
+# Local configure fragment for sysdeps/riscv/elf.
+
+AC_DEFINE(PI_STATIC_AND_HIDDEN)
diff --git a/sysdeps/riscv/nptl/Makefile b/sysdeps/riscv/nptl/Makefile
new file mode 100644
index 000000000000..5a4be9b00e93
--- /dev/null
+++ b/sysdeps/riscv/nptl/Makefile
@@ -0,0 +1,26 @@
+# Makefile for sysdeps/riscv/nptl.
+# Copyright (C) 2005-2017 Free Software Foundation, Inc.
+# This file is part of the GNU C Library.
+#
+# The GNU C Library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# The GNU C Library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with the GNU C Library; if not, see
+# <http://www.gnu.org/licenses/>.
+
+ifeq ($(subdir),csu)
+gen-as-const-headers += tcb-offsets.sym
+endif
+
+ifeq ($(subdir),nptl)
+libpthread-sysdep_routines += nptl-sysdep
+libpthread-shared-only-routines += nptl-sysdep
+endif
diff --git a/sysdeps/riscv/preconfigure b/sysdeps/riscv/preconfigure
new file mode 100644
index 000000000000..e118a5ed28f6
--- /dev/null
+++ b/sysdeps/riscv/preconfigure
@@ -0,0 +1,54 @@
+case "$machine" in
+riscv*)
+    xlen=`$CC $CFLAGS $CPPFLAGS -E -dM -xc /dev/null | sed -n 's/^#define __riscv_xlen \(.*\)/\1/p'`
+    flen=`$CC $CFLAGS $CPPFLAGS -E -dM -xc /dev/null | sed -n 's/^#define __riscv_flen \(.*\)/\1/p'`
+    float_abi=`$CC $CFLAGS $CPPFLAGS -E -dM -xc /dev/null | sed -n 's/^#define __riscv_float_abi_\([^ ]*\) .*/\1/p'`
+    
+    case "$xlen" in
+    32 | 64)
+    	;;
+    *)
+    	echo "Unable to determine XLEN" >&2
+    	exit 1
+    	;;
+    esac
+    
+    case "$flen" in
+    64)
+    	float_machine=rvd
+    	;;
+    32)
+    	float_machine=rvf
+    	;;
+    "")
+    	float_machine=
+    	;;
+    *)
+    	echo "Unable to determine FLEN" >&2
+    	exit 1
+    	;;
+    esac
+    
+    case "$float_abi" in
+    soft)
+    	abi_flen=0
+    	;;
+    single)
+    	abi_flen=32
+    	;;
+    double)
+    	abi_flen=64
+    	;;
+    *)
+    	echo "Unable to determine floating-point ABI" >&2
+    	exit 1
+    	;;
+    esac
+    
+    base_machine=riscv
+    machine=riscv/rv$xlen/$float_machine
+    
+    $as_echo "#define RISCV_ABI_XLEN $xlen" >>confdefs.h
+    $as_echo "#define RISCV_ABI_FLEN $abi_flen" >>confdefs.h
+    ;;
+esac
diff --git a/sysdeps/riscv/rv32/Implies-after b/sysdeps/riscv/rv32/Implies-after
new file mode 100644
index 000000000000..39a34c5f5743
--- /dev/null
+++ b/sysdeps/riscv/rv32/Implies-after
@@ -0,0 +1 @@
+wordsize-32
diff --git a/sysdeps/riscv/rv32/rvd/Implies b/sysdeps/riscv/rv32/rvd/Implies
new file mode 100644
index 000000000000..9438838e98b9
--- /dev/null
+++ b/sysdeps/riscv/rv32/rvd/Implies
@@ -0,0 +1,2 @@
+riscv/rvd
+riscv/rvf
diff --git a/sysdeps/riscv/rv32/rvf/Implies b/sysdeps/riscv/rv32/rvf/Implies
new file mode 100644
index 000000000000..66c401443b8c
--- /dev/null
+++ b/sysdeps/riscv/rv32/rvf/Implies
@@ -0,0 +1 @@
+riscv/rvf
diff --git a/sysdeps/riscv/rv64/Implies-after b/sysdeps/riscv/rv64/Implies-after
new file mode 100644
index 000000000000..a8cae95f9d46
--- /dev/null
