Fresh Fish 5/FreshFish_July-August1994.bin/bbs/dev/mungwall-37.64.lha/MungWall-37.64/MungWall.doc

Text File | 1993-03-02 | 10.3 KB | 231 lines

25-Feb-93 Mungwall 37.64 doc.

Mungwall munges memory and watches for illegal FreeMem's.
Mungwall is especially useful in combination with Enforcer.
Output is either serial or parallel (mungwall.par), or local by
using both mungwall and a local serial debug capture tool such
as Sushi.

Revisions
=========

Since 37.49 MungWall, NAMETAG option tags each allocation with the name
of the allocator.  The new "MUNGLIST" program examines used memory areas
for mungwall tag info, and outputs a list of who owns the various
pieces of allocated memory, their sizes, etc.  If you have used the
NAMETAG option of MungWall, this list will include the name of the
task or command that allocated the memory.  Note that certain
allocations belonging to your program may be displayed as belonging
to another task (such as the task of a disk device that you
locked a file on or accessed).

Mungwall 37.51 adds an AvailMem wedge which reduces reported available
memory by the size which Mungwall will add to any allocation.  It also
correct a problem which had caused the NAMETAG option to crash on a
68000.

Mungwall 37.52 fixes Enforcer hits in task name comparisons and adds
better A6 handling when calling the real memory functions.

Mungwall 37.53 should finally fix mungwall crashes on 68000 when
using taskname-related options.

Mungwall 37.54 - some fixes to output during initialization

Mungwall 37.55 - fixes a bug in Mungwall where last chunk of memory
   could be lost, and fixes a similar bug in munglist which could occur
   if munglist's buffer filled.  Also added munglist bufsize argument.

Mungwall 37.57 - stops null terminating cli_CommandName in place which
   makes mungwall name options again compatible with DMAKE and ARexx
   scripts with 1-character names.  Adds new SHOWFAIL option which
   tells Mungwall to report all failed allocations.  Changes the output
   text "(at 0xhhhhhhh)" to "(task 0xhhhhhhh)" to be easier to understand.

Mungwall 37.58 - adds matching NO and UPDATE options for SHOWSTACK,
   NAMETAG, and SHOWFAIL.

Mungwall 37.60 - adds SHOWPC dump of memory at A: and C: caller addresses
   and a matching NOSHOWPC option.  Does not show a supposed PC address
   if it is not RAM according to TypeOfMem().  This is to help prevent
   enforcer hits or worse, possible reads (or read-triggered writes)
   to hardware registers.

Mungwall 37.61 and Munglist 37.4 - Add the important capability for
   Mungwall to distinguish between old mungwall cookies left over in
   memory after rebooting, and new ones.  The mungwall info area on
   each allocation has been enlarged by 8 bytes and now contains a
   second per-session cookie which is based on the datestamp
   when mungwall is first started.   Munglist has been enhanced
   to show the addresses applications received when they allocated
   memory, not the address of the larger piece mungwall allocated.
   Some changes to output format.

Mungwall 37.62 implements a new default rolling fill character for
   the walls surrounding memory allocations.  Each allocation gets
   a new fill character between $81 and $FF.  This allows Mungwall to
   generally catch errors where too much memory has been copied
   from one allocation to another.  Note that the explicit FILLCHAR
   option of Mungwall now disables the rolling fillchar feature.
   Do not use the FILLCHAR option if you want the protection of the
   rolling fill char.  Some changes to output format.

Mungwall 37.63 adds SHOWHUNK and NOSHOWHUNK options.  With SHOWHUNK,
   mungwall will attempt to show the hunk and offset for the probable
   C or Asm PC addresses of the caller generating the hit if the PC
   address is in RAM and also within the seglist of the caller's process.

Mungwall 37.64 adds SegTracker support.  If SHOWHUNK is option is on,
   if SegTracker is installed, mungwall will get hunk/offset info
   from SegTracker, else mungwall can only check if the probable
   PC addresses are in the calling process's own SegList.


What Mungwall Does
==================

Memory munging:

 - Except when Enforcer is running, location 0 is set to $C0DEDBAD, i.e.
   programs referencing location zero will not f.e. find a null string.

 - On startup all free memory is munged with $ABADCAFE. If this number
   shows up, someone is referencing memory in the free list.

 - Except when MEMF_CLEAR is set, memory is pre-munged on allocation with
   $DEADFOOD. When this is used in an Enforcer report, the caller is
   allocating memory and doesn't initialize it before using it. Note that
   only memory which has a cookie attached will be pre-munged.

 - Memory is filled with $DEADBEEF before it is freed, encouraging
   programs reusing free'ed memory to crash.

Memory watching:

Mungwall places a magic cookie before the memory allocation.
Along with a wall of bytes on either side of the allocation to keep an
eye on the memory just before or after the allocation. If the
memory wall is trashed, mungwall complains and shows the damaged area.
If memory is trashed so bad that the cookie is completely gone, Mungwall
will not consider it a walled memory allocation and lets it go. Changes
are you'll be corrupting the memory list and/or overwriting other memory
allocation and crash soon after that. If a mungwall hit occurs, memory
will not be munged or free'ed, to give you a change to look at what was
written there.

