RISC-V: Add nanosleep functionality

libgloss/riscv/Makefile.in

@@ -7,6 +7,7 @@ gloss_hdrs = \
 
 gloss_srcs = \
 	syscalls.c \
+	nanosleep.c
 
 # Extra files
 

libgloss/riscv/nanosleep.c

@@ -0,0 +1,12 @@
+#include <machine/syscall.h>
+#include <sys/time.h>
+
+int
+nanosleep(const struct timespec *rqtp, struct timespec *rmtp)
+{
+  unsigned long current_time, end_time;
+  asm ("rdtime %0" : "+r" (current_time));
+  end_time = current_time + rqtp->tv_sec * 1000000000ULL + rqtp->tv_nsec;
+  while (current_time <= end_time) asm ("rdtime %0" : "+r" (current_time));
+  return 0;
+}

newlib/configure.host

@@ -258,7 +258,7 @@ case "${host_cpu}" in
   riscv*)
 	libm_machine_dir=riscv
 	machine_dir=riscv
-	newlib_cflags="${newlib_cflags}"
+	newlib_cflags="${newlib_cflags} -DHAVE_NANOSLEEP"
 	default_newlib_atexit_dynamic_alloc="no"
 	;;
   rl78)