+++ b/sysdeps/riscv/rv64/Implies-after
@@ -0,0 +1 @@
+wordsize-64
diff --git a/sysdeps/riscv/rv64/rvd/Implies b/sysdeps/riscv/rv64/rvd/Implies
new file mode 100644
index 000000000000..42fb132d12ae
--- /dev/null
+++ b/sysdeps/riscv/rv64/rvd/Implies
@@ -0,0 +1,3 @@
+riscv/rv64/rvf
+riscv/rvd
+riscv/rvf
diff --git a/sysdeps/riscv/rv64/rvf/Implies b/sysdeps/riscv/rv64/rvf/Implies
new file mode 100644
index 000000000000..66c401443b8c
--- /dev/null
+++ b/sysdeps/riscv/rv64/rvf/Implies
@@ -0,0 +1 @@
+riscv/rvf
diff --git a/sysdeps/unix/sysv/linux/riscv/Implies b/sysdeps/unix/sysv/linux/riscv/Implies
new file mode 100644
index 000000000000..6faec7011569
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/riscv/Implies
@@ -0,0 +1 @@
+riscv/nptl
diff --git a/sysdeps/unix/sysv/linux/riscv/Makefile b/sysdeps/unix/sysv/linux/riscv/Makefile
new file mode 100644
index 000000000000..0214869e46ab
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/riscv/Makefile
@@ -0,0 +1,100 @@
+ifeq ($(subdir),elf)
+sysdep_routines	+= dl-vdso
+ifeq ($(build-shared),yes)
+# This is needed for DSO loading from static binaries.
+sysdep-dl-routines += dl-static
+endif
+endif
+
+ifeq ($(subdir),misc)
+sysdep_headers += sys/cachectl.h
+sysdep_routines += flush-icache
+endif
+
+ifeq ($(subdir),stdlib)
+gen-as-const-headers += ucontext_i.sym
+endif
+
+abi-variants := ilp32 ilp32f ilp32d lp64 lp64f lp64d
+
+ifeq (,$(filter $(default-abi),$(abi-variants)))
+$(error Unknown ABI $(default-abi), must be one of $(abi-variants))
+endif
+
+abi-ilp32-options     := -D__SIZEOF_INT__=4
+abi-ilp32-condition   := (__SIZEOF_INT__ == 4)
+abi-ilp32-options     += -D__SIZEOF_LONG__=4
+abi-ilp32-condition   += && (__SIZEOF_LONG__ == 4)
+abi-ilp32-options     += -D__SIZEOF_POINTER__=4
+abi-ilp32-condition   += && (__SIZEOF_POINTER__ == 4)
+abi-ilp32-options     += -D__riscv_float_abi_soft
+abi-ilp32-condition   += && (defined __riscv_float_abi_soft)
+abi-ilp32-options     += -U__riscv_float_abi_single
+abi-ilp32-condition   += && (!defined __riscv_float_abi_single)
+abi-ilp32-options     += -U__riscv_float_abi_double
+abi-ilp32-condition   += && (!defined __riscv_float_abi_double)
+
+abi-ilp32f-options    := -D__SIZEOF_INT__=4
+abi-ilp32f-condition  := (__SIZEOF_INT__ == 4)
+abi-ilp32f-options    += -D__SIZEOF_LONG__=4
+abi-ilp32f-condition  += && (__SIZEOF_LONG__ == 4)
+abi-ilp32f-options    += -D__SIZEOF_POINTER__=4
+abi-ilp32f-condition  += && (__SIZEOF_POINTER__ == 4)
+abi-ilp32f-options    += -U__riscv_float_abi_soft
+abi-ilp32f-condition  += && (!defined __riscv_float_abi_soft)
+abi-ilp32f-options    += -D__riscv_float_abi_single
+abi-ilp32f-condition  += && (defined __riscv_float_abi_single)
+abi-ilp32f-options    += -U__riscv_float_abi_double
+abi-ilp32f-condition  += && (!defined __riscv_float_abi_double)
+
+abi-ilp32d-options    := -D__SIZEOF_INT__=4
+abi-ilp32d-condition  := (__SIZEOF_INT__ == 4)
+abi-ilp32d-options    += -D__SIZEOF_LONG__=4
+abi-ilp32d-condition  += && (__SIZEOF_LONG__ == 4)
