cyggdb

MIPS处理器的bootloader,龙芯就是用的修改过的PMON2

		GNU's gdb from Cygnus Support
		GNU's gdb from Cygnus Support

To use the debug Monitor with GNU's gdb,
connect the serial port that gdb will use, to the Monitor's tty0 (the
console) on the target board.  i.e., gdb only uses one serial port.

set command to set your
Monitor's prompt to "PMON ".  Gdb is
hardwired to expect that string, and will not work with any other value
(note the space after the "").
--

Compile and link your modules with the -g option.  This will generate
the extra information that is required by gdb. For example,

	pmcc -g -o bubble bubble.c

Invoke gdb.

	% mips-lsi-elf-gdb -b 9600 bubble

where 'bubble' is the name of the object file that you are debugging.
The option "-b 9600" specifies that 9600 baud will be used for the
Host-to-Target communications.

By default gdb from Cygnus Support runs in a windowed mode. However, it
the time of writing, the windowed mode was incomplete/buggy, so you might
prefer to run it in non-windowed mode. To select non-windowed mode, add
the option -nw to the command line.

	% mips-lsi-elf-gdb -nw -b 9600 bubble

gdb normally expects your monitor to have a prompt of "PMON " (note
the space). If your monitor uses a different type of prompt you can
either change it in the Monitor using the set
command or tell gdb what prompt to expect.  For example,

	(gdb) set monitor-prompt IMON 

Note that this command does not expect quotes around the prompt,
but gdb will take the entire string including trailing spaces. So be careful
to type the string exactly.

Next you must specify the target type, and serial port
that will be used to communicated with the target. For example,

	(gdb) target lsi /dev/ttyb

this specifies that the target is running LSI Logic's PMON (or IMON),
and that the target is connected to /dev/ttyb on the host. If you are
using MSDOS you will need to specify one of
the COM ports. eg. com1.

To download your program to the Target issue the "load" command. No
arguments are necessary as gdb has all the other information it needs.

	(gdb) load

If you simply want to run your program, you can just type "run". But if
as is more likely you want to be able to set breakpoints and single-step
your program, you should type,

	(gdb) b main
	(gdb) run

this will set a breakpoint at "main" and execute the program until it
reaches that point.

The following table is a summary of the most frequently used commands:

Brief Command Summary
gdbPMON/IMON equivalentDescription
steptSingle Step
nexttoStep Over
b addrb addrSet Breakpoint
deletedb *Delete
ccContinue
rungStart Execution

When debugging the Host-to-Target communications it is sometimes useful
to create of log of all the transactions. The following command writes
a log to the file "remote.log".

	(gdb) set remotelogfile remote.log