c_when

MIPS处理器的bootloader,龙芯就是用的修改过的PMON2

The when Command
when

The when command sets complex breakpoints 

Format

The format for the when command is: 

when condition action
 

where: 

condition  Specifies the conditions under which the 
		     breakpoint will occur.

	action     Specifies the action to be taken when the 
		     breakpoint occurs.

Functional Description

The when command provides a very flexible way to set breakpoints and to specify the action that
should be taken when they are encountered.

Each when command takes two arguments, a condition, and an
action.  The condition can be something as simple as @pc==main (when
the program counter is equal to value of the symbol main), or it can be
a complex expression that might include specifying the contents of
memory locations.

Actions can be any Monitor command string.
But it can also include the pseudo command stop. For example, the
command, "when @pc==main stop" specifies that when the
program counter has the value of the symbol main, execution should
stop. 

Conditional expressions can be combined in any arbitrary
manner to provide extremely complex breakpoint conditions. For
example,

	PMON when @pc==main2&(^tcbchn==task1||^tcbchn==task2) stop

which will stop execution when the pc is equal to main2, and
either tcbchn is equal to task1 or task2. 

In the preceeding examples we have chosen to stop execution when
the condition is met. However, it is possible to specify a list
of commands. For example,

	PMON when @pc==sort "r;d -w dat3 1"

	specifes that when the pc is equal to 'sort', the commands
	'r' and 'd -w dat3 1' will be executed. The ';' is used to
	separate commands, and the double quotes are necessary because
	the argument contains spaces.  

The Monitor is responsible for deciding when
to use hardware breakpoint registers (if present). In general, the Monitor uses software breakpoints unless there
is a specific reason that a hardware breakpoint is required.

If you issue a command that requires a hardware breakpoint register.
But that the Monitor finds that there is not
one available. The Monitor will automatically
use trace mode when you issue the c command to continue execution.
Because trace mode is not real-time, the Monitor will warn you at the time that you set
the breakpoint that this will require non real-time execution.

Examples