configs/boot/hack_back_ckpt.rcS

   1 #!/bin/sh
   2
   3 #
   4 # This is a tricky script to understand. When run in M5, it creates
   5 # a checkpoint after Linux boot up, but before any benchmarks have
   6 # been run. By playing around with environment variables, we can
   7 # detect whether the checkpoint has been taken.
   8 #  - If the checkpoint hasn't been taken, the script allows M5 to checkpoint the system,
   9 # re-read this script into a new tmp file, and re-run it. On the
  10 # second execution of this script (checkpoint has been taken), the
  11 # environment variable is already set, so the script will exit the
  12 # simulation
  13 #  - When we restore the simulation from a checkpoint, we can
  14 # specify a new script for M5 to execute in the full-system simulation,
  15 # and it will be executed as if a checkpoint had just been taken.
  16 #
  17 # Author:
  18 #   Joel Hestness, hestness@cs.utexas.edu
  19 #   while at AMD Research and Advanced Development Lab
  20 # Date:
  21 #   10/5/2010
  22 #
  23
  24 # Test if the RUNSCRIPT_VAR environment variable is already set
  25 if [ "${RUNSCRIPT_VAR+set}" != set ]
  26 then
  27         # Signal our future self that it's safe to continue
  28         export RUNSCRIPT_VAR=1
  29 else
  30         # We've already executed once, so we should exit
  31         /sbin/m5 exit
  32 fi
  33
  34 # Checkpoint the first execution
  35 echo "Checkpointing simulation..."
  36 /sbin/m5 checkpoint
  37
  38 # Test if we previously okayed ourselves to run this script
  39 if [ "$RUNSCRIPT_VAR" -eq 1 ]
  40 then
  41
  42         # Signal our future self not to recurse infinitely
  43         export RUNSCRIPT_VAR=2
  44
  45         # Read the script for the checkpoint restored execution
  46         echo "Loading new script..."
  47         /sbin/m5 readfile > /tmp/runscript
  48         chmod 755 /tmp/runscript
  49
  50         # Execute the new runscript
  51         if [ -s /tmp/runscript ]
  52         then
  53                 exec /tmp/runscript
  54         else
  55                 echo "Script not specified. Dropping into shell..."
  56                 /bin/bash
  57         fi
  58
  59 fi
  60
  61 echo "Fell through script. Exiting..."
  62 /sbin/m5 exit