cvs commit: src/sys/conf files src/sys/ddb db_capture.c db_command.c db_textdump.c ddb.h src/sys/kern kern_shutdown.c

[Robert Watson]

rwatson     2007-12-26 11:32:33 UTC

  FreeBSD src repository

  Modified files:
    sys/conf             files 
    sys/ddb              db_capture.c db_command.c ddb.h 
    sys/kern             kern_shutdown.c 
  Added files:
    sys/ddb              db_textdump.c 
  Log:
  Add textdump(4) facility, which provides an alternative form of kernel
  dump using mechanically generated/extracted debugging output rather than
  a simple memory dump.  Current sources of debugging output are:
  
  - DDB output capture buffer, if there is captured output to save
  - Kernel message buffer
  - Kernel configuration, if included in kernel
  - Kernel version string
  - Panic message
  
  Textdumps are stored in swap/dump partitions as with regular dumps, but
  are laid out as ustar files in order to allow multiple parts to be stored
  as a stream of sequentially written blocks.  Blocks are written out in
  reverse order, as the size of a textdump isn't known a priori.  As with
  regular dumps, they will be extracted using savecore(8).
  
  One new DDB(4) command is added, "textdump", which accepts "set",
  "unset", and "status" arguments.  By default, normal kernel dumps are
  generated unless "textdump set" is run in order to schedule a textdump.
  It can be canceled using "textdump unset" to restore generation of a
  normal kernel dump.
  
  Several sysctls exist to configure aspects of textdumps;
  debug.ddb.textdump.pending can be set to check whether a textdump is
  pending, or set/unset in order to control whether the next kernel dump
  will be a textdump from userspace.
  
  While textdumps don't have to be generated as a result of a DDB script
  run automatically as part of a kernel panic, this is a particular useful
  way to use them, as instead of generating a complete memory dump, a
  simple transcript of an automated DDB session can be captured using the
  DDB output capture and textdump facilities.  This can be used to
  generate quite brief kernel bug reports rich in debugging information
  but not dependent on kernel symbol tables or precisely synchronized
  source code.  Most textdumps I generate are less than 100k including
  the full message buffer.  Using textdumps with an interactive debugging
  session is also useful, with capture being enabled/disabled in order to
  record some but not all of the DDB session.
  
  MFC after:      3 months
  
  Revision  Changes    Path
  1.1260    +1 -0      src/sys/conf/files
  1.2       +55 -3     src/sys/ddb/db_capture.c
  1.76      +1 -0      src/sys/ddb/db_command.c
  1.1       +555 -0    src/sys/ddb/db_textdump.c (new)
  1.46      +23 -0     src/sys/ddb/ddb.h
  1.187     +9 -1      src/sys/kern/kern_shutdown.c