+abi-ilp32d-options    += -D__SIZEOF_POINTER__=4
+abi-ilp32d-condition  += && (__SIZEOF_POINTER__ == 4)
+abi-ilp32d-options    += -U__riscv_float_abi_soft
+abi-ilp32d-condition  += && (!defined __riscv_float_abi_soft)
+abi-ilp32d-options    += -U__riscv_float_abi_single
+abi-ilp32d-condition  += && (!defined __riscv_float_abi_single)
+abi-ilp32d-options    += -D__riscv_float_abi_double
+abi-ilp32d-condition  += && (defined __riscv_float_abi_double)
+
+abi-lp64-options      := -D__SIZEOF_INT__=4
+abi-lp64-condition    := (__SIZEOF_INT__ == 4)
+abi-lp64-options      += -D__SIZEOF_LONG__=8
+abi-lp64-condition    += && (__SIZEOF_LONG__ == 8)
+abi-lp64-options      += -D__SIZEOF_POINTER__=8
+abi-lp64-condition    += && (__SIZEOF_POINTER__ == 8)
+abi-lp64-options      += -D__riscv_float_abi_soft
+abi-lp64-condition    += && (defined __riscv_float_abi_soft)
+abi-lp64-options      += -U__riscv_float_abi_single
+abi-lp64-condition    += && (!defined __riscv_float_abi_single)
+abi-lp64-options      += -U__riscv_float_abi_double
+abi-lp64-condition    += && (!defined __riscv_float_abi_double)
+
+abi-lp64f-options     := -D__SIZEOF_INT__=4
+abi-lp64f-condition   := (__SIZEOF_INT__ == 4)
+abi-lp64f-options     += -D__SIZEOF_LONG__=8
+abi-lp64f-condition   += && (__SIZEOF_LONG__ == 8)
+abi-lp64f-options     += -D__SIZEOF_POINTER__=8
+abi-lp64f-condition   += && (__SIZEOF_POINTER__ == 8)
+abi-lp64f-options     += -U__riscv_float_abi_soft
+abi-lp64f-condition   += && (!defined __riscv_float_abi_soft)
+abi-lp64f-options     += -D__riscv_float_abi_single
+abi-lp64f-condition   += && (defined __riscv_float_abi_single)
+abi-lp64f-options     += -U__riscv_float_abi_double
+abi-lp64f-condition   += && (!defined __riscv_float_abi_double)
+
+abi-lp64d-options     := -D__SIZEOF_INT__=4
+abi-lp64d-condition   := (__SIZEOF_INT__ == 4)
+abi-lp64d-options     += -D__SIZEOF_LONG__=8
+abi-lp64d-condition   += && (__SIZEOF_LONG__ == 8)
+abi-lp64d-options     += -D__SIZEOF_POINTER__=8
+abi-lp64d-condition   += && (__SIZEOF_POINTER__ == 8)
+abi-lp64d-options     += -U__riscv_float_abi_soft
+abi-lp64d-condition   += && (!defined __riscv_float_abi_soft)
+abi-lp64d-options     += -U__riscv_float_abi_single
+abi-lp64d-condition   += && (!defined __riscv_float_abi_single)
+abi-lp64d-options     += -D__riscv_float_abi_double
+abi-lp64d-condition   += && (defined __riscv_float_abi_double)
diff --git a/sysdeps/unix/sysv/linux/riscv/Versions b/sysdeps/unix/sysv/linux/riscv/Versions
new file mode 100644
index 000000000000..f61c7e31a0ae
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/riscv/Versions
@@ -0,0 +1,5 @@
+libc {
+  GLIBC_2.27 {
+    __riscv_flush_icache;
+  }
+}
diff --git a/sysdeps/unix/sysv/linux/riscv/configure b/sysdeps/unix/sysv/linux/riscv/configure
new file mode 100755
index 000000000000..4dd085a7b0b6
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/riscv/configure
@@ -0,0 +1,210 @@
+# This file is generated from configure.ac by Autoconf.  DO NOT EDIT!
