Acid debugging basics

How to step through a program and inspect data structures

To help acid print data structures, compile with the -a or -aa options:

   8c -FTVwaa hubfs.c >$home/hubfs.acid

After a hubfs is started, attach acid to it:

   acid -l $home/hubfs.acid hubfspid

Check the current status of the execution stack and variables:

   lstk()

Set a breakpoint:

   bpset(fswrite)

Acid says “waiting”. Cause a write to the fs in the system outside of acid, then in acid:

   cont()

Now we have hit the breakpoint, check stack and step through a few lines of source:

   lstk()
   next()
   next()
   next()

Check the current stack and variables again, note that h has been set:

   lstk()

Use the address shown of h to print the data of the current Hub:

   Hub(0xe1ce0)

Delete the breakpoint

   bpdel(fswrite)

Allow the program to continue freely:

   cont()

Hit delete key to interrupt waiting, ctrl-D to exit acid.