make access denied problem

HI
I am using ns2 from last few moth i was working fine now few day to ago its
showing error when trying to run make command. all solution are well come
the error msg is as follow

barjinder@barjinder-HP-ProBook-4420s:~$ cd ns-allinone-2.35
barjinder@barjinder-HP-ProBook-4420s:~/ns-allinone-2.35$ cd ns-2.35
barjinder@barjinder-HP-ProBook-4420s:~/ns-allinone-2.35/ns-2.35$
 ./configure
./configure: line 2097: config.log: Permission denied
./configure: line 2107: config.log: Permission denied
barjinder@barjinder-HP-ProBook-4420s:~/ns-allinone-2.35/ns-2.35$ ./configure
./configure: line 2097: config.log: Permission denied
./configure: line 2107: config.log: Permission denied
barjinder@barjinder-HP-ProBook-4420s:~/ns-allinone-2.35/ns-2.35$ make
/home/barjinder/ns-allinone-2.35/bin/tclsh8.5 bin/tcl-expand.tcl
tcl/lib/ns-lib.tcl tcl/lib/ns-diffusion.tcl tcl/delaybox/delaybox.tcl
tcl/packmime/packmime.tcl tcl/tmix/tmix.tcl tcl/tmix/tmix_delaybox.tcl |
../tclcl-1.20/tcl2c++ et_ns_lib > gen/ns_tcl.cc
/bin/sh: 1: cannot create gen/ns_tcl.cc: Permission denied
error writing "stdout": broken pipe
    while executing
"puts "### tcl-expand.tcl: begin expanding $name""
    (procedure "expand_file" line 2)
    invoked from within
"expand_file [file tail $name]"
    ("foreach" body line 5)
    invoked from within
"foreach name $argv {
set dirname [file dirname $name]
if {$dirname != "."} {
cd $dirname
expand_file [file tail $name]
cd $startupDir
} else ..."
    (file "bin/tcl-expand.tcl" line 65)
make: *** [gen/ns_tcl.cc] Error 2



-- 
barjinder