+ # Local configure fragment for sysdeps/unix/sysv/linux/riscv.
+
+arch_minimum_kernel=4.15.0
+
+libc_cv_riscv_int_abi=no
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for grep that handles long lines and -e" >&5
+$as_echo_n "checking for grep that handles long lines and -e... " >&6; }
+if ${ac_cv_path_GREP+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -z "$GREP"; then
+  ac_path_GREP_found=false
+  # Loop through the user's path and test for each of PROGNAME-LIST
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH$PATH_SEPARATOR/usr/xpg4/bin
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_prog in grep ggrep; do
+    for ac_exec_ext in '' $ac_executable_extensions; do
+      ac_path_GREP="$as_dir/$ac_prog$ac_exec_ext"
+      as_fn_executable_p "$ac_path_GREP" || continue
+# Check for GNU ac_path_GREP and select it if it is found.
+  # Check for GNU $ac_path_GREP
+case `"$ac_path_GREP" --version 2>&1` in
+*GNU*)
+  ac_cv_path_GREP="$ac_path_GREP" ac_path_GREP_found=:;;
+*)
+  ac_count=0
+  $as_echo_n 0123456789 >"conftest.in"
+  while :
+  do
+    cat "conftest.in" "conftest.in" >"conftest.tmp"
+    mv "conftest.tmp" "conftest.in"
+    cp "conftest.in" "conftest.nl"
+    $as_echo 'GREP' >> "conftest.nl"
+    "$ac_path_GREP" -e 'GREP$' -e '-(cannot match)-' < "conftest.nl" >"conftest.out" 2>/dev/null || break
+    diff "conftest.out" "conftest.nl" >/dev/null 2>&1 || break
+    as_fn_arith $ac_count + 1 && ac_count=$as_val
+    if test $ac_count -gt ${ac_path_GREP_max-0}; then
+      # Best one so far, save it but keep looking for a better one
+      ac_cv_path_GREP="$ac_path_GREP"
+      ac_path_GREP_max=$ac_count
+    fi
+    # 10*(2^10) chars as input seems more than enough
+    test $ac_count -gt 10 && break
+  done
+  rm -f conftest.in conftest.tmp conftest.nl conftest.out;;
+esac
+
+      $ac_path_GREP_found && break 3
+    done
+  done
+  done
+IFS=$as_save_IFS
+  if test -z "$ac_cv_path_GREP"; then
+    as_fn_error $? "no acceptable grep could be found in $PATH$PATH_SEPARATOR/usr/xpg4/bin" "$LINENO" 5
+  fi
+else
+  ac_cv_path_GREP=$GREP
+fi
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_path_GREP" >&5
+$as_echo "$ac_cv_path_GREP" >&6; }
+ GREP="$ac_cv_path_GREP"
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for egrep" >&5
+$as_echo_n "checking for egrep... " >&6; }
+if ${ac_cv_path_EGREP+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if echo a | $GREP -E '(a|b)' >/dev/null 2>&1
+   then ac_cv_path_EGREP="$GREP -E"
+   else
+     if test -z "$EGREP"; then
+  ac_path_EGREP_found=false
+  # Loop through the user's path and test for each of PROGNAME-LIST
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH$PATH_SEPARATOR/usr/xpg4/bin
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_prog in egrep; do
+    for ac_exec_ext in '' $ac_executable_extensions; do
+      ac_path_EGREP="$as_dir/$ac_prog$ac_exec_ext"
+      as_fn_executable_p "$ac_path_EGREP" || continue
+# Check for GNU ac_path_EGREP and select it if it is found.
