re PR go/52586 (libgo fails to build for mips*64-linux-gnu (reference to…

re PR go/52586 (libgo fails to build for mips*64-linux-gnu (reference to undefined name 'SYS_GETDENTS64'))

	PR go/52586
mksysinfo, syscall: Make sure SYS_GETDENTS64 is defined.

Fixes build on MIPS GNU/Linux.

From-SVN: r186986

libgo/go/syscall/libcall_linux.go

@@ -203,7 +203,11 @@ func Getdents(fd int, buf []byte) (n int, err error) {
 		p = (*byte)(unsafe.Pointer(&_zero))
 	}
 	Entersyscall()
-	r1, _, errno := Syscall(SYS_GETDENTS64, uintptr(fd), uintptr(unsafe.Pointer(p)), uintptr(len(buf)))
+	s := SYS_GETDENTS64
+	if s == 0 {
+		s = SYS_GETDENTS
+	}
+	r1, _, errno := Syscall(uintptr(s), uintptr(fd), uintptr(unsafe.Pointer(p)), uintptr(len(buf)))
 	n = int(r1)
 	if n < 0 {
 		err = errno

libgo/mksysinfo.sh

@@ -224,6 +224,14 @@ grep '^const _SYS_' gen-sysinfo.go | \
     echo "const $sup = _$sys" >> ${OUT}
   done
 
+# The GNU/Linux support wants to use SYS_GETDENTS64 if available.
+if ! grep '^const SYS_GETDENTS ' ${OUT} >/dev/null 2>&1; then
+  echo "const SYS_GETDENTS = 0" >> ${OUT}
+fi
+if ! grep '^const SYS_GETDENTS64 ' ${OUT} >/dev/null 2>&1; then
+  echo "const SYS_GETDENTS64 = 0" >> ${OUT}
+fi
+
 # Stat constants.
 grep '^const _S_' gen-sysinfo.go | \
   sed -e 's/^\(const \)_\(S_[^= ]*\)\(.*\)$/\1\2 = _\2/' >> ${OUT}