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symmon(1M)							    symmon(1M)

NAME    [Toc]    [Back]

     symmon - kernel symbolic debugger

DESCRIPTION    [Toc]    [Back]

     symmon is a standalone program used to debug the kernel.  It is intended
     to	be used	only by	those involved in writing and debugging	device drivers
     or	other parts of the kernel.  The	implementation of symmon is machine
     dependent and the commands	and functionality described here may not apply
     to	all systems.

     To	use symmon, several steps must be taken	to prepare the system:

     1.	 symmon	must be	manually installed by the user,	because	it is not
	 installed on the system as shipped from the factory.  This can	be
	 done by installing the	``Debugging Kernels'' subsystem	in the IDO
	 software development option.

     2.	 Alterations must be done to the file /var/sysgen/system/irix.sm to
	 build a kernel	capable	of being debugged; see the comments in that
	 file for details.

     3.	 The program setsym(1M)	needs to be run	on the newly generated kernel
	 to allow symmon to recognize symbols in it.

     4.	 symmon	needs to be installed in the volume header of the root drive
	 with dvhtool(1M).  This normally happens as part of the software
	 installation process.

     symmon is typically used with a terminal as the system console (see
     prom(1M) for information on how to	enable a terminal as the console).
     When a debug kernel is booted, it automatically tries to load symmon from
     the same source.  symmon can be booted from an alternate device by
     setting the dbgname environment variable in the prom.  For	example:

	  setenv dbgname scsi(1)disk(1)rdisk(0)partition(8)symmon

     loads symmon from a disk 1, connected to SCSI controller 1.

     Once symmon is loaded, the	system operates	normally until symmon is
     triggered by the keyboard or an exceptional condition happens in the
     kernel that causes	it to enter the	debugger automatically.	 To enter
     symmon from the keyboard, type a <Ctrl-a>.	 symmon	prompts	with DBG: and
     accepts commands described	below.

   Built-in Commands    [Toc]    [Back]
     symmon has	a set of basic commands	for setting and	clearing breakpoints
     and examining system state.  Not all of the commands listed below are
     supported on all systems.	Some commands take memory addresses as
     arguments.	 Addresses can be given	directly in decimal, in	hex if
     preceded by 0x, in	binary if preceded with	0b, as names of	functions or
     data, as names of registers if preceded by	$, or as a combination of
     those with	+ and -.  Some commands	take a range of	addresses specified as

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symmon(1M)							    symmon(1M)

     either ADDR:ADDR for an inclusive range or	ADDR#COUNT for a count of
     COUNT starting at ADDR.  Commands are listed below:

     brk [ADDR]
	  Set a	breakpoint at the given	address.  If no	arguments are given,
	  the set of current breakpoints is listed.

     bt	[MAX_FRM]
	  Print	a stack	back trace of up to MAX_FRM frames.  See the
	  discussion about ubt below for an alternate form of stack back

     c	  Continue execution from a breakpoint.

     cacheflush	[RANGE]
	  Flush	both the instruction and data caches over the range of address

     call ADDR [ARGLIST]
	  Set up a stack frame and call	the procedure at the specified

	  Clear	the screen.

     dis [RANGE]
	  Disassemble instructions in memory over the range specified.

     dump [-b|-h|-w|-d]	[-o|-t|-x|-c] RANGE
	  Dump the contents of memory.	The -b,	-h, -w and -d flags can	be
	  used to specify byte,	halfword, word or double word data.  The -o,
	  -t, -x, and -c flags can be used to specify octal, decimal,
	  hexadecimal, or ASCII	data formats.

	  The specified	range of memory	to dump	can take these forms:

	  o  base for a	single location

	  o  base#count	for count locations starting at	base

	  o  base:limit	for locations whose addresses are greater than or
	     equal to base but less than limit

     g [-b|-h|-w] [ADDR|$regname]
	  Get and display the contents of memory at the	address	given.	If a
	  register name	is given, its contents are displayed at	the time the
	  kernel was stopped.

     goto ADDR
	  Continue execution until the given address or	a breakpoint is
	  reached.  This is a short hand way to	set a breakpoint at an

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symmon(1M)							    symmon(1M)

	  address, continue, and then remove that breakpoint.

     help List a short summary of the built-in commands.

     hx	NAME
	  The symbol table is searched for entries matching NAME, and if one
	  is found, its	value is printed.

     kp	[KPNAME]
	  Kernel print command.	 If no arguments are given, a list of the
	  available kernel print commands is given.  If	a name is given, that
	  print	function is executed.  See the discussion on kernel print
	  commands below for more information.

     lkaddr ADDR
	  The given address is matched against the symbol table	and the
	  symbols near it are listed.

     lkup STRING
	  The given string is matched against the symbol table and any symbol
	  with an equal	or longer name is printed.  This is convenient when
	  you cannot remember the precise symbol name.

     msyms ID
	  Print	dynamically loaded kernel module's symbols.  The module	id is
	  found	using either the lboot -V command or the ml list command.  See
	  the mload(4) manual page for more information.

