c_b

MIPS处理器的bootloader,龙芯就是用的修改过的PMON2

The b Command
b

The b command sets and displays breakpoints.

Format

The format for the b command is:

b
b adr..
b adr -s str

where:

adr	specifies an address for the breakpoint. 
				Up to 32 breakpoints addresses can be set.

-s str	executes the command string when the breakpoint is hit.

Invoking the b command with no options causes the Monitor to print a list 
of the current breakpoints. 

Functional Description

The b command sets a breakpoint at the specified 
address or addresses. Multiple addresses may be specified. Specified 
addresses must be word-aligned. 

This command is effectively a "pass-thru" to the 
when command. Issuing the command, 
"b main" is equivalent to issuing the command, 
"when @pc==main stop". However, unlike the 
when command, the b command can
take multiple addresses.

The Monitor automatically assigns a number to each breakpoint. 
The Monitor allocates the lowest 
available breakpoint number from 0 to 31 to any new breakpoint. 

The Monitor reports a new breakpoint's number immediately after the 
breakpoint is set (see the examples at the end of this subsection for 
illustration of this). The assigned numbers can be used in the 
db (Delete Breakpoint) command.

The brkcmd Variable 

When a breakpoint is reached, the command list specified in the 
environment variable brkcmd is executed. The default setting for brkcmd is:

brkcmd = "l @pc 1"

This command "l @pc 1", specifies that when the breakpoint
occurs, the Monitor will disassemble one line starting at the address
of the program counter.

You can change the breakpoint command variable with the set command. 
For example, you can include additional monitor commands in the brkcmd 
variable. You must separate additional commands on the command line 
with a semicolon. For example, entering the following command lists one 
line after reaching a breakpoint, and then displays all the register values.

set brkcmd "l @epc 1;r *"

By default, breakpoints are cleared when the load command is executed. 
See the section on the load command later in this document for details on 
how to override automatic breakpoint clearing after a download operation.

Some examples illustrating the use of the b command follow.

PMON b a002000c	Set a breakpoint at 0xa002000c.

Bpt 1 = a002000c

PMON b			

Bpt 0 = 8002022c

Bpt 1 = a002000c
Display all breakpoints.

PMON b 80021248 -s "r"	Set a breakpoint at 0x80021248. Display registers
			when the breakpoint is encountered.

See Also 
db,
when, 
and load commands.