Both null pointer FreeMem()'s and null sized Alloc/FreeMem()'s trigger
mungwall. Mungwall also gets upset when a memoryblock is free'ed with a
size different from the one used for allocating the memoryblock, and will
say so. The integrity of the walls will be tested according to the size
specified on allocation time, but will not be free'ed.

Pointers passed to FreeMem() will be rejected if they are non-longword
alligned. Thus possible catching bogus pointers otherwise left untouched
by mungwall.

Unless a specific task(s) is watched and that task leaves before mungwall
does, mungwall will always lose some memory.

NOTES:

Other debugging tools which SetFunction() AllocMem() and/or
FreeMem() and JSR to what they think is the old memory routine,
should be run BEFORE mungwall. Mungwall needs to know the returnaddress
of the initial caller. Running other debugging tools after mungwall
will result in false reports about layers.library and invalid
mungwall reports about the caller. The 'scratcher' for example must
be run before mungwall, 'memoration' can be run afterwards, since it
JMP's.

When mungwall is being stopped, the walls around the original allocations
which are not free'ed at that point, will never get free'ed, only the block
within. Thus causing memory fragmentation and memory loss.
In addition, stopping and restarting mungwall can cause numerous
bogus mungwall hits if applications allocate uncleared memory
(containing unlceared mungwall cookies) while mungwall is off and then
free it when mungwall is back on.


Memory allocations larger than 3 gigabytes will not be marked by mungwall.



MUNGWALL [UPDATE] [[TASK name][WAIT]] [SNOOP] [NOSNOOP] [NOWAIT] [INFO]
         [SHOWSTACK] [NOSHOWSTACK] [NAMETAG] [NONAMETAG] [SHOWPC][NOSHOWPC]
     [SHOWFAIL] [NOSHOWFAIL] [PRESIZE n] [POSTSIZE n] [FILLCHAR 0xXX]
     [SHOWHUNK] [NOSHOWHUNK]

TASK name   - Watch only the task(s), or all but the task(s) specified
              with 'name'. Multiple tasknames are indicated by placing
              a '|' between the names. If the names are preceeded by an
              exclamation mark, all tasks except the ones indicated are
              tracked. ALL is a reserved name, indicating all tasks
              should be tracked. Default ALL.

PRESIZE     - Size of wall before memory allocation in bytes. Minimum 4,
              maximum 64. Default 32.

POSTSIZE    - Size of wall after memory allocation in bytes. Minimum 4,
              maximum 64. The actual number of bytes after the allocation
              may vary slightly, since it's upped to the nearest longword.
              Default 32.

FILLCHAR n  - Character to build the memory wall with. Can be indicated
              both hexadecimal and decimal. Default is a rolling fillchar
          which uses a new odd number between $81 and $FF for each
          new allocation.  This makes it possible for Mungwall to
          usually catch errors where too much memory is copied
          from one allocation to another.  Specifying a FILLCHAR
          disables the default rolling fillchar feature.

SNOOP       - Produce snoop compatible output. No snoop output is given
              for illegal FreeMem's. Default OFF. Layers AllocMem's and
              FreeMem's are never snooped. SNOOP is particulary useful
              in combination with TASK. Snoop output can be filtered
              with 'snoopstrip' to find the origin of memory loss.

WAIT        - Halt task causing a hit and wait for Ctrl-C. Make sure you
            - can issue a break to the task. WAIT can be used without
              specifying a specific taskname to watch. Default OFF.

INFO        - Show configuration information.

SHOWSTACK   - Show 32 longwords of the stack whenever a hit/snoop occurs

NAMETAG     - Tag each allocation with allocating task or command's name

SHOWFAIL    - Tells mungwall to report all memory allocation failures

SHOWPC        - Show a dump of memory at the A: and C: possible PC
          (program counter) addresses (one should be correct)
              Does not show a supposed PC address if it is not RAM
              according to TypeOfMem().  This is to help prevent enforcer
              hits or worse, possible reads (or read-triggered writes)
              to hardware registers.

SHOWHUNK    - On a hit or snoop, if the probable PC address of a reported
          call to AllocMem or FreeMem is within the calling process's
          seglist, attempt to show hunk and offset information.

UPDATE      - Indicates an already running mungwall task should be up-
              dated with new parameters. Presize, postsize and fillchar
              can never be updated.  NOTE - when doing an UPDATE, the
          UPDATE option must be the first command line arg

The following are extra updating parameters.

NOSNOOP     - Turn snooping off.

NOWAIT      - No longer halt a task in case of an error.

NONAMETAG   - Turn off taskname storage

NOSHOWSTACK - Turn off showstack option

NOSHOWFAIL  - Turn off option that displays memory allocation failures

NOSHOWPC    - Turn off option that displays dump of memory at caller PC

NOSHOWHUNK  - Turn off options that displays hunk and offset information