     nm	ADDR
	  The address given is matched against the symbol table	and if an
	  exact	match is found,	the symbolic name is printed.  This is a more
	  restrictive version of the lkaddr command described above.

     p [-b|-h|-w] ADDR VALUE
	  Put the value	given into the address given.  This causes a write to

	  List the contents of the general purpose registers when the kernel
	  was stopped.

     quit Restart the PROM.

     s [COUNT]
	  Single step the kernel for either one	instruction or the given
	  count.  If the current instruction is	a branch, then both it and the
	  following instruction	are executed.  The next	unexecuted instruction
	  is disassembled when the command completes.  After a step command is
	  issued, symmon enters	a command repeat mode where a null command
	  causes another step to be taken.  This repeat	mode is	indicated by a
	  change to the	prompt.

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symmon(1M)							    symmon(1M)

     S [COUNT]
	  Same as the step command above, except that jump-and-link
	  instructions are stepped over.

     tlbdump [RANGE]
	  List the contents of the translation lookaside buffer.  If
	  specified, the range of TLB entries given is listed.	The range
	  should specify a subset of the 64 TLB	slots.

     tlbflush [RANGE]
	  Flush	the TLB	over the range of entries given	or the entire TLB if
	  no range is specified.

     tlbmap [-i	INDEX] [-n|-d|-g|-v] VADDR PADDR
	  Inserts an entry in the TLB that maps	the virtual address given by
	  VADDR	to the physical	address	given by PADDR.	 If specified, the TLB
	  slot given by	INDEX is used.	The -n,	-d, -g,	and -v flags can be
	  used to turn on the non-cached, dirty, global, and valid bits.  The
	  current TLB context number is	used.

     tlbpid [PID]
	  Get or set the current TLB context number.  If no argument is	given,
	  the current TLB context number is returned; otherwise, the context
	  number is set	to the argument.

     tlbptov PADDR
	  Display TLB entries that map a virtual address to the	physical
	  address given.

     tlbvtop VADDR [PID]
	  Find the physical address mapped to the virtual address given	by
	  VADDR.  If PID is given, then	it is used as the TLB context number
	  in the match;	otherwise, the current TLB context number is used.

     unbrk [BPNUM]
	  Remove the breakpoint	with the breakpoint number given.  The
	  breakpoint number can	by determined by listing the set breakpoints
	  with the brk command.

     wpt [r|w|rw] [0|PADDR]
	  Set a	read, write or read/write watch	point at on physical address
	  using	the R4000 watch	point registers.  The address must be double
	  word aligned,	and the	watch point trips on any access	within the
	  next eight bytes.  An	argument of 0 clears the watch point.  Note
	  that the R4000 only supports one watch point at a time.

	  Dump the contents of memory at the given address.  This command
	  functions in a similar manner	as the dbx(1) command of the same
	  syntax.  The XX is a symmon specific extension to printing
	  hexadecimal double words.

									Page 4

symmon(1M)							    symmon(1M)

   Kernel Print	Commands
     The kernel	extends	the set	of built-in symmon commands with kernel	print
     commands.	These commands dump various kernel data	structures.

     proc PROCINDEX
	  Dump the process structure associated	with the given process table
	  index.  Note that the	process	table index is not the same as the
	  IRIX process ID.

     user PROCINDEX
	  Dump the contents of the user	structure for the process with the
	  process table	index given.

     buf BUFNUM
	  Dump the contents of a buffer	structure.  The	address	of the buffer
	  to be	dumped is controlled by	the BUFNUM argument.  If BUFNUM	is a
	  valid	K0, K1,	or K2 address, then the	buffer at that address is
	  displayed.  If BUFNUM	is a small integer, it is used as an index
	  into the buffer table.  If BUFNUM is equal to	-1, summary
	  information about the	buffer pool is displayed.

     qbuf DEVICE
	  Dump the contents of buffers queued for the device given.  The
	  device argument is given as the major/minor device number of the
	  desired device.

     pda [CPUID]
	  Dump the contents of the processor private data area for the
	  processor ID given.

     runq Dump the run queue.  A short summary of each process waiting for CPU
	  time is listed.

     eframe [ADDR]
	  The exception	frame at the given address is displayed.  If the
	  address is a small integer, the exception frame of the process with
	  that process table index is used.  The exception frame holds the
	  contents of the general purpose registers at the time	the process
	  last executed.

     ubt [PROCINDEX]
	  User process stack back trace.  A stack back trace is	listed for the
	  process whose	process	table index is given.

	  Process table	list.  This gives an output similar to ps(1) and can
	  be used to find the process table index number for a process.

     pb	  Dump console print buffer.  The contents of the console print	buffer
	  are printed.	This can be useful when	an important message has
	  scrolled off the screen.

									Page 5

symmon(1M)							    symmon(1M)

SEE ALSO    [Toc]    [Back]


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