+  # Check for GNU $ac_path_EGREP
+case `"$ac_path_EGREP" --version 2>&1` in
+*GNU*)
+  ac_cv_path_EGREP="$ac_path_EGREP" ac_path_EGREP_found=:;;
+*)
+  ac_count=0
+  $as_echo_n 0123456789 >"conftest.in"
+  while :
+  do
+    cat "conftest.in" "conftest.in" >"conftest.tmp"
+    mv "conftest.tmp" "conftest.in"
+    cp "conftest.in" "conftest.nl"
+    $as_echo 'EGREP' >> "conftest.nl"
+    "$ac_path_EGREP" 'EGREP$' < "conftest.nl" >"conftest.out" 2>/dev/null || break
+    diff "conftest.out" "conftest.nl" >/dev/null 2>&1 || break
+    as_fn_arith $ac_count + 1 && ac_count=$as_val
+    if test $ac_count -gt ${ac_path_EGREP_max-0}; then
+      # Best one so far, save it but keep looking for a better one
+      ac_cv_path_EGREP="$ac_path_EGREP"
+      ac_path_EGREP_max=$ac_count
+    fi
+    # 10*(2^10) chars as input seems more than enough
+    test $ac_count -gt 10 && break
+  done
+  rm -f conftest.in conftest.tmp conftest.nl conftest.out;;
+esac
+
+      $ac_path_EGREP_found && break 3
+    done
+  done
+  done
+IFS=$as_save_IFS
+  if test -z "$ac_cv_path_EGREP"; then
+    as_fn_error $? "no acceptable egrep could be found in $PATH$PATH_SEPARATOR/usr/xpg4/bin" "$LINENO" 5
+  fi
+else
+  ac_cv_path_EGREP=$EGREP
+fi
+
+   fi
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_path_EGREP" >&5
+$as_echo "$ac_cv_path_EGREP" >&6; }
+ EGREP="$ac_cv_path_EGREP"
+
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+__SIZEOF_INT__ __SIZEOF_LONG__ __SIZEOF_POINTER__
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "4 8 8" >/dev/null 2>&1; then :
+  libc_cv_riscv_int_abi=lp64
+fi
+rm -f conftest*
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+__SIZEOF_INT__ __SIZEOF_LONG__ __SIZEOF_POINTER__
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "4 4 4" >/dev/null 2>&1; then :
+  libc_cv_riscv_int_abi=ilp32
+fi
+rm -f conftest*
+
+if test $libc_cv_riscv_int_abi = no; then
+  as_fn_error $? "Unable to determine integer ABI" "$LINENO" 5
+fi
+
+libc_cv_riscv_float_abi=no
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#ifdef __riscv_float_abi_double
+		   yes
+		   #endif
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "yes" >/dev/null 2>&1; then :
+  libc_cv_riscv_float_abi=d
+fi
+rm -f conftest*
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#ifdef __riscv_float_abi_single
+		   yes
+		   #endif
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "yes" >/dev/null 2>&1; then :
+  libc_cv_riscv_float_abi=f
+fi
+rm -f conftest*
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#ifdef __riscv_float_abi_soft
+		   yes
+		   #endif
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "yes" >/dev/null 2>&1; then :
+  libc_cv_riscv_float_abi=
+fi
+rm -f conftest*
+
+if test $libc_cv_riscv_float_abi = no; then
+  as_fn_error $? "Unable to determine floating-point ABI" "$LINENO" 5
+fi
+
+config_vars="$config_vars
+default-abi = $libc_cv_riscv_int_abi$libc_cv_riscv_float_abi"
diff --git a/sysdeps/unix/sysv/linux/riscv/configure.ac b/sysdeps/unix/sysv/linux/riscv/configure.ac
new file mode 100644
index 000000000000..b9a6207d48d6
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/riscv/configure.ac
@@ -0,0 +1,33 @@
+sinclude(./aclocal.m4)dnl Autoconf lossage
+GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
+# Local configure fragment for sysdeps/unix/sysv/linux/riscv.
