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 at
Mon Mar 31 14:57:30 PDT 2008

rwatson     2008-03-31 21:57:24 UTC

  FreeBSD src repository

  Modified files:        (Branch: RELENG_7)
    sys/conf             files 
    sys/ddb              db_capture.c db_command.c ddb.h 
    sys/kern             kern_shutdown.c 
  Added files:           (Branch: RELENG_7)
    sys/ddb              db_textdump.c 
  Merge files:1.1260, db_capture.c:1.2, db_command.c:1.76,
  db_textdump.c:1.1, ddb.h:1.46, kern_shutdown.c:1.187 from HEAD to
    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.
  Revision     Changes    Path
  1.1243.2.10  +1 -0      src/sys/conf/files      +55 -3     src/sys/ddb/db_capture.c     +1 -0      src/sys/ddb/db_command.c      +555 -0    src/sys/ddb/db_textdump.c (new)     +23 -0     src/sys/ddb/ddb.h    +9 -1      src/sys/kern/kern_shutdown.c

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