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Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
Use is subject to license terms.

Copyright 2022 Garrett D'Amore


1. Introduction

This directory contains source code for sample debugger modules for the Modular
Debugger (MDB).  These modules demonstrate how developers can use the MDB
programming API to extend the capabilities of MDB itself.  MDB is an extensible
utility for low-level debugging and editing of the live operating system,
operating system crash dumps, user processes, user process core dumps, and
object files.  For a more detailed description of MDB features and documentation
for the MDB programming API, refer to the manual, "Solaris Modular Debugger
Guide".  This document is available on-line at http://docs.sun.com.

2. Configuration

As the files in this directory are owned by the administrator, you should make
a copy of this directory to your home directory or other location before you
begin experimenting with MDB.  If you wish to change the configuration, edit
the CC macro definitions in Makefile.i386 and Makefile.amd64 to point to the
appropriate pathnames.

The Makefiles contained in this directory are set up to use the C compiler (cc)
found in your $PATH.  These four Makefiles can also be used to define base
compiler settings for the corresponding instruction set architecture (ISA):

	Makefile.i386		- rules for building 32-bit x86 objects
	Makefile.amd64		- rules for building 64-bit x86 objects

The Makefile.common file adds common compiler and linker flags to these base
definitions, and defines the rules for building the example modules.  You will
not need to change any of the definitions here in order to build the examples.
If you wish to construct additional modules of your own, edit the MODULES macro
at the top of Makefile.common.  For example, if you create a new module source
file common/mymodule.c, you should change:

<	MODULES = example1.so example2.so

to:

>	MODULES = example1.so example2.so mymodule.so

and then execute "make".

3. Targets

The Makefile in this directory supports the following targets:

	make all (default)	- build all modules for the current machine
	make clean		- remove object files from build directories
	make clobber		- remove objects, and modules

To build the example modules, execute "make" in this directory.  This will
execute the default "make all" target.

4. Loading Modules

After you successfully compile the example modules, the module object files
reside in one or more of the i386/, amd64/ subdirectories
depending on the ISAs supported on your machine.  In order to load the example
modules, you can either use the ::load built-in dcmd with the absolute pathname
of a given module, or you can adjust the module library path to include the
directory where your modules are located.  This can be done using the ::set -L
built-in dcmd.  For example:

	> ::set -L %o:/usr/demo/mdb/%i
	> ::load example1

The %o token expands to the old value of the path.  The %i token expands to
the appropriate ISA name.  You can restore this setting each time you use
MDB by adding the ::set directive to your $HOME/.mdbrc file.  This file, if
present, is processed automatically each time you start the debugger.

5. Example 1: Echo and Vmstat

The first example module provides the source code for two example loadable
dcmds.  ::simple_echo is a command to echo back its arguments, similar to
/usr/bin/echo or MDB's built-in ::echo dcmd.  ::vminfo is a command to read
and print the kernel's global virtual memory statistics structure.  This
example introduces the basic structure of an MDB module and demonstrates some
simple argument processing.  In order to use ::vminfo, you will need to apply
MDB to a crash dump of your system, or to the live kernel.  To apply MDB to a
crash dump, you might execute:

	$ mdb unix.0 vmcore.0

To apply MDB to the live kernel, become super-user and then execute:

	# mdb -k

6. Example 2: Proc Walker and PS

The second example module provides a more realistic example of something you
might want to do with MDB: print a formatted table of active processes,
similar to the /usr/bin/ps command or MDB's ::ps dcmd.  This example
introduces the concept of a walker, a set of functions which describe how to
iterate over a data structure, and them demonstrates how the ::simple_ps
dcmd can be built using this walker.  Using the simple_proc walker, you can
obtain a listing of kernel proc_t addresses:

	> ::load example2
	> ::walk simple_proc
	71690a80
	7168ee40
	71611898
	[ ... ]
	7103b178
	7103b888
	1041ce20

Using the ::simple_ps dcmd you can obtain a formatted listing of processes:

	> ::simple_ps
	PID COMM
	285 sh
	271 mibiisa
	269 ttymon
	[ ... ]

7. Packaging and Installation

If you are a software developer, you may wish to develop and deliver MDB
modules along with your software products in order to facilitate analysis
of software problems at customer sites.  Your completed MDB modules should
be packaged along with your software and delivered into the appropriate
MDB module directory.  For kernel debugging modules, your module should
be delivered in one of the following directories:

	/usr/lib/mdb/kvm
	/usr/platform/`uname -i`/lib/mdb/kvm

and should be named after your kernel module.  For example, the "ip" kernel
module has a debugging module named "ip.so".