GDB script to spoof the nginx config file for a runtime reload with SIGHUP

filespoof_memfd.gdb

set $conf = "server {\n\tlisten 8082 default_server;\n\tlisten [::]:8082 default_server;\n\troot /var/www/html;\n\tserver_name _;\n\tlocation / {\n\t\ttry_files $uri $uri/ =404;\n\t}\n}"
set $conf_len = $_strlen($conf)
set detach-on-fork off
break open
condition 1 $_streq((char *)$rdi, "/etc/nginx/sites-enabled/default")

# signal break
c
c
# open break
# preserve regs

set $old_rdi = $rdi

printf "nginxject: rdi: %s\n", (char *)$rdi

set $addr = (char *) malloc($conf_len)
call strcpy($addr, $conf)

set $mfd = (long long) memfd_create("newconf", 0)
printf "nginxject: memfd: %d\n", $mfd
call write($mfd, $conf, $conf_len)
printf "nginxject: rewinding..."
call lseek($mfd, 0, 0)
printf "nginxject: returning..."
set $rdi = $old_rdi

return (long long) $mfd

detach
q