+
+arch_minimum_kernel=4.15.0
+
+libc_cv_riscv_int_abi=no
+AC_EGREP_CPP(4 8 8, [__SIZEOF_INT__ __SIZEOF_LONG__ __SIZEOF_POINTER__
+  ], libc_cv_riscv_int_abi=lp64)
+AC_EGREP_CPP(4 4 4, [__SIZEOF_INT__ __SIZEOF_LONG__ __SIZEOF_POINTER__
+  ], libc_cv_riscv_int_abi=ilp32)
+if test $libc_cv_riscv_int_abi = no; then
+  AC_MSG_ERROR([Unable to determine integer ABI])
+fi
+
+libc_cv_riscv_float_abi=no
+AC_EGREP_CPP(yes, [#ifdef __riscv_float_abi_double
+		   yes
+		   #endif
+  ],libc_cv_riscv_float_abi=d)
+AC_EGREP_CPP(yes, [#ifdef __riscv_float_abi_single
+		   yes
+		   #endif
+  ],libc_cv_riscv_float_abi=f)
+AC_EGREP_CPP(yes, [#ifdef __riscv_float_abi_soft
+		   yes
+		   #endif
+  ],libc_cv_riscv_float_abi=)
+if test $libc_cv_riscv_float_abi = no; then
+  AC_MSG_ERROR([Unable to determine floating-point ABI])
+fi
+
+LIBC_CONFIG_VAR([default-abi], [$libc_cv_riscv_int_abi$libc_cv_riscv_float_abi])
diff --git a/sysdeps/unix/sysv/linux/riscv/rv32/Implies b/sysdeps/unix/sysv/linux/riscv/rv32/Implies
new file mode 100644
index 000000000000..8b7deb33cd51
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/riscv/rv32/Implies
@@ -0,0 +1,3 @@
+unix/sysv/linux/riscv
+unix/sysv/linux/generic/wordsize-32
+unix/sysv/linux/generic
diff --git a/sysdeps/unix/sysv/linux/riscv/rv64/Implies b/sysdeps/unix/sysv/linux/riscv/rv64/Implies
new file mode 100644
index 000000000000..f042343bf7b4
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/riscv/rv64/Implies
@@ -0,0 +1,3 @@
+unix/sysv/linux/riscv
+unix/sysv/linux/generic
+unix/sysv/linux/wordsize-64
diff --git a/sysdeps/unix/sysv/linux/riscv/rv64/Makefile b/sysdeps/unix/sysv/linux/riscv/rv64/Makefile
new file mode 100644
index 000000000000..cb60d740476d
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/riscv/rv64/Makefile
@@ -0,0 +1,4 @@
+ifeq ($(subdir),socket)
+CFLAGS-recv.c += -fexceptions
+CFLAGS-send.c += -fexceptions
+endif
diff --git a/sysdeps/unix/sysv/linux/riscv/shlib-versions b/sysdeps/unix/sysv/linux/riscv/shlib-versions
new file mode 100644
index 000000000000..fe7322d23a94
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/riscv/shlib-versions
@@ -0,0 +1,17 @@
+DEFAULT		GLIBC_2.27
+
+%if RISCV_ABI_XLEN == 64 && RISCV_ABI_FLEN == 64
+ld=ld-linux-riscv64-lp64d.so.1
+%elif RISCV_ABI_XLEN == 64 && RISCV_ABI_FLEN == 32
+ld=ld-linux-riscv64-lp64f.so.1
+%elif RISCV_ABI_XLEN == 64 && RISCV_ABI_FLEN == 0
+ld=ld-linux-riscv64-lp64.so.1
+%elif RISCV_ABI_XLEN == 32 && RISCV_ABI_FLEN == 64
+ld=ld-linux-riscv32-ilp32d.so.1
+%elif RISCV_ABI_XLEN == 32 && RISCV_ABI_FLEN == 32
+ld=ld-linux-riscv32-ilp32f.so.1
+%elif RISCV_ABI_XLEN == 32 && RISCV_ABI_FLEN == 0
+ld=ld-linux-riscv32-ilp32.so.1
+%else
+%error cannot determine ABI
+%endif
-- 
2.13.6