Favorite Comments and Constants in OpenSolaris Source

While perusing the code for OpenSolaris, my fellow interns and I have come across some great comments, variable names, and documentation, as any large code base must inevitably have:

• usr/src/uts/common/os/clock.c: "If the TOD chip isn't giving correct time, then set it to the time that was passed in as a rough estimate. If we don't have an estimate, then set the clock back to a time when Oliver North, ALF and Dire Straits were all on the collective brain: 1987." (Found by Dan)
• usr/src/uts/i86pc/os/machdep.c: "This routine is almost correct now, but not quite." (also from Dan)
• usr/src/uts/common/os/condvar.c: Regarding cv_wait_stop(), "This is a horrible kludge. It is evil. It is vile. It is swill. If your code has to call this function then your code is the same."
• usr/src/uts/common/sys/dumphdr.h: The magic number at the start of all core dumps:
  

  #define	DUMP_MAGIC	0xdefec8edU		/* dump magic number */

• usr/src/lib/watchmalloc/common/malloc.c: While poking around in mdb, I printed the words at the end of an array and found 0xbaddcabb and 0xfeedface. So I opened the OS source browser, searched, and found:

  /*
   * Patterns to be copied into freed blocks and allocated blocks.
   * 0xfeedbeef and 0xfeedface are invalid pointer values in all programs.
   */
  static	uint64_t	patterns[2] = {
  	0xdeadbeefdeadbeefULL,	/* pattern in a freed block */
  	0xbaddcafebaddcafeULL	/* pattern in an allocated block */
  };
  

• Earlier today I found out that the Solaris libc defines a struct uberdata. It ends up being used on the sly in the psig command.
• For a good time, follow int bsd_evil_hack through the grub source.

Posted by csg [Personal] ( August 01, 2007 02:58 PM ) Permalink | Comments[1]